The Radio Frequency Systems Bulletin

3rd quarter 2004

S h a re d a n d s c u l p t e d : L A b ro a d c a s t i n g i n t h e l i m e l i g h t Connections, corrugations and costs Alberta SuperNet—broadband for the future Minimizing microwave antenna interference

The Clear Choice™

Expansion vs QoS: striking the balance

4 What’s New BDA/duplexer series supports in-building 3G Broadband Optimizers complete 90-degree range Ultra-compact manifold combiner Dual function DAB Band III filter family

Microwave antenna options for minimizing interference

18 In Touch 3G focus for Chinese expo RFS shines the DTT light in Hungary IBC 2004: RFS to display digital solutions Kerrang! rocks with FM solution PREVIEW: Base station technology—an RF interface evolution

6 Cover Story Shared and sculpted: LA broadcasting in the limelight

WorldWideWeb: http://www.rfsworld.com Publisher: Jörg Springer Executive Editor/Editor Asia Pacific: Peter Walters Editor EMAI: Regine Suling Editor Americas: Ann Polanski Managing Editor: Dr Ellen Gregory Production Editor: Christian Michatsch Art Director: Marilu Krallmann

Authors: Allan Alderson, Dr Ellen Gregory, Anita Talberg Photos: RFS archives, Alcatel Canada, CMS Wireless, inform archives, Getty Technical illustrations: Pamela Seaman Cover images: RFS archives Cover art: Marilu Krallmann Print: Print Design, Minden

8 Feeder Systems

Layout and Graphics: inform Advertising, Hannover

Connections, corrugations and costs—the feeder cable debate

IMPRINT

Radio Frequency Systems

14 Technology Focus

3 Editorial

Editorial Services: Relate Technical Communications, Melbourne

11 Microwave

Trademarks: CELLFLEX®, BDA®, FLEXWELL®, MicroTenna™, Optimizer®, RADIAFLEX®, Radio Frequency Systems®, RFS®, RFS CompactLine®, SlimLine® and The Clear Choice™ are trademarks, service marks or registered trademarks of Radio Frequency Systems.

Alberta SuperNet—broadband for the future

On the cover: Dual RFS broadband panel arrays provide sculpted digital/analogue signals for four Los Angeles television broadcasters at Mount Wilson in California.

INDEX

8

BDA/duplexer series supports in-building 3G A new series of bi-directional amplifiers (BDA) and duplexers offers a convenient and inexpensive means of overlaying UMTS on existing 2G in-building RF distribution systems.

Connections, corrugations and costs— the feeder cable debate To make sense of base station feeder cable technology, start where it all begins and ends: at the base station site with the site crews and network development teams.

14 11 Alberta SuperNet—broadband for the future From Alberta’s Rocky Mountains to its northern ice lakes, RFS microwave antenna solutions play an important role in realizing province-wide broadband connectivity.

6 Shared and sculpted: LA broadcasting in the limelight An innovative, shared broadcast system atop Mount Wilson provides four LA broadcasters with high performance—and highly sculpted —digital and analogue television coverage.

Microwave antenna options for minimizing interference With microwave network density on the rise, the potential for signal interference is also increasing. RFS looks at ways of minimizing interference-causing distortion of radio frequency signals.

RF interference—one of the greatest challenges of network optimization and a by a remote antenna tilt system, the RF

A

recent

report

by

global

wireless

It is a well-known industry maxim that it

control afforded by the Optimizer range will

some

costs four times as much to attract a new

ensure operators can offer premium QoS

interesting points about the threat of

customer than to retain an existing one.

both now and in the future.

subscriber churn for mobile operators.

With this very real cost of churn in mind, it

But many factors come into play—in

Based on a survey of UK mobile phone

makes business sense for mobile operators

particular, a focus on total system solutions.

users, the report states that operators risk

to maintain a tight focus on customer

Carefully

losing a full third of their customers due to

satisfaction. If, as LogicaCMG points out,

performance at a component level, the

poor quality of service. It even goes so far

many mobile operators are focusing on

RFS range of high-performance cellular

as to put a figure on what this might

business expansion at the expense of

antennas, low-attenuation transmission

cost the UK telecoms industry in 2004—an

improving quality of service, they are clearly

line and RF conditioning components also

estimated _3 billion.

shooting themselves in the feet.

combine to provide fully integrated base

And the rate of subscriber churn in the

This choice between network expansion

station solutions that meet the most

telecommunications

consultancy,

LogicaCMG,

raises

industry

engineered

for

optimum

remains

and enhancing network performance is not

stringent demands of operators. Ongoing

significant. In May this year, the global

a new dilemma. Network optimization is an

QoS objectives are achieved through

average across fixed and mobile sectors

ongoing challenge for operators the world

precise RF control and tuning flexibility;

was estimated by communications research

while the broadband functionality and

group, Chorleywood, to be at 22 per cent.

built-in future-proofing streamline the path

Dr Klaus-Dieter Mischerikow Radio Frequency Systems President

EDITORIAL to network expansion and migration to

operators is what might happen to their

4

has been carefully engineered to combat

primary key to ensuring QoS. Complemented

Yet of perhaps greater concern to mobile

Normalised radiation [dB]

2

Expansion vs QoS: striking the balance

new technologies. In other words, RFS

bottom line if LogicaCMG’s predictions

over--a constant balancing act between

offers both expansion capability and quality

come to pass and the rate of churn increases.

coverage, capacity and quality of service

of service in the one solution set.

TNS Asia Telecoms Index has also revealed

(QoS). To-date, these have often been

The dilemma is unlikely to go away; the

that, compared with a year ago, 33 per

regarded as mutually exclusive; one to be

choice between network expansion and

cent more Asian mobile users are indicating

prioritized at the expense of the others. But

enhancing network performance has been

they’d like to change networks within the

this doesn’t have to be the case.

the ‘lot’ of wireless operators since the

next six months.

Radio Frequency Systems has developed a

inception of mobile services. In fact,

What is causing this rising dissatisfaction

comprehensive suite of RF products that

operators will face even more of a juggling

with mobile services? The attraction of

allow operators to consider more than one

act

more competitive pricing has long been a

goal at a time. This suite permits operators

technologies such as push-to-talk, WiFi and

factor, but new issues related to the service

to achieve both immediate and long-term

mobile video.

itself are coming to the fore. Surveys have

expansion objectives, plus fulfil immediate

RFS is committed to these next-generation

cited problems with coverage, reception,

and long-term goals for improvements in

technologies. Our focus is on providing

customer service, billing and roaming as

QoS—not to mention a generous dose of

optimal RF solutions in order for them to be

strong

future-proofing.

realized. Both network expansion and

customers to seek alternative providers. If

Our Optimizer range of high-performance

quality of service are important and, with

the service is not up to scratch, then the

cellular base station antennas is an ideal

the right technology, the choice of how to

fight over how much to pay for it becomes

case-in-point. Featuring a host of advanced

act can be made easier. It’s all about striking

somewhat moot.

features such as reduced side lobes and an

the right balance.

and

legitimate

reasons

for

as

they

deploy

next-generation

extended tilt range, the Optimizer series

Klaus-Dieter Mischerikow

3

B DA / d u p l e x e r s e r i e s supports in-building 3G

Ultra-compact manifold combiner and uplink, and are provided in two output

requirements can be realized ‘locally’ via the

power ratings, 18 dBm and 9 dBm. Used in

unit’s power port, or ‘remotely’ via the RF

The latest addition to the leading UHF

features double temperature compensation,

combination with the new duplexer, the

coaxial feeds, permitting the units to be

combiner range of Radio Frequency Systems

and exhibits low losses for its given filter

bi-directional amplifiers may be used to

cascaded in a wide range of combinations.

is an ultra-compact manifold combiner

sizes. According to Broad, a key differentiator

A new series of bi-directional amplifiers

I-DUX2G/3G combination is one of the

support a ‘3G on 2G’ overlay on an existing

The I-DUX2G/3G-1 duplexer is uniquely

ideal for low-power digital television (DTV)

is the availability of coaxial filters of up to

(BDA) and duplexers from Radio Frequency

first on the market to offer a cost-effective

broadband in-building system.

broadband, with its 2G port supporting

broadcast sites. Designed for combining

7-poles, offering semi-adjacent channel

Systems offers a convenient and inexpensive

and

Both I-BDA2100 models support the full

frequencies between 800 and 1880 MHz.

digital channels up to 250 W, the UHF

combining and transmitter DTV masking.

means of overlaying universal mobile

this situation.”

UMTS band, and provide automatic gain

It provides particularly low insertion loss at

manifold combiner offers an economical

Although the manifold configuration can

telecommunication services (UMTS) on

The series comprises two band-specific

control in accordance with the Third

both the 2G and 3G ports, and comes

and space-efficient alternative to balanced

only combine channels down to semi-adjacent

existing second-generation (2G) in-building

UMTS bi-directional amplifiers (I-BDA2100-1

Generation Partnership Project’s (3GPP)

complete with two separate on-board

modules.

spacings, it can be used with balanced

RF distribution systems.

and I-BDA2100-2), plus a broadband

specified UMTS requirements. Manual gain

dc power input ports, allowing even

“The manifold combiner has been developed

modules in a hybrid system to realize adjacent

“RFS has had the foresight to build in

duplexer (I-DUX2G/3G-1). The new BDAs

control is also provided for final system

greater

in direct response to requests from broad-

channel combining. “Essentially, the semi-

future-proofing in its 2G in-building RF

supply 35 dB nominal gain in RF downlink

levelling. The unit’s 10-30Vdc power

configuration.

simple

means

of

overcoming

flexibility

in

system

power

casters for an ultra-compact solution,”

coverage solutions—as a result, these are

The new series of bi-directional amplifiers (BDA) and duplexers from RFS is used for overlaying UMTS on existing 2G in-building RF distribution systems.

sufficiently broadband to support the simple overlay of new third-generation (3G) UMTS services,” said Peter Raabe, RFS Global Product Manager for Wireless

4

exiting

Broadcast, Graham Broad.

system can be fed into

“It’s a fully integrated unit,

system, and adjacent

used within

levels may prove inadequate, due to the

our balanced

higher insertion losses of the 2G network

combiner

cabling. The new RFS I-BDA2100 and

modules. For

I-DUX2G/3G-1

B ro a d b a n d O p t i m i z e rs c o m p l e t e 9 0 - d e g re e ra n g e

the wideband input

than half the components

IBDA2100-2

manifold

of a balanced combiner

many cases though, the UMTS RF power

WHAT ’S N EW

the

and contains less

Distributed Communications Systems. “In

IBDA2100-1

adjacent combined channels

said RFS Area Product Manager

channels inserted,” said Broad.

“This

means

that

multiple adjacent channels can be combined using half-balanced and half-manifold units, resulting in a highly

instance, the manifold

compact and low-cost system.”

configuration has just one

Designed for wall mounting or installation

50E filter instead of two, and the whole unit

within a standard 19-inch rack, the manifold

is therefore less than half the weight, has

combiner units alone can be used to combine

half the footprint, and is lower in cost.”

up to six semi-adjacent channels, with a

Displaying similar performance characteristics

combined maximum output power of 750 W.

to RFS’s low-power integrated balanced

This equates to 6 x 125 W or 3 x 250 W of

‘cellular’

combiner, the manifold model is also

potential input powers into the combiner,

850 MHz, trunking/specialized mobile radio

tuneable over the entire UHF band (470 to

providing superior flexibility for broadcasters

(SMR) 800 MHz, and global system for

860 MHz) for 6, 7 or 8 MHz bandwidths,

operating low power sites.

the

APX86-90914L

supports

mobile communications (GSM) 900 MHz 90-degree

“The 90-degree aperture cellular antenna is

circle. RFS now offers complete antenna

services. The APXV18-20914/15 antennas

beamwidth cellular antennas have joined

proving to be a vital complement to

solutions in both 65- and 90-degree

support

Radio Frequency Systems’ high-performance

conventional

beamwidths, ensuring network planners

communication services (PCS) 1900 MHz

Optimizer family. The new additions—the

antennas,” said Patrick Nobileau, RFS Vice

greater network optimization flexibility.”

and universal mobile telecommunications

In support of global digital audio broadcasting (DAB) deployments, Radio Frequency Systems

variable electrical tilt APXV18-20914 and

President Base Station Antenna Systems.

Importantly,

system (UMTS) 2100 MHz services. As

is launching a new family of DAB Band III coaxial filters. Tuneable over the entire VHF Band III,

APXV18-20915,

tilt

“In some cases, 65-degree proves the best

broadband, with the APXV18-20914 and

operators

the new filters offer a compact and flexible solution for both transmitter mask filtering and

APX86-909014L—complete the Optimizer

choice, as it results in a minimal bit error

APXV18-20915 supporting frequencies in

roll-out multiple and often co-located

digital RF channel combining.

90-degree aperture series, making it one of

rate. In other cases, a 90-degree aperture is

the 1710 to 2170 MHz band, while the

wireless platforms, the broadband nature

The DAB filter range is founded on RFS’s world-leading RF combining technology and utilizes

the most comprehensive of its kind

optimal, as in a tri-sector configuration it

APX86-90914L accommodates frequencies

of the optimizer 90-degree antennas

a similar platform of components to the company’s VHF Band III digital television combiners.

available today.

provides coverage that is closer to a perfect

in the 806 to 960 MHz band. As a result,

provides them with a powerful means

Six and eight-pole versions of the coaxial filters will be available in three cavity sizes

of rationalizing and reducing antenna

(100 mm, 180 mm and 270 mm), accommodating transmitter powers of 500 W, 1500 W

inventories.

and 2500 W respectively. The nominal bandwidth is 1.54 MHz, as specified by the global

Three

new

broadband

and

the

fixed

65-degree

aperture

all

three

antennas

RFS 90-degree beamwidth Optimizer antennas

are

GSM

1800

and

MHz,

OEMs

personal

worldwide

Dual function DAB Band III filter family

All three antennas exhibit the superior

‘Eureka 147’ DAB standard.

Type

Model No.

Bandwidth

Tilt

Length

Gain

performance

common

The eight-pole DAB filters can be incorporated within transmitters to provide critical mask

Low band fixed tilt

APX86-90914L-T0 and T6

824 - 940 MHz

Fixed 0 and 6 degrees

2 metres

15.5 dBi

to all members of the RFS Optimizer

filtering of the digital RF signal, in keeping with global DAB standards. When used as the key

Low band variable tilt

APXV86-90914

824 - 940 MHz

Variable 0 -10 degrees

2 metres

15 dBi

antenna family. This includes side lobe

components of a balanced DAB combiner, the eight-pole filters can achieve both critical

High band fixed tilt

APX18-209014 -T2 and T5

1710 - 2170 MHz

Fixed 2 and 5 degrees

1.3 metres

15.8 dBi

suppression typically better than 20 dB

transmitter masking and adjacent channel combining simultaneously, eliminating the need

High band fixed tilt

APX18-209015 -T2 and T5

1710 - 2170 MHz

Fixed 2 and 5 degrees

1.8 metres

17.5 dBi

across the entire frequency and tilt range,

for additional filters within the transmitter.

High band variable tilt

APXV18-20914

1710 - 2170 MHz

Variable 0 -10 degrees

1.3 metres

16.5 dBi

significantly increased gain, and superior

Exhibiting low losses for these cavity sizes, the RFS DAB Band III filters are of compact design,

High band variable tilt

APXV18-20915

1710 - 2170 MHz

Variable 0 -10 degrees

1.8 metres

17.5 dBi

front-to-back ratio.

with the 100-mm models able to be installed within a standard 19-inch rack.

characteristics

5

S h a re d a n d s c u l p t e d : L A b ro a d c a s t i n g i n t h e l i m e l i g h t An innovative, shared broadcast system atop Mount Wilson provides four LA broadcasters with high performance—and highly sculpted—digital and analogue television coverage.

Crucial combining

which were tuned to optimize system

was introduced at the top of the 20-level

A crucial component of the system is the

performance. In addition, a total of eight

panel antenna column. This comprises

pair of parallel RFS directional waveguide

5-inch

coaxial

stainless steel tanks filled with a specifically

combiner chains, which support the dual

transmission lines were installed to feed the

calculated volume of ethylene glycol, which

broadband arrays. The channel combiner

panel array—four for each sub-array.

moves against the modes of vibration,

sub-systems each comprise five directional

The

waveguide filters and one blank section to

transmission line system was reflected

characteristic from around 0.0025 to 0.05

allow for the introduction of additional

power so low across all channels that

(that is, reducing the magnitude of

channels. The total system is also designed

several

oscillations by a factor of 20).

RFS

net

HELIFLEX

flexible

performance

transmitters’

result

reflected

of

the

power

potentially

increasing

the

damping

The advent of digital television and simulcast

combining. Dual sub-systems

to accommodate future channel reallocation,

indicators did not even move when the

digital/analogue services has undeniably

also allow greater flexibility for

and its compact nature means that space is

transmitters were energized.

changed the face of global broadcasting.

main/standby services, as well as

available in the building for two additional

With mountain real estate often at a

accommodating the different

combiner systems, if required for future

Structural challenges

more than four years, the final RFS combiner/

premium, plus escalating potential for

pattern tailoring requirements

expansion.

Owing to both the congested nature and

antenna system at Mount Wilson has the

interference and the considerable cost of

of the stations.

In order to accommodate the high

potential seismic activity of the Mount

capacity to accommodate a total of 12 digital or analogue services from channel 32 to 56.

deploying new infrastructure, many broad-

Team effort Conceived and designed over a period of

transmitted powers of analogue services

Wilson site, installation of the combiner

casters have made the bold move toward

Sculpting the signal

on channels 50 and 56, a new ‘full-

system proved an interesting challenge. A

multi-service systems.

Accurate sculpting of the broad-

wavelength’ directional waveguide combiner

newly constructed combiner room was

For four Los Angeles broadcasters (KDOC,

cast signal was one of the

was developed. This incorporates resonators

built as a bridge suspended over an existing

KJLA, KOCE, and KXLA) seeking to add

primary performance require-

a full wavelength in height (instead of half

building; and the entire combiner and

DTV to existing analogue services, these

ments of the system. A number

wavelength), providing twice as much

separate digital mask filter systems were

considerations ultimately have led to

of

surface area to dissipate the greater heat

bolted onto several steel frameworks, also

the deployment of a shared broadcast

restrictions

or

generated by losses in the high-power,

suspended from groups of four vertical

facility atop the city’s premier site—Mount

toward San Diego to the south-

higher-frequency channels. This means that

steel members. Seismic horizontal ties,

channels required signal over

Mexico

east, and it was desirable to reduce wasted power over the

6

COVER STORY

ocean for all channels, while ensuring

premium

coverage

The panel arrays were installed in four sections in October 2003.

Dual broadband panel arrays from RFS provide sculpted digital/analogue signals for four Los Angeles broadcasters at Mount Wilson.

7

for all of Los Angeles and its western satellite cities. The only Wilson.

Envisaged,

co-designed

and

way of achieving this level of

connecting the steel frameworks to the

overseen by broadcast consultant, S. Merrill

pattern sculpting, without compromising

signal phasing on the pattern is tightly

building structure itself, prevent the frame-

Weiss, the solution incorporates a dual,

performance, was through use of broadband

integrated—such that a change of phasing

works from excessive swinging during

broadband panel antenna/combiner system

panel arrays.

on one face has cascaded effects on other

seismic activity.

The combiner chains were installed in the

designed and manufactured by Radio

The dual, 10-level broadband panel arrays

antenna parameters. Finally, due to the

This was not the only structural innovation.

first half of 2003, followed by the raising

Frequency Systems.

deployed at Mount Wilson were designed

broadband nature of the antenna (580 to

The internal cavity of the antenna column

of the two stacked panel arrays in October

As an experienced provider of broadband

by RFS in close collaboration with Merrill

756 MHz), any adjustments for one

needed to be expanded in order maintain

of the same year, and rigid line optimization

RF solutions, RFS joined the project when it

Weiss. Early in the project, it was decided

frequency lead to follow-on effects across

human access, as well as contain a large

in early 2004. Currently configured for

became clear that a shared system was

to use panels arrayed on three faces of a

the bandwidth, so that the design is

volume of equipment—including the eight

nine channels (including two standby

required. Not only is the Mount Wilson site

five-sided column, with panels omitted on

effectively four dimensional.

flexible feeders and the branch feeders and

services), the first services went on-air in

highly congested, but since adjacent

the two northern faces, since coverage was

The process of ensuring optimum coverage

power dividers used for pattern sculpting.

April 2004, with the others joining in the

channels were involved, each of these

not required over the nearby mountains to

for each of the services—and particularly,

forced air cooling is not required to ensure

The result was an asymmetrical cross-

following months.

services needed to be broadcast from the

the north. Using sophisticated computer

that the signal restrictions over Mexico

that the operating combiner will not exceed

section, which led to issues with the

The project as a whole was undeniably

same location to prevent interference. In

modelling

of

didn’t degrade the performance of those

the design temperature rise.

antenna/tower interface. This was solved

a team effort—not only between the

order to move the analogue services from

electrically tilting the three faces individually,

channels not requiring it—involved many

Complementing the combiner system is a

in collaboration with the tower designer

consultant, Merrill Weiss, and RFS, but

elsewhere to Mount Wilson, plus deploy

coupled with power distribution and

iterations of the key design variables.

network of rigid transmission lines linking

through

development

also between the tower and transmitter

the new digital services, a shared system

phasing adjustments, were assessed to

Interference issues and the challenge of

the transmitters, mask filters, combiners,

of a unique multi-dimensional antenna

designers, installation and construction

was

determine

imperative.

It

also

offered

the

techniques,

the

effects

The panel arrays are supported by a pair of parallel RFS directional waveguide combiner chains—including a new ‘full-wavelength’ directional waveguide combiner.

the

fast-track

achieving the required gain within specified

and flexible coaxial feeders, which are each

clamping mechanism.

crews, the site owner, and the four

advantage of economy of scale.

each antenna.

power limitations were also taken into

in different locations owing to the crowded

An additional design consideration was the

broadcasters themselves. After extensive

For the seven channels to be broadcast

This antenna pattern optimization process

account, with the ultimate result being

nature of the site. Care was taken during

minimization of tower harmonics due to

theoretical design and modelling, the

(32, 44, 48, 49, 50, 51, and 56), dual

involves numerous variables. The act of

two separate stacked panel arrays (each

the design phase to minimize the reflections

wind-induced

physical

antenna/combiner

sub-systems

the

optimum

pattern

for

vibrations.

To

provide

realization

of

the

individual

were

changing the beam-tilt on individual faces

capable of handling up to 195 kW total

that might otherwise have occurred due to

dynamic

antenna

components, and the ultimate installation

conceived for a number of reasons. The first

leads to ‘transition regions’ in the pattern

average power input) that meet the

the number of components in the rigid feed

structure—which comprises the two RFS

and commissioning, the RF broadcast

of these was to simplify the combiner system,

that require careful analysis during the

stringent performance requirements of all

system; this involved the development of

panel arrays plus a third antenna mounted

system met all performance objectives

removing the need for adjacent channel

design

four broadcasters.

high-performance, broadband ‘elbows’,

on top of these—a tuned, liquid damper

right from the start.

process.

Also,

the

effect

of

stability

to

the

C o n n e c t i o n s, c o r r u g a t i o n s a n d costs—the feeder cable debate Making sense of the base station feeder cable technology debate is no easy task.The best place to start is where it all begins and ends: at the base station site with the site crews and network development teams.

8

For these reasons, the appearance of

“We put a lot of thought into this with the

smooth-wall feeder cable on the base

development of CELLFLEX ‘A’,” explains

station scene is something of a curiosity.

Chris Adams. “We knew crush strength was

“To-date, rigid smooth-wall feeder cable

vital in the field, so we didn’t compromise

hasn’t been seen much in European base

the CELLFLEX crush resistance, while

station applications, but it’s common all

dropping attenuation up to six per cent.”

over the world in its ‘native’ application— that of cable television (CATV) signal

Make the connection

routing,” says RFS’s Adams. “Here, it’s

Dressing or ‘connectorizing’ the cable—

The ubiquitous coaxial feeder cable provides

end-to-end wireless project development

buried deep beneath the ground—where

finishing the cable so it is fitted with a

the RF link on cellular base stations from

services, from site acquisition and base

the thermal conditions are comparatively

universal 7/16-inch DIN connector—is the

Moscow to Minneapolis. Bought by the

station design, through to installation,

stable—and routed in long straight runs

second area where Wilson sees problems.

metre, its ‘buy and install’ cost is negligible

commissioning and maintenance.

with few bends, so it thrives.”

These, he believes, are often caused by

on the total base station price scale. In

And it is at the maintenance end that

In the vastly different environs of the cellular

cable manufacturers. “There are some

many quarters, the feeder system is regarded

Wilson sees feeder costs really blow-out.

base station, things are quite different.

brands out there that have three different

merely as a network ‘consumable’. Some

“We often get called out to repair faults on

“When we get called out on a site repair

types of connectors and connector tools, to

believe that ‘a cable, is a cable, is a cable’.

non-CMS Wireless sites. The majority of the

where rigid smooth-wall cable has been

do three different cable models, all by the

“Wrong,” say the experts—the network

feeder cable problems we see here are as a

used, we always check for the kinks first,”

same manufacturer!” Wilson says. He

operators and planners, and the site

result of poor connectorization, problems

installation and maintenance crews. If

at bends, and cuts and crush faults in the

poorly selected and managed, the potential

cable run,” says Wilson. These manifest in

total life-cycle costs of a transmission line

poor signal strength, or intermodulation

system can be very high indeed.

problems.

RFS uses a slotted brass finger claw on the RAPIDFIT connector to maximize the contact with the outer—this provides around twice the electrical contact, and better long-term performance.

firmly believes this is a recipe for disaster— It’s about striking a balance, and remem-

and he’s witnessed the results. “We’ve

bering that the feeder systems are ultimate-

actually just repaired a site where the

ly destined to be installed by real installers

installer made the wrong connector fit

on real base station sites, not in labs!”

the cable. There was no signal strength

FEEDE R SYSTEMS

9

”We attach great importance to the

According to Wilson, it’s a frustrating and

reliability and quality of feeder cables, as

costly business for the operator. “The end-

they directly influence both the quality of

user is putting out maintenance money to

the services we provide our subscribers, and

repair what should’ve been done right in

the ongoing expansion costs of the system

the first place,” he says. The cost isn’t limited

corrugated cable, and rigid smooth-wall cable

Bend and crush

says Wilson. “We also check the ground

at all—it was completely open!” The

as a whole. It is for this reason we search

to that of raw maintenance; there are also

—plus a dizzying range of accompanying

Accommodating cable bends—sometimes

kits and connectors—cutting into the outer

well-known cable brand name matched

out a specific grade and quality of cable,“

the costs of base station down-time, and

connector systems and tools. There is also

up to six bends in a single run on a modern

conductor seems to be a common problem

that of the connector, but the models didn’t

says Valery Ulianov, Director of Regional

resultant subscriber churn.

wide diversity in installation crews’ skill levels

urban site—is an area where problems can

with smooth-wall installs. If it’s cut, then

match up.

Network

Technical

Wilson cites the limited nature of the feeder

and experience, plus a broad range of site

occur. Most problematic is the rigid

thermal

expansion

Worse yet, the wide variety of tools can be

Director of Moscow region with leading

system commissioning/testing regime as a

layouts, weather conditions and so on. This

smooth-wall feeder cable. Without the

eventually make an opening for water

expensive, bulky and difficult to use. As

Russian

something of a problem. The common

mix makes achieving repeatable long-term

corrugations of conventional cable, it

to get in.”

Wilson explains, it can be an uphill battle

Ulianov is involved in the operator’s massive

voltage

feeder performance a challenge.

exhibits minimum bend radii of up to two

Some ‘high-performance’ (reduced attenu-

ensuring you have just the right tool for

network expansion program that will see

‘sweep’ test simply doesn’t truly measure

“We were well aware of this real-world,

and a half times that of corrugated cable,

ation) cables can also pose site problems. In

each job.

Vimpelcom’s popular ‘BeeLine GSM’ service

the long-term quality of the install. “You

multi-variable situation when we developed

and bending moments as much as six times

the quest to minimize attenuation, some

RFS’s Adams agrees that cross-range and

further expanded in the so-called macro-

can tighten a connector down and make

our

high-performance

greater. “From an installer’s point of view,

manufacturers have used dielectric foams

backward compatibility of connectors, plus

regions of Russia.

the sweep pass today, but over time and

corrugated feeder cable,” says Chris

this is the hardest cable to install,” says

with densities so low that crush resistance is

simplicity of tooling is an essential in

temperature cycles a poor install will

Adams,

of

Wilson. “It’s hard to bend, and if you

severely compromised. “They’re looking at

getting it right at site. Equally important

Mounting costs

deteriorate,” he says. “You’ll start seeing

Transmission Lines with Radio Frequency

re-bend, it tends to kink. If you bend it

gaining a quarter of a dB, but losing crush

though, is ensuring the RF and electrical

Fast forward from base station planning

reflective power over time.”

Systems. “All too often, feeder cable

once and need to bend it back, it

strength in a big way,” Wilson says. “When

robustness of the connector design itself.

and roll-out, to where the feeder system

The challenge facing both operators and

technology groups focus too hard on

generally snaps.”

you take the cable out and put a hoisting

There are three basic designs for connectors

costs really mount up: during long-term

installation crews is dealing with the

achieving performance in one or two key

The ‘kinks’ that ultimately occur in rigid

grip on it, it puts indentations in the

—two of which rely on clamping down on

maintenance and repair. Aaron Wilson is

number of variables in the transmission line

areas—say

or

smooth-wall cable represent a great deal

cable 'cause it's so thin.” This, he says,

the outer of the cable, which is ultimately

Technical Maintenance Manager with CMS

‘equation’. These include a wide selection

connector VSWR. The end result is they

more than visual blights—they are weak

becomes an even greater problem on

problematic.

Wireless, an Arkansas USA-based wireless

of feeder technologies—such as corrugated

have something that might perform well in

points that crack or deteriorate over time,

collocation sites, where obstructions and

“Smooth-wall cable is an entirely glued

base station developer. His company provides

cable, low-attenuation ‘high-performance’

the laboratory, but is a disaster in the field.

and ultimately reduce signal strength.

bends are many.

assembly—inner conductor to dielectric to

Development cellular

and

operator,

Vimpelcom.

standing

wave

ratio

(VSWR)

CELLFLEX Global

‘A’

Product

attenuation,

Manager

flexibility,

contraction

and

Alberta SuperNet— b ro a d b a n d f o r t h e f u t u re

outer conductor to jacket. This means you can’t flare the outer to electrically clamp it from both sides, as you do with corrugated cable connectors,” Adams says. As a result,

The wireless component of the project is divided again into two elements, the ‘transport’ or backbone links, and the

From Alberta’s Rocky Mountains to its northern ice lakes, RFS microwave antenna solutions play an important role in realizing province-wide broadband connectivity.

the cable outer is clamped from the outside only, using a ‘slip ring’. “Over time, the outer starts to collapse under the slip ring and gives way. Installers tell us that you can

‘access’ links. The transport links provide high-capacity point-to-point microwave connectivity (20

to

over

120

longer

kilometres),

distances at

data

leave an installation nice and tight, then

In some parts of the world, rolling out

Ingenious concept

throughputs of either 45 or 155 Mbps. The

return to find the connector can almost

community-wide

network

SuperNet is ingenious in its concept and

access links are shorter microwave hops

spin on the cable. This leads to inconsistent

infrastructure is far from straightforward.

design. The network is made up of two

(10 to 40 kilometres), providing connectivity

behaviour, dropped calls, intermodulation

Alberta, Canada’s fourth largest province, is

elements—a ‘base area’ and an ‘extended

between the transport network and remote

and so on.”

a case-in-point. Half its three million people

area’ network. The base area network is

facilities.

The other basic design that applies pressure

live in just two cities, Edmonton and

optical fibre-based, and provides gigabit

The Canadian arm of global communications

Calgary. The balance is thinly distributed

connectivity to 27 larger communities. The

solutions provider, Alcatel, was appointed

across far-flung rural and semi-rural centres.

extended area network is made up of a mix

by Bell in the second half of 2003 to provide

The province is roughly the same size as

of optical fibre and microwave wireless

the RF equipment radios (antennas and

to the cable outer conductor, is one used with some corrugated cable connectors.

Aaron Wilson, Technical Maintenance Manager with Arkansas USA-based wireless base station developer, CMS Wireless.

While the outer is flared and clamped in the

broadband

conventional manner, a ring of ball-bearings

Leader with the German installation group

just what is installed at site and how. “Stick

France, and its terrain varies wildly from

technologies,

SuperNet’s

associated equipment) that make up the

within the connector head is used to

Hestra-Antennenmontage. “If the connectors

with what works,” advises CMS Wireless’s

mountains, to rolling hills and plains,

connectivity to 395 smaller communities

2,000-kilometre/60-hop transport network.

achieve extra electrical connection on the

are correctly installed and sealed, you have

Wilson. “To me, that’s corrugated cable.

through to marshy peat lands. As a result,

across the province. For many of these

Alcatel, in turn, selected Radio Frequency

ridge of one corrugation. “This design is

no problems. We have base stations that

My suggestion is to find a cable with just

providing cost-efficient broadband access

smaller locations, access to high-speed

Systems to provide all the necessary

flawed, as the bearing ring only grabs a

are almost a decade old, and none have

one type of connector and stick with it.

to

internet

microwave antennas, waveguide, and

small portion of the available conductor.

experienced water problems.”

Make sure you keep the crush strength up

challenging, to say the least.

most

of

Alberta’s

population

is

and

services

extends

is

an

entirely

new

experience.

associated installation hardware.

there, as well.” While feeder cable might be purchased as a

10

FEEDER SYSTEMS

MICROWAVE

site-consumable, its potential long-term cost implications are in the ‘major capital item’ league. Ulianov’s experience with Vimpelcom suggests this is very much the

Instead, RFS uses a slotted brass finger claw

Adams concurs with this view. “The glued

case, and is the core reason Vimpelcom

Hops in time

on the RAPIDFIT connector to maximize the

assembly of the rigid smooth-wall cable

opts for CELLFLEX ‘A’. ”The vastness of

The 60 microwave hops are located across

contact with the outer,” Adams says. “It

stops water moving from within its connector

Russia, coupled with the fast-paced and

the province within 44 wireless ‘service areas’

gives us around twice the electrical contact,

to the cable. But water in the connector in

all-embracing

services

(see map on page 13). Each hop is powered

and better long-term performance.”

a cellular installation is enough to totally

expansion program, forces us to work

by Alcatel’s MDR-8000 low to high-capacity

nature

of

our

disrupt transmission!,” he says. “Our view

under diverse economic and climatic

microwave digital radios. These are coupled

The water myth

is that the only place water belongs is outside

conditions,” Ulianov concludes. ”At the

with RFS’s high-performance single-polarized

Water ingress in the cable is another area of

the transmission line. Where it gets in is

same time, we insist on providing unique

DA series microwave antennas, using RFS’s

debate. The rigid smooth-wall camp claims

either via a cut in the cable outer, or via a

quality standards in all the services we offer.

low-loss FLEXWELL elliptical waveguide to

its cable’s glued construction prevents water

poor quality connector. Keeping water out

For this reason we take the choice of the right

form each radio-to-antenna link.

ingress, whereas flexible corrugated cable is

of the connector comes down to two

cable systems very seriously”. The bottom

“The reason we selected the RFS DA series

susceptible. Nonsense, say the users. “I

factors—simplicity of connectorizing and

line, it would seem, is that subscribers the

antennas was to ensure we got the best RF

have been using corrugated cable here in

quality three-point sealing, rather than

world over justifiably expect operators to

performance,” says Alcatel Canada’s Senior

North Germany for many years now, and

simple ‘crest-seal’ O-rings.”

get it right the first time. There are no

Account Director, Terry Pettigrew. The RFS

have never experienced water ingress

Minimizing feeder system total life-cycle

‘second

DA series, he says, provides premium

problems,” says Stefan Kraege, Project

costs, it would seem, starts and finishes with

needs to be chosen accordingly.

chances’—feeder

technology

front-to-back

performance,

and

the

In early 2001, the Government of Alberta

The complete network is being built by

precision radiation pattern envelope (RPE),

took

It

leading next-generation communications

sharp beamwidth and reduced side lobe

conceptualized a province-wide broadband

this

challenge

head-on.

company, Bell, and independently managed

radiation demanded by the Canadian

network—the Alberta SuperNet. Its core

by Axia SuperNet, a subsidiary of the

spectrum authority, Industry Canada.

goal was to ensure affordable high-speed

broadband networks project group Axia

A further, and equally important, reason

network connectivity to schools, libraries,

Netmedia. This ensures cost-controlled

was RFS’s ability to deliver a proven product

businesses and homes in 422 communities

access for all service providers, plus a

in accordance with a demanding delivery

across Alberta.

healthy and competitive ISP market from

schedule. “The timeline was certainly one

which subscribers can choose.

of the biggest challenges,” says RFS Area

11

use ‘quad diversity’—a combination of

scale before—for example, State-wide

both space and frequency diversity—on the

deployments in Florida and Philadelphia—

single hop.

the time lines were more spread out.”

“We use either space or frequency diversity

The first deliveries of RFS antenna systems

in other hops, but this is the only link on this

and Alcatel radios to Bell were in October

project where we’ve actually combined

2003, with the entire program completed

them together,” says Alcatel’s Director

by the end of the second quarter of 2004.

Wireless Communications Division, Marc

The antennas and radios are progressively

Vandeberg. To achieve the space diversity,

being delivered and installed at the

Vandeberg explains, the link uses a massive

120 sites by the project’s installation

pair of 15-foot diameter RFS DA antennas,

contractors, Radian and West Tower.

plus a pair of 12-foot diameter antennas,

Time was tight on this project due in part to

each mounted with around 60 metres of

Alberta’s unique seasonal and geographic

vertical separation. While the balance of

conditions. An example is the marshy peat

the SuperNet transport hops operate in

lands in the north-east of the province—

the 8-GHz band, the Fort Chipewyn-to-

sites in this area are only accessible by road

Birch Mountain link uses channels in the

during the winter months, via ice roads cut

lower 6-GHz band, to reduce the hop

through the snow. After the spring thaw,

attenuation. Two pairs of non-adjacent

the only option for moving equipment into

channels, separated by 177.9 MHz, are

these sites is via helicopter—a prohibitively

used to achieve the link’s frequency

costly option.

diversity.

Lake Athabasca

Fort Chipewyn Wood Buffalo National Park

British Columbia

service level agreement, Alcatel opted to

had completed microwave projects of this

Birch Mountain

J

Bitumount Fort Mackay

Edmonton

S IN TA UN O M

Banff National Park

Long-distance link

Trials and success

One particular ice road-accessed hop also

Jointly designed by Alcatel, the project’s

The balance of

proved to be the project’s most technically

lead contractor, Morrison & Hershfield, and

the 60 transport

demanding—the hop linking the remote

design group Planetworks, the link was

hops are expected

centres of Fort Chipewyn and Birch

simulated and trialled in early April 2004 at

to

Mountain, in the province’s far north-east.

Alcatel’s two US facilities (Longview and

commissioned before the end

Located in the project’s wireless service area

Plano). The radios were connected to long

of September 2004, marking a

‘J’, the 120-kilometre microwave hop runs

lengths of microwave waveguide to model

significant milestone in the development of

over boggy marsh lands and alongside the

the space diversity in the 120-kilometre

SuperNet. “Once we got things rolling and a

vast Wood Buffalo National Park, home to

hop. Fixed and variable paths were used

process established, it all went incredibly

2,200 rare wood buffalo. “We had to get

to simulate fading activity, plus test

smoothly,” says Pettigrew. “Of all Bell’s

the antennas and radios in no later than the

equipment to simulate dispersive fade

suppliers, I know they are very pleased with

second week of March,” recalls Pettigrew.

characteristics.

RFS and Alcatel and the work we have done.”

“I think we had one of the last trucks on the

Once the link was proven in the factory, the

The responsiveness of the RFS/Alcatel team,

ice road to get in and out of there!”

Alcatel radios were air-freighted from

coupled with the tried and proven nature of

is

Edmonton, Alberta, to the remote Fort

the RFS DA series microwave antenna and

understood to be one of the longest

Chipewyn and Birch Mountain sites, where

the Alcatel MDR-8000 radio, have played

‘Optical Carrier Level 3’ (OC3) microwave

they joined the already-installed 15-foot

links in the world—presented a great

and 12-foot diameter RFS DA antennas.

challenge to the link’s designers. This was

be

installed

Calgary

an Saskatchew

MICROWAVE

Legend Wireless service area Wireless service area J National park area 0

100 km

13

200 km

and

A m i c ro w a v e solution for Alberta

standards such as ETSI, FCC, Industry

an important part in the success and

The RFS DA antenna series is a high-

provides superior flexibility and installation

efficiency of the transport network rollout.

performance solid-body antenna family,

efficiency,

On the first weekend in July 2004, the Bell

“There was no experimentation, beta-version

providing reduced side lobe suppression for

conventional, rigid rectangular waveguide.

exacerbated by the ponds and marshes

installation

crews

radio software or unproven RF systems,”

more exacting applications. Available in 4,

Available in a wide selection of frequency

scattered along the link, which represented

finally proved the design was correct—one

says Zoberi. “What we offered in the DA

6, 8, 10, 12 and 15-foot diameters, the

bands from 2 to 40 GHz, FLEXWELL

reflection and multipath sources. As the

of the world’s longest OC3 microwave

antenna was world class, proven technology

DA single-polarized antenna series features

provides both low loss and low VSWR

Government of Alberta specifies ‘five

links was up and running, and ‘Fort Chip’

—nothing less. It was the optimal choice

RPE that meets applicable international

performance.

nines’ reliability (99.999 per cent) in its

was on the air!

for the SuperNet.”

The

The 15-foot and 12-foot diameter RFS DA antennas mounted with around 60 metres of vertical separation at Fort Chipewyn.

Lake Mamawi

Alberta

Y CK RO

12

Product Manager, Asad Zoberi. “While we

long

hop

distance—the

link

and

commissioning

Canada and so on. The antennas also feature low VSWR performance and high front-to-back ratios, and are designed for the harshest of environments, with a survival wind speed of 200 km/h. RFS FLEXWELL elliptical waveguide when

compared

with

M i c ro w a v e a n t e n n a o p t i o n s f o r m i n i m i z i n g i n t e r f e re n c e With microwave network density on the rise, the potential for signal interference is also increasing. Dr Daniel Wojtkowiak, Vice President of Microwave Antenna Systems RFS, looks at ways of minimizing interference-causing distortion of radio frequency signals.

the antenna gain also reduced. Greater

Figure 2 is valid for the ‘ideal’ case, where

dependent on the wavelength (and hence

radio power would then be required to

wave fronts hit the wall perpendicularly.

frequency) to be used in the application.

achieve the desired radiation power, resulting

Now consider the situation for signals

Assuming a dielectric constant between 2.5

in a corresponding increase of side lobe

not having this ideal orientation. Given

Optimizing the radome

and 3, typical solid radome thicknesses for

radiations. This illustrates the fact that

the longer effective wave path through

Radomes are used for two main applications

different frequencies would be: 6 mm (14 GHz),

correct radome design is critical not only

the radome material as they hit the

in radio link antenna design. The first is to

4 mm (22 GHz), and 2.4 mm (38 GHz).

for optimizing link budget, but also for

wall obliquely, the optimum thickness

cover the antenna feed system in order to

It is important to note that if a radome of

interference control, since an increase in

is now also dependent on the angle of

protect it from the dirt, snow and ice of our

incorrect thickness is used, the transmitted

side lobe radiations would raise the potential

incidence (θ), measured as the deviation

power will be reduced, and consequently

for interference.

from the normal.

Over the past decade microwave links

potential for these to interact with one

natural environment. In addition, a radome

have proven a popular solution for the

another and cause interference. Since any

significantly reduces the windload of an

In practice, however, angles of incidence of

telecommunications industry. The relative

distortion of the signal reduces the quality

antenna system, by preventing the dish and

up to 20 degrees have negligible effect on

ease and economy of installation has seen

of service, controlling interference is now

shield from ‘catching’ wind. However, both

the optimum radome thickness. This is

them deployed in an increasing number

the mandate of any radio network operator

radome material selection and thickness need

of point-to-point and point-to-multipoint

and national authority. A good starting

to be carefully considered to optimize the

applications—from communications back-

point for consideration is the design and

power transmitted through the radome,

bones, to branch links and distribution

location of the source of the signal—the

while at the same time ensuring the side

networks, not to mention applications in

microwave antenna (Figure 1).

lobes are not increased to detrimental effect.

the broadcast industry and private enterprise.

Figure 1 shows the main beam at 0 degrees,

Figure 2 shows a plot of the reflection

With the rise of new cellular operators

plus side lobes that are significant to

characteristics at a plane wall radome for

and new technologies, overall microwave

about ±90 degrees from the main beam.

different materials. Each of these materials

network density is undeniably escalating.

It is these side lobes that can cause

are characterized by a relative dielectric

TECHNOLOGY FOCUS

Amplitude reflection coefficient [R] Amplitude reflection coefficient [R]

illustrated for flexible radome materials in Figure 3, which shows the relationship between angle of incidence (θ) and d/λο (where λο is the free space wavelength), for achieving 95 per cent power transmission through materials with different dielectric constants. For values of θ up to 20 degrees, the optimum thickness is barely impacted—particularly for low loss materials,

15

Yet this intensification of microwave

interference with adjacent point-to-point

constant of εr = 2; however each material

which should be those considered for

communications brings added challenge.

links, and it is these side lobes that must be

has a different loss parameter, tan δ, where

radome design purposes.

The greater the number of point-to-point

minimized through careful antenna design

tan δ ranges from 0.0018 (low loss) to

links in a given area, the greater the

and installation.

18 (high loss). Figure 2 shows that for low

A similar relationship holds for solid Figure 2—Reflection characteristics at a plane wall radome

minimum values of the reflection coefficient,

microwave antenna designers. A small

transmission of incident power. These correspond to design values where the ratio of radome wall thickness (d) to microwave wavelength in the sheet (λ) is close to either zero or 0.5. The first case of d/λ ≈ 0 is practically realized as d