Where the Competitive Receiver Starts -The First Mixer Bob DePierre August, 2009

Out-of-Passband Signals Cause In-Passband Interference -Once it gets through the mixer, no filter can get rid of it. -Third-order distortion usually dominates. -Some mixers handle overload better than others.

f1

f2

2*f1-f2 2*f2-f1

Mixer = Distortion Device • 1960’s breakthrough was the balanced mixer. • SBM => RF balanced out. • DBM => LO also balanced out. • Exponential behavior really bad for giant signals.

i = I S (e

v VT

− 1) 2

3

x x e = 1 + x + + + ... 2! 3! x

1 id

16.0m

1

Plot1 id in amperes

12.0m

8.00m

4.00m

0 160m

200m

240m vd in volts

280m

320m

Why the FET Mixer? Diode Ring DBM - Exponential 2 mag(fft(temp)) RF

6

5

R4 .001

4

L2 1u

L4 L6

8

X4 BAT720

L1 1u

V1

L4 L5

X1 BAT720

IF

3

L1 L3

10

L5 1u

RIF 50

RLO 50 L4 1u

7

V9

9

L6 1u

2

L1 L2

LO

1

X2 BAT720

X3 BAT720

L3 1u

L5 L6

VLO

L2 L3

Plot1_f mag(fft(temp)) in volts

100u

RRF 50

10u 1u 100n 10n 1n

2 3.00Meg

9.00Meg

15.0Meg frequency in hertz

21.0Meg

27.0Meg

Orion 4 JFET DBM – Square Law 18

RF

V1

11

L2 1u

L1 1u

14

C3 72p

J4 J310

R8 680 R9 5k

L3 1u

L1 L3

C6 330p

R11 5k

RIF 200

R12 5k

J2 J310 R3 47

C4 0.001u

C7 0.1u

6 10

R6 680

L11 1u J1 J310

C5 0.001u 13

L2 L3

IF

L10 1u

7

R10 5k

15

L1 L2

1m

L10 L11

16 2

IR13

12

C2 0.001u

RRF 50 1

2 mag(fft(temp))

R13 .01

J3 J310

R5 680

R7 680

17

L7 1u R4 50

LO

L9 1u

10u 2 1u

LO

L9 L7

9

100n

8

L7 L8

100u

L8 1u

3

4

V2 13

5

Plot1_f mag(fft(temp)) in volts

C1 0.001u

L9 L8

2.00Meg

6.00Meg

10.0Meg frequency in hertz

14.0Meg

18.0Meg

Receiver Architectures • Superheterodyne Bandpass Filters

First Mixer

Narrow Filters

Gain

Detector

Local Oscilllator

• Direct Conversion Bandpass Filters

First Mixer

Lowpass Filter

Audio Gain

Output Device

Audio Gain

Output Device

Mixer Test Procedures • •

Input Signals = -25dBm, Spacing 20 kHz, 2 kHz “Invasive” Measurement at Output Port of First Mixer Receiver Under Test

Marconi 2018A SignalGenerators

Hybrid Combiner Hi-Z FETProbe

HP 8657A

Agilent 8595E SpectrumAnalyzer

GPIB to PC

Intercept Graph Used to Calculate the IP E

Power Out(dBm)

C

D

B

A Power In(dBm)

F

Mixer Structures • BJT Gilbert Cell • Diode DBM • 2 JFET SBM • 4 JFET DBM • Fast Switching Multiplexer

BJT Gilbert Cell

• • • •

SA612 chip in wide use Double Balanced, but with no transformers Elecraft KX-1 Q-Track receivers

BJT Gilbert Cell in KX-1 Wide Spacing • Gain= +18.7 dB • Distortion= 46.1dB down • IP= -1.9 dBm

Diode DBM Mixer • MiniCircuits TUF-1 in Elecraft K2 • Workhorse high performance mixer of the 80’s—90’s • Transformers balance the RF and LO signals out of the IF port

Diode DBM Mixer in K2 ATTN off; 3 kHz Spacing • 14dB Preamp On • Gain= +11.2dB • Distortion 46dB down • IP= +4.85dBm • Phase noise very close in only

2 JFET SBM in Pegasus • Balanced only at RF port • Standard J310 FETs

2 JFET SBM in Pegasus ATTN off, 20 kHz Spacing • Gain= -9.5dB • Distortion 56.2dB down • IP= +3.3dBm • Noise at graph edge –100dBm

2 JFET SBM in Pegasus ATTN on, 20 kHz Spacing • • • •

Gain= -17.6dB Distortion 62dB down IP= +6dBm Noise at graph edge –95dBm

2 JFET SBM in Pegasus ATTN off, 2 kHz Spacing • Gain= -11.7dB • Distortion 47dB down • IP= -1.5dBm • Noise at graph edge –98dBm

2 JFET SBM in Pegasus ATTN Switched, 2 kHz Spacing • ATTN on/off

4 JFET DBM in TS850 • Discrete components • All 3 ports have balancing transformers

4JFET DBM in TS850 Preamp On, 20 kHz Spacing • Gain= +1.4dB • Distortion 47dB down • IP= -1.5dBm • Noise at graph edge –110dBm

4 JFET DBM in TS850 Preamp Off, 20 kHz Spacing • Gain= -6.6dB • Distortion >71.8dB down • IP= +13.55dBm • Noise at graph edge –105dBm

4 JFET DBM in TS850 Preamp On, 2 kHz Spacing • Gain= +4.7dB • Distortion 34dB down • IP= -8.0dBm • Noise at graph edge –85dBm

4 JFET DBM in TS850 Preamp Off, 2 kHz Spacing • Gain= -10.5dB • Distortion 61.4dB down • IP= +5.7dBm • Noise at graph edge –95dBm

4 JFET DBM in TS850 Preamp Off, 2 kHz Spacing • Gain= -7.9dB • Distortion 60.3dB down • IP=+5.1dBm • Noise at graph edge –100dBm

4 JFET DBM in FT950 • JFETs and transformers in modules • All 3 ports have balancing transformers

4 JFET DBM in FT950 Preamps Off, 20 kHz Spacing • Gain=-3.3dB • Distortion >80dB down • IP>+14.8dBm • Noise at graph edge –110dBm

4 JFET DBM in FT950 Preamps On, 20 kHz Spacing • Gain= +16.3dB • Distortion 46.7dB down • IP= -1.7dBm

4 JFET DBM in FT950 Preamp #1 On, 20 kHz Spacing • Gain= +8.1dB • Distortion 64.9dB down • IP= +7.4dBm • Noise at graph edge –100dBm

4 JFET DBM in FT950 Preamps Off, 2 kHz Spacing • Gain= -2 dB • Distortion >60.8dB down • Noise at graph edge –92dBm

4 JFET DBM in IC756Pro • Components inside well shielded enclosures • Measured outside enclosure at Q501

4 JFET DBM in IC756Pro Preamp #2 On, 20 kHz Spacing • • • • •

Input= -25dBm Gain= -23.4dB Dist 46.3dB down IP= -1.85dBm Noise at graph edge –113dBm

4 JFET DBM in IC756Pro Preamp #1 On, 20 kHz Spacing • • • • •

Input= -20dBm Gain= -31.3dB Dist 55.2dB down IP= +6.3dBm Noise at graph edge –115dBm

4 JFET DBM in IC756Pro Preamps Off, 20 kHz Spacing • • • • •

Input= -10dBm Gain= -42.5dB Dist 48dB down IP= +14.0dBm Noise at graph edge –115dBm

4 JFET DBM in IC756Pro Preamps Off, 2 kHz Spacing • Input= -15dBm • Gain= -40dB • Phase Noise Covers the Distortion • IP= +13.7dBm • Noise at graph edge –115dBm

4 JFET DBM in IC756 Preamp #1 On, 2 kHz Spacing • • • • •

Input= -15dBm Gain= -30dB Dist 42 dB down IP= +6.0dBm Noise at graph edge –108dBm

4JFET DBM in Orion • Discrete components • Balancing transformers at 2 ports

4 JFET DBM in Orion Preamp Off, 20 kHz Spacing • • • • •

Input= -15dBm Gain= +11.2dB Dist 55dB down IP= +12.6dBm Noise at graph edge –120dBm

4 JFET DBM in Orion Preamp On, 20 kHz Spacing • • • • •

Input= -25dBm Gain= +22.7dB Dist 47.2dB down IP= -1.38dBm Noise at graph edge –115dBm

4 JFET DBM in Orion Preamp Off, 20 kHz Spacing • • • • • •

ATTN= 6dB Input= -15dBm Gain= +5.6dB Dist 67.3dB down IP= +18.7dBm Noise at graph edge –95dBm

4 JFET DBM in Orion Preamp Off, 2 kHz Spacing • • • • • •

ATTN= 6dB Input= -10dBm Gain= +4.8dB Dist 55dB down IP= +17.6dBm Noise at graph edge –73dBm

4 JFET DBM in Orion Preamp On, 2 kHz Spacing • Input= -35dBm • Gain= +24.1dB • Phase Noise covers the Distortion • IP= -1.2dBm • Noise at graph edge –79dBm

2 JFET SBM in Orion Sub 20 kHz Spacing • • • •

Input = -25dBm Gain= 2.2dB Dist= 66.2dB down IP= +8.1dBm

2 JFET SBM in Orion Sub 2 kHz Spacing • Input= -25 dBm • Gain= +6.4dB • Phase Noise covers the Distortion • IP= +4.4dBm • Noise at graph edge –83dBm

Mux Mixers – K3 • Double Balanced With transformers at 2 ports • CBT3257 chip, 21¢

Mux Mixers – Softrock & Flex • Tayloe Mixer – Sampling Integrator – Direct Conversion Receiver Only

• FST3253 chip, 17¢ • Requires I/Q Inputs 1 i

2 q

Plot1 i in volts

4.50 3.50

1

2.50 1.50 500m

Plot2 q in volts

4.50 3.50

2

2.50 1.50 500m 1.00u

3.00u

5.00u time in seconds

7.00u

9.00u

Mixer vs Rig Rundown Mixer Type

Rig

IP Range

BJT Gilbert Cell

Elecraft KX-1

< 0 dBm

Diode Double Balanced Elecraft K-2

0 to +5dBm

2 JFET Single Balanced TenTec Pegasus, Jupiter, Orion Sub, IC-746

0 to +5 dBm

4 JFET Double Balanced

FT950, TS850, IC756, Orion Main

+10 to +15 dBm

Fast Switching Multiplexer

K-3, Flex, Softrock

The “Ultra” Rigs 20 kHz Spacing Orion +12.0 dBm (+18.6 dBm with 6dB ATTN) TS850 +13.55 dBm IC756 Pro +14.0 dBm FT950 +14.8 dBm 2 kHz Spacing IC756 Pro +13.7 dBm Orion +17.6 dBm (with 6dB ATTN)

And the Conclusion is:

The 4 JFET DBM has become so good that it doesn’t pay to improve it until we improve phase noise at its output!