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!