H-Mode mixer - Switches - FSAV332

Fairchild FSAV332

The FSAV332 (QSOP-16 package) contains 4 SPST switches with a separate control line each. All 4 switches are needed to implement the H-Mode mixer. The PCB layout of the FSAV332 with the 3 TT4-1A transformers is less compact than the layout of the SPDT type mixers. Especially the connection between the outer transformers is considerably longer. The FSAV332 requires an 74AC74 divide by two squarer as it does need both Q and !Q.

The following table summarizes the measurements with the FSAV332 and the TT4-1A transformers:

FSAV332 + TT4-1A + 74AC74 Vdd = 7.0V, Vbias = 3.5 Best bias
Band BPF mixer MDS -dBm IF rej spur mixer IIP3 (dBm) @ 20KHz spacing Bias IIP3
IL CL - + avg -6 -3 0 +3 +5 0
-dB -dB BPF BPF -dB dB dBm dBm dBm dBm dBm V dBm
160 3,3 5,12 133 129 57,6 41,4 3,5 41,4
80 1,4 5,04 133 131 57,6 43,7 44,7 46,2 48,2 49,7 3,5 46,2
40 2,3 5,00 133 130 57,2 46,2 3,5 46,2
30 3,4 5,04 133 129 57,2 43,0 3,5 43,0
20 3,4 5,04 133 129 55,2 41,4 3,5 41,4
17 3,0 5,00 133 129 52,0 41,1 3,5 41,1
15 3,9 4,96 133 127 51,6 3,6 40,4 3,5 40,4
12 3,7 4,96 133 129 51,6 38,1 3,5 38,1
10 2,3 4,96 133 126 57,2 37,0 3,5 37,0
6 5,40 123 27,6 35,2 3,5 35,2

The FSAV332 is tested at 7V Vdd with bias at the mid point. There is no other point were the IMD dipped better. There is no steep dip. FSAV332 is rather insensitive with respect to the bias point.

I am not able to measure at -6dBm reliably as the 3rd IMD products are too close to the noise floor.

Again degrading IP3 with frequency and peaking IP3 on 80M and 40M.

160M performance seems to suffer from the transformers limitations.

The spur reduction on 15M is fairly good at 3,6 dB above MDS average per spur.

Unlike the mixers with the SPDT type switches, the 9MHz IF rejection is very good at below -50dB fairly constant on all HF bands!

MDS on 6M and RF-IF isolation are very poor indeed. High spur levels were observed on 6M.

The FSAV332 is also tested with the ADTT1-1 1:1 transformer in order to verify the good results with these transformers obtained with the FSA3157 switches. The following table shows the results:

FSAV332 + ADTT1-1 + 74AC74 Vdd = 7.0V, Vbias = 3.5 Best bias
Band BPF mixer MDS -dBm IF rej spur mixer IIP3 (dBm) @ 20KHz spacing Bias IIP3
IL CL - + avg -6 -3 0 +3 +5 0
-dB -dB BPF BPF -dB dB dBm dBm dBm dBm dBm V dBm
160 3,3 5,68 132 129 58,4 42,4 3,5 42,4
80 1,4 5,60 132 131 58,4 44,2 45,0 46,5 47,0 46,7 3,5 46,5
40 2,3 5,60 132 130 60,0 45,2 3,5 45,2
30 3,4 5,56 133 129 59,2 45,0 3,5 45,0
20 3,4 5,60 133 129 60,0 42,9 3,5 42,9
17 3,0 5,68 133 129 58,0 42,1 3,5 42,1
15 3,9 5,76 132 128 56,4 3,8 41,9 3,5 41,9
12 3,7 5,80 132 126 56,8 40,3 3,5 40,3
10 2,3 5,92 132 127 54,8 40,0 3,5 40,0
6 6,12 124 28,0 37,2 3,5 37,2

The FSAV332 is clearly a winner! With the ADTT1-1 transformer the IIP3 is > +40dBm on all HF bands and not bias point dependent. However spur levels are somewhat problematic and 6M performance is considerably less good, probably due to the limitations of the PCB layout of the mixer.

The ADTT1-1 transformer, first tested with the FSA3157, improves the IP3 especially on the higher bands like it did with the FSA3157 mixer. The price to pay is the increase in conversion loss of roughly 0,6dB.

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