14-12-2022, 10:43 AM
Roger
There a lot of similarities between that PCB and the W1GHZ PCBs for 2.4 and 3.4GHz (at least the older version). The mixer goes at the RHS of your photo directly onto pads then to the tracks marked for IF and LO, the 70CM BPF in the centre and what I assume is an SMD RF switching device before heading off to two MMICs in each leg, transmit and receive.
The MMIC biassing is simple, one resistor that is determined by the MMIC type and the applied voltage with +8 is marked on the PCB. You can do some sums using loss figures for the ADE5 ( 6dB at 430 when using about +7 dBm LO level), then allow about 6dB loss for the BPF, 1-2dB for the SMD RF switch chip then start adding gain figures for the MMICs. The output device on TX was probably an MAV11 and that will produce maybe +16 dBm out. Thus you can work out the TX stage gain required for a 0dBM input level on transmit. Note the 1dB compression values of the MMIC chips, as well as the gain values, so that you are not expecting more output than the devices are capable of producing.
The RX chain probably has an ERA5 as a 1st chip, and maybe even a jumper across the 2nd MMIC position, as the total stage gain can again be calculated. Use -107dBm (1uV) as a starting point for rx input level, then add gain and loss figures along the chain so that it has a gain rise of about 10 to 20dB across RX input port to the IF output port.
The final step is to work out MMIC bias resistor values. Use SMD chip caps, probably also 0805 parts, to couple signals or bypass points to ground. Typically 100pF at 70CM for coupling, 470pF to 1000pF (sorry 1nF !!) for bypasses. Final C values are not critical.
Be sure that the TX drive at the IF port does NOT exceed around 0dBm else mixer overload or destruction can occur.
Of course, time has moved on and there are better MMICs now than when that PCB was designed so some research about what will fit the PCB layout, and is currently available, is in order.
Doug
There a lot of similarities between that PCB and the W1GHZ PCBs for 2.4 and 3.4GHz (at least the older version). The mixer goes at the RHS of your photo directly onto pads then to the tracks marked for IF and LO, the 70CM BPF in the centre and what I assume is an SMD RF switching device before heading off to two MMICs in each leg, transmit and receive.
The MMIC biassing is simple, one resistor that is determined by the MMIC type and the applied voltage with +8 is marked on the PCB. You can do some sums using loss figures for the ADE5 ( 6dB at 430 when using about +7 dBm LO level), then allow about 6dB loss for the BPF, 1-2dB for the SMD RF switch chip then start adding gain figures for the MMICs. The output device on TX was probably an MAV11 and that will produce maybe +16 dBm out. Thus you can work out the TX stage gain required for a 0dBM input level on transmit. Note the 1dB compression values of the MMIC chips, as well as the gain values, so that you are not expecting more output than the devices are capable of producing.
The RX chain probably has an ERA5 as a 1st chip, and maybe even a jumper across the 2nd MMIC position, as the total stage gain can again be calculated. Use -107dBm (1uV) as a starting point for rx input level, then add gain and loss figures along the chain so that it has a gain rise of about 10 to 20dB across RX input port to the IF output port.
The final step is to work out MMIC bias resistor values. Use SMD chip caps, probably also 0805 parts, to couple signals or bypass points to ground. Typically 100pF at 70CM for coupling, 470pF to 1000pF (sorry 1nF !!) for bypasses. Final C values are not critical.
Be sure that the TX drive at the IF port does NOT exceed around 0dBm else mixer overload or destruction can occur.
Of course, time has moved on and there are better MMICs now than when that PCB was designed so some research about what will fit the PCB layout, and is currently available, is in order.
Doug
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.