I'm trying to design an analog portable single side band receiver (ham radio transceiver in future).
I am looking for a good matching components.
Initially I started with SA612 mixers but I was disappointed by their noise level.
So I tried AD831 which had almost no gain while dissipating tonnes of heat. I understood I was foolish underestimating their power consumption and made many mistakes.
I have drawn this block diagram:
It uses Si5351 as VFO. First mixer VFO is set above receive frequency. RF BPF is up to 2MHz wide. IF 8MHz BPF is 3 KHz wide. LO can move up & down to be able to receive USB or LSB.
Now I am trying to build something which will be power efficient, compact.
So I picked LT5526 as double balanced mixers.
But I am looking at LT5560 and LTC5562.
LTC5562 seems having better characteristics and claims to have ESD protecting which sounds important for HF applications having an external antenna. The only caveat it has some note about external matching for lower frequencies which is my case.
For IF amplifier I picked AD8338. It has attracted me by presence of AGC and 80dB of dynamic range. But I struggle a little bit with proper configuration for this chip. I had to manually set AGC setpoint. Also I think I made poor decisions regarding my PCB design, I guess it starts self excitation. Many people recommend 4 layers board but it is an overkill for ham radio. I think it is doable with 2 layers. Also I was thinking to tap to AGC loop and use it for S-meter.
Next, I am thinking about some LNA after RF bandpass filters but unsure about it. In different designs I see LNAs and attenuators there. If signal will be stong it will overload LNA and small signal might be lost. From the other side, ham radio signals are usually very weak unlike broadcast radio stations so it worth to have it.
For audio amplifier I used SSM2211 and LM358 as preamp/filter. It is the only one which has option to have single ended output which is one my requirements.
TBH, I am not RF engineer and radio is my hobby so I am very welcome to any advice.
[edited by: zoonman at 4:21 AM (GMT 0) on 21 Jan 2020]