This is the transceiver which works as SDR receiver and PSN SSB transmitter utilizing SoftRock RXTX Ensembl. The RXTX Ensembl ordinary works as 1W transceiver with PC system.
However, sometime we get various problems caused by update of Windows and various drivers. In order to avoid them, I made, so called, the all pass filter to generate I,Q signal and put to SoftRock RXTX Ensembl disconnected output signal from PC.
The block diagram shows the all pass filter consisted of 4*2 phase shift circuits with microphone amplifier, hi pass filter, and low pass filer. There are two outputs, I,Q signal, whose phase should be ideally deferent by 90 degrees in all audio frequency range. In the realty, the discrepancy in 0.1 degree makes -55dB side band suppression. This is the target of my system.
The graph shows the phase sift (90 degree base) vs. frequency(100Hz-3KHz). It is the simulation made by Excel to set pole frequency of 8 phase shift circuits. You can see the phase shifts in 3kHz band range are in 0.1 degree discrepancy. The adjustment on my system was made based on this data andI have confirmed it worked the same.
You can get the Excel file by down loading, and the circuit diagram of the block diagram above.