JUMA TRX2 Polyphase board description Last update 2007-12-03 OH7SV

In the JUMA TRX2 there are two identical polyphase modules. Both of these plug-in modules are plugged into the main board. One module is in the RX section and the other is in the TX section. The purpose of the polyphase modules is to suppress the unwanted side band in the direct conversion method by means of phase shift. There are no adjustable parts.

JUMA-TRX2 Polyphase module

In the RX section the polyphase is fed by the qudrature I - Q audio signal with the complement signals coming from the QSD RX muxer. The phases of these four fed signals are 0, 90, 180 and 270 degrees. The Q signal is delayed by 90 degrees from the I signal. After summing the signals the unwanted side band is in opposite 180 degree phase and thus suppressed.

Correspondingly in the TX section the singe phase audio signal is split into the I - Q and the complement signals. These signals are fed to the commutating TX muxer which provides SSB RF signal.

There are no adjustable things in the polyphase module. The unwanted side band suppression is optimized for 300 Hz...3 kHz range by simulation. The absolute vales of the components are not critical but the performance of the polyphase depends on the deviation of the components in each "column" in the circuit. The design is done so that when using the specified components the unwanted side band attenuation is very good (better than 50 dB). The deviation comes mainly from the capacitors, the resistor are more accurate 1% type. The performance can be optimized, if desired, to a superb level (60 dB...70 dB) by screening close values of the capacitors in each "column".

Six columns in the JUMA-TRX2 polyphase module