I am working on a mixer which will be used for 4QAM, QPSK. The local oscillator is 9.6 kHz and the IF would be + or - 1 volt DC in order to have the RF port output either cosine or -cosine. Which type of mixer architecture would satisfy this? Any design ideas are welcome.
Use two opamps to generate the positive and negative versions of the carrier. Alternatively a center-tapped transformer will do. Then switch between the two phases via an analog switch controlled by the baseband. There are dedicated switch ICs available, but it may be as simple as two complementary transistors (BJT or MOSFET).