I am using HMC520A in a configurable modulator (QPSK/BPSK). When I am using this as BPSK can I just use one port from IF1 and IF2. Should I leave the other port open or terminate using 50 ohm resistance?
We haven't used the HMC520A as an IQ modulator though it can be theoretically be used as one (ADI has several parts that are better optimized for IQ modulation-https://www.analog.com/en/products/rf-microwave/iq-modulators-demodulators/iq-modulators.html). The IF ports are quadrature so a quadrature signal into the IQ mixer is needed to provide sideband rejection. For the BPSK application I think it would be ok to only use one of the IF ports as no sideband rejection is required. However, the conversion loss will now increase. For QPSK, the application would require a quadrature signal so I think it must use the IF1 and IF2 ports.