A family of RF/microwave downconverters consists of five PXI (3U) modules: preselector, microwave downconverter, RF downconverter, local oscillator, and IF downconverter. The programmable modules can be arranged into six primary configurations operating over 100-kHz to 2.9-GHz, 2.7- to 26.5-GHz, and 100-kHz to 26.5-GHz frequency ranges. They can perform various RF/microwave signal analysis functions or emulate older/obsolete instruments when operated in conjunction with PXI or PXI Express digitizers/controllers and DSP software. The modules are intended for use with LabVIEW, LabWindows/CVI, NI Modulation Toolkit, NI Spectral Analysis Toolkit, or user-provided DSP software.