The protoTx PTX-0350 is a user-programmable I/Q to RF upconverter and IF to RF upconverter with internal LO synthesizer. The PTX-0350 is programmed over USB 2.0 with a Windows-based soft front panel. User settings are stored in nonvolatile memory and recalled at power-up, enabling applications in target systems without USB control. The internal LO synthesizer has excellent spectral purity and can be locked to an external 10 MHz reference or the internal TCXO. For ultra-low phase noise or fast-switching LO applications, an external LO signal can be provided by the user. Programmable settings include operating mode, internal LO frequency, internal/external LO, internal/external reference, DC offsets for LO nulling control, RF filter select, RF step attenuator level, output enable/disable, and user/factory preset mode.