Two Down-Converter models have been custom-designed to operate at K-band (20-40 GHz) and V-Band (50-75 GHz). Gain calibration is accomplished using an internal K- or V-Band noise source, a noise injection coupler, and a precision temperature sensor. Using a +2.0 dBm Ku-Band local oscillator (LO) input to each module, both units employ a sub-harmonic mixer topology to down-convert from the millimeter-wave input frequency to an IF output under 1 GHz, providing 30 dB of nominal gain to the input signal. The V-Band module utilizes an additional diode-based frequency doubler on the LO input, allowing a common local oscillator to drive both modules. Overall, the receiver noise figure is under 4 dB for the K-Band model and under 6 dB for the V-Band receiver. Market applications include comprehensive real time atmosphere profiling for airport air traffic control, severe weather forecasting in support of emergency population evacuations, and homeland security atmospheric sensing.