.3 Mm Band Radiometer

3mm band radiometer was studied in this paper. For system design section, two types of radiometer suit for 3mm band: total power and Dicke, were discussed. With their principles being introduced and having them compared from several aspects, we decided to develop a super-heterodyne total power radiometer at 3mm band. Other questions like single-side band/double-side band, digital integration and aperture calibration, were talked after system parameters were calculated. For system circuitry design section, millimeter wave multi-mode antenna, W-band single-end balanced diode mixer and cavity-stabilized IMPATT Diode Oscillator, were introduced. Isolator was also discussed by taking the receiver's inverse radiation noise in to account when absolute calibration is necessary. Balanced mean square-law detector, having relative high stability with a feedback loop, was derived from the common Schottky barrier diode detector. After that, calculation principles and method of IF gain was presented, the 1st and 2nd IF circuitries were implemented with MMIC amplifiers. At last, Difference amplifier, auto gain control model, data acquisition system, USB interface and temperature holding circuitry were discussed briefly. For signal processing section, the algorithm of digital integration was analyzed and simulated as an FIR filter; Allan variance was introduced to estimate noise sources that interfering the radiometer. An algorithm of 2-point Allan variance was found, which in turn verifies the efficiency of Allan variance in determining several kinds of noises.