Design and Development of 100 GHz Quadrature Heterodyne Interferometer system at IPR

In this paper, we are report design, development, and characterization of indigenously developed 100 GHz Heterodyne interferometer system which provides real time plasma density measurement. The developed system consists of two free running Gunn oscillators which have been used as radio frequency source (RF) and local oscillator (LO) and produce stabilised intermediate frequency (IF) of 850 MHz using biased mixers for the down conversion at low power of LO.The IF signal is then coupled to an IQ demodulator for the generation of IQ signals. IQ for in phase and quadrature phase are known as IQ. Using highly stabilised signal conditioning electronics and DAQ system, the IQ signal is then processed by the Arctan function in MATLAB and LABVIEW for the phase measurements. Also these signals are coupled to FPGA based system to generate real-time signal. The developed system has the sensitivity or the noise floor - 69 dBm and dynamic range - 65dBm to -10dBm. The IQ phase imbalance is +/-15 degree(0.26 radian)