C-BAND LOW NOISE HIGH CONVERSION GAIN CASCADED HEMT MIXER

Abstract

A C-band low noise and high conversion gain cascade Single gate high electron mobility transistor (HEMT) mixer is designed and implemented. The cascaded mixer was optimized for high conversion gain and low noise figure by employing low pass interstage matching network and optimized biasing network. The unwanted harmonics are filtered out effectively by low pass interstage matching network. It is observed that the low pass technique of interstage matching network enhances the conversion gain and improves the noise figure of cascaded design. A single stage drain pump HEMT mixer is designed and implemented for the verification of different mixer parameters i.e. conversion gain, noise figure, port to port isolation and intermodulation distortion. A cascaded HEMT mixer simulated, it is observed that if we use both stages in the common source configuration we can achieve high conversion gain and low noise figure. In the desired mixer configuration local oscillator (LO) signal is applied to the drain and Radio Frequency (RF) signal to the gate of FET. An improvement in the conversion gain is achieved by selecting an appropriate value of decoupling capacitors. The simulated cascaded design is implemented. A conversion gain of 15 dB with associated noise figure of 3 dB is obtained from the device.