Active sub-harmonic mixer

Abstract

A superheterodyne receiver is commonly used receiver, but its main problem is its large size. To increase the integration and reduce the size of the receiver, the concept of direct conversion receiver came in the picture. It converts the RF signal into baseband signal (baseband is the signal which has very low frequency) directly in first mixing only. But the major disadvantage is LO (Local Oscillator) self mixing which create DC offset. To solve this issue, the sub-harmonic mixer was introduced. The sub-harmonic mixer presented here is designed using Gilbert cell mixer. Two Gilbert cell mixers are cascaded to facilitate mixing RF signal with second harmonic of the LO signal.