Based On Six-port Direct Conversion Receiver Front End

The original six-port technique applies only to alternative network analyzers. Since the late 1990s, the six-port technique has also been used for wireless communications receivers. And the receiver based on six-port is proved to be a very promising candidate to be a reconfigurable, reprogrammable, multi-band, multi-standard receiver front-end. The aim of this work is to research the six-port theoretical background, and design a Ka-band direct conversion receiver front-end based-on six-port.First, we introduce the six-port receiver theory using the additive mixing, and we study a very convenient calibration algorithm which can improve the performance of the six-port receiver. We also give an accurate mathematical description of the frequency conversion and demodulation process in six-port receivers.Next, we give details about our newly developed six-port receiver front-end including the power detectors. The six-port junction using a Wilkinson coupler and three branch line couplers is fabricated on a 0.254mm ceramic substrate, and the measurement results show that it is suitable for being used in a six-port receiver. The detectors using MSS20,141B10D zero biased low barrier Schottky diodes are on a 0.254mm RT5880.Finally, we present a six-port receiver front-end realized in monolithic microwave integrated circuit (MMIC) technology using OMMIC 0.18μm GaAs PHEMTs foundry named ED02AH. The circuit combines all the essential functions, namely the six-port junction and four GM Schottky diode detectors, and the size is 2.5×3.5 mm 2.