Active antenna with homodyne technique

Abstract

Active Integrated Antenna transceivers can provide cost effective solutions for two-way communications links. At present, most receivers in communication systems adopt the superheterodyne technique. However, superheterodyne receivers have some disadvantages, for example, complex circuitry, high power consumption and the existence of an image-frequency signal. Compared to Homodyne receiver, the receiver can eliminate the IF stage and band pass and band reject filters. A Homodyne receiver scheme constructed with an antenna, low noise amplifier (LNA), a local oscillator (LO), a mixer, a phase shifter and filters is shown in Figure 3.1. The properties of the homodyne receiver is compact circuitry and low power consumption, are desirable for RFIC technology for GSM digital cellular telephone handset. In practice, the homodyne receiver has the following advantages; the compact front-end reduces the interconnection loss between the antenna and circuits; it eliminates the need for conventional circuits and saves printed circuit band space; it is compatible with BPSK, QPSK, FSK, and QAM systems and also applies to beam forming array systems; and is capable of supporting shot range indoor wireless communication such as high-speed digital video signals. In this project, homodyne receivers are implemented based on the active antenna concept. The 50 ? loops across the circular patch antenna will act as a phase shifter. The AIA is designed as IQ Demodulator and the 50 ? loops will provide 90 o phase shift between In-phase (I) and Quadrature (Q) port. Two Schottky diodes would be attached to the loop and used as mixer. The intention of fabricating this active antenna is to provide the compact and efficient receiver architecture. The AIA from shows the ring antenna is needed an additional voltage control oscillator (VCO) to down convert the signal. This paper shows the design of AIA with the addition of the VCO.