Design, Implementation and Calibration of Compact MIMO 5.8 GHz Radar/RFID Transceiver Frontend

Abstract: The project deals with design, implementation and calibration of 5.8 GHz

(ISM band) RFID/radar transceiver frontend. The idea is based on the

implementation of the principle of FMCW (Frequency Modulated Continuous Wave) radar to estimate the Angle of Arrival (AOA) for 3D positioning. MIMO implementation is realized with one transmit and three receive channels.

Such systems are affected by noise; thus, emphasis is given to generate stable 5.8 GHz frequency synthesizer to reduce the phase noise. Accordingly, a board with PLL-VCO (Phase Locked Loop- Voltage Controlled Oscillator) combination

circuit is implemented and tested.

Homodyne (direct conversion) transceiver architecture is used due to its low hardware complexity. One of its main disadvantages is the DC offset created by self-mixing of the local oscillator at the receiver. This and related problems call for Calibration circuit. Besides, since the transceiver implements quadrature modulation, some components such as mixers corrupt the signal by introducing carrieleakage, quadrature imbalance and phase skewing. These effects are mitigated with the help of the calibration circuit. Since calibration is done first or the transmitter and then for all of the three receive channels, the whole system will be calibrated.

Successful operation of transceiver circuit depends also on good componentselection, power planning and applying principles of high frequency design carefully. Discrete circuit implementation is followed due to its ease of manufacturing and testing compared to MIC or MMIC implementations. Design tools such as Matlab and Agilent ADS were used when needed. Circuit schematics and layout was designed with Cadsoft Eagle.