K-band UWB radar front-end with coherent pulsed oscillator

Abstract

A K-band CMOS UWB radar front-end with coherent pulsed oscillator is proposed. At first, UWB transmitter with a bi-phase modulating pulsed oscillator is present. A variable delay circuits for calculating the distance to the target combines a synchronized 9-bit counter and Vernier delay line. The proposed bi-phase modulation technique in baseband control signal generator, which uses asymmetric control of an LC oscillator, has low complexity and a high level of efficiency. And a pulsed oscillator scheme is used because of its suitability for low power consumption and avoidance of LO leakage. The proposed output buffer structure operates as a set of TX/LO switches. The generated signal consequently has a minimum pulse width of about 280 ps which corresponds to the range resolution of 4.2 cm, and a peak power level of about 2 dBm. And the operation of bi-phase modulation and pulse position modulation is confirmed by the spread of spectral lines. Additionally, a K-band UWB radar transceiver including the proposed radar transmitter is demonstrated. A merged LNA and mixer scheme is adopted for receiving the reflected signal. The measurement results show that the maximum error is only 3.75 mm in the range of 0.15 m ~ 8.4 m, and the range resolution is less than 10 cm. The total power consumption of the core circuit is 6.89 mA with the supply voltage of 1.5 V, which is the lowest power consumption of reported UWB transceiver chips. Finally, a K-band UWB timed-array radar system for both range and direction detection is proposed. An RF delay line using a phase shifter is adopted for high angular resolution, and the trigger signal control method is used for resolving gain mismatch problem and for attaining wide angular coverage with small chip area. In addition, bi-directional beam-forming can achieve narrow beam-width, which is advantageous for accurate detection. The proposed timed-array UWB radar system can attain the angular resolution of 9° in the range of -45° to...