Implementation of an X-band FMCW Marine Radar System
|關鍵字:||雷達;調頻連續波;radar;frequency modulated continuous wave|
|摘要:||本論文利用調頻連續波 (Frequency Modulated Continuous Wave, FMCW)的概念，實現了用於偵測船舶距離的雷達系統。本系統在中心頻率為9410 MHz、頻寬為50 MHz、掃頻時間為250 s之規格下操作。系統分成三個部分：穩定的本地振盪器、發射模組與接收模組。將低雜訊放大器操作在非線性工作區，以達到倍頻器電路的效果，以設計9210MHz之本地振盪器(相位雜訊為-130dBc/Hz @1MHz)。天線陣列乃使用一維的微帶天線且陣列單元間距為半波長，天線間之隔離度達到60dB以上。利用FMCW雷達原理，量測發射波與回波之差頻藉以計算電波飛行時間(time of flight)，我們使用電腦程式執行快速傅立葉轉換，取得發射端與接收端之FMCW頻率差資訊。
In the thesis, a X-band marine frequency modulated continuous wave (FMCW) radar system is developed. Such a radar system is operated at center frequency 9410 MHz with 50 MHz sweep frequency bandwidth and 250 microsecond sweep time. The overall system can be decomposed into three parts: stable local oscillator (STALO), transmitter- and receiver- module, respectively. To have a low phase-noise of the STALO, the multiplier made up of a low-noise amplifier operating in the nonlinear region is employed to obtain a 9210MHz continuous wave from a low phase-noise (around -130 dBc/Hz @ 1MHz) input signal (centered at 2302.5 MHz). The transmitting and receiving antennas are composed of one-dimensional patches array with half-wavelength separation period. Additionally, the isolation between them is up to 60 dB. The fast Fourier transform (FFT) is exploited and implemented via computer program for extracting the beat frequency between the transmitted- and received- FMCW signals. The performance of this radar system has been evaluated using the radar target simulator by dynamically manipulating the transmitted FMCW signal and processing by the receiver to figure out the distance accordingly. The measured results indicate that the range resolution is 3 meter, which coincides with theoretical value.