A Unique Approach to Frequency-Modulated Continuous-Wave Radar Design

Transcription

1 Electromagnetics Research Group G.L. Charvat, L.C. Kempel, Michigan State University AMTA

2 Overview of Presentation Principles of Frequency-Modulated Continuous-Wave (FMCW) Radar The unique approach to FMCW Radar Range Profile Data Synthetic Aperture Radar (SAR) Imagery Conclusions and future work 2

3 Motivation Requirement: Low cost, short range, low power radar solution for use in high volume applications o Example: Vehicle radar sensors, such as a backup aid or side object detection Problem: Conventional radar becomes more complex as the desired detection range is decreased o Resulting in use of a wider bandwidth shorter pulse which require expensive digitizers to acquire the range to target information Solution: FMCW radar uses a simple FM modulated transmitter, causing the resulting range to target information to be in the form of low frequency (near audio) beats. The lower the beat the shorter the range to target. 3

4 Principles of FMCW Radar FMCW radar is different because it provides range to target information in the form of low frequency (near audio) beats. o This is done by frequency modulating a transmit oscillator, and comparing the current transmitted carrier to the carrier which is reflected from the target o The closer a target, the lower the beat frequency o The further a target, the higher the beat frequency 4

5 Principles of FMCW Radar Practical FMCW design considerations o Transmit to receive antenna coupling Limits sensitivity and dynamic range Causes a false target beat May require delay lines in the system o Producing a linear FM chirp Poor chirp linearity causes degradation in range resolution and maximum unambiguous range Overall decrease in range accuracy 5

6 The MA Gunnplexer This transceiver module is based around a voltage controlled Gunn Diode oscillator, a single Schottky diode mixer, and a fixed ferromagnetic circulator This component has many interesting problems o o o o Tuning linearity Tuning instability due to temperature and VSWR reflections Noise figure of 10 db, or worse Poor mixer response near DC 6

7 A Unique Approach to FMCW Radar Design Taking into account the FMCW radar design considerations, and the drawbacks to using Gunnplexer type transceiver modules, a unique approach to FMCW radar design was created. Design approach based on 2 transceiver modules, coupling power from one to the other for use as an LO reference 7

8 System Implementation The system is broken down into three major subsystems o The Front End Assembly o The IF Chassis o Data Acquisition 8

9 Range Profile Data 30 dbsm target located 20 ft from the system Range to Target 30 dbsm target located at 35 ft from the system Range to Target Amplitude (V*10,000) Series1 30 dbsm target located at 30 ft from the system Amplitude (V*10,000) Series Beat Freqeuncy (Hz/20) 500 Range to Target Beat Frequency (Hz/20) dbsm target located at 25 ft from the system Amplitude (V*10,000) Series1 30 dbsm target located at 40 ft from the system Range to Target Range to Target Amplitude (V*10,000) Series Beat Frequency (Hz/20) Amplitude (V*10,000) Series Beat Frequency (Hz/20) Beat Frequency (Hz/20) 9

10 Range Profile Data The results indicate a small range offset within the system of approximately ft on average. Actual Distance (ft) Measured Distance (ft) Range Difference (ft)

11 Synthetic Aperture Radar SAR experimental setup 30 dbsm Target 20 dbsm Target 11

12 EM Group Synthetic Aperture Radar 30 dbsm target located at 25 ft from the system S1 S7 S13 S19 S25 S S S S S37 S61 S67 S73 S79 S85 S S S103 12

13 EM Group Synthetic Aperture Radar 20 dbsm target located at 25 ft from the system S1 S7 S13 S19 S25 S31 S37 S43 S49 S55 S61 S67 S S79 S85 S91 S S103 13

14 EM Group Synthetic Aperture Radar 20 dbsm target located at 25 ft from the system, and the 30 dbsm target located at 40 ft from the system S1 S7 S13 S19 S25 S S S43 S49 S55 S S S S67 S85 S91 S S103 14

15 Conclusions and Future Work A unique low-cost FMCW radar system that uses commonly available parts Good Synthetic Aperture Radar performance using the unique FMCW radar solution This research has shown that the unique solution to FMCW radar works, and proven capable for use in more advanced applications such as Synthetic Aperture Radar Future outlook: o Increasing chirp bandwidth o Greater transmit power o A better solution to the range linearity problem 15