Electromagnetics Research Group G.L. Charvat, L.C. Kempel, Michigan State University AMTA 2004 1
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
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
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
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
The MA87127-1 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
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
System Implementation The system is broken down into three major subsystems o The Front End Assembly o The IF Chassis o Data Acquisition 8
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 500 500 450 450 400 400 Amplitude (V*10,000) 350 300 250 200 150 100 50 Series1 30 dbsm target located at 30 ft from the system Amplitude (V*10,000) 350 300 250 200 150 100 50 Series1 0 0 20 40 60 80 100 120 Beat Freqeuncy (Hz/20) 500 Range to Target 0 0 20 40 60 80 100 120 Beat Frequency (Hz/20) 450 400 30 dbsm target located at 25 ft from the system Amplitude (V*10,000) 350 300 250 200 150 Series1 30 dbsm target located at 40 ft from the system Range to Target Range to Target 100 500 50 500 450 0 Amplitude (V*10,000) 450 400 350 300 250 200 150 Series1 0 20 40 60 80 100 120 Beat Frequency (Hz/20) Amplitude (V*10,000) 400 350 300 250 200 150 Series1 100 100 50 50 0 0 20 40 60 80 100 120 Beat Frequency (Hz/20) 0 0 20 40 60 80 100 120 Beat Frequency (Hz/20) 9
Range Profile Data The results indicate a small range offset within the system of approximately 13.98 ft on average. Actual Distance (ft) 20 25 30 35 40 Measured Distance (ft) 30.702 38.199 44.182 50.337 55.692 Range Difference (ft) 10.72 13.199 14.982 15.337 15.962 10
Synthetic Aperture Radar SAR experimental setup 30 dbsm Target 20 dbsm Target 11
EM Group Synthetic Aperture Radar 30 dbsm target located at 25 ft from the system S1 S7 S13 S19 S25 S31 8000-9000 S43 7000-8000 6000-7000 S49 5000-6000 S55 4000-5000 S37 S61 S67 S73 S79 S85 S91 3000-4000 2000-3000 1000-2000 0-1000 S97 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 109 115 121 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 S103 12
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 S73 2500-3000 2000-2500 1500-2000 1000-1500 500-1000 0-500 S79 S85 S91 S97 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 3000 2500 2000 1500 1000 500 0 S103 13
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 S31 3500-4000 S37 3000-3500 2500-3000 S43 S49 S55 S61 2000-2500 1500-2000 S73 1000-1500 500-1000 S79 0-500 S67 S85 S91 S97 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 109 115 121 4000 3500 3000 2500 2000 1500 1000 5000 S103 14
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