AWR White Papers

Radar Systems

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OCW Coffee-Can Radar Optimized In 2012, IEEE Spectrum published an article titled, Coffee-Can Radar: How to Build a Synthetic Aperture Imaging System with Tin Cans and AA Batteries. 4 This article described how to build a synthetic aperture radar using a laptop coffee-can radar system that was derived from the OpenCourseWare 5 (OCW) online free course materials provided through MIT. A few years later, Dr. Jim Carroll and Dr. Gent Paparisto decided to redesign the coffee-can radar system using the circuit and system design capabilities within AWR Design Environment software to "recaffeinate" the original design. This application note describes how the original coffee-can radar system was redesigned with AWR ® software, specifically AWR Microwave Office ® circuit design software, AWR VSS system design software, and AWR AXIEM ® and Analyst™ EM simulators, such that it delivers better performance, is less expensive to make and has a smaller footprint than the original system. Original OCW Design The original coffee-can radar was based on the open ISM band at 2.4GHz, which made the parts for these Wi-Fi frequencies easily available. Connectorized Mini-Circuits components could be put together simply by fastening the connectors. The baseband signal from the radar unit was amplified and filtered using breadboard components. A laptop was used to sample the downconverted intermediate frequency (IF), and MATLAB was used for the baseband processing of the signals. The design parameters were 2.4GHz frequency with an 80MHz CW ramp waveform, less than one W of DC power, and less than one W of equivalent isotropic radiated power (EIRP). Figure 6 shows the system diagram superimposed over the top of a photo of the actual radar system. It can be seen that the original design included a voltage-controlled oscillator (VCO), an attenuator buffer between the PA and the VCO, and a 3 dB coupler going out to the transmit antenna and the target, then coming back from the target into the receive path. The low-noise amplifier (LNA) self-mixes down from the VCO signal with the mixer. At this point, users extracted the baseband information with their laptop sound card and then performed the processing with MATLAB. The total bill of materials (BOM) cost at that time was $360, about $240 of which was RF circuit components. The antenna BOM (mostly cabling and connectors) was about $54. Figure 6: The original MIT OpenCourseWare coffee-can radar with connectorized components near the top and the coffee-can antennas on top of the board 4. D. Schneider, "Coffee-can Radar: How to Build a Synthetic Aperture Imaging System with Tin Cans and AA Batteries," IEEE Spectrum, Nov. 1, 2012, http:// spectrum.ieee.org/geek-life/hands-on/coffeecan-radar 5. G. Charvat, J. H. Williams, A. Fenn, S. Kogon, J. S. Herd, "Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar Imaging," MIT OpenCourseWare, http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar- imaging-january-iap-2011/ Radar Systems 7 www.cadence.com/go/awr

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