AWR White Papers

Radar Systems

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An Integrated Framework for Complex Radar System Design Modern radar systems are complex and depend heavily on advanced signal processing algorithms to improve their detection performance. At the same time, the radio front end must meet challenging specifications with a combination of available components, implementation technologies, regulatory constraints, requirements from the system, and signal processing. This application example showcases how AWR Design Environment ® software, specifically AWR ® Visual System Simulator™ (VSS) system simulation software, enables radar system architects and RF component manufacturers to design, validate, and prototype a radar system. This integrated platform provides a path for digital, RF, and system engineers to collaborate on complex radar system design. The example project, Pulse_Doppler_Radar_System.emp, illustrates key models and simulation capabilities available for practical radar design. The project and resulting measurements highlight how to configure a Pulse-Doppler radar and set up the simulation to obtain the metrics of interest for radar development. The entire pulse-Doppler (PD) radar system project includes a linear FM (LFM) chirp signal generator, RF transmitter, antennas, clutter, RF receiver, moving target detection (MTD), constant false alarm rate (CFAR) processor, and signal detector for simulation purposes. Theory of Operation PD radars produce velocity data by reflecting a microwave signal from a given target and analyzing how the frequency of the returned signal has shifted due to the object's motion. This variation in frequency provides the radial component of a target's velocity relative to the radar. The radar determines the frequency shift by measuring the phase change that occurs in the EM pulse over a series of pulses. By measuring the Doppler rate, the radar is able to determine the relative velocity of all objects returning echoes to the radar system, whether planes, vehicles, or ground features. As the reflector (target) moves between each transmit pulse, the returned signal has a phase difference or phase shift from pulse to pulse. This causes the reflector to produce Doppler modulation on the reflected signal. For example, assume a target at a distance R that has a radial velocity component of Vr. The round-trip distance to the target is 2R. This is equivalent to 2R/λ wavelengths or (2R/λ)2π = 4πR/λ radians. If the λ phase of the transmitted signal is Equation 1, then the phase of the received signal will be: If the λ phase of the transmitted signal is φ " , = " + 4 λ dφ dt = 4p l = 4p l 0 then the phase of the received signal will be: φ " , = " + 4 λ dφ dt = 4p l = 4p l 0 The change in phase between pulses is φ " , = " + 4 λ dφ dt = 4p l = 4p l 0 . System Setup The main radar system diagram in Figure 1 includes the following building blocks: linear chirp source, RF transmitter and receiver, and the target and propagation models, as well as the receiver baseband signal processing blocks, including moving target indicator (MTI), MTD, and CFAR. User-defined parameters specifying the gain, bandwidth, and carrier frequency of both the transmitter and receiver sub-blocks can be set to values based on test specifications. A detailed look at the individual components will help explain how this DP radar works. Figure 1: AWR VSS software main radar system diagram showing linear chirp source, RF transmitter and receiver links, target and propagation model, and receiver baseband signal processing blocks. Radar Systems 3

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