And compromises factor desired why trade off required

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Unformatted text preview: eases the signal­to­noise ratio (good) Distorts the transmitted pulse (bad) Receiver Sensitivity Receiver Sensitivity Smallest return signal that is discernible against the noise background x An important factor in determining the unit’s maximum range x Summary of Factors and Compromises Summary of Factors and Compromises Summary of Factors and Compromises Factor Desired Why Trade-off Required Pulse Shape Sharp a rise as possible Better range accuracy Require infinite bandwidth, More power /longer range more complex Tall as possible Requires larger equipment More power Pulse Width Short as possible Closer minimum range More accurate range Pulse Repetition Freq. Short Better range accuracy Reduces maximum range Better angular resolution Better detection probability Pulse Compression Uses technique Greater range Shorter minimum range Reduces maximum range More complex circuitry Summary of Factors and Compromises Summary of Factors and Compromises Summary of Factors and Compromises Factor Desired Power More Greater maximum range Requires larger equipment & power Beam Width Narrow Greater angular accuracy Slow antenna rate & Detection time Carrier Frequency High Greater target resolution Detects smaller targets Smaller equipment Reduces maximum range Receiver Sensitivity High Maximizes detection range More complex equipment Receiver Bandwidth Narrow Why Trade-off Required Better signal-to-noise ratio Distorts pulse shape Types of Combined Types of Combined Radar Systems x Frequency Modulated CW Radar x x Pulse Doppler x x x Carrier wave frequency within pulse is compared with a reference signal to detect moving targets. Can use Bandpass Filter to remove signal from signals that do not have a specific Doppler shift. Moving Target Indicator (MTI) System x x Use for radar altimeters and missile guidance. Signals compared with previous return to enhance moving targets. (search radars) Frequency Agile Systems (change freq. with time) Modulating the Modulating the Radar’s Wave 4 Amplitude Modulation – Vary the amplitude of the carrier sine wave 4 Frequency Modulation – Vary the frequency of the carrier sine wave 4 Pulse-Amplitude Modulation – Vary the amplitude of the pulses 4 Pulse-Frequency Modulation – Vary the Frequency at which the pulses occur...
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This document was uploaded on 03/28/2014.

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