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Lecture_4_Radar_Principles(1)

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Unformatted text preview: maximum range of the system – Otherwise, reception of return will be obscured by the succeeding pulse Pulse Transmission Pulse Transmission Pulse Width (PW) – Determines the minimum range at which a target can be detected – The active transmit time (μsec) – If target so close to transmitter that echo received before transmission is cut off and receiver turned on, echo not displayed Need short pulses to detect close targets Pulse Transmission Pulse Transmission Pulse Repetition Frequency (PRF) – Number of pulses transmitted per second (Hz) Radio Frequency (RF) – The working/operating frequency – The frequency of the carrier wave being modulated, forming the pulse train Rest Time (RT) – Non­transmit time or time between pulses Pulse Transmission Pulse Transmission PRT Rest Time PRT = PW+RT Rest Time PRT = 1/PRF Pulse Transmission Pulse Transmission Note: – Pulse width must be short to increase reception of nearby targets and yet contain sufficient power to ensure a return echo of enough magnitude from max range of system, LARGE TRANSMITTED POWER outputs are required to produce pulses with sufficient energy Duty Cycle Duty Cycle Duty Cycle Duty Cycle Peak Power Peak Power Pulse Xmsn Key Points Pulse Xmsn Key Points Varying the pulse width affects the range of the radar – Need short pulses for short range targets PW determines radar’s minimum range resolution The slower the PRF the greater the radar’s maximum range The faster the PRF the greater the radar’s accuracy Range Determination Range Determination Basic Radar Components Basic Radar Components Typical pulse­echo radar systems are composed of seven basic components Transmitter Transmitter Generate high­power pulses under control of a timer – Carrier wave is produced/modulated Receiver Receiver Converts incoming EM at a tuned frequency into electrical signals that can be used by a signal processor Power Supply Power Supply Furnishes all AC and DC voltages necessary for the operation of the system – Pulse power generated can be MUCH greater than the power supplied b/c energy can be stored during the rest time in capacitors Synchronizer Synchr...
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