Emission characteristics of atomic and ionic pulsed metal vapor lasers are given in Table 9.3. the transmitted signal should be equal in magnitude to the reference signal. (This is the case when the target tracked is at a higher altitude than the platform.) This Radar Is Suitable For Both Air-to-air Combat And Air-to-ground Weapon Delivery Missions. This can also be a problem for detecting low-flying aircraft because of ground terrain clutter at similar ranges in the mainlobe of the radar. Perhaps the most well-known member of this subgroup is the copper laser, which is also referred to as the copper vapor laser (CVL). Q-switching, mode-locking and regenerative amplification. Rapid progress has taken place over the past 10 years in the field of diode-pumped solid-state lasers, and more specifically in the emerging area of ytterbium-doped (Yb-doped) laser systems. Another benefit is that since more pulses are transmitted in a given interval of time, higher average transmit power levels can be achieved. These lasers have found numerous applications due to their ability to emit large average powers in the green at λ = 515.55 nm and, at their secondary emission wavelength, at λ = 578.21. The higher the pulse repetition frequency, the better is the unambiguous measurement of the velocity (see Doppler ambiguity ). Home / Job Exam Papers / Multiple Choice questions for ECE. This opens the route to the development of highly energetic short-pulse sources with a high pulse repetition frequency (PRF), which implies an increasing number of new applications in industry [1, 2], medicine and science [3, 4]. A pulse Doppler radar uses the Doppler shift to discriminate moving targets from stationary clutter. T/d b.P/T c.P/d d.d/T. b. good target discrimination. c. 1000 us . Another alternative is to use a technique called FM ranging (Fig 19.6). The pulse Doppler radar usually uses filter banks, which are implemented with a discrete Fourier transform rather than delay cancellers to remove the clutter. Terminal Doppler Weather Radar (TDWR). The doppler spectrum of the sea echo obtained by an HF radar can also be used to extract the strength and direction of the winds over the ocean. 8. These are: A moving target indicator (MTI) radar in which the pulse repetition frequency (prf), denoted by fp, is low enough to have no range ambiguities; i.e., its maximum unambiguous range Runam = c/2 fp. The radar front-end is based on an RF MEMS electronically scanned array (ESA) design and low-loss MEMS time-delay units (TDU), which offer cost and performance advantages over the other technologies. The quasi-peak detector is a peak detector with weighted charge and discharge times (Table 7.1) which correct for the subjective human response to pulse-type interference. There will be, however, many range ambiguities because of the high prf. Higher in Frequency. c. pulse interval. Therefore, the receiver is not desensitized by the transmitter's high power at the received signal frequency. Multiple Choice questions for ECE Suresh Bojja. The frequency over time looks like a “sawtooth wave.” The receiver can operate during transmit operation, as the receiver is detecting time-delayed versions of the transmit signal, which are at a different frequency than current transmit operation. The following are regions of Doppler space where targets with those Doppler velocities cannot be detected: 14. So, the delay line is mainly used in Delay line canceller in order to introduce a delay of pulse repetition time. Therefore, the radar will be more accurate in the distance measurement. Range ambiguities are resolved and the true range is found by transmitting three separate waveforms, each at a different prf. This is the Multiple Choice Questions in Chapter 16: Radar Systems from the book Electronic Communication Systems by George Kennedy. Conventional designs use a Marx generator to develop these signals. Pulse Repetition Frequency. The front-end module was fabricated on a 6-inch fused silica wafer and a Rogers TMM3 substrate using wafer-scale monolithic tile construction. In the figure the time between successive pulses is given as 1 millisecond (10 −3 second), which corresponds to a pulse repetition frequency of 1 kilohertz (kHz). Q17. 127)The ability of the receiver to respond to the weakest signal is called ... Pulse repetition frequency D)Station frequency. In this chapter, we will learn about Delay Line Cancellers in Radar Systems. Medium-PRF operation is a compromise. The characteristic feature of coherent MTI radars is that the. Radar Systems have a greater range and range resolution when the transmitted signal has a high peak power and short pulse duration. anti-jamming, the high pulse repetition frequency (HPRF) synthetic wideband waveform has been used for radar imaging in supersonic/hypersonic aircraft guidance [1–5]. PHILIPPE LACOMME, ... ERIC NORMANT, in Air and Spaceborne Radar Systems, 2001. 16.9. References relate to bandwidth exclusively. The radiation patterns of the transmitting and receiving modules are shown in Fig. These lasers have found numerous applications due to their ability to emit large average powers in the green at λ = 515.55 nm and, at their secondary emission wavelength, at λ = 578.21. The clutter-rejection notches may be widened by passing the output of the delay line canceller through a, 11. Required fields are marked *. Michael Parker, in Digital Signal Processing 101 (Second Edition), 2017. Question: Question 2 A 10.5 GHz Airborne Radar Is Operating In High Pulse Repetition Frequency (PRF) Single Target Track Mode. As the name suggests, delay line introduces a certain amount of delay. Pulsed radars that are not required to be Doppler sensing systems have traditionally employed low pulse repetition frequency (PRF) waveforms. When flown in an aircraft for purposes of air-surveillance, these are called AMTI, or airborne moving target indicator radar. Multiple Choice Questions MTI andPulse Doppler Radar. 16.8. The doppler frequency shift is important for many purposes in radar. What is the typical frequency range about the center frequency of a tunable magnetron? c) Varactor diode modulator. Therefore, the quasi-peak response de-emphasizes the peak response at low PRFs, or to put it another way, pulse-type emissions will be treated more leniently by a quasi-peak measurement than by a peak measurement. A 38-GHz high-pulse repetition frequency (HPRF) mono-pulse Doppler-radar front-end was developed at the University of Michigan by Caekenberghe et al.28,29 for a long-range automotive radar application such as pre-crash detection and ACC. When no clutter is present (as when the antenna beam is looking up above the surface of the earth), a low prf waveform without any doppler processing might be employed. Pulse interval 4. Answer: determine the relative velocity of a target. As shown in the figure, Radar transmits a periodic signal. Two passive sub-arrays, as the key units, are composed of 16-dB-gain 64 elements of microstrip antennas optimized at 38 GHz. Since CISPR-based tests have historically been intended to protect the voice and broadcast users of the radio spectrum, they lay considerable emphasis on the use of the QP detector. implementation of high resolution.Wideband radar pulsescomplicate the design of transmitters and receivers and also, such receivers are prone to interference from other sources. High PRF operation spreads out the frequency spectrum of the receive pulse, allowing a full Doppler spectrum without aliasing or ambiguous Doppler measurements. Add your answer and earn points. The energy content of the pulse is equal to the peak (maximum) power level of the pulse multiplied by the pulse width. What is the maximum range of the radar a) Power return factor. Q16. To get the highest power, long transmit pulses are sent, and correspondingly long-matched filter processing (or pulse compression) is used. Seconds). c) pulse repetition frequency. The clutter that is present in the spectrum is not folding or aliased from higher frequencies, which lowers the noise floor of the receive spectrum. 2. Both range and Doppler measurements are ambiguous, but each will not be aliased or folded as severely as the more extreme low- or high-PRF modes. This can help improve the detection range of a radar system in high PRF mode. The following discussion summarizes the trade-offs. These are located in the vicinity of major airports to warn aircraft, that are landing or taking-off, of the presence of dangerous wind shear. This is called mainlobe clutter rejection, or filtering. Since bandwidth is a critical requirement for radar systems, and available unlicensed frequency spectrum is limited at already … Except for certain relatively high pulse repetition frequencies, which Chapter 8 will examine, velocity foldover is practically equivalent to projection along the range axis. Which may be used to tune the radar synchronizer B. 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