Pulse radar

Classical pulse radar emits high power (Pr) short electromagnetic pulses using a directional transmitting antenna of gain Gt The power density at the target at distance R from the transmitter is equal to [44]... 

For pulse radar, the receiver s bandwidth B is inversely proportional to the pulse width tp. Substituting the receiver s bandwidth by pulse time in (7), one obtains the equation... 

It has to be noted that the measurement values for range and velocity are not uncorrelated according to the LFMCW measurement described in section 8. As a consequence, the observed measurement errors ft, can also be considered as correlated random variables for a single sensor s data. For 24GHz pulse radar networks, developed also for automotive applications, a similar idea has been described by a range-to-track association scheme [12], because no velocity measurements are provided in such a radar network. 

M. Klotz An Automotive Short Range High Resolution Pulse Radar Network, PhD thesis, TU Hamburg-Harburg, 2002. 

Properly designed hardware is important to any successful detection scheme. At first glance, the NQR hardware requirements are deceptively simple a device to generate a strong RF magnetic field and another to detect a weak RF magnetic field. Clearly, there are parallels between these requirements and those of pulsed radar, and some early NMR systems were built around surplus radar hardware. In this section, NQR hardware and how it affects detection sensitivity is discussed. 

As mentioned previously, we tried two concepts for the duplexer. One concept is that introduced by Haeberlen for pulsed NMR (Haeberlen, 1967) in pulsed radar it was common even then. We will call this... 

Geoff A. Burrell Leon Peters, JR. 1979. Pulse propagation in lossy media using the low-frequency window for video pulse radar application. Proceedings of the IEEE, 67(7) 981-990. 

The thickness of the asphalt layer may also be determined by a non-destructive method using short-pulse radar, according to ASTM D 4748. 

The over-all system configuration is presented in Section 7.3.1. In Sections 7.3.2, 7.3.3, and 7.3,4, we consider applications of the system to a cw radar with sinewave, Gaussian/Gaussian, and Gaussian/Lorentzian input signals, respectively. Section 7.3.5 deals with its use in an analog communications system, whereas Section 7.3.6 is concerned with low-frequency applications of the technique. A numerical example in Section 7.3.7 is followed by evaluations of system performance for binary communications and pulsed radar in the vacuum channel (Sec, 7.3.8) and in the lognormal atmospheric channel (Sec. 7.3.9). A discussion is presented in Section 7.3.10. The main results are expressed as the output SNR for the system in terms of the input SNR. 

The previous subsections were primarily concerned with the behavior of the three-frequency nonlinear heterodyne system for applications in cw radar and analog communications. As such, a determination of the output signal-to-noise ratio (SNR)o was adequate to characterize the system. In this subsection, we investigate applications in digital communications and pulsed radar, and therefore examine system performance in terms of the error probability P. Evaluation of the probability of error under various conditions requires a decision criterion as well as a knowledge of the signal statistics we now investigate operation of the three-frequency nonlinear heterodyne scheme in the time domain rather than in the frequency domain. 

We begin with an investigation of binary communications and pulsed radar for both nonorthogonal and orthogonal signaling formats in the vacuum channel. In Section 7.3.9, we examine envelope probability distributions and... 

The three-frequency nonlinear heterodyne system can also be used for pulsed radar applications. The configuration is similar to that considered previously. Pulses are sent to the target and the maximum-likelihood test is used to determine whether the target is or is not present (reflected or scattered signal deemed present or absent). For a detailed treatment of conventional range-gated pulsed radar applications, the reader is referred to the book by Davenport and Root [7.74]. 

Application to Binary Communications and Pulsed Radar (Lognormal Atmospheric Channel)... 

Commercial twystrons operate in the S-band (2.6-3.95 GHz) and C-band (3.95 5.85 GHz), and are used for pulsed radar transmitter power amphfiers. The pulsed peak output ranges from 1 to 7 MW with a pulse width of 10 50 /xs. This results in an average output power in the range of 1 28 k W with efficiency of 30-35%. The tube requires a beam voltage of 80-117 kV and a beam current of 45 150 A. The microwave input power to drive the ampHfier twystron is in a range of 0.3-3.0 kW (liao, 1988). 

One of the earliest pulse compression techniques was developed at the Bell Telephone Laboratories (Klauder et al, 1960 Rhodes, 1980). The technique was called CHIRP and employs frequency modulation. In a stepped modulation, each separate frequency would be transmitted for a time, which would correspond to a pulse length in a pulsed radar system. Upon reception, the separate frequencies are folded together to effectively form one pulse width containing the total energy transmitted. In a linear modulation, the frequency is continuous swept over abandwidthin a linear manner during the transmitted pulse length. 

In a time-of-flight pulsed radar system, the distance to the object is computed by observing the time difference between transmitted and received electromagnetic pulses. Range information can also be obtained by detecting the phase difference between... 

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