SCR-270 radar development

The development of the SCR-270-271 series of radars is traced. These radar had their origin in the work that preceded and eventually culminated in the first US Army radar: Search Light Control Radar SCR-268. The principal technical characteristics of the 270-271 series are summarized and given in tabular form     

Comments on `Comparison of two-sensor tracking methods based onstate vector fusion and measurement fusion' by J. Roecker et al

As shown in the above named work (ibid., vol.24, p.447-9, July, 1988), the improvement in the centralized scheme over the decentralized one was shown to be about 6-8%. The reason is briefly described     

Comments, with reply, on `Optimal detection and performance ofdistributed sensor systems'

The commenter observes that the general solution proposed in the above paper (see ibid., vol.AES-23, no.1, p.24-30, Jan. 1988) for the global optimization of a distributed sensor detection system with fusion leads to coupled equations whose solution is a formidable computational task. This necessitated several simplifying assumptions that he comments on here. In response, the authors review the extent of the equal local threshold assumption throughout the work and make comments on the numerical performance comparison they gave there     

The untold Pearl Harbor radar story

Ever wonder what happened to the radar set that detected the Japanese aircraft before the raid on Pearl Harbor? This article reveals the fate of that SCR-270 radar set; describes some of the radar development background; and includes typical results of a World War II command, control and communications system that used the SCR-270 as its backbone radar. The SCR-270 was a radio-echo detection and direction finding set for locating aircraft. It operated by transmitting a short-duration pulse of high frequency radio waves, which would be reflected or re-radiated by any metallic or conducting surface within the field of the directive transmitting antenna; therefore, one or more aircraft within the antenna field appeared as a source of reflected radio waves. Rotating the antenna which also served as the receiving antenna, provided a means for determining the azimuth or direction of aircraft. The system measured the time it took a blip or reflected return from the target to appear on a cathode ray tube indicator, to give the distance or range to the detected aircraft. The maximum range of the radar was about 250 miles up to 50,000 feet under all atmospheric conditions including rain, mist, smoke or fog, and during daylight or darkness. The azimuth and range data supplied by the set permitted the plotting of the location of detected aircraft on maps. Major performance characteristics of the radar are provided in the included table     

Ambiguity function of quadriphase coded radar pulse

Taylor's quadriphase coding (J.W. Taylor, Jr. and H.J. Blinchikoff, ibid., vol.23, no.2, p.156-70, Mar. 1988) is investigated for nonzero Doppler shifts. While the zero-Doppler cut of the ambiguity function (i.e. the autocorrelation) strongly resembles that of the corresponding biphase code, the remaining ambiguity function differs considerably. The ambiguity function of quadriphase code 13 is typified by a diagonal ridge as found in linear FM signals. The ambiguity function of quadriphase code 28A resembles the three parallel ridges of Frank code 16     

The SCR-270 in Japan

The deficient state of the radar in use when the war in Korea erupted in 1950 is described. The installation of the SCR-270 radar system is discussed, and its siting is considered. Test and performance results are examined     

Comments on, `Improved multilevel quantization for detection ofnarrowband signals' by C.W. Helstrom

It is shown that optimum quantization levels may be obtained by using C.W. Helstrom's approach of the above named work (see ibid., vol.AES-24, p.141-147, Mar. 1988) but maximizing exact detection probabilities instead of approximations to it if the moment generating function of the test statistic can be expressed in rational form. Adaptive levels may be obtained for the quantizers by cell averaging, leading to constant false alarm rate (CFAR) detectors     

Comment on “A new approach to robust fault detection andidentification”

In the paper by M. Saif and Y. Guan (see ibid., vol. 3, no 29, p. 685-695), a necessary and sufficient condition is given for the existence of an asymptotically stable observer in the case of p=m. The objective of this note is to point out a critical mistake in the main theorem of the paper     

Comments on `SCR 584 radar and Mk.56 gunfire control' by I. Getting

Some errors in the above-titled article (see ibid., vol.5, no.10, p.3-15, Oct. 1990) are pointed out. Although the material is peripheral to the principal subject, the commenter feels that they are significant to the article if taken as historical     

Comments on `Existence and uniqueness of GPS solutions' by J.S.Abel and J.W. Chaffee

The commenter points out that a direct Global Positioning System (GPS) algorithm together with discussions on the existence and uniqueness of the solution appeared in his paper (J. Guidance, Control, and Dynamics, vol.9, p.715-17, Nov./Dec. 1986). Since the GPS solution is reduced to solving a quadratic equation, the existence and uniqueness can be easily tested. J.S. Abel and J.W. Chaffee, in the above-titled paper (ibid., vol.26, no.6, p.748-53, Sept. 1990), show that the GPS solution problem is similar to the hyperbolic-fix problem. The commenter notes that it can be inferred from his later work (ibid., vol.26. no.5, p.748-53, Sept. 1990) that the two solutions exist if and only if the four GPS satellites are coplanar, in which case the two solutions are mirror-symmetric with respect to the GPS plane     

Comments with reply, on `A new look at nonseparable syntheticaperture radar processing' by A. Di Cenzo

The commenters point out that the idea using a two-dimensional digital correlation technique to perform synthetic-aperture-radar (SAR) processing, presented as new in the above-titled paper (see ibid., vol.24, p.218-23, May 1988), was described by them as early as 1978 and has since been described by other authors. They discuss some of these earlier studies. The author replies that he was unaware of the earlier work, and that he did not intend to convey the impression that the nonseparable transform domain processor that he presented was the first     

Comments on "Unbiased converted measurements for tracking"

We show that there exists a compatibility problem in the derivation of the mean and covariance of the converted measurement errors in L. Mo et al. (ibid., vol.34, no.3, p.1023-7, 1998), and then present a modification to the computation of them, in which both the mean and the covariance are computed strictly conditioned on the measurements.     

Comments, with reply, on `Status of CR-like lower bounds fornonlinear filtering' by T.H. Kerr

The commenters object to criticisms of their work that appeared in the above-titled paper (ibid., vol.25, no.5, p.590-601, Sept. 1989) and provide a defense of their results. The author presents further arguments to buttress his claims     

Comments on `Tracking a maneuvering target using input estimation''

P.L. Boglar (see ibid., vol.AES-23, no.3, p.298-310, May 1987) developed a recursive formulation of the Chan, Hu, and Plant (CHP) algorithm, and the results of the simulation verified the performance improvements. The commenter claims that Bogler obtained an incorrect recursive formulation of input estimation because he incorrectly used the formulation of the Kalman filter. The commenter presents calculations that aim to demonstrate this claim     

Possible ultra-wideband radar terminology

This is a supplement to the terms proposed by Malek G.M. Hussain and James D. Taylor (see ibid., vol.19, no.7, p.39, July 2004).     

Current distribution control for parallel connected converters. I

For pt.II, see ibid., vol.28, no.3, p.841-851 (1992). A master-slave control scheme for a uniform current distribution among converter modules in a parallel connected system is presented. In this technique, inner current loops are introduced to the system to achieve output current equalization. The current distribution error is used as a criterion for judging system performance. Using this control scheme, the current distribution error can be reduced greatly even with nonidentical converters in the system. To optimize system efficiency and facilitate the fault-tolerant algorithm realization, this technique is refined so that only the necessary number of converters are activated for different load conditions     

Comments on 'Mismatched filter design for periodical binary phased signals' by H. Rohling and W. Plagge

The commenter states that the filters described in the above-mentioned paper by H. Rohling and W. Plagge (see ibid., vol.26, no.6, p.890-6, Nov. 1989) were described in general terms in his articles from 1977-8. The families of binary sequences with minimal or small loss-factors were described by the commenter in earlier publications (1980, 1987). Comparison of the data from these papers and from those of the authors shows that sequences with length 21 and 28 are not optimal.<>     

Observability analysis of piece-wise constant systems. I. Theory

For pt.II see ibid., vol.28, no.4, p.1068-75, Oct. 1992. A method for analyzing the observability of time-varying linear systems which can be modeled as piece-wise constant systems (PWCS) is presented. An observability matrix for such systems is developed for continuous and discrete time representations. A stripped observability matrix (SOM) is introduced which simplifies the analysis in cases where the use of this matrix is legitimate. The observability analysis is presented as a step-by-step procedure     

Current distribution control for parallel connected converters. II

For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given     

A tracking approach for targets with measurements containingjamming or clutter signals

The concept of maneuvering target tracking which is presented by K. Demirbas, (see ibid., vol.AES-23, p.757-66, 1987) is used to track maneuvering targets whose observations contain interference representing jamming or clutter signals. The resulting tracking approach produces state estimates that closely follow the actual state values, as in target tracking in a clear environment