Airborne Pulsed Doppler Radar

Presents the basic principles of pulse-doppler radar without resorting to a heavily mathematical treatment. High-, medium-, and low-pulse repetition frequency (PRF) modes are explained and the advantages and disadvantages of each are discussed. Also included are an explanation of the major signal-processing functions of doppler filtering, pulse compression, tracking, synthetic aperture, selection of medium PRFs, and resolving range ambiguities and a discussion of how to predict the performance of a pulse-doppler radar in the presence of noise and clutter. Annotation copyrighted by Book News, Inc., Portland, OR

The book is organized into three parts, each one building on the material of the previous sections. Part I (Chapters 1-8) covers the basic principles to lay sound foundations for the following parts of the book. It emphasizes classic processing techniques, especially the fast Fourier transform (FFT), and microwave engineering issues, antennas, and hardware. The second part of the book deals with the theory and techniques specific to pulse Doppler radar. This is subdivided into Part IIA (Chapters 9-10), which covers high PRF pulse Doppler, and Part IIB (Chapters 11-15), which covers medium PRF pulse Doppler. A major theme is that of PRF selection and optimization, other waveform design issues, and the problem of ghosting. While high and medium PRF pulse Doppler techniques have become synonymous with airborne fire control radars, they are used over a broad spectrum of airborne and surface-based radar applications. Part II does emphasize the airborne radar case, but it does not neglect the surface-based radar. Finally, Part III (Chapters 16-19) presents a series of four case studies. Each of these case studies applies the material of Part II whilst also highlighting additional radar techniques (and, in some cases, non-radar considerations) specific to the application. Such is the prevalence of pulse Doppler radars today; the number of case studies that could have been considered is well into double figures. However, the four presented here suffice to illustrate the wide variety of pulse Doppler radar applications.

Ground clutter interference is a major problem for airborne pulse Doppler radar operating at low altitudes in a look-down mode. With Doppler zero set at the aircraft ground speed, ground clutter rejection filtering is typically accomplished using a high-pass filter with real valued coefficients and a stopband notch centered at zero Doppler. Clutter spectra from the NASA Wind Shear Flight Experiments of l991-1992 show that the dominant clutter mode can be located away from zero Doppler, particularly at short ranges dominated by sidelobe returns. Use of digital notch filters with complex valued coefficients so that the stopband notch can be located at any Doppler frequency is investigated. Several clutter mode tracking algorithms are considered to estimate the Doppler frequency location of the dominant clutter mode. From the examination of night data, when a dominant clutter mode away from zero Doppler is present, complex filtering is able to significantly increase clutter rejection over use of a notch filter centered at zero Doppler. Jamora, Dennis A. Unspecified Center...

High resolution windspeed profile measurements are needed to provide reliable detection of hazardous low altitude windshear with an airborne pulse Doppler radar. The system phase noise in a Doppler weather radar may degrade the spectrum moment estimation quality and the clutter cancellation capability which are important in windshear detection. Also the bias due to weather return Doppler spectrum skewness may cause large errors in pulse pair spectral parameter estimates. These effects are analyzed for the improvement of an airborne Doppler weather radar signal processing design. A method is presented for the direct measurement of windspeed gradient using low pulse repetition frequency (PRF) radar. This spatial gradient is essential in obtaining the windshear hazard index. As an alternative, the modified Prony method is suggested as a spectrum mode estimator for both the clutter and weather signal. Estimation of Doppler spectrum modes may provide the desired windshear hazard information without the need of any preliminary processing requirement such as clutter filtering. The results obtained by processing a NASA simulation model output support consideration of mode identification as one component of a windshear detection algorithm. Lee, Jonggil Unspecified Center AIRBORNE EQUIPMENT; DETECTION; HAZARDS; METEOROLOGICAL RADAR; PULSE DOPPLER RADAR; SIGNAL PROCESSING; STATISTICAL ANALYSIS; WEATHER; WIND SHEAR; WIND VELOCITY; ALGORITHMS; CLUTTER; ERRORS; ESTIMATES; ESTIMATING; HIGH RESOLUTION; LOW ALTITUDE; LOW FREQUENCIES; SIMULATION; SPECTRA...

An introduction to the subject for non-specialists: engineers, technicians, pilots, and aerospace industry marketing, public relations, and customer support personnel. Also a reference for specialists in the field. The completely rewritten and revised Second Edition updates the original published by the Hughes Aircraft Company.

Intended for actual users of radar, the book focuses on the history, main principles, functions, modes, properties and specific nature of modern airborne radar. It examines radar's role within the system when carrying out its assigned missions, showing the possibilities of radar, it's limitations and a discussion of how radar may evolve in the future.