A new radar technique has been developed that provides a solution for the conflicting requirements of simultaneous long-range and high-resolution performance in radar systems. This technique, called Chirp at Bell Telephone Laboratories, recognizes that resolution depends on the transmitted pulse bandwidth. A long high-duty-factor transmitted pulse, with suitable modulation (linear frequency modulation in the case of Chirp), which covers a frequency interval many times the inherent bandwidth of the envelope, is employed. The receiver is designed to make optimum use of the additional signal bandwidth. This paper contains many of the important analytical methods required for the design of a Chirp radar system. The details of two signal generation methods are considered and the resulting signal waveforms and power spectra are calculated. The required receiver characteristics are derived and the receiver output waveforms are presented. The time-bandwidth product is introduced and related to the effective increase in the performance of Chirp systems. The concept of a matched filler is presented and used as a reference standard in receiver design. The effect of amplitude and phase distortion is analyzed by the method of paired echoes. One consequence of the signal design is the presence of time side lobes on the receiver output pulse analogous to the spatial side lobes in antenna theory. A method to reduce the time side lobes by weighting the pulse energy spectrum is explained in terms of paired echoes. The weighting process is described, and calculated pulse envelopes, weighting network characteristics and deleterious effects are presented. The effects of quadratic phase distortion are analyzed and the resultant pulse envelopes are presented. The receiver response characteristics in the presence of Doppler-shifted signals from moving targets are examined. Schematic ambiguity diagrams are presented for current signal designs.
Artículo donde aparece por primera vez la palabra "Chirp" y en este caso aplicado a los sistemas Radar. Los dispositivos "Chirp" son ejemplos de filtros adaptados (matched filters) diseñados para detectar señales moduladas en frecuencia con características particulares como en el caso del Radar, pero también fueron importantes como base para filtros SAW y transformadores de Fourier analógicos en el campo de las comunicaciones civiles.
- Autor/es: J.R.Klauder; A.C.Price; S.Darlington; W.J.Albersheim.
- Fecha: 1960-07
- Publicado en: The Bell System Technical Journal (Volume: 39, Issue: 4, July 1960, Pages: 745-808.
- Idioma: Inglés
- Formato: PDF
- Contribución: José Antonio Delgado-Penín.
- Palabras clave: Geociencia y teledetección, Proceso de señal, Sistemas electrónicos aeroespaciales