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 filter 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.

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This paper bears on the problem of splitting a signal into two parts of like amplitudes but different phases. Constant phase differences are utilized in such circuits as Hartley single sideband modulators. The networks considered here are pairs of constant‐resistance phase‐shifting networks connected in parallel at one end. The first part of the paper shows how to compute the best approximation to a constant phase difference obtainable over a prescribed frequency range with a network of prescribed complexity. The latter part shows how to design networks producing the best approximation.

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Some theoretical aspects of the demodulation of wideband, low‐power FM signals are discussed. It is assumed that a band‐limited, continuous, analog signal is supplied to the modulator and is recovered to a fidelity suitable for television, telephone, or carrier telephone. Much of the paper assumes that the baseband signal is sampled and clamped before it is applied to the frequency modulator. The combination has been called PAM‐FM and is characterized by a piecewise constant transmitted frequency. PAM‐FM can be demodulated by spectrum analysis means not suitable for continuously varying frequencies. It is shown that a spectrum generator can be derived from the techniques of radar pulse compression, and is equivalent to an infinite set of correlators or matched filters plus means for scanning their terminals. The spectrum analysis circuit forms are compared with demodulators using frequency detectors, with and without FM feedback, in regard to theoretical noise sensitivities. The theoretical sensitivities are quite similar for spectrum analysis and FMFB under conditions assumed. The comparisons disclose that frequency detectors (followed by filters) enjoy a disguised but efficient use of a differential phase coherence which is a characteristic of FM signals. A combination of spectrum analysis and frequency detection is described which has some of the theoretical advantages of both.