Analog communication system

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. 

Fig. 7.15. A three-frequency nonlinear heterodyne analog communications system...

Couch, L.W., II. 1993. Digital and Analog Communication Systems, 4th ed. Macmillan, New York, now Prentice-Hall, Englewood Cliffs, NJ. 

Lathi, B. P. 1989. Modern Digital and Analog Communication Systems, 2nd ed. Holt, Rinehart, and Wieston, Orlando, FL. 

Shanmugam, K.S. 1979. Digital and Analog Communication Systems. Wiley, New York. 

The RF output signal of the channel encoder is ampHfied to the appropriate power level for transmission. Because the carrier-to-noise (C/N) ratio of the modulated waveform is not generally so critical as that required for analog communications systems, relatively low transmission power often can be used. Depending on the sophistication of the data recovery circuits contained in the DAB receiver, the use of C/N ratios as low as 6 dB are possible without causing a degradation to the received signal. 

From Dorf, R.C. and Wan, Z., Modulation and demodulation, in The Electrical Engineering Handbook, 2nd ed., Dorf, R.C., Ed., CRC Press, Boca Raton, FL, 1998, p. 1505. Orignally from L. W. Couch, Digital and Analog Communication Systems, New York Macmillan, 1990. With permission. 

The isolated boar ketones, 5a-androst-16-en-3a-ol (androstenol) and androst-16-en-3-one (androstenone) secreted by the sub-maxillary gland, have a direct effect on the sexual receptivity of the sow and are used commercially to assist in artificial insemination (14). The fact that estrus can be determined in the sow by her response to these compounds suggests that there is a heightened acuity for these compounds at the time of ovulation. This is similar to the increase in olfactory acuity for certain compounds noted in human females prior to ovulation (15). A somewhat unique but analogous situation is the elephant temporal gland which is an apocrine gland that is active under stress and possesses an elephanty odor (16). Table III summarizes some of the mammalian communication systems that have been studied and the chemicals which have been found to have behavioral effects. 

Aircraft and aerospace electronics Analog instrumentation Automotive electronics Business machines Communication systems... 

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. 

Roden, M.S. 1991. Analog and Digital Communication Systems, 3rd ed. Prentice-HaU, Englewood Cliffs, NJ. 

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