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    Improving the noise performance of communication systems: radio and telephony developments of the 1920s [History of Communications]

    Schwartz, M.
    Communications Magazine, IEEE

    Volume: 47 , Issue: 12
    DOI: 10.1109/MCOM.2009.5350362
    Publication Year: 2009 , Page(s): 16 - 20
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    This article discusses the early pioneering work of both telephone and radio engineers in effecting improvements in the noise performance of communication systems. This work led ultimately to the explosive growth of communication activities following World War II. Radio engineers during the 1920s were most concerned with reducing the impact of externally generated "static," and showed this could be accomplished by the use of directional antennas and moving to higher-frequency transmission. Telephone engineers during that period of time, most prominently John R. Carson of AT&T, were led to include the impact of "fluctuation noise" (shot and thermal noise) as well. Carson, using the then novel concept of noise frequency spectrum, showed how the appropriate choice of bandwidth and frequency of transmission could be used to improve the signal-to-noise ratio, anticipating the concept of a "matched filter" introduced 20 years later during radar developments of World War II. This early work on improving the noise performance of communication systems led, in the early 1930s, to Edwin H. Armstrong's spectacular leap ahead with his invention of wide-deviation low-noise frequency modulation (FM), followed a few years later by the invention by Alec Reeves of pulse code modulation (PCM), the first low-noise digital communication system of the modern era. View full abstract»

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    Improving the noise performance of communication systems: 1930s to early 1940s

    Schwartz, M.
    History of Telecommunications Conference, 2008. HISTELCON 2008. IEEE

    DOI: 10.1109/HISTELCON.2008.4668718
    Publication Year: 2008 , Page(s): 72 - 78

    IEEE Conference Publications

    This work came directly out of work done during the War on radar and control systems. Yet the radar work itself was an outgrowth of work beginning circa 1920 on improving the performance of communication systems in the presence of noise. We have previously reported on work carried out in this area during the 1920s in both radio (wireless) communications and wired telephony [1]. In this paper we focus on work done in the 1930s and early 1940s, which both enlarged on, and saw considerable strides ahead in, these earlier studies involving noise in communication systems. We do this by presenting developments during this period of time in three inter-related, and roughly chronological, areas: 1. Work by Armstrong on FM and Reeves on PCM showing, for the first time, that noise could be reduced by purposefully increasing the bandwidth (now known as the noise-bandwidth tradeoff). This work is discussed in the next section covering the period of the 1930s. 2. Studies attempting to understand the statistical properties of noise, leading to its now-well-known Gaussian amplitude characteristic. This work is described in the section covering the late 1930s to early 1940s. 3. The recognition that ldquomatched filteringrdquo provided optimum signal detection in noise. This work, described in the last section of this paper, arose out of the need during World War II to detect small, pulsed, radar signals in the presence of noise. View full abstract»

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