EP0435455A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Varying bandwidth digital signal detector

Assignee: AT&T Inc

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Filing: 1990-11-23

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Granted: —

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Expires: 2010-11-23

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Abstract

Abstract A digital communication system has a plurality of channels with distinct carrier frequencies and overlapping bands. Each receiver includes a filter (405) having a time varying bandwidth. The received signal includes at least one carrier modulated by an information signal having a plurality of levels and transitions between the levels at predetermined intervals and components due to other channels. The receiver is synchronized to a selected one of the carriers. The received signal is translated to baseband and applied to the time varying filter (405) which is set to a first bandwidth at the information signal transitions and reduced in the intervals between transitions. The first filter bandwidth accommodates the information signal transitions. Reducing the bandwidth between transitions limits interference components in the time varying filter output when the the information signal level is sampled. The technique may be applied to various modulation schemes.

Inventors

👤 Robert Evan Myer

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-05 00:37

CPC Classifications

H; H03; H03G; H03G5/00; H03G5/16; H03G5/24; H04; H04B; H04B1/00; H04B1/06; H04B1/10; H04B1/1027; H04B1/16; H04B1/1638; H04B2001/1054

Claims Analysis

Total Claims: 6

Claim 1

Independent Claim 142 words

. A communication receiver comprising: means for receiving a modulated RF signal including at least one carrier signal modulated by a first information signal, the first information signal having a plurality of levels and transitions between the levels occurring at predetermined intervals, means responsive to the received modulated RE signal for forming a demodulated signal including a component corresponding to the first information signal, and CHARACTERIZED BY: means for detecting the levels of the demodulated signal between the transitions of the first information signal, the detecting means includes: means for limiting the demodulated signal to a first bandwidth at the transition instants of the first information signal and to a second narrower bandwidth between the transitions of the first information signal, and means for sampling the demodulated signal from the bandwidth limiting means during the second narrower bandwidth of the demodulated signal.

Claim 2

Dependent Claim 59 words

. A communication receiver according to claim 1 wherein the demodulated signal limiting means FURTHER CHARACTERIZED BY: filter means having a controllable variable bandwidth, and means for adjusting the bandwidth of the filter means to the first bandwidth at transitions of the first information signal and to the second narrower bandwidth between the transitions of the first information signal.

Claim 3

Dependent Claim 74 words

. A communication receiver according to claim 2 FURTHER CHARACTERIZED BY: the filter means having a controllable variable bandwidth comprises a filter including at least one resistive charging source for determining the bandpass of the filter, and the filter bandwidth adjusting means comprises means for adjusting the resistive charging source to a first value at the transitions of the first information signal and to a second value between transition of the first information signal.

Claim 4

Dependent Claim 56 words

. A communication receiver according to claim 3 FURTHER CHARACTERIZED BY; the resistive charging source comprises a switched capacitor element and means for clocking the switched capacitor element, and the means for adjusting the resistive charging source comprises means for varying the frequency of the switched capacitor element clocking means to adjust the resistive charging source.

Claim 5

Dependent Claim 80 words

. A communication receiver according to claim 4 FURTHER CHARACTERIZED BY: means responsive to each transition of the first information signal for producing a frequency control signal having an initial value at each transition and decreasing to a second value just prior to the next transition of the first information signal, and the means for clocking the switched capacitor element comprises a voltage controlled oscillator responsive to the frequency control signal for varying the frequency of the voltage controlled oscillator.

Claim 6

Dependent Claim 21 words

. A communication receiver according to claims 1,2,3,4 or 5 FURTHER CHARACTERIZED IN THAT the demodulated signal is a baseband signal.

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