EP0151916A2
Expired / Lapsed
EP
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Automatic gain control circuit
Assignee: Fujitsu Ltd
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Filing: 1985-01-02
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Granted: —
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Expires: 2005-01-02
Abstract
Abstract An automatic gain control (AGC) circuit comprising a first filter (33) to which a received signal (S R ) is applied, a variable level adjusting means (34), connected therewith, for producing the automatic gain controlled signal. A feedback loop is set up between the input and output of the variable level adjusting means (34), which feedback loop contains therein a second filter (51) exhibiting a narrower equivalent noise band width than that of the first filter (33), in response to a-particular signal component having a predetermined frequency spectrum with a certain duration so as to perform an integration in the second-filter (5).
Inventors
- 👤 Tokihiro Mezon Hisasue 503 473-4 Miyo
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 08:17
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3052; H03G3/3078; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/204; H04B7/212; H04L; H04L27/00; H04L27/02; H04L27/08
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
223 words
An automatic gain control (AGC) circuit, comprising: a band pass filter (33) receivina a received signal (S R ) and allowing desired frequency spectrum components thereof to pass therethrough; a variable level adjusting means (34) for effecting an automatic level control for the filtered output signal given from said band pass filter (33) and producing a level adjusted output signal as an automatic gain controlled signal; and a detector (36) for detecting the output signal produced from said variable, level adjusting means (34) and applying the detected output signal therefrom to a control input of said variable level adjusting means, characterized in that a filter (51) other than said band pass filter (33) is further incorporated in the AGC circuit, this filter being responsive only to a particular signal component having a predetermined frequency spectrum with a certain duration, included in said desired frequency spectrum components, and thus the filter (51) performs an integration for the particular signal component, and thereby produces a filtered output exhibiting an equivalent noise band width (N bw ), at the end of said certain duration, which is narrower than that of said band pass filter (33), and the filtered output with the thus narrowed equivalent noise band width is supplied, via said detector ( 36 ), to the control input of said variable level adjusting means (34).
Claim 2
Dependent Claim
223 words
An automatic gain control (AGC) circuit, comprising: a band pass filter (33) receivina a received signal (S R ) and allowing desired frequency spectrum components thereof to pass therethrough; a variable level adjusting means (34) for effecting an automatic level control for the filtered output signal given from said band pass filter (33) and producing a level adjusted output signal as an automatic gain controlled signal; and a detector (36) for detecting the output signal produced from said variable, level adjusting means (34) and applying the detected output signal therefrom to a control input of said variable level adjusting means, characterized in that a filter (51) other than said band pass filter (33) is further incorporated in the AGC circuit, this filter being responsive only to a particular signal component having a predetermined frequency spectrum with a certain duration, included in said desired frequency spectrum components, and thus the filter (51) performs an integration for the particular signal component, and thereby produces a filtered output exhibiting an equivalent noise band width (N bw ), at the end of said certain duration, which is narrower than that of said band pass filter (33), and the filtered output with the thus narrowed equivalent noise band width is supplied, via said detector ( 36 ), to the control input of said variable level adjusting means (34).
Claim 3
Dependent Claim
62 words
An AGC circuit as set forth in claim 1, wherein a peak holding means(37) is further incorporated therein between the output of said detector(36) and the control input of said variable level adjusting means (34), the peak holding means (37) detecting the peak value, appearing at the end of said certain duration, of said filtered output with the narrowed equivalent noise bandwidth.
Claim 4
Dependent Claim
22 words
An AGC circuit as set forth in claim 2, wherein said peak holding means (37) is made of a peak holding circuit.
Claim 5
Dependent Claim
19 words
An AGC circuit as set forth in claim 2, wherein said filter (51) is made of a narrow-band filter.
Claim 6
Dependent Claim
41 words
An AGC circuit as set forth in claim 4, wherein said narrow-band filter is responsive to a non-modulated short duration carrier signal, as said particular signal component, having a carrier frequency, which carrier signal is used for carrying said received signal.
Claim 7
Dependent Claim
34 words
An AGC circuit as set forth in claim 5, wherein said non-modulated carrier signal is obtained, under a time division multiple access (TDMA) mode, as a CR part contained in each TDMA burst signal.
Claim 8
Dependent Claim
67 words
An AGC circuit as set forth in claim 5, wherein said peak holding means (37) is realized as a samole and hold circuit for sampling the output from said detector every time a sampling control signal is given thereto and holding the thus sampled signal, in which the sampling control signal is created in response to a timing indicative of the end portion of said certain duration.
Claim 9
Dependent Claim
55 words
An AGC circuit as set forth in claim 7, wherein said sampling control signal is given from a voltage comparator receiving,,at its first input, the output from said detector and, at its second input, a threshold voltage which is so determined as to detect the peak side level of the output from said detector (36).
Claim 10
Dependent Claim
29 words
An AGC circuit as set forth in claim 7, wherein said sampling control signal is realized as a timing signal indicative of the end portion of said certain duration.'
Claim 11
Dependent Claim
46 words
An AGC circuit as set forth in claim 9, wherein said non-modulated carrier signal is obtained, under a time division multiple access (TDMA) mode, as a CR part contained in each TDMA burst signal, and said timing signal is given from a TDMA synchronization control unit.
Claim 12
Dependent Claim
64 words
An AGC circuit as set forth in claim 7, wherein said sampling control signal is given by way of a selector (141),the selector initially producing a first sampling control signal indicative of the peak side level of the output from said detector and then producing a second sampling control signal composed of a timing signal indicative of the end portion of said certain duration.
Claim 13
Dependent Claim
94 words
An AGC circuit as set forth in claim 11, wherein said first sampling control signal is given from a voltage comparator receiving, at its first input, the output from said detector and, at its second input, a threshold voltage which is so determined as to detect the peak side level of the output from said detector; and said second sampling control signal is given from a time division multiple access (TDMA) synchronization unit, in which a non-modulated carrier signal is obtained, under the TDMA mode, as a CR part contained in each TDMA.burst signal.
Claim 14
Dependent Claim
23 words
An AGC circuit as set forth in claim 1, wherein said variable level adjusting means is fabricated as a variable gain amplifier (34).
Claim 15
Dependent Claim
22 words
An AGC circuit as set forth in claim 1 wherein said variable level adjusting means is fabricated as a variable voltage attenuator.
Claim 16
Dependent Claim
92 words
An AGC circuit as set forth in claim 4, wherein said narrow-band filter is comprised of a first capacitor (91), a second capacitor (92), a third capacitor (93), and a coil (94), the first and second capacitors (91,92)-are connected in series between the input and the output of the narrow-band pass filter, and the third capacitor (93) and the coil (94) are connected in parallel, one end of which parallel circuit is grounded and the other end of which is connected to the intermediate connecting point between the first and second capacitors.
References Cited (Backward Citations)
No citation records indexed.
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