EP0713306A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
VCO-based frequency modulation system and method
Assignee: AT&T Inc
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Filing: 1995-11-06
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Granted: —
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Expires: 2015-11-06
Abstract
Abstract In a data modulating system the data stream (102) supplied to a modulating VCO (101) is filtered (in 108) before application to the VCO by increasing the low frequency gain of the data applied to the VCO. This increased gain counteracts a cancellation of low frequency data by the VCO because of diminished effectiveness of the VCO control signal due to low frequency data.
Inventors
- 👤 Syed M. Ahmed
- 👤 Sanjay Kumar
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 15:25
CPC Classifications
H; H03; H03C; H03C3/00; H03C3/02; H03C3/09; H03C3/0908; H03C3/0958; H04; H04L; H04L27/00; H04L27/10; H04L27/12; H03C2200/00; H03C2200/0037; H03C2200/005; H03C2200/0054
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
210 words
In a data modulating system for a cellular transmitter: a system comprising: a voltage controlled oscillator (VCO) having a control voltage input, a data input and a output for modulated data signals and a characteristic response to the control voltage in which a frequency deviation in its signal response drops sharply below a threshold frequency that is greater that a frequency of a portion of the data input; a reference frequency source; a frequency synthesizer connected to receive an output of the reference frequency source and the output of the VCO and the synthesizer having a frequency output; CHARACTERIZED BY: a low pass filter having an input connected to receive the frequency of the synthesizer and an output to provide a voltage to the control voltage input of the VCO; a data source terminal; a modulating data filter for interconnecting the data source terminal to the data input of the VCO; the modulating data filter having a gain frequency characteristic to counteract a control voltage response of the VCO that reduces frequency deviation of its output in response to a drop in data input with a curve shape of high gain of large frequency merging in a S shaped curve into a lower constant gain level above the threshold frequency.
Claim 2
Dependent Claim
26 words
In a data modulating system for a cellular transmitter as claimed in claim 1: a system comprising: wherein the modulating data filter is an active filter.
Claim 3
Dependent Claim
26 words
In a data modulating system for a cellular transmitter as claimed in claim 1: a system comprising: wherein the reference frequency source is a crystal oscillator.
Claim 4
Independent Claim
107 words
A method of modulating data applied to a voltage controlled oscillator (VCO) having a frequency response characteristic such that its signal response drop sharply below a threshold frequency permitting cancellation of low frequency data; including the steps of: accepting a stream of data at an input; CHARACTERIZED BY: filtering the data presented at the input with a filter function that adjusts the gain of signal through put such that low frequency signals below the frequency threshold are increased in gain and high frequency signals above the frequency threshold have a low gain relative to the increase in gain; applying the filted data to the voltage controlled oscillator.
Claim 5
Dependent Claim
37 words
A method of modulating data as claimed in claim 4, including the step of: generating a reference frequency in response to a crystal oscillator and applying the reference frequency through a low pass filter to the VCO.
Claim 6
Dependent Claim
44 words
A method of modulating data as claimed in claim 5, including the step of: using a filter function having a curve shape of high gain of large frequency merging in a S shaped curve into a lower constant gain level above the threshold frequency.
References Cited (Backward Citations)
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