EP0507401A2
Expired / Lapsed
EP
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Frequency tracking arrangement, corresponding method of frequency tracking and a radio receiver embodying such an arrangement
Assignee: Philips Electronics UK Ltd
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Filing: 1992-03-30
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Granted: —
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Expires: 2012-03-30
Abstract
Abstract A frequency tracking arrangement comprises an input (30) to a frequency translation means (32) whose output is coupled to a filter and demodulator (34) which has both frequency (36), and amplitude (38) outputs. The frequency output is fed via a low pass filter (42) to a variable gain stage (44). The output of the gain stage (44) is fed to a feedback input of the frequency translation means (32). The amplitude output (38) of the filter and demodulator is fed to a control input of the variable gain stage (44). The amplitude output of the filter and demodulator is used to vary the amplitude of the feedback signal in the frequency tracking loop. When the arrangement is used in an FM radio receiver for audio, as the input signal weakens the frequency translation means (32) stops attempting to track the incoming signal. The subjective effect is that as the output signal amplitude diminishes relative to the noise, the receiver is less likely to search adjacent frequency bands and lock on to unwanted signals.
Inventors
- 👤 Paul Bucknell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 20:59
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
96 words
A frequency tracking arrangement comprising a frequency translation means for converting an incoming signal to a frequency converted signal in response to a feedback signal, a demodulating means for demodulating the frequency converted signal to provide a frequency output signal and an amplitude output signal, and a feedback path comprising a filtering means and a variable gain means for filtering and varying the amplitude of the frequency output signal to provide the feedback signal to the frequency translation means, the gain of the variable gain means being responsive to the amplitude output of the demodulating means.
Claim 2
Dependent Claim
16 words
An arrangement as claimed in Claim 1, wherein the frequency translation means includes a digital memory.
Claim 3
Dependent Claim
18 words
An arrangement as claimed in Claim 1 or Claim 2, wherein the demodulator includes a CORDIC phase detector.
Claim 4
Dependent Claim
45 words
An arrangement as claimed in any one of the Claims 1 to 3, wherein the variable gain means includes an amplitude scaling means for providing a predetermined relationship between the amplitude output signal of the demodulating means and the gain of the variable gain means.
Claim 5
Dependent Claim
53 words
An arrangement as claimed in Claim 4, wherein the predetermined relationship is such as to provide a gain which increases with increasing amplitude at the amplitude output of the demodulating means while that amplitude output is below a threshold level and is substantially constant while that amplitude output is above the threshold level.
Claim 6
Independent Claim
72 words
A method of tracking frequency variations in an incoming signal, which method comprises frequency translating the incoming signal in accordance with a feedback signal to provide a frequency translated signal, demodulating the frequency translated signal to provide a frequency output signal and an amplitude output signal, and scaling the amplitude of the frequency output signal by a function of the amplitude output signal to provide the feedback signal for the frequency translation.
Claim 7
Dependent Claim
116 words
A radio receiver comprising a radio frequency (R.F.) stage for receiving and down converting a frequency modulated signal to an intermediate frequency (I.F.) signal, a frequency translation means for providing a frequency translated signal in response to the I.F. signal and a feedback signal, a demodulating means for providing at least a frequency output signal and an amplitude output signal in response to the frequency translated signal and a signal feedback path comprising filtering means and variable gain means for filtering and varying the amplitude of the frequency output signal to provide the feedback signal, the variable gain means being arranged to vary the amplitude of the feedback signal in response to the amplitude output signal.
Claim 8
Dependent Claim
115 words
A radio receiver comprising a radio frequency (R.F.) stage for receiving and down converting a frequency modulated signal to an intermediate frequency (I.F.) signal in response to a feedback signal, a frequency translation means for translating the I.F. signal to a frequency translated signal, a demodulating means for providing at least a frequency output signal and an amplitude output signal in response to the frequency translated signal, a signal feedback path comprising filtering means and variable gain means for filtering and varying the amplitude of the frequency output signal to provide the feedback signal, the variable gain means being arranged to vary the amplitude of the feedback signal in response to the amplitude output signal.
Claim 9
Dependent Claim
43 words
A radio receiver as claimed in Claim 7 or Claim 8, wherein the variable gain means includes an amplitude scaling means for providing a predetermined relationship between the amplitude output signal from the demodulating means and the gain of the variable gain means.
Claim 10
Dependent Claim
56 words
A radio receiver as claimed in Claim 9, wherein the predetermined relationship is such as to provide a gain which increases with increasing amplitude of the amplitude output signal from the demodulating means while that amplitude output is below a threshold level and is substantially constant while that amplitude output signal is above the threshold level.
References Cited (Backward Citations)
No citation records indexed.
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