IMPROVEMENTS IN OR RELATING TO RADIO RECEIVERS
First Claim
1. A radio receiver comprising:
- an analogue-to-digital converter;
a frequency divider for providing a sampling clock frequency (fS) for the analogue-to-digital converter for determining the strength of an output signal from the analogue-to-digital converter; and
device for altering a frequency dividing ratio of the frequency divider in response to the determined strength of the said output signal in order to vary the gain of the analogue-to-digital converter.
11 Assignments
0 Petitions
Accused Products
Abstract
A radio receiver comprises an input (14) for a modulated radio frequency signal, a frequency down converter (16) coupled to the input, the frequency down converter including quadrature mixers (32, 34) for demodulating a received modulated radio frequency signal using a local oscillator signal. An analogue-to-digital converter (54, 56) is coupled to receive demodulated signals from the mixing means. The analogue-to-digital converter, which may comprise a continuous time sigma delta converter, has an input for a sampling clock frequency (f s). A voltage controlled oscillator (38) provides the local oscillator signal and supplies a frequency divider (60, 94) used to provide the sampling clock frequency. The dividing ratio (1/A) of the frequency divider is variable in response to variations in the strength of an 15 output signal from the digital-to-frequency converter and the variations in the frequency of the sampling clock frequency vary the gain of the analogue-to-frequency converter thereby providing automatic gain control.
71 Citations
10 Claims
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1. A radio receiver comprising:
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an analogue-to-digital converter; a frequency divider for providing a sampling clock frequency (fS) for the analogue-to-digital converter for determining the strength of an output signal from the analogue-to-digital converter; and device for altering a frequency dividing ratio of the frequency divider in response to the determined strength of the said output signal in order to vary the gain of the analogue-to-digital converter. - View Dependent Claims (3, 4, 8, 9)
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2. A radio receiver comprising:
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an input for a modulated radio frequency signal; a frequency down converter coupled to the input, the frequency down converter including a mixer for demodulating a received modulated radio frequency signal using a local oscillator signal; an analogue-to-digital converter coupled to receive a demodulated signal from the mixer, the analogue-to-digital converter having an input for a sampling clock frequency (fS); a voltage controlled oscillator coupled to the frequency down converter for providing the local oscillator signal; and a frequency divider coupled to the voltage controlled oscillator for providing the sampling clock frequency, wherein a digital-to-frequency converter provides a sampling clock frequency control signal (fS control) according to a strength of a digital output signal from the analogue-to-digital converter, and in that the frequency divider is responsive to the sampling frequency control signal to vary a frequency dividing ratio (1/A) of the frequency divider. - View Dependent Claims (5, 6)
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7. A radio receiver as claimed in 5, characterised in that a received signal strength indicating stage is coupled to the output of the quantiser for producing digitised signal strength signals, and in that the digital-to-frequency conversion means comprises a look-up table storing sampling frequency control values to vary the dividing ratio of the frequency divider in response to the digitised signal strength control signals obtained from the received signal strength indicating stage.
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10. A method of operating a radio receiver, the method comprising:
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demodulating a received radio signal to obtain demodulated signals; filtering the demodulated signals; digitising the filtered signals in analogue-to-digital converter; and altering a gain of the analogue-to-digital converter by varying a sampling clock frequency (fS) of the analogue-to-digital converter in accordance with a strength of a signal derived from the analogue-to-digital converter.
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Specification