Communication system with control signal based tuning
First Claim
1. A radio communications system comprising:
- a) a radio base station for transmitting a control channel signal and a plurality of traffic channel signals separated in frequency from said control channel signal; and
b) a radio communications device, receptive and responsive to said control channel signal and receptive to said plurality of traffic channel signals, comprising;
i) a tuneable filter which substantially filters all but a selected traffic channel signal of said plurality of traffic channel signals, said tuneable filter having an adjustable characteristic;
ii) a received signal strength indicator circuit, responsive to said tuneable filter, for providing a received signal strength indicator (RSSI) signal in respect of a signal transmitted from said base station;
iii) a tuning circuit responsive to said RSSI signal and coupled to said tuneable filter for adjusting said filter characteristic; and
iv) a reference signal coupled to the tunable filter, the reference signal being based at least in part on the control channel signal;
whereinthe tuning circuit adjusts said adjustable characteristic of the tunable filter by using the reference signal as an accurate central frequency for a passband of the tuneable filter.
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Accused Products
Abstract
A communications system (10) comprising a base station (12) for controlling a control channel signal and a plurality of traffic channels and a communications device (17) responsive to the control channel signal (16) and receptive to the plurality of traffic channels. The communications device comprises a tuneable filter (48), having an adjustable characteristic, which substantially filters all but a selected traffic channel of the plurality of traffic channels. The communications device further comprises a tuning circuit (24, 38, 40, 44, 46, 52) for adjusting the filter characteristic. The tuning circuit (24, 38, 40, 44, 46, 52) uses the control channel signal (16) as an accurate central frequency (Fo) for a passband of the tuneable filter (48) and adjusts the filter characteristic to substantially a minimum insertion loss at the accurate central frequency, thereby substantially optimizing selectivity and sensitivity for the communications device (17).
61 Citations
34 Claims
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1. A radio communications system comprising:
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a) a radio base station for transmitting a control channel signal and a plurality of traffic channel signals separated in frequency from said control channel signal; and b) a radio communications device, receptive and responsive to said control channel signal and receptive to said plurality of traffic channel signals, comprising; i) a tuneable filter which substantially filters all but a selected traffic channel signal of said plurality of traffic channel signals, said tuneable filter having an adjustable characteristic; ii) a received signal strength indicator circuit, responsive to said tuneable filter, for providing a received signal strength indicator (RSSI) signal in respect of a signal transmitted from said base station; iii) a tuning circuit responsive to said RSSI signal and coupled to said tuneable filter for adjusting said filter characteristic; and iv) a reference signal coupled to the tunable filter, the reference signal being based at least in part on the control channel signal;
whereinthe tuning circuit adjusts said adjustable characteristic of the tunable filter by using the reference signal as an accurate central frequency for a passband of the tuneable filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18)
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14. The communications system in accordance 1, wherein the tuneable filter comprises a 2-pole monolithic crystal bandpass filter.
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19. A method of adjusting a filter characteristic of a tuneable filter of a communications device, the method comprising the steps of:
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a) tuning the tuneable filter of the communications device to receive a control channel signal transmitted at an accurate frequency by a base station responsible for the control of said communications device; b) establishing a centre for a passband of the tuneable filter using the accurate frequency of the control channel signal; c) adjusting said filter characteristic to a minimum insertion loss at said centre of the passband, thereby optimising selectivity and sensitivity for the communications device; d) subsequently tuning the tuneable filter to selectively receive a traffic channel signal, from a plurality of traffic channel signals transmitted by said base station, by filtering all but a selected traffic channel signal of said plurality of traffic channel signals. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method of adjusting a filter characteristic of a tuneable intermediate frequency filter of a radio communications receiver, the method comprising the steps of:
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a) supplying a parameter to the tuneable filter by means of a digital-to-analog converter to provide a first filter characteristic; b) tuning the tuneable filter to receive a control channel signal transmitted at an accurate frequency by a base station responsible for the control of said communications receiver; c) establishing a centre for a passband of the tuneable filter using the accurate frequency of the control channel signal; d) supplying to the tuneable filter a new parameter representative of a new filter characteristic, thereby adjusting said filter characteristic to a minimum insertion loss at said centre of the passband and optimising selectivity and sensitivity for the communications receiver; e) subsequently tuning the tuneable filter to selectively receive a traffic channel signal, from a plurality of traffic channel signals transmitted by said base station, by filtering all but a selected traffic channel signal of said plurality of traffic channel signals.
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Specification