Method and apparatus for receiving an amplitude modulated radiosignal
First Claim
1. A method for receiving an AM radio signal which may be transmitted in any one of a plurality of frequency channels within a predetermined frequency bandwidth, the method comprising operating a tuning means (3) of a radio receiver to scan the channels of the predetermined frequency bandwidth for detecting a signal, characterised in that on detecting a signal in a frequency channel the tuning means (3) is operated to scan a frequency bandwidth adjacent the channel in which the signal is detected for determining the number of channels in which the signal can be detected, and operating the tuning means (3) at the frequency of a middle one of the channels in which the signal can be detected.
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Accused Products
Abstract
Receiving apparatus (1) for receiving an amplitude modulated signal which may be transmitted on a plurality of frequency channels within a predetermined frequency bandwidth comprises a tuner (3) for sequentially scanning through the channels under the control of a microprocessor (6) which determines the presence of a signal on a channel to which the tuner (3) is tuned. A first validation circuit (10) determines if the received signal is a valid type signal, and if so the microprocessor (6) counts the channels from the channel on which the signal is first detected to the channel on which the signal can no longer be detected is reached. The microprocessor (6) determines the middle one of the channels in which the signal is detected, and the microprocessor (6) locks the tuner (3) onto the frequency of the middle channel, and simultaneously operates a gate circuit (11) for outputting at least one complete signal to security apparatus of a motor vehicle for switching the state of the security apparatus from one of an armed and a disarmed state to the other of the armed and disarmed state. A noise suppressing circuit (9) is responsive to a noise analysing circuit (8) under the control of the microprocessor (6) for suppressing noise in the received signal.
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Citations
53 Claims
- 1. A method for receiving an AM radio signal which may be transmitted in any one of a plurality of frequency channels within a predetermined frequency bandwidth, the method comprising operating a tuning means (3) of a radio receiver to scan the channels of the predetermined frequency bandwidth for detecting a signal, characterised in that on detecting a signal in a frequency channel the tuning means (3) is operated to scan a frequency bandwidth adjacent the channel in which the signal is detected for determining the number of channels in which the signal can be detected, and operating the tuning means (3) at the frequency of a middle one of the channels in which the signal can be detected.
- 27. A receiving apparatus for receiving an amplitude modulated radio signal which may be transmitted in any one of a plurality of frequency channels within a predetermined frequency bandwidth, the apparatus (1) comprising a receiving means (1) for receiving the AM. radio signal, a tuning means (3) for sequentially tuning the receiving means (1) to the plurality of frequency channels, a detecting means (6) for detecting the presence of a signal, and a control means (6) for controlling the tuning means (3) for scanning the frequency bandwidth for detecting a signal in a frequency channel, characterised in that the control means (6) is responsive to the detecting means (6) detecting a signal in a frequency channel for controlling the tuning means (3) to scan a frequency bandwidth adjacent the frequency channel in which the signal is detected for determining the number of channels in which the signal can be detected, and for further operating the tuning means (3) at the frequency of a middle one of the channels in which the signal can be detected.
Specification