Method and apparatus for receiving an amplitude modulated radio signal

• US 7,099,638 B2
• Filed: 12/20/2001
• Issued: 08/29/2006
• Est. Priority Date: 12/20/2000
• Status: Expired due to Fees

• Current Assignee: Land Rover (TATA Motors Limited), Hi-Key Ltd. (Valeo SE)
• Original Assignee: Land Rover (TATA Motors Limited), Hi-Key Ltd. (Valeo SE)
• Inventors: Greenwood, Jeremy J, Lyons, Patrick J
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Haroon, Adeel
• Application Number:
  US10/451,069
• Publication Number:
  US 20040041692A1
• Time in Patent Office: 1,713 Days
• Field of Search: 4551601-1681, 455/296, 375/136, 375/137, 375147-153
• US Class Current: 455/166.1
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/00238 the transmittted data signal containing a code which is changed
• CPC Class Codes: G07C 2009/00555 comprising means to detect or avoid relay attacks
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2209/61 Signal comprising different frequencies, e.g. frequency hopping
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: H03J 1/0091 provided with means for scanning over a band of frequencies H03J1/0058 takes precedence

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 analyzing circuit (8) under the control of the microprocessor (6) for suppressing noise in the received signal.

Claims

1. A method 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 method comprising:

operating a tuning means of a radio receiver to scan the channels of the predetermined frequency bandwidth for detecting a signal, and on a signal being detected operating the tuning means 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,

operating the tuning means to select the frequency of a middle one of the channels in which the signal can be detected for receiving the signal,

passing a received signal in each frequency channel selected by the tuning means through a variable level noise suppressing means,

analysing the received signal from the noise suppressing means from each frequency channel selected by the tuning means for the presence of noise,

incrementing the noise suppressing means by one level of suppression for the frequency channel selected by the tuning means on noise being detected in the analysed received signal,

setting a flag means for each channel in which noise is detected in the received signal after the level of suppression at which the noise suppressing means is operated for that channel is at a predetermined maximum noise suppression level, and

skipping each channel for which the flag means is set on each scan of the predetermined frequency bandwidth for a predetermined number of scans.

2. A method as claimed in claim 1 in which the tuning means is locked onto the frequency of the middle one of the channels in which the signal can be detected for a period sufficient for allowing at least one complete signal to be received.

3. A method as claimed in claim 2 in which the tuning means is locked onto the frequency of the middle one of the channels in which the signal can be detected for a predetermined time period.

4. A method as claimed in claim 1 in which the frequency bandwidths of the respective frequency channels are similar.

5. A method as claimed in claim 1 in which each time a signal is detected in a frequency channel in a scan the received signal is analysed for determining if the signal is of a valid type.

6. A method as claimed in claim 1 in which the tuning means is operated for scanning the frequency channels within the predetermined frequency bandwidth sequentially from one end of the predetermined bandwidth to the other.

7. A method as claimed in claim 6 in which the tuning means is operated for scanning the predetermined frequency bandwidth by sequentially altering the scanned frequency in frequency steps.

8. A method as claimed in claim 1 in which on detecting a signal in one of the frequency channels, the tuning means is operated to sequentially scan the channels from the channel in which the signal is first detected until a channel in which the signal can no longer be detected has been reached for determining the middle one of the channels in which the signal can be detected.

9. A method as claimed in claim 8 in which a count is recorded of the number of frequency channels through which the tuning means is stepped from the channel in which the signal is first detected to the channel in which the signal can no longer be detected has been reached for determining the middle one of the channels in which the signal can be detected.

10. A method as claimed in claim 9 in which the number of frequency steps through which the tuning means is stepped after the channel in which the signal is first detected is limited to a predetermined number of steps.

11. A method as claimed in claim 8 in which when the channel in which the signal can no longer be detected has been reached or the tuning means has been stepped through the predetermined number of steps from the channel in which the signal is first detected, the frequency at which the tuning means 9 is operating is altered by approximately half the number of frequency steps through which the tuning means had been operated from the channel in which the signal is first detected.

12. A method as claimed in claim 1 in which, on no noise being present in the signal from the noise suppressing means on the channel to which the tuning means is tuned, the suppression level at which the noise suppressing means is being operated is decremented by one suppression level for that channel until the suppression level at which the noise suppressing means is being operated for that channel is reduced to a zero level of suppression.

13. 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 comprising:

a receiving means for receiving the radio signal,

a tuning means for sequentially tuning the receiving means to the plurality of frequency channels,

a detecting means for detecting the presence of a signal,

a control means for controlling the tuning means for sequentially scanning the channels of the predetermined frequency bandwidth, the control means being responsive to the detecting means detecting a signal in one of the frequency channels for controlling the tuning means 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 to select a middle one of the channels in which the signal can be detected,

a variable level noise suppressing means operable under the control of the control means for suppressing noise in the received signal on each selected frequency channel, and

a noise analysing means for analysing the received signal on each selected channel for noise after the received signal has been passed through the noise suppressing means, the control means being responsive to noise being detected in the received signal of a selected channel by the noise analysing means for incrementing the level of suppression at which the noise suppressing means is being operated by one level of suppression for that channel, and for setting a flag means for each channel for which noise is still present in the received signal after the noise suppressing means is operated at a maximum predetermined noise suppression level for that channel, and the control means is responsive to the flag means being set for operating the tuning means to skip each channel for which the flag means has been set for a predetermined number of scans.

14. Apparatus as claimed in claim 13 in which the control means locks the tuning means onto the frequency of the middle one of the channels in which the signal can be detected for a period sufficient for allowing at least one complete signal to be received.

15. Apparatus as claimed in claim 13 in which a first signal analysing means is provided for analysing each received signal for determining if the signal is of a valid type.

16. Apparatus as claimed in claim 13 in which the control means operates the tuning means for scanning the frequency channels of the predetermined frequency bandwidth sequentially from one end of the predetermined bandwidth to the other.

17. Apparatus as claimed in claim 13 in which the control means operates the tuning means for scanning the predetermined frequency bandwidth by sequentially altering the scanned frequency in respective frequency steps.

18. Apparatus as claimed in claim 13 in which the control means is responsive to the detecting means detecting a signal in one of the channels for operating the tuning means to sequentially son the channels from the channel in which the signal is first detected until a channel in which the signal can no longer be detected has been reached for determining the middle one of the channels in which the signal can he detected.

19. Apparatus as claimed in claim 13 in which the control means stores a count of the number of channels through which the tuning means is stepped from the first channel in which a signal is detected to the channel in which the signal can no longer be detected has been reached.

20. Apparatus as claimed in claim 19 in which the control means is responsive to the count of the number of channels in which the signal can be detected exceeding a predetermined number or to the channel in which the signal can no longer be detected being reached for altering the frequency at which the tuning means is operating to a frequency which is at least one frequency step towards the channel in which the signal is first detected for determining the middle one of the channels in which the signal can be detected.

21. Apparatus as claimed in claim 13 in which the control means is responsive to the noise analysing means failing to detect noise in the signal from a channel to which the tuning means is tuned for reducing the level of suppression to which the noise suppressing means is set for that channel by one level to a minimum of zero level of suppression.

22. Apparatus as claimed in claim 13 in which a gate means is provided which is responsive to a valid type signal being detected for gating the valid type signal from the apparatus.

23. Security apparatus for a motor vehicle the security apparatus comprising the receiving apparatus as claimed in claim 13, and a second analysing means for analysing each valid type signal gated from the receiving apparatus for determining if the valid type signal is a valid signal for the security apparatus.

24. Apparatus as claimed in claim 13 in which a storing means is provided for storing the level of suppression at which the noise suppressing means is being operated for each channel.