Method and apparatus for system clock adjustment

• US 6,026,133 A
• Filed: 07/08/1997
• Issued: 02/15/2000
• Est. Priority Date: 07/11/1996
• Status: Expired due to Fees

• Current Assignee: Nokia Solutions and Networks US LLC (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Sokoler, Izydor
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHAYOUR, MOHAMMAD H
• Application Number:
  US08/889,361
• Time in Patent Office: 952 Days
• Field of Search: 375/369, 375/365, 375/368, 370/305, 370/510, 370/514, 370/516
• US Class Current: 375/365
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically
• CPC Class Codes: H04M 1/724 User interfaces specially adapted for cordless or mobile telephones
• CPC Class Codes: H04M 1/72502 with one base station connected to a single line
• CPC Class Codes: H04M 2250/08 home cordless telephone systems using the DECT standard
• CPC Class Codes: H04W 56/0085 detecting a given structure in the signal

Abstract

A system clock of a radio telephone is adjusted in relation to an associated transmitter/receiver station system clock by detecting a predetermined part (SYNC word) which occurs periodically in a digital signal. A clock signal having pulses synchronous with the system clock signal of the radio telephone is formed. The clock pulses in the clock signal are counted between the detection of two predetermined parts in the digital signal, and the system clock is corrected in response to the number of pulses between the detection of said two predetermined parts in the digital signal.

Claims

1. A method of adjusting a radio telephone system clock in relation to an associated transmitter/receiver station system clock of a base station, comprising steps of:

generating in the radio telephone a system clock signal and a further clock signal that is synchronous with the system clock signal;

repetitively counting clock pulses of said further clock signal between a detection of two predetermined parts that occur periodically in a digital signal received from the base station; and

repetitively correcting said system clock in response to a number of clock pulses that are counted between the detection of the two predetermined parts of the digital signal as long as said radio telephone communicates with said base station.

2. A method of adjusting a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising detecting a predetermined part which occurs periodically in a digital signal, providing a clock signal which is synchronous with the system clock signal of the radio telephone, counting the clock pulses in the clock signal between the detection of two predetermined parts in the digital signal, and correcting the system clock in response to the number of pulses between the detection of said two predetermined parts in the digital signal, wherein the digital signal is a Digital Cordless Telephone System DECT signal, and wherein the two predetermined parts comprise the signal preamble and synchronization SYNC word occurring in two different time slots.

3. A method of adjusting a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising steps of generating in the radio telephone a system clock signal and another clock signal that is synchronous with the system clock signal, repetitively detecting a predetermined part which occurs periodically in a digital signal received from the transmitter/receiver station, counting clock pulses in the clock signal between the detection of two predetermined parts in the digital signal, and repetitively correcting, so long as the radio telephone communicates with the transmitter/receiver station, the system clock in response to a number of clock pulses that are counted between the detection of said two predetermined parts in the digital signal by generating a correction voltage to correct the system clock in response to the number of clock pulses that are counted in relation to a predetermined value.

4. A frequency adjustment device for a radio telephone to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising means to detect a predetermined part which occurs periodically in a digital signal, a clock device to supply a clock signal which is synchronous with the system clock signal, a counter device adapted to count the clock pulses in the clock signal of the clock device, and a control device to register the status of the counter device when the detecting means detect the predetermined part in the digital signal, said control device being moreover adapted to repetitively correct, so long as the radio telephone communicates with the transmitter/receiver station, the system clock in response to the status of the counter device at the time of the detection of the predetermined part.

5. A frequency adjustment device according to claim 4, wherein the detecting means comprise a synchronization SYNC word detector to detect the SYNC word in a Digital Cordless Telephone System DECT signal.

6. A frequency adjustment device according to claim 4, wherein the clock device supplies the clock signal by dividing the system clock frequency by means of a frequency divider.

7. A frequency adjustment device according to claim 6, wherein the clock device supplies the clock signal with a frequency of 1152 kHz by dividing the system clock with a frequency of 10.368 MHz by means of a frequency divider which divides the system clock frequency by a factor 9.

8. A frequency adjustment device for a radio telephone to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising means to detect a predetermined part which occurs periodically in a digital signal, a clock device to supply a clock signal which is synchronous with the system clock signal, a counter device adapted to count the clock pulses in the clock signal of the clock device, and a control device to register the status of the counter device when the detecting means detect the predetermined part in the digital signal, said control device being moreover adapted to correct the system clock in response to the status of the counter device in the detection of the predetermined part, wherein the digital signal is a Digital Cordless Telephone System DECT signal, and wherein the counter device counts the pulses in the clock signal for a plurality of consecutive frames in the DECT signal.

9. A frequency adjustment device for a radio telephone to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising means to detect a predetermined part which occurs periodically in a digital signal, a clock device to supply a clock signal which is synchronous with the system clock signal, a counter device adapted to count the clock pulses in the clock signal of the clock device, and a control device to register the status of the counter device when the detecting means detect the predetermined part in the digital signal, said control device being moreover adapted to correct the system clock in response to the status of the counter device in the detection of the predetermined part, wherein the digital signal is a Digital Cordless Telephone System DECT signal, and wherein the counter device counts the pulses in clock signals for a plurality of consecutive frames that occur during a multiframe in the DECT signal.

10. A frequency adjustment device for a radio telephone to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising means to detect a predetermined part which occurs periodically in a digital signal, a clock device to supply a clock signal which is synchronous with the system clock signal, a counter device adapted to count the clock pulses in the clock signal of the clock device, and a control device to register the status of the counter device when the detecting means detect the predetermined part in the digital signal, said control device being moreover adapted to correct the system clock in response to the status of the counter device in the detection of the predetermined part, wherein the control device, when the detecting means detect the predetermined part in the form of a SYNC word, generate an error signal in response to the status of the counter device, said error signal being used for correcting the system clock.

11. A frequency adjustment device according to claim 10, wherein the control device is associated with a digital-to-analog converter to which the error signal is fed, said converter generating an analog control voltage contribution which is fed to the system clock.

12. A radio telephone having a frequency adjustment device to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, the frequency adjustment device comprising a detector for detecting at least one predetermined portion which occurs periodically in a digital signal that is received from the transmitter/receiver station, a clock for supplying a clock signal which is synchronous with the system clock signal, a counter for counting the clock pulses in the clock signal of the clock, and a controller for registering the status of the counter when the detector detects the at least one predetermined portion of the digital signal, said controller being operative to repetitively correct the system clock, so long as the radio telephone communicates with the transmitter/receiver station, in response to a status of the counter when the at least one predetermined portion is detected.

14. A radio telephone according to claim 12, wherein the clock supplies the clock signal by dividing the system clock frequency by a frequency divider.

15. A radio telephone according to claim 14, wherein the clock supplies the clock signal with a frequency of 1152 kHz by dividing the system clock with a frequency of 10.368 MHz by a frequency divider which divides the system clock frequency by a factor 9.

13. A radio telephone having a frequency adjustment device to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, the frequency adjustment device comprising a detector for detecting at least one predetermined portion which occurs periodically in a digital signal, a clock for supplying a clock signal which is synchronous with the system clock signal, a counter for counting the clock pulses in the clock signal of the clock, and a controller for registering the status of the counter when the detector detects the at least one predetermined portion of the digital signal, said controller operative to correct the system clock in response to a status of the counter when the at least one predetermined portion is detected, wherein the detector comprises a synchronization SYNC word detector for detecting the at least one predetermined portion, and wherein the at least one predetermined portion is comprised of a SYNC word in a Digital Cordless Telephone System DECT signal.

16. A radio telephone having a frequency adjustment device to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, the frequency adjustment device comprising a detector for detecting at least one predetermined portion which occurs periodically in a digital signal, a clock for supplying a clock signal which is synchronous with the system clock signal, a counter for counting the clock pulses in the clock signal of the clock, and a controller for registering the status of the counter when the detector detects the at least one predetermined portion of the digital signal, said controller operative to correct the system clock in response to a status of the counter when the at least one predetermined portion is detected, wherein the digital signal is a Digital Cordless Telephone System DECT signal, and wherein the counter counts the pulses in the clock signal for a plurality of consecutive frames in the DECT signal.

17. A radio telephone according to claim 16, wherein the counter counts pulses in clock signals for a plurality of consecutive frames that occur during a multiframe.

18. A radio telephone having a frequency adjustment device to adjust the frequency of a radio telephone system clock in relation to an associated transmitter/receiver station system clock, the frequency adjustment device comprising a detector for detecting at least one predetermined portion which occurs periodically in a digital signal, a clock for supplying a clock signal which is synchronous with the system clock signal, a counter for counting the clock pulses in the clock signal of the clock, and a controller for registering the status of the counter when the detector detects the at least one predetermined portion of the digital signal, said controller operative to correct the system clock in response to a status of the counter when the at least one predetermined portion is detected, wherein the controller, when the detector detects the at least one predetermined portion of the digital signal in the form of a synchronization SYNC word, generates an error signal in response to the status of the counter, said error signal being used for correcting the system clock.

19. A radio telephone according to claim 18, wherein the controller is associated with a digital-to-analog converter to which the error signal is fed, said converter generating an analog control voltage contribution which is fed to the system clock.

20. A method of adjusting a radio telephone system clock in relation to an associated transmitter/receiver station system clock, comprising detecting a predetermined part which occurs periodically in a digital signal, providing a clock signal which is synchronous with the system clock signal of the radio telephone, counting the clock pulses in the clock signal between the detection of two predetermined parts in the digital signal, and correcting the system clock in response to the number of pulses between the detection of said two predetermined parts in the digital signal, wherein a correction voltage is generated to correct the system clock in response to the number of pulses in relation to a predetermined value, wherein the digital signal is a Digital Cordless Telephone System DECT signal, and wherein the two predetermined parts comprise the signal preamble and synchronization SYNC word occurring in two different time slots.

21. A radio telephone for communicating with a network via an associated base station, said radio telephone comprising:

means for detecting a predetermined part which occurs periodically in data bursts in a digital signal received from said associated base station;

means for generating a system clock signal for said radio telephone;

means for generating a further clock signal which is synchronous with said system clock signal;

a counter for counting clock pulses in said further clock signal; and

a control device for registering a status of said counter when said detecting means detects the predetermined part in the digital signal;

said control device correcting said system clock signal in response to the registered status of said counter; and

said control device controlling said counter to repeat counting the clock pulses and to then repeat correcting the system clock signal accordingly for as long as said radio telephone communicates with said base station.