Systems and methods for automatic deviation setting and control in radio transmitters

• US 5,983,077 A
• Filed: 07/31/1997
• Issued: 11/09/1999
• Est. Priority Date: 07/31/1997
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul Wilkinson
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): APPIAH, CHARLES NANA
• Application Number:
  US08/904,131
• Time in Patent Office: 831 Days
• Field of Search: 455/110, 455/112, 455/113, 455/118, 455/42, 455/44, 332/128, 332/127, 331/23, 331/17, 375/373, 375/376
• US Class Current: 455/44
• CPC Class Codes: H03C 3/0925 applying frequency modulation at the divider in the feedback loop
• CPC Class Codes: H03C 3/0933 using fractional frequency division in the feedback loop of the phase locked loop
• CPC Class Codes: H03C 3/0941 applying frequency modulation at more than one point in the loop
• CPC Class Codes: H03C 3/095 applying frequency modulation to the loop in front of the voltage controlled oscillator
• CPC Class Codes: H03C 3/0966 modulating the reference clock
• CPC Class Codes: H03L 7/189 comprising a D/A converter for generating a coarse tuning voltage
• CPC Class Codes: H03L 7/197 a time difference being used for locking the loop, the counter counting between numbers which are variable in time or the frequency divider dividing by a factor variable in time, e.g. for obtaining fractional frequency division H03L7/1806 takes precedence

Abstract

A frequency modulation (FM) radio transmitter, such as a cellular telephone, includes an automatic deviation control system to automatically compensate for varying sensitivity of the FM transmitter. The FM transmitter includes a phase lock loop including a controlled oscillator that produces a frequency modulated input signal on an output channel frequency in response to a control input that is applied thereto. A scaler is responsive to the input signal and to at least one scaling content, to scale the input signal based upon the at least one scaling constant and to provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on the channel frequency. An automatic deviation control system measures the control signal that is applied to the controlled oscillator when tuned to one of the plurality of output channel frequencies and updates at least one of the scaling constants based upon the measured control input, to thereby provide automatic deviation control.

Claims

1. A frequency modulation (FM) radio transmitter which frequency modulates an input signal on one of a plurality of output channel frequencies, the FM radio transmitter comprising:

a phase lock loop including a controlled oscillator that produces the frequency modulated input signal on one of the plurality of output channel frequencies in response to a control input that is applied thereto;

a scaler that is responsive to the input signal and to a scaling constant to scale the input signal based upon the scaling constant and provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on one of the plurality of output channel frequencies; and

an automatic deviation control system that measures the control input that is applied to the controlled oscillator when tuned to one of the plurality of output channel frequencies, estimates a tangential modulation sensitivity of the controlled oscillator using the measurement of the control input, and updates the scaling constant based on the estimated tangential modulation sensitivity.

2. An FM radio transmitter according to claim 1 wherein the automatic deviation control system computes a change of frequency of the controlled oscillator relative to a corresponding change in the control input that is applied to the controlled oscillator, based uon the measured control input, to estimate the tangential modulation sensitivity of the controlled oscillator.

3. An FM radio transmitter according to claim 1 wherein the automatic deviation control system first measures the control input that is applied to the controlled oscillator during manufacture thereof and sets the scaling constant based on the tangential modulation sensitivity estimated using the measurement of the control input during manufacture, and then measures the control input that is applied to the controlled oscillator during operation thereof after manufacture, and updates the scaling constant based on the tangential modulation sensitivity estimated using the measurement of the control input after manufacture.

4. An FM radio transmitter according to claim 1 wherein the automatic deviation control system measures the control input that is applied to the controlled oscillator at each of the plurality of output channel frequencies and repeatedly updates a plurality of scaling constants corresponding to the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the measurements of the control input.

5. An FM radio transmitter according to claim 1 wherein the automatic deviation control system repeatedly measures the control input that is applied to the controlled oscillator at some of the plurality of output channel frequencies and repeatedly updates a plurality of scaling constants corresponding to the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the measurements of the control input and interpolation.

6. An FM radio transmitter according to claim 5 wherein the interpolation is one of linear interpolation, quadratic interpolation or higher order interpolation.

7. An FM radio transmitter according to claim 1 wherein the automatic deviation control system measures the control input that is applied to the controlled oscillator in response to a user command.

8. An FM radio transmitter according to claim 1 wherein the automatic deviation control system repeatedly scans the controlled oscillator through the plurality of output channel frequencies, repeatedly measures the control input that is applied to the controlled oscillator at the plurality of output channel frequencies and repeatedly updates a plurality of scaling constants corresponding to the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the measurements of the control input.

9. An FM radio transmitter according to claim 1 wherein the automatic deviation control system measures the control input that is applied to the controlled oscillator when power is applied to the FM radio transmitter.

10. An FM radio transmitter according to claim 1 wherein the automatic deviation control system repeatedly measures the control input that is applied to the controlled oscillator during frequency modulation of one of the plurality of output channel frequencies and repeatedly updates a plurality of scaling constants corresponding to the plurality of output channel frequencies based upon the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the control input measurement for the one channel frequency.

11. An FM radio transmitter according to claim 1 wherein the automatic deviation control system comprises:

an analog-to-digital converter that converts the control input into a digital signal; and

a control processor that is responsive to the digital signal to calculate the scaling constant; and

wherein the scaler comprises a digital signal processor that is responsive to the input signal and to the scaling constant, to scale the input signal based upon the scaling constant and provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on one of the plurality of channel frequencies.

12. An FM radio transmitter according to claim 1 wherein the phase lock loop comprises:

a phase detector that is responsive to a reference frequency and to an error input, to detect phase differences therebetween;

a loop filter that is responsive to the phase detector to provide a filtered error signal to the controlled oscillator; and

a fractional divider that is responsive to the controlled oscillator, to produce the error input.

13. An FM radio transmitter according to claim 1 wherein the input signal is a cellular radiotelephone input signal and wherein the plurality of output channel frequencies are a plurality of cellular telephone channel frequencies.

14. A deviation controlling method for a frequency modulation (FM) radio transmitter which frequency modulates an input signal on one of a plurality of output channel frequencies, the FM radio transmitter comprising a phase lock loop including a controlled oscillator that produces the frequency modulated input signal on one of the plurality of output channel frequencies in response to a control input that is applied thereto;

and a scaler that is responsive to the input signal and to a scaling constant to scale the input signal based upon the scaling constant and provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on one of the plurality of output channel frequencies;

the deviation setting method comprising the steps of;

measuring the control input that is applied to the controlled oscillator when tuned to one of the plurality of output channel frequencies;

estimating a tangential modulation sensitivity of the controlled oscillator using the measurement of the control input; and

updating the scaling constant based on the estimated tangential modulation sensitivity.

15. A method according to claim 14:

wherein the estimating step comprises the step of computing a change in frequency of the controlled oscillator relative to a corresponding change in the control input that is applied to the controlled oscillator, based upon the measured control input.

16. A method according to claim 14 wherein the measuring and updating steps comprise the steps of:

first measuring the control input that is applied to the controlled oscillator during manufacture thereof and setting the scaling constant based on the tangential modulation sensitivity estimated using the measurement of the control input during manufacture; and

then measuring the control input that is applied to the controlled oscillator during operation thereof after manufacture, and updating the scaling constant based on the tangential modulation sensitivity estimated using the measurement of the control input after manufacture.

17. A method according to claim 14 wherein the measuring and updating steps comprise the steps of:

measuring the control input that is applied to the controlled oscillator at each of the plurality of output channel frequencies; and

updating a plurality of scaling constants corresponding to the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the measurements of the control input.

18. A method according to claim 14 wherein the measuring and updating steps comprise the steps of:

measuring the control input that is applied to the controlled oscillator at some of the plurality of output channel frequencies; and

updating scaling constants corresponding to others of the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for the others of the plurality of output channel frequencies using the measurements of the control input and interpolation.

19. A method according to claim 14 wherein the measuring step is initiated in response to a user command.

20. A method according to claim 14 wherein the measuring and updating steps comprise the steps of:

scanning the controlled oscillator through the plurality of output channel frequencies;

measuring the control input that is applied to the controlled oscillator at the plurality of output channel frequencies; and

updating a plurality of scaling constants corresponding to the plurality of output channel frequencies based on the tangential modulation sensitivity estimated for each of the plurality of output channel frequencies using the measurements of the control input.

21. A method according to claim 14 wherein the measuring step is initiated when power is applied to the FM radio transmitter.

22. A method according to claim 14 wherein the measuring and updating steps comprise the steps of:

measuring the control input that is applied to the controlled oscillator while tuned to one of the plurality of output channel frequencies; and

updating scaling constants corresponding to more than one of the plurality of output channel frequencies based upon the tangential modulation sensitivity estimated for each of the more than one of the plurality of output channel frequencies using the control input measurement for the one channel frequency.

23. A frequency modulation (FM) radio transmitter which frequency modulates an input signal on one of a plurality of output channel frequencies, the FM radio transmitter comprising:

a phase lock loop including a controlled oscillator that produces the frequency modulated input signal on one of the plurality of output channel frequencies in response to a control input that is applied thereto;

a scaler that is responsive to the input signal and to at least one scaling constant to scale the input signal based upon the at least one scaling constant and provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on one of the plurality of output channel frequencies; and

an automatic deviation control system that repeatedly measures the control input that is applied to the controlled oscillator when tuned to some of the plurality of output channel frequencies and repeatedly updates scaling constants for all of the plurality of output channel frequencies by interpolation.

24. An FM radio transmitter according to claim 23 wherein the interpolation is one of linear interpolation, quadratic interpolation, or higher order interpolation.

25. A deviation controlling method for a frequency modulation (FM) radio transmitter which frequency modulates an input signal on one of a plurality of output channel frequencies, the FM radio transmitter comprising a phase lock loop including a controlled oscillator that produces the frequency modulated input signal on one of the plurality of output channel frequencies in response to a control input that is applied thereto;

and a scaler that is responsive to the input signal and to at least one scaling constant to scale the input signal based upon the at least one scaling constant and provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on one of the plurality of output channel frequencies;

the deviation setting method comprising the steps of;

measuring the control input that is applied to the controlled oscillator when tuned to some of the plurality of output channel frequencies; and

updating scaling constants for others of the plurality of output channel frequencies by interpolation in response to the measured control input.