Calibrated method and device for narrow band Doppler compensation

• US 5,095,538 A
• Filed: 09/29/1989
• Issued: 03/10/1992
• Est. Priority Date: 09/29/1989
• Status: Expired due to Term

• Current Assignee: Torsal Technology Group Limited LLC (Intellectual Ventures LLC)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Durboraw, I. Newton III
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): URBAN, EDWARD F
• Application Number:
  US07/414,494
• Time in Patent Office: 893 Days
• Field of Search: 455/52, 455/65, 455/71, 455/99, 455/63, 455/316, 455/317, 455/343, 331/1 A, 342/99, 342/418, 375/1, 375/98, 370/104.1
• US Class Current: 455/71
• CPC Class Codes: H04B 7/01 Reducing phase shift
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A Doppler compensating device which conserves power and can be used with hand-held communication devices comprises a phase lock loop for tracking a Doppler phase offset and a Doppler offset calibration loop which generates a Doppler offset curve. The Doppler offset calibration loop extracts Doppler offset points from the phase lock loop, and from these points calibrates a set of three parameters defining the Doppler offset curve using an estimation algorithm such as the least squares algorithm. After the curve is defined, the compensation device extracts points from the Doppler offset curve and deactivates the phase lock loop. This process preserves power within the hand-held communication devices.

Claims

1. A low-power Doppler compensating device comprising:

first means for tracking a dynamic Doppler phase shift from an input signal to generate a first Doppler correction signal;

said input signal having a Doppler phase shift due to predictable relative motion between a transmitter and a receiver;

second means for generating a Doppler offset curve for a dynamic Doppler phase shift, said second means generating a second Doppler correction signal;

said second means coupled to said first means to receive a set of Doppler phase shift samples to calibrate said Doppler offset curve;

third means for removing said Doppler phase shift from said input signal, said third means coupled to said first means and to said second means; and

said third means receiving said first Doppler correction signal for a given time, after which said third means receives said second Doppler correction signal.

2. A low-power Doppler compensating device according to claim 1 wherein said first means for tracking comprises a phase lock loop.

3. A low-power Doppler compensating device according to claim 1 wherein said second means for generating comprises an open loop time dependent compensator.

4. A low-power Doppler compensating device according to claim 3 wherein said second means for generating comprises:

accumulator means for extracting said set of Doppler phase shift samples from said first means, said accumulator means accumulating said extracted set of Doppler phase shift samples;

calibration means for generating calibration parameters representing said Doppler offset curve from said set of Doppler phase shift samples, said calibration means coupled to said accumulator means to receive said accumulated extracted set of Doppler phase shift samples;

synthesis means for extracting said calibration parameters representing said Doppler offset curve, said synthesis means coupled to said calibration means to extract said calibration parameters;

said synthesis means generating frequency estimates from said calibration parameters;

numerically controlled oscillator (NCO) coupled to said synthesis means to receive said frequency estimates, said NCO generating said second Doppler correction signal from said frequency estimates; and

said NCO coupled to said third means to relay said second Doppler correction signal to said third means and said NCO coupled separately to said accumulator means.

5. A low-power Doppler compensating device according to claim 1 wherein said second means for generating comprises:

accumulator means for extracting said set of Doppler phase shift samples from said first means, said accumulator means accumulating said extracted set of Doppler phase shift samples;

calibration means for generating calibration parameters representing said Doppler offset curve from said set of Doppler phase shift samples, said calibration means coupled to said accumulator means to receive said accumulated extracted set of Doppler phase shift samples;

synthesis means for extracting said calibration parameters representing said Doppler offset curve, said synthesis means coupled to said calibration means to extract said calibration parameters;

said synthesis means generating frequency estimates from said calibration parameters;

numerically controlled oscillator (NCO) coupled to said synthesis means to receive said frequency estimates, said NCO generating said second Doppler correction signal from said frequency estimates; and

said NCO coupled to said third means to relay said second Doppler correction signal to said third means and said NCO coupled separately to said accumulator means.

6. A low-power Doppler compensating device according to claim 1 wherein said third means comprises a signal demodulator/discriminator.

7. A method for adjusting an input signal for Doppler offset comprising the steps of:

tracking the Doppler offset in a phase lock loop (PLL);

generating a Doppler correction signal within said PLL;

modulating said Doppler correction signal with said input signal;

extracting and storing Doppler phase shift samples from said PLL;

generating calibration parameters defining a Doppler offset curve;

synthesizing frequency estimates from said calibration parameters;

generating a frequency command from said frequency estimates;

generating said Doppler correction signal from said frequency command;

deactivating said PLL; and

modulating said input signal with said Doppler correction signal.

8. A method of adjusting an input signal for Doppler offset according to claim 7 wherein said step of generating calibration parameters defining a Doppler offset curve comprises the step of calculating said calibration parameters using a least squares algorithm.

9. A method for adjusting an input signal for Doppler offset according to claim 8 wherein said step of calculating said calibration parameters using a least squares algorithm comprises:

calculating a Doppler estimate using the algorithm ##EQU7## calculating sensitivity vectors using the algorithm ##EQU8## calculating a correction vector using the algorithm ##EQU9## calcualting a new value of x using the algorithm x_new =x_old +δ

x; and

iterating from the step of calculating a Doppler estimate until δ

x=0.

10. A method for adjusting an input signal for Doppler offset according to claim 7 wherein said step of synthesizing frequency estimates comprise the step of compensating a receiver reference frequency from a predicted offset frequency using the algorithm