WIDEBAND FREQUENCY DISCRIMINATOR AND RADIOLOCALIZATION RECEIVER

• US 20070224965A1
• Filed: 03/20/2007
• Published: 09/27/2007
• Est. Priority Date: 03/22/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Nemerix, SA
• Inventors: BRENNER, Joel
• Granted Patent: US 7,966,359 B2
• Time in Patent Office: Days
• US Class Current: 455/336
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H03D 13/00 Circuits for comparing the phase or frequency of two mutually-independent oscillations measuring phase G01R25/00; phase-discriminators with yes/no output G01R25/005
• CPC Class Codes: H03D 3/006 by sampling the oscillations and further processing the samples, e.g. by computing techniques H03D3/007 takes precedence
• CPC Class Codes: H03L 7/085 concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00

Abstract

Frequency discriminator based on a combination of DFT operator and half-bin DFT operator, corresponding to a set of Twiddle factors with frequency double than the sampling frequency. The frequency estimators are so chose as not to have any zero or discontinuity point. Therefore the discriminator of the invention is more stable and well behaved in an extended operating range. The discriminator of the invention, when applied to a GPS receiver, allows a safer lock to the carrier frequency, even in presence of a large initial error, and avoids the problem of false locks.

Claims

1. Method of obtaining a frequency difference between an input signal (x) comprising a number of N successive samples (x_i) and a reference frequency, comprising the steps of:

applying to the samples (x_i) a discrete number of spectral component extraction operators (155a, 155b, 155c, 155d, 155e) for extracting the corresponding spectral components of the input signal,

combining mathematically the spectral components to a lower amplitude operator (C_D,) having a maximum of its transfer function at a lower frequency (f_d), and a upper amplitude operator (C_U,) having a maximum of its transfer function at a upper frequency (f_U) higher than the lower frequency (f_d) above the reference frequency,

obtaining the frequency difference from the value of the lower amplitude operator and upper amplitude operator (C_U,), characterized in that the response of lower amplitude operator and upper amplitude operator (C_D, C_U) exhibits no zeros or discontinuities in the operating frequency range.

2. Method according to the preceding claim, wherein the response of the lower and upper operators (C_D, C_U) exhibits no zeros or discontinuities at any frequency.

3. Method according to the any of the preceding claims, characterized in that the upper frequency (f_D) and the lower frequency (f_U) are symmetrically placed around the reference frequency.

4. Method according to any of the preceding claims, characterized in that the reference frequency is the zero frequency.

5. Method according to any of the preceding claims, characterized in that the two lower and upper operators (C_D, C_U) comprise a step of calculating an absolute value of the output.

6. Method according to any of the preceding claims, characterized in that each of the lower and upper operators (C_D, C_U) is a combination of a DFT operation, obtained by a linear combination of the samples (x_i), with weight (W) factors taken from the N distinct complex roots of unity of order N, and of a Half-bin DF operation, obtained by a linear combination of the samples (x_i), with weight (W) factors taken from the 2N distinct complex roots of unity of order 2N.

7. Method according to any of the preceding claims, wherein the frequency difference is obtained by the sole values of the lower and upper operators.

8. Method according to any of claims 1-7, wherein the frequency difference is obtained by the lower and upper operators and from the value of one or more DFT operators and half-bin DFT operators.

9. Method according to the preceding claim, wherein at least one of the DFT operators corresponds to the reference frequency.

10. Frequency discriminator device, comprising an input, for receiving an input signal, and frequency discriminator means (70), for generating an output signal (65) dependent on the difference from the fundamental frequency of the input signal and a reference frequency, wherein the discriminator means is arranged for carrying out the method of one of the preceding claims.

12. Frequency discriminator device according to claim 10 or 11, wherein the reference frequency is the zero frequency.

13. Frequency discriminator device according to one of claims 10 to 12, in combination with a variable frequency source (44), a mixer (45) for combining an input frequency (42) with an output of the variable frequency source (44), the discriminator comparing an output signal of the mixer and generating a frequency error signal, for driving the variable frequency source (44) and locking it to the input frequency (42), so to constitute a frequency control device.

14. GPS receiver, comprising a frequency discriminator according to one of claims 10 to 13.

15. Digital data carrier, comprising software code for carrying out the steps of methods of one of claims 1 to 9.

16. Computer program for carrying out the steps of methods of one of claims 1 to 9.

11. Frequency discriminator device, comprising an input, for receiving an input signal, and frequency discriminator means (70), for generating an output signal (65) dependent on the difference from the fundamental frequency of the input signal and a reference frequency;

wherein the frequency discriminator means (70) comprise frequency extraction means (702, 704) for extracting a discrete spectral components of the input signal, at a lower frequency (f_D) and at a upper frequency (f_U), the upper frequency (f_U) and the lower frequency (f_D) being placed above and under the reference frequency, whereas the frequency discriminator means (702, 704) has a maximum of its response for the corresponding spectral component;

characterized in that;

the response of the frequency discriminator means (702, 704) does not go to zero does not go to zero for any frequency in the operating frequency range.