Adaptive phase shift adjuster for resonator

• US 5,764,705 A
• Filed: 07/15/1996
• Issued: 06/09/1998
• Est. Priority Date: 07/15/1996
• Status: Expired due to Fees

• Current Assignee: BEI Technologies, Incorporated
• Original Assignee: Boeing North American Incorporated (The Boeing Co.)
• Inventors: White, Stanley A.
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US08/683,643
• Time in Patent Office: 694 Days
• Field of Search: 375/269, 375/270, 375/321, 375/324-327, 375/329, 375/332, 329/304, 329/352, 329/356, 329/367
• US Class Current: 375/324
• CPC Class Codes: H04L 27/3854 using a non - coherent carrier, including systems with baseband correction for phase or frequency offset

Abstract

The in-phase channel 28 of a complex demodulated resonator data output signal 12 should contain all of the sensed information, and the quadrature-phase channel 32 should contain none of it. This will not happen if the phase of the reference signal 14 is incorrect. The phase may be adjusted by first filtering each demodulated channel with a respective low-pass dc-blocked filter 34, 38 which passes only the frequencies of the sensed information. If the sensed information gets through on both channels, then there will be a non-zero cross-correlation between the channels. This cross-correlation can be servoed to a minimum by use of a feedback signal 22. Doing so will cause all of the sensed information to be in one channel 28, and diagnostic information to be in the other channel 32.

Claims

1. Apparatus for complex amplitude demodulating a resonator data output signal with respect to a resonator reference signal, the resonator reference signal having a frequency f₀, and the resonator data output signal having a passband centered at f₀ with a bandwidth of 2Δ

f, the apparatus comprising;

(a) a rotated complex demodulation reference signal generator connected to receive the resonator reference signal and a feedback signal and to thereby generate an in-phase reference signal and a quadrature-phase reference signal, the amount of rotation of the in-phase reference signal and the quadrature-phase reference signal with respect to the resonator reference signal being constructed to respond to the feedback signal;

(b) a complex amplitude demodulator comprising;

(1) an in-phase demodulation multiplier connected to multiply the in-phase reference signal by the resonator data output signal and to thereby produce an in-phase demodulated output signal; and

(2) a quadrature-phase demodulation multiplier connected to multiply the quadrature-phase reference signal by the resonator data output signal and to thereby produce a quadrature-phase demodulated output signal;

(c) an in-phase low pass dc-blocked (LPDCB) filter connected to receive the in-phase demodulated output signal and to thereby produce an LPDCB filtered in-phase signal, the in-phase LPDCB filter having an upper pass-band-edge frequency of Δ

f;

(d) a quadrature-phase LPDCB filter connected to receive the quadrature-phase demodulated output signal and to thereby produce a LPDCB filtered quadrature-phase signal, the quadrature-phase LPDCB filter having a response identical to that of the in-phase LPDCB filter; and

(e) a cross-correlator;

(1) connected to receive the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce the feedback signal, the feedback signal being responsive to a cross-correlation between the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal; and

(2) connected to apply the feedback signal to the rotated complex demodulation reference signal generator.

2. The apparatus of claim 1, wherein the rotated complex demodulation reference signal generator:

(a) is constructed to apply the feedback signal to a quadrature-phase rotation multiplier, which is also connected to receive a raw quadrature-phase signal, and to thereby produce a quadrature-phase product signal;

(b) includes a calculator constructed to;

(1) construe the feedback signal as a scaled sine signal; and

(2) convert it to a scaled cosine signal;

(c) is constructed to apply the scaled cosine signal to an in-phase rotation multiplier, which is also connected to receive a raw in-phase signal, and to thereby produce an in-phase product signal; and

(d) includes a rotation summer connected to sum the in-phase product signal and the quadrature-phase product signal, and to thereby produce a summed product signal.

3. The apparatus of claim 2, wherein the calculator is constructed to produce a Chebechev approximation scaled cosine signal.

4. The apparatus of claim 3, wherein the cross-correlator comprises:

(a) a cross-correlation multiplier connected to multiply together the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce a cross-correlation product; and

(b) an integrator connected to integrate the cross-correlation product, an output of the integrator being the feedback signal.

5. The apparatus of claim 4, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

6. The apparatus of claim 3, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

7. The apparatus of claim 2, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

8. The apparatus of claim 2, wherein the rotated complex demodulation reference signal generator comprises:

(a) a first Hilbert transformer connected to receive the resonator reference signal and to thereby produce the raw in-phase signal and the raw quadrature-phase signal; and

(b) a second Hilbert transformer connected to receive the summed product signal and to thereby produce the in-phase reference signal and the quadrature-phase reference signal.

9. The apparatus of claim 8, wherein the calculator is constructed to produce a Chebechev approximation scaled cosine signal.

10. The apparatus of claim 9, wherein the cross-correlator comprises:

(a) a cross-correlation multiplier connected to multiply together the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce a cross-correlation product; and

(b) an integrator connected to integrate the cross-correlation product, an output of the integrator being the feedback signal.

11. The apparatus of claim 10, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

12. The apparatus of claim 9, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

13. The apparatus of claim 8, wherein the cross-correlator comprises:

(a) a cross-correlation multiplier connected to multiply together the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce a cross-correlation product; and

(b) an integrator connected to integrate the cross-correlation product, an output of the integrator being the feedback signal.

14. The apparatus of claim 13, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

15. The apparatus of claim 8, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

16. The apparatus of claim 2, wherein the cross-correlator comprises:

(a) a cross-correlation multiplier connected to multiply together the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce a cross-correlation product; and

(b) an integrator connected to integrate the cross-correlation product, an output of the integrator being the feedback signal.

17. The apparatus of claim 16, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

18. The apparatus of claim 1, wherein the cross-correlator comprises:

(a) a cross-correlation multiplier connected to multiply together the LPDCB filtered in-phase signal and the LPDCB filtered quadrature-phase signal and to thereby produce a cross-correlation product; and

(b) an integrator connected to integrate the cross-correlation product, an output of the integrator being the feedback signal.

19. The apparatus of claim 18, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.

20. The apparatus of claim 1, wherein the cross-correlator further comprises an initializer constructed to initialize the feedback signal with a predetermined number.