Methods and apparatus for delay free phase shifting in correcting PLL phase offset
First Claim
1. An apparatus to eliminate a frequency-dependent differential phase shift, Δ
- θ
, between a double sideband suppressed carrier modulated angular rate information signal and its sinusoidal demodulation reference signal in a gyroscope angular rate sensing circuit, the circuit including a demodulation reference source, said apparatus comprising;
a demodulator;
a phase shifter in a demodulation reference signal path, the demodulation reference signal path being between the demodulation reference source and said demodulator, said phase shifter configured to adjust a phase of the sinusoidal demodulation reference signal;
a phase locked loop (PLL) comprising a phase detector, a servo equalizer, and a dual-frequency, numerically controlled oscillator, said PLL configured to provide a demodulation signal based on the phase shifted demodulation reference signal; and
a phase shift command source comprising frequency dependent outputs and configured to provide an input to said phase shifter to command an appropriate phase adjustment, the frequency dependent outputs based upon a tuning parameter, β
, of a numerically controlled oscillator (NCO) in said PLL that is controlled by the demodulation reference signal.
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Accused Products
Abstract
An apparatus eliminates a differential phase shift, Δθ(f), between a double sideband suppressed carrier modulated angular rate information signal and its sinusoidal demodulation reference signal in a gyroscope angular rate sensing circuit including a signal reference source. The apparatus includes a demodulator, a phase shifter in a demodulation reference signal path, the demodulation reference signal path being between the signal reference source and the demodulator. The phase shifter is configured to adjust a phase of the sinusoidal demodulation reference signal. A phase locked loop (PLL) includes a phase detector, a servo equalizer, and a dual-frequency, numerically controlled oscillator. The PLL is configured to provide a demodulation signal based on the phase shifted demodulation reference signal, and a phase shift command source is configured to provide an input to the phase shifter to command an appropriate phase adjustment.
21 Citations
17 Claims
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1. An apparatus to eliminate a frequency-dependent differential phase shift, Δ
- θ
, between a double sideband suppressed carrier modulated angular rate information signal and its sinusoidal demodulation reference signal in a gyroscope angular rate sensing circuit, the circuit including a demodulation reference source, said apparatus comprising;a demodulator; a phase shifter in a demodulation reference signal path, the demodulation reference signal path being between the demodulation reference source and said demodulator, said phase shifter configured to adjust a phase of the sinusoidal demodulation reference signal; a phase locked loop (PLL) comprising a phase detector, a servo equalizer, and a dual-frequency, numerically controlled oscillator, said PLL configured to provide a demodulation signal based on the phase shifted demodulation reference signal; and a phase shift command source comprising frequency dependent outputs and configured to provide an input to said phase shifter to command an appropriate phase adjustment, the frequency dependent outputs based upon a tuning parameter, β
, of a numerically controlled oscillator (NCO) in said PLL that is controlled by the demodulation reference signal. - View Dependent Claims (2, 3, 4, 5)
- θ
-
6. A method for eliminating a differential phase shift, Δ
- θ
, between a double sideband suppressed carrier modulated information signal and its sinusoidal demodulation reference signal in a circuit, the circuit including a demodulator, a phase shift command source and a phase shifter in a reference signal path between a signal reference source and the demodulator, said method comprising;generating an appropriate phase adjustment command from the phase shift command source to the phase shifter by providing frequency dependent outputs sin [Δ
θ
(f)] and cos [Δ
θ
(f)], from the phase shift command source; andadjusting a phase of the sinusoidal demodulation reference signal with the phase shifter, the differential phase shift being frequency dependent according to Δ
θ
(f). - View Dependent Claims (7, 8, 9, 10, 11)
- θ
-
12. An angular rate measurement system comprising:
-
a first analog to digital converter (ADC); a gyroscope configured to sense an angular rate input and provide a modulated angular rate information signal and a sinusoidal demodulation reference signal; a demodulator configured to demodulate a signal representative of the angular rate information signal; a phase shifter configured to adjust a phase of a signal representative of the sinusoidal demodulation reference signal; a phase locked loop configured to provide a demodulation signal to said demodulator, the demodulation signal based on the phase adjusted demodulation reference signal; a phase shift command source configured to provide a frequency based input to said phase shifter to enable an appropriate phase adjustment of the demodulation reference signal, the phase adjustment eliminating a frequency dependent differential phase shift, Δ
θ
(f), between the modulated angular rate information signal and the sinusoidal demodulation reference signal; anda first digital filter, said first ADC and said first filter configured to provide the signal representative of the angular rate information signal from the modulated angular rate information signal. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification