Complex digital demodulator employing Chebychev-approximation de

Details Complex digital demodulator employing Chebychev-approximation de Complex digital demodulator employing Chebychev-approximation de

1993-08-12

1994-11-01

Mis, David

Demodulators

Amplitude modulation demodulator

Input signal combined with local oscillator or carrier...

329356, 364566, 73489, H03D 100, G01P 1509

Patent

active

053610369

ABSTRACT:
To demonstrate a signal, the signal is sampled and each sample of the signal is multiplied by the sine and the cosine of a phase angle indicating when the sample was taken from the signal. The sinusoidal signal for producing an in-phase demodulated signal is Chebychev-approximation derived and computed as a selected even or odd polynomial, depending on whether the phase angle falls within one of a plurality of angular ranges. So that the error in the synthetic sinusoid is minimax and so that the even and odd polynomials have similar computational complexity, the angular ranges for the even polynomial exceed the angular ranges for the odd polynomial. Preferably, the sinusoid for producing a quadrature-phase demodulated signal is computed as a differential of the sinusoid spliced from the odd and even polynomials. Therefore the quadrature-phase demodulated signal can be provided with a minimal increase in computational complexity. The demodulation method permits a signal to be demodulated by a reference frequency signal to produce a demodulated digital signal that is synchronized to a system clock. The system clock need not be synchronized to the reference frequency signal. The demodulation method is computationally efficient, and permits a digital signal processor to be programmed for demodulating an angular rate signal from a quartz angular rate sensor vibrating at about 10 kilohertz.

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