| 摘要 |
<p>1. A digital circuit for measuring the instantaneous frequency Fs of a frequency-modulated signal on the basis of a phase shift vphi which is related to said instantaneous frequency in accordance with a trigonometral function, said circuit comprising more specifically first and second registers (20) and (21) arranged in series to ensure that at each sampling instant consecutive samples xn , xn+1 and xn+2 , respectively, be available at the outputs of these registers (21) and (20) and at the input (10) of the first register, and also means for determining the expression cos vphi =(xn +xn+2 )/2xn+1 , characterized in that it comprises, to allow the provision of an automatic gain control circuit, an amplitude-determining circuit comprised of : first and second squaring circuits (110) and (140) for squaring the output signal xn+1 of the first register (20) and for the output signal of an adder (40) of the samples xn and xn+2 , respectively ; a first multiplier (100) for multiplying the output signal xn from the second register (21) by the input signal xn+2 of the first register (20) ; a first subtracter (120) subtracting the output signal from the first multiplier (100) from the output signal from the first squaring circuit (110) ; a second multiplier (130) for multiplying the output signal from the first squaring circuit (110), after a shift through two bits for a multiplication by 4, by the output signal from the first subtracter (120) ; a second subtracter (150) subtracting the output signal from the first squaring circuit (110), after a shift through two bits for a multiplication by 4, from the output signal from the second squaring circuit (140) ; and a divider (160) for dividing the output signal from the second multiplier (130) by the output signal from the second subtracter (150), this divider supplying the square of said amplitude of the input signal.</p> |
