Demodulator for digital FM signals
AssigneeBlaupunkt-Werke GmbH
InventorsKarl-Dirk Kammeyer, Wolfgang Tobergte
Life of this patent
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Abstract
For compensation of the effects of multi-path reception, a cascade distortion corrector composed of distortion corrector blocks successively connected in series is provided for a digital FM demodulator that needs non-recursive filtering. Each distortion corrector block produces an increase of the phase rotation and of the propagation time as well as a reduction of the reflection factor of the input signal. The cascade distortion corrector leads to a significant reduction of the hardware expense compared to the previously used transversal type filter structures. Sufficient compensation of the multi-path reception effects can be obtained by connecting five or six distortion corrector blocks one after the other.
Claims14
Demodulator for frequency modulated signals in digital form comprising
- an analog-to-digital converter for converting analog frequency modulated signals into digital form and a band-pass filter ahead of the input of said converter and having a narrow pass-band for reduction of adjacent-channel interference, said demodulator further comprising, for suppression of effects of multi-path reception and for compensating for distortion produced by said band-pass filter:
- a non-recursive cascade distortion corrector unit connected for filtering digital signals produced by said converter and comprising several (n) distortion corrector blocks connected in tandem one after the other, each of said corrector blocks (44, 46, 48, 50, 52) having an input, signal delay means and multiplier means and being constituted for raising the phase rotation (.psi.) and the propagation time (.tau.) and reducing the reflected wave amplitude (.rho.) of signals supplied to the input of the corrector block, each of said corrector blocks delaying, by said signal delay means, said supplied signals for a single interval of time (2.sup.n-1 .kappa.T) and every said multiplier means in each of said corrector blocks multiplying, by a complex reflection factor, the signals delayed by said delay means.
Dependencies are inferred from the claim text.