Digital phase locked loop
AssigneeKoninklijke Philips Electronics N.V.
InventorsHans-Jürgen Kühn, Manfred Zupke
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Abstract
The invention relates to a digital phase locked loop (PLL) 12 for demodulating an intermediate frequency signal. The digital phase locked loop 12 comprises two coordinate rotation digital computers 24 and 30 in its phase detector. The robustness the PLL 12 can be improved by means of a gain control circuit 27, a sign detector 20, a carrier monitoring circuit 28 and an adjustable loop filter 32.
Claims13
A digital phase locked loop (PLL) for demodulation of an amplitude-modulated signal, in particular for an intermediate frequency demodulator for broadcast signals, having a digital phase comparison circuit, a digital loop filter, and a digitally controlled oscillator, the phase comparison circuit comprising a digital mixer and a phase transfer circuit, characterized in that the phase transfer circuit comprises a periodic transfer function with a phase error of π, so that a phase shift of π arising through amplitude overmodulation of the input signal can be suppressed.
A digital phase locked loop for demodulation of an amplitude-modulated signal, in particular for an intermediate frequency demodulator for broadcast signals, having a digital phase comparison circuit, a digital loop filter, and a digitally controlled oscillator, the phase comparison circuit comprising a digital mixer and a phase transfer circuit, characterized in that the phase locked loop comprises a carrier monitoring circuit, wherein a lower limit value of the magnitude of the carrier signal strength can be detected by means of the carrier monitoring circuit and wherein the phase transfer circuit can be deactivated if a lower limit value is detected.
A digital phase locked loop for demodulation of an amplitude-modulated signal, in particular for an intermediate frequency demodulator for broadcast signals, having a digital phase comparison circuit, a digital loop filter, and a digitally controlled oscillator, the phase comparison circuit comprising a digital mixer and a phase transfer circuit, characterized in that the digital loop filter is actively connected to a gain control circuit and the bandwidth of the loop filter can be set as a function of an output of the gain control circuit.
A digital phase locked loop for demodulation of an amplitude-modulated signal, in particular for an intermediate frequency demodulator for broadcast signals, having a digital phase comparison circuit, a digital loop filter, and a digitally controlled oscillator, the phase comparison circuit comprising a digital mixer and a phase transfer circuit, characterized in that the digital loop filter comprises a frequency locked loop (FLL), a gradient of the output signal of the phase transfer circuit can be determined by means of the frequency locked loop and the digitally controlled oscillator can be set by means of the determined gradient, wherein the phase locked loop may be brought into a locked state by adjusting the digitally controlled oscillator in the event of deviation of the carrier signal frequency by 0 to 1.6 MHz from a nominal frequency.
Dependencies are inferred from the claim text.