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US 8,803,627 B1Granted
Wideband direct DCO modulator with in-band compensation
AssigneeInnophase, Inc.
InventorsYang Xu, Sara Munoz Hermoso, Xi Li
Life of this patent
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Abstract
A Direct VCO (DCO) modulation apparatus and method that provides a wideband modulated signal output. The wideband response is obtained via signal processing to counteract a high-pass frequency characteristic as seen from the VCO modulation input. That is, low frequency components of data signals are compensated before being applied to a VCO input. The high-pass characteristic in combination with the compensated signal provides a relatively flat, wideband frequency response of the DCO modulator.
Claims30
An apparatus comprising:
- a phase locked loop (PLL) having a VCO-output high-pass characteristic, the PLL comprising:
- a voltage controlled oscillator (VCO) having a PLL VCO control input and a modulation VCO control input;
- and,
- a phase locked loop controller coupled to the PLL VCO control input and configured to output a PLL control signal to the PLL VCO control input;
- a signal phase generator configured to generate a phase signal of a desired information-modulated transmit signal;
- a compensation filter configured to generate a compensated phase signal by increasing low-frequency components of the phase signal to compensate for the VCO-output high-pass characteristic and the VCO gain characteristic;
- a phase derivative generator having an input coupled to the compensation filter, the phase derivative generator configured to receive the compensated phase signal and to convert the compensated phase signal to a compensated phase derivative modulation signal, and having a modulation control output coupled to the modulation VCO control input for providing the compensated phase derivative modulation signal to the VCO.
4 more elements
A method comprising:
- generating a phase signal of a desired information-modulated transmit signal;
- compensation filtering the phase signal to generate a compensated phase signal by increasing low-frequency components of the phase signal to compensate for a VCO-output high-pass characteristic;
- generating a compensated phase derivative modulation signal by converting the compensated phase signal to a compensated phase derivative modulation signal;
- providing the compensated phase derivative modulation signal to a modulation input of a VCO;
- generating a PLL VCO control signal using a low pass loop filter operating on a PLL error signal formed using an output of the VCO;
- applying the PLL VCO control signal to a PLL VCO control input, wherein the PLL VCO control signal operates to provide the VCO-output high-pass characteristic by removing low-frequency variations from an output of the VCO, and wherein the compensated phase derivative modulation signal counteracts the VCO-output high pass characteristic;
- and,
- providing the output of the VCO to a signal amplifier.
5 more elements
An apparatus comprising:
- an oscillator having an oscillator output, a first variable capacitance, and a second variable capacitance;
- a time-to-digital converter (TDC) connected to the oscillator output configured to generate a frequency error signal at an error output;
- a loop filter connected to the TDC and configured to low-pass filter the frequency error output signal and to generate a loop VCO error signal at a loop filter output, the loop filter output connected to the first variable capacitance to reduce low-frequency carrier deviations at the oscillator output, including data-modulation-induced low-frequency variations;
- a low-frequency-peaking compensation filter connected to the second variable capacitance, the low-frequency-peaking compensation filter configured to generate a compensated phase signal by increasing low-frequency components of a desired phase signal to compensate for the reduction of data-modulation-induced low-frequency carrier deviations;
- a phase derivative generator having an input coupled to the low-frequency peaking compensation filter, the phase derivative generator configured to receive the compensated phase signal and to convert the compensated phase signal to a compensated phase derivative modulation signal, and having a modulation control output coupled to the second variable capacitance.
2 more elements
Dependencies are inferred from the claim text.