KFM frequency tracking system using an analog correlator

• US 7,522,005 B1
• Filed: 07/27/2007
• Issued: 04/21/2009
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Sequoia Communications Corporation
• Inventors: Groe, John B., Walley, Kenneth Scott
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US11/829,828
• Time in Patent Office: 634 Days
• Field of Search: 331/1.A, 331 16- 18, 331/25
• US Class Current: 331/16
• CPC Class Codes: H03C 3/08 Modifications of modulator to linearise modulation, e.g. by feedback, and clearly applicable to more than one type of modulator
• CPC Class Codes: H03C 3/0908 using a phase locked loop
• CPC Class Codes: H03L 2207/06 Phase locked loops with a controlled oscillator having at least two frequency control terminals

Abstract

An apparatus providing a phase/frequency modulation system is disclosed herein. The apparatus includes a first circuit configured to introduce an offset to center a signal applied to a VCO. The apparatus further includes a second circuit configured to set a gain of the VCO. A frequency tracking network is configured to dynamically adjust one or both of the offset and the gain.

Claims

1. Apparatus providing a phase/frequency modulation system, the apparatus comprising:

a first circuit configured to introduce an offset to center a signal applied to a VCO;

a second circuit configured to set a gain of the VCO; and

a frequency tracking network configured to dynamically adjust one or both of the offset and the gain.

2. The apparatus of claim 1 wherein the frequency tracking network includes a correlator network operative to track a frequency error signal applied to the VCO.

3. The apparatus of claim 2 wherein the correlator network includes:

a correlator;

an integrator coupled to an output of the correlator; and

a window comparator coupled to an output of the integrator.

4. Apparatus for tracking in a two point phase/frequency modulation system to adjust an offset and scale of a signal applied to a VCO of a phase-locked loop (PLL), the apparatus comprising:

a correlator configured to project a PLL correction signal onto a reference modulation signal;

an integrator for accumulating an output of the correlator;

a window comparator for determining a polarity of an output of the integrator; and

logic comprising a first counter configured to scale the signal applied to the VCO based on an output of the window comparator, and a second counter configured to offset the signal applied to the VCO based on the output of the window comparator.

5. Apparatus for tracking in a two point phase/frequency modulation system to adjust an offset and scale of a signal applied to a VCO, the apparatus comprising:

a correlator operative to project a PLL correction signal onto a reference modulation signal and produce a correlation signal;

an A/D converter for producing a digital signal based upon the correlation signal; and

logic configured to compute a system error and to generate, based on the digital signal, a first output used in offsetting the signal applied to the VCO and a second output used in scaling the signal applied to the VCO.

6. A phase/frequency modulation system, comprising:

a phase-locked loop (PLL) having a VCO including a first port and a second port wherein during operation of the PLL an error signal is received by the first port;

a correlator network configured to track the error signal and produce an output signal; and

a tracking loop which generates, in response to the output signal, a VCO control signal applied to the second port.

7. The system of claim 6 wherein the tracking loop includes:

logic configured to generate an offset adjustment signal and a gain adjustment signal, and

a tracking network for providing the VCO control signal based upon the offset adjustment signal and the gain adjustment signal.