Analog Correlator VCO Gain Tracking for Wideband Modulation

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Solution Overview

Problem

Existing phase/frequency modulation systems face challenges in accurately setting and maintaining the gain of a Voltage-Controlled Oscillator (VCO) for wideband modulation, as the VCO gain depends on multiple factors and requires precise control, which is difficult to achieve, especially in two-point modulation systems.

Innovation Solution

A phase/frequency modulation system that includes a circuit to set and adjust the gain and offset parameters of a VCO using a frequency tracking loop, incorporating a correlator to project PLL correction signals onto a reference modulation signal, an integrator to accumulate outputs, and logic to scale and offset signals applied to the VCO, ensuring accurate VCO gain control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If two-point modulation with direct VCO modulation is used to support wideband phase modulation, then wideband modulation capability is improved, but VCO gain accuracy deteriorates because the gain depends on multiple factors and is difficult to set accurately

Engineering Contradiction:

Improvewideband modulation capabilityVSAvoidVCO gain accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the modulated VCO output is fed back through a correlator that compares it with a reference modulation signal. The correlator output is integrated and used to generate feedback signals that automatically adjust the VCO gain and offset, closing the control loop and maintaining accurate VCO parameters despite variations in operating conditions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual or static mechanical adjustment of VCO gain with an automatic electronic control system. The correlator and integrator circuits electronically adjust the VCO parameters based on real-time comparison with the reference signal, eliminating the need for precise manual setting and compensating for drift automatically

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If VCO gain is set to depend on multiple factors for wideband operation, then modulation flexibility is improved, but control complexity increases making accurate gain setting difficult

Engineering Contradiction:

Improvemodulation flexibilityVSAvoidcontrol complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system performs self-adjustment through the correlator feedback loop. The correlator automatically detects deviations from the desired modulation and generates correction signals that adjust the VCO parameters, allowing the system to self-correct without external intervention or complex manual calibration procedures

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS7522005B1K<sub>FM </sub>frequency tracking system using an analog correlator

Publication Date: 2009.04.21 QUINTIC MICROELECTRONICS WUXI

AI summary

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.