Multi-Stream Receiver Frequency Planning Against VCO Pulling

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Solution Overview

Problem

In multi-stream TV receivers, the simultaneous operation of voltage-controlled oscillators (VCOs) can lead to frequency pulling, degrading reception quality due to insufficient frequency distance between local oscillator frequencies, particularly in DOCSIS applications.

Innovation Solution

A method and apparatus for monitoring the local oscillator frequency change in multi-stream receivers and resetting the frequency planning to maximize the frequency distance between VCOs, using offset frequency generation techniques such as fractional-N phase locked loops and separate integer-N PLLs to prevent interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple receivers operate simultaneously with closely spaced local oscillator frequencies, then multi-stream reception capability is improved, but frequency pulling between VCOs occurs degrading reception quality

Engineering Contradiction:

Improvemulti-stream reception capabilityVSAvoidreception quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system dynamically adjusts the frequency planning of VCOs based on real-time monitoring of frequency distance. When the frequency distance between local oscillators falls below a threshold likely to cause pulling, the system resets the frequency planning to maximize frequency distance, thereby adaptively preventing VCO pulling while maintaining multi-stream reception capability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operating parameters (frequency planning) of the VCOs to maintain optimal frequency distance. By monitoring local oscillator frequency changes and adjusting VCO frequencies accordingly, the system ensures that frequency spacing remains sufficient to prevent pulling while still enabling simultaneous multi-stream operation

Inventive Principle:

Principle #35Parameter changes

2Productivity

If local oscillator frequencies are placed close together to maximize channel utilization, then spectral efficiency is improved, but VCO pulling and coupling occur between receivers

Engineering Contradiction:

Improvespectral efficiencyVSAvoidVCO pulling and coupling

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system implements feedback monitoring of local oscillator frequency changes in real-time. When frequency distance between oscillators falls below a threshold, the system detects this condition and triggers a frequency planning reset to maximize frequency distance, thereby preventing VCO pulling while maintaining efficient spectral utilization

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary frequency planning optimization by proactively resetting VCO frequency plans before pulling occurs. By monitoring frequency distance and preemptively adjusting frequencies when they approach critical spacing, the system prevents harmful coupling effects before they degrade reception quality

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively minimizes VCO pulling, enhancing the reception quality by maintaining a sufficient frequency distance between oscillators, thereby reducing spurs and noise correlation, and allowing for simultaneous operation of multiple streams without de-sensing.

Implementation Method 1

at least two receivers having respective voltage controlled oscillators (VCOs), the method including monitoring a change in local oscillator frequency

Methodology Applied

Scientific EffectVoltage-controlled oscillation:

Implementation Method 2

using offset frequency generation techniques such as fractional-N phase locked loops and separate integer-N PLLs

Methodology Applied

Scientific EffectPhase locked loop:

Data Source

PatentUS9325927B2Method of operating a multi-stream reception scheme

Publication Date: 2016.04.26 NXP BV

AI summary

A method of operating a multi-stream reception scheme, such as DOCSIS (Data Over Cable Service Interface Specifications), comprising at least two receivers (10, 12, 14) having respective voltage controlled oscillators (16), the method including monitoring a change in local oscillator frequency in a selected one of the at least two streams and, if the frequency distance between the local oscillator frequencies is below a value likely to cause pulling or coupling between the voltage controlled oscillators of the at least two receivers, resetting the frequency planning of the selected one of the at least two streams to maximize the frequency distance of the voltage controlled oscillator of the selected stream with the voltage controlled oscillators of the or the other streams.