Wideband I/Q Generation Using PLL and Variable Polyphase Filter

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Solution Overview

Problem

Conventional I/Q signal generation devices in wireless communication systems face issues with in-phase/quadrature-phase mismatching, phase noise from oscillators, and high power consumption, especially when dealing with high frequencies and multiple communication standards, leading to performance deterioration and increased complexity.

Innovation Solution

The proposed solution involves a phase locked loop (PLL) and a polyphase filter with variable capacitors (varactors) to control the local oscillator's frequency and separate I/Q signals effectively, minimizing mismatching and allowing wideband oscillation control without a limiter, thereby reducing phase noise and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a frequency divider is used in the oscillator for I/Q matching, then the oscillation frequency can be controlled, but phase mismatching occurs when second harmonics are present in the input signal

Engineering Contradiction:

Improveoscillation frequency controlVSAvoidI/Q phase matching

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent changes the parameter of the polyphase filter from fixed to variable by using varactor diodes whose capacitance can be adjusted via control voltages. This allows the filter to adapt to different oscillation frequencies while maintaining I/Q matching accuracy, resolving the contradiction between frequency adaptability and phase matching precision.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If an RC polyphase filter is used for I/Q matching, then narrow-range frequency control is achieved, but I/Q signal power is reduced

Engineering Contradiction:

Improvefrequency control rangeVSAvoidI/Q signal power

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The patent transforms the RC polyphase filter into a variable polyphase filter using varactor diodes, enabling wide frequency control range without the power loss inherent in RC filters. The voltage-controlled capacitance adjustment optimizes signal power across the frequency range.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If a limiter is added to reduce gain mismatching in polyphase filter methods, then I/Q matching improves, but device complexity and size increase

Engineering Contradiction:

ImproveI/Q gain matchingVSAvoidcircuit structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the need for the limiter component by using the variable polyphase filter with varactor diodes to directly compensate for gain and phase mismatches. This reduces device complexity while maintaining matching accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If multiple communication standards are supported, then system versatility improves, but I/Q mismatching and power consumption increase

Engineering Contradiction:

Improvecommunication standard compatibilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by stationary object

Solution Approach 1:

The patent creates a universal I/Q signal generation circuit using voltage-controlled varactor diodes that can adapt to multiple communication standards through electronic control. This single circuit design handles multiple standards without requiring separate dedicated circuits for each, reducing overall power consumption.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 minimizes I/Q mismatching, enables wideband frequency control, prevents performance deterioration due to phase noise, and contributes to device miniaturization by eliminating the need for a limiter, resulting in improved signal quality and reduced power consumption.

Implementation Method 1

a phase locked loop (PLL) and a polyphase filter with variable capacitors (varactors) to control the local oscillator's frequency

Methodology Applied

Scientific EffectPhase locked loop: Feedback

Implementation Method 2

a polyphase filter installed between the local oscillator and the mixers, for separating the oscillation signal from the local oscillator into an I signal and a Q signal

Methodology Applied

Scientific EffectPolyphase filter: Filter (electronic)

Implementation Method 3

polyphase filter with variable capacitors (varactors) to control the local oscillator's frequency

Methodology Applied

Scientific EffectVaractor effect: Capacitance

Data Source

PatentUS7454185B2Wideband I/Q signal generation device

Publication Date: 2008.11.18 SAMSUNG ELECTRONICS CO LTD

AI summary

An apparatus for generating an in-phase/quadrature-phase (I/Q) signal in a wireless transceiver is disclosed, including a local oscillator for generating an oscillation signal, and first and second mixers for mixing an oscillation signal with a transmission/reception signal to convert the transmission/reception signal into a baseband or high-frequency signal. The apparatus includes a phase locked circuit for controlling the local oscillator, and a polyphase filter installed between the local oscillator and the mixers, for separating the oscillation signal from the local oscillator into an I signal and a Q signal depending on a control signal from the phase locked circuit, and outputting the separated I and Q signals to the first and second mixers, respectively.