Segmented Mixer Circuit for Accurate RF Power and Low LO Leakage

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Solution Overview

Problem

Existing cellular telephone RF transceiver circuits face inaccuracies in controlling output power levels and local oscillator leakage due to parasitic effects and non-scalable mixer sizes, which fail to maintain proportional reduction in output power and leakage as specified by communication standards.

Innovation Solution

A novel mixer circuit employing multiple identical Mixer and Frequency Divider Pair (MFDP) circuits, where each MFDP can be enabled or disabled independently, with a single frequency synthesizer providing a drive signal to all frequency dividers, allowing precise control of output power by adjusting the number of enabled MFDPs and proportionally scaling the composite local oscillator signal power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple mixers of different sizes are used to control output power levels, then output power can be adjusted across multiple steps, but parasitic effects cause inaccuracies in power level control

Engineering Contradiction:

Improveoutput power controlVSAvoidpower level accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The mixer is divided into multiple identical mixer units, each capable of being independently enabled or disabled. This segmentation allows precise control of output power by selecting which units are active, while maintaining identical characteristics among all units to eliminate parasitic variations that occur with differently-sized mixers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the parameter of mixer unit uniformity - all mixer units are made identical in size and structure rather than using progressively larger mixers. This parameter change eliminates the parasitic effects that arise from structural differences while still allowing power level control through the number of active units.

Inventive Principle:

Principle #35Parameter changes

2Power

If mixer size is doubled to increase output power, then power output increases, but parasitic effects do not scale proportionally causing inaccuracy

Engineering Contradiction:

Improveoutput powerVSAvoidpower step accuracy

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

Instead of using a single large mixer or progressively larger mixers, the invention segments the mixer into multiple identical units. Each unit contributes equally to the output power, and by enabling or disabling specific units, precise power steps are achieved without the parasitic scaling issues that occur when mixer size is doubled.

Inventive Principle:

Principle #1Segmentation

3Use of energy by moving object

If output power is reduced by disabling mixers, then power consumption decreases, but local oscillator leakage does not scale proportionally

Engineering Contradiction:

Improvepower consumptionVSAvoidlocal oscillator leakage

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The local oscillator signal is distributed to multiple identical mixer units, each with its own frequency divider. When a mixer unit is disabled, its associated frequency divider also stops generating the local oscillator signal, thereby eliminating leakage from that unit. This segmentation ensures that local oscillator leakage scales proportionally with the number of active mixer units.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention extracts the local oscillator signal generation function into separate frequency divider circuits associated with each mixer unit. This allows the local oscillator signal to be completely eliminated from disabled mixer units by disabling their dedicated frequency dividers, thereby removing the source of leakage rather than relying on passive suppression.

Inventive Principle:

Principle #2Taking out (Extraction)

4Measurement precision

If identical mixer units are used instead of progressively larger mixers, then parasitic effects are eliminated improving accuracy, but device complexity increases

Engineering Contradiction:

Improvepower level accuracyVSAvoidmixer circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Each mixer unit is designed as a universal, identical module that can be enabled or disabled based on the required power level. This universality simplifies the overall design compared to creating multiple differently-sized mixers, as a single modular unit is replicated rather than multiple unique designs being implemented.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS7941115B2Mixer with high output power accuracy and low local oscillator leakage

Publication Date: 2011.05.10 QUALCOMM INC

AI summary

A circuit receives a first signal (for example, a baseband signal) and mixes it with a local oscillator (LO) signal, and outputs a second signal (for example, an RFOUT signal). The circuit includes multiple identical Mixer and Frequency Divider Pair (MFDP) circuits. Each MFDP can be enabled separately. Each MFDP includes a mixer and a frequency divider that provides the mixer with a local version of the LO signal. The MFDP outputs are coupled together so that the output power of the second signal (RFOUT) is the combined output powers of the various MFDPs. By controlling the number of enabled MFDPs, the output power of the second signal is controlled. Because the MFDPs all have identical layouts, accuracy of output power step size is improved. Because LO signal power within the circuit automatically changes in proportion to the number of enabled MFDPs, local oscillator leakage problems are avoided.