Differential Mixer DC Offset Balancing for SOI2 Linearity

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Solution Overview

Problem

Mixer nonlinearities, particularly second-order nonlinearity, lead to undesirable intermodulation products and mixer imbalance, degrading the performance and quality of wireless reception.

Innovation Solution

An offset balancer with an offset quantifier and adjuster is used to determine and adjust the DC offset of a differential mixer, increasing the second-order intercept point to counteract existing imbalances and enhance mixer linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mixer imbalance occurs due to component mismatches and phase errors, then device complexity increases, but second-order nonlinearity increases and reception quality degrades

Engineering Contradiction:

Improvereception qualityVSAvoidsecond-order nonlinearity

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by adjusting the DC offset voltage of the mixer to optimize its operating point. By changing the bias conditions and electrical parameters of the mixer, the second-order nonlinearity is reduced while maintaining reception quality. This involves tuning parameters such as the DC offset level and bias currents to achieve optimal linearity performance.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If component mismatches and phase errors are present in the mixer, then device complexity remains constant, but mixer imbalance increases and spurious cross-modulation signals are generated

Engineering Contradiction:

Improvemixer structureVSAvoidspurious cross-modulation signals

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent implements preliminary anti-action by introducing a DC offset adjustment mechanism that pre-compensates for mixer imbalance before signal processing occurs. The offset balancer circuit proactively counteracts the effects of component mismatches and phase errors by applying corrective DC offsets, thereby preventing the generation of spurious cross-modulation signals rather than addressing them after they occur.

Inventive Principle:

Principle #9Preliminary anti-action

3Device complexity

If no offset adjustment is applied to the mixer, then device complexity remains low, but second-order intercept point is low and intermodulation products are undesirable

Engineering Contradiction:

Improveoffset balancer circuitVSAvoidmixer linearity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent introduces an intermediary offset balancer circuit that mediates between the input signals and the mixer. This intermediary component provides DC offset adjustment capabilities, allowing precise control over the mixer's operating point. The offset balancer acts as a mediator that improves mixer linearity and second-order intercept point without requiring changes to the core mixer structure, thereby maintaining ease of manufacture while enhancing performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7532874B2Offset balancer, method of balancing an offset and a wireless receiver employing the balancer and the method

Publication Date: 2009.05.12 TEXAS INSTRUMENTS INC

AI summary

The present invention provides an offset balancer for use with a differential mixer employing a wireless reception and an offset quantifier configured to indicate an existing DC offset of the mixer corresponding to an existing second-order intercept point applicable to the wireless reception. In one embodiment, the offset balancer includes an offset adjuster coupled to the offset quantifier and configured to provide an offset adjustment to the existing DC offset based on increasing the existing second-order intercept point.