Mixer Circuitry Using Inverted LO Capacitors for Noise Figure

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Solution Overview

Problem

Designing a satisfactory mixer for electronic devices with wireless communications capabilities is challenging due to noise figure degradation caused by phase noise associated with the local oscillator, which can couple to the input port through parasitics, degrading the noise performance of the mixer circuitry.

Innovation Solution

Incorporating an oscillator phase noise cancellation capacitor that receives inverted oscillator signals to offset parasitic coupling noise, improving noise figure performance by canceling phase noise associated with the local oscillator signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mixer is designed for wireless communications circuitry, then the mixer can demodulate radio-frequency signals, but phase noise from the local oscillator couples to the input port through parasitics and degrades the noise figure performance

Engineering Contradiction:

Improvenoise figure performanceVSAvoidphase noise coupling

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by introducing a cancellation signal that is the inverse of the phase noise before the noise degrades the signal quality. The local oscillator signal is inverted and fed through a cancellation path to preemptively counteract the phase noise that would otherwise couple into the RF input through parasitic capacitances, thereby preserving noise figure performance

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent uses an intermediary approach by introducing a cancellation path with its own capacitor and resistor elements that act as a mediator between the local oscillator and the RF input. This intermediary path generates an opposing signal that neutralizes the harmful phase noise coupling through the parasitic capacitances at the RF input port

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If oscillator signals are used to control mixer switches, then signal demodulation is enabled, but parasitic capacitances at the input port couple the oscillator signals and degrade noise performance

Engineering Contradiction:

Improvesignal demodulation capabilityVSAvoidparasitic coupling noise

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful parasitic capacitance into a beneficial element by using the same parasitic path to inject the cancellation signal. The inversion capacitor is positioned to utilize the existing parasitic coupling mechanism, turning the previously harmful oscillator signal coupling into a useful noise cancellation effect that improves overall mixer performance

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11095252B1Mixer circuitry with noise cancellation

Publication Date: 2021.08.17 APPLE INC

AI summary

An electronic device may include wireless circuitry with a baseband processor, a transceiver, a front-end module, and an antenna. The transceiver may include mixer circuitry. The mixer circuitry may include switches controlled by oscillator signals. The mixer circuitry may also include oscillator phase noise cancelling capacitors controlled by inverted oscillator signals. Operated in this way, the mixer circuitry exhibits improved noise figure performance.