TX LO Leakage Calibration Circuit for mmWave Transceivers

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The use of super heterodyne architecture in mmW frequency communication systems is problematic due to conflicts between mmW communication frequencies and the frequency of the local oscillator (LO) signal, leading to interference and the need to discern between desired communication information signals and LO signal leakage.

Innovation Solution

A TX LO leakage calibration circuit is implemented, comprising a transceiver with a transmit and receive portion, an interface circuit, an impedance control circuit for the LNA, a power detector, and a local oscillator cancellation element, which adjusts input impedance and detects LO leakage to correct for interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If super heterodyne architecture is used in mmW frequency communication systems, then frequency translation capability is improved, but LO signal leakage and interference increase

Engineering Contradiction:

Improvefrequency translation capabilityVSAvoidLO signal leakage

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent detects the harmful LO leakage signal using a power detector and then feeds back this information to adjust the transmit signal, converting the harmful leakage into useful feedback information for calibration and cancellation purposes

Inventive Principle:

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

Solution Approach 2:

The patent implements a feedback loop where the power detector monitors LO leakage from the transmit section, and the detected leakage information is used to adjust and cancel the leakage signal, creating a closed-loop system that continuously reduces harmful emissions

Inventive Principle:

Principle #23Feedback

2Productivity

If LO signal frequency is increased to match mmW communication frequencies, then communication performance is improved, but frequency conflict and interference increase

Engineering Contradiction:

Improvecommunication performanceVSAvoidfrequency conflict

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent performs LO leakage calibration before normal communication operations begin, pre-characterizing the leakage behavior at different frequencies and power levels, so that when actual communication starts, the system already has baseline data to compensate for frequency conflicts

Inventive Principle:

Principle #10Preliminary action

3Power

If TX power is increased to improve communication range, then signal strength is improved, but LO leakage detection accuracy deteriorates

Engineering Contradiction:

ImproveTX powerVSAvoidLO leakage detection accuracy

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The patent uses a variable gain amplifier to selectively amplify only the weak LO leakage signal portion while leaving the strong communication signal unchanged, applying partial amplification specifically to the leakage component to enable accurate detection without being overwhelmed by the main transmit signal

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12549216B2Transmit (TX) local oscillator (LO) leakage calibration

Publication Date: 2026.02.10 QUALCOMM INC

AI summary

A transmit (TX) local oscillator (LO) leakage calibration circuit including a transceiver having a transmit portion and a receive portion, an interface circuit connected to the transmit portion and the receive portion, an impedance control circuit connected to a low noise amplifier (LNA) in the receive portion, the impedance control circuit configured to adjust an input impedance for the LNA, a power detector coupled to an output of the LNA, and a local oscillator cancellation element connected to the power detector, the local oscillator cancellation element configured to adjust an input to the transmit portion based on TX LO leakage detected by the power detector.