Zero-IF Transmitter Decoupling Stage for Noise and LO Leakage

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Solution Overview

Problem

Zero IF transceiver architectures face challenges with noise, high power consumption, I-Q mismatch, and local oscillator leakage due to the need for high-speed level shifters and gain-dependent issues in existing designs.

Innovation Solution

Incorporating an intermediate decoupling stage with a common gate structure and noise reduction inductors between the mixer and programmable gain stage, which reduces noise and power consumption, and decouples the mixer from the programmable gain stage, making the system independent of gain settings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If an I-Q mixer is directly coupled to a programmable gain stage in a Zero IF architecture, then the architecture is more efficient in power and area compared to multistage architectures, but noise increases and high-speed level shifters are required which increase power consumption

Engineering Contradiction:

Improvepower consumptionVSAvoidnoise

Core Design Contradiction:

Use of energy by stationary objectVSObject-affected harmful factors

Solution Approach 1:

A level shifter stage is inserted as an intermediary between the I-Q mixer and the programmable gain stage. This level shifter converts the differential output signals from the mixer to single-ended signals suitable for the programmable gain stage, enabling direct coupling while maintaining signal integrity and reducing noise compared to alternative approaches

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If high-speed level shifters are used to couple the mixer to the programmable gain stage, then direct up-conversion is enabled, but power consumption increases

Engineering Contradiction:

Improvesignal conversion speedVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The level shifter stage is designed to operate at high speeds by optimizing transistor sizing and biasing conditions. The circuit parameters such as gate voltages and current levels are carefully controlled to achieve fast signal transitions while minimizing dynamic power consumption through efficient switching operations

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the mixer is directly coupled to the programmable gain stage, then the architecture is simplified, but I-Q mismatch and local oscillator leakage become gain dependent

Engineering Contradiction:

Improvearchitecture complexityVSAvoidI-Q mismatch independence

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The level shifter stage acts as a buffer that isolates the I-Q mixer from the programmable gain stage. This intermediate stage prevents the gain variations in the programmable gain stage from affecting the mixer's I-Q balance and local oscillator leakage characteristics, making these parameters independent of the gain setting while maintaining architectural simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11374536B2Zero IF transmitter with decoupling between mixer and programmable gain stage

Publication Date: 2022.06.28 TEXAS INSTRUMENTS INC

AI summary

A system includes a Zero IF transmitter having a mixer and a programmable gain stage. The Zero IF transmitter also includes an intermediate stage between the mixer and the programmable gain stage, wherein the intermediate stage is configured to decouple the mixer and the programmable gain stage.