Back-Gate FET Phase Shifter for Low-Loss Radar Arrays

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Solution Overview

Problem

Current radar systems face limitations in achieving low loss and fine resolution phase shifting, particularly at radio frequency and millimeter wave ranges, due to high insertion loss, nonlinear harmonic generation, and size and switching speed issues with FET switches, which hinder their application in compact IC designs for vehicular systems.

Innovation Solution

The implementation of a field effect transistor (FET) based phase shifter that adjusts the effective capacitance of the drain-to-body and source-to-body nodes through a back-gate node, utilizing a gate bias source and a back gate bias source to modify the capacitance and phase of radar signals, thereby enabling low-loss and fine resolution phase shifting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If FET switches are used for phase shifting, then device size is reduced and integration is improved, but insertion loss increases and switching speed is limited

Engineering Contradiction:

Improvedevice sizeVSAvoidinsertion loss

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The patent replaces mechanical switching mechanisms with continuous electrical control through the back-gate voltage. Instead of using FET switches that mechanically open/close circuits, the invention uses the back-gate to continuously modulate the capacitance, thereby achieving phase shifting without the losses associated with switching operations. This substitution of switching mechanism with continuous control resolves the contradiction between compact size and insertion loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameter from discrete switching states to continuous capacitance modulation via back-gate voltage. By varying the back-gate voltage, the effective capacitance of the FET is continuously adjusted, enabling fine-resolution phase shifting without the high insertion loss inherent in traditional FET switching. This parameter change allows simultaneous achievement of compact integration and low loss.

Inventive Principle:

Principle #35Parameter changes

2Power

If FET size is increased to handle higher power, then power handling capability is improved, but additional matching networks are required and isolation problems increase

Engineering Contradiction:

Improvepower handling capabilityVSAvoidmatching networks and isolation

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent uses back-gate voltage to dynamically adjust the FET's capacitance parameter, enabling the same device to handle varying power levels without physical size changes. This continuous parameter modulation allows the FET to adapt to different power requirements while maintaining proper impedance matching, thereby avoiding the need for additional matching networks and isolation circuits that would increase device complexity.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If capacitor banks are used for phase shifting, then phase shifting capability is achieved, but process variation affects performance and fine-resolution tuning is difficult

Engineering Contradiction:

Improvephase shifting capabilityVSAvoidfine-resolution tuning

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces discrete capacitor bank switching with continuous back-gate voltage control. Instead of switching between fixed capacitance values that are susceptible to process variation, the back-gate voltage continuously modulates the effective capacitance, enabling fine-resolution phase tuning that is not limited by discrete capacitor steps or manufacturing tolerances. This substitution achieves both ease of operation and measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for efficient phase adjustment with reduced power dissipation and nonlinear harmonic generation, enabling high-frequency operation with improved resolution and compact design suitability for vehicular radar systems.

Implementation Method 1

adjusting an effective capacitance of drain-to-body and/or source-to-body through the back-gate node of FET

Methodology Applied

Scientific EffectCapacitance modulation: Capacitance

Implementation Method 2

adjust a phase of the alternating current radar signal in response to the first variable voltage applied to the gate and the second variable voltage applied to the back gate well control

Methodology Applied

Scientific EffectBack-gate effect:

Data Source

PatentUS11309870B2Field effect transistor (FET) configured to phase shift a radar signal using first and second variable voltages applied to a gate and a back gate of the FET

Publication Date: 2022.04.19 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

The present application relates to a method and apparatus for implementing a radar array including a gate bias source for providing a first variable voltage, a back gate well control for providing a second variable voltage, and a field effect transistor having a drain, a source, a gate and a back gate well control, the field effect transistor being further configured to couple an alternating current radar signal between the drain and the source and to adjust a phase of the alternating current radar in response to first variable voltage applied to the gate and the second variable voltage applied to the back gate well control.