RF Power Transistor Triode Mode Attenuation

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Solution Overview

Problem

Conventional radiofrequency transmission devices face issues with parasitic capacitances and noise introduction due to attenuator designs, which compromise signal adjustment and quality, especially in low-energy operations like Wi-Fi or Bluetooth Low Energy (BLE) transmissions.

Innovation Solution

The power transistor of the transmit stage is used in a triode mode as an adjustable resistor to attenuate reception signals, bypassing the limitations of traditional attenuators, and a controller adjusts the transistor's resistive value to achieve optimal attenuation without introducing noise, thereby optimizing component usage and reducing parasitic capacitances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional attenuator circuit with parallel resistors and switches is used in the receive stage, then adjustable signal attenuation is achieved, but large parasitic capacitances are introduced that compromise transformer adjustment and create signal distortion

Engineering Contradiction:

Improveadjustable signal attenuationVSAvoidparasitic capacitances

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The power transistor M1 is designed to perform dual functions: amplifying transmission signals during transmit mode and attenuating reception signals during receive mode. By controlling the gate voltage, the transistor operates in different regions (saturation for amplification, triode for attenuation), eliminating the need for separate attenuator components and their associated parasitic capacitances.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention changes the operating parameters of the power transistor by adjusting the gate voltage to control its region of operation. In the triode region, the transistor exhibits resistive behavior with controlled resistance value, enabling adjustable attenuation without introducing parasitic capacitances. This parameter-based control allows dynamic adjustment of attenuation levels while maintaining signal integrity.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If low noise amplifiers with degenerate gain are used to attenuate reception signals, then signal attenuation is achieved, but noise is introduced into the receive chain particularly in low-energy operation

Engineering Contradiction:

Improvesignal attenuation capabilityVSAvoidnoise introduction

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The power transistor M1, already present in the circuit for transmission amplification, is utilized to provide attenuation functionality during reception. This self-service approach eliminates the need for additional attenuator components that would introduce noise, particularly important in low-energy operations where noise floor is critical.

Inventive Principle:

Principle #25Self-service

3Object-generated harmful factors

If the power transistor is used in triode mode as an adjustable resistor for attenuation, then noise-free signal attenuation is achieved, but the transistor operates outside its typical amplification function

Engineering Contradiction:

Improvenoise reductionVSAvoidoperational flexibility

Core Design Contradiction:

Object-generated harmful factorsVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 adjustable signal attenuation without the constraints of traditional designs, improving signal quality and reducing noise, while efficiently using existing components in radiofrequency transmission devices.

Implementation Method 1

The placing of the power transistor in the triode mode comprises a delivering of a control voltage on the gate of the power transistor, obtained on the basis of the comparison between a benchmark voltage across the conduction terminals of a benchmark transistor and a model voltage across the terminals of a model resistive circuit.

Methodology Applied

Scientific EffectTriode mode operation: Electrical Resistance

Data Source

PatentUS10396736B2Attenuator device in a radio frequency transmission stage

Publication Date: 2019.08.27 STMICROELECTRONICS (GRENOBLE 2) SAS

AI summary

The transmission device comprising a transmit stage configured to deliver a transmission signal on an input-output node of an antenna and comprising a power transistor coupled to the input-output node and configured to amplify a signal to be transmitted. The device comprises a receive stage configured to receive a reception signal on the input-output node and comprising an attenuator circuit configured to attenuate the reception signal. The attenuator circuit comprising the power transistor and a control circuit able to place the power transistor in a triode mode.