Multi-Gain LNA Source Degeneration Using Switchable Shunt Capacitors

Solution Overview

Problem

Existing multi-gain low noise amplifiers (LNAs) with inductive source degeneration face challenges in size, cost, and noise figure performance due to the need for large inductors and switches, which impact sensitivity and input matching.

Innovation Solution

A tunable degeneration network using a fixed inductor and switchable shunting capacitors is implemented, allowing for multiple gain modes without the need for multiple inductors, thereby reducing size and cost while maintaining noise figure performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple inductors are used to provide different gain modes, then multi-gain functionality is achieved, but device size and cost increase

Engineering Contradiction:

Improvemulti-gain functionalityVSAvoiddevice size

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent changes the parameter from inductance to capacitance by using switchable capacitors instead of switchable inductors. The capacitors are connected in parallel with a fixed inductor, and by switching different capacitor values, the effective inductance seen by the circuit is changed, enabling multi-gain functionality without requiring multiple physical inductors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces capacitors as intermediary elements that mediate between the fixed inductor and the circuit. These capacitors, when switched in parallel with the inductor, modify the effective impedance without requiring direct switching of the inductor itself, thus achieving gain control with fewer magnetic components.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple inductors are used to provide different gain modes, then multi-gain functionality is achieved, but manufacturing cost increases

Engineering Contradiction:

Improvemulti-gain functionalityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent changes the parameter from inductance to capacitance by using switchable capacitors instead of switchable inductors. The capacitors are connected in parallel with a fixed inductor, and by switching different capacitor values, the effective inductance seen by the circuit is changed, enabling multi-gain functionality without requiring multiple physical inductors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent merges the functions of multiple inductors into a single fixed inductor combined with switchable capacitors. Instead of having separate inductors for each gain mode, the solution combines one inductor with multiple capacitors that can be switched to achieve different effective inductance values, reducing component count and manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If large inductors are used for inductive source degeneration, then noise figure performance is maintained, but device size and parasitic effects increase

Engineering Contradiction:

Improvenoise figure performanceVSAvoidinductor size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent changes the parameter from inductance to capacitance by using switchable capacitors instead of switchable inductors. The capacitors are connected in parallel with a fixed inductor, and by switching different capacitor values, the effective inductance seen by the circuit is changed, enabling multi-gain functionality without requiring multiple physical inductors.

Inventive Principle:

Principle #35Parameter changes

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

The solution provides a compact, cost-effective multi-gain LNA with improved noise figure and sensitivity by using a single smaller inductor and switchable capacitors to achieve various gain modes, enhancing broadband frequency response stability and reducing parasitic capacitance effects.

Implementation Method 1

a first switchable shunting network connected between the first terminal and the second terminal, the first switchable shunting network comprising: a first switch in series connection with a first capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a parallel combination of the fixed inductance inductor and the first capacitor results in a first parallel combined inductive impedance that is larger than an inductive impedance of the fixed inductance inductor

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20240171145A1Tunable Effective Inductance for Multi-Gain LNA with Inductive Source Degeneration

Publication Date: 2024.05.23 PSEMI CORP

AI summary

A multi-gain LNA with inductive source degeneration is presented. The inductive source degeneration is provided via a tunable degeneration network that includes an inductor in parallel with one or more switchable shunting networks. Each shunting network includes a shunting capacitor that can selectively be coupled in parallel to the inductor. A capacitance of the shunting capacitor is calculated so that a combined impedance of the inductor and the shunting capacitor at a narrowband frequency of operation is effectively an inductance. The inductance is calculated according to a desired gain of the LNA. According to one aspect, the switchable shunting network includes a resistor in series connection with the shunting capacitor to provide broadband frequency response stability of the tunable degeneration network. According to another aspect, the LNA includes a plurality of selectable branches to further control gain of the LNA.