Active Lumped Element Circulator Using Microwave Amplifiers

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Solution Overview

Problem

Conventional ferrite-based RF circulators and isolators are expensive, narrow-band, bulky, and impractical for integration onto monolithic substrates, and discrete non-ferrite solutions do not perform well at higher frequencies.

Innovation Solution

An integrated circuit with a semiconductor substrate featuring a lumped element active circulator comprising three ports and microwave operational amplifiers, configured to pass signals between ports while isolating them from each other, emulating ferrite circulator functionality without discrete components and ferrite materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferrite-based circulators are used, then non-reciprocal signal isolation is achieved, but the device becomes bulky, expensive, and narrow-band

Engineering Contradiction:

Improvesignal isolationVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent replaces ferrite-based magnetic field control mechanisms with electronic operational amplifiers and feedback circuits. The active electronic components substitute for the passive ferrite material, enabling non-reciprocal signal isolation through electronic gain control and feedback rather than magnetic permeability manipulation. This substitution dramatically reduces device size while maintaining isolation functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the operating parameters from magnetic field-dependent ferrite properties to electrically-controlled amplifier gain and feedback loop characteristics. By using active electronic components with可调 gain and bandwidth, the device achieves broader frequency operation compared to narrow-band ferrite resonators, while maintaining signal isolation through electronic rather than magnetic mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If ferrite-based circulators are used, then non-reciprocal signal isolation is achieved, but integration onto monolithic substrates becomes impractical

Engineering Contradiction:

Improvesignal isolationVSAvoidintegration capability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent merges multiple discrete functional elements (signal paths, isolation mechanisms, and control circuits) into a single integrated circuit implementation. The operational amplifiers and feedback networks are combined on a monolithic substrate, creating a compact circulator that integrates transmission and isolation functions in one device rather than requiring separate ferrite components and waveguide structures.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The replacement of ferrite materials with semiconductor-based operational amplifiers enables monolithic integration. The electronic active components can be fabricated using standard integrated circuit processes, allowing the entire circulator to be manufactured on a single chip, whereas ferrite-based devices require separate magnetic material processing and assembly.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If discrete non-ferrite solutions are used, then cost and size are reduced, but performance at higher frequencies deteriorates

Engineering Contradiction:

Improvedevice sizeVSAvoidhigh-frequency performance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The invention optimizes the operational amplifiers for high-frequency operation by selecting devices with sufficient unity-gain bandwidth and adjusting feedback network parameters accordingly. The active electronic components are chosen and configured to maintain gain and phase characteristics suitable for RF and microwave frequencies, overcoming the traditional limitation of discrete non-ferrite solutions at higher frequencies.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The integrated active circulator design provides universal functionality across a broad frequency range, unlike narrow-band ferrite devices optimized for specific frequencies. The electronic feedback mechanism can be designed to maintain isolation and signal transmission performance across wide bandwidths, making the device suitable for multiple frequency applications without requiring frequency-specific ferrite resonator designs.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9197170B2Active lumped element circulator

Publication Date: 2015.11.24 VIASAT INC

AI summary

An integrated circuit can comprise: a first port, a second port, and a third port; and a plurality of microwave operational amplifiers coupled to each other and the first port, the second port, and the third port. The plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the first port to the second port while substantially isolating the signal provided to the first port from the third port; the plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the second port to the third port while substantially isolating the signal provided to the second port from the first port; and the plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the third port to the first port while substantially isolating the signal provided to the third port from the second port.