Active Circulator Bias Circuit with RF Chokes
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Solution Overview
Problem
Existing active circulators suffer from significant DC and RF power loss due to resistors in the DC bias circuit, which limits the maximum RF voltage swing and power handling capability, and are not energy efficient.
Innovation Solution
The active circulator design separates the DC and RF paths using choke inductors and bypass capacitors, eliminating resistors in the DC bias circuit to prevent power loss, allowing maximum RF voltage swing without DC power consumption through resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drain resistors and common ground resistor are used in the DC bias circuit, then the FET transistors can be biased properly, but significant DC power consumption and RF power loss occur
Solution Approach 1:
The patent removes the resistive elements (drain resistors and common ground resistor) from the DC bias circuit entirely. Instead of using resistors to establish bias, the invention uses direct DC voltage connections to the FET drains and sources, extracting the harmful resistive components that cause power consumption while maintaining the necessary biasing function through alternative means.
Solution Approach 2:
The patent introduces RF chokes (inductors) as intermediary elements in the bias circuit. These chokes provide DC current paths while blocking RF signals, serving as mediators between the DC bias voltage sources and the FET terminals. This allows proper DC biasing without creating significant voltage drops or power losses that would occur with resistive elements.
2Reliability
If drain resistors and common ground resistor are used, then DC bias can be established, but maximum RF voltage swing is limited due to voltage drops across resistors
Solution Approach 1:
The patent extracts the limiting resistive elements from the circuit, removing the source of voltage drops that constrain RF voltage swing. By eliminating drain resistors and common ground resistors, the full DC supply voltage can be utilized for RF signal swings without being reduced by resistive voltage drops, thereby maximizing the available voltage swing range.
Solution Approach 2:
RF chokes are introduced as intermediary components that provide DC current paths with minimal RF impedance. These chokes act as mediators that allow DC bias currents to flow while presenting high impedance to RF signals, preventing RF voltage drops across the biasing elements and preserving maximum RF voltage swing capability.
3Reliability
If high value drain resistors are used to block RF signal, then RF isolation is achieved, but significant RF power loss occurs across the resistors
Solution Approach 1:
The patent substitutes resistive RF blocking mechanisms with inductive RF choking mechanisms. Instead of using high-value resistors to block RF signals (which dissipate power), the invention uses RF chokes (inductors) that block RF signals through their inductive reactance without dissipating significant power, replacing a resistive system with an inductive system.
Solution Approach 2:
The patent changes the fundamental parameter used for RF blocking from resistance to inductance. By using components with high inductive reactance at RF frequencies rather than high resistance, the circuit achieves the same RF isolation function with dramatically reduced power loss, as inductive reactance does not dissipate power like resistance does.
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 design enhances power handling capability and energy efficiency by maintaining good insertion loss and isolation up to higher input driving powers, significantly improving upon prior art circulators.
Implementation Method 1
The drain bias voltages are connected to the drains of the FET transistors through the choke inductors of the RF chokes. The bypass capacitors of the RF chokes are connected in parallel with the choke inductors.
Implementation Method 2
The bypass capacitors of the RF chokes are connected in parallel with the choke inductors.
Data Source
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AI summary
A multi-port active circulator where each of a plurality of FET transistors has (i) a gate connected to an associated port of the multi-port active circulator via a capacitor of an associated one of a plurality of first RF chokes, each of the first RF chokes being connected to a gate of an associated FET transistor of said plurality of transistors, the associated port of said associated FET transistor and to a power supply bias connection; (ii) a source connected to a common point; and (iii) a drain connected to the gate of the same FET transistor by a feedback circuit and connected to the gate of a neighboring FET transistor via a capacitor of one of a plurality of second RF chokes, each of which coupling gates and drains of neighboring FET transistors via capacitors thereof and being connected to another power supply bias connection.