RF Amplifier Shunt Resonant Circuit for Antiresonance Suppression
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Solution Overview
Problem
Existing radio frequency amplifiers experience increased intermodulation distortion and efficiency loss due to antiresonance and impedance issues when dealing with wide bandwidths and varying difference frequencies, particularly when multiple circuits with different resonant frequencies are used.
Innovation Solution
A radio frequency amplifier design incorporating a shunt circuit with first and second series resonant circuits connected by a resistor, which reduces impedance at difference frequencies by inhibiting antiresonance, maintaining efficiency and linearity over a wide bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple series resonant circuits with different resonant frequencies are combined to reduce difference frequency impedance over wide bandwidth, then the impedance reduction effect is improved, but antiresonance occurs at frequencies between adjacent resonant frequencies resulting in high impedance bands that worsen intermodulation distortion
Solution Approach 1:
A shunt circuit is introduced as an intermediary element between the multiple series resonant circuits. This shunt circuit, connected to ground, acts as a mediator that suppresses the antiresonance phenomenon occurring between adjacent resonant frequencies. By providing a controlled impedance path to ground at the antiresonance frequencies, the shunt circuit prevents the formation of high impedance bands, thereby eliminating the harmful effect on intermodulation distortion while preserving the impedance reduction effectiveness of the series resonant circuits.
Solution Approach 2:
The invention modifies the impedance parameters of the matching circuit by carefully selecting the resonant frequencies of multiple series resonant circuits to target specific difference frequencies. Additionally, the shunt circuit's impedance characteristics are optimized to specifically counteract antiresonance effects. This parameter optimization allows the circuit to maintain low impedance at difference frequencies while preventing high impedance formation at intermediate frequencies, thus resolving the contradiction between impedance reduction and intermodulation distortion.
2Reliability
If a resistor is connected in series to a difference frequency impedance reduction circuit to prevent antiresonance, then the antiresonance is suppressed, but the resistor converts amplified radio frequency signal into heat causing decrease in amplifier efficiency
Solution Approach 1:
The shunt circuit serves as an intermediary that suppresses antiresonance without requiring series resistors. By providing a parallel path to ground with optimized impedance characteristics, the shunt circuit absorbs the antiresonance energy without converting it to heat through resistive dissipation. This approach achieves antiresonance suppression while minimizing energy loss, thereby maintaining amplifier efficiency.
Solution Approach 2:
Instead of using resistive damping that dissipates energy, the invention employs reactive impedance elements (inductors and capacitors) in the shunt circuit that copy or replicate the impedance suppression effect without the energy loss mechanism. The reactive elements store and release energy cyclically, achieving the same antiresonance suppression function as resistors would provide, but without converting RF signals into heat.
3Device complexity
If bias voltage is shared through the inductor and transmission line of the series resonant circuit, then circuit complexity is reduced, but voltage drop occurs causing increased power consumption and deterioration of radio frequency properties
Solution Approach 1:
The invention segments the bias voltage supply path from the series resonant circuit. Instead of sharing the bias voltage through the inductor and transmission line, a separate bias supply path is provided. This segmentation eliminates the voltage drop issue caused by current flow through the resonant circuit elements, thereby reducing power consumption and preserving RF properties, while the overall circuit complexity remains manageable through systematic design.
Solution Approach 2:
A separate bias supply path acts as an intermediary channel that delivers bias voltage directly to the series resonant circuit without requiring current flow through the inductor and transmission line. This intermediary path prevents voltage drop and associated power loss, while maintaining the simplified circuit structure by using dedicated biasing components rather than complex voltage regulation circuits.
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 design achieves low intermodulation distortion and high efficiency by stabilizing impedance across a wide bandwidth, reducing impedance at difference frequencies without significant insertion loss.
Implementation Method 1
a first series resonant circuit that is connected between a node and the ground, includes a first inductor element and a first capacitor element that are connected in series, and has a first resonant frequency
Implementation Method 2
reduces the impedance at difference frequencies over a wide bandwidth
Implementation Method 3
a first impedance element that is connected between a first connection point and a second connection point and includes a resistance component
Data Source
AI summary
A radio frequency amplifier includes: a transistor; an input line; an output line; and a shunt circuit that is connected between ground and the input line or the output line, wherein the shunt circuit includes: a first series resonant circuit that includes an inductor and a capacitor that are connected in series and has first resonant frequency f1; a second series resonant circuit that includes an inductor and a capacitor that are connected in series and has second resonant frequency f2 that is different from the first resonant frequency; and a resistor that is connected between a first connection point and a second connection point, the first connection point being a connection location between the inductor and the capacitor in the first series resonant circuit, the second connection point being a connection location between the inductor and the capacitor in the second series resonant circuit.