RF Bias Circuit Resonators for Wideband Baseband Impedance
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Solution Overview
Problem
In radio frequency transistor circuits, the λ/4 transmission line used for biasing limits the baseband frequency to about 1/100 of the radio frequency signal, making it difficult to reduce impedance in the baseband and thereby causing signal distortion.
Innovation Solution
A radio frequency circuit design that includes a power supply path with a series connection of first and second inductors, a first resonator with a third inductor and capacitor, a second resonator with a capacitor and resistor, and a third resonator with a capacitor connected in parallel, to resonate at specific frequencies and suppress impedance peaks, thereby reducing baseband impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a λ/4 transmission line is used for the power supply path to obtain high impedance at radio frequency, then the radio frequency signal is isolated from the power supply path, but the impedance at baseband frequency cannot be lowered and the baseband is limited to about 1/100 of the radio frequency signal
Solution Approach 1:
The power supply path is segmented into multiple sections with different impedance characteristics. The λ/4 transmission line provides high impedance for RF isolation, while additional LC circuits are inserted to create low-impedance paths for baseband frequencies, allowing each segment to handle different frequency ranges independently
Solution Approach 2:
Different impedance characteristics are applied to different frequency bands within the same power supply path. The circuit structure provides high impedance specifically at RF frequencies while maintaining low impedance at baseband frequencies, achieving frequency-selective impedance control
2Reliability
If a λ/4 transmission line is used for the power supply path, then high impedance is obtained at radio frequency, but the impedance at baseband frequency (several tens of MHz to several hundreds of MHz) cannot be lowered causing signal distortion
Solution Approach 1:
LC circuits are introduced as intermediary elements in the power supply path. These circuits act as mediators that provide low-impedance paths for baseband signals while maintaining the high-impedance characteristics of the λ/4 transmission line for RF signals, thereby reducing signal distortion without compromising RF isolation
3Object-affected harmful factors
If the impedance at baseband is lowered to reduce signal distortion, then signal quality improves, but the λ/4 transmission line structure prevents this from being achieved
Solution Approach 1:
The invention merges the λ/4 transmission line structure with additional LC circuits in the power supply path. This combination allows the circuit to simultaneously provide RF isolation through the transmission line and low baseband impedance through the LC circuits, achieving both goals without requiring completely separate paths
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 effectively reduces baseband impedance over a wideband frequency, enhancing signal quality and reducing distortion by controlling resonance frequencies and impedance peaks.
Implementation Method 1
a first resonator that includes a third inductor and a first capacitor connected in series to the third inductor, and that resonates at a series resonance frequency corresponding to an inductance of the third inductor and a capacitance of the first capacitor
Data Source
AI summary
A radio frequency circuit has an amplifier that amplifies an input radio frequency signal, a power supply path that is disposed between an output node of the amplifier and a power supply node to which a DC bias voltage is supplied, and includes a first inductor and a second inductor connected in series, a first resonator that comprises a third inductor and a first capacitor connected in series to the third inductor, and resonates at a series resonance frequency, a second resonator that resonates at a series resonance frequency corresponding to an inductance of the first inductor, a capacitance of the second capacitor, and a resistance value of the first resistor, and a third resonator that comprises a third capacitor connected in parallel with the second inductor, and resonates at a parallel resonance frequency corresponding to a capacitance of the third capacitor and an inductance of the second inductor.