Variable Attenuator Suppressing Harmonic Distortion
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Solution Overview
Problem
Existing high frequency variable attenuators using PIN diodes suffer from distortion and restricted formation regions, leading to degraded IMD characteristics and harmonic distortion when handling high power signals.
Innovation Solution
A variable attenuator configuration utilizing a switch circuit with resistors and a variable reactance portion, such as a variable capacitor without a diode structure, allows for adjustable impedance and suppression of harmonic distortion, enabling simple and effective attenuation without generating harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PIN diodes are used in a variable attenuator, then attenuation can be adjusted by changing resistance, but distortion is generated in the I layer and IMD characteristics are degraded
Solution Approach 1:
The patent changes the fundamental parameter of the variable element from a PIN diode (semiconductor device with distortion) to a capacitor (electrical component without distortion). By adjusting the capacitance value of the variable capacitor, the attenuation characteristic is changed without generating the distortion that occurs in PIN diodes when the I layer is depleted under high frequency signals.
2Ease of operation
If a 90° hybrid circuit is used for variable attenuation, then attenuation can be controlled, but the formation region is restricted
Solution Approach 1:
The patent segments the attenuator into multiple discrete resistance values (R1, R2, R3, R4) that can be independently selected by a switch circuit. This segmentation allows the formation region to be extended because each resistance can be optimized independently, and the switch circuit can be implemented using simple semiconductor switches rather than requiring a complex 90° hybrid circuit structure.
3Adaptability or versatility
If multiple resistance values are provided with switch circuit, then types of impedance capable of being realized are increased, but device complexity increases
Solution Approach 1:
The patent implements a dynamic switch circuit that can selectively connect different capacitors (C1, C2, C3, C4) to ground, thereby dynamically changing the impedance characteristics. The switch circuit uses simple semiconductor switches (such as MOSFETs or BJTs) controlled by digital signals, which provides adaptability for multiple impedance types while keeping the device complexity low compared to analog control 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 solution effectively suppresses high harmonic distortion and allows for easy realization of variable attenuators with improved electric power handling capability and desired impedance types, enhancing noise cancel effects in high frequency circuits.
Implementation Method 1
The variable reactance portion is configured of a variable capacitor that does not have a diode structure
Data Source
AI summary
An attenuator includes a first high frequency signal input-output terminal and a second high frequency signal input-output terminal, a switch circuit, a plurality of resistors, and a variable capacitor. The plurality of resistors are respectively connected to the first high frequency signal input-output terminal while the resistors being parallel to each other. The switch circuit includes a plurality of selection target terminals respectively connected to the resistors and a shared terminal to which the plurality of selection target terminals are selectively connected and which is connected to the second high frequency signal input-output terminal. The variable capacitor is connected to one of the resistors in series and is so constituted as to have not a diode structure.