Multi-band SPNT Switch with Variable Quarterwave Transmission Lines
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Solution Overview
Problem
Conventional Single Pole N Throw (SPNT) switches are limited to single-frequency operation due to the fixed physical length of quarterwave transmission lines, which leads to performance degradation and signal leakage when used across multiple frequency bands.
Innovation Solution
A parallel matrix SPNT switch configuration with multiple transmission lines connected to a common terminal, where SPST switches are used to ground transmission lines, allowing them to operate as open nodes at different frequencies, and variable quarterwave transmission lines are used to maintain impedance matching across multiple bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed physical length quarterwave transmission lines are used in SPNT switch, then single-frequency operation is achieved, but multi-band functionality is degraded
Solution Approach 1:
The patent applies dynamics by making the transmission line length adjustable rather than fixed. The variable transmission line allows the electrical length to be changed dynamically to match quarterwave at different frequency bands, enabling the switch to maintain proper impedance transformation and isolation performance across multiple frequencies. This resolves the contradiction by allowing the system to adapt its physical characteristics to different operating conditions.
Solution Approach 2:
The patent changes the parameter of transmission line length to enable multi-band operation. By adjusting the physical length of the transmission line, the system can maintain the quarterwave electrical length at different frequency bands, thereby preserving isolation performance while achieving multi-band functionality. This parameter adjustment allows the same hardware to operate reliably across multiple frequency ranges.
2Adaptability or versatility
If variable transmission line length is used to achieve multi-band operation, then frequency adaptability is improved, but maintaining impedance matching becomes more complex
Solution Approach 1:
The variable transmission line structure allows dynamic adjustment of the electrical length to maintain quarterwave at different frequencies. This dynamic capability enables the system to automatically maintain proper impedance transformation ratios across multiple frequency bands without requiring complex external impedance matching networks for each band, thereby reducing overall system complexity despite the variable length requirement.
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
Enables efficient multiplexing and demultiplexing of multi-band signals with improved isolation and reduced insertion loss across various frequency bands, allowing for the extension of SPNT switch functionality to multi-band frequencies without signal leakage.
Implementation Method 1
the SPST switch of off-path is configured as the switch element combined with a quarterwave (λ/4) transmission line (TL). This makes the impedance seen looking into the SPST switch of off-path open
Implementation Method 2
the on-path should minimize the insertion loss of the input signal by matching the characteristic impedance of the input and output terminals
Data Source
AI summary
Provided is a Single Pole N Throw (SPNT) switch including: a transmission line unit including a plurality of transmission lines each connected between a plurality of selection terminals and a single common terminal; and a SPST switch unit including a plurality of SPST switches for grounding each of the plurality of transmission lines, wherein the SPST switches allows at least a part of the plurality of transmission lines and other transmission lines to operate as open nodes at the common terminal for different frequencies.