Millimeter Waveband Switch Isolation via Wavelength Transmission Lines
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Solution Overview
Problem
Conventional millimeter waveband switches achieve improved isolation but incur increased passing loss due to the on-resistance of the switching element when the switch is on.
Innovation Solution
A millimeter waveband switch design featuring a first switching element connected in series between input and output terminals, with a ½ wavelength transmission line connected in parallel, and a second transmission line of ¼ wavelength connected between the switching element and ground, allowing for high isolation without increasing passing loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching elements are arranged in parallel to improve isolation, then isolation characteristic is improved, but passing loss increases due to on-resistance
Solution Approach 1:
A ½ wavelength transmission line is introduced as an intermediary component between the switching element and the signal path. This transmission line transforms the impedance characteristics, allowing the switching element's on-resistance to be effectively masked or transformed, thereby reducing its impact on passing loss while maintaining isolation performance when the switch is off.
Solution Approach 2:
The patent changes the electrical parameters of the transmission line (specifically setting its length to ½ wavelength) to achieve impedance transformation. This parameter change allows the system to achieve both high isolation and low passing loss by transforming the effective impedance seen by the signal, thereby resolving the contradiction between isolation and passing loss.
2Reliability
If inductance is arranged in series to achieve high isolation, then isolation characteristic is improved, but passing loss increases
Solution Approach 1:
The ½ wavelength transmission line serves as an intermediary that replaces the need for series inductance. By transforming the impedance through the transmission line, the patent achieves high isolation without introducing additional lossy inductive components in series with the signal path.
Solution Approach 2:
The patent substitutes the mechanical/physical approach of using series inductance with an electromagnetic field-based approach using a ½ wavelength transmission line. This substitution achieves the same isolation effect but with lower energy loss, as the transmission line approach better matches the high-frequency millimeter waveband operating conditions.
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 enhances isolation characteristics while maintaining low passing loss, as demonstrated by frequency characteristic calculations, particularly on the 77 GHz band, and can be adjusted for desired frequency bands using GaAs-FET, GaN-FET, or HBT.
Implementation Method 1
a first transmission line having an electric length of 1⁄2 wavelength which is connected in parallel to the first switching element
Implementation Method 2
a second transmission line having an electric length of 1⁄4 wavelength which is connected between a ground and another end of a parallel circuit including the first switching element and the first transmission line
Data Source
AI summary
A millimeter waveband switch which enables high isolation without increasing passing loss, includes a first switching element that is connected in series between input and output terminals through which a signal passes; and a first transmission line having an electrical length of ½ wavelength and which is connected in parallel with the first switching element. Alternatively, the millimeter waveband switch may include: a first switching element having a first end connected in parallel to input and output terminals through which a signal passes; a first transmission line having an electrical length of ½ wavelength which is connected in parallel with the first switching element; and a second transmission line having an electrical length of ¼ wavelength and which is connected between aground and a second end of her first switching element.