Multi-band CMOS Transmit-Receive Switch with LC Resonant Tuning
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Solution Overview
Problem
Existing transmit-receive switches using CMOS FETs in the GHz range face performance shortcomings, including a reduced 1 dB input compression point and excessive insertion loss, and fail to provide wide frequency operation and integration with external elements.
Innovation Solution
A monolithic transmit-receive switch utilizing CMOS FETs with floating substrates and LC resonant circuits, enabling high coupling during transmit intervals and low insertion loss during receive intervals, with CMOS FETs configured to operate in both high and low frequency bands through selective switching and tuning structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMOS FETs are used in the GHz range, then integration and manufacturing cost are improved, but 1 dB input compression point is reduced and insertion loss increases
Solution Approach 1:
The patent divides the TR switch into multiple independent CMOS FETs (first FET for transmit path, second FET for receive path, third FET for isolation) rather than using a single device. This segmentation allows each FET to be optimized for its specific function, improving overall performance while maintaining CMOS integration benefits.
Solution Approach 2:
The patent combines multiple CMOS FETs with different substrate configurations (first substrate for transmit FET, second substrate for receive FET, third substrate for isolation FET) to create a composite structure that achieves both integration and high performance. This composite approach allows simultaneous optimization of compression point and insertion loss.
2Ease of manufacture
If CMOS FETs are used in the GHz range, then integration is improved, but insertion loss increases
Solution Approach 1:
The patent applies different substrate configurations to different FETs based on their specific functional requirements. The first FET has its first substrate connected to ground, the second FET has its second substrate connected to ground, and the third FET has its third substrate connected to ground. This localized optimization minimizes insertion loss in each path while maintaining overall integration.
Solution Approach 2:
The patent introduces a third FET with its drain connected to the transmit port and source connected to the receive port, acting as an intermediary isolation element. This intermediary FET prevents signal leakage and reduces insertion loss by providing proper isolation between transmit and receive paths.
3Adaptability or versatility
If external elements are combined, then frequency operation range is improved, but device complexity increases
Solution Approach 1:
The patent designs the TR switch to perform multiple functions using the same basic CMOS FET structure. The same three-FET topology can operate across wide frequency ranges by adjusting external LC resonant circuit parameters, eliminating the need for different device structures for different frequency bands and reducing overall complexity.
Solution Approach 2:
The patent enables wide frequency operation by changing the parameters of external LC resonant circuits rather than modifying the internal FET structure. The first LC resonant circuit and second LC resonant circuit can be tuned to different frequencies, allowing the same CMOS TR switch design to operate across multiple frequency bands without increasing device complexity.
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 achieves improved 1 dB compression point and reduced insertion loss, enabling efficient operation across multiple frequency bands with minimal parasitic effects, enhancing the performance of wireless transceivers by integrating baseband and RF processing on a single CMOS integrated circuit.
Implementation Method 1
The switches may be arranged with an LC resonant circuit to provide high coupling from a transmit port to an antenna port and high isolation from transmit port to receive port during a transmit interval, and during a receive interval, a low insertion loss from an antenna port to a receiver port
Implementation Method 2
A transmit-receive switch which uses CMOS FETs, has two or more ranges of operation, and provides both low insertion loss and an improved 1 dB compression point
Data Source
AI summary
A transmit-receive switch has a transmit port, an antenna port, and a receive port. A first switch couples the transmit port to the antenna port when a signal TxON is asserted. A LOW_BAND signal indicates the selection of a lower band of frequencies. A tuning structure is formed by a second and third switch in series which couple the antenna port to ground through a first capacitor when TxON and LOW_BAND are both asserted, and LOW_BAND may be provided to one or more such tuning structures for multi-band frequency operation. A second capacitor couples the antenna port to ground when a fourth switch is enabled. An inductor couples the antenna port to the receive port. A third capacitor is placed across the receive port and ground. A fifth switch is closed when TxON is asserted. The first through fifth switches can be a CMOS FET with an isolated substrate coupled to ground through an associated resistor.