Antenna Switch Circuit Harmonic Suppression via Transistor Body Control
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Solution Overview
Problem
Existing antenna switch circuits face challenges in achieving effective harmonic suppression while maintaining high isolation performance, often requiring additional space and increasing manufacturing costs due to the need for multiple resonant circuits or causing insertion loss by adding harmonic attenuation filters.
Innovation Solution
The antenna switch circuit incorporates a first and second switch circuit with transistors, voltage dividing circuits, and variable capacitor circuits, allowing for capacitance variation based on voltage, which enhances harmonic suppression without increasing size or cost by controlling the body of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a harmonic suppression function is added to a duplexer connected to the rear end of an antenna switch circuit, then harmonic attenuation performance is improved, but isolation performance requirements become difficult to meet and device complexity increases
Solution Approach 1:
The patent extracts the harmonic suppression function from the duplexer and relocates it to the antenna switch circuit itself. By adding a harmonic suppression circuit that includes a capacitor connected between the body terminal and source terminal of the transistor, the harmonic attenuation is achieved at the switch level rather than requiring the duplexer to handle both isolation and harmonic suppression functions simultaneously.
Solution Approach 2:
The antenna switch circuit is enhanced to perform multiple functions: signal switching and harmonic suppression. The transistor structure is utilized to provide both switching capability and harmonic attenuation by exploiting the body terminal's capacitance effect, thereby eliminating the need for separate harmonic suppression components in the duplexer path.
2Object-generated harmful factors
If a band stop resonant circuit is added to a duplexer transmit matching path to improve harmonic attenuation, then harmonic attenuation is improved, but additional space is required and manufacturing costs increase
Solution Approach 1:
The patent merges the harmonic suppression function with the existing antenna switch circuit structure. Instead of adding a separate band stop resonant circuit with inductors and capacitors, the invention utilizes the transistor's body terminal in conjunction with a capacitor to create the harmonic suppression effect, thereby combining multiple functions within the same circuit footprint.
Solution Approach 2:
The invention changes the operational parameters of the transistor by utilizing its body terminal capacitance. By connecting a capacitor between the body terminal and source terminal, the circuit exploits the voltage-dependent capacitance characteristics to achieve harmonic attenuation without requiring additional passive components that would increase space requirements.
3Object-generated harmful factors
If a low pass filter is added to the front end of the antenna switch circuit to provide harmonic attenuation, then harmonic attenuation function is improved, but insertion loss increases due to attenuation of necessary bands
Solution Approach 1:
The patent applies local quality by targeting harmonic suppression at a specific location within the circuit - the transistor body terminal region. Rather than using a broad-spectrum low pass filter that attenuates all frequencies including desired bands, the invention locally addresses harmonic frequencies through the body terminal capacitance mechanism, preserving signal integrity in the operating bands while suppressing harmonics.
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
This configuration effectively reduces leakage current and improves harmonic attenuation performance, achieving better harmonic suppression characteristics without the need for additional external elements or increased size, thus meeting tighter harmonic requirements within the same circuit size.
Implementation Method 1
a first variable capacitor circuit connected between a first voltage dividing circuit and a body of the first transistor, and having capacitance varying according to a voltage across opposite ends of the first variable capacitor circuit
Implementation Method 2
having capacitance varying according to a voltage across opposite ends of the first variable capacitor circuit
Implementation Method 3
a first voltage dividing circuit including a first resistor and a second resistor connected in series between a source of the first transistor and a drain of the first transistor
Data Source
AI summary
An antenna switch circuit includes: a first switch circuit connected between a first signal port for signal transmission and reception and an antenna port, and operated by a first gate signal; and a second switch circuit connected between a second signal port for signal transmission and reception and the antenna port, and operated by a second gate signal. The first switch circuit and/or the second switch circuit includes a first transistor and a second transistor connected in series between the first and second signal ports, a first voltage dividing circuit including a first resistor and a second resistor connected in series between a source and a drain of the first transistor, and a first variable capacitor circuit connected between the first voltage dividing circuit and a body of the first transistor, and having capacitance varying according to a voltage across opposite ends of the first variable capacitor circuit.