RF Switch Body Impedance Tuning for Better Linearity
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Solution Overview
Problem
Radio-frequency switches face challenges in reducing radiated spurious emissions (RSE) and maintaining linearity due to impedance mismatch between the antenna and switch, leading to increased voltage and harmonic degradation.
Innovation Solution
The implementation of a radio-frequency switch with a field-effect transistor (FET) having a coupling path with a diode and an adjustable impedance network between the FET's body and ground, which adjusts impedance based on frequency to reduce distortion and improve linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed impedance network is used in the radio-frequency switch, then the circuit complexity is reduced, but the linearity and radiated spurious emissions performance deteriorate due to impedance mismatch at different frequencies
Solution Approach 1:
The patent implements an adjustable impedance network where impedance values are dynamically changed based on the operating frequency. The network includes multiple impedance elements (resistors, capacitors, inductors) that can be selectively connected or disconnected to provide different impedance values at different frequency bands, thereby maintaining optimal linearity and reducing radiated spurious emissions across varying operating conditions.
Solution Approach 2:
The patent changes the impedance parameters of the network according to the operating frequency. By adjusting the impedance values in the network to match the specific frequency band being used, the system maintains proper impedance matching between the antenna and switch, preventing voltage degradation and harmonic distortion that would occur with fixed impedance values.
2Device complexity
If a simple fixed impedance network is used, then the device complexity is reduced, but radiated spurious emissions increase due to impedance mismatch
Solution Approach 1:
The adjustable impedance network dynamically adapts its impedance values based on the operating frequency band. This dynamic adjustment ensures that the impedance matching between the antenna and switch is optimized for each frequency band, thereby minimizing reflections and reducing radiated spurious emissions that would otherwise occur with a fixed impedance network.
Solution Approach 2:
The patent modifies the impedance parameters of the network to match the specific operating frequency. By changing the impedance values in response to frequency changes, the system prevents impedance mismatch conditions that lead to voltage degradation and increased radiated spurious emissions, maintaining clean signal transmission across different frequency bands.
3Device complexity
If impedance is not adjusted with frequency, then the device complexity is reduced, but linearity degrades due to voltage degradation and harmonic generation
Solution Approach 1:
The patent implements a frequency-dependent adjustable impedance network that maintains optimal impedance matching across different operating frequencies. By dynamically adjusting the impedance values based on the current frequency band, the network prevents voltage degradation and harmonic generation that would occur with fixed impedance values, thereby maintaining high linearity performance.
Solution Approach 2:
The impedance parameters of the network are changed according to the operating frequency to maintain proper impedance matching. This parameter adjustment prevents the voltage degradation and harmonic distortion that lead to linearity degradation, ensuring that the radio-frequency switch operates linearly across all frequency bands.
4Reliability
If an adjustable impedance network is implemented, then linearity and radiated spurious emissions performance are improved, but the device complexity increases
Solution Approach 1:
While the adjustable impedance network does increase device complexity compared to a fixed network, this complexity is necessary to achieve frequency-dependent impedance matching. The network includes multiple impedance elements that can be selectively connected to provide different impedance values at different frequencies, enabling the system to maintain optimal linearity and reduce radiated spurious emissions across varying operating conditions.
Solution Approach 2:
The patent employs parameter changes in the impedance network to match the operating frequency, which improves linearity and reduces radiated spurious emissions. Although this approach increases device complexity compared to fixed impedance solutions, the performance benefits in terms of signal integrity and emission control make the added complexity justified.
Data Source
AI summary
A process for fabricating a semiconductor die involves providing a semiconductor substrate, forming a first field-effect transistor on the semiconductor substrate, the first field-effect transistor having a source, a drain, a gate, and a body, forming a coupling path that couples the body of the first field-effect transistor to the gate of the first field-effect transistor, the coupling path including a diode, and forming an adjustable impedance network coupled between the body of the first field-effect transistor and a ground reference, the adjustable impedance network being configured to reduce radio-frequency distortion in the first field-effect transistor.