Tunable Filter With Variable Capacitors For Multi-Band RF Front-Ends
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Solution Overview
Problem
In wireless communication technology, tunable filters used in RF front-end circuits face challenges in reducing circuit area and complexity while maintaining performance, especially with the need for multi-channel and multi-band communication systems, and the requirement for lighter, smaller wireless communication devices, where existing solutions do not effectively adjust center frequency and quality factor within a larger frequency range without increasing insertion loss.
Innovation Solution
A tunable filter design featuring serially connected inductors in parallel with capacitors, with mutual induction and variable capacitors, allowing for adjustment of center frequency and quality factor, and using 3D inductor structures to minimize loss, and variable coupling capacitors to maintain bandwidth and reduce insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple filters are used in multi-channel and multi-band communication systems to achieve more data throughput and faster transmission speed, then the data throughput and transmission speed are improved, but the circuit area and circuit complexity increase
Solution Approach 1:
The patent combines multiple filter functions into a single tunable filter that can operate across multiple bands and channels. The filter uses shared inductors and capacitors with tuning mechanisms that allow it to dynamically switch between different frequency bands, eliminating the need for separate physical filters for each band and thereby reducing circuit complexity while maintaining multi-band capability
Solution Approach 2:
The tunable filter is designed to perform multiple functions by covering multiple frequency bands (e.g., LTE bands 3, 7, 20, 28) and communication standards within a single device. The filter's resonant frequency can be adjusted to match different band requirements, making it a universal solution that replaces multiple specialized filters
2Adaptability or versatility
If the filter is designed to operate across a larger frequency range to accommodate multi-band communication, then the adaptability is improved, but the quality factor and bandwidth control become more difficult
Solution Approach 1:
The filter employs dynamic tuning mechanisms including variable capacitors and adjustable inductors that allow the resonant frequency to be changed in real-time. This dynamic adjustment capability enables the filter to maintain optimal quality factor across different frequency bands by reconfiguring the LC tank circuits to match the desired operating frequency
Solution Approach 2:
The filter uses parameter adjustment through variable capacitors and inductors to change the resonant frequency and bandwidth characteristics. By varying the capacitance and inductance values, the filter can be tuned to different frequency bands while maintaining the required quality factor, effectively managing the trade-off between frequency range and quality factor control
3Adaptability or versatility
If variable capacitors are used to adjust the center frequency within a larger frequency range, then the frequency tuning range is improved, but the insertion loss may increase
Solution Approach 1:
The patent combines multiple LC tank circuits with shared inductors to create a more efficient tuning structure. By sharing high-quality-factor inductors across multiple tuning configurations and using capacitor arrays for frequency selection, the design achieves wide frequency tuning while minimizing the number of discrete components that would each contribute to insertion loss
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 enables flexible frequency tuning within a larger range while maintaining low insertion loss and return loss, ensuring the tunable filter operates effectively across different frequencies with minimal increase in insertion loss and maintaining a fractional bandwidth of 10% and return loss less than -15 dB.
Implementation Method 1
A mutual induction is generated between the first inductor and the second inductor
Data Source
AI summary
A tunable filter includes a first circuit and a second circuit. In both of them, the first inductor and the second inductor are connected in serial, and further connected with the first capacitor in parallel. The first end of the second capacitor is connected between the first inductor and the second inductor, and the second end of the second capacitor is grounded. The first end of the first capacitor of the first circuit is coupled to the input end of the tunable filter through a first coupling capacitor. The second end of the first capacitor of the first circuit is coupled to the first end of the first capacitor of the second circuit through a second coupling capacitor. The second end of the first capacitor of the second circuit is coupled to the output end of the tunable filter through a third coupling capacitor.