Varactor-Tuned Silicon Duplexer With Fewer Resonant Sections
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Solution Overview
Problem
Existing duplexers in wide bandwidth systems, such as CDMA, require numerous cascaded sections to achieve sufficient bandwidth and isolation, leading to complex designs and high component counts, which are costly and inefficient.
Innovation Solution
A tunable duplexer circuit implemented on a single silicon chip with electronically tunable bandpass filters using varactors, allowing for adjustable capacitance and reduced resonant sections, along with a calibration circuit for precise tuning of center frequency, pass band, and stop band performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If nontunable duplexers use many cascaded resonant sections to achieve wide bandwidth, then the pass band bandwidth is sufficient, but the device complexity and component count increase significantly
Solution Approach 1:
The patent applies dynamics by making the resonant frequencies of the filter sections tunable through voltage-controlled varactors. This allows the duplexer to dynamically adjust its pass band bandwidth to match specific channel requirements, eliminating the need for fixed wide bandwidth designs with many cascaded sections. The tunable resonant frequencies enable the filter to be optimized for narrowband channels while maintaining the ability to cover wide bandwidth when needed.
Solution Approach 2:
The patent changes the physical parameters of the filter sections by using varactors whose capacitance can be adjusted via control voltages. This parameter change allows the resonant frequency of each section to be tuned, thereby adjusting the pass band characteristics. By controlling the capacitance values of the varactors, the system can achieve the required bandwidth with fewer sections compared to fixed nontunable designs.
2Reliability
If fixed nontunable duplexers are designed for wide bandwidth to compensate for variations, then the frequency coverage is sufficient, but the number of components and cost increase
Solution Approach 1:
The tunable design allows the duplexer to adapt its frequency coverage dynamically based on the specific channel being used. Instead of designing for the worst-case wide bandwidth scenario, the system can tune its resonant frequencies to match the actual operating channel, providing sufficient frequency coverage margin only when needed while reducing component count for narrowband operations.
Solution Approach 2:
By using voltage-controlled varactors, the patent enables parameter changes in the resonant frequencies of the filter sections. This allows the system to adjust its frequency coverage characteristics to match actual operating conditions, providing adequate margins for process and temperature variations without requiring excessive bandwidth coverage that would increase component count and cost.
3Adaptability or versatility
If tunable duplexers use variable capacitance elements, then the frequency tuning capability is achieved, but the linearity and signal processing performance may deteriorate
Solution Approach 1:
The patent incorporates feedback mechanisms through calibration circuits that adjust the control voltages applied to the varactors. This feedback ensures that the tunable filter maintains optimal performance characteristics including linearity across different tuning positions. The calibration circuit compensates for non-linearities introduced by the varactors, thereby maintaining signal processing performance while enabling frequency tuning capability.
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 tunable duplexer reduces the number of resonant sections and components, achieving better signal processing performance, lower costs, and improved linearity by positioning stop band zeros effectively, while maintaining acceptable input return loss and pass band performance.
Implementation Method 1
The tunable duplexer reduces the number of resonant sections and components, achieving better signal processing performance, lower costs, and improved linearity by positioning stop band zeros effectively, while maintaining acceptable input return loss and pass band performance
Data Source
AI summary
A tunable duplexer using voltage-controlled varactors is presented. The center frequency, the pass band, and the stop band are each tunable to meet system requirements. A calibration circuit driving digital to analog converters produces the necessary voltages used in the resonant circuits. The tunable duplexer can be fabricated on a single silicon chip. On-chip transformers can be used to reduce the voltage level of signals in the filters to improve the linearity of the duplexer.