Distributed Amplifier RF Filter with Tunable Cutoff Bands
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Solution Overview
Problem
Conventional RF communication devices require multiple fixed-frequency bandpass filters, which are costly, not optimized for miniaturization, and lossy, making them inefficient for multi-frequency band operations.
Innovation Solution
A tunable filter device using a distributed wide-band amplifier with adjustable cut-off frequencies, implemented with a LCR network and switchable capacitors, allowing for programmable frequency band response without altering gain, linearity, or noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple fixed-frequency bandpass filters are used for multi-frequency band operations, then frequency selectivity is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a single distributed amplifier that can function as multiple bandpass filters by reconfiguring its gain elements. The amplifier is designed to support multiple frequency bands (e.g., GSM 900, GSM 1800, UMTS 2100) through dynamic control of transconductance values, eliminating the need for separate fixed-frequency filters for each band. This multi-functional approach directly resolves the contradiction by providing broad frequency band coverage while maintaining low device complexity.
Solution Approach 2:
The patent employs dynamic reconfiguration of the distributed amplifier's transconductance values to adapt the filter characteristics to different frequency bands. By controlling the gain elements (transistors) with variable transconductance, the system can dynamically switch between different frequency responses without physical reconfiguration. This dynamic adaptability allows a single device to replace multiple fixed filters, resolving the contradiction between versatility and complexity.
2Adaptability or versatility
If multiple stand-alone RF bandpass filters are employed, then frequency selectivity is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the functionality of multiple stand-alone RF bandpass filters into a single distributed amplifier circuit. By combining the filtering functions for multiple frequency bands (GSM 900, GSM 1800, UMTS 2100, etc.) into one integrated device with reconfigurable gain elements, the manufacturing cost is significantly reduced compared to producing and assembling multiple separate filter components. This merging approach directly addresses the cost issue while maintaining comprehensive frequency band filtering capability.
3Adaptability or versatility
If conventional fixed filters are used, then frequency selectivity is improved, but miniaturization is hindered
Solution Approach 1:
The distributed amplifier is designed as a universal filtering device that can operate across multiple frequency bands through electronic reconfiguration of its gain elements. This eliminates the need for multiple separate filter devices, each optimized for a specific frequency band. By consolidating multi-frequency band support into a single reconfigurable device, the overall volume is dramatically reduced, directly resolving the contradiction between adaptability and miniaturization.
4Adaptability or versatility
If multiple RF bandpass filters are implemented, then frequency selectivity is improved, but signal loss increases
Solution Approach 1:
The patent merges multiple filtering functions into a single distributed amplifier, eliminating the cumulative signal loss that occurs when signals pass through multiple separate filters. The distributed amplifier architecture provides gain rather than just filtering, which compensates for losses and improves overall signal quality. This merging approach directly addresses the signal loss issue by replacing multiple lossy filters with a single active device that can provide both filtering and amplification across multiple frequency bands.
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 filter device replaces multiple fixed filters with a single integrated circuit, reducing cost and size while maintaining performance across various frequency bands, ensuring efficient and linear signal processing without re-tuning matching elements.
Implementation Method 1
A tunable filter device using a distributed wide-band amplifier with adjustable cut-off frequencies, implemented with a LCR network and switchable capacitors
Implementation Method 2
switchable capacitors, allowing for programmable frequency band response
Implementation Method 3
distributed wide-band amplifier having at least two amplifying elements, an input transmission line connected to the input of the filter device and connecting inputs of the at least two amplifying elements, an output transmission line connected to the output of the filter device and connecting outputs of the at least two amplifying elements
Data Source
AI summary
The present invention relates to a tunable filter device for providing a tunable band pass characteristics for the receive path of a multi-band front-end module. According to the invention is proposed, a distributed, wide-band amplifier with a low-frequency cut-off and a high-frequency cut-off in combination with a LCR network, of which wide-band amplifier the DC blocking capacitors define the low-frequency cut-off of the filter device, whilst the high-frequency cut-off is determined by the cut-off frequency of the artificial input and output transmission lines of the LCR network. In one embodiment, additional capacitors are coupled in parallel to the DC blocking capacitors of the LCR network, switchable by MOS transistors as switching elements. Accordingly, in a certain embodiment it is proposed to allow tuning of the low- and the high-frequency cut-off by programming with a digital control command.