Active Multiband Filter Circuitry With Switchable Impedance Matching
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Solution Overview
Problem
Designing filter and amplifier circuitry for wireless communications in electronic devices is challenging due to the high cost of passive bandpass filters and the complexity of integrating them with low noise amplifiers.
Innovation Solution
Implementing a circuitry with switchable matching circuits and lowpass-to-bandpass conversion filters, along with a signal combiner and frequency shifting circuit, to combine radio-frequency signals from multiple bands into a single receive path, reducing the need for multiple amplifiers and filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive bandpass filters are used for filtering radio-frequency signals, then filtering performance is improved, but cost increases
Solution Approach 1:
The patent transforms passive bandpass filters into active filters by changing the filtering mechanism from passive LC circuits to active switched-capacitor circuits. The active filters use switches controlled by clock signals to simulate inductor behavior, enabling filtering functionality without expensive passive components while maintaining acceptable filtering performance across multiple frequency bands
Solution Approach 2:
The patent replaces mechanical/passive filtering components (inductors, capacitors, resistors) with electronic switching and capacitive networks. The active filter circuitry uses transistor switches and capacitors to create frequency-selective filtering, substituting the traditional passive mechanical filtering approach with an electronically controlled system that reduces component cost and complexity
2Reliability
If separate filter and amplifier circuitry is designed for each frequency band, then frequency selectivity is improved, but device complexity increases
Solution Approach 1:
The patent creates a universal active filter circuit that can operate across multiple frequency bands by changing switch control signals. The same physical filter circuit provides frequency selectivity for different bands (e.g., LTE, Wi-Fi, Bluetooth) by reconfiguring which switches are active, eliminating the need for separate filter circuits for each frequency band and reducing overall device complexity
Solution Approach 2:
The patent implements dynamic reconfiguration of the filter circuitry using controlled switches that can be activated or deactivated based on the desired frequency band. This dynamic switching allows a single static circuit topology to provide multiple frequency-selective filtering functions, adapting the circuit's behavior to match different operational requirements without physical reconfiguration
3Power
If multiple amplifiers are used for different frequency bands, then signal amplification is improved, but device complexity increases
Solution Approach 1:
The patent employs a universal low-noise amplifier that can amplify signals across multiple frequency bands without requiring separate amplifier circuits for each band. The amplifier is designed with broad bandwidth characteristics and works in conjunction with the reconfigurable active filters to provide the necessary signal amplification for LTE, Wi-Fi, and Bluetooth frequencies, thereby reducing the total number of amplifiers needed in the device
Data Source
AI summary
Wireless circuitry can include a first filter circuit configured to output signals in a first frequency range, a second filter circuit configured to output signals in a second frequency range different than the first frequency range, and a signal combiner having a first input coupled to the first filter circuit and having a second input coupled to the second filter circuit. The wireless circuitry can further include a first switchable impedance matching circuit coupled between an antenna and the first filter circuit and a second switchable impedance matching circuit coupled between the antenna and the second filter circuit. The first and second filter circuits can be active filters such as lowpass-to-bandpass conversion filters operable in different frequency bands.