Reconfigurable Analog Filter With Variable Load Passband Control
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Solution Overview
Problem
Analog filters require a wide adjustable range of passbands to support different radio access technology systems, necessitating a reconfigurable filter with adjustable passband/cutoff frequency to effectively remove unwanted signals and minimize noise from adjacent channels.
Innovation Solution
A reconfigurable analog filter is designed with a transimpedance amplifier, input capacitor, variable load circuit, and low pass filter, where the variable load circuit adjusts impedance based on a control signal to provide high impedance in wideband mode and low impedance in narrowband mode, ensuring optimal filtering characteristics across varying bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the passband is made narrow to improve filtering characteristics, then the roll-off characteristic becomes sharper and noise from adjacent channels is minimized, but the adjustable range of the passband is reduced
Solution Approach 1:
The patent implements a variable load circuit that dynamically adjusts the load impedance of the transimpedance amplifier based on control signals. This allows the filter to switch between wideband mode (high impedance) and narrowband mode (low impedance), enabling the passband to be reconfigured according to different radio access technology requirements while maintaining optimal filtering characteristics in each mode
Solution Approach 2:
The patent changes the load impedance parameter of the transimpedance amplifier to achieve different filtering characteristics. By adjusting the load impedance between high and low values, the system can adapt the passband width and roll-off characteristics to match different channel bandwidth requirements, resolving the contradiction between sharp filtering and wide adjustability
2Adaptability or versatility
If the passband is made wide to support different radio access technology systems, then the adjustable range is increased, but the filtering characteristics deteriorate and noise from adjacent channels increases
Solution Approach 1:
The variable load circuit enables dynamic adaptation of the filter characteristics. When wideband operation is required for supporting different RAT systems, the load impedance is increased to maintain a wide passband. When narrowband operation is needed for sharp filtering, the load impedance is decreased to improve roll-off characteristics, thus resolving the contradiction between wide adaptability and filtering precision
3Device complexity
If a fixed impedance load is used in the transimpedance amplifier, then the circuit is simpler, but the passband cannot be adjusted to different bandwidths
Solution Approach 1:
The variable load circuit is designed to provide multiple impedance values (high and low) to the transimpedance amplifier, enabling the same circuit to support both wideband and narrowband operating modes. This multi-functional approach allows a single filter circuit to adapt to different channel bandwidths and radio access technology requirements without requiring multiple separate filter circuits
Solution Approach 2:
The load impedance is made variable through the use of switches that can selectively connect different impedance elements. This dynamic configuration allows the circuit to transition between different operating states, enabling passband adjustment from wide to narrow while maintaining a relatively simple overall circuit structure
Data Source
AI summary
A reconfigurable analog filter includes a transimpedance amplifier configured to convert a current signal into a voltage signal, an input capacitor configured to form a current-mode low pass filter together with an input impedance of the transimpedance amplifier, a variable load circuit including at least one switch configured to selectively close a circuit path to provide a resistor and/or a capacitor as a load of the transimpedance amplifier according to a control signal, and a low pass filter configured to filter the voltage signal.