Mixer-Filter Circuitry Using Active Inductor Complex Poles
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Solution Overview
Problem
Current filter circuitries in wireless communication systems face challenges in generating complex poles without significant current consumption, especially with increasing signal bandwidths, as they require high Unity Gain Bandwidth from op-amps or large silicon area for passive inductors, leading to inefficiencies and stability issues.
Innovation Solution
A combined mixer and filter circuitry using Hara's active inductor with a capacitor, which generates complex poles with moderate quality factor, reusing direct currents and requiring minimal extra current consumption, eliminating feedback loops and stability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If op-amps are used to generate complex poles in filter circuitry, then the required attenuation at stop band is achieved, but current consumption increases significantly due to high Unity Gain Bandwidth requirements
Solution Approach 1:
The patent combines the mixer and filter circuitry into a single integrated structure where the filter shares the same current source and active inductor with the mixer. This merging eliminates the need for separate high-bandwidth op-amps, reducing current consumption while maintaining stop band attenuation through the shared filter poles.
Solution Approach 2:
The filter circuitry uses the existing current source and active inductor from the mixer to generate complex poles, rather than requiring additional dedicated components. The mixer's own current consumption serves dual purposes: driving the mixer function and providing the necessary current for filter operation, thereby eliminating extra current consumption.
2Reliability
If passive inductors are used to generate complex poles, then filter functionality is achieved, but silicon area increases significantly
Solution Approach 1:
The patent replaces physical passive inductors with an active inductor implementation using a transistor and resistor. This substitution eliminates the need for large silicon area passive inductors while maintaining the filtering function through the active generation of complex poles by the transistor-based active inductor.
3Reliability
If high order filters are implemented with multiple op-amps, then required stop band attenuation is achieved, but device complexity and current consumption increase
Solution Approach 1:
The patent merges the mixer and filter into a single circuit block, allowing high-order filtering to be achieved by multiplying the order of a single integrated circuit rather than cascading multiple separate op-amp filters. This reduces device complexity by eliminating the need for multiple discrete op-amps while maintaining the required stop band attenuation.
Data Source
AI summary
A combined mixer and filter circuitry is disclosed. The combined mixer and filter circuitry comprises a mixer comprising a first input, a second input and an output. The combined mixer and filter circuitry further comprises a filter comprising an active inductor and a first capacitor. The active inductor comprises a transistor having a first terminal, a second terminal and a third terminal and a resistor connected between the first terminal of the transistor and a voltage potential. The first capacitor is connected between the third terminal and a signal ground and the second terminal of the transistor is connected to the second input of the mixer.