Mixer-Filter Circuitry Using Active Inductors for Low-Power 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 at high signal bandwidths, and existing solutions like op-amps and passive inductors have limitations such as high power consumption and large silicon area requirements.
Innovation Solution
A combined mixer and filter circuitry using an active inductor and a capacitor, which generates complex poles with moderate quality factor, reusing direct currents from existing blocks and requiring minimal additional current consumption, and can be scaled for different bandwidths by adjusting capacitors and resistors.
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 bandwidth requirements
Solution Approach 1:
The patent combines the mixer and filter functions into a single integrated circuit block, where the filter shares the same current sources and active inductors as the mixer. This merging eliminates the need for separate op-amps dedicated to filter operation, thereby achieving stop band attenuation without the proportional increase in current consumption that would result from adding independent high-bandwidth op-amps.
Solution Approach 2:
The active inductors and current sources in the filter circuitry serve dual purposes: they function as part of the mixer operation and simultaneously provide the necessary filtering capability. This multi-functionality allows the filter to achieve complex pole generation and stop band attenuation while reusing existing current paths, avoiding additional 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 inductor components with electronically synthesized active inductors implemented using transistors and resistors. This substitution eliminates the need for large-area passive inductors while maintaining the filter's complex pole generation capability, thereby achieving the same filtering functionality with significantly reduced silicon footprint suitable for integrated circuits.
3Reliability
If higher order filters are used to achieve required stop band attenuation, then attenuation performance improves, but current consumption increases due to additional op-amps
Solution Approach 1:
The patent integrates multiple filtering functions into a unified circuit structure where a single set of active inductors and capacitors works together to provide the necessary filter order and attenuation. By combining what would traditionally require multiple separate op-amp stages into one integrated filter-mixer block, the design achieves high-order filtering performance without proportionally increasing current consumption.
Data Source
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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.