Combined Mixer-Filter Circuit Using an Active Inductor for High Bandwidth
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Solution Overview
Problem
Current filter circuitry in wireless communication systems faces challenges in generating complex poles without significant current consumption, especially at high signal bandwidths, due to the need for multiple op-amps or large silicon area for passive inductors, leading to high power consumption and stability issues.
Innovation Solution
A combined mixer and filter circuitry using an active inductor with a transistor and resistor, along with a capacitor, which generates complex poles with moderate quality factor, reusing direct currents and requiring minimal extra current consumption, and is scalable by adjusting capacitors and resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If op-amps are used to generate complex poles for filtering, then filtering performance is improved, but current consumption increases significantly
Solution Approach 1:
The patent combines the mixer and filter functions into a single integrated circuit block, where the filter shares the same current source and active inductor with the mixer. This merging eliminates the need for separate op-amps, thereby maintaining filtering performance while significantly reducing current consumption.
Solution Approach 2:
The active inductor and current source are designed to serve dual purposes: they function as the core amplifying elements for the mixer while simultaneously providing the necessary poles for filtering. This multi-functionality allows the circuit to achieve both mixing and filtering without requiring additional dedicated components, thus reducing overall current consumption.
2Reliability
If passive inductors are used to generate complex poles, then filtering performance is improved, but silicon area increases
Solution Approach 1:
The patent replaces physical passive inductors with an active inductor implemented using a transistor and resistor. This substitution eliminates the need for large-area spiral inductors while maintaining the necessary inductive reactance for generating complex poles, thereby achieving filtering performance with minimal silicon area.
Solution Approach 2:
The active inductor allows dynamic control of the inductance value through biasing conditions, enabling the same circuit element to provide different inductance values as needed for filtering and mixing operations. This parameter variability achieves the required filtering performance without requiring large fixed inductors.
3Speed
If higher bandwidth is required for the filter, then signal processing capability is improved, but current consumption increases
Solution Approach 1:
The mixer and filter share the same current source and active inductor, creating a unified signal path that processes signals across the entire bandwidth simultaneously. This combined architecture achieves high bandwidth signal processing without requiring separate high-bandwidth amplifiers, thereby avoiding the current consumption penalty of traditional approaches.
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.