Gm-C Filter Calibration Using Cell Re-Use for Stable Bandwidth
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Solution Overview
Problem
Gm-C filters exhibit poorly controlled passband frequency response due to variations in semiconductor process, supply voltage, and temperature, leading to unstable corner frequency and bandwidth.
Innovation Solution
A transconductor-capacitor (Gm-C) circuit operates in a calibration mode as a capacitor-controlled oscillator to adjust transconductor or capacitor values based on output and reference frequency signals, ensuring accurate calibration and stable operation as a filter by configuring between oscillator and filter modes using variable resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Gm-C filter is used to provide lower noise and lower-power operation, then noise and power consumption are reduced, but passband frequency response control deteriorates due to variation of Gm and C values with process, voltage and temperature
Solution Approach 1:
The patent applies preliminary action by performing calibration of the Gm-C filter before normal operation. A calibration mode is implemented where the filter parameters are adjusted in advance to compensate for expected variations in process, voltage, and temperature. This preliminary calibration ensures that the filter maintains stable passband frequency response during actual operation while retaining the low power consumption benefits of the Gm-C architecture.
2Stability of the object's composition
If calibration is performed to adjust circuits to changing conditions, then passband frequency response stability is improved, but device complexity increases due to additional calibration circuitry and control mechanisms
Solution Approach 1:
The patent implements universality by designing the calibration circuitry to serve multiple functions. The same circuit elements and control mechanisms are used both for calibration adjustments and for normal filter operation. This multi-functional approach allows the system to achieve stable passband frequency response through calibration while minimizing additional device complexity, as the calibration infrastructure is integrated with the operational filter structure rather than being completely separate.
Data Source
AI summary
Various embodiments are disclosed relating filter calibration with cell re-use. According to an example embodiment, an apparatus includes a first circuit, including a variable circuit element. The first circuit is adapted to output an output frequency signal during a calibration mode and to operate as a filter during a filter mode. A control circuit is coupled to the first circuit and is adapted to receive a reference frequency signal and to calibrate the first circuit by adjusting the variable circuit element based on the reference frequency signal and the output frequency signal during the calibration mode. The calibrated first circuit is configured to then operate as a filter during the filter mode.