Active-Inductor BAW Oscillator for Low-Noise GHz Biasing
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Solution Overview
Problem
Bulk acoustic wave (BAW) MEMS resonators are sensitive to capacitive loading, which degrades their quality factor and impedance, leading to high gain and spurious oscillations at low frequencies, making it challenging to implement low-power oscillators effectively.
Innovation Solution
The use of active inductor circuits, which are smaller than transformers or inductors, provides biasing, reduces capacitive loading, and minimizes spurious oscillations by coupling with a differential active inductor circuit and a gain circuit, thereby reducing circuit size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional transformers or inductors are used for biasing, then reliable biasing is achieved, but circuit size increases
Solution Approach 1:
The patent replaces traditional passive inductors or transformers with an active inductor circuit implemented using transistors (such as common-source or common-gate transistor configurations). This substitution of passive electromagnetic components with active semiconductor circuits achieves the same biasing function while significantly reducing the circuit area occupied by inductors or transformers.
2Ease of manufacture
If capacitive loading is increased, then circuit design becomes easier, but quality factor and impedance degrade
Solution Approach 1:
The active inductor circuit serves as an intermediary component between the BAW resonator and the rest of the oscillator circuit. It provides impedance transformation and buffering that isolates the resonator from excessive capacitive loading effects, thereby maintaining the quality factor and impedance characteristics while still allowing for practical circuit design.
3Use of energy by moving object
If low-power operation is implemented, then energy consumption is reduced, but spurious oscillations increase
Solution Approach 1:
The active inductor circuit enables dynamic control of operating parameters such as bias current and transconductance. By optimizing these parameters, the circuit achieves low power consumption while maintaining sufficient gain to suppress spurious oscillations. The transistor-based active inductor allows for parameter tuning that balances power efficiency with oscillation suppression.
Data Source
AI summary
An apparatus comprises a piezoelectric resonator, a first active inductor circuit, and a second active inductor circuit. The piezoelectric resonator includes a first resonator terminal and a second resonator terminal. The first active inductor circuit is coupled between the first resonator terminal and a power supply terminal, the first active inductor circuit having a first impedance that reduces with a first frequency where the first frequency is at or above 1 GHz. The second active inductor circuit is coupled between the second resonator terminal and the power supply terminal, the second active inductor circuit having a second impedance that reduces with a second frequency where the second frequency is at or above 1 GHz.