BAW Ladder Filter Loop Circuit for Near-Passband Attenuation
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Solution Overview
Problem
Conventional ladder-type filters using bulk acoustic wave resonators face a trade-off between passband characteristics and attenuation characteristics, with insufficient attenuation near the passband, affecting performance.
Innovation Solution
Incorporating a loop circuit with a coupled bulk acoustic wave resonator between the input and output of a ladder-type circuit, optimized for phase-cancellation, to improve attenuation levels near the passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If design parameters are optimized between series-connected FBARs and parallel-connected FBARs in a conventional ladder-type filter, then loss in the passband is reduced, but attenuation characteristics near the passband remain insufficient
Solution Approach 1:
The filter is divided into two independent circuits: a ladder-type circuit for passband signal transmission and a loop circuit for stopband signal attenuation. Each circuit is optimized for its specific function, with the ladder-type circuit minimizing passband loss and the loop circuit maximizing stopband attenuation near the passband.
Solution Approach 2:
The loop circuit acts as an intermediary element that specifically targets and attenuates signals in the stopband near the passband frequency, which the conventional ladder-type circuit cannot effectively handle. This intermediary circuit bridges the performance gap without affecting passband characteristics.
2Reliability
If a loop circuit with coupled BAW resonator is added for phase cancellation, then attenuation in stopband near passband is improved, but device complexity increases
Solution Approach 1:
The loop circuit is merged with the existing ladder-type filter circuit, sharing common input and output nodes. This combination allows the filter to achieve enhanced stopband attenuation near the passband while maintaining a compact and integrated structure, rather than adding a completely separate system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the separation and isolation characteristics of the filter by minimizing loss in the passband and improving attenuation in the stopband.
Implementation Method 1
a loop circuit connected between two distinct points on a signal path extending from an input to an output of the ladder-type circuit for phase-cancellation of signals at the two distinct points
Implementation Method 2
Bulk acoustic wave (BAW) resonators have been used for such filtering devices. The BAW resonators may include film bulk acoustic resonators (FBARs)
Data Source
AI summary
Aspects and examples provide improvement in the attenuation level near the passband within the stopband of the bandpass-type filter using a ladder-type circuit. In one example the ladder-type circuit is formed from bulk acoustic wave resonators. A loop circuit is connected between two distinct points on a signal path extending from an input to an output of the ladder-type circuit for phase-cancellation of signals at the two distinct points. The two distinct points may be the input and the output of the ladder-type circuit. The loop circuit may include a coupled bulk acoustic wave resonator.