BAW Filter Loop Circuit Phase Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ladder-type filters using bulk acoustic wave resonators face a trade-off between passband and attenuation characteristics, resulting in insufficient attenuation near the passband, which affects the separation and isolation performance.
Innovation Solution
Incorporating a loop circuit with surface acoustic wave or bulk acoustic wave resonators between distinct points in the ladder-type circuit for phase-cancellation, improving attenuation levels near the passband within the stopband.
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 can be independently optimized for its specific function, allowing the ladder circuit to minimize passband loss while the loop circuit provides enhanced attenuation near the passband without compromising passband performance.
Solution Approach 2:
The loop circuit acts as an intermediary element that selectively interacts with stopband signals. By connecting the loop circuit between distinct points on the signal path, it provides additional attenuation for frequencies near the passband while remaining transparent to passband signals, thus resolving the contradiction between maintaining low passband loss and achieving high attenuation near the passband.
2Reliability
If design parameters are optimized between series-connected FBARs and parallel-connected FBARs in a conventional ladder-type filter, then passing characteristics are improved, but attenuation characteristics within the stopband deteriorate
Solution Approach 1:
The filtering function is segmented into two specialized circuits: the ladder-type circuit handles passband signal transmission with optimized passing characteristics, while the loop circuit handles stopband signal attenuation. This segmentation allows each circuit to be optimized for its specific frequency range without compromising the other function.
Solution Approach 2:
The loop circuit provides excessive attenuation action specifically for stopband frequencies near the passband. By designing the loop circuit with resonators having frequencies slightly offset from the passband center, it creates strong attenuation in the stopband region while having minimal impact on passband transmission characteristics.
3Reliability
If a loop circuit is added for phase cancellation, then attenuation near the passband is improved, but device complexity increases
Solution Approach 1:
The loop circuit is merged with the existing ladder-type filter structure by connecting it between distinct points on the signal path. This integration allows the loop circuit to share the same physical substrate and interconnect structures, reducing the overall complexity increase compared to implementing separate filter circuits.
Solution Approach 2:
The loop circuit components, particularly the resonators and capacitors, serve multiple functions: they provide phase cancellation for attenuation near the passband, contribute to overall stopband rejection, and can be designed to work with standard fabrication processes. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity.
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 within the stopband, allowing for better signal separation and isolation.
Implementation Method 1
Incorporating a loop circuit with surface acoustic wave or bulk acoustic wave resonators between distinct points in the ladder-type circuit for phase-cancellation
Implementation Method 2
Incorporating a loop circuit with surface acoustic wave or bulk acoustic wave resonators between distinct points in the ladder-type circuit for phase-cancellation
Implementation Method 3
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 4
series-connected FBARs 111, 113, 115, 117 are disposed in series along a conductive signal path 131 extending from a first signal contact 141 to a second signal contact 143 on the top surface 151a of a piezoelectric substrate 151
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 formed by a BAW resonator. In one example the filter includes a ladder-type circuit formed by a bulk acoustic wave (BAW) resonator, and 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. The two distinct points may be the input and the output of the ladder-type circuit. The loop circuit may include a SAW resonator or a BAW resonator. The BAW resonator may be a film bulk acoustic resonator (FBAR) or solidly mounted resonator (SMR).