High-Pass Filter Topology for Steep Roll-Off and Spurious Suppression
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Solution Overview
Problem
Existing high-pass filters have an insufficient steepness of attenuation in the transition region between the passband and stopband, and they often form spurious signals within the passband, particularly in frequency bands above 3 GHz such as Band46, E-UTRA, and 5G new radio frequencies.
Innovation Solution
The design incorporates at least one capacitor in a first pathway between input and output terminals, an inductor connected to the pathway, and acoustic wave resonators in parallel and series configurations to narrow the transition width and prevent spurious formation within the passband, by carefully aligning resonant and antiresonant frequencies of the acoustic wave resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LC circuits with acoustic wave resonators are used, then the filter can operate in high-frequency bands, but the attenuation steepness in the transition region is insufficient
Solution Approach 1:
The filter is divided into multiple pathways (first pathway with capacitors and inductors, second pathway with acoustic wave resonators) that work together to achieve steep attenuation. Each pathway handles specific frequency ranges, with the acoustic wave resonators providing sharp roll-off characteristics in the transition region.
Solution Approach 2:
The patent combines conventional LC circuit elements (capacitors C1-C3, inductor L1) with acoustic wave resonators (R1, R2) in a unified filter structure. This merging allows the filter to achieve both the broadband characteristics of LC circuits and the sharp attenuation of acoustic wave resonators.
2Reliability
If conventional high-pass filters are used, then the circuit is simple, but spurious signals are formed within the passband
Solution Approach 1:
Acoustic wave resonators R1 and R2 act as intermediary elements that selectively suppress spurious signals within the passband. These resonators are configured with specific resonant frequencies that target and attenuate unwanted spurious components while maintaining the desired passband characteristics.
Solution Approach 2:
The patent carefully selects and adjusts the resonant frequencies of acoustic wave resonators R1 and R2 to specifically target spurious signal frequencies. By changing the resonant frequency parameters of these resonators, spurious signals at specific frequencies are suppressed without affecting the main passband.
3Reliability
If the transition width is narrowed using acoustic wave resonators, then attenuation steepness improves, but the risk of spurious formation increases
Solution Approach 1:
The filter is segmented into multiple functional pathways: the first pathway (capacitors C1-C3 and inductor L1) provides the basic high-pass filtering and determines the general transition width, while the second pathway (acoustic wave resonators R1 and R2) provides additional attenuation and suppresses spurious signals. This segmentation allows independent optimization of each pathway to achieve both narrow transition width and spurious suppression.
Solution Approach 2:
The acoustic wave resonators serve as intermediary elements that narrow the transition width while simultaneously suppressing spurious signals. By positioning these resonators with their resonant frequencies aligned with the transition region, they provide the necessary attenuation steepness without creating harmful spurious effects.
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
This configuration significantly narrows the transition width and inhibits spurious signals within the passband, improving the steepness of attenuation in the transition region, particularly in high-frequency bands like Band46 and 5G new radio frequencies.
Implementation Method 1
at least one first acoustic wave resonator located in a second pathway connected in parallel to the first pathway between the input terminal and the output terminal, the at least one first acoustic wave resonator being connected in parallel to the at least one capacitor; and at least one second acoustic wave resonator, a first end of the at least one second acoustic wave resonator being coupled to the second pathway, a second end of the at least one second acoustic wave resonator being coupled to a ground
Implementation Method 2
a piezoelectric substrate, and a plurality of electrode fingers arranged in a comb shape on the upper surface of the piezoelectric substrate
Data Source
AI summary
A high-pass filter includes: at least one capacitor located in a first pathway between input and output terminals and connected between the input and output terminals; at least one inductor, a first end of the at least one inductor being coupled to the first pathway, a second end of the at least one inductor being coupled to a ground; at least one first acoustic wave resonator located in a second pathway connected in parallel to the first pathway between the input and output terminals, the at least one first acoustic wave resonator being connected in parallel to the at least one capacitor; and at least one second acoustic wave resonator, a first end of the at least one second acoustic wave resonator being coupled to the second pathway, a second end of the at least one second acoustic wave resonator being coupled to a ground.