Bridge-Capacitor Band-Pass Filter for Low Loss and Rejection
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Solution Overview
Problem
Current band pass filters for radio frequency electronic systems face challenges in achieving low loss, good out-of-band rejection, and compact size while meeting performance specifications, particularly for Ultra High Band frequencies.
Innovation Solution
The design incorporates a band pass filter with a first and second LC resonant circuit, capacitors in series, and a bridge capacitor to create transmission zeros, implemented on an integrated passive device die, using high-quality surface mount capacitors and small shunt inductors to achieve low loss and compact size, with the capacitors and inductors distributed across a laminate and IPD die for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional band pass filter designs are used, then out-of-band rejection can be achieved, but in-band insertion loss increases and device size becomes larger
Solution Approach 1:
The filter is divided into multiple resonant circuits (first and second LC resonant circuits) with distinct functions. The first resonant circuit handles passband signals with low loss, while the second resonant circuit creates transmission zeros for out-of-band rejection. This segmentation allows each circuit to be optimized for its specific function, achieving both low insertion loss and good rejection simultaneously.
Solution Approach 2:
A bridge capacitor is introduced as an intermediary element connecting the two resonant circuits. This bridge capacitor creates transmission zeros at specific frequencies below the passband, providing the necessary out-of-band rejection without significantly impacting the in-band insertion loss. The intermediary element mediates between the conflicting requirements of low loss and high rejection.
2Volume of moving object
If acoustic wave filters are used, then compact size is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent merges multiple filter functions into a single integrated passive device (IPD) die. Both the first and second LC resonant circuits, along with coupling capacitors and the bridge capacitor, are integrated on one die using standard semiconductor fabrication processes. This merging achieves compact size comparable to acoustic wave filters while maintaining ease of manufacture through established IPD technology.
Solution Approach 2:
The design uses planar printed circuit board (PCB) layouts that replicate the functionality of three-dimensional acoustic wave structures. By copying the filter topology into a two-dimensional IPD implementation, the patent achieves similar compactness without the complex manufacturing processes required for acoustic wave filters, thereby reducing cost and improving manufacturability.
3Device complexity
If LTCC filters are used, then integration is achieved, but insertion loss increases
Solution Approach 1:
The patent changes the material parameters and construction approach by using high-quality capacitors and optimized conductor traces on the IPD die. By carefully selecting capacitor quality factors and minimizing trace inductance, the design achieves lower insertion loss than LTCC filters while maintaining high integration. The parameter optimization of individual components compensates for the inherent losses in integrated structures.
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
The solution provides band pass filters with low in-band insertion loss, good out-of-band rejection, and a compact size, making them more cost-effective and comparable in size to acoustic wave filters while offering lower loss than LTCC filters, suitable for frequencies above 3 GHz.
Implementation Method 1
A first LC resonant circuit, a second LC resonant circuit
Implementation Method 2
The bridge capacitor is arranged to create a transmission zero at a frequency below the passband of the band pass filter
Data Source
AI summary
Aspects of this disclosure relate to a band pass filter that includes LC resonant circuits coupled to each other by a capacitor. A bridge capacitor can be in parallel with series capacitors, in which the series capacitors include the capacitor coupled between the LC resonant circuits. The bridge capacitor can create a transmission zero at a frequency below the passband of the band pass filter. The LC resonant circuits can each include a surface mount capacitor and a conductive trace of the substrate, and an integrated passive device die can include the capacitor. Band pass filters disclosed herein can be relatively compact, provide relatively good out-of-band rejection, and relatively low loss.