Multilayer High-Frequency Filter for Harmonic Stopband Rejection
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Solution Overview
Problem
High frequency filters struggle to suppress unnecessary harmonic components in the frequency band higher than the passing frequency due to distortion characteristics in high frequency circuits.
Innovation Solution
A high frequency filter design incorporating a multilayer substrate with specific electric conduction pads and columnar conductors, where the electrical lengths between these components are 90 degrees or less at the center frequency of the stopband, forming a coaxial line with the columnar conductor as the inner conductor and surrounding conductors as the outer conductor, effectively rejecting signal transmission in the stopband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional high frequency filter with a single perpendicular conductor and electric conduction pads is used, then the filter structure is simple, but unnecessary harmonic components in the high frequency band cannot be suppressed
Solution Approach 1:
The filter structure is segmented into multiple functional layers: first and second electric conduction pads for fundamental frequency filtering, and third electric conduction pads specifically positioned to suppress harmonic components. This segmentation allows each layer to target specific frequency ranges, resolving the contradiction between structural simplicity and harmonic suppression capability.
Solution Approach 2:
The invention extends the conventional two-layer pad structure into a three-layer multilayer configuration. By adding the third electric conduction pads in an intermediate layer with specific positioning and spacing, the filter gains an additional dimensional degree of freedom for controlling electromagnetic field distribution, enabling effective harmonic suppression without excessive structural complexity.
2Object-affected harmful factors
If the electrical length between electric conduction pads is increased to improve filtering, then the stopband frequency is reduced, but the filter size increases
Solution Approach 1:
Different spacing configurations are applied to different functional regions: the first and second electric conduction pads use one spacing arrangement for fundamental frequency filtering, while the third electric conduction pads use a different, optimized spacing specifically tailored for harmonic suppression. This local quality differentiation allows effective filtering without requiring uniform increases in overall filter dimensions.
Solution Approach 2:
The invention optimizes the spacing parameter between the third electric conduction pads and other conductive elements to specific ranges that correspond to electrical lengths suitable for harmonic frequency rejection. By carefully controlling this parameter, the filter achieves effective stopband formation at harmonic frequencies without requiring excessive physical spacing that would increase filter size.
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 filter successfully forms a stopband in the frequency band of unnecessary harmonic components, suppressing transmission of harmonic components up to the fourth harmonic with respect to the pass band, thereby improving signal rejection in high frequency circuits.
Implementation Method 1
a first electric conduction pad including multiple lands formed along a layering direction of the multilayer substrate is provided, the multiple lands forming a capacitance
Implementation Method 2
the first columnar conductor and the second columnar conductors constitute a coaxial line in which the first columnar conductor functions as an inner conductor and the second columnar conductors function as an outer conductor
Implementation Method 3
a portion corresponding to the spacing between the first electric conduction pad and the third electric conduction pad and a portion corresponding to the spacing between the second electric conduction pad and the third electric conduction pad are electrical lengths of 90 degrees or less at the center frequency of a stopband where transmission of a signal is rejected
Data Source
AI summary
A high frequency filter includes: a multilayer substrate including a first substrate for which lands are provided, a second substrate for which lands are provided, and a third substrate for which lands are provided, the third substrate being sandwiched between the first substrate and the second substrate; a columnar conductor electrically connected to the lands in the multilayer substrate; and columnar conductors provided to surround the columnar conductor, electrically connected to a ground plane of the first substrate, and electrically connected to a ground plane of the second substrate. The spacing between the lands of the first substrate and the lands of the third substrate and the spacing between the lands of the second substrate and the lands of the third substrate are electrical lengths of 90 degrees or less at the cutoff frequency.