Surface-Mount Microstrip Bandpass Filter With Low Loss Above 15 GHz
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Solution Overview
Problem
The challenge lies in developing compact, high-frequency stripline filters that can effectively operate at frequencies above 15 GHz with minimal insertion loss and maintain excellent performance characteristics, particularly for 5G frequency spectrum applications, where existing miniaturization efforts face difficulties in surface mounting and maintaining low insertion loss.
Innovation Solution
A high-frequency stripline filter design featuring a monolithic base substrate with thin-film microstrips and strategically placed vias, where the conductive path length is optimized to approximately 95-105% of a quarter wavelength, ensuring low insertion loss and return loss across a wide frequency range, and the filter is configured for compact surface mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturization is pursued to reduce component size for high frequency operation, then the filter becomes more compact and suitable for surface mounting, but the insertion loss increases and performance deteriorates
Solution Approach 1:
The patent transitions from traditional planar microstrip filters to a three-dimensional stripline configuration embedded within a monolithic substrate. By utilizing the Z-dimension (vertical embedding) in addition to the X-Y plane, the filter achieves compact footprint while maintaining adequate electrical path lengths for low insertion loss at high frequencies
Solution Approach 2:
The patent optimizes the conductive path length to be approximately 95-105% of a quarter wavelength at the operating frequency. This precise parameter control ensures resonant operation with minimal insertion loss while keeping the physical dimensions compact for surface mounting applications
2Loss of energy
If the conductive path length is increased to reduce insertion loss, then signal transmission improves, but the filter occupies more space and becomes less suitable for compact mounting
Solution Approach 1:
The stripline configuration embeds conductive paths within the substrate thickness, utilizing the vertical dimension to achieve longer electrical path lengths without increasing the horizontal footprint. This allows the filter to maintain compact surface mounting dimensions while achieving the quarter-wavelength path length needed for low insertion loss
Solution Approach 2:
The patent employs a monolithic base substrate that integrates multiple functional layers (conductive layers, dielectric layers, ground planes) into a single composite structure. This composite approach enables compact integration of the quarter-wavelength resonant path while maintaining the electrical performance needed for low insertion loss
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 achieves an insertion loss greater than -3.5 dB at frequencies above 15 GHz, with excellent return loss characteristics and a compact form factor, suitable for 5G applications, enabling efficient signal processing and transmission.
Implementation Method 1
A conductive path may include a via formed in the monolithic base substrate. The conductive path may electrically connect the first thin-film microstrip with the port on the bottom surface of the filter.
Implementation Method 2
The conductive path may have an effective length between the first arm of the thin-film microstrip and the port that ranges from about 95% to about 105% of λ/4, where λ is a wavelength that corresponds with a passband frequency propagating through the monolithic base substrate.
Data Source
AI summary
A high frequency, stripline filter may have a bottom surface for mounting to a mounting surface. The filter may include a monolithic base substrate having a top surface and a plurality of thin-film microstrips, including a first thin-film microstrip and a second thin-film microstrip, formed over the top surface of the substrate. Each of the plurality of thin-film microstrips may have a first arm, a second arm parallel to the first arm, and a base portion connected with the first and second arms. A port may be exposed along the bottom surface of the filter. A conductive path may include a via formed in the substrate. The conductive path may electrically connect the first thin-film microstrip with the port on the bottom surface of the filter. The filter may exhibit an insertion loss that is greater than −3.5 dB at a frequency that is greater than about 15 GHz.