Tunable Band-Pass Filter Using Coplanar Waveguide on SOI
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Solution Overview
Problem
Existing high performance band-pass filters embedded in system-on-a-chip (SOC) using MEMS or PCBs face integration challenges with very-large-scale integration (VLSI) structures, particularly in millimeter-wave and microelectronics devices, due to difficulties in integrating MEMS capacitors and metal-air-metal capacitors.
Innovation Solution
A tunable band-pass filter design is implemented using a silicon-on-insulator substrate with a metal shielding layer and a band-pass filter device featuring a MOS varactor, which includes a first port, a second port, and a coupling metal between them, arranged in a coplanar waveguide configuration to enhance coupling effects and reduce direct coupling with the substrate, allowing for improved RF signal transfer and filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MEMS or PCB structures are used for band-pass filters, then filter performance is improved, but integration difficulty with VLSI increases
Solution Approach 1:
The patent merges the band-pass filter device with the silicon-on-insulator substrate and coplanar waveguide structure to form an integrated filter system. The filter device is positioned above the substrate with coupling metal extending between ports, eliminating the need for separate MEMS or PCB components while maintaining filter performance and enabling VLSI integration.
2Adaptability or versatility
If traditional off-chip capacitors are used, then resonate frequency adjustment is enabled, but physical area increases
Solution Approach 1:
The patent transitions from planar off-chip capacitor layouts to a three-dimensional integrated structure where the band-pass filter device is positioned above the silicon-on-insulator substrate. This vertical stacking enables frequency adjustment functionality while reducing the lateral physical area occupied by the filter components.
3Reliability
If coupling metal is positioned between ports, then coupling effects are enhanced, but direct coupling with substrate increases
Solution Approach 1:
The patent introduces the silicon-on-insulator substrate as an intermediary layer between the coupling metal and the underlying substrate. The substrate acts as a mediator that enables controlled coupling between ports while preventing unwanted direct coupling with the substrate through its insulating properties, thus enhancing desired coupling effects while blocking harmful direct coupling.
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 design enhances coupling effects, reduces physical area, and provides a higher tuning range and accuracy for resonate frequency, facilitating integration with VLSI structures and reducing the size of high performance tunable band-pass filters.
Implementation Method 1
a band-pass filter device featuring a MOS varactor, which includes a first port, a second port, and a coupling metal between them, arranged in a coplanar waveguide configuration to enhance coupling effects and reduce direct coupling with the substrate
Implementation Method 2
A representative filter comprises a silicon-on-insulator substrate having a top surface, a metal shielding positioned above the top surface of the silicon-on-insulator substrate
Implementation Method 3
at least one layer of metal shielding is positioned above the top surface of the silicon-on-insulator substrate. The metal shielding layer can prevent AC signal of the coplanar waveguide structure from passing below the coplanar waveguide structure
Data Source
AI summary
A representative filter comprises a silicon-on-insulator substrate having a top surface, a metal shielding positioned above the top surface of the silicon-on-insulator substrate, and a band-pass filter device positioned above the metal shielding. The band-pass filter device includes a first port, a second port, and a coupling metal positioned between the first and second ports.