Dielectric Waveguide Filter with Serpentine Air Channel
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Solution Overview
Problem
Current RF dielectric waveguide filters face challenges with high spurious and harmonic resonance modes close to the passband, leading to high insertion loss and limited power handling, while also being large and expensive.
Innovation Solution
A dielectric waveguide filter design featuring a block of dielectric material with exterior conductive surfaces, resonators formed on the surfaces, and internal serpentine RF signal channels that push spurious and harmonic resonance modes to higher frequencies without degrading the quality factor Q, achieved through the use of open air channels and varying channel widths for optimal coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional dielectric waveguide filter is used, then the filter achieves good insertion loss and fast roll-off, but the spurious and harmonic resonance modes are high and very close to the passband
Solution Approach 1:
The patent introduces an interior RF signal channel dimension within the dielectric block, creating a three-dimensional serpentine path that physically separates the RF signal from spurious resonance modes. This dimensional approach allows the signal to traverse through the filter while spurious modes are pushed to higher frequencies, effectively resolving the contradiction between low insertion loss and suppression of harmful resonance modes.
Solution Approach 2:
The filter is segmented into multiple resonators (first, second, third resonators) arranged in a specific spatial configuration within the dielectric block. The interior channel is segmented into multiple sections that couple these resonators, allowing independent control of signal paths and resonance modes. This segmentation enables the push-spurious function while maintaining low insertion loss through optimized coupling between segments.
2Loss of energy
If air cavity filters are used to achieve low loss and high rejection, then the filter performance improves, but the size and weight increase significantly
Solution Approach 1:
The patent embeds the RF signal channel and resonators within the dielectric block structure, creating a nested configuration where the functional elements are contained within the dielectric material. This nesting allows the filter to achieve air-cavity-like performance with low loss while maintaining a compact form factor and reduced weight compared to traditional air cavity filters.
Solution Approach 2:
The filter utilizes a composite structure combining dielectric material with air-filled interior channels. This composite approach leverages the low loss characteristics of air cavities while using the dielectric block to provide structural support and define the resonator geometries, achieving a balance between performance and weight.
3Object-generated harmful factors
If dielectric loading is added to push spurious further away, then the spurious frequency increases, but the insertion loss degrades
Solution Approach 1:
The patent applies different dielectric characteristics to different regions: the exterior surfaces and resonator structures use dielectric material for defining geometry and controlling resonance, while the interior RF signal channel is kept air-filled or minimally loaded. This local differentiation allows spurious modes to be pushed to higher frequencies through the dielectric resonator structures without degrading insertion loss in the signal path.
Solution Approach 2:
The interior RF signal channel acts as an intermediary structure that mediates between the dielectric resonators. It provides a low-loss transmission path through the dielectric block while the resonators, positioned around the channel, control the spurious modes. This intermediary approach allows the system to achieve both low insertion loss and high spurious rejection.
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 results in a lower-weight, lower-cost filter with improved filter rejection and reduced insertion loss, tolerating dielectric material variations and effectively moving spurious/harmonics away from the RF signal passband.
Implementation Method 1
RF dielectric waveguide filter with an interior RF signal channel formed in the body of the filter
Implementation Method 2
a plurality of resonators defined on the block of dielectric material
Data Source
AI summary
A dielectric waveguide filter comprising a block of dielectric material including exterior surfaces covered with a layer of conductive material. A plurality of resonators are formed on the block. RF signal input/outputs are formed on the block. An RF signal is transmitted through the block in a serpentine pattern. In one embodiment, a RF signal transmission channel is formed in the block and extends between and surrounding selected ones of the plurality of resonators in a serpentine pattern. In one embodiment, selected ones of the plurality of resonators are comprised of respective islands of dielectric material formed on one of the top and bottom surfaces of the block of dielectric material surrounded by the channel and respective counter-bores formed and extending into the respective islands of dielectric material. In another embodiment, the respective islands of dielectric material and counter-bores defining the respective resonators are formed in opposed top and bottom surfaces of the block.