RF Filter Assembly With Reflective Loads For Transmission Zeros
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Solution Overview
Problem
Existing filters face challenges in achieving high attenuation in the stop-band while maintaining low insertion loss in the pass-band, often requiring large and complex designs with limited transmission zeros, which complicates their manufacturing and increases component count.
Innovation Solution
A filter assembly that incorporates a coupler and reflective loads with overlapping pass-bands and stop-bands to introduce deep and broad transmission zeros, allowing for reduced component size and complexity by carefully arranging the positions of pass-bands and stop-bands, and using quarter wave impedance transformers to compensate for impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high order filter is deployed to achieve small frequency separation between pass-band and stop-band, then the guard band requirement is met, but the number of components increases and physical size increases
Solution Approach 1:
The filter is divided into multiple cascaded filter stages, each contributing to the overall frequency separation requirement. This segmentation allows achieving high order filtering performance while maintaining manageable component counts at each stage
Solution Approach 2:
The patent introduces transmission zeros in the frequency domain to achieve additional attenuation without increasing the temporal dimension (number of components). By placing zeros at specific frequency locations, enhanced stop-band rejection is achieved without proportionally increasing component count
2Manufacturing precision
If a high order filter is deployed to achieve small frequency separation between pass-band and stop-band, then the guard band requirement is met, but the physical size increases
Solution Approach 1:
The filter is divided into multiple cascaded filter stages, each contributing to the overall frequency separation requirement. This segmentation allows achieving high order filtering performance while maintaining manageable component counts at each stage
Solution Approach 2:
The patent introduces transmission zeros in the frequency domain to achieve additional attenuation without increasing the temporal dimension (number of components). By placing zeros at specific frequency locations, enhanced stop-band rejection is achieved without proportionally increasing component count
3Loss of energy
If existing filter architectures with transmission zeros are used, then attenuation is increased, but the filters are difficult and complex to manufacture, occupy large space, and have high insertion losses
Solution Approach 1:
The filter is divided into multiple cascaded filter stages, each contributing to the overall frequency separation requirement. This segmentation allows achieving high order filtering performance while maintaining manageable component counts at each stage
Solution Approach 2:
The patent introduces transmission zeros in the frequency domain to achieve additional attenuation without increasing the temporal dimension (number of components). By placing zeros at specific frequency locations, enhanced stop-band rejection is achieved without proportionally increasing component count
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 significant attenuation improvements in the stop-band with minimal insertion loss increase in the pass-band, enabling smaller and less robust components, and allows for the placement of transmission zeros to enhance isolation between transmission and reception channels.
Implementation Method 1
the filter which receives the radio frequency signal and provides the filtered radio frequency signal highly attenuates that radio frequency signal in the stop-band regions of that filter
Implementation Method 2
the portion of the filtered signal within the pass-band of the filtered reflective load is dissipated by the impedances
Implementation Method 3
using quarter wave impedance transformers to compensate for impedance changes
Implementation Method 4
the radio frequency signal within the filtered signal in the pass-band of the filter will not be dissipated by the impedance device, but instead will be reflected back to the coupler to provide an output radio frequency signal
Data Source
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AI summary
A filter assembly is disclosed. The filter assembly is for filtering a radio frequency signal and comprises: a first filter having a first filter pass band and a first filter stop band, the first filter being operable to receive the radio frequency signal and to provide a first filtered radio frequency signal; a coupler operable to receive the first filtered radio frequency signal and to provide a second filtered radio frequency signal; and a pair of filtered reflective loads coupled with the hybrid coupler to receive the first filtered radio frequency signal and to provide the second filtered radio frequency signal, each filtered reflective load comprising a second filter and an impedance device, each second filter having a second filter pass band which overlaps with the first filter stop band. Selecting the pass-band of the filtered reflective loads to overlap with the stop-band of the filter causes two effects. The first is that the portion of the filtered signal within the pass-band of the filtered reflective load is dissipated by the impedances, which provides a deep and broad transmission zero. It will be appreciated that by carefully arranging the position of the pass-bands and stop-bands of the filters, the position and breadth of the transmission zero can be controlled. Secondly, the radio frequency signal within the filtered signal in the pass-band of the filter will not be dissipated by the impedance device, but instead will be reflected back to the coupler to provide an output radio frequency signal. This means that high power does not flow through the filter within the filtered reflective loads and so smaller and less robust components can be used for that filter which reduces its size.