Microwave Filter Stub Embedded Spurline Harmonic Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microwave notch filters require complex circuit structures and increased space to reject specific frequencies while allowing odd harmonics, leading to higher ohmic losses.
Innovation Solution
A microwave filter design that incorporates a stub with an embedded spurline, configured to appear as a short circuit at the central frequency and an open circuit at select odd harmonics, allowing for efficient rejection of the central frequency while passing specific odd harmonics without the need for complex circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple stubs are cascaded to enhance frequency response and extend notch depth, then the notch depth increases (over 55 dB), but the device complexity and space requirements increase
Solution Approach 1:
The spurline is embedded within the stub structure, creating a nested configuration where one resonant element (spurline) is integrated inside another (stub). This nested design allows the filter to achieve enhanced notch depth and harmonic control without requiring multiple separate cascaded stubs, thereby reducing overall device complexity and space requirements while maintaining the desired frequency rejection characteristics
2Adaptability or versatility
If complex circuit structures are used to reject specific frequencies while allowing odd harmonics, then frequency selectivity improves, but ohmic losses increase
Solution Approach 1:
The invention extracts and utilizes the natural resonant properties of the stub-spurline combination to achieve frequency selectivity. By carefully designing the electrical lengths of the stub and embedded spurline, the filter exploits resonant cancellation effects to reject specific frequencies while allowing odd harmonics to pass, thereby achieving high frequency selectivity without requiring additional complex circuit elements that would contribute to ohmic losses
3Loss of energy
If the stub length is set to 1/4 wavelength to reject the central frequency, then the central frequency is effectively rejected, but odd harmonics are also suppressed
Solution Approach 1:
The embedded spurline introduces localized resonant characteristics within the stub structure. By positioning and dimensioning the spurline with specific electrical length (typically 1/12 to 1/20 of the central wavelength), it creates localized resonant effects that selectively affect different frequency components. This local quality modification allows the stub to reject the central frequency while simultaneously permitting odd harmonics to pass through with minimal attenuation
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 design achieves efficient rejection of the central frequency while passing desired odd harmonics with minimal loss, maintaining a simple structure and reducing space requirements, as demonstrated by the examples of rejecting the third harmonic with minimal attenuation.
Implementation Method 1
A stub 708 is connected to the transmission line 702 between the input port 704 and the output port 706. An L-shaped spurline 710 is embedded in the stub 708... the stub includes a spurline so that the stub appears to the transmission line as a short circuit at the center frequency and as an open circuit at higher order odd harmonic frequencies
Data Source
AI summary
A microwave filter is provided that includes a transmission line having a signal input port and a signal output port, a stub connected to the transmission line between the input port and the output port, and a spurline embedded in the stub. The microwave filter is configured to substantially attenuate a frequency while substantially passing at least one predetermined odd harmonic of the frequency.