Wide Bandwidth Microwave Balun Using Frequency Segmentation
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Solution Overview
Problem
Existing baluns fail to provide the necessary 10:1 frequency bandwidth in the microwave region, limiting their application in signal intelligence and surveillance due to inability to effectively cancel second-order distortion across a wide frequency range.
Innovation Solution
The solution involves dividing incoming signals into high and low frequency bands using diplexers and employing two baluns, one for each band, to achieve a combined full bandwidth output, effectively canceling second-order distortion over a 10:1 frequency range from 2 GHz to 20 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single balun is used in the microwave region, then the device structure is simple, but the frequency bandwidth is limited and cannot achieve 10:1 bandwidth ratio
Solution Approach 1:
The patent divides the wide frequency bandwidth into multiple segments, each handled by a dedicated balun optimized for its specific frequency range. This segmentation allows each balun to achieve high performance within its band while collectively covering the full 10:1 bandwidth ratio, resolving the contradiction between bandwidth and device complexity.
Solution Approach 2:
The patent creates a multi-functional balun system where multiple baluns work together to provide universal coverage across the entire frequency range. Each balun serves multiple purposes: impedance transformation, phase balancing, and distortion cancellation within its optimized band, achieving broad adaptability without requiring a single complex universal design.
2Adaptability or versatility
If ferrite technology is used to achieve wide bandwidth, then the frequency coverage is broad, but the device becomes incompatible with MMIC fabrication and planar form requirements
Solution Approach 1:
The patent replaces ferrite-based mechanical/magnetic components with planar transmission line structures and distributed element circuits that are compatible with MMIC fabrication processes. This substitution maintains the wide bandwidth performance while enabling integration with standard semiconductor manufacturing techniques.
Solution Approach 2:
The patent changes the fundamental operating parameters from relying on ferrite material properties to using distributed LC circuit parameters and transmission line characteristics. This parameter transformation enables the same wide bandwidth function to be achieved through fabrication-compatible planar structures rather than requiring ferrite materials.
3Reliability
If the balun operates from lowest input frequency to twice the highest output frequency to cancel second harmonics, then the distortion cancellation is effective, but the required bandwidth increases beyond practical limits
Solution Approach 1:
The patent segments the frequency range into multiple bands, with each balun optimized to handle second harmonic cancellation within its specific band. This segmentation allows effective distortion cancellation to be achieved across the full bandwidth without requiring any single balun to cover the entire extended frequency range from lowest input to twice the highest output frequency.
Data Source
AI summary
A wide bandwidth microwave balun utilizes frequency band splitting and two conventional baluns operating in a high frequency band and a low frequency band, which when combined offer a full bandwidth output, thus to offer wide bandwidth impedance matching and second-harmonic rejection.