Directional Coupler Flat Amplitude via Phase Shift
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Solution Overview
Problem
Conventional directional couplers exhibit varying power output from the sub line due to frequency-dependent coupling, requiring IC compensation, as the amplitude characteristic of the coupling signal is not flat.
Innovation Solution
Incorporating a low pass filter between the sub lines, which causes a phase shift in the signal, ensuring the amplitude characteristic of the coupling signal is closer to being flat across the frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the frequency of the input signal is increased, then the degree of coupling between the main line and sub line is increased, but the amplitude characteristic of the coupling signal becomes non-flat
Solution Approach 1:
A phase conversion unit is introduced as an intermediary component between the main line and sub line. This unit converts the phase of the signal passing between the lines, thereby compensating for the frequency-dependent coupling variations and achieving a flat amplitude characteristic across the operating frequency band.
Solution Approach 2:
The invention changes the phase parameter of the signal through the phase conversion unit. By adjusting the phase of the coupled signal based on frequency, the system compensates for coupling variations and maintains a flat amplitude characteristic despite changes in coupling degree with frequency.
2Device complexity
If conventional directional coupler design is used, then the device structure is simple, but IC compensation is required to maintain constant power output
Solution Approach 1:
The phase conversion unit serves as an intermediary that actively compensates for coupling variations. Instead of requiring external IC compensation, the phase conversion unit is integrated into the coupler structure itself, simplifying the overall system while maintaining signal power stability.
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 a flat amplitude characteristic for the coupling signal, improving isolation characteristics without increasing component size, and maintaining power proportionality regardless of frequency variations.
Implementation Method 1
a first sub line that is connected to the third terminal and electromagnetically coupled to the main line; a second sub line that is connected to the fourth terminal and electromagnetically coupled to the main line
Data Source
AI summary
A directional coupler used in a predetermined frequency band includes a main line connected between a first terminal and a second terminal. A first sub line is connected to a third terminal and is electromagnetically coupled to the main line. A second sub line is connected to a fourth terminal and is electromagnetically coupled to the main line. A low pass filter is connected between the first sub line and the second sub line and causes a phase shift to be generated in a passing signal passing therethrough in such a manner that the phase shift monotonically increases within a range from about 0 to about 180 degrees with increasing frequency in the predetermined frequency band.