Directional Coupler Defected Ground Structure Broadband Compensation
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Solution Overview
Problem
Directional couplers used in high-frequency applications face challenges in achieving broad bandwidth compensation for frequency response, leading to significant deviations in signal magnitude and high manufacturing costs due to the use of expensive chip capacitors and complex bonding processes.
Innovation Solution
Incorporating a defected ground structure with a parallel RLC resonator circuit and resistor elements between the coupling element and measuring port, which reduces manufacturing costs and improves frequency response compensation across a broader bandwidth by altering the signal line's capacitance and inductance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chip capacitors are used to compensate frequency response, then bandwidth compensation is improved, but manufacturing cost increases due to bonding processes
Solution Approach 1:
The patent replaces expensive chip capacitors with a defected ground structure that achieves frequency response compensation without requiring additional discrete components. The DGS is integrated directly into the substrate, eliminating the need for costly bonding processes while maintaining broadband compensation performance from 100 MHz to 5 GHz and beyond.
2Measurement precision
If capacitance elements are used to compensate frequency response, then frequency response precision is improved, but bandwidth is limited
Solution Approach 1:
The patent transforms the frequency response compensation mechanism by changing the physical parameters of the ground structure itself. By introducing a defected ground structure with specific geometric parameters (size, shape, position), the patent achieves broadband frequency response compensation that extends beyond the limited bandwidth of traditional capacitance elements, covering 100 MHz to 5 GHz and higher frequencies.
3Power
If traditional voltage divider with resistors is used, then high current load capability is improved, but frequency response deviation increases
Solution Approach 1:
The patent merges the voltage divider function with the frequency response compensation function into a single integrated structure. The defected ground structure is combined with the resistive voltage divider, allowing the system to maintain high current load capability while simultaneously achieving broadband frequency response compensation with less than 1 dB deviation across 100 MHz to 5 GHz.
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 provides a directional coupler with reduced manufacturing costs and improved precision in high-frequency signal derivation, achieving less than 1 dB deviation in frequency response magnitude from 100 MHz to 5 GHz, suitable for broadband amplifier and EMC applications.
Implementation Method 1
A defected ground structure in the metallic ground plane leads to a disturbance of the shield current distribution in the ground plane caused by the defect in the ground. This disturbance changes the characteristics of the signal line such as line capacitance and line inductance.
Implementation Method 2
A first extension and a second extension increase the route length of current and the effective inductance of the signal line.
Implementation Method 3
The equivalent circuit of a defected ground structure is a parallel RLC resonator circuit, also called oscillating circuit.
Implementation Method 4
The equivalent circuit of a defected ground structure is a parallel RLC resonator circuit, also called oscillating circuit. To insert a defected ground structure into the metallic ground plane of the signal line therefore can electrically be expressed by insertion of a parallel RLC circuit in series in the signal line
Data Source
AI summary
A directional coupler is configured to provide a forward and/or a backward signal derived from a high-frequency signal. The directional coupler comprises a coupling element coupled to a main line, wherein the main line is configured to transport the high frequency signal. The directional coupler further comprises a signal line connecting the coupling element to a measuring port. The signal line comprises a defected ground structure inserted between the coupling element and the measuring port.