Resonant Filter Circuit With Weakly Coupled Stopband Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing band-pass filters in communication systems, particularly for 5G, face challenges in maintaining low insertion loss in the passband and abrupt insertion loss changes near the passband due to increased resonator numbers or improper setting of band elimination filters, leading to deteriorated filter characteristics.
Innovation Solution
A filter circuit design incorporating a master resonant circuit and a slave resonant circuit with weaker coupling, where the slave resonant circuit acts as a band elimination filter, using smaller capacitors to connect with ports, thereby maintaining desired characteristics without increasing the number of resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of resonators is increased to obtain abrupt insertion loss changes near the passband, then the insertion loss characteristics improve, but the passband insertion loss increases
Solution Approach 1:
The filter is divided into two independent resonant circuits (first and second) that can be designed and optimized separately. The first resonant circuit handles the passband characteristics while the second resonant circuit handles the stopband characteristics, allowing independent optimization without compromising the other.
Solution Approach 2:
The second resonant circuit acts as an intermediary element that provides stopband rejection without directly interfering with the first resonant circuit's passband performance. By coupling both circuits to the same ports with controlled impedance, the second circuit shapes the stopband while the first circuit maintains the passband.
2Adaptability or versatility
If a band elimination filter is used to obtain abrupt insertion loss changes near the passband, then the frequency selectivity improves, but the passband insertion loss increases
Solution Approach 1:
Different parts of the filter have different coupling strengths to the ports. The first resonant circuit has stronger coupling for passband operation, while the second resonant circuit has weaker coupling specifically for stopband rejection. This local differentiation allows frequency selectivity without compromising passband performance.
Solution Approach 2:
The coupling parameters (capacitance values) are specifically optimized for each resonant circuit. The first resonant circuit uses larger coupling capacitors for strong passband coupling, while the second resonant circuit uses smaller coupling capacitors for weak stopband coupling, achieving frequency selectivity without passband loss.
3Manufacturing precision
If the coupling strength of the slave resonant circuit is increased to improve stopband rejection, then the frequency selectivity improves, but the passband insertion loss increases
Solution Approach 1:
The filter exhibits dynamic behavior where the coupling strength effectively changes with frequency. At passband frequencies, the first resonant circuit dominates with strong coupling. At stopband frequencies, the second resonant circuit becomes active with its weaker coupling providing the necessary rejection, creating a frequency-dependent coupling effect.
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 abrupt insertion loss changes near the passband while minimizing passband insertion loss and filter size, allowing for efficient frequency adjustment and miniaturization.
Implementation Method 1
a first resonant circuit including a plurality of first resonators, provided between the two ports in a circuit configuration, and coupled with both of the two ports; and a second resonant circuit including a plurality of second resonators
Implementation Method 2
two first capacitors capacitive-coupling the first resonant circuit and the two ports; and at least one second capacitor capacitive-coupling the second resonant circuit and the two ports
Data Source
AI summary
A filter circuit includes two ports, a first resonant circuit, and a second resonant circuit. The first resonant circuit is provided between the two ports in a circuit configuration and coupled with both of the two ports. The second resonant circuit is provided between the two ports in the circuit configuration and coupled with at least one of the two ports. Coupling of the second resonant circuit and the two ports is weaker than coupling of the first resonant circuit and the two ports.