Capacitive-Coupled Bandpass Filter With Harmonic Suppression Notches
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Solution Overview
Problem
Conventional capacitive-coupled bandpass filters do not provide adequate harmonic suppression, particularly at higher frequencies, limiting their effectiveness in modern wireless communications applications.
Innovation Solution
A capacitive-coupled bandpass filter design incorporating multiple series coupling capacitors and shunt arms with L/C resonators, configured to provide harmonic suppression notches at specific frequencies, such as 2.4 GHz and 5.4 GHz, while maintaining low insertion loss and a sharp frequency cut-off profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional capacitive-coupled bandpass filter topology is used, then insertion loss is reduced at higher frequencies, but harmonic suppression becomes inadequate
Solution Approach 1:
The filter is divided into multiple functional sections: series coupling capacitors for signal transmission, shunt resonators for harmonic suppression, and parallel resonators for additional harmonic rejection. Each section performs a specific function, allowing the filter to achieve both low insertion loss in the passband and strong harmonic suppression simultaneously.
Solution Approach 2:
Different parts of the filter have specialized characteristics optimized for their specific functions. The series capacitors are optimized for minimal loss signal coupling, while the shunt and parallel resonators are tuned to specific harmonic frequencies for targeted suppression. This local optimization allows each component to excel at its specific task while contributing to overall filter performance.
2Object-generated harmful factors
If more filter elements are added to improve harmonic suppression, then device complexity increases
Solution Approach 1:
The resonators in the filter serve multiple functions: they provide harmonic suppression at their resonant frequencies while also contributing to the overall frequency selectivity and impedance matching of the filter. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The shunt resonators and parallel resonators are combined in a compact arrangement where they work together to suppress multiple harmonics. By merging these functions into a coordinated structure rather than separate independent stages, the filter achieves strong harmonic suppression without proportionally increasing complexity.
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 improved harmonic suppression with insertion losses greater than 30 dB at harmonic suppression frequencies and less than 1.1 dB in the passband, ensuring effective performance in high-frequency wireless communications.
Implementation Method 1
shunt resonators. In the example shown in FIG. 1, the filter 100 includes a pair of shunt resonators 120. Each shunt resonator 120 includes an inductor 122 connected in parallel with a capacitor 124
Implementation Method 2
The capacitive-coupled bandpass filter 100 includes a plurality of series capacitors 110 connected in series with one another along a series path 106 between an input contact 102 and an output contact 104
Data Source
AI summary
Examples of a capacitive-coupled bandpass filter include a plurality of coupling capacitors connected in series along a signal path extending between an input contact and an output contact, a first harmonic suppression notch circuit configured to provide a first harmonic suppression notch in a frequency response of the capacitive-coupled bandpass filter, and a second harmonic suppression notch circuit configured to provide a second harmonic suppression notch in the frequency response of the capacitive-coupled bandpass filter. The first harmonic suppression notch circuit includes a first pair of series L/C resonators connected in shunt between the signal path and a reference potential, and the second harmonic suppression notch circuit includes a second pair of series L/C resonators connected in shunt between the signal path and the reference potential.