Antenna Duplexer Harmonic Suppression via Inductance Tuning
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Solution Overview
Problem
Conventional antenna duplexers fail to provide sufficient attenuation of spurious signals caused by harmonics in the transmission signal, as they have high impedance at frequencies higher than the transmission frequency band, leading to inadequate suppression of these spurious signals.
Innovation Solution
The antenna duplexer incorporates a transmission filter with a specific configuration of series and parallel resonators and inductance elements, where the inductance of one inductance element is lower than the other, creating an LC series resonant circuit with low impedance at higher frequencies, thereby producing a larger attenuation at frequencies beyond the pass band, effectively suppressing spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional transmission filter with small capacitance COP3 and inductance element LSER2 is used, then the filter structure is simple, but the attenuation at frequencies higher than the transmission band is insufficient, failing to suppress harmonics
Solution Approach 1:
The transmission filter is divided into multiple stages with series resonators (3, 4, 5) and parallel resonators (7, 8, 9) arranged in a ladder configuration. Each resonator stage contributes to different frequency attenuation characteristics, collectively achieving both passband transmission and stopband suppression of harmonics
Solution Approach 2:
The patent optimizes the capacitance values of parallel resonators (particularly increasing COP3) and inductance values (LSER2, L1, L11) to specific ranges. These parameter changes enable the filter to produce adequate attenuation poles at frequencies above the transmission band, effectively suppressing harmonics while maintaining structural feasibility
2Object-generated harmful factors
If the capacitance COP3 of parallel resonator 9 is increased to improve harmonic suppression, then the attenuation at high frequencies improves, but the impedance Z1 decreases, affecting the attenuation pole position
Solution Approach 1:
The patent specifies optimal capacitance ranges for parallel resonators (particularly COP3) and corresponding inductance values. By carefully adjusting these parameters, the filter achieves adequate impedance Z1 that positions attenuation poles correctly in the harmonic frequency regions while maintaining harmonic suppression capability
Solution Approach 2:
The filter design allows for dynamic adjustment of resonator parameters to optimize performance. The interconnected resonators can be tuned to achieve the desired balance between impedance levels and attenuation pole positions across different operating conditions
3Measurement precision
If a ladder type filter with multiple resonators is used, then the frequency selectivity improves, but the device complexity increases
Solution Approach 1:
The filter is segmented into discrete resonator units (series resonators 3, 4, 5 and parallel resonators 7, 8, 9) that can be independently designed and optimized. This modular segmentation achieves high frequency selectivity through cumulative effect while allowing standardized manufacturing of individual units
Solution Approach 2:
Multiple resonators are combined in a ladder configuration where series and parallel resonators work together to achieve both transmission and attenuation functions. This merging of multiple simple resonator elements creates a complex frequency response with high selectivity without requiring a single complex filter structure
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
This configuration ensures sufficient suppression of spurious signals caused by harmonics in the transmission signal, enhancing communication quality in devices like mobile phones by effectively filtering out unwanted frequencies.
Implementation Method 1
Transmission filter 1 includes input terminal 2, series resonator 3 connected to input terminal 2, series resonator 4 connected to an output port of series resonator 3, series resonator 5 connected to an output port of series resonator 4
Implementation Method 2
An LC series resonant circuit composed of parallel resonator 9 and inductance element 11 has impedance Z1. Z1=jωLSER2+1/(jωCOP3). In transmission filter 1, since capacitance COP3 of parallel resonator 9 is small, impedance Z1 is high at the frequency higher than the transmission frequency band
Data Source
AI summary
An antenna duplexer includes a transmission filter and a reception filter both coupled with an antenna terminal. The transmission filter has a lower pass band than the reception filter. The transmission filter includes a first series resonator coupled with a first terminal, a second series resonator connected to the first series resonator at a first node, a first parallel resonator connected to a first port of the first series resonator, a second parallel resonator connected to a first node and the first parallel resonator at a second node, a third parallel resonator connected to the first node, a fourth parallel resonator connected to the third parallel resonator at a third node, a first inductance element coupled with the second node and a ground, and a second inductance element coupled with the third node and the ground. The second inductance element has a lower inductance than the first inductance element.