Resonator Duplexer Cross-Coupling for Lower Loss and Higher Rejection
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Solution Overview
Problem
Existing duplexers for portable communication devices face challenges in reducing size, weight, and fabrication costs while achieving improved performance characteristics such as lower insertion loss and higher out-of-band attenuation, especially when operating at higher frequencies and complying with various wireless communication standards.
Innovation Solution
The duplexer design incorporates ladder-type filters with series and shunt resonators, including cross-coupling capacitors and common ground inductors, which shift transmission zeros to align with the center frequencies of the receive and transmit passbands, minimizing overlap and enhancing rejection levels, thereby achieving near-ideal elliptic filter performance without the need for large external inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional band-pass filters are used in duplexers, then the basic filtering function is achieved, but the device size, weight, and fabrication cost cannot be reduced while meeting performance requirements at higher frequencies
Solution Approach 1:
The patent transforms the filter design from traditional lumped-element band-pass filters to distributed resonator-based filters operating at higher frequencies. This parameter change in the fundamental design approach enables lower insertion loss by using resonators with higher quality factors, while the standardized resonator modules simplify the overall design complexity despite the higher operating frequencies
Solution Approach 2:
The filter is segmented into multiple identical or similar resonator modules connected in a ladder configuration. Each resonator module is a standardized unit that can be independently designed and fabricated, reducing overall design complexity while achieving the required filtering performance and lower insertion loss through the cumulative effect of multiple resonators
2Manufacturing precision
If resonators are used to filter transmit and receive signals, then filtering performance is improved, but design and fabrication become difficult due to passband and stopband requirements and matching circuit requirements
Solution Approach 1:
The patent merges the filtering function and impedance matching function into a single integrated resonator ladder structure. The series and shunt resonators simultaneously provide both the required passband/stopband filtering characteristics and the impedance transformation needed for matching to the antenna and transceiver, eliminating the need for separate matching circuits and simplifying fabrication
Solution Approach 2:
The resonator ladder filter structure serves multiple functions simultaneously: it provides band-pass filtering, impedance matching, and transmission zero positioning. This multi-functionality reduces the overall device complexity by consolidating what would traditionally require separate components, while achieving high manufacturing precision in out-of-band attenuation through the resonant characteristics
3Reliability
If cross-coupling elements are added to shift transmission zeros, then out-of-band rejection is improved, but the number of components and manufacturing variables increases
Solution Approach 1:
The cross-coupling elements are pre-configured into the resonator ladder structure during the initial design phase, with their positions and values optimized to automatically position transmission zeros at the desired frequencies. This preliminary integration eliminates the need for post-fabrication adjustments or additional manufacturing steps, maintaining high product yield while achieving superior out-of-band rejection
Solution Approach 2:
The cross-coupling elements are merged with the basic resonator ladder structure to form an integrated filter design. Rather than being separate add-on components, the cross-coupling capacitors or inductors are incorporated as inherent parts of the resonator modules, reducing the total component count and simplifying the manufacturing process while achieving the required transmission zero positioning for improved out-of-band rejection
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 design results in a smaller, more efficient duplexer with improved out-of-band rejection and in-band insertion loss, reducing manufacturing complexities and increasing product yields by allowing for smaller die sizes and fewer manufacturing variables.
Implementation Method 1
a cross-coupling capacitor connected between a first capacitor node connected to at least one of the second series resonators and a second capacitor node connected to one of the second shunt resonators
Implementation Method 2
an inductor connected in series between second capacitor node and ground
Implementation Method 3
The first filter includes at least four first series resonators connected in series between the antenna and one of the receiver and the transmitter, four first shunt resonators respectively connected between at least one of the four first series resonators and ground voltage
Data Source
AI summary
A duplexer interfacing a receiver and a transmitter with an antenna includes first and second filters. The first filter includes at least four first series resonators, four first shunt resonators respectively connected between the four first series resonators and ground voltage, and a mutual inductance commonly connected between two adjacent first shunt resonators. The second filter includes at least four second series resonators, four second shunt resonators respectively connected between the four second series resonators and the ground voltage, and a cross-coupling capacitor connected between a first capacitor node connected to at least one of the second series resonators and a second capacitor node connected to one of the second shunt resonators, and an inductor connected in series between second capacitor node and ground. Three of the second series resonators and the second shunt resonator to which the cross-coupling capacitor is connected are between the first and second capacitor nodes.