BAW Duplexer Shunt Inductance Impedance Rotation
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Solution Overview
Problem
Conventional duplexers for transceivers face issues such as large area requirements, high insertion loss due to delay lines or pi-networks, unwanted low pass characteristics, and lack of a DC current path to ground, necessitating additional circuitry for ESD protection.
Innovation Solution
A duplexer design utilizing bulk acoustic wave (BAW) resonators with a shunt inductance between the antenna port and ground, which rotates the input impedance in a negative direction, reducing the need for large substrates and minimizing insertion loss, while providing a DC path to ground for ESD protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmission line or pi-network is used for impedance transformation and phase shifting, then the input impedance is transformed to high values at the Tx frequency range, but the device requires a relatively large area and introduces insertion loss
Solution Approach 1:
The patent changes the impedance transformation approach by using a shunt inductance with a specific value (e.g., 5 nH) instead of a transmission line or pi-network. This parameter change allows achieving the same impedance transformation effect with a much smaller area, as the inductance can be implemented as a compact component or even a bond wire inductance.
Solution Approach 2:
Instead of using a series inductance or transmission line to transform impedance, the patent uses a shunt inductance connected to ground. This inverted approach achieves the same impedance transformation effect but with a different topological configuration that reduces area requirements and insertion loss.
2Reliability
If a transmission line or pi-network is used for phase shifting, then the +90° phase shift is achieved, but insertion loss increases for both Rx and Tx signal paths
Solution Approach 1:
The patent changes the phase shifting mechanism by using a shunt inductance that provides a -90° phase rotation (opposite direction) combined with impedance transformation. This parameter change in the phase shifting approach reduces insertion loss because the shunt inductance configuration is more efficient than transmission lines or pi-networks for achieving the required phase shift.
Solution Approach 2:
The patent converts the typically harmful -90° phase rotation into a beneficial effect by combining it with impedance transformation. The shunt inductance simultaneously achieves both impedance transformation and phase shifting in a way that reduces overall insertion loss, turning what would normally be a disadvantage into an advantage.
3Reliability
If a +90° phase shift is used for impedance transformation, then high input impedance is achieved at Tx frequency, but a DC current path to ground is not provided, requiring additional ESD protection circuitry
Solution Approach 1:
The shunt inductance serves multiple functions simultaneously: it provides impedance transformation, achieves phase shifting, and creates a DC current path to ground for ESD protection. This multi-functionality eliminates the need for separate ESD protection circuitry, reducing device complexity while maintaining impedance transformation effectiveness.
Solution Approach 2:
The patent merges the ESD protection function with the impedance transformation network by using the shunt inductance for both purposes. This combination eliminates the need for separate ESD protection circuitry, as the shunt inductance naturally provides a DC path to ground while achieving the required impedance transformation.
4Reliability
If a delay line is used for impedance transformation, then the input impedance is transformed, but the device enforces use of a multilayer substrate and requires relatively large area
Solution Approach 1:
The patent changes the impedance transformation method from a delay line (which requires multilayer substrates) to a shunt inductance. This parameter change in the transformation mechanism allows for simpler manufacturing, as the shunt inductance can be implemented as a single-layer component or even a bond wire, eliminating the need for complex multilayer substrate structures.
Solution Approach 2:
The patent extracts the impedance transformation function from the delay line structure and implements it separately using a shunt inductance. This extraction allows the use of simpler substrate structures, as the inductance can be implemented independently without requiring the complex multilayer architecture needed for delay lines.
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 proposed duplexer design achieves reduced insertion loss, smaller footprint, and inherent ESD robustness by integrating shunt inductances, improving signal isolation and matching efficiency across frequency bands.
Implementation Method 1
a transmitting filter (300) comprising bulk acoustic wave (BAW) resonators (302, 303, 304, 305) and a receiving filter (320) comprising bulk acoustic wave (BAW) resonators (322, 323, 324, 325)
Implementation Method 2
a shunt inductance (340) coupled between the antenna port and ground, wherein the shunt inductance (340) and the first and second antenna side impedances (350, 360) of the transmitting filter (300) and the receiving filter (320) are selected in such a way that the shunt inductance (340) turns the first and second input impedance in a negative direction in a Smith diagram
Data Source
AI summary
A duplexer for connection with an antenna comprises an antenna port, a transmitting filter comprising bulk acoustic wave (BAW) resonators having a first antenna side impedance coupled with the antenna port, a receiving filter comprising BAW resonators having a second antenna side impedance coupled with the antenna port, and a shunt inductance coupled between the antenna port and ground. The shunt inductance and the first and second antenna side impedances of the transmitting filter and the receiving filter are selected in such a way that the shunt inductance turns the first and second input impedance in a negative direction in a Smith diagram.