Single-Chip Duplexer Shield Layout for Filter Isolation
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Solution Overview
Problem
In portable communication devices, single-chip duplexers face increased interference due to magnetic coupling and capacitive coupling between transmit and receive filters, which degrades isolation characteristics and increases insertion loss, making it challenging to meet the demands for smaller, more efficient, and cost-effective designs that operate at higher frequencies.
Innovation Solution
A single-chip duplexer design incorporating film bulk acoustic resonator (FBAR) or bulk acoustic wave (BAW) filters, with an annular sealing ring and conductive stripe acting as an isolation shield to reduce parasitic capacitance and electromagnetic coupling, thereby enhancing antenna-to-receiver and antenna-to-transmitter port rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If single-chip topology is used to reduce size and weight, then miniaturization is achieved, but interference between transmit and receive filters increases due to magnetic coupling and capacitive coupling
Solution Approach 1:
An isolation shield is introduced as an intermediary element between the transmit filter and receive filter on the single chip. This shield acts as a mediator that blocks magnetic coupling and capacitive coupling between the two filters, allowing them to coexist on the same chip without significant interference while maintaining the miniaturized single-chip topology.
Solution Approach 2:
The single chip is segmented into distinct regions by the isolation shield, separating the transmit filter section from the receive filter section. This segmentation reduces the electromagnetic interaction between the two filters while maintaining their individual functionality, enabling both filters to operate effectively in close proximity on the same chip.
2Device complexity
If filters are placed closer together on a single chip, then device integration is improved, but parasitic capacitance between filters increases
Solution Approach 1:
The isolation shield serves as a protective intermediary that eliminates parasitic capacitance between the transmit and receive filters. By placing this conductive shield between the two filters, the design maintains high integration while preventing the formation of unwanted capacitive coupling that would otherwise occur when filters are positioned close together on a single chip.
3Object-affected harmful factors
If isolation shield is added between filters, then interference is reduced, but device complexity increases
Solution Approach 1:
The isolation shield is implemented as a localized feature only in the critical region between the transmit and receive filters where electromagnetic interference occurs. This targeted approach provides effective interference reduction without adding complexity to the entire duplexer structure, maintaining simplicity in non-critical areas while addressing the specific interference problem where it exists.
Solution Approach 2:
The isolation shield is a relatively simple intermediary element that can be implemented as a conductive layer or pattern on the chip substrate. Despite its simplicity, it effectively reduces interference between filters, providing a low-complexity solution to the interference problem that maintains overall device simplicity while achieving the desired isolation performance.
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 solution improves isolation characteristics, reduces insertion loss, and increases out-of-band attenuation, enabling smaller, more efficient, and cost-effective duplexers that operate effectively at higher frequencies, addressing the interference issues in single-chip designs.
Implementation Method 1
interference between the transmit and receive filters further increases due to the single-chip topology, e.g., resulting in undesirable magnetic coupling and capacitive coupling (i.e., parasitic capacitance or electrical induction) between the transmit and receive filters
Implementation Method 2
undesirable magnetic coupling and capacitive coupling (i.e., parasitic capacitance or electrical induction) between the transmit and receive filters
Implementation Method 3
Such duplexers may include resonators for filtering the transmit and receive signals, such as a thin film bulk acoustic resonators (FBARs) and/or bulk acoustic wave (BAW) resonators
Data Source
AI summary
A single-chip duplexer, interfacing a receiver and a transmitter with a common antenna, includes transmit and receive filters, an annular sealing ring and a conductive stripe. The transmit filter is connected between the antenna and the transmitter, and has a transmit passband. The receive filter is connected between the antenna and the receiver, and has a receive passband different from the transmit passband. The annular sealing ring is connected between a surface of the chip and a surface of a cap to form a sealed cavity between the chip and the cap. The conductive stripe extends across at least a portion of the surface of the chip between the transmit filter and the receive filter, the conductive stripe being directly connected to the sealing ring and electrically connected to ground. The conductive stripe provides at least one of magnetic shielding and capacitive shielding between the transmit filter and the receive filter.