Stacked Die Switch-Filter for Antenna Coupling Reduction
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Solution Overview
Problem
Portable wireless devices face challenges in reducing transmit and receive interference between simultaneously operating radios, particularly due to insufficient spacing between antennas in WLAN radios, which affects spatial diversity and increases antenna coupling.
Innovation Solution
A stacked die configuration of a switch and a filter is used in a wireless front-end module, where the switch is mounted on a filter with a metallized outer surface, forming a common node and reducing electrical couplings, allowing for improved performance and a smaller footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple antennas are used to provide spatial diversity, then data recovery probability increases and nulls caused by multi-path propagation are avoided, but antenna coupling increases and transmit/receive interference occurs when antennas are placed close together
Solution Approach 1:
The patent combines the filter and switch into a single integrated component where the switch is mounted directly on the filter substrate. This merging reduces the overall number of discrete components and interconnections, thereby reducing antenna coupling while maintaining spatial diversity functionality through the integrated switch-filter structure
Solution Approach 2:
The switch acts as an intermediary component between the antenna and the filter, enabling selective connection and disconnection of the antenna to the filter based on transmit/receive mode. This intermediary function allows the system to maintain spatial diversity while controlling interference through proper switching operations
2Object-generated harmful factors
If DPDT switching is used to switch between antennas for spatial diversity, then transmit/receive interference is reduced, but device complexity increases due to multiple switches and control signals
Solution Approach 1:
The patent merges the filter and switch into a single integrated component, reducing the number of discrete components and interconnections. This integration simplifies the overall switching circuit while maintaining the ability to reduce transmit/receive interference through proper switching operations
Solution Approach 2:
The integrated switch-filter component performs multiple functions: filtering, switching, and interference suppression within a single component. This multi-functionality reduces device complexity by eliminating the need for separate filter and switch components while maintaining effective transmit/receive isolation
3Object-generated harmful factors
If the distance between antennas is reduced to less than 20% of a wavelength, then spatial diversity is maintained and antenna coupling is reduced, but available space for antenna placement decreases in compact devices
Solution Approach 1:
The patent combines the filter and switch into a single integrated component mounted on the filter substrate. This merging reduces the overall footprint required for antenna placement while maintaining proper spacing between antennas to reduce coupling and preserve spatial diversity
4Ease of operation
If conventional DPDT switch configuration is used, then switching functionality is achieved, but isolation between transmit and receive paths is insufficient
Solution Approach 1:
The patent integrates the filter and switch into a single component where the switch is mounted on the filter substrate. This integration provides better isolation between transmit and receive paths by reducing parasitic coupling between the switch elements and the filter structure, while maintaining full switching functionality
Data Source
AI summary
Systems and methods are provided for a stacked die configuration of a high isolation switch and a rejection filter where transmit and receive signals are desired to have a high out-of-band rejection and a low loss band-pass region. In some aspects of the invention the high isolation switch is a double pole double throw switch modified to operate as a high isolation single pole double throw (SPDT) switch. In some aspects of the invention the high isolation switch is a conventional high isolation SPDT switch. The switch is mounted on a low profile rejection filter having metallization on a portion of an outer surface of the rejection filter. The metallization on the outer surface of the rejection filter provides an AC ground layer in close proximity to the switch that provides a short coupling path between the switch and the AC ground. The resulting switch-filter component also results in a smaller footprint than if the two devices were mounted individually and/or adjacently. The switch-filter component has applications in devices requiring high isolation between transmit and receive paths, for example use within a front-end module (FEM) of a single antenna, multi-radio device.