Non-Reciprocal RF Bandpass Filter Isolator Integration
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Solution Overview
Problem
Current full-duplex transceivers require large and complex RF transceivers due to the need for bulky ferromagnetic elements, which hinder integration with IC-based components and increase physical size and power loss.
Innovation Solution
The development of non-reciprocal RF co-designed bandpass filters/isolators (BPFIs) using series cascaded non-reciprocal resonant stages and transmission line-based impedance inverters, combining the functions of an RF bandpass filter and isolator within a single device volume, achieving enhanced power transmission and isolation without magnetic biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic-based circulator/isolator components are used, then non-reciprocal RF filtering function is achieved, but the physical size and device complexity increase significantly
Solution Approach 1:
The patent combines the bandpass filter and isolator into a single integrated device called a bandpass filter/isolator (BPFI). The BPFI merges the filtering function and isolation function into one component, eliminating the need for separate magnetic-based circulator/isolator components. This integration directly reduces the physical footprint while maintaining the non-reciprocal RF filtering function through the use of non-reciprocal resonant stages that provide both filtering and isolation capabilities in a unified structure.
Solution Approach 2:
The BPFI performs multiple functions simultaneously: it acts as a bandpass filter for signal selection and as an isolator for non-reciprocal signal transmission. The non-reciprocal resonant stages provide universal functionality by enabling both filtering and isolation operations within the same device, replacing the need for separate specialized components and thereby reducing overall device complexity and physical size.
2Reliability
If conventional magnetic-based circulator/isolator components are used, then non-reciprocal RF filtering function is achieved, but the device complexity and integration difficulty increase
Solution Approach 1:
The patent merges the bandpass filter and isolator into a single integrated device called a bandpass filter/isolator (BPFI). The BPFI merges the filtering function and isolation function into one component, eliminating the need for separate magnetic-based circulator/isolator components. This integration directly reduces the physical footprint while maintaining the non-reciprocal RF filtering function through the use of non-reciprocal resonant stages that provide both filtering and isolation capabilities in a unified structure.
Solution Approach 2:
The patent replaces the mechanical magnetic-based circulator/isolator system with an electronic implementation using non-reciprocal resonant stages based on transistors and transmission lines. This substitution eliminates the need for bulky ferromagnetic elements and their associated mechanical structures, thereby reducing integration complexity and enabling easier integration with IC-based components while maintaining the non-reciprocal RF filtering function.
3Reliability
If conventional magnetic-based circulator/isolator components are used, then isolation function is achieved, but the power loss increases
Solution Approach 1:
The patent replaces the mechanical magnetic-based circulator/isolator system with an electronic implementation using non-reciprocal resonant stages based on transistors and transmission lines. This substitution eliminates the need for bulky ferromagnetic elements and their associated mechanical structures, thereby reducing integration complexity and enabling easier integration with IC-based components while maintaining the non-reciprocal RF filtering function.
Solution Approach 2:
The patent changes the operational parameters of the resonant stages by using active transistor components (such as pHEMT transistors) that can provide gain and control the non-reciprocal behavior. By adjusting transistor biasing and circuit parameters, the system achieves the required isolation function with reduced power loss compared to passive magnetic-based components, as the active components can compensate for losses and provide signal amplification where needed.
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 solution reduces the physical footprint and power loss of RF front-end components, providing high-order transfer functions, increased selectivity, and isolation while eliminating the need for magnetic-biasing, making them suitable for full-duplex communication, radar, and instrumentation systems.
Implementation Method 1
The non-reciprocity in the resonant stage is achieved by cascading in-parallel a transistor-based stage and a TL-based element with opposite phase responses
Implementation Method 2
when the RF signal is injected at Port 2, the RF signals that arrive in the resonator output—Port 1—are mutually-cancelled through destructive RF signal cancellation
Implementation Method 3
The transistor-based stage is shaped by four resistors and a pHEMT transistor in common-source (CS) configuration that exhibits a positive phase response
Implementation Method 4
by appropriately selecting the TL characteristics a zero-phase resonance can be achieved in the overall resonator-ring—shaped by the TL and the transistor-based stage—when the RF signal is injected in Port 1
Implementation Method 5
Taking into consideration that TL-based elements exhibit a negative phase response
Implementation Method 6
transmission line (TL)-based impedance inverters
Implementation Method 7
in-series cascaded non-reciprocal resonant stages—N for an N-pole BPF response
Data Source
AI summary
RF co-designed bandpass filters/isolators (BPFIs) are based on series-cascaded non-reciprocal resonant stages, microwave resonators and multi-resonant cells. The non-reciprocal stages are shaped by an in-parallel cascaded transistor-based path and a transmission line (TL) that result in a zero-phase resonance in the forward direction and high isolation in the reversed one. This includes coupling routing diagrams (CRDs) of BPFs that result in low- and high-order transfer functions with and without transmission zeros in their forward direction and high levels of isolation in the reverse one. BPFIs provide alternative-type of filtering responses (e.g., flat-passband, quasi-elliptic) with and without gain in the forward direction and high levels of isolation in the reversed one. BPFIs include five planar microstrip/lumped element (LE) prototypes using hybrid combinations of non-reciprocal resonant stages, microwave resonators and multi-resonant cells.