90 Degree Hybrids and Quadplexers for Interband Isolation
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Solution Overview
Problem
Existing circuit arrangements, such as quadplexers, fail to provide sufficient isolation between transmission and receiving ports for interband carrier aggregation, especially for closely spaced frequency bands like bands 2 and 4, leading to inadequate Tx to aggregated Rx isolation.
Innovation Solution
A circuit arrangement comprising 90-degree hybrids and two quadplexers, each with a duplexer, is used to achieve phase-shifted signal interference, ensuring destructive interference of leakage signals at receiving ports and constructive interference at the antenna port, thereby enhancing isolation between transmission and receiving ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diplexer is used to separate frequencies, then frequency separation is achieved, but sufficient isolation between closely spaced bands cannot be provided
Solution Approach 1:
The system divides the frequency separation function into multiple components: a first duplexer for band 2, a second duplexer for band 4, and two 90-degree hybrids that create separate signal paths. Each component handles specific frequency bands, and their combined operation provides the necessary isolation that a single diplexer cannot achieve for closely spaced bands.
Solution Approach 2:
The 90-degree hybrids act as intermediary components that split and recombine signals with specific phase relationships. These hybrids mediate between the duplexers and the antenna ports, creating destructive interference for leakage signals and enabling sufficient isolation between closely spaced frequency bands.
2Adaptability or versatility
If a quadplexer is used to support carrier aggregation, then multiple frequency bands can be handled, but Tx to aggregated Rx isolation is insufficient
Solution Approach 1:
The isolation function is segmented across multiple independent paths: signals from the first transmission port pass through the first duplexer and first 90-degree hybrid, while signals from the second transmission port pass through the second duplexer and second 90-degree hybrid. This segmentation allows each path to be optimized for its specific band, achieving sufficient isolation between Tx and aggregated Rx ports.
Solution Approach 2:
The system converts the harmful leakage signal into a beneficial effect by using destructive interference. The 90-degree hybrids are configured so that leakage signals traveling from transmission ports to receiving ports are phase-shifted and combined in opposite phases, causing them to cancel each other out and achieve the required isolation.
3Reliability
If additional resonators or structures are added to the Tx filter, then Tx to Rx isolation is improved, but Tx insertion loss increases
Solution Approach 1:
The 90-degree hybrids serve as intermediary components that provide isolation without requiring additional resonators in the transmission filter paths. By using the phase-shifting and destructive interference properties of the hybrids, the system achieves high isolation while maintaining low insertion loss, avoiding the energy losses that would result from adding more filtering elements.
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 configuration provides improved Tx to Rx and Tx to aggregated Rx isolation, supporting interband carrier aggregation without the need for additional antennas, and increases reception bandwidth by effectively separating frequencies in closely spaced bands.
Implementation Method 1
90 degree hybrids being configured to transfer an input signal into two output signals that are phase shifted relative to each other
Implementation Method 2
The quadplexers and the 90 degree hybrids are interconnected such that a leakage signal travelling from one of the transmission ports to one of the receiving ports destructively interferes at the receiving port
Data Source
AI summary
A circuit arrangement includes an antenna port, a first receiving port, a second receiving port, a first transmission port, and a second transmission port. A number of 90 degree hybrids are configured to transfer an input signal into two output signals that are phase shifted relative to each other. Two quadplexers each include a first duplexer and a second duplexer. The quadplexers and the 90 degree hybrids are interconnected such that a leakage signal travelling from one of the transmission ports to one of the receiving ports destructively interferes at the receiving port.