Multiplexer Using 90-Degree Hybrids for RF Isolation
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Solution Overview
Problem
Existing duplexers for mobile communication systems require large circuit configurations to achieve high isolation between transmission and reception signals while maintaining electric power handling capability, leading to increased size and complexity.
Innovation Solution
A multiplexer configuration using two 90° hybrids and filters with specific characteristics, such as band elimination, low-pass, and high-pass filters, to achieve high isolation between radio frequency signal paths of different frequency bands, reducing the overall size and propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two hybrids and two band pass filters are disposed to achieve high isolation between transmission and reception signals, then isolation characteristics are improved, but circuit configuration size increases
Solution Approach 1:
The patent combines the functions of two separate hybrids and two band pass filters into a single integrated multiplexer unit. The first and second 90° hybrids are merged with first, second, and third filters within one circuit configuration, achieving high isolation characteristics while reducing the overall circuit footprint compared to the conventional separate hybrid and filter arrangement.
Solution Approach 2:
The multiplexer is designed to perform multiple functions simultaneously: it provides isolation between transmission and reception signals, filters different frequency bands (reception band and transmission bands), and combines signals from multiple paths. This multi-functionality is achieved through the integrated configuration of hybrids and filters that handle both Tx and Rx signals within a single circuit unit.
2Reliability
If additional filters are added to secure isolation and attenuate harmonics in transmission and reception paths, then isolation and signal quality are improved, but device complexity increases
Solution Approach 1:
The patent merges multiple filtering functions into a unified filter system. The first filter (band elimination filter) and second filter (low-pass or high-pass filter) are integrated with the hybrid structures, eliminating the need for separate harmonic attenuation filters in the transmission and reception paths. This integration maintains signal quality while reducing circuit complexity.
Solution Approach 2:
The filters in the multiplexer perform multiple functions simultaneously: the band elimination filter attenuates transmission band signals in the reception path, while the low-pass or high-pass filter handles harmonic attenuation and frequency selection. This multi-functionality reduces the total number of filter components needed compared to conventional separate filter arrangements.
3Power
If conventional duplexer configuration is used to handle high electric power, then power handling capability is maintained, but propagation loss increases
Solution Approach 1:
The patent combines signal combining and filtering functions within the integrated multiplexer structure. By merging the hybrids and filters into a single unit with optimized internal signal paths, propagation loss is reduced compared to conventional duplexers that require separate hybrid and filter stages. The integrated design minimizes the number of signal path transitions while maintaining high power handling capability.
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 solution miniaturizes the duplexer while maintaining high isolation between signal paths, enhancing electric power handling capability and reducing propagation loss, making it suitable for mobile communication base stations.
Implementation Method 1
a first 90° hybrid that is connected to an antenna terminal, includes a plurality of transmission lines, and is configured to shift, with respect to a radio frequency signal passing through one transmission line of the plurality of transmission lines, a phase of a radio frequency signal passing through another transmission line by approximately 90 degrees
Implementation Method 2
a second filter and a third filter connected to both the first 90° hybrid and the second 90° hybrid, and mutually having the same filter characteristics, wherein each of the second filter and the third filter is any one of a band elimination filter configured to reflect a radio frequency signal of a first pass band
Implementation Method 3
a low-pass filter configured to reflect a radio frequency signal of a radio frequency band including the first pass band and allow a radio frequency signal on a lower frequency side relative to the radio frequency band to pass through
Implementation Method 4
a high-pass filter configured to reflect a radio frequency signal of a low frequency band including the first pass band and allow a radio frequency signal on a higher frequency side relative to the low frequency band to pass through
Data Source
AI summary
A duplexer includes a 90° hybrid connected to an antenna terminal, a 90° hybrid connected to a terminating resistor, a transmission-side filter connected to the 90° hybrid connected to the antenna terminal, and notch filters connected to both of the 90° hybrids and mutually having the same filter characteristics, where each of the notch filters is a band elimination filter configured to reflect a radio frequency signal of a transmission band and allow a radio frequency signal of a band other than the transmission band to pass through.