Duplex Filter Arrangement With Signal Divider And Combiner
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Solution Overview
Problem
Off-the-shelf duplex filters for radio transceivers often fail to meet specific design criteria, particularly in terms of size and cost, and their transmit-receive signal isolation properties are inadequate for modern mobile communication networks.
Innovation Solution
A filter arrangement using two duplex filters with a signal divider and combiner, incorporating 90° couplers and amplifiers, to split and combine transmit and receive signals, improving isolation by generating phase shifts and compensating for leakage signals, thereby reducing the need for additional circuit space and components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single off-the-shelf duplex filter is used, then the device complexity is low, but the transmit-receive signal isolation is insufficient
Solution Approach 1:
The patent divides the single filter function into two separate duplex filters, each handling specific frequency bands. The transmit signal is split into two portions that pass through separate filters before being combined at the antenna, thereby improving isolation by preventing transmit signals from leaking into the receive path through a single filter's insufficient rejection characteristics.
Solution Approach 2:
The patent combines multiple duplex filters and signal processing components (signal splitter, signal combiner, 90° couplers, amplifiers) into an integrated filter arrangement. This merging allows the system to achieve superior transmit-receive isolation while maintaining a compact structure suitable for mobile communication base stations.
2Reliability
If two duplex filters with signal divider and combiner are used, then the transmit-receive signal isolation is improved, but the device complexity increases
Solution Approach 1:
The patent introduces 90° couplers as intermediary components between the signal splitter and the duplex filters, and between the filters and the signal combiner. These couplers provide precise phase control (90-degree phase shifts) that enable constructive interference for transmit signals and destructive interference for leakage signals, thereby improving isolation while maintaining manageable system complexity.
Solution Approach 2:
The patent employs amplifiers with adjustable gain parameters to compensate for signal level differences and optimize the performance of each filter path. By dynamically adjusting amplification parameters, the system achieves consistent transmit-receive isolation across varying operating conditions without requiring excessive hardware redundancy.
3Reliability
If larger and more expensive filters are used, then the transmit-receive signal isolation is improved, but the size and cost of the radio station increase
Solution Approach 1:
Instead of using a single large, expensive high-isolation filter, the patent segments the filtering function across two smaller duplex filters. Each filter operates at lower isolation requirements individually, but their combined effect through the signal splitting and combining architecture achieves the overall high transmit-receive isolation needed, thereby reducing size and cost.
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 filter arrangement enhances transmit-receive signal isolation by 15-20 dB, reduces the size and cost of filters, and maintains constant output levels, addressing the limitations of existing duplex filters in mobile communication networks.
Implementation Method 1
incorporating 90° couplers and amplifiers, to split and combine transmit and receive signals, improving isolation by generating phase shifts
Implementation Method 2
Filters are designed, for example, for a specific frequency band. Signals within that specific frequency band will pass through the filter from a first port to a second port whereas signals outside of the specific frequency band will be prevented from passing through the filter
Implementation Method 3
incorporating 90° couplers and amplifiers, to split and combine transmit and receive signals, improving isolation by generating phase shifts and compensating for leakage signals
Data Source
AI summary
A filter arrangement for filtering a radio transmit signal and radio receive signal, comprising a first duplex filter and a second duplex filter, a signal divider for splitting a transmit input signal into a first transmitter signal portion and a second transmitter signal portion, the first transmitter signal portion being passed to the a transmit port of the first duplex-filter, and a second signal portion being passed to the second transmitter port of the second duplex filter. The filter arrangement further comprising a signal combiner/divider for combining a first filtered transmit portion signal and a second filtered transmit portion signal into a single filtered transmit signal. The filter arrangement further comprising a signal combiner for combining a first filtered receive signal portion and a second filtered receive signal portion into a single filtered receive signal, which is provided at a third output of the signal combiner. With such a filter arrangement the suppression of noise from the transmit signal in the receive signal is improved.