Balanced Active Duplexer for Wideband Isolation
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Solution Overview
Problem
Existing duplexer technologies suffer from narrow band operation and sensitivity to phase response, leading to limited isolation improvement between transmitters and receivers, especially in SAW filters, and are ineffective when antenna impedance matching is poor.
Innovation Solution
The introduction of a balanced active cancellation unit with a coupler, an active component with a variable attenuator and phase shifter, and a second coupler for 180-degree phase shifting, along with a passive 90° hybrid coupler for signal splitting and combining, to enhance noise cancellation across a wider bandwidth and improve impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional active cancellation loop with a single coupler is used, then isolation improvement can be achieved at a specific frequency, but the bandwidth is narrow and the system is highly sensitive to phase response variations
Solution Approach 1:
The single cancellation path is segmented into two parallel cancellation paths, each with its own coupler, duplexer, active component, and phase shifter. This segmentation allows independent optimization of each path and extends the overall bandwidth by combining multiple narrowband responses
Solution Approach 2:
Two separate cancellation paths are merged in parallel to achieve broadband isolation improvement. The combined effect of both paths provides wider frequency coverage and reduced sensitivity to phase variations compared to a single path
2Reliability
If active tuning components (variable attenuator and phase shifter) are used to achieve cancellation, then isolation can be improved at the target frequency, but the device complexity and control requirements increase
Solution Approach 1:
Different components within each cancellation path have specialized functions optimized for their local role: couplers for signal sampling/injection, duplexers for frequency separation, active components for amplitude control, and phase shifters for phase adjustment. This local optimization reduces the need for complex global control
3Reliability
If a filter-based duplexer is used in the cancellation loop, then cancellation can be achieved, but the phase response is problematic and limits the bandwidth of isolation improvement
Solution Approach 1:
The duplexer components are selected to serve multiple functions: providing frequency separation for the cancellation signal while also having phase responses that, when combined in parallel, extend the bandwidth of isolation improvement. The same duplexer type can be used in both cancellation paths
4Reliability
If the antenna impedance matching is poor, then the cancellation loop has limited effect on signal leaking, but improving impedance matching increases system complexity
Solution Approach 1:
The parallel cancellation path configuration provides inherent robustness to impedance variations. The system self-adjusts by distributing the cancellation function across two paths, reducing the sensitivity to poor antenna matching without requiring additional impedance matching components
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 achieves improved isolation between transmitter and receiver over a wider bandwidth with minimal insertion loss and adaptive tuning, effectively addressing the limitations of prior art by ensuring signal cancellation across cellular frequencies without the need for extensive control elements.
Implementation Method 1
an active component receiving the simulated signal and providing an amplified signal having a phase 180 degree shifted with respect to the simulated signal
Implementation Method 2
a coupler sampling a signal to transmit provided by the transmitter
Implementation Method 3
a coupler for injecting said simulated signal at the receiver
Implementation Method 4
a passive 90° hybrid coupler for signal splitting and combining
Data Source
AI summary
An active cancellation unit is disclosed for improving the noise cancellation between a transmitter and a receiver which are connected to an antenna using a duplexer, the unit comprising a coupler sampling a signal to transmit provided by the transmitter, a cancellation duplexer having characteristics similar to the duplexer and receiving the sampled signal to provide a simulated signal and an active component receiving the simulated signal and providing an amplified signal having a phase 180 degree shifted with respect to the simulated signal; and a coupler for injecting the simulated signal at the receiver.