Tuned Hybrid Isolation Circuit for Full-Duplex Signal Separation
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Solution Overview
Problem
Existing communication systems face challenges in isolating weak incoming signals from strong outgoing signals sharing the same channel, particularly in wideband applications, due to limitations in bandwidth and efficiency of prior art devices such as hybrids, diplexers, and directional devices.
Innovation Solution
A method and apparatus that utilize a differencing amplifier with filtered outgoing and incoming signals, where the filters are configured to provide identical frequency responses and include phase shifting and attenuation, ensuring effective cancellation of the outgoing signal and isolation of the incoming signal, using a driver amplifier and termination impedance to match channel impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a voltage source with low output impedance is used to provide transmit signals, then the transmit signal can be effectively delivered to the channel, but the voltage source's bandwidth limitations impede high-frequency operation and wideband communication
Solution Approach 1:
The patent divides the isolation function into multiple frequency-dependent paths using resistors, capacitors, and inductors. Each component handles specific frequency ranges, with capacitors blocking DC and low frequencies while passing high frequencies, and inductors providing impedance at specific frequency ranges. This segmentation allows the circuit to operate effectively across wide bandwidth without requiring an ultra-high bandwidth voltage source.
Solution Approach 2:
The patent introduces intermediate isolation components (resistors RS, R1, R2 and reactive components) between the voltage source and the differencing amplifier. These intermediaries filter and condition the transmit signal at multiple stages, allowing the voltage source to operate at lower bandwidth while still achieving wideband isolation through the combined effect of all isolation components.
2Power
If the power level of the outgoing transmit signal is increased to ensure adequate transmission, then the transmit signal can overcome channel attenuation, but the receive signal becomes impossible to isolate due to the overwhelming transmit signal power
Solution Approach 1:
The patent converts the harmful overwhelming transmit signal into a beneficial cancellation mechanism. The differencing amplifier subtracts a replicated and phase-inverted version of the transmit signal from the receive signal path. By intentionally recreating and inverting the transmit signal, the circuit transforms the harmful interference into a useful cancellation effect, enabling receive signal isolation even when transmit power is high.
Solution Approach 2:
The patent applies counterbalancing by introducing an equal and opposite transmit signal replica into the receive path through the differencing amplifier. This counter-signal acts as an anti-weight to cancel out the harmful transmit signal leakage, allowing the weak receive signal to be isolated despite the presence of strong transmit signals at high power levels.
3Reliability
If prior art hybrid circuits with resistive bridges are used to isolate transmit and receive signals, then basic isolation can be achieved, but the circuits suffer from bandwidth limitations and inefficiency in wideband applications
Solution Approach 1:
The patent changes the impedance parameters across frequency by using reactive components (capacitors and inductors) in addition to resistors. The capacitive reactance decreases with increasing frequency while inductive reactance increases, creating frequency-dependent impedance transformations that enable wideband operation. This parameter change with frequency allows the circuit to maintain effective isolation across wide bandwidth, overcoming the fixed impedance limitations of prior art resistive hybrids.
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 approach enables accurate isolation of incoming signals with minimal attenuation of outgoing signals, maintaining high-frequency operation and reducing noise and distortion, thus overcoming the limitations of prior art in wideband communication systems.
Implementation Method 1
the filters are configured to provide identical frequency responses and include phase shifting and attenuation
Implementation Method 2
the filters are configured to provide identical frequency responses and include phase shifting and attenuation
Implementation Method 3
ensuring effective cancellation of the outgoing signal and isolation of the incoming signal
Implementation Method 4
using a driver amplifier and termination impedance to match channel impedance
Data Source
AI summary
A method and apparatus for isolating transmit and receive signals in a communication system utilizing a common channel for both incoming and outgoing signals. In one embodiment a tuned hybrid or isolation circuit is provided with a high-frequency pre-emphasis response. The tuned hybrid rejects the transmit signal from the receive port and is capable of isolating the low power receive signal. One or more filters within the hybrid provide the desired levels of attenuation and frequency specific processing. Outgoing transmit signals encounter minimal attenuation thereby reducing overall transmit power requirements while receive signals are isolated. The tuned hybrid may be configured with an all-pass network consisting of an attenuator and a delay element. Both of these devices or elements maybe tuned to tailor the frequency response to the channel.