Active Step Attenuator for Adaptive CATV Signal Control
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Solution Overview
Problem
Existing bidirectional CATV systems face challenges in managing return path signal attenuation due to variance in subscriber distances and intermittent ingress noise, with prior solutions like passive step attenuators being inflexible and requiring multiple versions, which increases costs and may not provide precise attenuation.
Innovation Solution
An active step attenuator that automatically adjusts attenuation based on the power of input signals, using a diplex filter with a power circuit to convert RF energy into DC voltage for real-time control of active variable attenuators, allowing for precise power management without external power sources and reducing the need for multiple attenuator versions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive step attenuator is used to provide attenuation in a CATV system, then attenuation can be provided for different frequency bands, but multiple versions must be manufactured and installed to achieve precise attenuation levels
Solution Approach 1:
The patent applies dynamics by making the attenuation characteristic adjustable through a temperature-dependent resistor. By varying the temperature of the resistor (through heating elements or environmental temperature changes), the attenuation level can be continuously adjusted without requiring multiple discrete passive attenuator versions. This transforms a static attenuation device into a dynamic one that can adapt to different attenuation requirements.
Solution Approach 2:
The patent changes the physical parameter of temperature to control attenuation. The temperature-dependent resistor's resistance value changes with temperature, which directly affects the attenuation level in the RF signal path. This allows a single device to provide variable attenuation by simply changing the temperature parameter, eliminating the need for multiple fixed-attenuation versions.
2Measurement precision
If multiple versions of passive step attenuators are manufactured to provide different attenuation levels, then precise attenuation can be achieved, but manufacturing costs and installation complexity increase
Solution Approach 1:
The patent makes a single attenuator device universal by enabling it to perform multiple attenuation functions. Instead of manufacturing separate attenuators for 3dB, 6dB, 9dB, etc., one attenuator with temperature-controlled resistance can provide all these attenuation levels by adjusting its temperature. This multi-functional approach simplifies manufacturing while maintaining precise attenuation control.
Solution Approach 2:
By using a temperature-dependent resistor, the patent allows a single manufactured device to provide variable attenuation levels through parameter change (temperature) rather than requiring multiple manufactured versions. This reduces manufacturing complexity while achieving the same precision in attenuation control.
3Reliability
If a passive step attenuator is used, then attenuation can be provided, but the device cannot adjust to time-varying conditions such as intermittent ingress noise
Solution Approach 1:
The patent introduces dynamics into the attenuator by making its attenuation characteristic time-variable through temperature control. When ingress noise or other interfering signals appear, the system can dynamically adjust the resistor temperature to change the attenuation level in real-time, allowing the device to adapt to time-varying conditions rather than remaining fixed.
Solution Approach 2:
The patent enables feedback control by monitoring the RF signal characteristics (such as detecting ingress noise or signal quality) and adjusting the temperature-dependent resistor accordingly. This feedback mechanism allows the attenuator to automatically adapt its attenuation level to maintain optimal system performance under varying conditions.
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 active step attenuator provides precise and adaptive signal power control, improving signal-to-noise ratio and reducing ingress noise by adjusting attenuation levels in real-time, ensuring optimal system performance across varying conditions with a single device.
Implementation Method 1
using a diplex filter with a power circuit to convert RF energy into DC voltage for real-time control of active variable attenuators
Data Source
AI summary
An active step attenuator can attenuate the RF signal from a cable modem or other RF source. The active step attenuator converts the RF energy into a DC control signal that controls the attenuation applied to the RF signal. The voltage of the control signal is proportional to the RF energy, so that the active step attenuator attenuates a stronger RF signal more than a weaker RF signal. The active step attenuator may be in the form of a diplex circuit, one branch of which passes signals in one frequency band without attenuation and the other branch of which actively attenuates signals in another frequency band.