Capacitor-Coupled Receiver Interface for Bandwidth Enhancement
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Solution Overview
Problem
Conventional receiver interfaces for AC-coupled communications systems face issues with parasitic capacitance and bandwidth narrowing due to resistor-based networks, which require complex tuning and introduce high-frequency signal loss.
Innovation Solution
A capacitor-coupled receiver interface that allows independent configuration of low-frequency gain and pole location using a passive filter and AC coupler circuit, eliminating the need for switches in the signal path and reducing parasitic capacitance, thereby enhancing bandwidth and signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a resistor-based network is used to attenuate low-frequency signals, then low-frequency attenuation is achieved, but parasitic capacitance increases and bandwidth narrows
Solution Approach 1:
The patent changes the fundamental parameter of the coupling method from resistive coupling to capacitive coupling. By using a capacitor as the coupling element instead of resistors, the circuit achieves low-frequency attenuation through the capacitor's impedance characteristics (Zc = 1/jωC) without introducing the parasitic capacitance problems associated with resistor-based networks. This parameter change resolves the contradiction by maintaining bandwidth while achieving the desired low-frequency disturbance rejection.
2Adaptability or versatility
If multiple resistors are tuned simultaneously to configure low-frequency attenuation, then pole location is configured, but device complexity increases
Solution Approach 1:
The patent extracts the tuning complexity from the circuit by eliminating the need for multiple resistors that require simultaneous adjustment. The capacitive coupling approach with a single capacitor value determines the pole location through the formula pole = 1/(2πRC), where R is the load resistance. This extraction of the tuning parameter simplifies the device from requiring multi-resistor simultaneous tuning to requiring only a single capacitor selection, thereby reducing device complexity while maintaining adaptability.
3Object-affected harmful factors
If AC coupling is used to reduce DC offsets, then DC offset effects are reduced, but additional AC couplers are required
Solution Approach 1:
The patent applies the universality principle by designing the capacitive coupling circuit to perform multiple functions simultaneously. The same capacitor that provides AC coupling to block DC offsets also serves as the equalization element that attenuates low-frequency signals and sets the pole location. This multi-functional design eliminates the need for separate AC couplers in many applications, reducing device complexity while maintaining the ability to reject DC offsets.
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 solution enables separate tuning of low-frequency gain and pole location, improving bandwidth and reducing signal loss, while maintaining high-frequency integrity and eliminating the need for external capacitance charging, thus addressing the limitations of resistor-based networks.
Implementation Method 1
a capacitor coupled between a first node responsive to receive an input signal and a second node
Implementation Method 2
an equalizer to equalize channel loss by attenuating low-frequency energy while maintaining high-frequency energy
Data Source
AI summary
An apparatus includes a capacitor coupled between a first node responsive to receive an input signal and a second node. The apparatus includes a first circuit coupled to the second node and a third node. The first circuit is selectively operable to separately configure at least one of a low-frequency gain of an equalizer and a pole of the equalizer. The equalizer includes the first circuit and the capacitor. The second node is responsive to receive an equalized version of an AC signal of the input signal in a first mode of the apparatus. The second node is responsive to receive a non-equalized version of the AC signal of the input signal in a second mode of the apparatus. The equalized version of the AC signal of the input signal may be a level-shifted and equalized version of the AC signal in the first mode of the apparatus.