PAM Signal Amplifier Circuit for Linearity and Eye Height Control
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Solution Overview
Problem
High-level pulse amplitude modulation signals, such as PAM-4, experience linearity degradation when passing through amplifiers, leading to increased bit error ratio (BER) and reduced communication sensitivity and speed due to non-linearity issues.
Innovation Solution
A pulse amplitude modulation signal processing circuit with a main amplifier and an auxiliary amplifier connected in parallel, where the auxiliary amplifier variably amplifies the input signal based on a linearity improvement control signal to correct the non-linearity, using a MOSFET device configuration to adjust the operating point and maintain equal eye heights between voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single amplifier is used to amplify PAM-N signals, then the circuit structure is simple, but the linearity of the output signal is degraded
Solution Approach 1:
The amplifier is divided into a main amplifier and an auxiliary amplifier. The main amplifier provides the primary amplification function, while the auxiliary amplifier specifically targets and corrects non-linear distortion components. This segmentation allows each amplifier to have specialized functions, improving overall linearity without requiring a completely complex new architecture.
Solution Approach 2:
The auxiliary amplifier acts as an intermediary that processes the output of the main amplifier and injects correction signals back into the signal path. This intermediary component specifically addresses the non-linearity issue by adding compensating signals that cancel out the distortion products generated by the main amplifier.
2Power
If amplifier gain is increased to improve signal strength, then signal amplitude is enhanced, but non-linearity increases and eye height uniformity degrades
Solution Approach 1:
The system employs feedback mechanisms where the auxiliary amplifier monitors the output signal quality and adjusts its correction signals accordingly. This feedback loop enables the system to maintain eye height uniformity across different signal amplitudes by dynamically compensating for non-linear effects that become more pronounced at higher gain levels.
Solution Approach 2:
The auxiliary amplifier dynamically adjusts its operating parameters to match the signal conditions. By changing its gain and correction characteristics based on the input signal level, the system maintains optimal linearity correction across the full dynamic range of the PAM-N signal, ensuring uniform eye heights regardless of the main amplifier's gain setting.
Data Source
AI summary
A circuit for processing an N-level pulse amplitude modulation (PAM-N) signal according to an embodiment of the present invention comprises: an input unit receiving an input signal; a main amplifier connected to the input unit to amplify the input signal with a first gain; and an output unit outputting an output signal of the main amplifier, and the circuit further comprises an auxiliary amplifier connected in parallel with the main amplifier between the input unit and the output unit to variably amplify at least a portion of the input signal and apply the signal to the output unit according to a linearity improvement control signal corresponding to the output signal.