PLL Compensation Filter for Bandwidth Expansion and Signal Fidelity
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Solution Overview
Problem
Phase locked loops in wireless signal transmitting devices, such as VSATs, limit bandwidth, leading to degraded signal fidelity and poorer performance in signal transmission.
Innovation Solution
A compensation filter is implemented in the signal path of the transmitting device, programmed with coefficients and parameters to expand the bandwidth, pre-distorting the signal to counteract the lowpass filtering effect of the phase locked loop, resulting in a Butterworth filter response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase locked loop is used in the transmitting device, then the signal fidelity is improved, but the bandwidth is reduced
Solution Approach 1:
The compensation filter is placed before the phase locked loop in the signal path to pre-distort the signal in advance. This preliminary action counteracts the bandwidth-limiting effect of the PLL, allowing the signal to pass through with expanded bandwidth while maintaining fidelity.
Solution Approach 2:
The compensation filter applies an opposing effect to the PLL's bandwidth limitation by introducing a pre-distortion that counteracts the lowpass filtering effect. This preliminary anti-action neutralizes the harmful bandwidth reduction before it occurs.
2Reliability
If the bandwidth of the phase locked loop is reduced, then the signal fidelity is improved, but the overall performance of the transmitting device deteriorates
Solution Approach 1:
By placing the compensation filter before the PLL and programming it with appropriate coefficients, the system pre-processes the signal to compensate for the upcoming bandwidth limitation. This allows the device to achieve both high fidelity and high performance simultaneously.
Data Source
AI summary
An apparatus for PLL bandwidth expansion including a compensation filter and a phase locked loop, where the compensation filter is programmed with a compensation function derived based on programmable coefficients and parameters of a transmitting device, a frequency response of the phase locked loop, and a wanted frequency response.