ASK Demodulation Circuit Using Delayed-Signal Subtraction for NRZ Data
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ASK demodulation devices face challenges in quickly changing threshold values for demodulating ASK-modulated signals with NRZ-encoded data sequences due to continuous input of '0' or '1', leading to slow response and bit errors, especially when signals are distorted, and require complex control circuits for maintaining a 50% duty ratio in Manchester-encoded data.
Innovation Solution
An ASK demodulation device that delays the detected signal by less than one bit time, subtracts it from the original signal, and extracts crossing points within a specific time interval to synchronize the clock signal, eliminating the need for threshold calculation and using a simple configuration to determine polarity and recover the data clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ASK demodulation device uses a long time period for obtaining mean value of the detected signal to ensure accurate threshold calculation, then the threshold value accuracy is improved, but the response speed deteriorates and the device cannot quickly change threshold values when signal levels change
Solution Approach 1:
The patent pre-calculates and stores threshold values for multiple signal levels before actual demodulation occurs. When the signal level changes, the device can immediately switch to the pre-prepared threshold value corresponding to the new level, avoiding the need for long-time mean value calculation and achieving both accuracy and fast response
Solution Approach 2:
The patent implements dynamic threshold selection by detecting signal level changes and automatically switching between different pre-calculated threshold values. This dynamic adaptation allows the device to maintain accurate threshold values for varying signal conditions without requiring continuous long-duration measurements
2Measurement precision
If a conventional ASK demodulation device uses complex control circuits to maintain 50% duty ratio in Manchester-encoded data, then the demodulation accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent utilizes the inherent characteristics of Manchester encoding where level transitions naturally occur at the center of each bit period. By detecting these transitions and using them as clock references, the device can automatically maintain 50% duty ratio without requiring complex external control circuits, achieving both accuracy and simplicity
Data Source
AI summary
A delay section delays a detected signal by less than one bit time in the NRZ data. A subtraction section performs subtraction between a delayed signal and the detected signal, and outputs a resultant signal. A clock extraction section extracts, from crossing points of a subtracted signal, crossing points whose time interval is more than or equal to (Tb-alpha) and less than or equal to (Tb+beta) (wherein 0<alpha<=Tb/8, 0<beta<=Tb: Tb is one bit time in the NRZ data), and outputs a synchronous signal synchronized with the extracted crossing point. A clock recovery section synchronizes a clock signal with the phase of the synchronous signal, and outputs a data clock signal. A determination section determines the polarity of the subtracted signal outputted from the subtraction section in accordance with the data clock signal, and outputs the determination result as the NRZ data.