Carrier Frequency-Independent Receiver Baud Rate Estimation
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Solution Overview
Problem
Existing digital receivers for infrared signals require expensive sampling apparatus to determine carrier frequencies, making them costly for low-cost consumer electronic devices, and existing methods rely on pulse counting which is inefficient.
Innovation Solution
A method to determine the baud rate of an encoded signal by estimating the duration of symbols after demodulation, without counting pulses, using a low-frequency sample clock, allowing for low-cost implementation and accurate decoding of infrared signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sampling of high-frequency IR carrier signals is used to determine carrier frequency, then measurement precision is improved, but device cost increases due to expensive high-speed sampling apparatus
Solution Approach 1:
The patent divides the high-frequency carrier signal analysis into two stages: first, downconvert the high-frequency IR carrier signal to a lower intermediate frequency; second, perform frequency measurement on the downconverted signal. This segmentation allows using lower-cost sampling apparatus while maintaining measurement precision through the two-stage processing approach.
Solution Approach 2:
The patent applies preliminary frequency downconversion before the actual frequency measurement process. By pre-processing the high-frequency carrier signal to a lower frequency range, the system prepares the signal in a form that can be accurately measured by less expensive sampling apparatus, avoiding the need for costly high-speed samplers.
2Device complexity
If pulse counting methods are used to determine carrier frequency, then device cost is reduced, but productivity decreases due to inefficient processing
Solution Approach 1:
The patent replaces the mechanical pulse counting approach with a signal processing-based frequency measurement system. Instead of counting individual pulses through hardware counters, the system uses downconversion followed by frequency estimation algorithms, which are more efficient and less prone to errors while maintaining low device cost.
Solution Approach 2:
The patent introduces an intermediate frequency signal as a mediator between the high-frequency carrier and the final frequency measurement. This intermediate representation allows for more efficient processing compared to direct pulse counting, improving productivity while keeping the overall system cost low.
3Measurement precision
If high sampling frequency is used to capture IR carrier signals, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent segments the frequency measurement process into downconversion and measurement stages, allowing the use of lower sampling frequencies in the second stage. This reduces the energy consumption of the sampling apparatus while maintaining measurement precision through the preparatory downconversion step.
Solution Approach 2:
By performing frequency downconversion as a preliminary action before sampling, the system reduces the required sampling frequency for accurate measurement. This preliminary processing step significantly lowers the energy consumption of the sampling apparatus while preserving the ability to accurately determine the original carrier frequency.
Data Source
AI summary
A method for processing a signal envelope generated by demodulating a received signal that includes a train of pulses that is transmitted at a carrier frequency and is modulated at a given baud rate with data symbols in accordance with a predetermined communication protocol, which defines features of the modulated signal. The method includes measuring a duration of a selected feature in the signal envelope as defined by the communication protocol. The baud rate of the signal is estimated based on the measured duration without counting the pulses in the received signal. The data symbols are decoded by processing the signal envelope responsively to the estimated baud rate.