Frequency Drift Compensation in Bidirectional Metering Communication
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Solution Overview
Problem
Existing bidirectional communication systems between measuring devices and data collectors face challenges in maintaining effective downlink transmission of control telegrams due to limited resources and frequency drift issues, particularly in measuring devices that rely on batteries and have limited circuit technology.
Innovation Solution
The solution involves equipping the data collector's recipient and transmitter with an oscillator, while each measuring device uses a common oscillator for its transceiver. By performing frequency difference measurements, the data collector adjusts the transmission reference frequency to match the measuring device's receiver frequency, ensuring optimal demodulation conditions for control telegrams without additional circuitry in the measuring device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the measuring device uses a common oscillator for both transmission and reception, then the device complexity is reduced, but frequency drift causes deterioration in the reliability of downlink communication
Solution Approach 1:
The patent implements a feedback mechanism where the measuring device determines the frequency difference between its transmitted signal and received signal, then uses this information to adjust its oscillator frequency. This closed-loop feedback system automatically compensates for frequency drift caused by temperature changes and aging, maintaining reliable bidirectional communication without requiring complex separate oscillators for transmission and reception.
2Use of energy by moving object
If the data collector transmits control telegrams using narrowband transmission, then the energy consumption is reduced, but frequency drift makes demodulation difficult without additional circuitry in the measuring device
Solution Approach 1:
The measuring device uses feedback to determine the frequency offset between transmitted and received signals, then adjusts its oscillator accordingly. This allows the device to maintain accurate frequency alignment for narrowband downlink reception without requiring additional demodulation circuitry, keeping both energy consumption and circuit complexity low.
Solution Approach 2:
The measuring device performs self-adjustment of its oscillator frequency based on the frequency difference it determines between its own transmitted signal and the received control telegrams. This self-service mechanism eliminates the need for external frequency correction or additional complex circuitry in the resource-constrained measuring device.
3Adaptability or versatility
If the measuring device operates autonomously on batteries with limited resources, then the portability and independence are improved, but the capability for interference-free narrowband downlink reception deteriorates
Solution Approach 1:
The autonomous measuring device incorporates a feedback mechanism that continuously monitors frequency drift and automatically adjusts its oscillator frequency. This allows the resource-constrained battery-powered device to maintain reliable narrowband downlink reception despite environmental variations, without requiring additional power-consuming circuitry or external assistance.
Solution Approach 2:
The measuring device dynamically changes its oscillator frequency parameter based on the detected frequency difference, adapting to environmental conditions such as temperature changes and aging effects. This parameter adjustment enables the device to maintain optimal reception conditions for narrowband control telegrams while operating autonomously with limited resources.
Data Source
AI summary
The aim of the invention is to achieve optimal receipt of the smart meter control telegrams (15) transmitted by a concentrator (data collector 12) in the case of a measuring device (11) having a transceiver (13) for bidirectional data exchange despite the minimal resources of said measuring device. This aim is achieved in that the current modulation reference frequency (f17) in the data collector (12), which modulation reference frequency is subject to drift, is shifted by the instantaneous frequency difference (Δf) between the current transmitter-side reference frequency (f17) and the current transceiver-side reference frequency (f13). Thus, the current reference frequencies (f17 = f13) match in the case of the downlink without intervention in the measuring device (11) being required. Said frequency difference (Δf) in the data collector (12) is obtained from a comparison of the current receiver-side demodulation reference frequency (f16) with the current transmitter-side reference frequency (f17) and with the current transceiver-side reference frequency (f13) from telegrams (14, 21) from the transmitter (17) of the data collector (12) and from the transceiver (13) of the measuring device (11), which are received by means of the receiver (16) of the data collector (12). Without demand for the resources of the measuring device (11), all that is required therefor is merely the connection of a frequency-measuring comparator (20) before and after the demodulator (24) in the data collector (12), followed by a frequency subtractor (22) connected to the transmitter-side conditioner (19.17) in order to derive the reference frequency (f) from an oscillator frequency (F).