Presentation Information
[ED6-06]Theoretical Analysis of Voltage Waveforms Reconstructed from Frequency-Modulated Pulse Trains for AC Josephson Voltage Standard
*Kaho Koyanagi1, Michitaka Maruyama1, Hirotake Yamamori1, Daiki Matsumaru1, Nobu-Hisa Kaneko1 (1. AIST (Japan))
Keywords:
Josephson Voltage Standard,AC Voltage,Electrical Measurements,Frequency Modulation,Waveform
[Purpose]
To ensure metrological traceability in miniaturized electronic devices such as IoT sensors operating at low voltages, we aim to develop quantum voltage sources and establish calibration techniques for small voltage ranges. This study focuses on analyzing the RMS voltage error of AC waveforms reconstructed from modulated pulse trains, which is essential for validating the accuracy of our unique waveform generation method using frequency modulation (FM-JVS) for small-amplitude quantum AC voltage waveforms.
[Method]
In the FM-JVS system, a frequency-modulated microwave centered around the characteristic frequency (approximately 12 GHz) is applied to Josephson junction array A, while another microwave at the characteristic frequency is applied to an array B, which are connected in series. The differential voltage between arrays A and B generates a quantum AC voltage waveform synchronized with the modulation signal, without any DC offset component. Additionally, by using a mixer circuit and a pulse counter to measure the difference frequency component between the microwaves, a theoretical AC waveform can be computationally reconstructed and compared with the generated quantum waveform. This reconstruction method involves counting the number of pulses (Npulse) within a fixed time window (Twindow), and repeating this process over time to obtain the instantaneous frequency modulation degree (Npulse / Twindow). Since the output voltage of a Josephson junction is proportional to the applied microwave frequency, a series of instantaneous voltage values can be derived from the frequency data, enabling reconstruction of the theoretical AC waveform and its RMS value.
[Results]
RMS voltage values reconstructed from experimentally measured pulse trains were compared with those calculated from ideal pulse trains. The FM frequency was 10 Hz, and the modulation depth was ±141 MHz, corresponding to 1.14% of the 12 GHz carrier frequency. The deviation ratio of the RMS voltage from the theoretical value was found to depend on the inverse of the time window (fwindow = 1/Twindow), confirming that the choice of Twindow significantly affects measurement accuracy.
[Consideration]
Experimental results demonstrated that accurate evaluation of RMS voltage requires careful selection of the time window Twindow. In particular, the influence of the time window length on RMS deviation was clearly observed. The comparison between measured and ideal pulse trains enabled quantitative validation of the waveform reconstruction accuracy. These findings suggest that Twindow is a critical parameter directly linked to measurement precision in FM-JVS-based AC voltage reconstruction.
[Conclusion]
This study confirms that the selection of the time window used for pulse counting is crucial for accurate RMS voltage evaluation in FM-JVS systems. The proposed method enables precise measurement of quantum-level AC voltages, contributing to the advancement of quantum voltage standards for low-voltage electronic devices.
To ensure metrological traceability in miniaturized electronic devices such as IoT sensors operating at low voltages, we aim to develop quantum voltage sources and establish calibration techniques for small voltage ranges. This study focuses on analyzing the RMS voltage error of AC waveforms reconstructed from modulated pulse trains, which is essential for validating the accuracy of our unique waveform generation method using frequency modulation (FM-JVS) for small-amplitude quantum AC voltage waveforms.
[Method]
In the FM-JVS system, a frequency-modulated microwave centered around the characteristic frequency (approximately 12 GHz) is applied to Josephson junction array A, while another microwave at the characteristic frequency is applied to an array B, which are connected in series. The differential voltage between arrays A and B generates a quantum AC voltage waveform synchronized with the modulation signal, without any DC offset component. Additionally, by using a mixer circuit and a pulse counter to measure the difference frequency component between the microwaves, a theoretical AC waveform can be computationally reconstructed and compared with the generated quantum waveform. This reconstruction method involves counting the number of pulses (Npulse) within a fixed time window (Twindow), and repeating this process over time to obtain the instantaneous frequency modulation degree (Npulse / Twindow). Since the output voltage of a Josephson junction is proportional to the applied microwave frequency, a series of instantaneous voltage values can be derived from the frequency data, enabling reconstruction of the theoretical AC waveform and its RMS value.
[Results]
RMS voltage values reconstructed from experimentally measured pulse trains were compared with those calculated from ideal pulse trains. The FM frequency was 10 Hz, and the modulation depth was ±141 MHz, corresponding to 1.14% of the 12 GHz carrier frequency. The deviation ratio of the RMS voltage from the theoretical value was found to depend on the inverse of the time window (fwindow = 1/Twindow), confirming that the choice of Twindow significantly affects measurement accuracy.
[Consideration]
Experimental results demonstrated that accurate evaluation of RMS voltage requires careful selection of the time window Twindow. In particular, the influence of the time window length on RMS deviation was clearly observed. The comparison between measured and ideal pulse trains enabled quantitative validation of the waveform reconstruction accuracy. These findings suggest that Twindow is a critical parameter directly linked to measurement precision in FM-JVS-based AC voltage reconstruction.
[Conclusion]
This study confirms that the selection of the time window used for pulse counting is crucial for accurate RMS voltage evaluation in FM-JVS systems. The proposed method enables precise measurement of quantum-level AC voltages, contributing to the advancement of quantum voltage standards for low-voltage electronic devices.