10:45 AM - 12:15 PM
[PEM12-P26] Development and deployment of new HF Doppler observation system with ranging capability
Keywords:HF Doppler, observation system , FM-CW, radar altimeter
The HF Doppler (HFD) ionospheric observation system by the University of Electro-Communications (UEC) has been in operation since 2001 (Tomizawa et al., 2003). We continuously observe conditions in the mid-latitude ionospheric E and F regions over Japan. It features multi-point bistatic observations and provides multi-frequency HFD data at multiple locations (http://gwave.cei.uec.ac.jp/~hfd). The Doppler shift data represent the temporal variation of the phase path length of the reflected wave, which often corresponds to the vertical motion of the ionosphere, and has been used to study propagating ionospheric disturbances, sporadic E phenomena, and variations of the ionosphere associated with energy inputs from the magnetosphere or lower atmosphere.
The radio waves transmitted from the UEC have two frequencies: 5.006 MHz and 8.006 MHz, 200 W each. In the poster presentation at the JpGU in 2022, we introduced the concept of the additional ranging function based on the FM-CW method to the existing system. Then, we got permission to change the current license for the radio transmission and have been conducting development with test measurements. This presentation will report on the status of the subsequent development.
In order to operate the new transmitter system with ranging capability, the control of the transmitter is required a more complicated function than the existing system for only continuous wave transmission. In order to satisfy the following three requirements: (1) consistency with the conventional observation data, (2) capability to measure the reflection altitude, which was previously only inferred from the Doppler shift data, and (3) domestic radio regulations. The new transmitter system uses digital equipment to incorporate a reference signal from GPS, new clock control, and a monitoring system. The conventional transmitter stabilized the transmitting frequency based on a rubidium reference signal, but the new system incorporated GPS-based reference. We confirmed no effect on the observation data. In addition, a function generator with two channels was employed as the source of the transmission signal instead of the conventional transceiver. It can transmit multiple signals: the same continuous wave for Doppler observation, frequency-modulated continuous wave (FM-CW) for distance measurement signals, and Morse code for identification. The use of new devices enables both data continuity and function scalability. The new system is prepared to automatically switch the transmission signal and measure VSWR using a single-board computer or microcontroller to keep the signal quality.
In the presentation, detail of the new system will be introduced based on the measurement data obtained at the inspection of the license change. The presentation will also show the study of a receiver system for FM-CW radio signals.
The radio waves transmitted from the UEC have two frequencies: 5.006 MHz and 8.006 MHz, 200 W each. In the poster presentation at the JpGU in 2022, we introduced the concept of the additional ranging function based on the FM-CW method to the existing system. Then, we got permission to change the current license for the radio transmission and have been conducting development with test measurements. This presentation will report on the status of the subsequent development.
In order to operate the new transmitter system with ranging capability, the control of the transmitter is required a more complicated function than the existing system for only continuous wave transmission. In order to satisfy the following three requirements: (1) consistency with the conventional observation data, (2) capability to measure the reflection altitude, which was previously only inferred from the Doppler shift data, and (3) domestic radio regulations. The new transmitter system uses digital equipment to incorporate a reference signal from GPS, new clock control, and a monitoring system. The conventional transmitter stabilized the transmitting frequency based on a rubidium reference signal, but the new system incorporated GPS-based reference. We confirmed no effect on the observation data. In addition, a function generator with two channels was employed as the source of the transmission signal instead of the conventional transceiver. It can transmit multiple signals: the same continuous wave for Doppler observation, frequency-modulated continuous wave (FM-CW) for distance measurement signals, and Morse code for identification. The use of new devices enables both data continuity and function scalability. The new system is prepared to automatically switch the transmission signal and measure VSWR using a single-board computer or microcontroller to keep the signal quality.
In the presentation, detail of the new system will be introduced based on the measurement data obtained at the inspection of the license change. The presentation will also show the study of a receiver system for FM-CW radio signals.