5:15 PM - 6:45 PM
[PEM16-P02] Development of the analog signal combination system for next-generation solar wind observation system
Keywords:solar wind, ground-based radio observation, phased-array antenna, analog signal combination
Source region and the acceleration mechanisms of the solar wind have not yet been understood well and are actively studied. The interplanetary scintillation (IPS) is observed when the radio wave from distant objects is scattered by the solar wind passing through the front. We have observed the IPS at 327 MHz using our own radio telescopes. We are now developing the next-generation solar wind observation system to observe approximately 10 times as many observational objects as the former telescopes with higher accuracy for further detailed analysis of the solar wind. In the next-generation observation system, 2D phased array antenna consisting of many antenna elements are installed, and a digital multi-beam former is mounted on the back end. This system enables to observe many radio sources accurately and simultaneously.
In this study, we developed an analog signal combination system of the next-generation observation system. This system combines the 16 analog signals received by the 16 antenna elements to form a sub-array. The combination system minimizes power loss of the signal from each antenna to achieve high gain performance of the sub-array. A numerical target is that the power loss of the signal in the analog signal combination device is less than 0.5 dB in the frequency band of 327 MHz.
We made a prototype of 16-port signal combiner. It combines the 16 signals from each of the antenna elements all at once. For the evaluation of this combiner, we used an antenna array system that consists of the 8×2 elements. The spacing between each element is 0.5 m. The transmitter antenna is located 25 m away from the receiver array. The phase difference between the center element and the furthest element is 1/20 of the 327 MHz wavelength (about 0.917 m) in this array configuration. Then we investigated the output power of the combiner.
The output power is approximately 13 dB less than the total of the 16 input powers. We had expected that the signal loss should be approximately 5 dB based on the results of the pre-experiment. However, this result got a much larger loss compared with the expectation. We also measured the spectrum of the signals received from each element. We found that the change of the power spectra derived from each antenna from the array center to both ends of the array was not symmetric. It is suggested that the radio reflection and interference from the surrounding environment can affect the combiner output. For a more accurate evaluation of the signal combination system, it is necessary to do the same experiment in a larger site where the far-field conditions of the antenna can be met with less artificial objects.
In this study, we developed an analog signal combination system of the next-generation observation system. This system combines the 16 analog signals received by the 16 antenna elements to form a sub-array. The combination system minimizes power loss of the signal from each antenna to achieve high gain performance of the sub-array. A numerical target is that the power loss of the signal in the analog signal combination device is less than 0.5 dB in the frequency band of 327 MHz.
We made a prototype of 16-port signal combiner. It combines the 16 signals from each of the antenna elements all at once. For the evaluation of this combiner, we used an antenna array system that consists of the 8×2 elements. The spacing between each element is 0.5 m. The transmitter antenna is located 25 m away from the receiver array. The phase difference between the center element and the furthest element is 1/20 of the 327 MHz wavelength (about 0.917 m) in this array configuration. Then we investigated the output power of the combiner.
The output power is approximately 13 dB less than the total of the 16 input powers. We had expected that the signal loss should be approximately 5 dB based on the results of the pre-experiment. However, this result got a much larger loss compared with the expectation. We also measured the spectrum of the signals received from each element. We found that the change of the power spectra derived from each antenna from the array center to both ends of the array was not symmetric. It is suggested that the radio reflection and interference from the surrounding environment can affect the combiner output. For a more accurate evaluation of the signal combination system, it is necessary to do the same experiment in a larger site where the far-field conditions of the antenna can be met with less artificial objects.