5:15 PM - 7:15 PM
[PCG20-P13] Development of a Preamplifier on the Basis of Floating Power Supply Dedicated to Electric Field Measurements in Space Plasma
In the observation of electric fields in space plasma, impedance of electric field sensors strongly depends on plasma parameters because the plasma is a dispersive medium. Since electric field sensors need to cover a wide frequency range from DC to 10MHz, the impedance matching between the sensor and the preamplifier is impossible. An extremely high input impedance, therefore, is required for the preamplifier to improve observation accuracy. In addition, the electric field sensor also shows complexed features in the measurement of DC electric fields, because the measurement is affected by electrostatic potentials of sensors as well as spacecraft charging.
To meet the requirements for the preamplifier, the Japanese past design for the preamplifiers on the satellites had two parallel preamplifiers, each dedicated to DC or AC measurement. However, this structure leads to an impedance drop by the interaction of the input impedance of two amplifiers, which declines sensitivity, especially in DC measurements.
On the other hand, European and U.S. missions have used floating power supply preamplifiers that automatically follow the input voltage by supplying power to the preamplifier at a potential independent from the satellite using an isolated DC/DC converter, and by using the potential reference as the output of the preamplifier. This method does not cause impedance drop because it has only one preamplifier and can be expected to provide high-precision observations.
In this study, we proposed a floating power supply preamplifier using a bootstrapping power supply consisting of transistors instead of isolated DC/DC converters, which are used in a conventional floating power preamplifier. This is intended to operate in the same way as a European or U.S. floating power supply preamplifier by generating a constant current from the satellite's internal high-voltage power supply to generate a floating potential independent of the satellite's potential and using the preamplifier's output as the reference of the floating potential. This device does not need a DC/DC converter in the floating power supply, thereby eliminating the effect of switching noise on the observation results, which was a problem with the European and American types. Moreover, since the floating power supply system uses only one preamplifier, it can prevent sensitivity degradation in DC measurements, which was a problem with conventional Japanese satellites. In this presentation, we will show the outline and details of the new preamplifier under development, as well as the results of the performance evaluation of the test circuit.
To meet the requirements for the preamplifier, the Japanese past design for the preamplifiers on the satellites had two parallel preamplifiers, each dedicated to DC or AC measurement. However, this structure leads to an impedance drop by the interaction of the input impedance of two amplifiers, which declines sensitivity, especially in DC measurements.
On the other hand, European and U.S. missions have used floating power supply preamplifiers that automatically follow the input voltage by supplying power to the preamplifier at a potential independent from the satellite using an isolated DC/DC converter, and by using the potential reference as the output of the preamplifier. This method does not cause impedance drop because it has only one preamplifier and can be expected to provide high-precision observations.
In this study, we proposed a floating power supply preamplifier using a bootstrapping power supply consisting of transistors instead of isolated DC/DC converters, which are used in a conventional floating power preamplifier. This is intended to operate in the same way as a European or U.S. floating power supply preamplifier by generating a constant current from the satellite's internal high-voltage power supply to generate a floating potential independent of the satellite's potential and using the preamplifier's output as the reference of the floating potential. This device does not need a DC/DC converter in the floating power supply, thereby eliminating the effect of switching noise on the observation results, which was a problem with the European and American types. Moreover, since the floating power supply system uses only one preamplifier, it can prevent sensitivity degradation in DC measurements, which was a problem with conventional Japanese satellites. In this presentation, we will show the outline and details of the new preamplifier under development, as well as the results of the performance evaluation of the test circuit.