PXI-based System Research Articles

Wuhan Ionospheric Oblique-Incidence Sounding System and Its New Application in Localization of Ionospheric Irregularities

In this paper, a novel oblique-incidence ionosonde (Wuhan Ionospheric Oblique-Incidence Sounding System) and its new application in the localization of the ionospheric irregularities are presented. Due to the usage of the binary-phase-coded waveform, a large signal processing gain, a high Doppler and range resolution, and a large unambiguous detection range can be achieved in this ionosonde. This ionosonde also adopts the peripheral component interconnect extensions for instruments (PXI) bus technology and is designed as a small-sized PXI-based system. Furthermore, a high-performance oven-controlled crystal oscillator that is disciplined by the Global Positioning System is used to achieve a good time and frequency synchronization. With multichannel digital receiver and multiple receiving sites, this ionosonde can be applied in the localization of the ionospheric irregularities. The details of the system configuration, the ambiguity function of the sounding waveforms, the signal processing algorithm, and the time and frequency synchronization method are described. The experimental results show that the virtual height along with the ground position of the ionospheric field-aligned irregularities can be preliminarily localized with this ionosonde.

A Low-Power and Small-Size HF Backscatter Radar for Ionospheric Sensing

A new high-frequency backscatter radar (Wuhan Ionospheric Oblique Backscattering Sounding System) for ionospheric sensing and study has been developed. With the new system design, oblique backscatter sounding and oblique sounding can be achieved in this radar just through simply loading appropriate software. Furthermore, due to alternate transmission and reception in equal interval, this radar can detect the ionospheric state in the range of a few thousand kilometers and achieve the largest gain of applied pseudorandom sequences. In addition, this radar usually obtains 27-dB gain from phase coded pulse compression and 21-dB gain from coherent spectral integration using pseudorandom code, pulse compression, and coherent spectral integration techniques. This radar also exploits merits of Peripheral component interconnect eXtensions for Instruments (PXI) bus technology and is designed as a modular and compact PXI-based system. Details of system design, sounding timing, and signal-processing algorithm are described. Except for the antenna systems and power amplifier, this radar's dimension is 177.8 times 431.8 times 457.2 mm. With this radar, the oblique backscatter ionogram and Dopplerionogram can be clearly obtained in the range of a few thousand kilometers with 100-W power. The oblique ionogram for propagation over a distance of several kilometers can also be clearly acquired at the time of oblique backscatter sounding. The initial observations obtained with this radar are included to demonstrate its performance.

Loss-less data acquisition system for SST-1

SST-1 being steady-state Tokamak having a discharge duration of 1000 s demands a data acquisition system (DAS) which is capable enough to acquire data loss lessly from slow diagnostics. The needs of loss-less continuous acquisition have a significant effect on selection of acquisition hardware. The evolution of DAS for steady-state operation of Tokamaks has been technology-driven. The paper describes the various needs of SST diagnostics and our selection of the most suitable configuration for long-duration discharges. Here PXI bus, which is an extension of the widely accepted PCI bus, has been evaluated on the most commonly used platform like Windows with normally available PCs. For slow diagnostics, the PXI-based system with 48 channels was evaluated for continuous, single-shot and windowed acquisition. In the case of continuous acquisition, it acquires data from 48 channels at 10 kHz sampling rate and pushes all the 48 data channels on the network as well as writing to the hard disk simultaneously. A client utility also has been developed to view the data from any network node.