Shuzhu Shi

The Wuhan Ionospheric Sounding Systems

The ionospheric laboratory of Wuhan University, Wuhan, China, has developed a new ionospheric sounding system for about seven years. The first system is used for ionospheric oblique backscattering detection and is called the Wuhan ionospheric oblique backscattering sounding system (WIOBSS). The WIOBSS is a portable monostatic backscatter ionosonde for ionospheric research and high-frequency (HF) channel management, adopting alternate transmitting and receiving patterns to transmit long coded pulse trains for high pulse-compression gain. However, it is difficult to recognize the echo path and mode only with the backscatter ionogram. Therefore, a separate remote digital receiver has been developed for auxiliary detection. The receiver is a compact radio system used to receive the transmitting signal of the WIOBSS, and it includes a Global Positioning System receiver for clock and frequency standard synchronization. Combined with the WIOBSS, the receiver has been used for ionospheric bistatic backscatter sounding and oblique incident sounding. The WIOBSS and several remote digital receivers can compose a detection network for ionospheric research and HF channel management.

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.

Experimental Demonstration for Ionospheric Sensing and Aircraft Detection With a HF Skywave Multistatic Radar

In this letter, a new high-frequency (HF) skywave multistatic radar that is used for ionospheric sensing and aircraft detection is presented. With multiple receiving sites, this radar can detect the aircraft in much larger surveillance with high probability and can obtain the characteristics of many ionospheric paths simultaneously. In addition, this radar adopts a binary-phase-coded continuous waveform to achieve a high Doppler resolution, a large signal processing gain, and a low probability of interception. Details of the system configuration, the ambiguity function of the sounding waveform, and the signal processing algorithm are described. The experimental results show that backscatter ionograms and oblique ionograms can be simultaneously obtained and that the aircraft with different flying conditions can be clearly detected with an HF skywave multistatic experimental radar.

A Novel Radar Waveform Design for a Low-Power HF Monostatic Radar

In this letter, a novel radar waveform is proposed for a low-power high-frequency monostatic radar used for ionospheric sensing and aircraft detection. In this proposed waveform, a hybrid modulation scheme is adopted, where the pulse-to-pulse phase is coded by the WG sequence, and the frequency of each subpulse is linearly modulated with a fixed chirp rate. Compared with the conventional binary-phase-coded waveform, larger signal processing gain, higher range resolution, and lower range sidelobes can be simultaneously achieved with the proposed waveform. Furthermore, it is more insensitive to the Doppler shifts and is not subject to significant range-Doppler cross coupling. With this newly proposed waveform, the ionospheric backscatter ionogram with clear leading and trailing edges can be obtained in the range of 500-2300 km, and the aircraft target can be also clearly detected.

Design and implementation of hardware architecture in ionospheric oblique backscattering sounding system

The ionospheric oblique backscattering sounding system can not only be used to detect the state of ionosphere and the condition of high frequency channel in real time, but also be used for over-the-horizon sounding. So, it has a very high military and civil value. For the characteristics of ionospheric oblique backscattering sounding, such as long sounding distance, wake echo, strong background noise, slow moving target, etc., a hardware platform of ionospheric oblique backscattering sounding system is designed. This platform adopts the technology of software radio and is designed as a new kind of general-purpose, modularized, software-based ionosonde that is based on VXI (Versa module eurocard eXtensions for Instrumentation) bus. At present, this hardware platform has been successfully used in actual ionospheric oblique backscattering sounding, and the experimental results demonstrate that this system can satisfy the demands of ionospheric oblique backscattering sounding preferably.

Wuhan Ionospheric Oblique Backscattering Sounding System and Its Applications—A Review

For decades, high-frequency (HF) radar has played an important role in sensing the Earth’s environment. Advances in radar technology are providing opportunities to significantly improve the performance of HF radar, and to introduce more applications. This paper presents a low-power, small-size, and multifunctional HF radar developed by the Ionospheric Laboratory of Wuhan University, referred to as the Wuhan Ionospheric Oblique Backscattering Sounding System (WIOBSS). Progress in the development of this radar is described in detail, including the basic principles of operation, the system configuration, the sounding waveforms, and the signal and data processing methods. Furthermore, its various remote sensing applications are briefly reviewed to show the good performance of this radar. Finally, some suggested solutions are given for further improvement of its performance.

A Novel Ionospheric Oblique-Incidence Sounding Network Consisting of the Ionospheric Oblique Backscatter Sounder and the Parasitic Oblique-Incidence Sounder

In this letter, a novel ionospheric oblique-incidence sounding network consisting of the ionospheric oblique backscatter sounder and the parasitic oblique-incidence sounder is presented. With the new configuration, the oblique ionogram and the backscatter ionogram can be provided at the same time. Due to the usage of a novel waveform combining the pseudorandom phase coding and the chirp modulation, about 130-dB signal processing gain can be usually obtained to improve the signal-to-noise ratio for the low-power transmission. Furthermore, through choosing different types of pseudorandom sequences for each transmitter, many oblique ionograms that depict the information of different propagation paths can be simultaneously achieved at a single receiver site. In addition, the digital beamforming technique is implemented on the receiving antenna array to simultaneously receive the echoes produced by each transmitter, to achieve a good space isolation to enhance the echo discrimination, and to suppress the strong interferers appearing in the high-frequency band. Details of the system configuration, the ambiguity function of the sounding waveform, and the signal processing algorithm are described. The initial experimental results show that multiple oblique ionograms can be simultaneously obtained at a single receiver site with this sounding network.

Application of Biphase Complete Complementary Code for Ionospheric Sounding

This paper illustrates the processes carried out for the application of biphase complete complementary code (CCC) for ionospheric sounding to address the coherent interference problem in multi-station ionospheric sounding. An algorithm to generate the biphase CCC is described, and the detailed process of waveform construction and signal processing is presented. Characteristics of the autocorrelation and cross-correlation are analyzed through simulations, and the technical feasibility of the application of CCC is explored. Experiments of ionospheric sounding with the CCC are also implemented to verify performance. Results demonstrate that the CCC performs well in multi-station ionospheric sounding, and is capable of eliminating the coherent interference in the network of ionosondes, compared to the conventional complementary code.

Design of the signal processor for an ionospheric sounding system

On the basis of the analysis of the system sounding principle, this paper introduced a new type of ionospheric oblique backscattering sound system, which is based on the pseudo- random noise phase modulated pulse compression. According to the high requirements of real-time and a large amount of computation and echo characteristics, a high-speed real-time signal processing system was established and the design of system hardware and software was focused on. The sounding results indicate that the system is equipped to handle the data fast and has a high degree of software features. It is of great significance for the realization of fast, real-time ionospheric sounding means.