Research on Satellite Interference Monitoring Technology Based on LabVIEW

0Introduction

Satellite applications have provided all-weather, all-day, high-precision positioning and monitoring services for various military and civilian carriers on land, sea and air in my country, and have become increasingly important in national defense construction and the national economy. However, satellites are extremely susceptible to interference. When high-power interference or matching interference enters the station, the normal inbound signal level will drop or even be interrupted, and user information will not be able to enter the station, which seriously affects the stable operation of the system.

In order to ensure the normal operation of satellites, it is necessary to monitor interference. At present, my country can locate certain interference within a certain accuracy using the amplitude difference method. Based on the above requirements, this system uses LabVIEW to develop a system that automatically monitors and stores excessive interference signals and extracts the carrier-to-noise ratio and important signal parameters.

The stored data can be reproduced, its source, type and impact on the system can be analyzed, certain interference can be located, and the impact of interference on the system can be eliminated.

1. System Requirements

The spectra of the six inbound beams are acquired in real time and displayed on a monitoring computer.

There is often interference when the system enters the station. When the interference is large enough, it will suppress the inbound signal, resulting in a low success rate of inbound capture or even the inability of users to enter the station. A trigger should be set within the system anti-interference threshold. Once it exceeds the threshold, an audible and visual alarm will be sounded, and users can extract the G/T value in time for positioning.

The inbound signal power of a satellite may decrease or even become zero due to factors such as weather or the unstable working state of the satellite itself. This phenomenon can be monitored through the inbound signal power and an alarm can be issued in time.

When interference occurs, the interference waveform data and important parameters are stored in a timely manner for later reproduction and research.

2 System Design and Implementation

This system uses Advantech's industrial computer to control the spectrum analyzer through the GPIB card to monitor the satellite inbound signal. The system structure is shown in Figure 1. It mainly consists of a spectrum analyzer, an on-site industrial computer, a GPIB card, a switch, and a monitoring computer.

The on-site industrial computer establishes a connection with the spectrum analyzer through the GPIB card, and issues control commands to the spectrum analyzer through the GPIB port, including: center frequency, bandwidth, analysis bandwidth, video bandwidth, reference level, peak search, etc. For the data obtained from the spectrum analyzer, the "DataSocket Server" data transmission protocol program is written on the industrial computer, and sent to the monitoring computer located in the signal transceiver room through the network connection line arranged in the computer room. After receiving the network data, the monitoring computer restores the spectrum data and image in the monitoring window, and sets the interference threshold. When the inbound interference triggers the sound and light alarm, the system automatically stores the interference signal.

Figure 1 System structure

2.1 On-site industrial computer software module

The industrial computer in the transmitter room uses the following modules to control the spectrum analyzer and extract data:

1) Driver module.

The main driver module used in industrial computers is shown in Figure 2.

Figure 2 Driver module

The five drive modules in Figure 2 are control modules, from left to right:

a) Initialize VI initialization module: used to establish communication with the spectrum analyzer and generate a visa vision identification word, using a fixed GPIB address to represent the instrument; b) Frequenc VI frequency control module: use this module to set the center frequency of the spectrum analyzer; c) Span VI bandwidth control module: use this module to set the bandwidth of the spectrum analyzer; d) Amplit VI level control module: use this module to set the reference level of the spectrum analyzer; e) Marker VI: use this module to control the display of peak point data.

2) Reading module. The data reading module is shown in Figure 3.

Figure 3 Reading module

The four drive modules in Figure 3 are read modules, from left to right:

a) Trace VI trace reading module: use this module to restore the spectrum curve; b) Power VI power reading module: use this module to read the signal power; c) Frequenc VI frequency reading module: use this module to read the center frequency of the spectrum analyzer; d) Amplit VI level reading module: use this module to read the peak level of the signal.

2.2 Monitoring computer software

The main process of the monitoring program is as follows: After the spectrum data received by the on-site industrial computer is sent to the computer in the remote control room through the network connection line arranged in the computer room, the spectrum data and image are restored in the monitoring window after the collected data on the network is obtained by using datasocket read.vi, and the spectrum power value is calculated. If it exceeds the set range (the threshold is usually set to 3 dB deviation from the normal inbound power and 10 dB higher than the normal inbound level), an audible and visual alarm will be issued. At the same time, the program also has a save function, which stores the waveform in real time and records important parameter information such as the average power of the alarm information and the time when the carrier peak occurs.

2.2.1 Interference waveform and important parameter storage function

The over-limit trigger alarm function is determined by the output of several comparators. The comparator compares the set carrier/power threshold with the inbound interference power/power sampling value: when the threshold value is not exceeded, the output is false; when the threshold value is exceeded, the output is true, triggering the sound and light alarm and interference storage module, and at the same time storing the important waveform parameters and the time when the interference occurs within the entire inbound bandwidth. This is the most important function of this system, and part of its program is shown in Figure 4.

Figure 4 Interference waveform storage function

2.2.2 Interference recurrence function

When it is necessary to restore or analyze the saved interference waveform, you can reproduce it through the written interference recovery program, set the offset of Read waveformfrom file.vi to screen the interference, check the time when the interference occurs, and display the peak frequency, average power and other parameters of the interference. You can also analyze other parameters of the interference as needed.

2.2.3 Remote Control

Normally, there is no need to locate the interference source, mainly because the spectrum analyzer needs to be set up cyclically to measure the accurate carrier-to-noise ratio. Therefore, the carrier-to-noise ratio is not extracted normally. When the interference source needs to be located, the on-site industrial computer program can be controlled through remote login to start the carrier-to-noise ratio measurement and automatically save the carrier-to-noise ratio on the monitoring computer.

2.3 Key technologies used

The implementation of this system mainly adopts the following key technologies.

2.3.1 DataSocket Technology

DataSocket is a network programming technology based on TCP/IP protocol. It is oriented to measurement and real-time high-speed data exchange on the Internet. It can be used for data exchange within a computer or between multiple applications. Its characteristic is real-time. It adopts the architecture of Publisher, DataSocket. Server and Subscriber. DataSocket eliminates the more complex TCP/IP underlying programming and simplifies the communication between applications and computers. The two parties exchanging data do not need to communicate directly, but read (Read) or write (Write) data to a third-party DataSocket. Server. The data interface of the application becomes very simple and the data type does not need to be converted.

Using this technology, the monitoring computer can access the on-site acquisition card and become a local virtual data acquisition card.

2.3.2 Remote Control

This system integrates remote control technology. The monitoring computer can not only open and operate the VI front panel of the server computer in a very simple way, but also allow users to directly open and operate the test program front panel on the server on the client. It can even embed the test program front panel window into a web page and operate it directly on the web page. In this way, users can directly operate the software on the server through a remote panel link or browser on the client. Figure 5 shows an open virtual instrument panel located at the acquisition site.

Figure 5 The front panel of the remote control program opened in the IE browser

3 Conclusion

The satellite interference monitoring system, which uses spectrum analyzer, switch and industrial computer as hardware platform and is based on datasocket and remote panels technology of LabVIEW, not only realizes the real-time processing or online monitoring of satellite beams, but also has the functions of alarm and post-interference analysis and processing. The system has good scalability, improves our anti-interference measures and improves the reliability of satellite applications to a certain extent.