Design of an Automatic Test System for Terminal Guidance Radar

Terminal guidance radar is one of the key components of the anti-ship missile guidance system. The quality of its performance directly affects the tactical and technical indicators of the missile. It is technically complex, has the highest failure rate, and has a heavy maintenance and support task. At present, the missile terminal guidance radar test equipment is basically a special supporting equipment corresponding to each type of terminal guidance radar. They are not universal, and the test methods and means are different, which brings serious difficulties to the military's use, maintenance and repair, and reduces the technical support efficiency of the missile. In response to the urgent need for universal and automated terminal guidance radar test equipment and the "universalization, serialization, and modularization" requirements of equipment development, modern measurement and control technology is used to develop a universal detection system for terminal guidance radar. The test software, adapter, target simulator and the object to be tested correspond to each other, and the effectiveness of the automatic test equipment can be maximized without moving the general equipment resources. It is of great practical significance and long-term strategic significance to realize the universalization of terminal guidance radar, save financial investment, improve the reliability of the measurement and control system, and thus improve the technical support level and support efficiency of the military.

1 Interface bus

1.1 GPIB bus

GPIB, also known as IEEE488 or HP-IB, was first proposed by HP. In order to effectively transmit information, the GPIB system requires three different elements: listener, speaker and controller. Its data transmission adopts bit parallel, byte serial, bidirectional hook and bidirectional asynchronous methods. There are 24 buses in total, which can be divided into three categories: 16 signal lines, 1 shield line and 7 ground lines. The signal lines are divided into three groups: the first group is the 8-bit data bus, which is used to transmit data, commands or status words; the second group is the interface management bus, which consists of 5 signal lines (ATN, IFC, REN, SRQ, EOI), which is used to control the bus process and play a bus command role; the third group is three hook lines (DAV, N RF D, N DAC ), which are used for data communication and ensure the smooth progress of asynchronous transmission. It supports ten basic interface functions, including controller, speaker, extended speaker, listener, extended listener, source hook, receiver hook, service request, remote local, parallel query, device trigger and device clear function.

1.2 RS-422 interface protocol

The full name of RS-422 standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuit". Because the receiver uses high input impedance and the transmission driver has stronger driving capability than RS232, it allows multiple receiving nodes to be connected on the same transmission line, up to 10 nodes. That is, one master device (Master) and the rest are slave devices (salve). The slave devices cannot communicate with each other, so RS-422 supports point-to-multiple bidirectional communication. The input impedance of the receiver is 4 k, so the maximum load capacity of the transmitting end is 10×4 k+100 Ω (termination resistance). The maximum transmission distance of RS-422 is 4,000 feet (about 1,219 meters) and the maximum transmission rate is 10 Mb/s. The length of its balanced twisted pair is inversely proportional to the transmission rate. The maximum transmission distance can only be achieved at a rate below 100 kb/s. The highest transmission rate can only be obtained at a very short distance. Generally, the maximum transmission rate that can be obtained on a 100-meter twisted pair is only 1 Mb/s.

2 Overall design

2.1 System composition

The terminal guidance radar universal detection system is an integrated, digital, universal bus-based automatic detection system, which consists of a hardware platform, a software platform, and a test program set TPS (including test program TP and interface adapter TUA), as shown in Figure 1.

The system adopts the IEEE488 bus mode. The measurement and control computer is the control center of the system. It connects all test resources through the IEEE488 bus cable, controls the test resources through the test software, and realizes the automatic test and automatic diagnosis process of the radar. There are two types of test resources: general test resources and special test resources. General test resources are general shelf products, such as signal sources, oscilloscopes, etc., generally using IEEE488 bus products; special resources are self-developed special equipment that cannot be bought on the market, such as adapters, target simulators and controllers, microwave darkrooms, etc. Try to use IEEFA88 bus devices for program-controlled equipment.

The system mainly consists of a measurement and control computer, a test platform, a power supply system and a target simulator. The measurement and control computer consists of a computer host and peripherals such as a display , keyboard, mouse, printer, etc. The power supply system uses ~220 V, 50 Hz power supply to output DC 28.5 V; the test platform includes a computer host containing a GPIB bus control card, a 422 bus communication card, an adapter, a data acquisition card, an oscilloscope, a multimeter and a signal source; the target sensor includes a cross and a target simulator.

2.2 Basic design principles

(1) Achieve the requirements of "standardization, generalization, and serialization" to meet the needs of future development;

(2) The test process meets the needs of the repair shop for factory maintenance of the two types of terminal guidance radars and cannot copy the test process of the technical preparation position;

(3) Use mature technologies and general equipment to the maximum extent possible to ensure system reliability and maintainability;

(4) Combining the universalization and miniaturization of system equipment, striving for miniaturization;

(5) The motorized portable box structure is adopted to meet the requirements of transfer use;

(6) The equipment is easy to operate and has a good human-machine interface, making it easy to use.

3 Hardware Design

3.1 Connection method selection

Adapter connection mode: For detection systems with many types of test resources and a large number and types of test signals, you can choose to connect the test resources to the object under test through a test adapter. The test adapter plays a role in signal combing, aggregation and simple processing. The signals of the test interface of the object under test are aggregated, classified and simply processed inside the adapter, and then sent to the corresponding test resources. Compared with the direct connection mode, the connection relationship is simple. The connection relationship between the test adapter and the test resources is fixed. When using it, you only need to select the test adapter according to the object under test, and connect the test adapter to the object under test to achieve the connection between the object under test and the test resources. The adapter connection mode is suitable for medium-sized detection systems and situations with fewer objects under test.

3.2 Hardware Platform

3.2.1 Hardware platform composition

The hardware platform consists of a measurement and control computer, a power supply control system, test resources, a test adapter, and some auxiliary equipment, as shown in Figure 3.

3.2.2 System Digital Bus

The GHB bus is used inside the detection system. The GPIB bus complies with the requirements of IEEE488.2-1992 and is used for bus control between the main control computer and the test resources in the system. There is also an RS-422 interface protocol for bus communication between the detection system and the radar under test. The measurement and control computer has a built-in high-performance GIPB card, which leads to the GPIB bus port and directly controls the GPIB test resources.

3.2.3 Measurement and Control Computer (TCC)

The measurement and control computer consists of a computer host and peripheral devices such as a monitor , keyboard, mouse, printer, etc. The computer host contains a GPIB bus control card, a 422 bus communication card, etc. The computer host has a built-in physical backup hard disk, which is different from a general logical hard disk. It is pre-installed with an operating system and test software. When a problem occurs in the system disk, the backup hard disk can be converted into a system disk. The measurement and control computer is the test control center of the detection system, and its main functions are as follows:

(1) Provide GPIB bus interface communication;

(2) Computer resource management;

(3) Management of test resources;

(4) Scheduling and management of the test program (TPS);

(5) Test data recording, storage, and printout.

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3.2.4 Principles for selecting test resources

(1) The program control interface should be a GPIB bus interface;

(2) Control commands should comply with IEEE488.2 standards;

(3) The test accuracy meets the test requirements of terminal guided mines ;

(4) Meet the requirements for seeker testing and determine the model and quantity based on comprehensive considerations.

3.2.5 Test equipment

Testing resources mainly consist of two types of equipment: general testing equipment and special testing equipment.

General test equipment: refers to the shelf products available in the market, mainly GPIB bus products. The structure of general test equipment should comply with the GJB100-86 "Basic Dimension Series of Racks and Cabinets" standard, and the reliability index should meet the system requirements.

Special test equipment: Special test equipment refers to equipment that is specifically used for measuring, simulating , and controlling certain specific parameters. It is professional equipment, a non-shelf product, and must be developed in conjunction with other equipment.

In addition to the above-mentioned bus-type equipment, the test resource composition also includes non-programmable equipment such as microwave darkroom, horn antenna, target simulator, microwave cable, etc.

3.3 Test Interface Adapter (TUA)

The full name of the test interface adapter is Test Unit Adapter (TUA).

3.3.1 Adapter Function

The adapter is a device that provides electronic, electrical and mechanical connections between the object under test and the test resources. It can include appropriate excitation and load that are not available in the test resources. Considering the cost factor, the detection system does not use the array interface form, but the test resources are directly connected to the test object through the adapter. In addition to providing a connection channel, the test adapter also completes the following functions:

(1) The TTL level output signal of the detection system directly drives the relay array inside the adapter, issuing control instructions in the form of 28.5 v/air, ground/air, 28.5 v/ground, etc.

(2) The 28.5 V/air, ground/air and other status commands sent by the terminal guidance radar under test are converted into TTL level form inside the adapter and detected by the digital I/O in the detection system;

(3) The multi-channel DC power supply voltage signals and analog quantity signals output by the terminal guidance radar under test are selected through the switch array inside the adapter and sent to the digital voltmeter for measurement;

(4) Achieve the training of the terminal guidance radar under test;

(5) Sort and classify the tested signals and send them to the corresponding test resources;

(6) Perform level conversion on the synchronous pulse video signal output by the terminal guidance radar under test, and convert it into the level form required for the pulse triggering of the oscilloscope and microwave signal source.

3.3.2 Adapter structure

The front panel of the adapter is equipped with radar status display lights, key signal monitoring points, radar experience control, etc. The rear panel is the connection port with the radar under test and test resources; considering the line loss factor, the test signal and video signal are transferred through the adapter, and the microwave signal is not transferred through the adapter, but directly connected from the RF output port of the radar comprehensive tester to the target simulator, and from the radar directly to the RF input port of the radar comprehensive tester. The test adapter adopts a 19-inch standard chassis with a height of 4U. The rear panel is connected to the test resources of the detection system through a connector. The front panel includes: Key signal monitoring points: The front panel of the adapter is designed with key signal monitoring points, which are directly connected to the signal of the radar detection interface without any processing and transfer, and are used to directly detect the working status and control status of the radar on the ground.

4 Software Design

The system selects WINXP as the operating system; selects Lab-Windows/CVI and VC++ as the main control program and detection program development tools to complete the test of the radar performance indicators under test.

Radar console soft panel: provides manual operation of the radar, adjusts and queries general radar parameters, and the radar status indicator shows the current working status of the radar.

Instrument control soft panel: a virtual interface for controlling test resources such as voltmeter, signal source, oscilloscope, target simulator controller, etc., and controlling related instrument parameters. The radar console soft panel and instrument console manually control the tested object and test resources to complete all manual test items.

Automatic test soft panel: According to the test procedure , the terminal guidance radar is tested in a "full process and full item automatic test" sequence. Before the automatic test, the tester can not only select the number of automatic test items and the test process, but also pause and terminate the test process. This improves the flexibility of the system's automatic test process and facilitates the user's handling of unexpected events.

Data management software panel: complete the processing, analysis, storage, query and printing of test data;

System Help Panel: Complete description of the test system, usage, test steps, troubleshooting of common software failures, etc.

5 Conclusion

This universal automatic test system completes the automatic test tasks of 4 different terminal guidance radars . It has small size, standardized structure, high test accuracy and fast speed. It improves the maintainability and supportability of the radar system, increases the combat readiness rate and mission success rate, and reduces the maintenance and support costs of the system.