I. Introduction
With the continuous expansion of higher education and the rising costs of laboratory equipment, many universities are facing a growing shortage of experimental instruments. This challenge has led to an increasing focus on reusing and repurposing old or discarded equipment. Radar transmitters play a crucial role in radar education, but their installation is often limited by factors such as budget and space. Developing a simple and practical experimental radar transmitter can be a cost-effective solution that supports both teaching and research.
In recent years, due to technological upgrades and natural wear and tear, many laboratories have accumulated a large amount of obsolete equipment. Some components within these systems—such as magnetrons, thyratrons, and waveguides—still retain functional value, even if their performance parameters have slightly declined. Instead of discarding them, we have explored the possibility of using these spare parts to build new experimental tools. This initiative not only reduces waste but also provides a solid foundation for hands-on learning.
II. System Design of the Experimental Transmitter
The development of the experimental radar transmitter involved several stages: team selection, schematic design, assembly, and debugging. Based on available spare parts, the system was designed to include key modules such as power supply control, power supply, timer, modulator, magnetron oscillator, and measuring instruments like ammeters and voltmeters. The final layout of the system is shown in Figure 1.
III. Development, Production, and Commissioning
1. Assembly and Testing
Following the schematic, we sourced various components from the existing stock. We first used basic tools like multimeters to test transformers, thyratrons, and magnetrons. After initial screening, we assembled the system on a wooden board. Careful attention was given to electromagnetic compatibility, ensuring proper isolation between RF lines, intermediate frequency lines, and power supplies. After several iterations, the prototype was successfully completed.
2. Prototype Assembly and Performance Evaluation
Once the prototype was built on the wooden board, it was transferred to a standard chassis. Due to spatial constraints and trace layout issues, the debugging process required multiple adjustments. The successful assembly not only deepened students’ understanding of radar transmitter principles but also improved their skills in electronic circuits, RF engineering, and mechanical design. The final prototype is shown in Figure 2.
Microwave systems differ significantly from low-frequency circuits due to their high frequency and short wavelength. This leads to distributed parameters, which affect how signals propagate. As a result, microwave measurements involve parameters like power, wavelength, and standing wave ratio. These aspects were carefully evaluated during testing.
IV. Application in Practical Teaching
When the radar transmitter is used in other experiments, it serves as a self-contained unit that allows students to measure its own performance. This approach not only tests the transmitter’s functionality but also provides a safe environment for hands-on learning. Unlike mounted systems, this independent setup avoids the risks associated with complex waveguide connections, making it more accessible for beginners.
1. Power and Spectrum Measurement
To measure the transmitter's output power, we used a spectrum analyzer with a directional coupler to reduce signal strength. The measured power was xxW, with a spectrum width of xxMHz, as shown in Figure 3.
2. Frequency Measurement
A resonant cavity frequency meter was used to determine the transmitter’s operating frequency. By adjusting the cavity and monitoring the detection current, we could directly read the frequency from the meter. The results are illustrated in Figure 4.
3. Standing Wave Ratio Measurement
Using a standing wave measurement line, we analyzed the electric field distribution in the waveguide. The standing wave ratio (Ï) was calculated based on the maximum and minimum electric field strengths, as shown in Figure 5.
4. RF Signal Transmission and Reception
Finally, the transmitter was connected to horn antennas via waveguide-to-coaxial adapters. The received signal was analyzed using a spectrum analyzer, demonstrating the system’s capability to transmit and receive RF signals, as seen in Figure 6.
V. Innovative Production Experience
By repurposing spare parts from retired equipment, we created a practical teaching tool that is both cost-effective and educational. This approach not only addresses funding constraints but also fosters student innovation and problem-solving skills. Two senior students, who had participated in electronics competitions, played a key role in the project. Their enthusiasm and creativity, combined with guidance from faculty, helped form a productive and collaborative development team.
VI. Conclusion
This experimental radar transmitter serves as a valuable teaching aid, enabling students to understand radar operation, generate RF signals, and conduct various microwave measurements. Its development required interdisciplinary knowledge and collaboration between faculty and students. The success of this project demonstrates the potential of repurposing old equipment to create effective learning platforms. It not only saves resources but also contributes to the broader goals of innovation and experimental education reform.
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