I. Introduction
With the continuous expansion of higher education and the rising costs of laboratory equipment, many universities are facing a severe shortage of experimental instruments. To address this issue, repurposing old or discarded equipment has become an effective strategy to reduce expenses and enhance the availability of lab resources. Radar transmitters play a crucial role in radar education, but their installation is often limited by factors such as budget constraints and space availability. Developing a simple and practical experimental radar transmitter has therefore become an important goal for both teaching and research.
As military technology advances and older lab equipment is replaced, a large amount of unused or obsolete hardware accumulates in laboratories. Many components within these systems—such as magnetrons, thyratrons, and waveguides—still retain functional value despite performance degradation. These spare parts, which were previously discarded, now serve as a valuable resource for building low-cost experimental devices. By utilizing these materials, we have successfully developed an experimental radar transmitter that serves as a hands-on learning tool for students.
II. System Design of the Experimental Transmitter
The development of the experimental radar transmitter went through several stages, including team selection, schematic design, assembly, and debugging. Based on available spare parts, the system was designed to include a power supply control module, power supply module, timer, modulator, magnetron oscillator, and measuring instruments like ammeters and voltmeters. The overall structure is shown in Figure 1.
III. Development, Production, and Commissioning
1. Assembly and Testing
Following the schematic, we sourced various components from the existing spare parts inventory. A multimeter was used to test transformers, thyratrons, and magnetrons for basic functionality. After preliminary screening, we assembled the components onto a plywood base according to the design. Electromagnetic compatibility was carefully considered, especially isolating RF lines from intermediate frequency lines and power supplies. After multiple iterations, the prototype was successfully completed.
2. Prototype Assembly and Performance Evaluation
Once the initial version was working, we transitioned to a standard chassis for more stable performance. This process involved further adjustments due to spatial and layout constraints. Through this hands-on experience, trainees gained a deeper understanding of radar transmitter principles and improved their skills in electronics, RF engineering, and mechanical assembly. The final prototype is shown in Figure 2.
Microwave signals operate at high frequencies, where the wavelength is comparable to or smaller than the size of the circuit. This leads to distributed parameters, making microwave transmission fundamentally different from low-frequency circuits. As a result, measurement techniques such as power, wavelength, and standing wave ratio are essential. These will be discussed in detail later.
IV. Application in Practical Teaching
When used in other experiments, the radar transmitter itself becomes a subject of measurement, testing its own performance. The successful production of the transmitter not only addresses the need for RF signal generation but also enables a wide range of experiments that would otherwise be difficult on conventional radar systems.
For example, connecting waveguide components is often challenging on mounted systems, especially for inexperienced students. An independent transmitter allows for greater flexibility, reducing risks and improving safety. It also helps overcome the intimidation factor associated with complex equipment, encouraging more confident experimentation.
1. Transmitter Power and Spectrum Measurement
Power was measured using a spectrum analyzer with a directional coupler to attenuate the signal to a safe level. The results showed a power output of xxW and a spectrum width of xxMHz (see Figure 3).
2. Transmitter Frequency Measurement
A resonant cavity frequency meter was used to determine the transmitter’s frequency. By adjusting the cavity and monitoring the detection current, the frequency was accurately measured (see Figure 4).
3. Standing Wave Ratio Measurement
A standing wave measurement line was used to assess the feeder system’s performance. The probe moved along the waveguide, detecting changes in the electric field. The standing wave ratio (Ï) was calculated based on the maximum and minimum field strengths (see Figure 5).
4. RF Signal Transmission and Reception
The transmitter’s signal was sent via horn antennas and received using a spectrum analyzer. The results confirmed the system’s ability to transmit and receive RF signals effectively (see Figure 6).
V. Innovative Production Experience
Using spare parts from waste equipment to build teaching tools is an innovative approach under market conditions. These instruments are cost-effective, practical, and closely aligned with laboratory needs. They help alleviate funding shortages while fostering student innovation and practical skills.
Two senior students, who had participated in electronic design competitions, were selected for the project. While they had strong theoretical knowledge, the challenge of building a radar transmitter pushed them to develop new problem-solving abilities. Their collaboration with instructors created a dynamic learning environment, stimulating both student creativity and faculty engagement.
VI. Conclusion
This experimental radar transmitter serves as a valuable educational tool, helping students understand radar operation, RF signal generation, and related measurements. It supports experiments in frequency, power, spectrum, and standing wave ratio, as well as signal transmission and reception.
The development of this device required expertise in electronics, RF engineering, and mechanical design. A team of faculty and students worked together, forming a model for hands-on learning and innovation. The successful use of this transmitter can significantly reduce the need for expensive commercial equipment, saving costs and addressing instrument shortages.
Moreover, this project provides a foundation for exploring new methods in experimental education, talent cultivation, and laboratory management. It demonstrates how repurposed equipment can contribute to both academic and technical advancement.
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