6-18GHz Low-power Programmable Attenuator Research Design Technology

TWT is a kind of microwave electronic vacuum device used to amplify microwave signal energy, which has the advantages of low-noise, high power capacity, high-gain, broadband, etc. It’s widely used in radar, communications, electronic warfare, etc. TWT’s production process is complex, and the testing method is backward. Our research group aims to design a set of suitable for automatic test system of TWT, hope to be able to improve the test efficiency of TWT and deal with the test data, it will have very important meaning for the mass production and the TWT’s researching.In the broadband travling wave tube automatic test system, programmable attenuator place in the power divider back, in the long time test of traveling wave tube, ensuring each of signal power at each frequency point can have an independent and program control changes.The main content of this article is research on programmable attenuator design principle and design method on the basis of the understanding of TWT automatic test system of each parts, and under the condition of existing experimental study of a small power program-controlled attenuator. In this paper, the main work content as follows:1. The hardware composition of the TWT’s launching part and the development of the current domestic program-controlled attenuator are introduced. Simply introduces the principle of microwave transmission line, and system to study the power attenuator’s design principle and the method of attenuator’s design.2. In this paper, according the attenuator’s actual need, chooses two suitable chip of attenuator. The attenuator’s largest decay can be up to 25 d B, can work within 6 ~ 18 GHz bandwidth. According to the working frequency, the actual situation of attenuator chip to choose the appropriate substrate material, design the microstrip transmission line and the correct peripheral circuit. Finally, using Altium Designer and Solid Works software completed two programmable attenuator circuit schematic diagram, layout and the metal structures.3. According the control principle of programmable attenuator, a low frequency control circuit which use the microcontrollers as the control center is designed in this paper. The code of this circuit was finished by Keil u Vision3 software, and the circuit simulation was proceeded in proteus software.4. Complete the programmable attenuator and the control circuit physical production, during their production process, we need be have a attention about the circuit soldering and circuit debugging. Test the control circuit with multimeter and computer, and test programmable attenuator with the control circuit, microwave signal source,dynamometer.