The Design Of An Adaptive Attenuator And Its Miniaturization

With the rapid development of communication technology and the wide application of wireless devices,the frequency spectrum in the same frequency band is complex,so the electromagnetic interference between devices is becoming more and more serious.In industrial applications,field electromagnetic monitoring,high voltage electrical control and other complex electromagnetic environment monitoring,the system needs to be equipped with the ability to deal with various complex environments.In the electromagnetic environment,there may be adjacent-frequency interference or co-frequency interference due to the large number of equipment,or strong electromagnetic signal noise due to the high power of some transmitting equipment.Or some equipments will be interfered easily due to the exposure of equipment antenna in the environment.The results includes equipment overload,spectrum blocking and target signal loss,etc.Therefore,corresponding measures should be taken to solve the problems of EMC among devices of monitoring platform in complex electromagnetic environment to avoid serious consequences.In order to improve the anti-interference ability of the equipment in the complex electromagnetic environment,the research of EMC adaptive anti-interference control technology is carried out in this paper.In this paper,an adaptive attenuator is designed.Its working frequency range is 1-4GHz,and it can carry a high-power signal of 40 d Bm.It has two working modes: automatic and manual.The automatic mode can attenuate the signal within the range of 0d Bm?30d Bm according to the input signal size.The output power is stably controlled below-10 d Bm.The manual mode can realize the custom adjustment of the attenuation.The adjustable attenuator range is 0?41.5d B,and the attenuation accuracy is within ±1d B.The main work of this paper is as follows:Firstly,the research background of the adaptive attenuator is analyzed,the principle of the automatic control system is described,the scheme of the adaptive attenuator is constructed,the technical route of the design is given,the system functions and index requirements are analyzed,the main devices and indicators are introduced,and the component selection is completed.Using the combination of circuit modules of microwave switch,fixed attenuator and numerical control attenuator to reach a large dynamic range of attenuation.And the numerical control attenuator module are protected.By sampling and detecting the input and output signals and using the broadband digital control attenuator variable technology,the control flow design is completed,so that the attenuator system can be adaptive processing according to the signal size and accurately control the atten1 uator attenuation.Through control and calibration,the upper computer software can be displayed accurately,and the working state of the attenuator can be visualized.In order to reduce the size of the attenuator,a miniaturization design was carried out.The simulation design of the directional coupler was completed by using the multi-node serrated coupling line structure of the microstrip circuit.The coupling degree of the coupler in 1-4GHz was 20 d B.At the same time,based on SS114 numerical control attenuator chip,ADRF5132 microwave switch chip,AD8318 power detector chip and HMC658LP2 E fixed attenuator chip and other IC chips,the design of microwave circuit PCB is completed,the size of which is 11cm×9.5cm.The size ratio was reduced by 86.1% compared with the originalThe adaptive attenuator designed by circuit module and miniaturized by IC chip are tested in practice.The test items mainly include functional requirements,maximum loadable power,attenuation range,attenuation precision,response time and SWR.The test results show that the designed two kinds of adaptive attenuators meet the design expectations.