Design Of Shortwave VSWR Tester Based On DDS Technology

Currently, with the rapid development of wireless communication technology, shortwave communication which has long communication distance, high maneuverability,small volume and etc. is widely used in wireless communication. The antenna feed as areceiving and transmitting device is an important component of the short wavecommunications. The performance of match between antenna and feed directly affects thequality of communication. Therefore, it is indispensable that studying and designing ahigh precision capable of automatically measuring HF antenna VSWR measuring.This paper analyzes the development VSWR measurement technology and introducesthe principle of VSWR bridge. This paper proposes using the amplitude-frequencyreceiver instead demodulator of VSWR bridge and realizes the improved the ability ofharmonic suppression of measuring system. At the same time, the signal source isintegrated in the tester and this paper accomplishes the improved the overall design of thedetection system of VSWR.This paper bases on direct frequency synthesis technology to complete the design offrequency signal source of the system. It realizes an output frequency hopping with highspeed, high precision and high controllable by using AD’s AD9852DDS chip as the corecomponents of the signal source. This paper uses STM32F103RCT6which is a32-bitMCU based on Cortex-M3of ST as a control unit.This paper analyses the advantages and disadvantages of frequency synthesistechnology and ultimately determine uses AD’s AD9852DDS chip as the core componentsof the signal source which realizes an output frequency hopping with high speed, highprecision and high controllable by fully taking into account the direct frequency synthesis(DDS) technology unique advantages. It makes the entire test system with a small, stableperformance, low cost characteristics by fully using internal ADC and other resource ofSTM32F103RCT6. Finally, this paper completes the design of hardware and software ofthe system, and it does a measurement on the system. The error of results in the measurement is±0.2when the VSWR is between1.3and3.0. The results can satisfythe performance requirements of the system and it indicates that the system has a highaccuracy and high value of practical.