The Design And Realization Of The Prediction System For The Performance Of HF Circuits

This paper mainly studies the forecast method of2-30MHz shortwave circuit’sperformance and the calculation method of sky wave field strength’s coverage.Because of shortwave communication effect by specific communication location,circuit time, season, day and night, frequency and so on many conditions vary greatly,so we must predict the shortwave radio communication circuit.The shortwave communication circuit’s performance we discussed in this papermainly includes the following circuit parameters: critical frequency of E layer, F2layer critical frequency, basic circuit MUF, optimum working frequency, maximumusable frequency and the lowest usable frequency. Communication frequency withwhich these parameters mainly affect the user’s choice for the communicationfrequency, provides a suitable working frequency to user for a shortwavecommunication usage. When we predict the critical frequency of the E layer and F2layer critical frequency, we mostly use the method that mentioned in ITU-R P.1239recommendations; other parameters are mainly use the method noticed in the ITU-RP.533.The forecast of sky wave field strength includes252methods for the path lengthless than7000kilometers, the FTZ method for the path length over9000km, and theinterpolation method for the path length between the7000km and9000km. Thesemethods mainly reference the corresponding formula of ITU-R P.533.The analysis of Sky wave field strength in this paper include the field strengthcoverage of contour tracing algorithm, contour filling algorithm, contour labelingalgorithm and3D Earth field coverage display. Contour tracking using the commonrectangular grid contour tracking of the terrain elevation; contour filling method uses relatively simple area filling algorithm; contour labeling using field put forward bythe difference method for maximum labeling.Practice shows that shortwave circuit performance of this high precision,relatively perfect function, diversity characteristic results prediction system, cansatisfies the most of user calculations and the prediction of short circuit performance.