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Medium Frequency (MF) and Lower High Frequency (Lower HF)-DATA Communication systemMF band: This band covers the frequency 300 to 3000KHz. Ground wave method is valid from 10KHz to 3MHz.Sky wave method are valid from 150KHz to 1705KHz. TIS (Travel Information System): These system is used to data communication system in Medium Frequency(MF).

Ground Wave propagation:The ground wave include the direct wave and reflected wave.The ground wave depend on the:Distance between transmitter and receiver.

Change in terrain.Antenna height in the transmitter and receiver.Frequency.Attenuation function.

There are many problems in the ground wave propagation:Land Sea Boundary: Sky-wave interference:(conductivity, permittivity)When the transmit ground wave and sky wave from the same Tx:This maybe let interference between sky wave and ground wave in the transmission before come to the receiver.Curvature of the earth:It is limited for use the ground wave propagation.Frequency:limited until 2MHz.

We take some equations about ground wave:At the distance between Tx and Rx within the line of sight, the field strength is given by:

Case #1.1

The electric field strength at a distance (z) below the surface of the earth is given by:Case #1.2

The Smooth-Earth Model:It is many computation techniques are used in this smooth-earth model: Flat earth attenuation function.Power series expansion. Diffraction.distance between Tx and Rx, These method are different in:height of antenna,and frequency.

The electric field strength when the Tx and Rx antennas are near to the earth with respect to a wavelength is given by:f=1.5;a=2;t=[10:2:700];pE=2500;gc=15+(3./(i.*.00000000125));d=a.*t;e=sqrt(gc-1);k=1;h1=20;h2=10;D=sqrt((d.^2)+(h1-h2).^2);o=exp(i.*pi./4).*sqrt((k.*D)./2).*e.*(1+(h1+h2)./(e.*D));Ro=exp(i.*pi./4).*sqrt(pi.*k.*D./2);A=1-((Ro.*e.*exp(o.^2).*erfc(-.707)));E=(9.487.*sqrt(pE).*A)./d;T=20.*log(E./.001);plot(d,T)f=1.5;a=2;t=[10:2:700];pE=2500;gc=15+(3./(i.*.00000000125));d=a.*t;e=sqrt(gc-1);k=1;h1=20;h2=10;D=sqrt((d.^2)+(h1-h2).^2);o=exp(i.*pi./4).*sqrt((k.*D)./2).*e.*(1+(h1+h2)./(e.*D));Ro=exp(i.*pi./4).*sqrt(pi.*k.*D./2);A=1-((Ro.*e.*exp(o.^2).*erfc(-.707)));E=(9.487.*sqrt(pE).*A)./d;T=20.*log(E./.001);plot(d,T)Case #2.1

When the transmitter and receiver antenna locations are high enough:Case #2.2

When the receiving antenna is near the radio horizon of the transmitting antenna, but not beyond it. Case #3.1

For long paths, the geometry is such that a straight line connecting the Tx and Rx antennas intersects the curve earth. Case #3.2:

Compare between theses cases: We compare these cases by show the value of electric field strength one distance for all cases.At distance = 150Km:E (case#1.1)=55 dBv/150Km At (L.O.S.)E (case #3.2)=140 dBv/150Km At( Long path)E (case#2.2)=120 dBv/150Km At (Far L.O.S.)E (Case #3.1)=0 dBv/150Km At ( Near path)E (case #1.2)=97 dBv/150Km At( Distance (z))E (case #2.1)=295 dBv/150Km At (Near L.O.S.)

2) The smooth earth mixed path model:This model is valid for the same frequency and distance range as the smooth earth model.Losses in first path(from Tx to Rx):Ltr=L1 (d1)-L2 (d1) +L2 (d1+d2)-L3 (d1+d2) +L3(d1+d2+d3) Losses in second path(from Rx to Tx):Lrt= L3 (d3)-L2 (d3) +L2 (d3+d2)-L1 (d3+d2) +L1 (d3+d2+d1)) The total losses:

Cont.

Sky Wave PropagationAt MF, the sky wave propagation are valid from 150KHz to 1705KHz. Regions on the ionosphere: D-layer:(50-90)Km.Ionizations low.This layer has ability to reflect signals with low frequency.E-layer:(90-140)Km.

This layer has ability to reflect signals with higher frequency than D-layer up to20MHz. F-layer:(130-400)Km.F-layer is reflect frequency than D and E-layer up to 30MHz.

High ionization.

Cont.

F-layer:At day, this layer appears two regions(F1 and F2).At night, F1and F2 will mixed.Some equation should be consider on sky wave propagation:Conductivity, permittivity, SNR, attenuation, and power and gain in Tx and Rx.Electron density:LowHighAttenuation:LowHigh

Numbers of sky wave field strength prediction methods:

FCC/Region2 sky wave method:These model is used beyond that distance.ITU sky wave method:Wang sky wave method:Q(m)=Geometric altitudes(degree)V=Tx force (dB), Gs=Sea Gain, Lp=path loss, and Ps=slant propagation distance (Km).F= V + Gs Lp + 106.6 2sin (Q) 20 log (Ps) 0.001(Kr) (Ps)-Lt)

Compare between methods in sky wave propagation:At distance between Tx and Rx=2000Km: FCC/Region2 sky wave method:ITU sky wave method:Wang sky wave method:F=13 dBv/2000KmF=35 dBv/2000KmF=20 dBv/2000Km

ICEPAC Software: ICEPAC (Ionospheric Communication Enhanced Profile Analysis and Circuit) is integrated system. Used for planning and operation of high frequency communication system using sky wave.Command Lines of ICEPAC:Frequency command line.Antenna command line.Fprob command line.Time command line.

Plan for next semester work:Study more information about high frequency by using ICEPAC.Design System by using ICEPAC in High frequency.

ThanksAny questions!!!