ELEC 6341 Final Project Report

ELEC 6341 Antennas

Project Fall 2012

Instructor : R. Paknys

submitted by

Kiran Phalak 6514081

Sudhanshu Chaudhary 6299598

Oussama Alaoudatallah 5530830

1. To find the antenna beam orientation to get maximum advantage of atmosphere :

In this particular case, we are concerned about propagation of signal at 3.5 MHz. At this

frequency radio propagation is dominated by sky wave propagation. Earth has thick layer of

atmosphere around it which has important layer of ionosphere. Ionosphere consists of ionized

gases which results in refraction of electromagnetic waves. Detailed discussion about

ionosphere and bending of waves through ionosphere is discussed in later part. When

transmission signal is bent down from this ionosphere, propagation can be said to be at the

maximum advantage if it travels the information signal to farthest point.

figure 1 : Sky wave propagation indicating grazing angle[1]

The ionosphere is modelled as a spherical reflecting surface at virtual height from earth's

surface. A signal launched at elevation(grazing) angle ψ gets refracted and bent down if it

makes angle(θi) with normal which is greater than that of θm, where θm is minimum angle

permitted for usable frequency. The single hop distance between transmitter and receiver

points is a function of grazing angle. The maximum value of the single hop distance occurs for

grazing angle = 0 or horizontal launch of transmit signal.[2]

Therefore, we need antenna beam which is as close to horizontal launch as possible to take

maximum advantage of atmospheric reflection.

2. Design of antenna having antenna beam in desired direction

From first part we know that transmitter antenna beam should point towards horizon as much

as possible. Therefore our aim is design an economical antenna which will offer maximum

possible gain in least elevation angle possible. One of the important constraint is about space

available. Due to FSI problem antenna must be designed over 100 ft X 20 ft area.

When we consider frequency of 3.5 MHz . It is low end of HF frequency therefore wavelength is

very long. Vee dipole antenna to be effective should have length of at least few wavelengths.

With FSI problems this is not feasible. As antenna of approximately 1000 ft is required.

Quarter wave monopole antenna with modified radials is designed for the solution as shown

below :

figure 2 : Isometric view of monopole antenna with modified radials

Top view and side view shown below figure 3 indicates that antenna satisfies FSI criteria.

figure 3 : View of antenna from (a) left hand side (b) top

This antenna gives the directive radiation pattern as shown below :

figure 4 : E plane pattern of the designed monopole antenna

As seen from radiation pattern this antenna gives the maximum gain of 1.740 = 2.408 dB. And

one of the most interesting thing in our point of view is it has directional beam with elevation

angle of just 14o from ground. In addition to that it has front to back level of - 2.7 dB.

3. Assessment of effect of ground surrounding

These antennas operate at lower end of HF frequency. Effect of ground surroundings is studied

on antenna performance by changing the material relative permittivity and by carrying the

thickness of the wall.

It is being observed that change in material of walls or construction does not affect the antenna

performance by much deal. On the other hand, it is observed that thickness of wall affect the

antenna performance by big deal having thick walls improves the beam direction of antenna by

small margin. This happens because walls absorb more radiations and reflections of the waves.

When antenna performance for the shape of roof is analyzed, it is observed shape of the roof

alters the performance of the antenna.

But on the ground line it should be always considered that designing the surrounding of

antenna which suits performance is not the best option but the designing the antenna which

works satisfactorily irrespective of surroundings is design criteria.

4. Effect of ground conductivity on antenna performance

In the line of sight communication, only one path is assumed to be present between transmitter

and receiver for propagation of electromagnetic waves. But when transmitter antenna radiates,

some of radiated energy is in the direction of ground plane. The energy gets reflected back

upwards fulfilling the conditions of reflection from the surface.

The amount of reflection depends on various factors such as angle of incidence, polarization of

wave, electrical properties.

Ground conductivity also known as soil conductivity is important electrical property which

decides the strength and direction signal. We know perfect electrical conductor reflects all the

energy, similarly ground plane conductivity affect the radiation characteristics of antenna.

Ground conductivity is measured in siemens per meter. Typically ground conductivity value

varies from 10-5 to 5. [3]

Therefore effect of effect of ground plane conductivity on elevation (grazing) angle and gain of

one dipole antenna designed for 3.5 MHz is figured through graph below :

figure 5 : Variation in (a) gain and (b) elevation angle with respect to ground conductivity

This figure 5 indicates there is typical value of 1.7 mS/m below which ground conductivity

adversely affect the radiation pattern of antenna.

5. Evaluation of propagation conditions using propagation prediction software tool

By using the program W6EL , which is used to predict the wave propagation between Montreal

and Rochester, and observing the results over 10 consecutive days .we have figured out the

propagation conditions related to the solar flux and the K index.

By using the universal time (UTC) as a reference . we have observed the results summarized in

the following table :

0

0.5

1

1.5

2

2.5

3

3.5

5.5

0E-

06

1.7

0E-

05

5.5

0E-

05

1.7

0E-

04

5.5

0E-

04

1.7

0E-

03

5.5

0E-

03

1.7

0E-

02

5.5

0E-

02

1.7

0E-

01

5.5

0E-

01

1.7

0E+

00

5.5

0E+

00

Gain(dB)

0

5

10

15

20

25

5.5

0E-

06

1.7

0E-

05

5.5

0E-

05

1.7

0E-

04

5.5

0E-

04

1.7

0E-

03

5.5

0E-

03

1.7

0E-

02

5.5

0E-

02

1.7

0E-

01

5.5

0E-

01

1.7

0E+

00

5.5

0E+

00

Elevation Angle (degrees)

Date SFI K Index Availability

75-100%

Availability

50-75%

Availability

25-50%

Availability

1-25%

13-11-2012 146 0 0000 0100

0600 0800

1400 2330

0130 0530

0830 1130

0930 1030

14-11-2012 142 1 0600 0830

1130 2330

0000 0530

0900 1100

15-11-2012 141 2 0000 0100

0600 0800

0130 0530

0830 0900

0930 1000

16-11-2012 138 2 0000 0100

0600 0800

0400 0530 0130 0330

0830 1100

17-11-2012 138 2 0000 0100

0600 0800

0500 0530 0130 0430

0900 1030

18-11-2012 135 2 0000 0100

1130 2330

0500 0800 0130 0430

0830 1100

19-11-2012 141 2 0000 0100

0600 0800

1100 2330

0400 0530 0130 0330

0830 1100

20-11-2012 141 4 0000 0100

0600 0730

1200 2300

0100 0130

0400 0530

0200 0330

0800 0830

1130 1200

0900 1100

21-11-2012 141 1 0000 0030

0600 0800

1130 2330

0400 0530

1100 1130

0100 0330

0930 1030

0130 0300

0930 1100

22-11-2012 128 1 0000 0030

0630 0800

1200 2330

0530 600

0800 0830

0030 0100

0330 0500

0130 0300

0930 1100

Table 1 : Propagation prediction for 3.5 MHz between Montreal and Rochester

It can be observe,

In general, the frequency 3.5 MHz can propagate with availability 75-100 % from 00:00

to 01:00 & 11:00 to 23:30, regardless of the SFI and K indices.

The availability 50-75 % is in the period 01:00 05:30 depending on SFI and K indices

The availability 25-50% is in the period 01:30 to 03:30 when the SFI is about141 and K is

about 2, while the availability is in the periods 02:00 – 03:30 & 08:00 – 08:30 &11:30 -

12:00 when the K index is 4.

The availability 1-25% appears when K index is 4 in the period 09:00 – 11:00 ,while it

appears in the periods 01:30 -03:00 & 09:30 11:00 when K index is 1.

6. Study about D-layer and propagation with the help of D-layer

The ionosphere layers are consisted of The layers D , E ,F1 , F2 which extend from a height of

about 50 km to over 500 km. The ionosphere layer is ionised by radiation of the Sun. This layer

is so important for HF, where the radio waves are bent due to this layer , in other words, the

waves are reflected back to earth. The higher ionized layer density ,the higher the frequencies

that can be reflected.

figure 6: D, E ,F layers during day and night [5]

These layers are not constant because they depend on the sunlight and the day time .during the

day four layers may be existed D, E, F1 and F2 layers. Their approximate height ranges are:

D layer 50 to 90 km, E layer 90 to 140 km, F1 layer 140 to 210 km, F2 layer over 210 km. [5]

The solar condition affects the presence of the layer, for example the layers F1 and F2 may

consist F layer. At night the D, E and F1 become slightly ionized , which means only F2 layer is

available for communications. The layers E, F1 and F2 refract HF waves, while D layer does not,

That makes D layer so important for HF Communications Due to the possible reflection at D

layer , long communication paths can be achieved ,which cannot be made without reflection.

Since the ionosphere layer is not constant, using the same frequency is not possible over 24

hours, and it depends on the solar cycle. The solar cycles have period of 9 - 14 years. Depending

on the cycle, HF frequencies can be implemented. During low level solar activity period, only

the lower frequencies can be used, while higher frequencies can be successful when the activity

is high. that is because of the high radiation of the sun which makes the ionization high and

hence the more reflection. The communications in HF frequencies are affected by flare

occurring. Flares emit radiation to earth, and that causes ionization of D layer which means

increasing in absorption. Since D layer is present at day time, all communications take place in

daylight will be affected. When a flare occurs HF waves are absorbed, this phenomenon is

called short wave fade out.[5]

figure 7 : E ,F1, F2 maximum frequencies during the day[5]

Fade-outs can be avoided by using a higher frequency. The duration of fade-outs takes time

between about 10 minutes to several hours. During the day a higher frequency can be used

.When the sun rises, the radiation of the sun causes ionization in ionosphere, hence frequencies

increase till noon, then the frequencies drop. At night The layers D, E, F1 disappear, which

means communications during night occurs by the layer F2, at this time the attenuation is low,

and the MUF decreases until just before dawn when this frequency reaches a minimum value.

When solar flares occur, ionization in D layer is increased which means increase in absorption of

HF radio waves. If the radiation of the flares reach high level, HF communications can be

unusable for a period of time which causes fade-outs. Salient features of fade-outs are: [5]

the circuits existed in daylight sectors will be affected, while the circuits existed in

darkness will not be affected.

Fade-outs may last from a few minutes to a few hours, depending on the duration and

the size of the flare.

The magnitude of the fade-out depends on the size of the flare and the relative

position between the Sun and the point where the signal goes through the D layer.

The lower frequencies, the higher absorption, so the lower frequencies are more

affected, and higher frequencies are less affected and may still be usable .

figure 8: fade out effect vs frequency[5]

7. Sunspots and 11 year solar cycle

HF frequencies propagation depends on three factors related to the sun. The three factors are

solar flux , and Ap and Kp indices.[6]

The ionosphere can be considered as number of layers. These layers are ionized due to effect of

sunlight .This ionization affects the radio waves according to the state of ionization. Depending

on the frequency, incident angle, and ionization level, the wave can reflect to escape to the

outer space. The variation in the level of ionization in ionosphere causes different behaviours of

HF frequencies .when the ionization is high , the ionosphere is able to bent the waves, which

means high MUF can be used. The level of ionization is a function of many variables such as the

time of the day and the season and the sunspot cycle which has a period of 11 years.

The higher sunspot, the higher radiation of the sun. The sun emits many particles which have

magnetic field. when the emission is high ,we can predict two effect, the first one is disturbing

the magnetic field of the earth and the second one is increasing the ionization of the

ionosphere. As a result a blackout in HF communications occurs.[6]

Solar flux is a measure to estimate the level or radiation of the sun. The solar flux unit(SFU) is

the radio noised emitted by the sun at a frequency of 2800 MHz. Since there is a close relation

between solar flux and the level of ionization, the conditions for long distance can be predicted

during the peak of sunspot cycle the index can reach the value of 200.[6]

The indices A and K are used to determine the geomagnetic activity. These factors can tell how

much is the magnetic fluctuation, in other words, the disturbance to the ionosphere. The A

factor takes values up to 100,while during a magnetic storm it can reach 200. The K factor

takes values, 2 - 4. However this value can reach 6 during a minor magnetic storm and 9 during

a major magnetic storm, in this case a blackout in HF communications may occur.

8. Observation of the signal strength variation of a AM radio station WHAM on 1180KHz from

Rochester NY

Observation of signal strength of channel WHAM at 1180 kHz is done using a CORA AM/FM

projection clock radio (Model # crx-6750) as shown in the figure 9 :

figure 9 : CORA AM/FM radio used for observation of signal strength

This radio is manually operated AM/FM bands and for the best result, it is had been matched

with big music system which is having digital operated AM/FM band. Radio channel WHAM at

1180 kHz is listened for around 10 days and observation of the signal strength variation from

day to day and day to night is noted down.

The results can be summarized as shown in table 2:

Days Time Signal Quality Notes

13-Nov-12

9am Poor No signals(only noise)

1pm Poor No signal(only noise)

9pm Average Signal + Noise(noise disturbance and interference in

the signal)

11pm Average/Good Signal + Noise(very less disturbance but some time

interference)

14-Nov-12

8:30am Poor No signal(only noise)


9pm Average Signal + Noise(noise disturbance and interference )

11:30pm Average/Good Signal + Noise(very less disturbance but some time

interference)

15-Nov-12

9am Poor No signal(only noise)



1am Average Signal + Noise(noise disturbance and interference in

the signal)

16-Nov-12



8pm Average/Good Signal + Noise (very less disturbance but some time

interference)

11pm Average Signal + Noise(noise disturbance and interference)

17-Nov-12





the signal)

18-Nov-12





the signal)

19-Nov-12





interference)

20-Nov-12


1:30pm Poor No signal(only noise)


11pm Average/Good Signal + Noise(very less disturbance but some time

interference)

21-Nov-12


1:30pm Poor No signal(only noise)


interference)

12:30am Average Signal + Noise(noise disturbance and interference in

the signal)

Table 2 : Signal strength variation of WHAM 1180 kHz from 13 to 21 november 2012

It is being observed that the signal strength from 13thNov to 21stNov at 1180KHz varies with

time. In day time, nothing can be heard but noise, during night the signal starts coming and at

around 8:30pm to 10pm mixed signals are heard like signals from 1180KHz radio station mixed

with noise but sometimes interference occur due to other signals. One thing is noticed that

during interference signal can be identified but cannot be understood. Sometimes, very clear

signal is heard but that is for very less time approximately only for 1 minute otherwise always

mixed with noise is heard.

9. Impact of noise sources:

In the context of our text, Noise sources refer to the sources by which the AM radio signal get

affected i.e. disturbance in the signal or distortion in the signal. There are many appliances in

residential places like TV, Vacuum cleaner, Hair drier, etc. which affect the AM radio signals.

The motors in these appliances cause interference in AM radio signals. Little sound coming

after interference is same as the sound of the motor itself. Very fuzzy noise is observed due to

a table lamp which operates by human touch, when radio under test is kept near the lamp.

Not fuzzy but kind of high pitch repetitive noise signal is observed when mobile phone is kept

dialed from near vicinity of the radio under the test. In the night, time when the signals are

average/good (i.e. Signal + Noise (very less disturbance but some time interference) are less

susceptible to the influence of some noise source than day time when nothing except the noise

heard.

In conclusion, YES the noise sources in my home influence the results and audibility of AM radio

signal.

10. Propagation prediction at 1180 kHz frequency

Propagation prediction at any frequency level can be done if propagation at these frequency is

modeled. 1180KHz frequency lies in Medium frequency(MF) band which ranges from 300 to

3000KHz. Radio-wave propagation prediction models, that can be used for engineering analysis

of communication systems, determine the basic transmission loss between a communications

transmitter and receiver. The propagation of radio waves in MF depends on both a surface

wave and a sky wave and is quite different from propagation at any other frequency. [7]

A] Ground wave propagation prediction method:

The ground wave includes the direct line-of-sight space wave, the ground-reflected wave, and

the Norton surface wave that diffracts around the curvature of Earth. For small distances

between transmitter, radio wave propagates mainly as a surface wave, because the direct and

ground-reflected waves in the space wave cancel each other and as a result the surface wave is

the only wave that is left. This cancellation is takes place due to the fact that the elevation

angle is zero and the two waves (direct and reflected) are equal magnitude and opposite in

phase. This is the condition that exists for the LF and MF band[7].

Surface are predominantly vertically polarized as horizontal component is shorted by ground

conductivity. Surface waves are guided by earth's surface. Charges are induced in earth's

surface. Earth carrying these charge flow can be modeled as leaky capacitor. Therefore

characteristic of earth as conductor can be represented as parallel RC circuit, where

conductivity is modeled as resistor and dielectric constant is modeled as capacitor. This resistor

results in attenuation of wave as it travels. The attenuation function is the ratio of electric field

over lossy earth to that of over perfectly flat surface. [8]

Electric field strength at distance d can be given as : [8]

𝐸 = 𝐴𝐸0

𝑑

where E0 is electrical field over earth's surface at small distance at few wavelengths away from

transmitting antenna.

Berry[9] and stewart[10] give thesmooth-0earth model. The smooth earth attenuation function

used for line of sight propagation when distance is small and earth can be considered as flat.

And electric field is given by :

𝐸 𝑑 = 9.487 𝑃𝐸𝐴 (𝜌)

𝑑

where d is distance in km and PE is effective radiated power in watts and A(ρ) is flat earth

attenuation function. which given by following equations : [11]

figure 10 : flat earth surface model [7]

𝐴 𝜌 = 1 − 𝑅0∆𝑒𝜌2

𝑒𝑟𝑓𝑐(𝜌)

𝑅0 = 𝑒−𝑖𝜋4

𝜋𝑘𝐷

2

𝜌 = 𝑒−𝑖𝜋4

𝑘𝑑

2∆(1 +

ℎ1 + ℎ2

∆𝑑)

these dimensions are given according to the figure 10. [7]

B. Sky wave propagation prediction method:

Sky wave propagation takes place due to refraction and reflection through ionosphere. D,E

layer is responsible for refraction and reflection at medium frequency propagation. Signal is

absorbed by D-layer during day time and is not present during night. Whereas E layer is product

of not only photo ionization but cosmetic and x-rays. Therefore, E layer predominately reflects

the MF signals during night.[12,13]

Signal received gets increasingly stronger as distance increases when it is propagated through

sky waves because it is product of increasingly lower angle of elevation at transmitter. But this

is not the case. The propagation of sky wave depends on latitude but all propagation model did

not consider this factor. The models which consider both latitude and actual path length in

consideration gives accurate results.[14] The sky wave propagation also depends on distance,

time of the day and frequency.

field strength dependence on distance given is given by, [15]

𝐹𝑐 = 231

3 + 𝑑

1000

− 35.5

where field strength is given in dBuV/m and d is distance in km.

In modification to this model Wang has developed MF sky wave model giving field strength.

Wang equation for field strength is, [16]

𝐹𝑐 = 95 − 20 log 𝑑 [6.28 + 4.95 tan(∅𝑚)2] 𝑑

1000

where Fc is field strength in dbuV/m, d is distance in km and φm is geometric latitude.

This can be used now for sky wave propagation prediction. When both ground and sky wave

models are considered then propagation prediction for 1180 kHz.

References:

[1] http://www.ycars.org/EFRA/Module%20C/EMSkyWave.htm

[2] A.R. Harish and M. Sachidananda, 'ANTENNAS and WAVE PROPAGATION', OXFORD

University Press,978-0-19568666-1

[3]Http://www.ips.gov.au/Category/Educational/Other%20Topics/Radio%20Communication/In

tro%20to%20HF%20Radio.pdf

[4] http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/ion2.html

[5]http://www.ips.gov.au/Category/Educational/Other%20Topics/Radio%20Communication/In

tro%20to%20HF%20Radio.pdf

[6] Ian Poole G3YWX, 'Understanding Solar Indices', http://www.arrl.org/files/file/Technology/

tis/info/pdf/0209038.pdf

[7] Nicholas DeMinco, Medium Frequency Propagation Prediction Techniques and Antenna

Modeling for Intelligent Transportation Systems (ITS) Broadcast Applications.(U.S. department

of commerce), NTIA Report 99-368, 1999.

[8] F.E. Terman, Electronic and Radio Engineering, New York: McGraw-Hill Book Co., 1955, pp.

803-808.

[9] L.A. Berry, “User's guide to low frequency radio coverage programs,” Office of

Telecommunications Technical Memorandum 78-247, January 1978.

[10] F.G. Stewart, L.A. Berry, C.M. Rush, and V. Agy, “An air-to-ground HF propagation

prediction model for fast multi-circuit computation,” NTIA Report 83-131, August 1983. (NTIS

Order No. PB 84-145861).

[11] J.R. Wait , “Electromagnetic surface waves,” in Advances in Radio Research J.A. Saxton

(Ed.), London: Academic Press, 1964, pp. 157-217.

[12] D.G. Fink and D. Christiansen (editors), Electronic Engineers Handbook, Chapter 18 “Radio-

Wave Propagation” by R.C. Kirby, New York: McGraw-Hill Book Co., pp. 18-96 to 18-103, 1989.

[13] K. Davies, Ionospheric Radio Propagation, NBS Monograph 80 (U.S. Government Printing

Office), Washington, DC, pp. 2-7, 1965.

[14] ITU-R (International Telecommunications Union), (CCIR-International Radio Consultative

Committee), “Sky-wave field strength prediction method for the broadcasting service in the

frequency range 150 to 1600 kHz,” Recommendation 435-7, International Telecommunications

Union, Geneva, Switzerland, 1992.

[15] ITU (International Telecommunications Union), Final Acts of the Regional Administrative

MF Broadcasting Conference (Region 2), Rio de Janeiro, 1981 (International Telecommunication

Union, Geneva, Switzerland).

[16] J.A. Wang, “A skywave propagation study in preparation for the 1605-1705 kHz

broadcasting conference,” IEEE Trans. $Broadcasting, BC-31, No. 1, pp. 10-19, March 1985.

"We certify that this submission is the original work of members of the group and meets the

Faculty's Expectations of Originality."

Kiran Phalak Sudhanshu Chaudhary Oussama Alaoudatallah

6514081 6299598 5530830

ELEC 6341 Final Project Report

Documents

Transcript of ELEC 6341 Final Project Report