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METHODS OF DIVERSITY OF MOBILE COMMUNICATION 
ANTENNAS MOUNTED ON A SINGLE MAST 
A.Abdukadirov (PhD, Tashkent University of Information Technologies) 
The modern rapid development of mobile (cellular) communication systems, 
bringing many new conveniences in our life, at the same time requires 
implementation of many works on planning, organization and maintenance of 
cellular networks. Particularly, issues of mobile networks’ base stations (BS) 
installation (especially in urban regions) has an increasing relevance in connection 
with the growing number of BSs, hardening ecological and electromagnetic 
restrictions, complication of antenna and mast constructions, etc. Cellular operators 
install their BSs according to their frequency-terrain planning and respectively, 
install antenna and mast constructions that, as a rule, have similar constructions 
and diagrams. Growth of a subscriber base and consequently need to increase a 
number of BSs leads to installation of several antennas and masts of different 
mobile operators on the same buildings and constructions (Fig. 1). 
Fig.1. Appearance of the building with BS antennas in urban regions 
Installation of a large number of bulky antenna and mast constructions of 
mobile communication is not absolutely desirable in a number of the city regions 
having important architectural, tourist and historical values as they worsen the 
esthetic appearance of those places. In this regard there is a need to minimize 
damage from installation of antenna and mast constructions in representative 
regions of the cities. 
Panel antennas representing antenna grids of cross radiation from symmetric 
vibrators supplied with reflectors are generally used for creating mobile networks 
in cities. Vertical symmetric vibrators in one or two rows are placed in a panel. 
The panel antennas have mechanical or electrical control of a tilt of the main beam 
pattern to regulate cover zone. 
Minimizing cross-effect of such antennas will be one of the major factors in 
development of technology of mobile antennas joint installation on a single mast. 
First of all, such influence is possible through the induced resistance which 
changes input resistances of antennas that leads to a mismatch of an antenna-
feeder path of BS. The vibrators that are in near distance to each other are called as 

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“connected vibrators”. Interference of connected vibrators is similar to the 
interference of connected oscillating circuits with concentrated constants. The field 
created by a system of vibrators is a result of addition of the fields created by 
separate vibrators taking into account phases of this field, defined as a difference 
of the course of rays, and a phase difference of currents in radiators. In the specific 
case, when vibrators are identical, parallel and are powered equally, the induced 
resistance is called mutual resistance. It is the function of values of l/λ, d/λ and h/λ, 
i.e. they are defined by exclusively geometrical system size. (Here l - length of a 
vibrator shoulder, d - distance between vibrators of the antenna, h - spacing 
between the panel antennas and λ - wavelength). 
The active and reactive components of mutual resistance depending on the 
relative distance d/λ between vibrators are accepted both the positive, and the 
negative values and in case of some d/λ values pass through zero. Similar 
dependence is noticed in case of change of h/λ. Respectively, the active component 
of the induced resistance can be positive or negative. 
Radio signal propagation and, therefore, value of the induced resistance is 
influenced by the restriction placed between antennas. Therefore, it is possible to 
assume that the restriction-shield placed between panel antennas of mobile 
network allows reducing vertical distance between antennas without 
communication quality deterioration. There is a matter of the restriction-shield 
shape. Indeed the restriction in the shape of, say, cutting-edge will not reduce but 
increase the cross impact of antennas. Therefore, a smoothly changing shape of a 
restriction-shield was selected for further research, so as wave’s diffraction on it 
will have considerable loose as, for example, on a shield in the shape of a sphere, 
cylinder or an ellipsoid of rotation. 
An experimental installation has been created for these purposes. The 
transmitting part consisted of the microwave generator G4-83 connected to funnel-
shaped antenna by coaxial cable and coaxial-to-waveguide transition. 
The receiving part consisted of the funnel-shaped antenna connected to 
Agilent E4407B spectrum analyzer through waveguide-to-coax transition and the 
coaxial cable, as well. The restriction-shield was placed between the receiver and 
transmitter. Frequency of the generator was selected equal to 10GHz (λ = 3 sm), 
and simulation coefficient - equal to 11 that corresponded to operating frequency 
range of GSM standard – 900MHz. 
Block diagram of the installation to weakening an electromagnetic field on 
restrictions of different shape is given in fig.2. 
Experiments discovered that the power level on the receiver input decreases 
in case of installation of restriction-shield in the shape of a sphere or cylinder in 
average by twenty and more dB, i.e. 100 times and more. Therefore, the 
restriction-shield in the shape of a sphere or cylinder gives an increase in 
decoupling between antennas more than 100 times. 
A great interest for us represents also an influence of value of the relative 
spacing of h/λ between an antenna and a restriction as well as between two 

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antennas on value of the induced resistance, i.e. on value of the standing wave ratio 
(SWR) in the panel antenna feeder. 
Fig.2. Block diagram of the experimental installation on research of weakening a field on 
restriction (1 – G4-83 microwave generator, 2 – coaxial cable, 3 – transmitting funnel-shaped 
antenna, 4 – restriction-shield, 5 - receiving funnel-shaped antenna, 6 - spectrum analyzer) 
A mobile panel antenna, restriction-shield made full-scale of the metal lath 
with cells of 35 mm and a spectrum analyzer FSH-6 have been used for this 
experiment. The spectrum analyzer had built-in generator which was connected to 
the antenna, and dependence of SWR values on frequency was displayed on the 
analyzer display. 
Block diagram of the experimental installation on restriction-shield 
influence on the SWR value in the feeder of transmitting panel antenna is shown in 
fig. 3. 
Fig.3. Block diagram of the experimental installation on research of restriction-shield influence 
on the SWR value in the feeder of transmitting panel antenna (1 – spectrum analyzer FSH-6, 2 – 
coaxial cable, 3 - antenna, 4 - restriction-shield) 
A distance between antenna and a restriction-shield changed during the 
experiment. It was discovered that existence of a restriction-shield brings an 
increase of the SWR value in the feeder from 1,20 to 1,21. In case of increasing the 
size of a restriction-shield from 40cm up to 75cm in diameter the SWR value 
increased only for 0,05. That is, the extremely feeble dependence of the antenna 
matching on value of h/λ and the size of a restriction has been observed.
A diagram of such an installation option of different mobile operators 
antennas on one mast with use of a spherical shield is given in fig. 4. 
Fig.4. A diagram of different mobile operators antennas on one mast with use of a spherical 
restriction-shield (1 - panel antennas, 2 - a mast, 3 - feeder paths, 4 and 5 – BS transceivers, 6 – 
a building roof, 7 – a restriction-shield) 

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Also, one of the factors influencing on the value of antennas diversity is 
spatial selectivity of antennas. But, since mobile station antennas have a wide 
range of directivity, this factor can be neglected. 
Thus, using restriction-shields between different mobile operators’ panel 
antennas allows to considerably reducing the distance between antennas when 
installing them on one mast and it can decrease a concentration of antenna masts 
installation on roofs, especially in central representative areas of the cities. And 
this, in turn, will improve esthetic architectural image of our cities.