# Development of small-sized phased antenna arrays on ferrite phase shifters for unmanned aerial vehicles

### Abstract

### Keywords

#### For citation:

Bushkin S.S., Golovin S.A., Soroka N.N. Development of small-sized phased antenna arrays on ferrite phase shifters for unmanned aerial vehicles. *Journal of «Almaz – Antey» Air and Space Defence Corporation*. 2020;(1):19-25.
https://doi.org/10.38013/2542-0542-2020-1-19-25

Development of complex microwave systems, such as active and passive antenna arrays, is a labour- and capital-intensive process involving state-of-the-art technologies. To reduce expenses, the developer strives to minimize the scope of works associated with mocking-up and full-scale experiments. Currently, one of the minimization methods is the full-fledged use of mathematical modelling means at all stages of development, manufacturing, setup and testing. At that, the more sophisticated is the device being developed, the higher is the efficiency of using mathematical modelling means. V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC widely uses mathematical models describing the radiating and distributing systems of an antenna array (AA), using the break-down principle. The antenna system (AS) is broken down into several simpler assemblies that can be modelled using numerical methods subject to some simplifications. The mathematical model of a complex system, such as phased antenna array (PAA), becomes too complicated for calculation, unless we assume that all AA radiating elements are identical, metals have perfect conductivity and there are no losses in the dielectric materials.

The antenna system mathematical model, developed by A. N. Gribanov at V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC, has the following break-down block diagram (Fig. 1).

The above mathematical model is original, it has been designed and developed within V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC for several decades. Its functionality makes it possible not just to predict AS parameters, but also to analyse experimental data. Our colleagues, being its immediate authors, have made numerous publications about the peculiarities and capabilities of developed mathematical model for the PAA and APAA design [1]. By the example of PAA with electronic beam control for an unmanned aerial vehicle (UAV) (Fig. 2), this paper considers the use of mathematical model for achieving PAA characteristics required under the SOW at the stage of its setup and testing.

**Fig. 1**. Block diagram of PAA mathematical model break-down

**Fig. 2**. Appearance of PAA developed and manufactured at V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC for unmanned aerial vehicle

The considered PAA is distinguished from most known PAA by its small electrical size of about 10-15 wave lengths, and small number of radiating elements. The antenna emission system is designed in the form of an array of waveguide radiating elements with an increment of 16 mm in the azimuthal plane and 20.5 mm in the elevation plane. The energy distribution system is a waveguide system. The phasing system is based on Reggia - Spencer ferrite phase shifters [2, 3] with the use of control device designed based on PLIC, composite transistor switches and powerful MOSFET-transistors for control of inductive load.

The listed set of technical solutions provides for small dimensions, maximum AG, low level of background radiation; however, it sets the task of enhancing the accuracy of phase front implementation to a few degrees through elimination of all potential causes of amplitude and phase errors in the PAA aperture.

The design features and accuracy of antenna system and its elements manufacturing have the same level of importance. It is known that, at random distribution of phase errors in the PAA aperture, the background radiation level can be estimated using formula 1 [4].

(1)

where σ is root mean square implementation error of phase distribution in radians; N is number of PAA elements.

At the same time, if due to some design or methodological solutions the errors are of periodic nature, then the level of side lobes increases by dozens of times due to this periodicity. Unfortunately, this effect could not be avoided in the first PAA prototype.

When measuring radiation characteristics of an antenna, such an increase of the side lobe was revealed at upper frequencies in the radiation pattern (RP) of the azimuthal plane within the range from 70 to 90 and from -70 to -90° (Fig. 3).

To reveal the origin of this lobe, the mathematical model of a small-size PAA was used [5]. Using the numerical method of antenna equivalent phase distribution estimation by measured RPs, a high value of errors of phase distribution in the PAA aperture plane of a correlated nature was predicted (Fig. 4).

As a result of analysis of RP obtained using mathematical modelling (Fig. 5) and equivalent line (Fig. 6) built based on the amplitude and phase distribution measured by channels (Fig. 7), the version about errors of phase distribution of the PAA aperture was not confirmed.

**Fig. 3**. Radiation pattern in the azimuth plane of PAA prototype for a UAV

**Fig. 4**. Modelled equivalent line of phase distribution of PAA by measured RP

**Fig. 6**. Equivalent line of phase distribution of PAA by measured phase distribution

**Fig. 7**. Measured phase distribution of PAA aperture

The next step for revealing the lobe origin in the range of 70-90 and -70..._90ه in the azimuth plane consisted in recording the amplitude and phase distribution in the PAA aperture plane using the near-field scanner (Fig. 8). This data made it possible to determine and measure the shift of phase centres of the radiating panel (Fig. 9) relative to their geometric centres.

**Fig. 8**. Phase distribution of a fragment of the aperture of PAA prototype for a UAV

**Fig. 9**. Design of the radiating panel of PAA for a UAV

To simplify the manufacturing technology, the considered antenna included the radiating panel of a double row structure, where the wide walls of waveguides bended along the external sides of the radiating panels. This bend causes an increase in the size of the narrow wall of radiating element in the antenna aperture area and, therefore, a shift of phase centres of the radiating panel relative to the geometric centres of PAA elements.

The adjusted mathematical model of PAA, where the radiating panel design features were taken into account (Fig. 10), confirms that the main reason for the side lobe increase in the range from 70 to 90 and from -70 to -90° is the shift of phase centres of the radiating panel relative to the geometric centres. Therefore, further use of the double-row structure of the radiating panel requires its modification.

Table 1

Radiation characteristics at f_{cp} of PAA for a UAV

Parameter name |
Azimuth |
Elevation |

Beam width (by -3 dB level) |
3.8° |
8° |

SLL |
-28.5 dB |
-22 dB |

Implemented phase distribution RMSD |
4.3° |

## Results of development and manufacture of PAA for a UAV at V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC

The considered PAA has an amplification gain exceeding 28 dB and a zero depth of less than -30 dB at f_{cp}, other characteristics are specified in Table 1, and RPs are shown in Figures 11 and 12 and in 3D format in Figure 13.

**Fig. 12**. a - RP in the azimuth plane of PAA prototype for a UAV in various angular positions; b - RP in the elevation plane of PAA prototype for a UAV in various angular positions

**Fig. 13**. а - 3D RP of PAA prototype for a UAV; b - spatial RP of PAA prototype for a UAV

To sum up, it is to be noted that, by virtue of mathematical modelling, already the first prototype of a small-size PAA was successful in terms of radiation characteristics that met all the requirements of SOW, in spite of both technical and technological complexity of antenna system developed at V. Tikhomirov Scientific-Research Institute of Instrument Design, JSC.

## References

1. Синани А. И. 50 лет Научно-исследовательскому институту приборостроения им. В. В. Тихомирова // Антенны. 2005. № 2.

2. Старшинова Е. И. Сверхвысокочастотный фазовращатель. Патентное изобретение № 2207666. 2002.

3. Фирсенков А. И., Чалых А. Е., Старшинова Е. И. Сверхвысокочастотный фазовращатель. Полезная модель № 142373. 2014.

4. Хансен Р. С. Фазированные антенные решетки. 2-е изд. М.: Техносфера, 2012. 560 с.

5. Грибанов А. Н., Гаврилова С. Е., Павленко Е. А., Чубанова О. А. Программа расчета пространственной диаграммы направленности плоской ФАР/АФАР. Программа ЭВМ № 2015610685. 2015.

### About the Authors

**S. S. Bushkin**Bushkin Sergey Sergeevich – Head of the Laboratory

Research interests: antennaactive phased antenna arrays (APAA), phased antenna arrays (PAA), mathematical modelling of antenna systems, APAA and PAA control systems, PAA setup methods.

**S. A. Golovin**Golovin Sergey Alexandrovich – Engineer of the 1st category

Research interests: antennaactive phased antenna arrays (APAA), phased antenna arrays (PAA), mathematical modelling of antenna systems, APAA and PAA control systems, PAA setup methods.

**N. N. Soroka**Soroka Nikolay Nikolaevich – Engineer of the 2nd category

Research interests: antennaactive phased antenna arrays (APAA), phased antenna arrays (PAA), mathematical modelling of antenna systems, APAA and PAA control systems, PAA setup methods.

### Review

#### For citation:

Bushkin S.S., Golovin S.A., Soroka N.N. Development of small-sized phased antenna arrays on ferrite phase shifters for unmanned aerial vehicles. *Journal of «Almaz – Antey» Air and Space Defence Corporation*. 2020;(1):19-25.
https://doi.org/10.38013/2542-0542-2020-1-19-25