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УДК 621.396
АКТИВНЫЕ ФАЗИРОВАННЫЕ АНТЕННЫЕ РЕШЕТКИ (АФАР)
Александр Александрович Андросов
Сибирский государственный университет геосистем и технологий, 630108, Россия, г. Новосибирск, ул. Плахотного, 10, магистрант кафедры фотоники и приборостроения, тел. (923)226-26-71, e-mail: qvinton.555@mail.ru
Игорь Николаевич Карманов
Сибирский государственный университет геосистем и технологий, 630108, Россия, г. Новосибирск, ул. Плахотного, 10, кандидат технических наук, доцент, зав. кафедрой информационной безопасности, тел. (903)937-27-90, e-mail: i.n.karmanov@ssga.ru
Рассмотрены основные преимущества и недостатки активных фазированных антенных решеток по сравнению с пассивными фазированными антенными решетками, а также ряд проблем, связанных с их разработкой и созданием радиоэлектронных систем на их базе.
Ключевые слова: активные фазированные антенные решетки, радиоэлектронный комплекс, радар.
ACTIVE PHASED ARRAY ANTENNA (APAA)
Alexander A. Androsov
Siberian State University of Geosystems and Technologies, 10, Plakhotnogo St., Novosibirsk, 630108, Russia, Graduate, Department of Photonics and Device Engineering, phone: (923)226-26-71, e-mail: qvinton.555@mail.ru
Igor N. Karmanov
Siberian State University of Geosystems and Technologies, 10, Plakhotnogo St., Novosibirsk, 630108, Russia, Ph. D., Associate Professor, Head of Department of Information Security, phone: (903)937-24-90, e-mail: i.n.karmanov@ssga.ru
The main advantages and disadvantages of active phased array antennas in comparison with passive phased array antennas are considered, as well as some problems associated with their development and creation of radio-electronic systems on their basis.
Key words: active phased array antenna, radio-electronic complex, radar.
Electrically scanning antennas - phased antenna arrays (PAA) is widely used in modern radar systems. The development of new ground, aviation and space radio
complexes based on active phased array antennas (APAA) provides, in comparison
with passive PAA, additional opportunities in terms of energy potential, controllability, reliability, which allows significant expanding of the scope of tasks to be solved.
APAA is a radiotechnical system in which the radio transmitting device and the high-frequency receiver are integrated into the antenna array in the form of a distributed structure, including the transceiver active modules (AM) as the main nodes [1,2].
So, during the development of the APAA there is a need for an integrated approach, based on the development of their theory, taking into account the linkage be-
tween the electrodynamic properties of the emitters of the antenna of the canvas and the radio transceiver AM characteristics for different types of signals, accounting for boundary effects, technological and temporary destabilizing factors, the failure of the modules.
Further development of modern antenna systems is the construction of active phased array antennas (APAA). These gratings consist of modules, which include, in addition to emitters and phase shifters, active elements for amplification, frequency converters, analog-to-digital converters, and other devices for preliminary spatial and temporal signal processing.
The use of APAA in radar special systems has a long history. However, the further development of the element base of APAA modules allows to expand their scope. The production of a solid-state short-wave transceiver module of centimeter range in integrated design allows, for example, multifunctional aircraft radar in the active version or intelligent digital antenna systems [2].
The advantages and disadvantages of APAA are well known. The introduction of active elements into the microwave path allows not only to reduce losses, but also to increase the emitted power, simplify the distribution system, improve the weight and size characteristics of the antenna system, as well as to build a more efficient system of signal processing, adaptation, polarization signal processing, multi-target operation, etc. However, a sharp increase in the cost of the antenna system - a significant lack of APAA - should be justified by the expansion of the functionality of the electronic system and a significant improvement in the characteristics.
Currently, the development of the theory and technology of APAA is conducted by many research teams for different ranges of operating frequencies, the level of emitted power, directional characteristics and control, and various applications and functionalities. The inclusion of active elements (or devices) into the antenna array turns it from a passive mutual device into a multi-element transceiver system with the characteristics inherent to the transceiver devices, except for the directional characteristics and antenna control. This fact explains the expansion of the circle of specialists working in the field of APAA spatiotemporal multichannel signal processing. In APAA, as in any radio-electronic system, there are questions of noise immunity, signal to noise ratio of the construction of optimal systems of adaptation, signal processing, etc.
In APAA, unlike PAA, it is possible to significantly expand the operating frequency band and, moreover, to build ultra - wideband (UWB) electrically scanning antennas transmitting and receiving ultrashort (about one nanosecond and shorter) radio or video pulses. This opens up the possibility to generate UWB radar for detection and recognition of low-observable targets.
Progress in the development of new types of aircraft and missiles, which became particularly intense by the middle of the XX century, led to a significant increase in the speed of the targets and reduced their effective surface scattering (ESS). This situation led to significant improvements of radar stations as one of the best means of detecting and monitoring air targets. It was during this period that phased array antennas (PAA) began to be widely deployed in radar systems for various purposes. However, their development has shown that the replacement of the mirror antenna with passive PAA in-
creases the loss of energy in the high-frequency part of the radar several times. To preserve the tactical characteristics of the radar, these losses had to be compensated by increasing the transmitter power output that resulted in an increase in weight and volume. Simultaneously the power consumption of the radar increased.
For radars installed on an air carrier or a space platform, such an increase in volume, weight and energy consumption is usually almost impossible. As for ground-based radars, especially those with longer range target detection, it's also problematic. The creation of new types of aircraft and missiles has led to an increase in the speed of the target and reduce their ESS. Under these circumstances a need for use of electrical scanning of the beam in the radar occurs, and increase in the output power is also required. The use of passive PAA in them led to an increase in the volume and weight of the equipment, which does not allow solving the problem - "increasing the power + maintaining the mobility". One of its real solutions was the transition to the use of active phased array antennas (APAA) in radar.
In APAA all elements are interconnected, intensively influence each other's parameters and, as a result, determine the electrodynamic characteristics of the lattice, and therefore APAA is considered as a single complex, and its design is a system task. The development of a radio-electronic complex with APAA leads to a significant change in the design process of other systems of the complex, starting with signal processing and ending with the power supply. To date, theoretical studies, simulation results, experience in the development and testing of radio systems with APAA allowed to formulate the advantages and disadvantages of APAA.
The main advantages of APAA:
- the possibility of creation on their basis of essentially new integrated radio-electronic complexes (REC) that provides multi-functionality, flexible management of spatial characteristics and a high energy potential, adaptation to fast-changing conditions and complex interference conditions, thereby meeting the growing requirements for power and weight and size characteristics of antenna systems for different purposes;
- the high level of radiated power provided by summation in the space of many low-power signals, which allows to significantly exceed the power characteristics of a single feeder tract without the danger of an electric breakdown;
- high reliability, provided by the presence of excess elements and their functionality (MTBF of solid-state amplifiers is 104-105 h, APAA - (8-12)103 h; transmitter on traveling-wave tube s - 300-500 h, failure in the solid-state transmitter does not immediately occur and faults accumulate gradually);
- in case of redundancy of active APAA modules and periodicity of maintenance, the failure time of APAA ceases to affect the reliability of REC;
- ease of operation of solid-state afar due to the absence of high voltage (supply voltage of the active modules is quite low - 24...30 V) and, due to the high phase stability, there are no need for adjustment of the amplifiers during operation, their replacement is easily carried out during routine maintenance, REC with APAA are designed as maintenance-free system;
- low mass-dimensional characteristics of the solid-state transmit / receive modules (TRM) of APAA, allowing to design multi-element grating with high energy potential. Experience of the design of solid-state APAA showed that when the average power of the transistors used (40 W), the mass-dimensional characteristics of the grid are much better than those of antenna systems with a transmitter on electron-vacuum devices, the absence of a powerful high-voltage modulator gives an additional gain in weight and overall dimensions that allows to place all the APAA equipment together with power sources on one board or ground vehicle [3-5];
- the problems of losses in distribution paths on the general characteristics of the system are significantly weakened, since the amplifying devices in TRMs allow to compensate them, and the absence of losses at a high level of power in dividers and phase shifters allows to simplify and reduce the cost of these devices, and at the same time to increase the speed of the beam control system [6];
- operation in a wider frequency band and the controlled polarization scanning sector, which makes it possible to build broadband and ultra-broadband antenna systems based on APAA with electric scanning, which not only detect unobtrusive targets (or sources), but also carry out their identification [7,8];
- gain in signal processing - for on-board radar, it is 6 dB, which increases the range by 40%; in addition, radars with APAA allow to form: dips in directional diagram towards electronic warfare; several beams that provide simultaneous modes: air-air, air-surface, bypass obstacles; independent directional diagrams for transmission and reception.
Disadvantages of APAA:
- high cost (an order of magnitude or more) both in the design and manufacturing;
- the complexity of the antenna system construction is due to the presence of additional elements (phase shifters, amplifiers, controlled attenuators) in each APAA channel, which require the development and creation of a new element base - TRM with built-in amplifiers, phase shifters and attenuators [9];
- low efficiency (about 2 times less) of low-power transistor amplifier devices in comparison with the powerful transmitters of the PAA, which leads to technological difficulties with heat transfer in the canvas of the antenna lattice, radiation resistance and reliability [10];
- the lack of a methodological framework with an integrated approach to the design of the APAA;
- the absence of metrological support in production, control and operation.
In the process of implementing REC with APAA the need to create maintenance and repair base and testing equipment will appear. The cost of such additional equipment can be comparable with the cost of the development of the APAA itself. However, undeniable progress in the development of integrated high-frequency TRMs will contribute to the creation of solid-state APAA. At the same time, the use of APAA in REC is economically justified when the complex itself has to provide multifunctional operation with high energy potential, mobility and adaptation to the rapidly changing environment in conditions of active radioprotection.
Conclusion
To date, the problem of distribution of individual signals to the modules and channels of PAA and APAA is mostly solved. The element base existing in our country and abroad allows not only to create all the necessary components, but also to perform the integration of optical components on a single substrate in the form of fiberoptic interface, added to each module. Further reduction of weight, dimensions, energy consumption and expansion of functionality is associated with modification of the design of typical APAA modules, in which integral optical elements are combined on a single substrate, and further improvement of the characteristics of APAA (bandwidth, signal to noise ratio, dynamic range) is associated with the use of optical phase shifters and fiber delay lines in the design of APAA modules.
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© А. А. Андросов, И. Н. Карманов, 2018
