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Here, we describe a source of high-power ultrawideband radiation with elliptical polarization. The source consisting of a monopolar pulse generator, a bipolar pulse former? and a helical antenna placed into a radioparent container may be used in tests for electromagnetic compatibility. In the source, the helical antenna with the number of turns N=4...
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Citations
... In recent years, there has been an increasing demand for high-power microwave (HPM) systems and antennas capable of transmitting gigawatt-level power. Various types of antennas for HPM systems, such as impulse radiating antenna (IRA) [1], radial line slot antenna [2], TEM horn antenna [3], and helical antenna [4][5][6][7], have been described in the literature. Helical antennas are widely used in HPM systems owing to their advantages, including their compact structure, simple radiating circularly polarized wave, and wide bandwidth. ...
... The most important consideration in designing an antenna suitable for HPM applications is its increased power handling capacity, which can be achieved in two ways. The first method aims to improve the critical electric field strength with the use of an SF6 gas or a vacuum pump [4][5][6]. The second method aims to reduce the maximum E-field on the antenna through the modification of the antenna structure [6,7]. ...
... For HPM applications, the electric field strength should be taken into account to avoid electrical breakdown in each section. The E-field can be reduced if the wire of the helix is made of a thick copper tube [5]. However, as the wire diameter becomes thicker, the input impedance of the helical antenna decreases [8]. ...
In this paper, a novel helical antenna for high-power microwave is proposed. The proposed antenna is intended to demonstrate improved power handling capacity without any deterioration in matching characteristics, gain, and axial ratio. The proposed antenna with a long helix structure is investigated in order to achieve high gain and a relatively wide impedance bandwidth. By increasing the distance between the helix and the ground plane, an improved power handling capacity is obtained, and the impedance matching problem caused by the proposed method is addressed with the use of a feed-through insulator. In addition, a conical-shaped ground is used to compensate for the gain reduction by increasing the distance between the helix and the ground plane. As a result, the proposed antenna exhibits a gain exceeding 11 dBi and an axial ratio of less than 2 dB within the frequency range of 0.86–1.09 GHz. In addition, its power handling capacity exceeds 50 MW for a 0.7-ns input pulse length in air conditions.
... The axial-mode helical antenna is always used as the high-power radiation antenna for its wide radiation bandwidth, high directivity, and circular polarization (CP) characteristic. [5][6][7] However, in order to achieve the axial-mode radiation, the helix circumference of the helical antenna should be approximately equal to the wavelength of its operating frequency. 8 It means that the dimension of the helical antenna will be larger as the operating frequency decreases, which limits the application of the helical antenna in the place with limited volume. ...
... Hodograph of electric field strength is usually used to estimate the CP characteristic of the helical antenna with a wideband or UWB excitation signal. 6 The excitation signal in this paper is produced by a solid-state pulse generator based on the avalanche transistor. Figure 2 is the waveform of the excitation pulse, which has a 5.5 kV amplitude and 172 ps rise time. ...
An exponential spacing and sinusoidal folded helical (ESSFH) antenna backed with a cavity is developed in this paper. Compared with the conventional helical (CH) antenna, the proposed antenna not only has smaller dimension but also exhibits a wider working bandwidth, a higher gain, and a better circular polarization (CP) characteristic. To reduce the dimension of the helical antenna, a sinusoidal structure is adopted along the circumference of the helix. However, it deteriorates the CP characteristic of the antenna. Therefore, the structure of the exponential helix spacing is introduced into the sinusoidal folded helical (SFH) antenna. Then, to further improve the gain of the ESSFH antenna, its ground plane is replaced by an optimized cavity. Compared with the CH antenna, the helix diameter of the ESSFH antenna D λ is reduced from 0.32 to 0.23, and its volume is reduced to 53%. The ESSFH antenna backed with a cavity has an impedance bandwidth of 0.43–1.02 GHz, which is much wider than 0.48–0.60 GHz of the CH antenna. Moreover, it has an axial ratio of 1.77, while the axial ratio of the CH antenna is 2.61. In addition, its effective potential gain is 0.56, which is 22% higher than that of the CH antenna.
... Generally, there are two kinds of highvoltage sources for driving bipolar pulses. One is the Tesla transformer, for example, the Sinus-type ultra-wideband system developed by the Institute of High Current Electronics (HCEI) [9][10][11][12], and RADAN series developed at the Institute of Electrophysics [13]. e other is to use the Marx generator to generate high-voltage pulse for driving bipolar pulse [14][15][16][17]. ...
... Compared with the "linear" or "Z"-type Marx generator [18], the modified structure is greatly shortened in length. Compared with the bipolar pulse generated by Blumlein line [9], the bipolar pulse generated by a single line is simpler in structure and easier in insulation design and debugging under higher-power conditions (especially when the power exceeds 10 GW). ...
A compact high-power ultra-wideband bipolar pulse generator based on a modified Marx circuit is designed, which is mainly composed of a primary power supply, Marx generator, sharpening and cutoff subnanosecond spark gap switches, and coaxial transmission lines. The Marx generator with modified circuit structure has thirty-two stages and is composed of eight disk-like modules. Each module consists of four capacitors, two spark gap switches, four charging inductors, and a mechanical support. To simplify the design of the charging structure and reduce the number of switches, four groups of inductors are used to charge the capacitors of the Marx generator, two of which are used for positive voltage charging and the other two for negative voltage charging. When the capacitor of each stage is charged to 35 kV, the maximum output peak voltage can reach 1 MV when the Marx generator is open circuit. The high-voltage pulse generated by the Marx generator charges the transmission line and forms a bipolar pulse through sharpening and cutoff switches. All transmission lines used for bipolar pulse generation have an impedance of 10 Ω. When the 950 kV pulse voltage generated by the Marx generator is fed into the transmission line, the bipolar pulse peak voltage can reach 390 kV, the center frequency of the pulse is about 400 MHz, and the output peak power is about 15.2 GW.
... The distance between the ground plane and the receiving antenna was 336 cm. The distance between the receiving antenna and the rotation axis of 320 cm was chosen based on our previous studies [5]. ...
A cylindrical equidistant helix antenna has been created. The helix geometry of the antenna determined its central frequency of the operating band, equal to 1 GHz. This frequency corresponds to the maximum spectra of a bipolar voltage pulse with duration of 1 ns. Helixes identical to those of a single antenna were used in horizontal four-element linear arrays. Antenna arrays with different periods of d were studied in the axial mode with simultaneous excitation of elements by a bipolar voltage pulse of 1 ns duration and in the mode of scanning at a fixed angle in the horizontal plane. Experimental measurements were carried out in the frequency and time domains.
... Helical antennas are widely used in high-power sources of ultrawideband (UWB) radiation [1]. Along with high-power sources of UWB radiation containing a single helical antenna [1,2], sources with transmitting arrays of helical antennas are created [3,4]. Despite the huge variety of helical antennas, cylindrical [2,3] and conical [4,5] one-wire antennas are used in high-power UWB radiation sources. ...
... Along with high-power sources of UWB radiation containing a single helical antenna [1,2], sources with transmitting arrays of helical antennas are created [3,4]. Despite the huge variety of helical antennas, cylindrical [2,3] and conical [4,5] one-wire antennas are used in high-power UWB radiation sources. In this paper, we study cylindrical helical antennas and arrays of such antennas. ...
Studies of the squre array of cylindrical equidistant helical antennas have been perfomed. The array is designed to radiate a bipolar voltage pulse with a duration of 1 ns. In the transmission mode, the change in the effective potential and the elliptisity ratio of radiation along the array axis is studied, when a part of the elements is rotated around its axis at arbitrary angles. The possibility of adjusting the ellipticity ratio at radiation along the array axis within a wide range is shown. The phenomenon of decreasing of effective potential of array radiation in the direction of the main maximum due to the mutual influence of elements was found. The reflection coefficients fron a single helical antenna and an array element were studied in the frwuency domain.
... Interest in the high-power ultrawideband (UWB) sources of elliptical radiation remains stably high in recent years. Single helical antennas [1,2] or arrays of such antennas [3] are used as radiators in the sources of this type. A voltage pulse exciting the helical antenna may be a monopolar pulse ending by a decaying sinusoid [1]. ...
... A voltage pulse exciting the helical antenna may be a monopolar pulse ending by a decaying sinusoid [1]. In [2,3], the radiators were excited by a high-voltage bipolar pulse of 1 ns duration. In [3], a square 22 helical antennas array allowed increasing the peak radiated field Ep, by 1.6 times in comparison with the source based on a single antenna [2]. ...
... In [2,3], the radiators were excited by a high-voltage bipolar pulse of 1 ns duration. In [3], a square 22 helical antennas array allowed increasing the peak radiated field Ep, by 1.6 times in comparison with the source based on a single antenna [2]. Further increase of Ep implies multiplication of the elements in the array. ...
An ultrawideband square 8x8 array of cylindrical
helical antennas has been developed. The antennas are excited
synchronously by a bipolar pulse of a 1 ns duration.
Experimental studies of the array radiation have been carried
out. The array is planned to be installed into a high-power source
of ultrawideband radiation.
... High-power sources of the UWB radiation based on single cylindrical helical antennas and arrays excited by bipolar pulses with different duration are being developed at the High Current Electronics Institute. A source based on a cylindrical helical antenna with N = 4 turns has been considered in [9]. A bipolar voltage pulse with a duration of 1 ns and an amplitude of 200 kV has been fed to the antenna input. ...
... Figure 2 presents the calculated frequency dependences of the VSWR for antennas with N = 4.0, 4.25, and 4.5 turns. It is seen that an increase in number N leads to a low-frequency shift of the lower boundary frequency at a level of VSWR ≤ 2. Using the approach of [9], we determine energy efficiency k w for each variant. To estimate quantity k w , we use energy spectra of a unipolar pulse with a duration of 1 ns and a bipolar pulse with a duration of 2 ns. ...
... Based on the approach of [9], we determine the position of the center of emission with the aid of criterion ≈ const, where is the radius vector of a point in the far-field zone and is the radius vector of the reference point. Point (x 0 , y 0 , z 0 ) = (0, 0, 0) serves as the origin of coordinates in which we determine radius vectors and . ...
Ultrawideband elliptically polarized radiation is numerically and experimentally studied. The analysis is performed for the axial radiation of a cylindrical helical antenna that is excited by a bipolar voltage pulse with a duration of 2 ns. The results are used for construction of a source of high-power ultrawideband pulses with elliptical polarization. The radiation pulses with an effective potential of 300 kV are generated at an amplitude of the bipolar voltage pulse of 200 kV and a repetition rate of 100 Hz.
... Andreev et al. [20], [21] suggested an original technique for determining the position of the radiation center of helical UWB antennas and helical antenna arrays. Radiation center for fixed direction is found from the analysis of rE p (r ) dependence, where E p is the peak electric field value and r is the distance from the transmitting antenna to the point of E p measurements. ...
... Radiation center for fixed direction is found from the analysis of rE p (r ) dependence, where E p is the peak electric field value and r is the distance from the transmitting antenna to the point of E p measurements. If r corresponds to the far-field zone of transmitting antenna, then rE p is usually called the effective potential [20]. The suggested technique, alongside with obvious advantages, has a number of shortcomings. ...
... For the frequency f h = 2 GHz, substitution of the corresponding λ h with reference to (1) gives the value of the far-field boundary equal to 60 cm. Using the estimation r ∼ = 1.5λ l [20], we obtain one more value of the inner boundary of the far-field region r ∼ = 1.15 m for f l . Measurements of the CA1 radiation characteristics were carried out in an anechoic chamber. ...
The paper proposes a method for measuring the position of radiation centers for an ultra-wideband combined antenna in the pulsed mode. The radiation centers for E-and H-planes of the antenna are determined. Antenna rotation in these planes, with respect to an arbitrary axis, results in the time delays (advances) of the recorded receiving pulses for various angles. The purpose of the measurements is to find the rotation axes providing minimum time delays of the radiated pulse registration at the receiving antenna for the largest possible range of observation angles. These rotation axes pass through local areas (radiation centers) in the antenna volume. Simple analytic formulas refining the position of the radiation center from an arbitrary measurement are proposed. In the simulations, a code based on the FDTD method was used. The combined antenna has at least two radiation centers. Radiation center of the H-plane is located at 1/3-1/2 of the antenna length counting from its rear wall, slightly below the antenna’s half-height. Radiation center of the E-plane is located near the aperture plane of the antenna, also slightly below the antenna’s half-height.
... An HP UWB radiation source with elliptical polarization was created at the Institute of High Current Electronics on the basis of a single cylindrical helical antenna, which is excited by a 1-ns-long bipolar pulse [8]. When the amplitude of the generator voltage pulse was ~200 kV and the pulse repetition frequency was 100 Hz, an effective radiation potential of 280 kV was obtained. ...
... The source operated at a pulse repetition rate of 100 Hz. The design of the unipolarpulse generator and the bipolar-pulse (1 ns) shaper were considered in detail in [8]. ...
... A small deflection of the turns of the conical helix (θ 0 ≈ 2.5°) from the cylindrical generatrix allows one to presume the presence of a conditional radiation center. The technique for determining the radiation center for a cylindrical helical antenna was described in [8]. For the radiation direction θ = 0° and the assumption that the radiation center lies on the antenna axis, the dependences of the effective radiation potential (r -r 0 )E p on the distance r were obtained in computations and experiments, which dif-fered in the reference point r 0 . ...
A high-power source of ultrawideband radiation with elliptical polarization was developed on the basis of exciting a conical helical antenna by a bipolar voltage pulse with a length of 1 ns. The antenna parameters were preliminarily estimated using analytical formulas and then optimized via numerical simulation. The results of low-voltage test measurements were compared with the data that were obtained using a program that was developed on the basis of the finite-difference method in the time domain. In high-voltage measurements, the energy efficiency of the radiator was 0.85 and the coefficient of the hodograph ellipticity measured along the antenna axis was 0.9. The effective radiation potential of the source at an amplitude of bipolar voltage pulses of 190 kV was 270 kV, while the efficiency with respect to the peak field strength was 1.35. The high-power source of ultrawideband radiation operated at a pulse repetition frequency of 100 Hz.
... Such high-power UWB sources include helical antennas and radiate electromagnetic pulses with elliptical polarization. 7,8 The electric-field vector hodograph is a closed curve that can be inscribed in an ellipse. The axial ratio of radiation is determined by the ratio of the axes of this ellipse. ...
To measure simultaneously two orthogonal components of the electromagnetic field of nano- and subnano-second duration, an antenna array has been developed. The antenna elements of the array are the crossed dipoles of dimension 5 × 5 cm. The arms of the dipoles are connected to the active four-pole devices to compensate the frequency response variations of a short dipole in the frequency band ranging from 0.4 to 4 GHz. The dipoles have superimposed phase centers allowing measuring the polarization structure of the field in different directions. The developed antenna array is the linear one containing four elements. The pattern maximum position is controlled by means of the switched ultrawideband true time delay lines. Discrete steering in seven directions in the range from −40° to +40° has been realized. The error at setting the pattern maximum position is less than 4°. The isolation of the polarization exceeds 29 dB in the direction orthogonal to the array axis and in the whole steering range it exceeds 23 dB. Measurement results of the polarization structure of radiated and scattered pulses with different polarization are presented as well.
