RU223140U1 - WIDEBAND DUAL POLARIZATION LOW PROFILE X-BAND ANTENNA WITH CAPACITIVE FEED - Google Patents

Abstract

The utility model relates to low-profile antennas that can be used in transmit-receive antenna devices of radio engineering systems to create phased array antennas for ultra-short pulse (USP) and ultra-wideband (UWB) radar with full-polarization modulation. The main goal of the proposed utility model is to expand the operating frequency band of the prototype. This model, under the conditions found in practice, allows one to achieve a technical effect: to expand the operating frequency band by 2.8 times. The technical effect is achieved by compensating for inductive impedance and introducing a dielectric on the power pin, while the pin and the emitter form a capacitor through which the emitter is excited. 4 ill.

Description

The utility model relates to low-profile antennas, in particular to the technological equipment of broadband antennas that can be used in receiving, transmitting and transceiving antenna devices of radio engineering systems for various purposes, in particular for creating phased array antennas for ultra-short pulse (USP) and ultra-wideband (UWB) radar with full polarization modulation.

The areas of SRS and UWB radar that have been developing in recent decades require the creation of effective small-sized antenna systems. When using the full-polarization modulation method in small-sized SRS locators, the antenna system must provide control of all types of polarization in order to obtain maximum information about the located object.

The best option is a microstrip antenna, but it does not meet the broadband requirements, since it has an operating bandwidth of only a few percent. For use in SRS locators, the relative frequency range must be at least 15%. An antenna with a center frequency of 10 GHz will have an operating range of 1.5 GHz.

Many works are devoted to expanding the operating range of planar antennas, see, for example, [1]. All of them, as a rule, come down to a deterioration in the quality factor of the antenna, which is implemented in three well-known options:

1. Increasing the thickness of the dielectric. As a rule, the thickness is in the range of 0.07÷0.2λ. Reducing the ratio leads to a narrowing of the working band;

2. Reducing the dielectric constant of the substrate (ε _r );

3. Using passive additional emitters. Creating multilayer antennas with the addition of additional passive radiators greatly complicates the antenna design.

For large dielectric thickness, the input impedance is always inductive. Therefore, by using a thick substrate and probe feeding, which introduces additional inductance, to obtain a wide bandwidth, this inductance must be compensated.

A number of studies have shown that another way to expand the operating frequency band of small-sized planar antennas is to use weak capacitive coupling between the feed feeder and the emitter.

Capacitance is realized either by the physical addition of a lumped capacitor or by structural elements. One of such constructions is shown in [2].

The antenna shown in [3] p. 119 was taken as a prototype of a capacitively fed antenna.

The capacitance is made in the form of an additional printed circuit board, which is placed on the upper conductor of the planar antenna. The drive pin passes through the planar antenna substrate and the sub-circuit board substrate and is in contact with its top conductor. There is no contact with the top conductor of the planar antenna. Thus, it turns out that the exciting pin is connected to the upper conductor through a capacitor, which is formed by the conductors of the additional printed circuit board. Such designs are applicable at relatively low frequencies; at frequencies in the X range, due to the small dimensions of the elements, the implementation of such a design is difficult.

According to this utility model, a simple, technologically advanced low-profile antenna is proposed, capable of operating on linear and circular polarizations with a working bandwidth of 20%, which does not have the disadvantages inherent in previous designs.

The antenna contains a brass screen (1) 0.3 mm thick, on which a dielectric plate (2) with ε _r = 1.05 is installed, on the other surface of which there is a square-shaped radiating brass plate (3), the dimensions of which are smaller than the dimensions of the screen, and can be in the range of 0.4÷0.6λ.

Two power pins (4) from the power feeders (5) pass through the screen, dielectric plate and emitter. A special feature of this antenna is that the feeding pins and the radiating element are separated by a dielectric (6) and have no galvanic contact. The connection points of the conductors to the strip emitter are located at the same distance from the center of the square emitter at an angle of 90°, and the distances from its center correspond to the requirement of matching the transmission lines with the planar antenna. The impedance changes from zero at the center to resistance at the edge something like this:

where R _i is the input resistance, R _e is the input resistance at the edge, x is the distance from the center of the plate, L is the height of the plate. The location of the feeding coaxial does not significantly affect the resonant frequency. The point at which microwave energy is supplied at a given input resistance can be found from the formula:

Each pin is connected to its own transceiver using a feeder. The presence of two pins and two feeders makes it possible to excite two orthogonal polarizations, and when creating a phase shift between them, circular and elliptical polarizations. Phase shifts can be generated by the control circuits of transceivers.

In order to compensate for the inductive impedance, a dielectric is introduced on the supply pin, while the pin and the emitter form a capacitor, through which the emitter is excited. The central core of the RK50-2-23 cable together with fluoroplastic insulation is used as a probe.

In fig. Figure 1 shows a section of the antenna module, where number (1) indicates the base of the antenna module (screen), and number (2) the dielectric substrate. The height of the substrate in this version is 0.08λ, determined by the specified dimensions. Below the number (3) is a square radiating element, which is smaller than the size of the screen. The dimensions of the emitter can be in the range of 0.4÷0.6λ.

The emitter is powered at two power points by pins (4) from feeders (5), located between the center and edge of the emitter and creating orthogonally located electric field strength vectors, while each of the microwave inputs is connected through a microwave connector to the corresponding input of the transceiver. The power pins and the radiating element are separated by a dielectric (6).

Studies were carried out on the parameters of the antenna with a galvanic connection of the coaxial line and the emitter, as well as with capacitive power supply through the coaxial line insulator by modeling the antennas in the electrodynamic modeling program HFSS v. 19. The dependence of the standing wave ratio of an antenna module with galvanic coupling on frequency is shown in Fig. 2. The results of modeling the dependence of the standing wave ratio of a capacitively coupled antenna module on frequency are shown in Fig. 3.

Comparison of antenna bandwidth at SWR=2 level showed:

- the antenna with galvanic coupling had a bandwidth of 1.44 GHz;

- the antenna with capacitive feeding had a bandwidth of 4.05 GHz, which is 2.8 times greater.

The layout of a broadband low-profile dual-polarization X-band antenna with capacitive power supply is shown in Fig. 4.

BIBLIOGRAPHY

1. Los V.F. Microstrip and dielectric resonator antennas, CAD models: methods of mathematical modeling / Edited by L.D. Bakhrakha, - M.; IPRZHR, 2002. - 96 p.

2. A.I. Semenikhin, D.V. Semenikhin, S.N. Sergeev, S.N. Nosakov Broadband compact microstrip antennas with capacitive microstrip power supply, Southern Federal University. Technical science.

3. Bankov S.E. Antennas for satellite navigators. - M.: Pero Publishing House, 2014. - 693 p.

Claims (1)

Wideband low-profile dual-polarization X-band antenna with capacitive feeding, characterized by containing a 0.3 mm thick brass screen on which a dielectric plate of thickness , with dielectric constant , on the other surface of which there is a square-shaped radiating brass plate, the dimensions of which are smaller than the screen dimensions and are within , two power pins pass through the screen, dielectric plate and emitter, located at the same distance from the center of the square emitter at an angle of 90°, which are galvanically isolated from the radiating element due to separation by a dielectric, creating orthogonally located electric field strength vectors, with each of the inputs through the microwave connector it is connected to the corresponding input of the transceiver through the power feeders.