RU183448U1 - PRINTED ANTENNA OF THE RADIO MODULE - Google Patents

Abstract

The invention relates to antenna devices for transmitting and receiving various types of information in the field of wireless communication and can be used in wireless networks for accessing the Internet, as well as in wireless telemetry data transmission devices operating at VHF frequencies, preferably 868 MHz. The antenna contains a dielectric panel including a ground plane and a meander-shaped strip conductor located on its other plane, forming a dipole antenna. Moreover, the antenna is made asymmetric and single-element with a strip conductor in the form of a single periodic microstrip trace line in the form of a meander structure, with turns alternating with equal pitch, forming a package of turns. In this case, the total length of the trace line is close to half the wavelength of the central operating frequency of the working radiation band of the antenna. The technical result consists in reducing the overall dimensions of the antenna. 5 C.p. f-ls, 5 ill.

Description

Purpose and scope

The present technical solution relates to antenna devices for transmitting and receiving various types of information in the field of wireless communication and can be used in wireless networks for accessing the Internet, as well as in wireless telemetry data transmission devices operating at VHF frequencies, preferably 868 MHz .

State of the art

Wireless systems are firmly rooted in our lives. In everyday life, these are various multimedia systems, control devices, wireless interfaces, and various monitoring systems. In industry, data collection systems, automated and automatic control systems (from lighting systems to building automation and their complexes). In transport - cargo tracking, monitoring of traffic parameters, etc. In addition, the scope of wireless devices and systems based on them is constantly growing both qualitatively (new areas are added) and quantitatively (the number of devices using the radio channel is expanding, the density of nodes and networks is increasing). This forces wireless chip manufacturers and system and software developers to constantly look for new solutions to the problems of node and system interaction, network compatibility, and minimize hardware size while maintaining a high level of performance.

In wireless telemetry data transmission devices operating at VHF frequencies, the antenna is a key element in determining size and performance.

In this regard, there is a problem of creating antennas adapted for placement in a compact housing of a wireless transmission device, the performance of which, such as efficiency, energy level, bandwidth, radiation pattern, etc., would ensure reliable and high-quality communication.

Simple and reliable designs of whip and helical antennas are known which, for example, are equipped with mobile radiotelephones. A significant disadvantage of antennas of such designs are large dimensions. Spiral antennas are made wound on a dielectric frame, therefore, in comparison with whip antennas, they have a shorter geometric length. To reduce the geometric length of the pin antennas, they are equipped with “shortening” means, for example, inductors (Kamenetsky MV, Zaikin VA Radiotelephones / St. Petersburg, “Science and Technology”, 2000, pp. 8-10).

From the prior art, a USB modem device with a rotating (directional) antenna and a retractable USB connector is known (US 7530823 B1, published May 12, 2009). The disadvantages of this technical solution include restrictions on reducing the overall characteristics of the structure, the impossibility of moving this antenna into the area of more reliable radio signal reception, and the limited location of the final client equipment; the need to adjust, adjust the rotatable (directional) antenna to achieve the most useful result; weakly pronounced directional action of a rotating (directional) antenna and, as a result, a small distance at which the signal is received stably. Thus, this solution does not provide a solution to the problem of minimizing the overall characteristics of the device while maintaining consistently high performance characteristics of the wireless data transmission device, providing reliable and high-quality communication.

The prior art also knows the use of microstrip antenna devices (printed antennas) in wireless communication devices. The appearance of microstrip antenna devices (MPA) is caused by the need for light, thin, conformal and cheap antenna devices that can be placed on any surface with a minimum area. At present, a significant number of samples of microstrip single-element antennas have been created and patented. The possibility of creating antennas with linear and circular polarization, as well as the possibility of creating dual-frequency antennas, has been revealed. Any microstrip antenna device is a dielectric sheet of small thickness with a thin copper coating applied on both sides, as a rule. On one side are made a radiating element, power circuits, control and coordination. The other metal side of the antenna board serves as a screen. Resonator-type printed emitters built on the basis of an asymmetric strip line are widely used. Another type of microstrip antenna in printed design is vibrators of various configurations and slots cut in the metal wall of the strip transmission line of a symmetrical type. The difference between these antennas are flat ribbon spirals and curved emitters.

Printed antennas based on asymmetrical strip conductors, which have also found application in the construction of wireless data transmission devices, are also known from the prior art. The main element of such antennas is a flat emitter located on one side of the dielectric plate, the other, fully metallized side of which serves as a screen, which allows you to create a one-sided radiation pattern (US patent No. 5323168, CL H01Q 1/38, publ. 1994). The disadvantage of printed antennas of this design is due to the dependence of their efficiency on the thickness of the dielectric plate: the antenna efficiency increases with increasing thickness of the dielectric, which leads to an increase in the weight and dimensions of the antenna, and, consequently, the data transmission device.

Also, examples of integrated antennas are known from the prior art, the printing of which is carried out on dielectric substrates together with electronic components. Integration of radio frequency elements and components of digital electronics with transceiver antennas into a single module reduces the number of wires and connectors, which reduces the cost of the device. However, such designs have a significant drawback, namely spurious emissions from electronic components (oscillators) located on the printed circuit board, which can significantly reduce the communication range.

An external dipole antenna does not have such a disadvantage, since it is isolated from the elements of the control electronics. However, such antennas for the 868 MHz range have a length of about 15 cm, which significantly limits their scope.

Modern telemetry devices have many different electronic components. The spurious emissions of these components near the path of the radio frequency cable reduce the dynamic range of the communication system. In fact, measurements of electromagnetic compatibility show that such interference can exceed the noise level in a communication system by more than 20 dB.

As a rule, the influence of spurious components on the cable can be minimized by using a special passive electronic device, such as a balanced transformer (balun), to balance the impedances between the antenna and the RF circuit. However, such a balloon with a printed circuit board has a linear size equal to a quarter of the wavelength, and therefore, as a rule, it is too large for most telemetry devices operating at 868 MHz. Therefore, developers are forced to use antennas without a balloon. (A. Kalachev “Building a Wireless Channel Based on Texas Instruments Components, Components and Technologies, No. 4, 2012)

The above problem is taken into account in the antenna design, the solution of which is disclosed in US Pat. No. 8,063,845, which describes the solution of an antenna comprising a dielectric panel including a ground plane and a meander-shaped strip conductor located on its other plane. forming a symmetrical dipole antenna, in particular, intended for its use in the frequency band 315 MHz in automotive applications, such as, for example, keyless entry systems. According to the solution disclosed in the patent, the antenna has primary and secondary antenna tracing lines made in the form of tracks of a strip conductor on a printed circuit board and connected to the control module via a connector. Both tracing lines are made on one side of the circuit board. At the same time, a symmetrical printed meander dipole antenna may additionally include an inductance located between the primary and secondary antenna trace lines, and additional cutting of the trace lines along the edges of the antenna is designed to provide the possibility of additional tuning of the antenna impedance. In turn, to provide additional tuning of the frequency band, the antenna may also contain a resistor. As follows from the description in the patent publication, the primary and secondary antenna trace lines may include 16 vertical paths having a length of approximately 70 mm and a width of approximately 33 mm. The distance between the trace lines is approximately 5 mm. The width of the trace lines, together with additional cutting along the edges, is 54 mm. All trace lines are made of conductive material, such as copper, for example. As the material of the dielectric substrate is preferably used fiberglass brand FR4. The disadvantages of this antenna include the excessively large dimensions of the antenna, limiting the possibility of its use for transmitting telemetry device data, especially with respect to the 868 MHz frequency band, and its integration into surround devices. The need to symmetry the meander portion significantly complicates both the design of the antenna and the technology of its manufacture, while actually doubling the amount of material needed to make the antenna. In addition, the design of both the antenna and the end device is complicated by the presence of a connector, a tuning resistor, and inductance, which must be precision for fine tuning, which further increases the risk of incorrect antenna tuning, thereby reducing the operational characteristics of the device, and complicates the manufacturing process of the antenna and device, including it, increasing it in time. The directivity and consistency of the antenna with the transmitter output are not unattainable, and can even be surpassed. However, this decision, in terms of the essential features, is taken as a prototype.

The essence of the claimed utility model.

The technical task of the utility model, the solution of which the claimed solution is directed, is to offer a simple, compact design of a printed antenna that provides high performance.

The technical result achieved by the claimed utility model consists in expanding the arsenal of known technical means by optimizing the configuration of the printed antenna operating in the frequency band 868 MHz, ensuring the compactness of the antenna and its high operational characteristics.

The specified technical result is achieved by the use of a printed antenna of a radio module containing a dielectric panel, including a ground plane and a meander-shaped strip conductor located on its other plane, forming a dipole antenna, which differs from the prototype in that the antenna is made asymmetric and single-element, with a strip conductor in the form of a single a periodic microstrip trace line in the form of a meander structure, with turns alternating with equal pitch forming a packet of turns, is the total length of the trace line is close to a half wavelength of the central operating frequency of the antenna operating band radiation.

In a preferred embodiment of the claimed utility model, the trace line of the strip conductor is made in the form of alternating in the form of a meander, with an equal pitch of no more than 1.7 mm, U-shaped turns consisting of horizontal and vertical sections, where the antenna length along the packet of turns is 0.038λ , and the length of each vertical section of the coil is 0.026λ, where λ is the wavelength at the central operating frequency of 868 MHz. Moreover, the width of the strip conductor, preferably not less than 0.3 mm and not more than 0.4 mm

In one embodiment, one of the lateral vertical portions of the strip conductor is shortened and mates with a horizontal portion open from the outside to interface with the matching circuit of the amplifier stage of the radio module.

According to the claimed utility model, the dielectric substrate is preferably made of fiberglass, for example, brand FR4, and the strip conductor is made of copper.

Brief Description of the Drawings

The claimed technical solution is illustrated by drawings, where:

figure 1 - antenna of the radio module;

FIG. 2 - antenna location on the radio module board;

figure 3 - radiation pattern of the antenna of the radio module: a) prototype; b) the declared decision;

figure 4 - three-dimensional radiation pattern of the antenna, according to the claimed solution;

5 is a diagram of Wolpert-Smith: a) prototype; b) the declared decision.

It should be noted that the accompanying drawings illustrate only one of the most preferred embodiments of the utility model and cannot be considered as limitations on its content, which may include other possible embodiments.

Utility Model Feasibility Example

As follows from the FIGS. 1 and 2 of the graphical representations of the claimed solution, the printed antenna of the radio module includes a substrate in the form of a dielectric panel 1, made preferably of fiberglass, for example, FR4 grade, preferably 0.8 mm thick, on one side of which a strip conductor 2 is placed, made preferably , from copper, in the form of a printing track with a thickness of 0.035 mm, forming a single periodic microstrip trace line in the form of a meander structure containing, according to the presented embodiment, a set (pa em) of staggered, similar U-shaped windings 3. Each coil comprises a vertical 4 and horizontal 5 portions. At the same time, the turns are arranged equidistantly with an equal pitch H. Together, according to the presented embodiment, the horizontal and vertical sections form 7.5 turns, with a pitch H = 1.7 mm.

According to the claimed utility model, the antenna has overall dimensions in fractions of the wavelength λ at the central operating frequency of the components: L = 0.038λ, where L is the antenna length along the bundle of turns, and W = 0.026 λ, where W is the length of each vertical portion of the turn, and - wavelength. In the presented embodiment, the antenna of the radio module is tuned to the operating frequency of 868 MHz, thus the overall dimensions of the printed antenna according to the presented embodiment are (LxW) - 13x9 mm. Obviously, even with respect to the wavelength, the proposed antenna has a more optimal design compared to the prototype (the ratio LxW of the prototype in fractions of the wavelength is 0.074 λx0.057 λ). Moreover, the length of each of the horizontal sections of the turns of the microstrip trace line of the claimed solution is 1.25 mm, and the vertical, with the exception of one of the side, made shortened, is 9 mm, the width of the strip conductor is preferably selected at least 0.3 mm and no more than 0.4 mm. The optimal length of the shortened side vertical section of the antenna, in particular, depends on the geometry of the ground plane and the operating frequency of the antenna, decreasing with its increase. Obviously, the claimed solution can be applied not only to the 868 MHz operating frequency band presented in the example, but also to other frequencies used in wireless telemetry data receiving devices. In the present embodiment, the width of the strip of the strip conductor is 0.4 mm. Thus, in total, the length of the trace line is approximately half the wavelength, at the operating frequency of 868 MHz. This makes the radiation of the antenna equivalent to the radiation of a half-wave asymmetric dipole antenna.

In the drawing of FIG. Figure 2 shows the location of the antenna on the radio module board. As follows from the presented embodiment, for the signal to the antenna does not require additional connectors and connectors. The coordination of the radio frequency signal with the antenna is ensured by a matching circuit made on reactive elements that compensate for the reactive components of the input impedance of the antenna. Since the total input impedance of this antenna is roughly matched with a resistance of 50 ohms, external matching elements are not required. The value of the antenna input impedance is affected by the geometry of the board ground plane. Therefore, the length of the antenna is adjusted in accordance with the size and shape of the ground layer, for example, by connecting serial and shunt elements at the antenna feed point. They can be used to compensate for the mismatch caused by the plastic case and the presence of other objects near the antenna.

The results of measuring the operating characteristics of the antenna, presented as an example of implementation, showed that the compact overall dimensions of the antenna did not impair its performance.

As shown in the Volpert-Smith diagram (Fig. 5b)), the antenna provides an SWR value within 2 (the reflection coefficient of the antenna does not exceed -10 dB) in the range of 862.8 ... 879.3 MHz. The value of the SWRC at the main operating frequency is 1.4, which indicates a higher degree of coordination with the transmitter with an impedance of 50 Ohms than the antenna of the prototype (Fig. 5a)). A reflection coefficient of less than -10 dB, or an RRC of less than 2, ensures that more than 90% of the available power is supplied to the antenna.

Presented on the graph of FIG. 4, a three-dimensional radiation pattern of the antenna of the radio module, according to the embodiment shown, shows a close to spherical shape, which is achieved as an antenna configuration made in such a way that the current phase distribution in the antenna path is close to linear, and there are no elements introducing phase a shift, which ultimately leads to the absence of side lobes in the radiation pattern, and a more uniform distribution of the antenna field strength. The orientation of the printed antenna of the radio module during measurements is shown in the graph of figure 4.

Shown in the graphs of figa) and 3b), the comparative characteristics of the radiation pattern in the horizontal plane of the prototype and the claimed solution confirm the above conclusions. In comparison with the prototype, the radiation pattern of the claimed solution is close to spherical and is characterized by a low level of non-uniformity of characteristics in the working frequency band, not exceeding 6.1 dB.

A printed antenna according to the claimed utility model can be made by any method known in the art and using a wide variety of known technological equipment and materials for the manufacture of printed circuit boards.

Thus, the presented example of the feasibility of the claimed solution of the utility model shows that the proposed configuration of the printed antenna can significantly reduce the overall dimensions of the structure, while improving the directivity and consistency of the proposed antenna in comparison with the known in the prior art, which allows the use of this solution in miniature wireless devices , with data transmission over significantly long distances. At the same time, the proposed antenna configuration eliminates additional elements, such as connectors, resistors and inductances, which ensure that the antenna parts are balanced and additionally configured in the prototype solution.

In addition, the efficiency of the choice of the form of representation of the antenna in a printed manner allows to ensure

- repeatability of performance in large-scale production;

- no need to use an external antenna;

- reduction of the range of components of the product.

As a result of the integration of all nodes of the radio-transmitting and transmitting device with the antenna into a single module, a synergistic effect is achieved consisting in significantly increased physical integrity and stability of the device, and the configuration of the antenna path used reduces the power loss of the output radio signal, while maintaining the quality of communication.

Claims (6)

1. A printed antenna of a radio module comprising a dielectric panel including a ground plane and a meander-shaped strip conductor located on another plane thereof, forming a dipole antenna, characterized in that the antenna is made asymmetric and single-element, with a strip conductor in the form of a single periodic microstrip trace line in the shape of the meander structure, with turns alternating with equal pitch forming a packet of turns, while the total length of the trace line is close to half the wavelength c ntralnoy operating frequency of the operating band of the antenna. 2. The antenna according to claim 1, characterized in that the trace line of the strip conductor is made in the form of alternating in the form of a meander with an equal pitch of not more than 1.7 mm U-shaped turns, consisting of horizontal and vertical sections, where the length of the antenna along the package of turns is 0,038

, and the length of each vertical section of the coil is 0,026

where

- wavelength at a central operating frequency of 868 MHz. 3. The antenna according to claim 2, characterized in that the width of the strip conductor is not less than 0.2 mm and not more than 0.4 mm. 4. The antenna according to claim 2, characterized in that the lateral vertical section of the strip conductor is made shorter and paired with a horizontal section open from the outside to interface with the matching circuit of the amplifier stage of the radio module. 5. The antenna according to any one of claims 1 to 4, characterized in that the dielectric substrate is made of fiberglass. 6. The antenna according to claim 5, characterized in that the strip conductor is made of copper.

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