D E S C R I P T I O N

Field of Application

The present invention applies to the field of telecommunications, and particularly relates to antennas for receiving and transmitting radio frequency signals.

In greater detail, the present invention refers to an antenna particularly suitable for making UWB radars.

Background

In the field of telecommunications, the transmission technique referred to as UWB, i.e. Ultra WideBand, is known, which is developed to transmit and receive signals using radio frequency pulses having an extremely short time duration and, therefore, a very wide spectrum occupancy. These pulses are represented by a few wave cycles of a radio frequency carrier and, therefore, the frequency spectrum associated with this waveform is extremely wide, i.e. returns ambipolar pulses whose duration is so short that a carrier is not required.

The advantage of this technique is that the shortness of the pulse makes the transmission of the signal not very sensitive to interference due to the reflection of the wave itself.

The bandwidth causes the power spectral density to be very low, by limiting, among other things, interference towards the surrounding applications. Such band, which can reach significant widths, may be obtained with extremely low antenna electrical powers.

Due to these characteristics, this technique is also used in the field of radars.

As is known, radar is a system that uses electromagnetic waves to detect and determine the position, and possibly the speed, of both fixed and moving objects.

Notably, the operation of radar is based on the physical phenomenon of the reflection of electromagnetic radiation when it hits an object, which is larger than the wavelength of the incident radiation.

A relevant feature is that the signal must have excellent directivity, i.e. radars must be characterized by antennas able to radiate the signal in a privileged direction. Such feature of radar devices is necessary in order to discern objects, whether fixed or moving, placed at the same distance from radar. Furthermore, the directivity of the signal allows a large part of the energy to be directed in the selected direction, increasing the maximum detection distance.

Another relevant feature is that the signal must allow the highest possible resolution of the detection and have a limited module and phase dispersion to ensure that the radiated signal coincides as much as possible with the one to be fed to the antenna in order to increase the spatial resolution of the radar.

It is also known that high-resolution radar antennas must be able to ensure the above-mentioned features of the signal over a very high frequency range.

In addition, the need to miniaturize radar antennas so that they may also be used in robotics and / or home automation applications is becoming more and more compelling. This is particularly important in the case of UWB radars, where the size of the antennas is predominant when compared to the other elements of the radar device.

According to the known art, antennas increasingly exploit the production process of the printed circuit board on which the transceiving circuits are made in such a way as to increase integration and compactness. Such process also allows manufacturing costs to be reduced.

However, the results achieved by the known art are not always optimal.

Notably, known antennas for UWB signals do not ensure optimal performance in terms of directivity and impedance matching over such a wide spectrum of frequencies.

Furthermore, typically, the antennas for UWB signals are designed for electromagnetic signals with earth or ground reference, while it is often useful to use differential or phase opposition signals.

In addition, the known art comprises the publication of Lindmark B. titled "A novel dual polarized aperture coupled patch element with a single layer feed network and high isolation", published by the Antennas and Propagation Society as part of the International symposium, 1997. IEEE., 1997 Digest Montreal, Que., Canada 13-18 July 1997, New York, NY, USA, IEEE, US, 13 July 1997, page 2190, and the Patent for Industrial Invention US 2009 121957 A1.

The mentioned documents disclose only antennas comprising slots, which allow the radiating elements to generate a radiating field in phase opposition. Such slots just cross each other without any additional effect.

Presentation of the Invention

The object of the present invention is to overcome at least partially the drawbacks identified above by providing an antenna for UWB signals which allows the directivity of the emitted electromagnetic signal to be maximized.

Another object of the present invention is also to provide an antenna for UWB signals which allows a better impedance matching between the signal generator and the transmission means to be achieved compared to what occurs in the known equivalent devices. Accordingly, an object of the present invention is therefore to reduce the dispersion of the output signal on the antenna in the whole range of the frequencies used.

A further object is to provide an antenna for UWB signals suitable for being used with differential devices, wherein the signal is expressed as the difference in potential between two different terminals fed by phase opposition signals.

Another object is to provide a miniaturized antenna integrated in the printed circuit board on which the transceiving circuits are made, so as to increase its integration, compactness, and reduce manufacturing costs.

Such objects, as well as others that will become more manifest below, are achieved by an antenna according to the following claims, which form an integral part of the present disclosure.

Notably, the antenna is of the PCB type, i.e. made on a printed circuit board. It includes, like the known antennas, at least one ground plane, at least one power supply and radiating elements. To be more precise, according to one aspect of the invention, the radiating elements are at least two.

Advantageously, as a result, the antenna may be used with phase opposition signals.

According to another aspect of the invention, the radiating elements are formed by a foil having a shaped perimeter. Such foil has a central area free of material and also having a shaped perimeter, as well as at least two slots connecting the aforementioned central area to the perimeter of the foil thereof. This way, the latter is divided into portions, each forming a radiating element.

Advantageously, this allows the terminals connected to the metal tracks to be kept separate.

Still advantageously, the slots allow the radiating elements to generate a phase opposition radiating field and, therefore, to operate as coupled microstrip antennas (patch antennas).

According to a further aspect of the invention, the central area has at least one of the dimensions greater than the width of the slots.

Advantageously, the dimensions of the central area are such as to allow the slots to excite it, thereby actually obtaining a further radiating element.

Advantageously, all of this improves the directivity and the impedance matching of the antenna of the invention compared to known equivalent antennas, in particular with UWB signals.

Brief Description of the Drawings

Further features and advantages of the invention will be more evident in light of the detailed description of some of the preferred but not exclusive embodiments of an antenna according to the invention, illustrated by way of non-limiting example with the aid of the accompanying drawings, wherein:

FIG. 1 represents a PCB antenna according to the invention in a schematic view;

FIG. 2 represents a detail of the PCB antenna in FIG. 1 ;

FIG. 3 represents a detail of an alternative embodiment of the antenna of the invention;

FIG. 4 represents a detail of the PCB antenna in FIG. 1. Detailed Description of Some Preferred Embodiments

With reference to the mentioned figures, and especially to Fig. 1 , an antenna 1 according to the invention is described. As can be seen, the antenna 1 is of the PCB type, that is, it is made on a printed circuit board. Such antennas are also called planar antennas.

According to an aspect of the invention, the antenna comprises a ground plane 3, a power supply 4, and two radiating elements 5. Notably, the figure shows that such elements each consist of a corresponding conducting layer and separated from each other by at least one substrate made of a dielectric material.

As far as the power supply 4 is concerned, there are two electrical connection tracks 6, which, through metallized holes 7, connect it to the outputs of a generator or to the input of a radio-frequency or microwave signal receiver.

According to another aspect of the invention, the aforementioned two radiating elements 5 are formed, as can also be seen in the detail of Fig. 2, by a foil 13 having a shaped perimeter 14. According to the embodiment of the invention which is being described, the perimeter 14 is shaped as a quadrangle.

According to a further aspect of the invention, the foil 13 has a shaped central area 15 free of material, as well as two slots 16 connecting the aforementioned central area 15 to the perimeter 14.

This way, advantageously, the foil 13 is divided into portions each forming one of the two radiating elements 5.

Still advantageously, the presence of a pair of radiating elements 5 allows the antenna 1 to be fed with differential signals.

As a result, still advantageously, the slots 16, together with the central area 15, allow the radiating elements 5 to generate a phase opposition radiating field and, therefore, to operate as two coupled microstrip antennas (patch antennas). Besides, this is enhanced by the symmetrical configuration of the radiating elements 5 of the embodiment which is being described.

According to a further aspect of the invention, the central area 15 has at least one of the dimensions greater than the width of the slots 16.

Advantageously, the dimensions of the central area 15 are such as to allow the slots 16 to excite it, thereby actually obtaining a further radiating element.

As a result, generally, the microstrip antenna 1 is advantageously characterized by very small dimensions and low costs, being able to exploit the technologies for making the integrated circuits.

Furthermore, still advantageously, the conformation of the radiating elements 5, the slots 16, and the central area 15 together allow the directivity and the impedance matching of the antenna of the invention to be improved compared to the known equivalent antennas, especially when differential UWB signals are used.

As far as the shaping of the perimeter 14 of the foil 13 is concerned, as said in the embodiment which is being described, it is quadrangular. Obviously, this aspect should not be regarded as limiting for different embodiments of the invention, wherein, for example, the perimeter of the foil is shaped according to other polygonal shapes in accordance with the specific use of the antenna 1 and with the desired directivity and impedance matchings thereof.

For the shaped central area 15, the figures show that it has an elliptical shape. Obviously, even such aspect must not be regarded as limiting for different embodiments of the invention, wherein, for example, the central area is shaped as a polygon or mixed line.

Also in this case, the shape of the central area 15 is in accordance with the specific use of the antenna 1 and with the desired directivity and impedance matchings thereof.

The features of the antenna 1 just mentioned are also influenced, as said, by the slots 16. According to the embodiment which is being described, they are rectilinear. Flowever, it is evident that this embodiment of the slots should not be considered as limiting for the present invention. In fact, according to a different alternative embodiment, which can be seen in Fig. 3, the foil 113 has two slots 116 extending according to a broken line. This does not exclude further alternative embodiments, not shown herein, wherein they identify curved lines, mixed lines, or others. All this is in accordance with the desired directivity and impedance matchings. The numbers of radiating elements, shaped central areas and slots are also all non-limiting features for the present invention, since they can be whatsoever, provided that at least two radiating elements are identified.

Obviously, also the number of connection tracks 6, which feed the radiating elements 5 can be whatsoever according to the number of such radiating elements 5.

According to another aspect of the invention, the end part 20 of the two connection tracks 6, as can be seen in the detail of Fig. 4, consists of shaped flanges 21.

Advantageously, the latter allow the power matching of the antenna 1 to be improved, by introducing a set of parasitic capacitors which are formed between such flanges 21 and the overlying radiating elements 5.

Obviously, this aspect, too, should not be regarded as limiting for different embodiments of the invention, wherein, for example, they are absent, or wherein they take on a different shape from what is visible in figures.

In light of the foregoing, it is understood that the antenna of the invention achieves all the intended objects.

Notably, the antenna of the invention is be particularly suitable for treating electromagnetic signals of the UWB type and allows the directivity of the signals to be maximized over a wide portion of the spectrum, which is higher than that allowed by known antennas.

On closer inspection, the antenna of the invention is particularly suitable for being used with differential signals.

In addition, it allows the impedance matching between the signal generator and the transmission means to be improved so as to reduce the dispersion of the output or input signal to the antenna.

In addition, the invention allows the antenna to be manufactured on a printed circuit board, allowing the overall dimensions of the system to be reduced, with an evident advantage in terms of manufacturing costs.

Finally, the antenna of the invention is particularly suitable for radar applications since the improved directivity allows the detection of targets to be optimized. Furthermore, the increased impedance matching allows the reduction of the dispersion of the output signal on the antenna in the whole range of the frequencies used.

The invention might be subject to many changes and variations, which are all included in the appended claims. All the details may be replaced by other technically equivalent elements, and the materials may be different depending on the needs, without departing from the protection scope of the invention defined by the appended claims.