Patent Application
20120086608
This application claims the priority benefit of French Patent Application Number 10-58110, filed Oct. 6, 2010, entitled “Antenna array for transmission/reception device for signals with a wavelength of the microwave, millimetre or terahertz type,” which is hereby incorporated by reference to the maximum extent allowable by law.
The invention relates to the transmission of signals with a wavelength of the microwave, millimeter and terahertz type whose frequencies go respectively from 300 MHz to 30 GHz, from 30 GHz to 300 GHZ and from 300 GHz to 3 THz and, more particularly, to antennas adapted to such transmissions.
The invention may advantageously be applied, but is not limited to, wireless electronic systems capable of exchanging such signals with microwaves, millimeter and terahertz wavelengths.
The HDMI standard is a wired video data transmission standard. The data rates are very high. In order to obtain such a wireless transmission (W-HDMI), the use of a 60 GHz frequency is proposed with a very high data rate (between 3 and 6 Gb/s) and over distances from 3 to 10 meters between two transmitters/receivers for which the nature of the path of the waves between these two elements can be direct (LOS or Line-of-Sight) or indirect (NLOS or Non-Line-of-Sight) using the acronyms that are well known to those skilled in the art. An antenna or an antenna array must then be used whose radiation pattern in transmission and reception is steerable and a system is needed with a high wireless transmission gain (or “air link gain” according to a term well known to those skilled in the art).
There are then two possible alternatives for the implementation of this system. A first alternative aims to use a power amplifier with a high output power connected to an antenna or antenna array having a moderate gain. This then leads to a high power consumption. Another alternative aims to use a power amplifier with a moderate output power connected to an antenna or antenna array having a high gain. This then leads to a reduced power consumption of the system but the antenna or the antenna array generally requires additional external devices (for example a lens) in order to achieve a high gain.
With an antenna array, it is possible to obtain an electronic pointing of the array in one direction by varying the phase and the amplitude of each of the signals sent to and/or received from the antennas of the array. Indeed, depending on the various phase shifts, the direction of the radiation pattern of the antenna array can be adjusted. Moreover, in a given direction, a higher gain can be obtained than with a single omni-directional antenna.
For the elements of the antenna array, planar antennas or non-planar antennas may be used. The literature provides exemplary embodiments of antennas.
Thus, the publication entitled “High-Gain Yagi-Uda Antennas for Milimeter-Wave Switched-Beam Systems”, by Ramadan A. Alhalabi and Gabriel M. Rebeiz in IEEE TRANSACTIONS ON ANTENNA AND PROPAGATION, VOL. 57, NO. 11, NOVEMBER 2009, describes a high-efficiency power supply for an antenna known as a Yagi Uda antenna for millimeter wavelengths using a microstrip system. This antenna is constructed on either side of a teflon substrate which allows the passage from a symmetric transmission line (antenna) to an asymmetric transmission line (microstrip). A gain of 9-11 dB is thus obtained for frequencies in the range 22-26 GHz. When used in an array of two antennas, a gain of 11.5-13 dB is obtained for the frequencies 22-25 GHz. A high radiation efficiency is obtained.
The publication entitled “On-Chip Antennas for 60-GHz Radios in Silicon Technology” by Y. P. Zhang, M. Sun, and L. H. Guo in IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 7, JULY 2005, describes a compact and efficient antenna for 60 GHz radio waves. This antenna is fabricated on a silicon substrate with a low resistivity of 10 Ω.cm. Two types of antennas have been used, namely an antenna of the Yagi-Uda type and an antenna referred to as an inverted-F antenna. The results obtained are respectively the following: for the inverted-F antenna, insertion losses of 32 dB and a gain of −19 dBi at 61 GHz, and for the Yagi-Uda antenna, insertion losses of 6.75 dB and a gain of −12.5 dBi at 65 GHz (with dBi a unit well known to those skilled in the art representing in dB the gain of an antenna with respect to an isotropic aerial, in other words an antenna which is capable of radiating or of also receiving in every direction and for every polarization).
The publication entitled “60 GHz Antennas in HTCC and Glass Technology” by J. Lanteri, L. Dussopt, R. Pilard, D. Gloria, S. Yamamoto, A. Cathelin, H. Hezzeddine from EuCAP 2010, describes an antenna constructed on glass and connected to a ceramic module using the ‘flip-chip’ technique. An antenna array comprising two antennas such as described hereinabove has also been fabricated. The results obtained are the following: for the single antenna, insertion losses less than 10 dB and a gain of 6-7 dBi over a bandwidth at −10 dB of 7 GHz and, for the antenna array, a gain of 7-8 dBi over a bandwidth at −10 dB of 3 GHz.
When an antenna array using a single type of antenna is employed, for example antennas of the planar type, the radiation pattern of the array can be degraded for large pointing angles with respect to the normal to the plane formed by the antenna array. This is notably the case when the electronically pointed directions make a large angle θ(theta) in the plane of the electric field with the normal to the plane of the antenna, in the radiating direction.
The planar antennas E1, E2, E3, E4 are identical and a more detailed representation is shown at the bottom of
The curve C1 represents the radiation pattern of one of the elements E1, E2, E3 or E4 as a function of the orientation of the electromagnetic waves to the normal from the elements E1, E2, E3 or E4.
The curve C2 represents the theoretical radiation pattern for the antenna array as a function of the orientation of the electromagnetic waves in the plane of the electric field. This pattern is determined by adding to the curve C1 the value: “10 log (N)” for N elements, in other words 10 log (4) with 4 elements E1 . . . E4. The notation log represents the logarithmic function in base 10.
Each of the curves C3, C4, C5, C6 and C7 illustrates, for a pointing direction making an angle θ (theta) with the normal to the antenna array RE in the plane of the electric field, the radiation pattern as a function of the orientation of the electromagnetic waves. The pointing direction is obtained electronically by applying various phase shifts to each of the signals from the elements E1 . . . E4.
The curve C3 corresponds to the case where no phase shift is applied to the antenna array. In this case, the maximum directivity of the radiation pattern is aligned with the direction normal to the planar antennas. The pointing direction makes an angle θ(theta) equal to 0 with the normal to the antenna array, in other words the pointing direction is in the same direction as the normal to the antenna array, this direction is also known as “azimuth”.
The curve C4 corresponds to the pointing direction making an angle θ (theta) equal to +35° in the plane of the electric field with the normal to the antenna array.
The curve C5 corresponds to the pointing direction making an angle θ(theta) equal to +70° in the plane of the electric field with the normal to the antenna array.
The curve C6 corresponds to the pointing direction making an angle θ(theta) equal to +80° in the plane of the electric field with the normal to the antenna array.
The curve C7 corresponds to the pointing direction making an angle θ(theta) equal to +90° in the plane of the electric field with the normal to the antenna array.
As can be seen, the pattern represented by the curve C3 comprises two side lobes for the orientations “+50°” and “−50°”. These are substantially reduced with respect to the main lobe) (0°).
The pattern represented by the curve C4 comprises a main lobe (+35°) and three side lobes at around the orientations “−10°”, “−45°” and “−85°”. These are also relatively substantially reduced.
The pattern represented by the curve C5 comprises a main lobe (+70°) and three side lobes around the orientations “+10°”, “−20°” and “−70°”. As can be seen, the side lobe along the orientation “−70°” has almost the same gain as the main lobe.
The pattern represented by the curve C6 comprises a main lobe (70°) with three side lobes at around the orientations “15°”, “−15°” and “−70°”. The side lobe along the orientation “−70°” has a gain equal to the main lobe. Moreover, the main lobe is not in the pointing direction but along an orientation making a smaller angle (+70°).
The pattern represented by the curve C7 comprises a main lobe (+70°) and three side lobes around the orientations “+10°”, “−20°” and “−70°”. The side lobe along the orientation “−70°” also has a gain equal to the main lobe. Moreover, the main lobe is not in the pointing direction θ(theta) equal to +90° but in a direction making a smaller angle (+70°).
The following are thus observed for electronically pointed directions making large angles θ(theta) with the normal:
a superposition of the main lobes for pointing directions making angles θ(theta) greater than 70°,
a degradation of the main lobe for pointing angles θ(theta) greater than 45°,
a generation of side lobes with a gain as high as the main lobes for pointing angles θ(theta) greater than 45°.
Several problems can then result: degradation of the aerial transmission gain in the lateral directions, problems of synchronization between the transmitter and the receiver, direction of the transmission not well defined, generation of several paths (due to the side lobes) and appearance of interference effects.
Several conventional techniques exist for reducing (or “tapering” according to a term well known to those skilled in the art), the side lobes in the case of an antenna array.
One of the known techniques (“amplitude tapering” according to a term well known to those skilled in the art) consists in adjusting the amplitude of the signals from each of the antennas. This solution can thus be implemented by an electronic management system. However, it is difficult to control the relative amplitude of each antenna for the numerous orientations of the waves to be transmitted and/or received.
Another solution consists in adjusting the phase of the signals from each of the antennas (“phase tapering” according to a term well known to those skilled in the art). This solution can also be implemented by an electronic management system, but it is very complex to control and may even be incompatible with the pointing techniques using the phase.
Another technique consists in spacing the various antenna elements by non-uniform distances, but the antenna array obtained could then get very large.
According to one aspect, a transmission/reception device for signals having a microwave, millimeter, or terahertz wavelength comprising an antenna array including a first group of first omni-directional antennas and a second group of second directional antennas disposed around the first group of antennas.
Other features and advantages of the invention will become apparent upon examining the detailed description of non-limiting embodiments and their implementations, and the appended drawings in which:
Before addressing the illustrated embodiments in detail, various embodiments and advantageous features thereof will be discussed generally. According to one embodiment, a device is provided that is compatible with an HDMI wireless application, aiming to minimize or to overcome the aforementioned drawbacks while at the same time maintaining an antenna array with reduced size and a system having a reasonable power consumption.
According to one embodiment, such a transmission and reception device is provided whose radiation pattern is not degraded for directions making angles θ of more than 45° in the plane of the electric field. According to another embodiment, such a transmission and reception device is also provided in which the side lobes of the radiation pattern are weak.
According to one aspect, a transmission/reception device for signals having a microwave, millimeter, or terahertz wavelength comprising an antenna array. According to one general feature of this aspect, the antenna array comprises a first group of first omni-directional antennas and a second group of second directional antennas disposed around the first group of antennas.
The pointing with phase-shift does not always allow a satisfactory radiation pattern to be obtained and the use of directional antennas can thus complete the radiation of the omni-directional antennas.
The angle θ between the normal to a first antenna and the maximum directivity of the radiation from a second antenna is preferably high which allows a global radiation pattern of the antenna array to be obtained that is much less degraded than in the prior art, or even not degraded at all.
Thus, according to one embodiment, the angle between the normal to each first antenna and the maximum directivity of the radiation pattern of each second antenna is in the range between 45° and 90°.
The maximum directivity of the radiation pattern along these directions allows the radiation pattern of the first group of the first antennas, which is degraded for pointing directions making an angle greater than 45° with the normal, to be completed. The resulting radiation pattern therefore enables the transmission and the reception of waves having an orientation greater than 45° to the normal.
According to one embodiment, the first group of first antennas is situated in an ovoid-shaped central region and comprises identical first antennas, whose isobarycentres are mutually equidistant. The use of an ovoid shape allows an efficient distribution of the antennas. Furthermore, if the antenna array is centroidal, a radiation pattern having a center of symmetry is obtained. In addition, the use of uniform distances between the isobarycentres of the antennas allows the surface of the antenna array to be minimized for the same antenna gain.
According to one embodiment, the isobarycentres of the first antennas are mutually equidistant by a distance equal to half the wavelength of the signals. According to one embodiment, the isobarycentres of the second antennas are also mutually equidistant. According to one embodiment, the isobarycentres of the first and second antennas are mutually equidistant.
According to one embodiment, the first antennas of the first group all have the same orientation, in other words the same omni-directional radiation pattern. The fabrication of the antenna array is then simpler.
According to one embodiment, the second group of antennas is situated in a ring around the central region and comprises second identical antennas, the maximum directivity of the radiation pattern of each second antenna being oriented towards the outside of the ring with respect to the central region.
According to one embodiment, the maximum directivity of the radiation pattern of each second antenna is oriented along a radius of the said ring. The use of a radiation pattern in the direction of the radius of the ring around the ovoid region allows optimum distribution of the various directions in which the directional antennas point.
According to one embodiment, the device also comprises control means capable of controlling means configured for selectively disabling at least one second antenna and its active part.
A part of the directional antennas is not useful when the direction of the wave to be transmitted or received does not correspond to their radiation pattern. It is therefore advantageous to be able to disable some of these directional antennas and the active elements of the circuit connected to these antennas in order to reduce the power consumption.
According to one embodiment, the control means are furthermore capable of controlling phase-shifting means configured for applying phase-shifts to the signals from the antennas of the first group and/or to the signals from the antennas of the second group. The maximum directivity of the radiation pattern of the antenna array is therefore adjustable.
According to one embodiment, the signals are situated in a band of frequencies around 60 GHz.
According to another aspect, a wireless communications device is provided, comprising a transmission/reception device such as described hereinabove.
Turning now to the specific illustrated embodiments,
In this non-limiting example, the array is substantially planar and centroidal.
The directional antennas, which are all identical, are disposed around the omni-directional antennas, more precisely in a ring S2 around the central region S1.
Each of the antennas is represented schematically by a rectangle in the case of an omni-directional antenna and by an arrow in the case of a directional antenna. As can be seen at the bottom of
The grid-lines illustrated in
The radiation pattern of the first group of first antennas A11-A15 is similar to that which was illustrated for 4 planar antennas in
The radiation pattern of the directional antennas is represented by the arrow which also indicates the maximum directivity of the radiation pattern. As can be seen, for the antenna A26, this direction is preferably oriented along a radius R of the ring. The maximum directivity of the radiation pattern (DR) of the second antennas, in this example, lies in a plane that is slightly inclined with respect to the plane of the antenna array, in other words the angle θ(theta) between the normal to the planar antennas and the maximum directivity of the radiation pattern DR is about 90°. However, this value is non-limiting and the angle between the normal and the maximum directivity can be situated in the range 45°-90°. In addition, the pattern DR of each of the directional antennas comprises for example a first main lobe and two side lobes having a lower gain.
In other words, a second group of antennas is used that comprises directional antennas whose maximum directivity of the radiation pattern without phase-shift points in directions making a large angle, for example in the range between 45° and 90°, with the normal to the first group of antennas. Thus, pointing in these directions with the first group of antennas is no longer necessary and the drawbacks that have been mentioned relating to a group of planar antennas pointing in these directions are eliminated. The first planar antennas continue to point electronically in the directions that may entail no degradation of the radiation pattern. An array with an electronically steerable radiation pattern is thus obtained which is completed for the extreme orientations by the directional antennas.
Furthermore, by using directional antennas whose maximum directivity of the radiation pattern without phase-shift points in directions oriented along radii, all the orientations can be reached and a hemispherical radiation pattern is approximated for the whole antenna array.
Each antenna (A11 . . . A15, A21 . . . A28) is capable of transmitting and/or receiving a signal SP of microwave, millimeter or terahertz wavelength whose frequency goes from 300 MHz to 3 THz. For each antenna (A11 . . . A15, A21 . . . A28), the device DIS comprises a transmission channel and a reception channel between means for processing the signal received or transmitted MDTSER and the corresponding antenna. The means MDTSER notably comprise mixers, local oscillators, and analogue-digital and digital-analogue converters and one or more processors in baseband.
The transmission channel notably comprises, phase-shifting means MDD configured for shifting the phase of the signal to be transmitted SE and a power amplifier PA configured for amplifying the signal prior to its transmission.
The reception channel notably comprises a low-noise amplifier LNA, phase-shifting means MDD configured for applying a phase-shift to the signal following its amplification in such a manner as to obtain the received signal SR.
In this figure, a common antenna is shown for the transmission channel and the reception channel. In this case, a selector switch SW is required. However, it is also possible to provide an antenna dedicated to the transmission and another antenna dedicated to the reception.
All these means are controlled by control means MC notably capable of controlling the phase-shift applied by the means MDD to each of the signals to be transmitted or received by the antennas A11 . . . A28 in such a manner as to point electronically in a desired direction. For example, for each of the directions in which the antenna points, the various phase-shifts are fixed. According to one variant, for one pointing direction, each of the phase-shifts can vary around a fixed value.
The means MC are also capable of enabling or not each of the antennas A21 . . . A28 and the active part that supplies it via the disabling means MDES. It is indeed advantageous, for reasons of power consumption, to be able to disable a directive antenna and its active part, notably the amplifiers PA and/or LNA, which are not useful when the pointing direction is different from the maximum directivity of the radiation pattern of the directive antenna.
In
In
In
It goes without saying that other variant embodiments are possible. All the means
PA, LNA, MDTSER, MDD, MDES are conventional structures and known per se.
The device DIS can be integrated into a wireless communications device APP. The device APP may itself be integrated into a video and/or audio broadcasting system. For example, the device APP is advantageously integrated into a television set thus allowing the existing HDMI cables to be replaced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-58110 | Oct 2010 | FR | national |
