Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array

Definitions

• the invention is directed to network antennas, and more particularly to so-called active network antennas.
• the network antennas consist of identical radiating elements (or radiating sources).
• the sources are equidistant. Moreover, these sources are powered with the same voltage value.
• one applies to the set of radiating sources a uniform law of weighting. This law leads to obtaining a radiation pattern having high secondary lobes. It is recalled that a radiation pattern corresponds to the Fourier transform of the illumination law of the grating antenna which itself reflects the distribution of the light power of the antenna at different locations around the antenna.
• An optimal law of illumination has regular growth between each end of the network antenna and its center.
• the optimum of the light power is reached around the center of the linear array antenna.
• the presence of secondary lobes of high amplitude in the radiation pattern of the antenna studied corresponds to a law of illumination far removed from an optimal law.
• a so-called active network antenna comprises in its architecture a distributed amplification, that is to say that radiofrequency amplification elements are positioned between the entry point of the network antenna and the radiating elements constituting said network antenna.
• These amplification elements are generally modules that can be used both in reception and in transmission. They sometimes include phase shift elements to point the beam emitted by the network antenna in directions other than normal to the network antenna.
• the power that can be delivered by the aforementioned modules is limited by the technology. It can not exceed a certain level related to the saturation point of the amplification element.
• the radiated power is limited by the sum of the powers delivered at the outputs of the radiofrequency amplification elements. At a given number of radio frequency amplification elements, it is preferable that these elements operate with a maximum output power, that is to say at saturation.
• the output power of the modules is also identical.
• the network antenna is cumbersome; it is necessary to add an additional channel to implant the network of radiating elements forming the antenna in question; the overall architecture of the network antenna is complexified; its mass and its cost of manufacture increase.
• Another known technique for weighting the amplitude of the power radiated by the antenna is to form sub-networks of radiating elements.
• the radiating elements are grouped in block, each block comprising more or fewer radiating elements.
• Each of these sub-networks is powered via an amplifier, all the amplifiers used within the network antenna being identical.
• the number of radiating elements in each sub-network varies according to the average power that we want the element radiating emanates in the case where the antenna operates in emission. Indeed, as each sub-network is connected to the same amplifier, the same voltage value is delivered to each sub-network. Consequently, the more radiating elements in the sub-network, the lower the power radiated by each of these elements.
• the law of illumination obtained with this type of network antenna comprises steps or slots. For example, it may be low on a first portion of the antenna, move to a maximum value on a second portion of the antenna and then return to a low value on a last portion of the antenna.
• This law of illumination implies a rise of the secondary lobes, which is particularly harmful for small network antennas.
• the invention aims in particular to provide a solution to these problems.
• An object of the invention is to propose a network antenna, in particular an active array antenna having a desired illumination law, in other words an optimal illumination law for the use made of the considered network antenna.
• a network antenna comprising radiating elements distributed in sub-networks, the sub-networks being fed via substantially identical amplifiers operating at the same level as the transmission.
• the radiating elements of the same subarray are non-uniformly distributed in space, the distance between two adjacent radiating elements being a function of the desired illumination law for said network antenna. and technical characteristics of subnets.
• the difference between two radiating elements is proportional to the wavelength of the signal emitted by said network antenna.
• the radiating elements are distributed according to the desired law while taking into account the technical characteristics of the sub-networks. This is a spatial weighting of the power emitted or received by the network antenna without modifying the power delivered by the amplifiers used for feeding the radiating elements.
• a technical characteristic of a subnetwork may be the number of radiating elements it has.
• the sub-networks located at the center of the network antenna have fewer radiating elements than the sub-networks at its ends.
• the position of a radiating element of rank i within said array antenna can be determined so that the power density of said radiating element of rank i is substantially equal to the density power of a radiating element of rank i also incorporated within a network antenna having a uniform distribution of its radiating elements, and whose power transmitted or received by each radiating element corresponds to the desired illumination law.
• the radiating elements can be arranged linearly.
• the sub-networks can be distributed in two orthogonal directions.
• FIG. 1 illustrates an illumination law of an active type network antenna according to the invention
• FIG. 2 represents an example of a radiation pattern of a network antenna according to the invention.
• the upper part of FIG. 1 represents an example of an illumination law of an antenna array ANT represented on the lower part, when the latter operates in transmission.
• the law of illumination corresponds to the variation of the average power Pi, radiated by the different radiating elements of a network antenna according to
• This variation is therefore a function of a distance (here in meters, m).
• the illumination law represented passes from a very low value Pmin for the radiating element situated at the first end of the array antenna, to a maximum value Pmax at the center of the antenna, then goes back to the low value Pmin at the second end of the ANT network antenna.
• the evolution from the minimum value Pmin to the maximum value Pmax and vice versa is gradual.
• SR1 and SR4 arranged at the ends of the network antenna ANT each comprise four radiating elements, while the two subarrays of the center SR2 and SR3 respectively comprise two radiating elements.
• each subnet SR1, SR2, SR3 and SR4 has its own spatial distribution of ELT radiating elements that it incorporates.
• the general appearance of this spatial distribution internally to the subnetworks results in radiating elements narrower in the center of the ANT network antenna than at its ends and, in each subnetwork, narrower as one closer to the center of the ANT antenna.
• This distribution makes it possible to obtain the illumination law represented on the upper part of FIG. 1.
• Each sub-network SR1, SR2, SR3 and SR4 is supplied via a radio-frequency amplifier, respectively referenced as AMP1, AMP2, AMP3 and AMP4. connected to the ENT input of the ANT network antenna. These are able to function both during transmission and when receiving a signal from the network antenna ANT.
• the different elements are coupled to each other via an electrical path CH forming an adder when the antenna ANT network
• Each amplifier AMP1, AMP2, AMP3 and AMP4 delivers the same voltage value to the subnet to which it is connected, namely its saturation value.
• the ANT network antenna Due to its subnetwork architecture, the ANT network antenna performs block weighting on the radiated power of its ELT radiators. To this is added a spatial distribution within each sub-network SR1, SR2, SR3 and SR4. Therefore, when the network antenna ANT operates in transmission, the local power density radiated (that is to say the power radiated per unit length, for example the meter, around the radiating element considered) by a radiating element ELT is function:
• the ELT radiating elements belonging to a zone of the ANT network antenna, where these antennas are narrower have a greater weight than the other elements. More precisely, the position of each radiating element is calculated by considering the power density provided by an integrated radiating element within a passive network antenna.
• a passive network antenna unlike an active network antenna, has no amplifier downstream of its radiating elements, which are in turn distributed regularly.
• - Pi P 0 / Ni such that P 0 is the power supplied by the amplifier connected to the radiating element of rank i and Ni is the number of elements within the sub-network considered, and - Pondj is the power desired equivalent, corresponding to the application of the desired weighting law opposite the position corresponding to the element i of a network antenna whose radiating elements are evenly distributed.
• Optimization can be performed, particularly at the locations of coupler type changes, i.e. at the junctions between two subnetworks. This optimization makes it possible to counter parasitic cleavages between two radiating elements, in particular between two radiating elements belonging to two adjacent ends of two distinct subnetworks. This optimization can be likened to a smoothing of the transmitted power (in the case of a transmission).
• FIG. 2 An example of a radiation pattern obtained with a network antenna according to the invention is shown in FIG. 2.
• the first secondary lobes LS are located approximately 22 dB below the main lobe LP.
• the network antenna can be linear as for the example described above, but also be in two dimensions.
• the position of the radiating elements is then defined in two orthogonal directions on the surface of the antenna.
• the antenna can be considered as stacking (i.e., side-by-side mounting) of sub-network and space-weighted linear arrays in each sub-network as described above, or
• the amplifiers are connected via dividers to two-dimensional sub-networks of radiating elements; in this case, it is considered a sub-surface area cutout and an adjustment of the position of the sources according to the two orthogonal directions on the surface of the network antenna.

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• Variable-Direction Aerials And Aerial Arrays (AREA)

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• 2007
  • 2007-12-21 FR FR0709032A patent/FR2925770B1/fr active Active
• 2008
  • 2008-12-19 US US12/809,605 patent/US20110012804A1/en not_active Abandoned
  • 2008-12-19 WO PCT/EP2008/068111 patent/WO2009083513A1/fr active Application Filing
  • 2008-12-19 EP EP08869041A patent/EP2223388A1/de not_active Withdrawn

Non-Patent Citations (1)

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