Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/30—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array
  • H01Q3/34—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means
  • H01Q3/36—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means with variable phase-shifters
  • H01Q3/38—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means with variable phase-shifters the phase-shifters being digital

Definitions

• the present invention relates to electronic scanning and broadband antennas of instantaneous frequency.
• An electronic scanning antenna is an antenna consisting of a network constituted by the juxtaposition of a plurality of elementary radiating sources.
• the M sources are arranged regularly along a main direction X of the antenna and are spaced apart from each other by a step d.
• a distance D (M-1) d thus separates the first source and the same source.
• the orientation of the pointing direction P of the antenna beam is effected by adjusting the delay between the elementary waves emitted or received by the different sources. Indeed, as shown schematically in FIG. 1, this has the consequence of modifying the angle of the wavefront with respect to the main direction X, and thus of modifying the angle of pointing of the beam of the antenna, c that is, the angle between the pointing direction P and a reference direction Z normal to the main direction X of the antenna.
• the delay to be introduced for a given source is related to the desired pointing angle, as well as to the position of the source within the antenna.
• the maximum delay to bring between the first source and the same source is equal to Dsin (0), where ⁇ is the desired pointing angle.
• An electronic scanning antenna is therefore equipped with adjustment means of the delay that must introduce each of the sources of which the antenna is constituted.
• the delay is brought by a phase shift introduced into the transmission or reception signal. from a source to the crossing of a phase-shifter placed just behind this source. This phase shifter is controlled to introduce a suitable phase shift.
• the solution consists in introducing the delay, not in the form of a phase shift, by means of a phase-shifter, but in the form of a path length. additional, by means of a programmable length line, referred to as LLP in the following.
• an N-bit LLP consists of N cascaded controlled switches, each switch for connecting an input terminal to an output terminal by selecting either a direct connection or an indirect connection by a line of length L1 for the first switch, L2 for the second switch ..., LN for the Nth switch.
• the length L1 is called LSB (for "Least Significant Bit” or the least significant bit).
• the length LN 2 N_1 L1 is also called MSB (for "Most Significant Bit”) .
• the lengths that can be generated with an N-bit LLP are all lengths from 0 (when all N switches select a direct connection) to 2LN-L1 (when all N switches select an indirect connection), by LSB steps, let: 0, L1, L2, L2 + L1, L3, L3 + L1, L3 + L2, L3 + L2 + L1 ...
• a line used to make an indirect connection is for example a line segment TEM (for example a coaxial cable segment) or for example still a circuit called "all-pass filter" known to those skilled in the art.
• An LLP has the property of introducing a delay proportional to its length and this whatever the frequency of the signal.
• Lmax D sin (Omax)
• D is a characteristic dimension of the antenna
• Omax the angel of misalignment maximum of the antenna.
• the LLPs to be used in order to adjust the delay of each source to allow the antenna to operate in an extended angular range would thus have a large bulk, in particular because of the large length of the most significant bits.
• LLPs are therefore incompatible with close networking of the sources, in particular in the case of planar array antennas, in which the sources are arranged in two orthogonal directions X and Y.
• LLPs introduce relatively large ohmic losses that increase with the length used. The ohmic losses introduced by the most significant bits are thus too important.
• the solution currently implemented consists of dividing the subnetwork antenna, then to implement for the angular misalignment of the beam, on the one hand, phase shifters at each source of radiant sub-networks and, secondly, a programmable length line at the entrance. each subnet.
• LLPs provide network pointing stability, while phase shifters provide pointing accuracy and lobe quality of the radiation pattern.
• a second cause of degradation of the diagram is related to the use of the concept of phase modulo 2 ⁇ phase-shifters, which, if valid at the central frequency, introduces an error that increases away from this central frequency.
• the third cause of degradation of the diagram is related to sub-network subdivision of the network antenna, which generates a certain geometric periodicity on the errors identified above.
• the invention therefore aims to overcome the aforementioned problems.
• the subject of the invention is an electronic scanning antenna with a wide instantaneous frequency band, comprising a plurality of radiant sources grouped into sub-arrays and delay adjustment means that each source must introduce to point a beam of the antenna at a required pointing angle, the adjustment means comprising, on the one hand, a first delay adjustment device at each of the sources of a sub-array and, on the other hand, on the one hand, a second delay adjustment device at each of the antenna subarrays, each second adjustment device being constituted by a second programmable length line, characterized in that each first adjustment device is consisting of a first programmable length line.
• the invention has one or more of the following characteristics, taken in isolation or in any technically possible combination:
• a programmable length line at each source of each sub-network being said to rank "1” and a programmable length line at each sub-array of the antenna being said to rank “2"
• a first range of length introduced by a line of programmable length of rank "1” and a second range of length introduced by a row of programmable length of rank "2" overlap each other;
• At least one bit of a line of programmable length of rank "1" introduces a length equal to that introduced by a bit of a row of programmable length of rank "2";
• an amplifier is associated with each row of programmable length of rank "1" and / or each row of programmable length of rank "2";
• the rows having a programmable length of rank "1" are identical between and / or the lines with programmable length of rank "2" are identical to each other;
• the number of bits of a line of programmable length of rank "1" is less than 8, preferably 6, in particular 4.
• antenna adapted to operate on an extended instantaneous frequency band, greater than 100 MHz, preferably of the microwave domain.
• FIG. 1 is a schematic representation of the operating principle of an electronic scanning antenna
• FIG. 2 is a representation of a programmable length line
• FIG. 3 is a schematic representation of an embodiment of an electronic scanning antenna according to the invention.
• FIG. 3 diagrammatically represents an antenna 4 with electronic scanning capable of operating on an extended instantaneous frequency band.
• the antenna is subdivided into a plurality of subnets.
• the linear antenna 4 which is composed of nine sources Si, is subdivided into three subnets Rj, each having three juxtaposed sources.
• the LLPs are then distributed over two levels of the transmission / reception chain of the microwave signal: at a level corresponding to each sub-network Rj of the so-called LLPs of rank 2, and at a level corresponding to each source S, of a sub-network Rj of so-called tier 1 LLPs.
• rank 1 LLPs are referenced from 1 to 19 and rank 2 LLPs are referenced from 21 to 23.
• the delay to be introduced is the sum of the delay introduced by the rank 2 LLP associated with the subnet Rj at which the considered Si source belongs, and by the rank 1 LLP associated with the source Si considered.
• the rank 1 LLPs are identical to each other and the rank 2 LLPs are identical to each other.
• the strongest bits of rank 1 LLPs have a shorter length than the highest order bits of rank 2 LLPs.
• Tier 1 LLPs can thus be implanted more easily inside the geometrical mesh of the network constituted by the radiating sources.
• each LLP of rank 1 is located in the immediate vicinity of the radiating source with which it is associated.
• rank 1 LLPs The ohmic losses generated by rank 1 LLPs are low. They are advantageously "masked" by the addition of microwave amplifiers.
• the rank 2 LLPs are set back from the sources. Their size then constitutes a less critical constraint.
• the ohmic losses that they generate remain important, but have smaller consequences, since away from the sources. These ohmic losses can advantageously be "masked" by the insertion of suitable microwave amplifiers.
• the invention thus simplifies the implementation of programmable length lines within a network antenna.
• the directional antenna obtained has improved characteristics compared with antennas of the prior art, especially when it is used on extended instantaneous frequency bands.
• Tier 1 and Tier 2 LLPs must be mutually adapted. Indeed, the range of lengths to be generated for the proper functioning of the antenna can not be simply distributed between a first range of lengths for the LLPs of rank 1 and a second range of lengths for the LLPs of rank 2, complementary and disjoint from the first,
• this overlap is such that at least one least significant bit of the rank 2 LLPs corresponds to a most significant bit of the rank 1 LLPs.
• the characteristics of a sub-network are determined. For this, taking into account criteria relating to the characteristics sought for the global antenna (pointing accuracy for the antenna, granularity of the angular position of the beam, average level of the lobes ...) make it possible to determine the most significant delay. small that can be introduced into a signal. This smallest delay is identified by the length of the least significant bit, LSB1, of rank 1 LLPs.
• total number M M1 xM2 of sources constituting the antenna (where M1 is the number of sources in a sub-network and M2 the number of sub-networks network subdividing the antenna), form of the mesh of the antenna network, implementation of the components in the mesh, maximum number of bits of the LLP of rank 1 (according to the congestion and the ohmic losses) ...
• N1 must remain as low as possible, for example 6 or 7 bits, so that the corresponding rank 1 LLP can be integrated near the source, and to limit the ohmic losses.
• the maximum length Lmax1 to be generated between two sources belonging to the same sub-network is then determined, that is to say the maximum length that the rank 1 LLPs can introduce alone.
• Lmax1 V2a sin ( 9max).
• the highest MSB 2 bit of the rank 2 LLPs is defined from the maximum length Lmax that the antenna must be able to introduce.
• Lmax Lmaxl + Lmax2.
• Lmaxl Lmaxl + Lmax2.
• the maximum length Lmax depends on the shape of the antenna. For example, for an antenna intended to electronically scan its beam up to an angle 6max throughout the space, and having a disk shape of diameter D, the maximum length to be generated is:
• the maximum length to be generated is:
• Lmax2 2MSB2 - LSB2
• MSB2 2 N2 _1 LSB2.
• a third step the choice of LSB2 and N2 is optimized and the overlap between the first and second delay ranges introduced by the rank 1 LLPs and the rank 2 LLPs, respectively.
• LmaxO-LminO the range of lengths to be generated for a sub-network is calculated: LmaxO-LminO, where LmaxO, respectively LminO, is the maximum length, respectively minimum, to be generated in this subnet from a share of the rank 2 LLP associated with this subnetwork, and secondly rank 1 LLPs associated with each source of this subnetwork, to obtain the pointing angle ⁇ 0.
• the LminO value is framed by two successive length values, Li and Li + 1, introduced by the rank 2 LLP associated with the subnet.
• the difference Li + 1 - Li corresponds to the discretization of the LLPs of rank 2, that is to say to LSB2.
• LSB 2 The determination of LSB 2 can be performed more easily by maximizing LminO-Li by Li + 1 -Li, or LSB2, in the above inequality:
• This third step is iterated for different value of the pointing angle ⁇ 0 to determine the values of LSB2 and N2 which, given the sometimes complex geometry of the antenna, allow all angles of pointing within the domain predefined angle for the antenna.
• this procedure results in the number of common bits between the rank 1 LLPs and the rank 2 LLPs being at least 1. Beyond two bits in common, it is preferable to reduce the number of bits of rank 1 LLPs.
• the bit of the rank 2 LLP When using the antenna, for the generation of a length belonging to the overlap interval between the first and second ranges, the bit of the rank 2 LLP will be selected in priority.
• the lengths accessible by the LLPs of rank 1 are then: 0, 10, 20, 30, 40, 50, 60 and 70 mm.
• the solution for minimizing this overlap is to have a single common bit between the rank 1 LLPs and the rank 2 LLPs, the 20 mm length bit.
• LLPs in two levels may be generalized to a distribution in K levels, with K an integer greater than or equal to two, for antennas with a large number of sources.
• LLPs The production of the LLPs is carried out in a conventional manner. They can be realized as MMIC components, for example from elementary cells of the "all-pass" filter type, in particular for rank 1 LLPs. They can also be realized as a combination of cells of the filter type "all-pass” and physical lengths (sections of cable TEM). Finally, they can be made from only physical lengths, for example for rank 2 LLPs.

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• 2015
  • 2015-07-21 FR FR1501551A patent/FR3039327B1/fr active Active
• 2016
  • 2016-07-18 EP EP16739191.1A patent/EP3326240A1/de not_active Withdrawn
  • 2016-07-18 WO PCT/EP2016/067075 patent/WO2017013076A1/fr not_active Ceased

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