IL284045B2

IL284045B2 - Bidirectional hyperfrequency coupler comprising two parallel double-rib waveguides

Info

Publication number: IL284045B2
Application number: IL284045A
Authority: IL
Original assignee: Thales Sa
Priority date: 2018-12-18
Filing date: 2019-12-18
Publication date: 2024-05-01
Also published as: EP3900104A1; FR3090217A1; EP3900104B1; WO2020127424A1; FR3090217B1; IL284045A; IL284045B1

Description

WO 2020/127424 PCT/EP2019/085852 BIDIRECTIONAL HYPERFREQUENCY COUPLER COMPRISING TWO PARALLEL DOUBLE-RIB WAVEGUIDES id="p-1" id="p-1" id="p-1"

[0001] The present invention relates to a bidirectional microwave coupler comprising two parallel double-rib waveguides.[0002] In most microwave devices, it is necessary to be able to extract a given portion of the generated signal in order to measure the various parameters defining this microwave signal and, possibly, to correct them on the basis of the usage conditions. This operation is performed using devices known by the name of couplers, which extract a given percentage of the power that is carried.[0003] Since microwave emission sources deliver powers that are often high, the most suitable propagation means are waveguides.[0004] Very wideband directional couplers are known, with a band typically from GHz to 100 GHz, produced in the form of hole couplers, the holes serving to create the coupling between the two waveguides.[0005] One exemplary embodiment of such a hole coupler is illustrated in figure 1, taken from the book "Microwave Engineering", p. 339, by David M. Pozar, 4ed, Wiley, 2012.[0006] Figure 1 shows a bidirectional microwave hole coupler comprising two superimposed parallel waveguides, respectively forming a main path VP and a coupling path VC. The coupler comprises N+1 holes indexed from n=0 to n=N.[0007] Such a multi-hole coupler makes it possible to act on directivity as a function of frequency. Specifically, all of the diameters of the holes are the same number of parameters of an associated function and make it possible to obtain for example a Chebyshev response, or even a binomial response, among the most conventional ones.[0008] Considering the general case of the multi-hole coupler from figure 1, comprising N+1 equidistant holes coupling the two parallel waveguides, the amplitude of the incident wave in the main path guide VP is A. At each aperture, a small fraction of this wave is transmitted to the coupled path, generating, on this path, a positively directed wave of amplitude A * Fn and a negatively directed wave of amplitude A * Bn. Fn and Bn are respectively the coupling coefficients of the positive wave and of the negative wave. The holes are equidistant by a distance d, in m.

WO 2020/127424 PCT/EP2019/085852 id="p-9" id="p-9" id="p-9"

[0009] For example, a 20 dB coupler has a power coupling factor of 100.01 = 20/1°־, such that the power transmitted by the waveguide has the value 1 - 0.01 = 0.99 of the incident power (1% coupled to the upper guide). The voltage (or field) drop in the main path waveguide VP is equal to V0,99 = 0.995, that is to say 0.5%. The amplitude of the incident field is thus identical at each hole, but the phase changes from one aperture to another.[0010] An aperture or hole therefore generally excites the opposing traveling waves with different amplitudes. Therefore, calling Fn the coupling coefficient of the nth hole in the forward direction, and calling Bn the coupling coefficient of the nth hole in the backward direction, the amplitude of the wave in the forward direction may be written: [0011]F = Ae־^Nd’ 51"=0Fn, since all of the components travel on a path of the same length.[0012] The amplitude of the wave in the backward direction may be written:[0013] B = A^^B-^1™^2־-, since the length of the path of the nth component is 2pnd.[0014]/? represents the propagation constant, in rad/m.[0015] The phase reference is taken at the first hole of index 0.[0016] Coupling C and directivity D may be calculated using the following relationships:201og|^=0Fn| dB - = |؛| 0017 ] C = -201og ] I ni IVW n dB ----- 20 log =- ؛ I I 2jh=0 1[0019] One aim of the invention is to reduce the significant length for a given directivity.[0020] What is proposed, according to one aspect of the invention, is a bidirectional microwave coupler comprising two parallel double-rib waveguides, having two respective faces arranged opposite one another and mechanically connected by a metal layer, and comprising antenna assemblies connecting the respective interiors of solid parts outside the ribs of the two waveguides, an antenna assembly comprising an antenna mounted fixedly in a dielectric insert that is mounted fixedly in said metal layer.

WO 2020/127424 PCT/EP2019/085852 id="p-21" id="p-21" id="p-21"

[0021] The length of such a coupler is thus reduced in comparison with a hole coupler from the prior art, since it makes it possible, in comparison with circular apertures, to achieve stronger coupling between the main path and the coupled path.[0022] The length is thus shortened by about 30% to 70% in comparison with a hole coupler. For example, a 100 mm coupler was thus produced in the 6 to 18 GHz band while retaining good directivity, i.e. directivity greater than 17 dB.[0023] The spacing between the antennas according to the invention may be markedly less than that necessary for an equivalent hole coupler, which, if it were of the same length, for example 100 mm, would have a directivity markedly less than dB, of the order of 10 dB.[0024] In one embodiment, a dielectric insert comprises an outer shoulder and an inner shoulder.[0025] The outer shoulder makes it possible to keep the insert fixed in the metal layer between the two waveguides, and the inner shoulder makes it possible to keep the antenna fixed in the insert, and to do so in an easily achievable manner and at reduced cost.[0026] In one embodiment, a dielectric insert that is mounted fixedly in said metal layer does not have a portion inside the two waveguides.[0027] There is thus no insert part inside the two waveguides, thereby simplifying the design of the coupler and facilitating heat exchange.[0028] According to one embodiment, an antenna is cylindrical in shape and provided with a collar that is intended to be mounted abutting against the inner shoulder of an insert.[0029] Cylindrical shapes are easy to produce for the stops and also for the shoulders. [0030] In one embodiment, a dielectric insert comprises a fluoropolymer, such as polytetrafluoroethylene (PTFE for short), which is a fluoropolymer derived from tetrafluoroethylene.[0031] According to one embodiment, an antenna comprises aluminum and/or copper. [0032] In one embodiment, the metal layer comprises copper and/or aluminum.[0033] The invention will be better understood on studying a few embodiments described by way of completely non-limiting example and illustrated by the appended drawings, in which:[0034] figure 1 schematically illustrates a bidirectional microwave hole coupler according to the prior art; WO 2020/127424 PCT/EP2019/085852 id="p-35" id="p-35" id="p-35"

[0035] figure 2 schematically illustrates a bidirectional microwave coupler, in perspective, according to one aspect of the invention;[0036] figure 3 schematically illustrates the bidirectional microwave coupler from figure 1, in a sectional view, according to one aspect of the invention;[0037] figure 4 schematically illustrates an antenna assembly, according to one aspect of the invention; and[0038] figure 5 schematically illustrates a plurality of antenna assemblies, in a sectional view, according to one aspect of the invention.[0039] Throughout the figures, elements having identical references are similar.[0040] In the present description, the embodiments that are described are non- limiting, and features and functions that are well known to a person skilled in the art are not described in detail.[0041] Figure 2 schematically shows a bidirectional microwave coupler, in a sectional view, according to one aspect of the invention, comprising two parallel double-rib NVp, Nvc waveguides VP, VC, having two respective faces arranged opposite one another and mechanically connected by a metal layer CM.[0042] The two waveguides VP and VC have two respective faces arranged opposite one another (via their large side) and mechanically connected by the metal layer CM, and comprise antenna assemblies EA connecting the respective interiors of solid parts outside the ribs Nvc, Nvp of the two waveguides VP, VC.[0043] As shown in figures 4 and 5, an antenna assembly EA comprises an antenna Ant mounted fixedly in a dielectric insert Ins that is mounted fixedly in the metal layer CM.[0044] The coupling is thus made by the antennas Ant, and not by holes as in the prior art.[0045] The dielectric insert Ins serves both as an electrical insulator and as a support. [0046] The insert Ins comprises an inner shoulder EPI and an outer shoulder EPE. The outer shoulder EPE makes it possible to keep the insert Ins fixed in the metal layer CM between the two waveguides VP, VC, and the inner shoulder EPI makes it possible to keep the antenna Ant fixed in the insert Ins, and to do so in an easily achievable manner and at reduced cost.[0047] A dielectric insert Ins may remain outside the two waveguides VP, VC, and there is thus no insert part inside the two waveguides, thereby simplifying the design of the coupler and facilitating heat exchange.

WO 2020/127424 PCT/EP2019/085852 id="p-48" id="p-48" id="p-48"

[0048] These antennas Ant may vary in diameter and height after optimization, making it possible to achieve better performance in terms of directivity and to reduce the total length of the coupler.[0049] An antenna Ant may be cylindrical in shape and provided with a collar Col that is mounted abutting against the inner shoulder of the insert Ins.[0050] The dielectric is chosen according to usage requirements, taking into account temperature and power.[0051] Figure 3 is a sectional view in the longitudinal direction of the coupler from figure 2.10

Claims

WO 2020/127424 PCT/EP2019/085852 CLAIMS

1. A bidirectional microwave coupler comprising two parallel double-rib (NVP, NVC) waveguides (VP, VC), having two respective faces arranged opposite one another and mechanically connected by a metal layer (CM), and comprising antenna assemblies (EA) connecting the respective interiors of solid parts outside the ribs of the two waveguides (VP, VC), an antenna assembly (EA) comprising an antenna (Ant) mounted fixedly in a dielectric insert (Ins) that is mounted fixedly in said metal layer (CM).

2. The coupler as claimed in claim 1, wherein a dielectric insert (Ins) comprises an outer shoulder (EPE) and an inner shoulder (EPI).

3. The coupler as claimed in either of the preceding claims, wherein a dielectric insert (Ins) that is mounted fixedly in said metal layer (CM) does not have a portion inside the two waveguides (VP, VC).

4. The coupler as claimed in one of the preceding claims, wherein an antenna (Ant) is cylindrical in shape and provided with a collar (Col) that is intended to be mounted abutting against the inner shoulder (EPI) of an insert (Ins).

5. The coupler as claimed in one of the preceding claims, wherein a dielectric insert (Ins) comprises a fluoropolymer.

6. The coupler as claimed in one of the preceding claims, wherein an antenna (Ant) comprises aluminum and/or copper.

7. The coupler as claimed in one of the preceding claims, wherein the metal layer (CM) comprises copper and/or aluminum.