WO2008145165A1 - Ligne à retard ferroélectrique - Google Patents

Ligne à retard ferroélectrique Download PDF

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Publication number
WO2008145165A1
WO2008145165A1 PCT/EP2007/004824 EP2007004824W WO2008145165A1 WO 2008145165 A1 WO2008145165 A1 WO 2008145165A1 EP 2007004824 W EP2007004824 W EP 2007004824W WO 2008145165 A1 WO2008145165 A1 WO 2008145165A1
Authority
WO
WIPO (PCT)
Prior art keywords
delay line
waveguide body
ridge
ferroelectric
dielectric
Prior art date
Application number
PCT/EP2007/004824
Other languages
English (en)
Inventor
Giorgio Bertin
Marco Braglia
Bruno Piovano
Original Assignee
Telecom Italia S.P.A.
Pirelli & C. S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telecom Italia S.P.A., Pirelli & C. S.P.A. filed Critical Telecom Italia S.P.A.
Priority to PCT/EP2007/004824 priority Critical patent/WO2008145165A1/fr
Publication of WO2008145165A1 publication Critical patent/WO2008145165A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P9/00—Delay lines of the waveguide type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/18—Phase-shifters
    • H01P1/181—Phase-shifters using ferroelectric devices

Definitions

  • a voltage-variable ferroelectric waveguide phase shifter according to the preamble of claim 1 is known from US 5,724,011 A.
  • the prior-art phase shifter comprises a symmetrical ridge waveguide with two contacting slabs of ferroelectric material filling the gap between two confronting ridges.
  • a flat electrode is disposed in the ferroelectric material, in the symmetry plane of the waveguide, and is connected to a variable voltage source to establish a variable transverse electrical field within the ferroelectric material and to consequently vary the delay of electromagnetic signals propagating along the waveguide.
  • a continuously electrically tunable delay line including: a waveguide body; a metal ridge longitudinally extending within said waveguide body; a ferroelectric member also longitudinally extending within said waveguide body along at least a portion of the ridge, and a variable d.c. voltage source for applying a variable transversal electrical field to said ferroelectric member to vary the dielectric constant thereof and hence the delay imparted by the line, wherein said ridge is electrically insulated from the waveguide body, said ferroelectric member is comprised between said metal ridge and a confronting wall of the waveguide body and said d.c. voltage source is connected between said ridge and said confronting wall of the waveguide body.
  • the delay line may further include coaxial input/output connectors at opposed ends of the waveguide body, for connection to coaxial cables carrying input/output signals and means for impedance matching between the coaxial cables and the ferroelectric member.
  • said impedance matching is achieved through a plurality of dielectric members located between each connector and the ferroelectric member and having different dielectric constants, increasing in a direction from a connector to the ferroelectric member, and electrical length ⁇ /4, ⁇ being the wavelength of a signal transmitted along the line.
  • said impedance matching is achieved through a plurality of dielectric members located within each connector and having different dielectric constants, increasing in a direction toward the ferroelectric member.
  • the invention also provides an apparatus for transmitting a signal to a plurality of users of a wireless communication system via diversity antennas, said apparatus including, along a signal path towards said diversity antennas, at least one tunable delay line generating at least one variably-delayed replica of said signal and consisting of an electrically-tunable delay line according to the invention.
  • the invention also provides a wireless communication system including the above transmitting apparatus.
  • Fig. 1 is a schematic cross-sectional view explaining the basic principles of an electrically-controllable delay line according to the invention
  • Fig. 4 shows graphs of the phase and the phase shift, versus frequency, in a practical example of the delay line shown in Fig. 2;
  • Fig. 5 is a perspective view, in longitudinal cross-section, of a variant of the first embodiment
  • Fig. 6 is a perspective view, in longitudinal cross-section, of a second embodiment of the invention.
  • FIG. 7 is a schematic block diagram of a transmitting apparatus of a wireless communication system with dynamic delay diversity, using delay lines according to the invention.
  • Fig. 1 there is schematically shown in cross sectional view the structure of an electrically controllable delay line according to the invention, generally denoted by 1.
  • the physical support for delay line 1 is a ridge waveguide, which consists of a metallic waveguide body 2 with rectangular cross-section and a longitudinal partition or ridge 3, also of rectangular cross-section, centrally arranged in the waveguide cavity 4 and electrically separate from waveguide body 2.
  • the drawings show a vertically arranged ridge 3, with the major sides of the rectangular cross-section parallel to the side walls of waveguide body 2.
  • Teflon® Teflon®
  • Member 5 also provides mechanical support for ridge 3, whose top part is embedded within Teflon® member 5, as shown in Fig. 1.
  • the active member of delay line 1 is a slab 6 of ferroelectric material, i.e. a dielectric material with electrically controllable dielectric constant, which is arranged between the bottom surface of ridge 3 and bottom wall 2" of waveguide body 2 and is secured to the latter.
  • ferroelectric material i.e. a dielectric material with electrically controllable dielectric constant
  • Several materials can provide the desired controllability of the dielectric constant.
  • BST Barium Strontium Titanate
  • Ba (1-x) Sr x Ti ⁇ 3 or BST composites are used in delay lines or phase shifters for microwave applications.
  • metal ridge 3 and dielectric members 5, 6 with far different dielectric constants results in the electric field being essentially concentrated in the region where the active (ferroelectric) material is located.
  • the electrical separation of ridge 3 from waveguide body 2 results in a two-conductor delay line, which does not exhibit the frequency limitations of single-conductor delay lines.
  • the guide of the invention supports a quasi-TEM propagation characterised by zero cutoff frequency.
  • the variation of the dielectric constant of ferroelectric slab 6 necessary for delay tuning is obtained by applying a variable d.c. bias voltage of some kVs between ridge 3 (forming the positive pole) and bottom wall 2" of waveguide body 2.
  • the source of that bias voltage is denoted by 7.
  • connection of delay line 1 towards the exterior is obtained with coaxial connectors, of which the trace is shown by dashed-line circle 8 in the Figure, and insulation of the signal from the bias voltage is obtained by means of a commercially available DC block or a bias-tee (not shown) at the input and the output.
  • bias- tees solves also the problem of application of the bias voltage from source 7.
  • ferroelectric slab 106 is made of Ba 06S Sr 03Z TiO 3 (1.5MgO), use of which is disclosed in the paper "Parallel plate waveguide bulk ceramic ferroelectric phase shifter" by A. Deleniv et al., presented at the 35 th European Microwave Conference, Paris 2005, pages 653 - 655 of the conference proceedings.
  • the impedance matching between input/output connectors 108A, 108B and ferroelectric slab 106 is obtained by means of two sets of impedance matching dielectric members of rectangular-cross sections, symmetrically arranged at both sides of ferroelectric slab 106.
  • the different dielectric members have different dielectric constants, increasing in the direction from connector 108A, 108B to ferroelectric slab 106, and have the same electrical length ⁇ /4.
  • a set of dielectric members 109 to 112 and ferroelectric slab 106 define five delay line sections 101-1 to 101-5 characterised by different cross- sectional sizes and lengths of waveguide body 102 and/or ridge 103.
  • waveguide body 102 and ridge 103 are narrower in correspondence of the first delay line section 101-1
  • ridge 103 has different height in correspondence with the different sections, resulting in a step profile of its top surface and an indented profile of its bottom surface.
  • the variation of the cross-sectional sizes of waveguide body 102 and ridge 103 in longitudinal direction contributes to improving the impedance matching.
  • the following table 1 reports the materials employed for the impedance-matching dielectric members 109 to 112 and ferroelectric slab 106, and the sizes and electrical characteristics thereof, in an exemplary practical embodiment of delay line 101.
  • the dielectric constant of the ferroelectric material (indicated in short by BST in the table) is concerned, reference is made to a variation range from 550 to 450 obtained by varying the applied field from 1 to 3 KV/mm, as reported in the paper of Deleniv et al.
  • Table 2 in turn reports the geometrical characteristics of ridge 103 and waveguide body 102 in the various sections.
  • Fig. 5 shows a delay line 201 according to a variant of Fig. 2.
  • the dielectric member of Plexiglas® is dispensed with, so that the delay line comprises four sections 201-1 to 201-4.
  • Dielectric members 210A to 212A and 210B to 212B are made of the same dielectric materials as members 110 to 112 of Fig. 2, and still have electrical length ⁇ /4. In this case however they have cross-sectional sizes identical to each other and to ferroelectric slab 206.
  • Waveguide body 2 has constant cross- sectional size of 35mm x 18mm and ridge 203 has constant width and variable height, the height variations resulting in a toothed profile of the top surface.
  • the delay line is more compact, but this is paid with a reduction of the operating frequency band.

Landscapes

  • Waveguide Switches, Polarizers, And Phase Shifters (AREA)

Abstract

Cette invention concerne une ligne à retard électriquement réglable (1) pour des applications de radiofréquence comprend un corps guide d'ondes (2); une arête métallique (3) qui s'étend de manière longitudinale à l'intérieur du corps guide d'ondes (2), un élément ferroélectrique (6) qui s'étend également de manière longitudinale à l'intérieur du corps guide d'ondes le long d'au moins une partie de l'arête (3); et une source de tension cc variable (7) conçue pour appliquer un champ électrique transversal variable à l'élément ferroélectrique (6) afin de modifier la constante diélectrique et, de ce fait, le retard appliqué par la ligne (1). L'arête (2) est électriquement isolée du corps guide d'ondes (2) et elle est maintenue à l'intérieur d'un élément de maintien diélectrique (5) supporté par le corps guide d'ondes (2).
PCT/EP2007/004824 2007-05-31 2007-05-31 Ligne à retard ferroélectrique WO2008145165A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2007/004824 WO2008145165A1 (fr) 2007-05-31 2007-05-31 Ligne à retard ferroélectrique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2007/004824 WO2008145165A1 (fr) 2007-05-31 2007-05-31 Ligne à retard ferroélectrique

Publications (1)

Publication Number Publication Date
WO2008145165A1 true WO2008145165A1 (fr) 2008-12-04

Family

ID=39103761

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2007/004824 WO2008145165A1 (fr) 2007-05-31 2007-05-31 Ligne à retard ferroélectrique

Country Status (1)

Country Link
WO (1) WO2008145165A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2989709A (en) * 1955-09-16 1961-06-20 Bell Telephone Labor Inc Magnetically controlled wave guide switch
US4028650A (en) * 1972-05-23 1977-06-07 Nippon Hoso Kyokai Microwave circuits constructed inside a waveguide
EP0164224A1 (fr) * 1984-05-09 1985-12-11 BRITISH TELECOMMUNICATIONS public limited company Isolateur pour des radiations électromagnétiques à hyperfréquences
US4782307A (en) * 1987-06-08 1988-11-01 Hughes Aircraft Company Feed-forward microwave amplifier arrangement with ferrite temperature compensation
US20020033744A1 (en) * 2000-04-20 2002-03-21 Sengupta Louise C. Waveguide-finline tunable phase shifter

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2989709A (en) * 1955-09-16 1961-06-20 Bell Telephone Labor Inc Magnetically controlled wave guide switch
US4028650A (en) * 1972-05-23 1977-06-07 Nippon Hoso Kyokai Microwave circuits constructed inside a waveguide
EP0164224A1 (fr) * 1984-05-09 1985-12-11 BRITISH TELECOMMUNICATIONS public limited company Isolateur pour des radiations électromagnétiques à hyperfréquences
US4782307A (en) * 1987-06-08 1988-11-01 Hughes Aircraft Company Feed-forward microwave amplifier arrangement with ferrite temperature compensation
US20020033744A1 (en) * 2000-04-20 2002-03-21 Sengupta Louise C. Waveguide-finline tunable phase shifter

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