US2825060A

US2825060A - Dual-polarization antenna

Info

Publication number: US2825060A
Application number: US462826A
Authority: US
Inventors: Ruze John
Original assignee: Gabriel Co
Current assignee: Gabriel Co
Priority date: 1954-10-18
Filing date: 1954-10-18
Publication date: 1958-02-25
Anticipated expiration: 1975-02-25

Description

Feb. 25'; 1958 J. RUZE DUAL-POLARIZATION ANTENNA Filed Oct. 18. 1954 INVENTOR. JOHN RUZE BY I A TTORNE Y6 United States Patent DUAL-POLARIZATION ANTENNA John Ruze, Boston, Mass., assignor to The Gabriel Company, Cleveland, Ohio, a corporation of Ohio Application October 18, 1954, Serial No. 462,826

13 Claims. (Cl. 343-756) The present invention relates to antennas and more particularly to antenna systems operating with radio waves of complementary polarizations.

Various proposals have heretofore been made for simultaneously transmitting or receiving radio waves of differing electric-vector polarizations. Perhaps the most elementary of these proposals is the use of a plurality of dipole or other linear antennas, one oriented along each direction of polarization. To generate or receive circularly polarized waves, for example, which may be considered as the resultant of a horizontally polarized wave and a vertically polarized wave phase-displaced from the horizontally polarized wave by plus or minus ninety degrees, two perpendicularly oriented antennas have been employed. Because of the physical juxtaposition of such antennas, however, a certain amount of cross-polarization reception or transmission occurs. Some of the horizontally polarized energy, as an illustration, may induce a voltage in the vertically polarized antenna, and vice versa. This is particularly true in the ultra-highfrequency and microwave ranges where even the thickness dimension of an antenna may be an appreciable-portion of the wavelength and thus capable of intercepting cross-polarization energy. Cross coupling is also increased in the case where a common transmission system is employed and especially in waveguide microwave systems where the cross coupling could exist due to in-, advertently generated higher order modes. While this is tolerable in some systems, there are other occasions where it is entirely undesirable. As an illustration, it may be necessary to receive in a radio receiver a weak polarized radio-wave signal in the presence of a strong transmitted difierently polarized signal. Attempts have therefore been made to minimize cross-polarization effects through careful construction, orientation and symmetry of the antenna system but such techniques do not solve the problem in cases where there are very rigid requirements as to the amount of allowable cross-coupling, such as where the coupled transmitted signal is of the order of the amplitude or greater than the amplitude of the received signal itself.

An object of the present invention, therefore, is to provide a new and improved antenna system in which crosspolarization effects are minimized.

A further object is to provide a novel dual-polarization antenna system.

An additional object is to provide such an antenna system that is particularly adapted for the ultra-high-frequency and microwave frequency ranges of the radio spectrum where wave-guide techniques are employed. In summary, the present invention employs a pair of symmetrical substantially planar conducting ridges or septums preferably mounted within a flaring horn portion of a waveguide system and each extending inward from oppositely disposed flaring walls of the horn portion in substantially the same plane. This plane is, in turn, substantially perpendicular to one of the radio-wave elecice tric-vector polarizations to be employed in the wave-guide system. The inner edges of the septums diverge from each other toward the mouth of the horn portion with the separation between the adjacent opposite walls of the wave guide being too small at the throat of the horn portion but sufficient at the mouth thereof to permit a wave-guided propagation of radio waves of electric-vector polarization substantially perpendicular to the said one polarization. The two-conductor balanced transmission lines formed by the opposite faces of the ridges launches or receives radio-frequency energy that is to propagate as radio waves of the perpendicular polarization in the remaining portion of the wave-guide horn. This balanced transmission line is excited by a coaxial line, the outer conductor being connected to the adjacent ridge and the inner conductor to the other ridge. Preferred constructional details are hereinafter fully described.

Other and further objects will be hereinafter discussed and will be more particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawing the single figure of which is a perspective view of the invention in preferred form, parts being shown broken away to illustrate details of construction.

A wave-guide transmitting or receiving antenna is shown comprising a flared preferably pyramidal horn portion 1 of rectangular cross-section terminating at its throat 3 in a preferably rectangular wave guide portion 5 of substantially uniform cross-section. As will be evident from the description of operation to follow, other types of cross-sectional configurations, horns and/ or guides may be employed, though the illustrated embodiment is preferred for the particular application of the invention in which the wave-guide system is disposed at the focal region of a large paraboloidal reflector, not shown, designed to receive weak radio signals. The wave guide is shown oriented so that the upper and lower walls are the longer walls of the guide, but the apparatus may be equally well oriented in any other desired position.

While the cross-polarization-elimination techniques of the invention, moreover, may be similarly used for radio transmission, they will hereinafter be described as applied to the above-mentioned weak-signal receiving system and transmission of strong signals.

With the antenna 15 oriented as shown, it is adapted to transmit or receive radio waves of complimentary polarization. A probe antenna 7, for example, may launch or absorb vertically polarized waves, and a probe 9, horizontally polarized waves. Appropriate receiving or transmitting apparatus, not shown, may be connected to the probes as is well known. If desired, the vertically polarized waves may be launched or absorbed at a point remote from the wave-guide section or portion 5 in which event the probe 7 may be dispensed with and a further wave-guide section, not shown, may be attached to the portion 5 at the flange 11. The width W of the waveguide portion 5 is sufficient, that is, equal to or greater than the half-wave length of the radio energy, to permit the progagation therein of, for example, the TE mode of wave of a predetermined frequency with the electricvector vertically oriented parallel to the probe 7. The length of the wave-guide section 5 must, however, be made sufiiciently long to attenuate any higher order modes that are inherently generated by the probe 7 but are non-propagating in the section 5.

The probe 9, however, is an extension of an inner conductor 13 of a coaxial transmission line. The outer conductor 15 of the coaxial transmission line is shown connected at 19 to the side wall 17 of the horn portion 1 of 3 the antenna, preferably near the throat 3. Insulator supporting spacers, such as 33, may maintain the inner and outer conductors out of electrical contact, as is well known. The two-conductor transmission line 13, 15 will connect the probe 9 to an appropriate receiver or transmitter, not shown, as before explained. Other types of twoconductor transmission lines besides the coaxial type may be employed in connection with both the probes 9 and 7, but the coaxial type has certain advantages including the shielding of the inner conductor 13 by the outer conductor 15. The horizontal probe 9 is shown extending within the horn portion 1 near the throat 3 through an aperture 21 in a conductive planar ridge or septum 23, terminating at 27 within a similar conductive ridge or septum 25. Supporting insulator spacers 29 prevent electrical contact between the probe 9 and the aperture 21. The ridges 23 and 25 are preferably of the same roughly triangular shape, or special gradual shape for use in broad-banding, each having one side secured to the respective flaring walls 17 and 18 of the horn portion 1. They are shown symmetrically disposed within substantially the same horizontal plane, midway between the upper and lower walls of the horn portion 1. From the inner adjacent spaced vertices 22 and 24 of the respective septums 23 and 25, the inner edges 26 and 28 of the septums diverge as they extend toward the mouth 29 of the horn portion 1. They preferably diverge along a somewhat gradual curve, as illustrated, from a separation W at the vertices 22 and 24 to a separation substantially equal to the full width of the mouth 29. The separation of the opposite walls of the wave guide is made too small, however, in the throat region, to permit wave-guide propagation of Waves of the said predetermined frequency and of a polarization parallel to the probe 9. As the separation between the diverging edges 26 and 28 increases toward the mouth 29, however, the separation between the opposite walls 17, 18 becomes large enough to permit of wave-guiding within the horn portion 1 of such waves. These Waves may, for example, be of TE mode. Since the probe extension 9 of the inner coaxial-line conductor 13 terminates at 27 upon the septum 25, preferably just to the left of the vertex 24, as shown, and the outer conductor 15 terminates at 19 upon the wall 17 and hence upon the septum 23 secured thereto, radio-frequency energy in the coaxial line 13, 15 will be propagated, not as wave-guided radio waves, but as two-conductor transmission-line-propagated radio-frequency energy between the ridges or septums 23 and 25. The ridges or septums, indeed, act merely as extensions of the respective two-conductor transmission-line conductors 15 and 139 until the separation between the wave-guiding walls adjacent the septums 23 and 25 becomes wide enough to permit propagation of the energy as uni-conductor wave-guided waves of, for example, the TE mode. At the point where the transmission-line ridges 23, 25 and the guiding walls 17 and 18 adjacent thereto are separated a sufiicient distance to permit the TE mode to propagate, there will be a gradual transfer of the energy from the two-conductor transmission-line propagation mode to the wave-guide mode. The relative amount of energy in each mode depends upon the characteristic impedance of the transmission-line and wave-guiding systems, so that when the ridges 23 and 25 blend into the Walls 17 and 18, near the mouth of the horn 1, all of the energy is propagated in the wave-guide mode.

The manner in which this construction substantially completely eliminates cross-polarization effects between radio waves of electric-vector polarization parallel to the respective perpendicularly oriented probes 7 and 9 will now be explained. Energy polarized parallel to the plane of the ridges 23, 25 will not propagate toward the probe 7 as the section is below cut-off for this polarization and this section 5 can be made of sufiicient length to provide adequate attenuation. Waves of polarization parallel to the probe 7, however, can pass right by the septums 23 and 25 since the septums lie in a plane perpendicular to the probe 7. There will be some crosspolarization vertically polarized energy induced in the septums 23 and 25 because they have a small vertical or thickness dimension. In view of the symmetrical or balanced placement of the ridges or septums 23, 25, however, any vertically polarized voltage set up on one side of the horizontal probe 9 on one septum will be balanced by a similar voltage on the septum on the other side of the probe 9. The probe 9 will therefore not pick up any vertically polarized energy. In actual practice, indeed, this structure has been found to produce almost complete cancellation of cross-polarized voltages. By making the ridges slightly unsymmetrical, furthermore, the cancellation can be rendered substantially complete over a wide band of frequencies.

In order to compensate for reflections from the edges 35 and 37 of the septums 23 and 25 facing the probe 7, the edges 35 and 37 are preferably also caused to diverge away from the vertices 22 and 24 but toward the throat 3, the angle of divergence being very much greater than that subtended by the septum edges 26 and 28. Energy reflected from successive regions along the diverging edges 35 and 37 will travel successively different paths producing an overall at least partial cancellation effect. This effect and proper matching may be further attained through the use of one or more capacitive irises 36 mounted upon the upper and preferably also upon the lower inner walls of the wave-guide-portion 5 and extending inward of the guide in a plane or planes substantially parallel to the probe 7. Alternately, an inductive iris or other means may be used as is well known in impedance-matching techniques.

If the invention is used with energy of the same frequency at the probes 7 and 9, the polarization diversity effects of the invention are produced. Additional frequency diversity can also be achieved, however, if different frequencies are used. The horn 1, moreover, may be closed at its month by any well-known radio-permeable window 2 and the whole interior may be sealed with any desired gas at any desired pressure.

Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A wave guide having, in combination, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar conducting ridges disposed within the wave guide displaced from the first-named means and each extending inward of the wave guide in substantially the same plane substantially perpendicular to the said predetermined direction, the inner edges of the ridges being separated along the complete length thereof and shaped to provide a successively increasing separation therebetween from a first region where the separation between opposite walls of the wave guide adjacent the ridges is too small to permit of wave-guided propagation within the wave guide of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a second region thereof where the separation is sufficient to permit of such wave-guided propagation within the wave guide, and means comprising a two-conductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the said first region and terminating upon the other ridge.

2. A wave guide having, in combination, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar conducting ridges disposed within the wave guide displaced from the first-named means and each extending inward of the wave guide in substantially the same plane substantially perpendicular to the said predetermined direction, the inner edges of the ridges being separated along the complete length thereof and shaped to provide a succesively increasing separation therebetween from a first region where the separation between opposite walls of the wave-guide adjacent the ridges is too small to permit of wave-guided propagation within the wave guide of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a second region thereof where the separation is suflicient to permit of such waveguided propagation within the wave guide, and means comprising a coaxial transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the ridges near the said first region and terminating upon the other ridge.

3. A wave guide having, in combination, a portion of substantially uniform cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar conducting ridges disposed within the horn portion of the wave guide and extending inward from oppositely disposed flaring walls of the same in substantially the same plane substantially perpendicular to the said predetermined direction, the inner edges of the ridges being separated along the complete length thereof and diverging from each other toward the mouth of the horn portion with the separation between the opposite walls of the wave guide being too small at the throat of the horn portion to permit of wave-guided propagation within the horn portion of radio waves of electricvector polarization substantially perpendicular to the said predetermined direction and suflicient to permit of such wave-guided propagation near the mouth of the horn portion, and means comprising a two-conductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the throat of the horn portion and terminating upon the other ridge.

4. A wave guide having, in combination, a portion of substantially uniform cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar conducting ridges disposed within the horn portion of the wave guide and extending inward from oppositely disposed flaring walls of the same in substantially the same plane substantially perpendicular to the said predetermined direction, the inner edges of the ridges being separated along the complete length thereof and diverging from each other toward the mouth of the horn portion with the separation between the opposite walls of the wave guide being too small at the throat of the horn portion to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction and sutficient to permit of such wave. guided propagation near the mouth of the horn portion, and means comprising a coaxial two-conductor transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge, and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the ridges near the throat of the horn portion and terminating upon the other ridge.

5. A wave guide having, in combination, a portion of substantially uniform cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar triangular conducting ridges disposed within the horn portion of the wave guide and extending inward from oppositely disposed flaring walls of the same in substantially the same plane substantially perpendicular to the said predetermined direction, the inner edges of the substantially triangular ridges forming the sides of the triangles nearer the mouth of the horn portion being separated along the complete length thereof and diverging from each other toward the said mouth with the separation between the opposite walls of the wave guide increasing from a value at the adjacent inner vertices of the substantially triangular ridges too small to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a value suflicient to permit of such wave-guided propagation near the said mouth of the horn portion, the inner edges of the sides of the triangles nearer the throat of the horn portion more rapidly diverging from each other toward the said throat, and means comprising a twoconductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the said throat and terminating upon the other ridge.

6. A wave guide having, in combination, a portion of substantially uniform cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization, a pair of substantially planar triangular conducting ridges disposed within the horn portion of the wave guide and extending inward from oppositely disposed flaring walls of the same in substantially the same plane substantially perpendicular to the said predetermined direction and substantially symmetrically disposed within the horn portion of the wave guide, the inner edges of the substantially triangular ridges forming the sides of the triangles nearer the mouth of the horn portion being separated along the complete length thereof and diverging from each other toward the said mouth with the separation between the opposite walls of the wave guide increasing from a value at the adjacent inner vertices of the substantially triangular ridges too small to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a value suflicient to permit of such wave-guided propagation near the said mouth of the horn portion, the inner edges of the sides of the triangles nearer the throat of the horn portion more rapidly diverging from each other toward the said throat, and means comprising a coaxial two-conductor transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the said adjacent inner vertices of the ridges and terminating upon the said inner vertex of the other ridge.

7. A wave guide of substantially rectangular crosssection having, in combination, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter wave-guide walls, a pair of substantially planar conducting ridges disposed within the wave guide displacedv from the first-named means and each extending inward of the wave guide from one of the said shorter walls in substantially the same plane substantially perpendicular to the said shorter walls, the inner edges of the ridges being separated along the complete length thereof and shaped to provide a successively increasing separation therebetween from a first region where the separation between the opposite shorter walls of the wave guide adjacent the ridges is too small to permit of wave-guided propagation within the wave guide of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a second region thereof where the separation is sufficient to permit of such wave-guided propagation within the wave guide, and means comprising a two-conductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the said-first region and terminating upon the other ridge.

8. A wave guide of substantially rectangular crosssection having, in combination, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter wave-guide walls, a pair of substantially planar conducting ridges disposed within the wave guide displaced from the first-named means and each extending inward of the Wave guide from one of the said shorter walls in substantially the same plane substantially perpendicular to the said shorter walls, the inner edges of the ridges being separated along the complete length thereof and shaped to provide a successively increasing separation therebetween from a first region where the separation between the opposite shorter walls of the wave guide adjacent the ridges is too small to permit of wave-guided propagation within the wave guide of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a second region thereof where the separation is sufficient to permit of such wave-guided propagation within the wave guide, and means comprising a coaxial transmission line having its outer conductor connected to a portion of one of the shorter walls adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the ridges near the said first region and terminating upon the other ridge.

9. A wave guide having, in combination, a portion of substantially uniform rectangular cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter waveguide walls, a pair of substantially planar conducting ridges disposed within the horn portion of the wave guide and extending inward from the oppositely disposed flaring shorter walls of the same in substantially the same plane substantially perpendicular to the said shorter walls, the inner edges of the ridges being separated along the complete length thereof and diverging from each other toward the mouth of the horn portion with the separation between the shorter walls of the wave guide being too small at the throat of the horn portion to permit of waveguided propagation within the horn portion of radio Waves of electric-vector polarization substantially perpendicular to the said predetermined direction and sufficient to permit of such wave-guided propagation near the mouth of the horn portion, and means comprising a twoconductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the throat of the horn portion and terminating upon the other ridge.

10. A wave guide having, in combination, a portion of substantially uniform rectangular cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter waveguide walls, a pair of substantially planar conducting ridges disposed within the horn portion of the wave guide and extending inward from the oppositely disposed flaring shorter walls of the same in substantially the same plane substantially perpendicular to the said shorter walls, the inner edges of the ridges being separated along the complete length thereof and diverging from each other toward the mouth of the horn portion with the separation between the shorter walls of the wave guide being too small at the throat of the horn portion to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction and sufiicient to permit of such wave-guided propagation near the mouth of the horn portion, and means comprising a coaxial transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the ridges near the throat of the horn portion and terminating upon the other ridge.

11. A wave guide having, in combination, a portion of substantially uniform rectangular cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter waveguide walls, a pair of substantially planar triangular conducting ridges disposed within the horn portion of the wave guide and extending inward from the oppositely disposed flaring shorter walls of the same in substantially the same plane substantially perpendicular to the said shorter walls, the inner edges of the substantially triangular ridges forming the sides of the triangles nearer the mouth of the horn portion being separated along the complete length thereof and diverging from each other toward the said mouth with the separation between the shorter walls of the wave guide increasing from a value at the adjacent inner vertices of the substantially triangular ridges too small to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a value sufiicient to permit of such wave-guided propagation near the said mouth of the horn portion, the inner edges of the sides of the triangles nearer the throat of the horn portion more rapidly diverging from each other toward the said throat, and means comprising a two-conductor transmission line having one conductor connected to one ridge and the other conductor extending between the ridges near the said throat and terminating upon the other ridge.

12. A wave guide having, in combination, a portion of substantially uniform rectangular cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter waveguide walls, a pair of substantially planar triangular conducting ridges disposed within the horn portion of the wave guide and extending inward from the oppositely disposed flaring shorter walls of the same in substantially the same plane substantially perpendicular to the said short er walls and substantially symmetrically disposed between the longer walls of the horn portion of the wave guide, the inner edges of the substantially triangular ridges forming the sides of the triangles nearer the mouth of the horn portion being separated along the complete length thereof and diverging from each other toward the said mouth with the separation between the shorter walls of the guide increasing from a value at the adjacent inner vertices of the substantially triangular ridges too small to permit of wave-guided propagation within the horn portion of radio waves of electric-vector polarization substantially perpendicular to the said predetermined direction to a value suflicient to permit of such wave-guided propagation near the said mouth of the horn portion, the inner edges of the sides of the triangles nearer the throat of the horn portion more rapidly diverging from each other toward the said throat, and means comprising a coaxial transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the said adjacent inner vertices of the ridges and terminating upon the said inner vertex of the other ridge.

13. A wave guide having, in combination, a portion of substantially uniform rectangular cross-section terminating in an outwardly flaring horn portion, means for launching or receiving radio waves of a predetermined frequency and a predetermined direction of electric-vector polarization substantially parallel to the shorter waveguide walls, a pair of substantially planar triangular conducting ridges disposed within the horn portion of the wave guide and extending inward from the oppositely disposed flaring shorter walls of the same in substantially the same plane substantially perpendicular to the said shorter walls and substantially symmetrically disposed between the longer walls of the horn portion of the wave guide, the inner edges of the substantially triangular ridges forming the sides of the triangles nearer the mouth of the horn portion being separated along the complete length thereof and diverging from each other toward the said mouth with the separation between the shorter walls of the wave guide increasing from a value at the adjacent inner vertices of the substantially triangular ridges too small to permit of wave-guided propagation within the horn portion ofiradio Waves of electricvector polarization substantially perpendicular to the said predetermined direction to a value sufficient to permit of such wave-guided propagation near the said mouth of the horn portion, the inner edges of the sides of the triangles nearer the throat of the horn portion more rapidly diverging from each other'toward the said throat, and means comprising a coaxial two-conductor transmission line having its outer conductor connected to a portion of the wave-guide wall adjacent one ridge and hence connected to the said one ridge and its inner conductor extending in a direction substantially perpendicular to the said predetermined direction through an aperture in the said one ridge, between the said adjacent inner vertices of the ridges and terminating upon the said inner vertex of the other ridge, and conductive iris means extending substantially parallel to the said predetermined direction and disposed within the wave-guide portion of substantially uniform cross-section.

References Cited in the file of this patent UNITED STATES PATENTS