Polarization separator and wave-guide-microstrip line mode transformer for microwave apparatus

Abstract: A polarization separator for separating orthogonal polarization waves (H,V) into a horizontal polarization wave component (H) and a vertical polarization wave component (V) is minimized in size. A metal pole in the form of a thin metal bar (8) is disposed in a circular waveguide (4) of a waveguide member (1) into which the orthogonal polarization waves are introduced, and reflects the horizontal polarization wave component so that it is outputted through an output terminal (5) formed in a circumferential wall of the waveguide member. Meanwhile, the vertical polarization wave component propagates in a substantially rectangular waveguide provided rearwardly of the metal pole and is outputted from another output terminal (15). Since the rectangular waveguide is formed in a cutoff structure for the horizontal polarization wave component, the reflection means can be formed from the metal pole in the form of a thin bar, and consequently, the polarization separator can be minimized.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a polarization separator which separates orthogonal polarization electromagnetic waves propagating in a circular waveguide into a horizontal polarization wave and a vertical polarization wave, and more particularly to a polarization separator for use with a reception antenna or a like apparatus for broadcasting such as CS (Communication Satellite) broadcasting in Japan or ASTRA satellite broadcasting in Europe wherein horizontal polarization waves and vertical polarization waves are transmitted as orthogonal polarization waves modulated in various channels. Description of the Related Art Various broadcast waves are transmitted from artificial satellites floating at the height of 36,000 Km from the ground. Of such broadcast waves, CS broadcast waves for commercial use can be received in Japan in addition to BS (Broadcasting Satellite) broadcast waves for use for television broadcasting. A broadcasting frequency band of microwaves or quasi millimeter waves (SHF) is utilized for such broadcast waves. The broadcast waves are received by means of a parabola antenna normally installed on the roof, converted into predetermined frequencies by a converter and inputted to a tuner by which a broadcasting channel is selected. A parabola antenna for receiving orthogonal polarization waves of the CS broadcasting or the ASTRA satellite broadcasting from among various broadcast waves is typically constructed in such a manner as shown in FIG. 8. Referring to FIG. 8, the parabola antenna shown includes a parabola reflector 81 for reflecting and converging radio waves from a satellite, a primary horn 83 for receiving the thus converged radio waves, a polarization separator 1 for separating the orthogonal polarization radio waves received by the primary horn 83 into horizontal polarization waves and vertical polarization waves, and a down converter 84 for converting the horizontal polarization waves and the vertical polarization waves separated by the polarization separator 1 for individual channels by frequency conversion and supplying signals obtained by the frequency conversion to a television tuner not shown. Various polarization separators are conventionally employed for the polarization separator 1 in such an antenna for receiving the CS broadcasting as shown in FIG. 8 or a parabola antenna for receiving the ASTRA broadcasting. An exemplary one of such conventional polarization separators is shown in FIGS. 1 and 2A to 2C. FIG. 1 is a perspective view of the conventional polarization separator, and FIGS. 2A to 2C are a front elevational view, a longitudinal sectional view and a top plan view, respectively, of the conventional polarization separator. Referring first to FIG. 1, the polarization separator shown includes a substantially tubular member 1 and separates orthogonal polarization waves received by a CS broadcasting reception antenna or an ASTRA broadcasting reception antenna into a horizontal polarization wave component H and a vertical polarization wave component V. The tubular member 1 has a circular waveguide 4 formed therein for propagating the orthogonal polarization waves therein. The circular waveguide 4 has a flange 2 to which the primary horn 83 shown in FIG. 8 is securely connected. A plurality of through-holes 3 are formed in the flange 2, and bolts not shown for securing the primary horn 83 shown in FIG. 8 are fitted in the through-holes 3. The tubular member 1 further has a rectangular opening 5 formed therein. The rectangular opening 5 has a major side in the direction of an axis of the circular waveguide 4 and serves as a horizontal polarization wave output terminal from which the separated horizontal polarization wave component H is extracted. A reflection plate 6 is located in the inside of the circular waveguide 4 and reflects only the horizontal polarization wave component H. The tubular member 1 further has a vertical polarization output terminal 7 from which the vertical polarization wave component V is extracted. Orthogonal polarization waves received by the CS broadcasting reception antenna or ASTRA broadcasting reception antenna are introduced in the directions of orthogonal arrow marks V and H shown in FIG. 1 into the tubular member 1 of the polarization separator by way of the primary horn 83. When the orthogonal polarization waves propagate in the circular waveguide 4 and reach the reflection plate 6 as indicated by arrow marks in FIG. 1, the horizontal polarization wave component H of the orthogonal polarization waves is reflected by the reflection plate 6 placed horizontally in the circular waveguide 4 so that it is outputted as indicated by an arrow mark H in FIG. 1 from the output terminal 5 in the form of a rectangular opening having a major side in the direction of the axis of the circular waveguide 4. Meanwhile, the vertical polarization wave component V of the orthogonal polarization waves is not reflected by the reflection plate 6 since it is orthogonal to the reflection plate 6. Consequently, the vertical polarization wave component V propagates straightforwardly in the circular waveguide 4 and is outputted as indicated by an arrow mark V in FIG. 1 from the output terminal 7 of the circular waveguide 4. It is to be noted that, since the output terminal 5 in the form of a rectangular opening has a cutoff structure (this will be hereinafter described) as viewed from the vertical polarization wave component V, the vertical polarization wave component V is not outputted from the output terminal 5. As can be recognized from the structure described above, the conventional polarization separator separates orthogonal polarization waves into a horizontal polarization wave component H and a vertical polarization wave component V while the orthogonal polarization waves propagate in the polarization separator. Further, in the polarization separator, propagation of the horizontal polarization wave component H toward the output terminal 7 is prevented by the reflection plate 6 which reflects the horizontal polarization wave component H in principle. Therefore, in order to sufficiently suppress the horizontal polarization wave component H from leaking to the output terminal 7 to assure a high separation efficiency of the polarization separator, the reflection plate 6 is formed long so as to increase the reflection efficiency of it. Prior art document PATENT ABSTRACTS OF JAPAN vol. 13, no. 216 (E-760) (3564), 19 May 1989, discloses a high frequency polarizer, wherein a circular wave guide is followed by rectangular wave guide, said circular waveguide having a slit at a top portion thereof. Further, prior art document PATENT ABSTRACTS OF JAPAN vol. 9, no. 144 (E-122) (1022), 3 August 1982, describes a feeding device for a circular polarized wave, wherein a metallic post is provided for reflecting only X components of signals. SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarization separator which is reduced in lenght without deteriorating the separation efficiency to achieve minimization and recuction in cost. It is another object of the present invention to provide a polarization separator wherein possible disorder of the distribution of an electromagnetic field in the proximity of an opening of the polarization separator at an output terminal of a polarization wave component reflected by reflection means is suppressed to allow impedance matching at the output terminal to be established readily to enhance the separation efficiency. It is a further object of the present invention to provide a polarization separator which is formed as a unitary member together with a converter to facilitate production and assembly of the polarization separator and the converter. It is a still further object of the present invention to provide a polarization separator which prevents electromagnetic waves from leaking to the outside through a joining location between a second circuit board of a multi-layer circuit board assembly and a waveguide member. In order to attain the objects described above, the present invention provides a polarization separator as defined in claim 1 or 2. Preferred embodiment of the invention are described in the subclaims. A preferred polarization separator for a microwave apparatus comprises a substantially tubular member having a circular waveguide formed therein for receiving input orthogonal polarization electromagnetic waves, a first rectangular hole formed in a side wall thereof, a second rectangular hole formed in a portion thereof remote from the portion at which the input orthogonal polarization electromagnetic waves are received, and a rectangular waveguide formed therein and extending between the circular waveguide and the second rectangular hole, and a reflecting pole located in the circular waveguide and having an axis extending perpendicularly to a direction in which the input orthogonal polarization electromagnetic waves propagate and also to a direction of a line along which the first rectangular hole and the center of the circular waveguide lie. With the polarization separator for a microwave apparatus, since reflection means for reflecting one of input orthogonal polarization waves is formed from the reflecting pole which may be in the form of a metal bar or rod such as, for example, a machine screw, the polarization separator can be produced with a minimized size and at a reduced cost. Another preferred polarization separator for a microwave apparatus comprises a substantially tubular member having a circular waveguide formed therein for receiving input orthogonal polarization electromagnetic waves, a first rectangular hole formed in a side wall thereof, a second rectangular hole formed in a same plane in the same side wall thereof, and a rectangular waveguide formed therein and extending between the circular waveguide and the second rectangular hole, and a reflecting pole located in the circular waveguide and having an axis extending perpendicularly to a direction in which the input orthogonal polarization electromagnetic waves propagate and also to a direction of a line along which the first rectangular hole and the center of the circular waveguide lie. Also with the polarization separator for a microwave apparatus, since reflection means for reflecting one of input orthogonal polarization waves is formed from the reflecting pole which may be in the form of a metal bar or rod such as, for example, a machine screw, the polarization separator can be produced with a minimized size and at a reduced cost. Preferably, dimensions of height and width of the rectangular waveguide are determined such that the rectangular waveguide has a cutoff frequency higher than that of a first one of the input orthogonal polarization electromagnetic waves but lower than that of a second one of the input orthogonal polarization electromagnetic waves. In this instance, preferably the polarization separator for a microwave apparatus further comprises an iris fitted in at least one of the first and second rectangular holes and having an opening formed therein, the opening of the iris being smaller than the first and/or second rectangular holes. Since the iris suppresses otherwise possible disorder of the distribution of an electric field of a vertical polarization wave component, leakage of an undesired polarization wave component can be prevented, and consequently, a high separation efficiency of the polarization separator can be assured. A preferred microwave apparatus comprises a substantially tubular member having a circular waveguide formed therein for receiving input orthogonal polarization electromagnetic waves, a first rectangular hole formed in a side wall thereof, a second rectangular hole formed in a same plane in the same side wall thereof, and a rectangular waveguide formed therein and extending between the circular waveguide and the second rectangular hole, a reflecting pole located in the circular waveguide and having an axis extending perpendicularly to a direction in which the input orthogonal polarization electromagnetic waves propagate and also to a direction of a line along which the first rectangular hole and the center of the circular waveguide lie, the tubular member and the reflecting pole constituting a polarization separator, a circuit board, a pair of waveguide-microstrip line mode transformers located on the circuit board corresponding to locations of the first and second rectangular holes, and a cover for covering over the first and second rectangular holes and holding the circuit board thereon. With the microwave apparatus, since the polarization separator is formed as a unitary member together with a converter which is constituted from the circuit board, waveguide-microstrip line mode transformers and cover, the microwave apparatus can be produced and assembled readily. The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference characters. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a conventional polarization separator; FIGS. 2A, 23 and 2C are a front elevational view, a side elevational sectional view and a top plan view, respectively, of the polarization separator shown in FIG. 1; FIG. 3 is a perspective view of a polarization separator to which the present invention is applied; FIGS. 4A, 4B, 4C and 4D are a front elevational view, a side elevational sectional view, a top plan view and a rear elevational view, respectively, of the polarization separator shown in FIG. 3; FIG. 5 is a perspective view of another polarization separator to which the present invention is applied; FIGS. 6A, 6B and 6C are a front elevational view, a side elevational sectional view and a top plan view, respectively, of the polarization separator shown in FIG. 5; FIG. 7A is a top plan view of a further polarization separator to which the present invention is applied, and FIG. 7B is a sectional view taken along line A-A' of FIG. 7A FIG. 8 is a schematic view showing an antenna which can receive orthogonal polarization waves such as a CS signal reception antenna; FIG. 9 is a schematic perspective view showing a rectangular waveguide member; FIG. 10 is an exploded view of a case of a converter to which the present invention is applied; FIG. 11 is a schematic view showing a circuit board of the converter shown in FIG. 10; FIGS. 12A and 12B are sectional views showing the converter of FIG. 10 before and after a polarization separator is assembled to the converter, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 3 and 4A to 4D, there is shown a polarization separator to which the present invention is applied. The polarization separator includes a substantially tubular member 1. The tubular member has a circular waveguide 4 formed therein in which the orthogonal polarization waves propagate. The tubular member 1 has a flange 2 having a plurality of through-holes 3 formed therein. The tubular member 1 further has a rectangular opening 5 formed therein. The construction of the polarization separator described above is similar to that of the conventional polarization separator described hereinabove with reference to FIG. 1, and accordingly, further overlapping description of the common construction is omitted herein to avoid redundancy. The polarization separator further includes a metal pole 8 for reflecting a horizontal polarization wave component H. The tubular member 1 further has a waveguide 9 formed therein by drawing upper and lower portions of the inner portion of the tubular member 1 so as to have a cross section of such a substantially rectangular shape as seen in FIG. 4D. The tubular member 1 further has an offset or step 10 for changing the circular inside section of the circular waveguide 4 into the rectangular inside section of the waveguide 9. The tubular member 1 has an output terminal 11 for extracting a vertical polarization wave component V therefrom. It is to be noted that, in FIG. 3, arrow marks accompanied by characters H and V denote horizontal and vertical polarization wave components, respectively. Orthogonal polarization waves received by a parabola antenna not shown are inputted as indicated orthogonal arrow marks in FIG. 3 into the circular waveguide 4 by way of a primary horn not shown (primary horn 83 shown in FIG. 8) and then propagate in the circular waveguide 4. When the orthogonal polarization waves propagate to the metal pole 8 in the circular waveguide 4 as indicated by arrow marks in FIG. 3, since a horizontal polarization wave component H of the orthogonal polarization waves is parallel to the metal pole 8, it is reflected by the metal pole 8 so that it is thereafter outputted as indicated by an arrow mark from the output terminal 5 which is a rectangular opening having a major side in the direction of the axis of the tubular member 1. Meanwhile, since a vertical polarization wave component V is perpendicular to the metal pole 8, it is not reflected by the metal pole 8 and consequently continues to propagate in the circular waveguide 4. Thus, the vertical polarization wave component V passes by the offset 10 and then propagates in the substantially rectangular waveguide 9 so that it is thereafter outputted as indicated by an arrow mark from the output terminal 11 of the tubular member 1. It is to be noted that the cutoff frequency fc of a rectangular waveguide is given, where, as shown in FIG. 9, the width of the rectangular waveguide of a waveguide member 91 is represented by a, by the following equation (1): fc = C/2a where C is the velocity of light. The width a of the substantially rectangular waveguide 9 of the tubular member 1 of the polarization separator shown in FIGS. 3 and 4A to 4D is set so that the frequency fv of the vertical polarization wave component may be higher than the cutoff frequency fc given by the equation (1) above. Meanwhile, for the horizontal polarization wave component H, the cutoff frequency fc is calculated in accordance with the equation (1) with the width a substituted for b since the side of the length a of the waveguide 9 extends in parallel to the direction of the electric field of the horizontal polarization wave component H. Accordingly, the cutoff frequency fc of the waveguide 9 is high and the frequency fh of the horizontal polarization wave component H is lower than the cutoff frequency fc, and consequently, the horizontal polarization wave component H cannot propagate across the step 10 and accordingly will not leak to the output terminal 9 at all. It is to be noted that the frequency fv of the vertical polarization wave component V and the frequency fh of the horizontal polarization wave component H in the waveguide are equal frequencies to each other of, for example, 12 GHz. Where the waveguide 9 for introducing only the vertical polarization wave component V which is not reflected by the metal pole 8 is constructed in a cutoff structure for the horizontal polarization wave component H, the horizontal polarization wave component H can be reflected sufficiently not by such a long reflecting member having a considerable width as the reflection plate 6 but only by the metal pole 8. In other words, in the polarization separator to which the present invention is applied, since the reflection means can be formed from an elongated bar-like metal pole, the circular waveguide 4 can be made short and the entire polarization separator 1 can be minimized. It is to be noted that, while the location of the metal pole 8 must be a little rearwardly of the center as viewed from the opening of the output terminal 5, if the location of the metal pole 8 is adjusted finely or the size of the circular waveguide 4 is varied, then the frequency characteristic of the polarization separator varies, and accordingly, the location of the metal pole 8 should be determined so that a desired characteristic may be obtained taking them into account. The metal pole 8 can be formed, for example, by screwing a long screw into the circular waveguide 4, which facilitates production and fixation of the reflection means. Referring now to FIGS. 5 and 6A to 6C, there is shown another polarization separator to which the present invention is applied. The present polarization separator is a modification to the polarization separator described hereinabove with reference to FIGS. 3 and 4A to 4D, and only differences of it will be described while description of common components is omitted herein to avoid redundancy. In the present polarization separator, an iris 12 is provided for restricting the opening of the output terminal 5 of the tubular member 1 for the horizontal polarization wave component H. The tubular member 1 is ground flat at an outer side portion thereof to form a flat face portion 13 which facilitates extraction of an output of the polarization separator. The waveguide 9 is bent at a corner 14 for reflecting the propagation direction of the vertical polarization wave component V in order to dispose an output terminal 15 for the vertical polarization wave component V on the same plane as the output terminal 5 for the horizontal polarization wave component H. In the polarization separator described hereinabove with reference to FIGS. 3 and 4A to 4D, the opening of the output terminal 5 for the horizontal polarization wave component H is large, and due to the construction, the electric field of the vertical polarization wave component V is disordered in distribution at the location of the opening so that a reflected wave which returns to the input terminal is produced or an undesired polarization wave component leaks to the output terminal, resulting in obstruction to enhancement of the separation efficiency. Therefore, in the polarization separator shown in FIGS. 5 and 6A to 6C, the iris 12 is provided in the opening of the output terminal 5, through which the horizontal polarization wave component H is outputted, to restrict the opening. As seen in FIGS. 5 and 6A to 6C, the iris 12 has a substantially rectangular opening which is rounded at the opposite ends thereof so as to exhibit a generally elliptical shape as seen in FIG. 6C, and the area of the opening of the iris 12 is a little smaller than the area of the opening of the output terminal 5. Consequently, by locating the iris 12 in the opening of the output terminal 5, the opening area at the boundary between the output terminal 5 and the circular waveguide 4 is narrowed so that otherwise possible disorder of the electromagnetic field of the vertical polarization wave component V in the opening area of the output terminal 5 can be suppressed. Further, in the polarization separator 1 shown in FIGS. 5 and 6A to 6C, the waveguide 9 for the vertical polarization wave component V is bent at the corner 14 thereof so as to bend the propagation direction of the vertical polarization wave component V upwardly so that the output terminal 15 for the vertical polarization wave component V is provided at the flat face portion 13 which is formed by grounding an outside portion of the tubular member 1 flat and lies in the same plane as the output terminal 5 for the horizontal polarization wave component H. This construction allows outputs of the vertical polarization wave component V and the horizontal polarization wave component H to be extracted from the same plane, and consequently, extraction means for the horizontal polarization wave component H and the vertical polarization wave component V can be formed as a unitary member and placed on the flat face portion 13 of the circular waveguide 4. Accordingly, for example, it is easy to supply the outputs of the two polarization wave components to different function circuits provided on a common circuit board. By the way, in the polarization separator 1 shown in FIGS. 5 and 6, since the iris 12 is provided, disorder of the electromagnetic field in the proximity of the opening from which the horizontal polarization wave component H is extracted can be prevented, but since the impedance varies suddenly at the location of the iris 12, it sometimes difficult to establish impedance matching with a circuit following the same. FIGS. 7A and 7B show a waveguide-microstrip line mode transformer which is a modification to the waveguide-microstrip line mode transformer described above with reference to FIGS. 6A to 6C and is modified such that impedance matching can be established readily while the iris 12 is provided. Thus, only differences of it will be described while description of common components is omitted herein to avoid redundancy. Referring to FIGS. 7A and 7B, the waveguide-microstrip line mode transformer shown additionally includes a probe 16 disposed in the proximity of the iris 12 and formed from a microstrip line for extracting and supplying a horizontal polarization wave component H to the converter 84 (FIG. 8), another probe 17 disposed in the proximity of the output terminal 11 and formed from another microstrip line for extracting and supplying a vertical polarization wave component V, and a metal lid member 20 placed on the flat face portion 13, on which the output terminals 5 and 11 of the polarization separator 1 are provided, and having hollows formed on a face thereof opposing to the flat face portion 13 for defining spaces from which the horizontal polarization wave component H and the vertical polarization wave component V are extracted. It is to be noted that FIG. 7A shows the flat face portion 13 with the lid member 20 removed, and FIG. 7B is a sectional view taken along line A-A' of the polarization separator 1 shown in FIG. 7A. In the waveguide-microstrip line mode transformer shown in FIGS. 7A and 7B, the horizontal polarization wave component H reflected by the metal pole 8 propagates through the iris 12 to the output terminal 5. The horizontal polarization wave component H then propagates in a space defined by the output terminal 5 and one of the hollows of the lid member 20 and is received by the probe 16 which is located in the space. The probe 16 is constituted from part of the microstrip line of the converter 84 described hereinabove, and consequently, the horizontal polarization wave component H received by the probe 16 is supplied from the probe 16 to the converter 84 by way of the microstrip line. The input impedance to the converter 84 can be adjusted readily by varying the configuration of the probe 16. Accordingly, by employing such probe 16, impedance matching between the waveguide and the converter 84 can be established readily. It is to be noted that the vertical polarization wave component V propagates along the corner 14 of the waveguide 9 and is outputted from the output terminal 15, whereafter it is received by the other probe 17 located in the other space defined by the output terminal 15 and the other hollow of the lid member 20 and is then supplied to another input terminal of the converter 84. Referring now to FIG. 10, there is shown a structure according to the present invention wherein a polarization separator and a shield case of a converter are formed as a unitary member. The converter is generally denoted at 100 while the polarization separator is generally denoted at 101. The polarization separator 101 separates orthogonal polarization waves received by a parabola antenna not shown in FIG. 10 into vertical polarization waves and horizontal polarization waves. A shield case 102 is provided for shielding such circuits as amplifiers and mixers mounted on a circuit board 105. The polarization separator 101 includes a rectangular waveguide 103 having an end portion from which separated horizontal polarization waves H are outputted and another rectangular waveguide 104 having an end portion from which separated vertical polarization waves are outputted. The circuit board 105 further has a probe 106 for receiving horizontal polarization waves and another probe 107 for receiving vertical polarization waves. A shield cover 108 serves as a lid for the shield case 100, and a waterproof case 109 is used to protect the elements in the shield case 100 from water. As seen in FIG. 10, the converter 100 is formed as a unitary member by molding of a metal such as aluminum and including the shield case 102 and the polarization separator 101, and orthogonal polarization waves including a horizontal polarization wave component and a vertical polarization wave component are introduced into the polarization separator 101. The horizontal polarization wave component separated by the polarization separator 101 is outputted from the waveguide 103 while the separated vertical polarization wave component is outputted from the waveguide 104. A stepped portion 102a is formed on an inner circumferential face of the shield case 102, and the circuit board 105 is mounted as indicated by an arrow mark in FIG. 10 such that peripheral portions of the circuit board 105 are received by the stepped portion 102a. The circuit board 105 is constituted from a double-sided printed circuit board formed from, for example, a glass epoxy resin plate. The probe 106 for extracting horizontal polarization waves, the other probe 107 for extracting vertical polarization waves, amplifiers, mixers and various other electric circuits are incorporated in the printed circuit board and connected to each other by way of microstrip lines. When the circuit board 105 are placed in position on the stepped portion 102a of the shield case 102, the probes 106 and 107 provided on the circuit board 105 are positioned at end portions of the waveguides 103 and 104, respectively. If the circuit board 105 is mounted onto the shield case 102 and then the shield case 102 is covered with the shield cover 108 as indicated by an arrow mark in FIG. 10, then the end portions of the waveguides 103 and 104 are terminated by respective hollows formed on the shield cover 108 while the circuit board 105 is held between and fixed by the end portions of the waveguides 103 and 104 and the shield cover 108. Further, since the circuit board 105 is accommodated in a space defined by and between the shield case 102 and the shield cover 108, it is electromagnetically shielded and will not allow leakage of disturbing waves. Meanwhile, when it is intended to protect the converter 100 from water, the shield cover 108 should be covered with the waterproof case 109. An example of the circuit board 105 is shown in FIG. 11. Referring to FIG. 11, the probes 106 and 107 are formed from printed wires on the circuit board 105, and also microstrip lines 51, 53, 56 and 57 are formed from printed wires on the circuit board 105. Amplifier FETs (field effect transistors) 52 and 54 are soldered to the microstrip lines 51, 53, 56 and 57. The probe 106 receives horizontal polarization waves from an end portion of the waveguide 103, and the other probe 107 receives vertical polarization waves from an end portion of the waveguide 104. A plurality of through-holes 50 are formed for a grounding line 55 around the probes 106 and 107. A vertical polarization signal propagates in the microstrip lines 51 and 56 and is amplified by the FET 52 while a horizontal polarization signal propagates in the microstrip lines 53 and 57 and is amplified by the FET 54. In the circuit board 105 shown in FIG. 11, a horizontal polarization signal received by the probe 106 located at the end portion of the waveguide 103 propagates in the microstrip line 53 and is then amplified by the FET 54, whereafter it is outputted to the microstrip line 57 connected to a mixer not shown. Then, the frequency of the horizontal polarization signal is converted by down conversion into a signal of an intermediate frequency. Meanwhile, a vertical signal received by the probe 107 located at the end portion of the waveguide 104 propagates in the microstrip line 51 and is then amplified by the FET 52, whereafter it is outputted to the microstrip line 56 connected to another mixer not shown. Then, the frequency of the vertical polarization wave component is converted by down conversion into a signal of an intermediate frequency. The through-holes 50 perforated around the probes 106 and 107 connect a grounding line on the front face and another grounding line on the rear face of the printed circuit board 105 to each other. The through-holes 50 are arranged such that they surround printed wiring portions blanked in substantially same shapes as the shapes of cross sections of the waveguides 103 and 104 so that vertical and horizontal polarization signals may not leak from the locations. Preferably, the distance between the through-holes 50 is set so that it may be smaller than a cutoff frequency of electromagnetic waves outputted from the waveguides 103 and 104. Where the through-holes 50 are provided in this manner, the characteristic of the waveguide-microstrip line mode transformer can be improved as hereinafter described. Referring now to FIGS. 12A and 12B, the circuit board 105 is shown held between the polarization separator 101 provided integrally on the shield case 102 and the shield cover 108. In particular, FIG. 12A shows in cross sectional view an arrangement of the circuit board 105 disposed in an opposing relationship to the end portion of the waveguide 104 and the shield case 108 disposed in an opposing relationship to the circuit board 105, and FIG. 12B shows the circuit board 105 held between and fixed by the end portion of the waveguide 104 and the shield case 108. The shield cover 108 has a hollow 60 formed thereon for terminating the waveguide 104. The hollow 60 has a depth of λ/4 and is defined by a projection 61 formed on the shield cover 108. The circuit board 105 is held between and fixed by the polarization separator 101 and the shield cover 108, which are fastened together by means of a plurality of machine screws 62. It is to be noted that a grounding pattern 58 is formed on the rear face of the circuit board 105. In assembly, the polarization separator 101, the circuit board 105 and the shield case 108 are disposed in such a condition as shown in FIG. 12A and then contacted with each other, and then the machine screws 62 are screwed to fasten the shield case 108 to the polarization separator 101. Consequently, the circuit board 105 is held between and fixed by the polarization separator 101 and the shield case 108 as shown in FIG. 12B. In the construction shown in FIG. 12B, since the end portion of the waveguide 104 of the polarization separator 101 is terminated by the hollow 60 of the depth of λ/4 of the shield case 108, a signal of a vertical polarization wave component can be extracted efficiently from the probe 107. The signal of the vertical polarization wave component propagates in the microstrip line 51 and is inputted to the FET 52. Consequently, the signal of the vertical polarization wave component is amplified by and outputted from the FET 52 to the microstrip line 56. Meanwhile, though not shown, a signal of a horizontal polarization wave component is received by the probe 106, amplified by the FET 54 and outputted to the microstrip line 57 similarly to the signal of the vertical polarization wave component. Where the polarization separator 101 is molded integrally with the shield case 102 of the converter 100 and the shield cover 108 is mounted as a lid member on the shield case 102 in this manner, the waveguide-microstrip line mode transformer can be constructed readily and minimized in loss. Further, the converter 100 is superior in cross polar characteristic.

Claims: A polarization separator for a microwave apparatus, comprising: a substantially tubular member (1) having a circular waveguide (4) formed therein for receiving input orthogonal polarization electromagnetic waves, a first rectangular hole (5) formed in a side wall thereof, a second rectangular hole formed as an output terminal at an end of said tubular member, and a rectangular waveguide (9) formed therein and extending between said circular waveguide and said second rectangular hole; characterized by a reflecting pole (8) located in said circular waveguide (4) and having an axis extending perpendicularly to a direction in which the input orthogonal polarization electromagnetic waves propagate and also to a direction of a line along which said first rectangular hole (5) and the center of said circular waveguide (4) lie. A polarization separator for a microwave apparatus, comprising: a substantially tubular member (1) having a circular waveguide (4) formed therein for receiving input orthogonal polarization electromagnetic waves, a first rectangular hole (5; 103) formed in a side wall thereof, a second rectangular hole (15; 104), and a rectangular waveguide (9) formed therein and extending between said circular waveguide (4) and said second rectangular hole (15); characterized in that said second rectangular hole (15) is formed in a same plane in the same side wall as said first rectangular hole (5), and a reflecting pole (8) is located in said circular waveguide (4) and has an axis extending perpendicularly to a direction in which the input orthogonal polarization electromagnetic waves propagate and also to a direction of a line along which said first rectangular hole (5) and the center of said circular waveguide (4) lie. A polarization separator for a microwave apparatus as claimed in claim 1 or 2, characterized in that said tubular member (1) and said reflecting pole (8) are made of a metal. A polarization separator for a microwave apparatus as claimed in any one of claims 1 to 3, characterized in that dimensions of height and width of said rectangular waveguide (9) are determined such that said rectangular waveguide (9) has a cutoff frequency higher than that of a first one of the input orthogonal polarization electromagnetic waves but lower than that of a second one of the input orthogonal polarization electromagnetic waves. A polarization separator for a microwave apparatus as claimed in claim 4, characterized in that a reflecting face (14) for changing the direction of propagation of the second electromagnetic wave in said rectangular waveguide (9) approximately by 90 degrees in said rectangular waveguide (9) is formed in said rectangular waveguide (9). A polarization separator for a microwave apparatus as claimed in claim 4 or 5, characterized by further comprising an iris (12) fitted in at least one of said first and second rectangular holes (5, 15) and having an opening formed therein, said opening of said iris (12) being smaller than said first and/or second rectangular holes (5, 15). A polarization separator for a microwave apparatus as claimed in claim 6, characterized in that said opening of said iris (12) has an elliptic shape. A polarization separator for a microwave apparatus as claimed in any one of claims 1 to 7, characterized in that said reflecting pole is a bolt (8). A microwave apparatus, comprising: a polarization separator (101) as defined in claim 2, a circuit board (105); a pair of waveguide-microstrip line mode transformers located on said circuit board corresponding to locations of said first and second rectangular holes; and a cover (108) for covering over said first and second rectangular holes and holding said circuit board thereon. A microwave apparatus as claimed in claim 9, characterized by further comprising a shield case (100) for covering over said polarization separator as well as an electric circuit on said circuit board including said waveguide-microstrip line mode transformers, and a waterproof case for covering said shield case and said cover. A microwave apparatus as claimed in claim 9 or 10, characterized in that said cover (108) has a pair of hollows formed thereon corresponding to said first and second rectangular holes (103, 104). A microwave apparatus as claimed in claim 11, characterized in that said hollows of said cover (108) have a depth substantially equal to one fourth of a wavelength of the input electromagnetic waves.

Inventors: FUKUZAWA KEIJI, HORISAWA SHOZO, KAWASAKI KENICHI, MITA HIROYUKI, YOSHIDA YOSHIKAZU, FUKUZAWA, KEIJI, HORISAWA, SHOZO, KAWASAKI, KENICHI, MITA, HIROYUKI, YOSHIDA, YOSHIKAZU, FUKUZAWA, KEIJI, C/O SONY CORPORATION, HORISAWA, SHOZO, C/O SONY CORPORATION, KAWASAKI, KENICHI, C/O SONY CORPORATION, MITA, HIROYUKI, C/O SONY CORPORATION, YOSHIDA, YOSHIKAZU, C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1993
Main classification: H01P1
IPC codes: H01P1, H01P5