Array antenna

Abstract: A radiowave receiving array antenna comprises a lower earthing conductor (1), an upper earthing conductor (3), supporting plates (4) for supporting a feeder circuit board (2) therebetween, radiation elements (7) and low noise amplifiers (5), wherein the low noise amplifiers are mounted on the feeder circuit board at spaces formed by thinning out a part of the radiation elements.

Description: The present invention relates to an array antenna for receiving signals in a microwave region. Figure 5 is a diagram showing a conventional radiowave receiving array antenna wherein reference numeral 1 designates a lower earthing conductor, numeral 2 designates a feeder circuit board, numeral 3 designates an upper earthing conductor, numerals 4 designate supporting plates, numerals 5 designate low noise amplifiers, numerals 6 designate power source lines for the low noise amplifiers, numeral 7 designates a number of radiation elements, numeral 8 designates a feeder circuit, numerals 9 designate a metal pins and numeral 10 designates a number of radiation windows. In the operation of the conventional array antenna, radiowaves received by the radiation elements 7 in the feeder circuit board are synthesized by the feeder circuit 2, the synthesized signal is amplified by the low noise amplifiers 5, and then, is supplied to a receiver. In the feeder circuit 2, a loss of electric energy produces noises, whereby the quality of an electric signal is deteriorated. When the a level of deterioration exceeds an allowable range, it is necessary to divide the antenna into sub-arrays and to insert the low noise amplifiers 5 in each sub-array. Namely, influence by a loss produced in the feeder circuit from the low noise amplifiers 5 to the output terminals of the antenna can be reduced in inverse proportion to the gain of the low noise amplifiers 5 by inserting a plurality of low noise amplifiers 5 in the feeder circuit 2. In order to insert the low noise amplifiers in the feeder circuit 2, it is necessary to mount the low noise amplifiers 5 on the back surface of the lower earthing conductor 1 and to connect the low noise amplifiers 5 to the feeder circuit 2 by using metal pins 9 or the like. The conventional radiowave receiving array antenna having the construction described above had disadvantages as follows. The structure for connecting the low noise amplifiers to the feeder circuit is complicated to thereby increase cost. Further, since the low noise amplifiers are mounted on the back surface of the lower earthing conductor, the thickness of the antenna device is increased. When the array antenna is to be prepared for outdoor use, a cover for protecting the low noise amplifiers is additionally needed, whereby the construction is further complicated to thereby increase cost. EP 0 055 324 A2 discloses a monolithic microwave circuit with array elements, a feed network and low noise amplifiers being integrated on a single substrate of semiconductor material. JP 1-114106 A describes a structure in which a portion corresponding to a feeding terminal on the earthing conductor protrudes towards the feed circuit board and an amplifier is attached to the top of the portion. In JP 1-114104 A and JP 1-114105 A a low noise amplifier is provided in the space between the earthing conductor and the feeder circuit board so as to be perpendicular or parallel to both the earthing conductor and the feeder circuit board, respectively. It is an object of the present invention to provide a radiowave receiving array antenna to suppress an increase of cost with respect to the mounting of the low noise amplifiers. This object is solved by the features of claim 1. In the present invention, connection of the low noise amplifiers to the feeder circuit can be easy because the low noise amplifiers are mounted on the same plane as the feeder circuit. The low noise amplifiers were generally formed on microstrip lines. Insertion of the converting device comprising a rectangular coaxial member between a triplate line and a microstrip line in the feeder circuit assures effective conversion and provides a simple and efficient structure. When the array antenna of the present invention is to be in outdoor use, the upper earthing conductor is covered by a radome. Accordingly, the low noise amplifiers can be mounted, without the necessity of an additional protecting means, by arranging the power source lines for the amplifiers on the upper earthing conductor. The power source lines for the upper earthing conductor and the low noise amplifiers are formed, by etching or the like, on both surfaces of a double-side-metal-sheet-lined substrate, whereby the number of elements can be reduced so that the manufacturing cost can be reduced. In drawings: Figure 1a is a perspective view partly removed of an embodiment of the radiowave receiving array antenna according to the present invention; Figure 1b is a longitudinal cross-sectional view in an enlarged scale of the array antenna shown in Figure 1a; Figure 2a is a longitudinal cross-sectional view partly broken in an enlarged scale of another embodiment of the radiowave receiving array antenna according to the present invention; Figure 2b is an enlarged vertical cross-sectional view of the array antenna shown in Figure 2a; Figure 3a is a perspective view partly removed of another embodiment of the radiowave receiving array antenna of the present invention; Figure 3b is a longitudinal cross-sectional view partly broken in an enlarged scale of the array antenna shown in Figure 3a; Figure 4a is a perspective view of another embodiment of the radiowave receiving array antenna according to the present invention; Figure 4b is a longitudinal cross-sectional view partly broken in an enlarged scale of the array antenna shown in Figure 4a; Figure 5a is a perspective view of a conventional radiowave receiving array antenna; and Figure 5b is a longitudinal cross-sectional view in an enlarged scale of the array antenna shown in Figure 5a. The following, preferred embodiments of the radiowave receiving array antenna according to the present invention will be described with reference to the drawings. Figure 1, reference numeral 1 designates a lower earthing conductor or a lower earthing conductive plate, numeral 2 designates a feeder circuit board comprising an insulating film on which a feeder circuit is formed, numeral 3 designates an upper earthing conductor or an upper earthing conductive plate made of a metallic substance, numerals 4 designate first and second supporting plates made of a foamed resinous material, numeral 5 designate low noise amplifiers, numeral 7 designate a number of radiation elements formed on the insulating film which is overlaid on the first supporting plate 4, numeral 8 designates the feeder circuit, numeral 10 designate a number of radiation windows formed in the upper earthing conductor 3. The feeder circuit board 2 is sandwiched between the first and second supporting plates 4; the upper earthing conductor 3 is overlaid on the other surface of the first supporting plate 4 and the lower earthing conductor 1 is overlaid on the other surface of the second supporting plate 4. In Figure 1, the low noise amplifiers 5 are mounted on the same plane as the feeder circuit board 2. In comparison with the conventional technique wherein the low noise amplifiers are mounted on the back surface of the lower earthing conductor 1 (Figure 5), it is unnecessary to provide means for connecting the low noise amplifiers 5 to the feeder circuit 8, on the lower earthing conductor 1. Further, it is unnecessary to provide a cover for protecting the low noise amplifiers 5. In order to mount the low noise amplifiers on the same plane as the feeder circuit board 2, it is necessary to create spaces by sacrificing a part of the radiation elements 7. However, if the number of the radiation elements is sufficiently large, the deterioration of the characteristics of the antenna due to the reduction of the number of the radiation elements is negligible. In this respect, more detailed description will be made. The gain G of an array antenna is expressed by the following formula: G = G e + 10 log N + η - L (dB) where G is the gain of elements, N is the number of elements, η is opening efficiency (<0) and L is current feeding loss (>0). Accordingly, a change of gain ΔG caused by reducing a part of radiation elements is expressed by the following formula: ΔG = 10 log (N 1 /N 2 ) where N₁ is the number of elements after reducing some elements and N₂ is the number of elements before the reducing of the number of the elements. If the tolerance of ΔG is determined to be -0.2 dB or less, then N₁/N₂ ≐ 0.955. Namely, when there is an antenna having N₂ = 100, it is possible to reduce 4 radiation elements. Figure 2 shows another embodiment of the array antenna according to the present invention. In Figure 2, the same reference numerals as in Figure 1 designate the same element, and therefore, description of these elements is omitted. In Figure 2, reference numeral 11 designates a rectangular coaxial type inner conductor, numeral 12 designates a rectangular coaxial type outer conductor, numeral 13 designates a microstrip line for a low noise amplifier, and numeral 14 designates an earthing conductor for the microstrip line 16. In the embodiment shown in Figure 2, the rectangular coaxial type inner and outer conductors 11, 12 constitutes a converting device. The insertion of the converting device between the microstrip line and a triplate line suppresses the deterioration of efficiency of transmitting electromagnetic waves. The deterioration of the transmission efficiency is caused because the microstrip line forms an imbalance type transmission path and the triplate line forms a balance type transmission path, and therefore, if the both lines are directly connected, imbalanced, undesired electromagnetic waves are produced at the connection area so as to keep the continuity of electric field, to thereby deteriorate the transmission efficiency. The rectangular coaxial type converting device forms a balance type transmission path. When the converting device is inserted between the microstrip line and the triplate line, electromagnetic waves produced at the connection area is of a waveguide mode because the connection area is entirely surrounded by a metallic substance. In the embodiment as shown in Figure 2, the converting device comprising rectangular coaxial type inner and outer conductors is inserted in a converting section where there are the microstrip line 13 for a low noise amplifier and the triplate line in the feeder circuit 8, wherein the dimension of the longer inner side of the outer conductor is determined to be able to cut off a waveguide mode at an available frequency. The cut-off frequency of the waveguide mode is given by the formula: f = c/(2a), where f is cut-off frequency, c is the velocity of light and a is the dimension of longer inner side of the outer conductor. In the above-formula, the deterioration of the transmission efficiency can be controlled by determining the value of f to be higher than a frequency used. Accordingly, occurrence of useless mode can be suppressed with a simple structure, and conversion can be effectively done. Figure 3 shows another embodiment of the antenna array according to the present invention. In Figure 3, the same reference numerals as in Figure 1 designate the same elements except that the array antenna of this embodiment has a radome 15. The radome 15 is generally attached to an array antenna for outdoor use. Accordingly, by arranging the power source lines 6 for the low noise amplifiers between the upper earthing conductor 3 and the radome 15, it is unnecessary to provide an additional protecting means for the power source lines 6. Figure 4 shows another embodiment of the array antenna according to the present invention. In Figure 4, the same reference numerals as in Figure 1 designate the same or corresponding elements except that numeral 9 designate metal pins and numeral 16 designates a double-side-metal-sheet-lined substrate. In the embodiment shown in Figure 4, the upper earthing conductor 3 and the power source lines 6 are formed, by etching or the like, on both surfaces of a single double-side-metal-sheet-lined substrate, whereby the number of structural elements can be further reduced. Thus, in accordance with the present invention, low noise amplifiers are mounted on the same plane as a feeder circuit, or power source lines are arranged on the upper earthing conductor, whereby the construction of an array antenna can be simplified and the manufacturing cost can be reduced.

Claims: A radiowave receiving array antenna comprising a lower earthing conductive plate (1), a first supporting plate (4) made of a foamed resinous material which is overlaid on the lower earthing conductive plate, a feeder circuit board (2) comprising a feeder circuit (8) and radiation elements (7) formed on an insulating film which is overlaid on the first supporting plate (4), a second supporting plate (4) made of a foamed resinous material which is overlaid on the feeder circuit plate (2), an upper earthing conductive plate (3) made of a metallic substance, overlaid on the second supporting plate (4), in which radiation windows (10) are formed at positions corresponding to the radiation elements and low noise amplifiers (5), characterized in that said low noise amplifiers (5) are mounted on spaces formed by thinning out a part of the radiation elements (7) on the feeder circuit board (2). A radiowave receiving array antenna according to claim 1, characterized in that said low noise amplifiers (5) are mounted on microstrip lines (13) at spaces formed by thinning out a part of the radiation elements on the feeder circuit board, and a converting device (11, 12) formed of rectangular coaxial members is inserted between a microstrip line (13) and a triplate line of the feeder circuit (8). A radiawave receiving array antenna according to claim 1 or 2, characterized in that a power source line (6) for the low noise amplifiers (5) is formed on the upper earthing conductive plate (3). A radiowave receiving array antenna according to claim 1, 2 or 3, characterized in that said upper earthing conductive plate (3) is arranged at the lower surface of a double-side-metal-sheet-lined substrate (16); and a power source line (6) for the low noise amplifiers (5) is formed on said substrate (16).

Inventors: CHATANI YOSHIYUKI, FUNADA MASAHIKO, HARADA AKIRA, HIGA MORIO, HURUNO TAKAYOSHI, MASUJIMA TOSHIO MITSUBISHI DEN, NISHIOKA YASUHIKO, ORIME NOBUTAKE, CHATANI, YOSHIYUKI, FUNADA, MASAHIKO, HARADA, AKIRA, HIGA, MORIO, HURUNO, TAKAYOSHI, MASUJIMA, TOSHIO, NISHIOKA, YASUHIKO, ORIME, NOBUTAKE, CHATANI, YOSHIYUKI, MITSUBISHI DENKI K.K., FUNADA, MASAHIKO, MITSUBISHI DENKI K.K., HARADA, AKIRA, MITSUBISHI DENKI K.K., HIGA, MORIO, MITSUBISHI DENKI K.K., HURUNO, TAKAYOSHI, MITSUBISHI DENKI K.K., MASUJIMA, TOSHIO, MITSUBISHI DENKI K.K., NISHIOKA, YASUHIKO, MITSUBISHI DENKI K.K., ORIME, NOBUTAKE, MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1992
Main classification: H01Q1
IPC codes: H01Q23, H01P5, H01Q21, H01Q13, H01Q1