Array antenna apparatus

Abstract: Array antenna apparatus can form a beam in plural directions by changing the electrical supply track length between antenna elements of array antennas so that a beam of the same form but a different inclinati on angle is formed by each array antenna. Each array antennas can be arb itrarily selected switch circuit, and a supplied transmitted signal, and enables forming a beam in different directions alternatively.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This invention relates to an array antenna apparatus which is suitable for use in a variety of applications including aircraft and artificial satellites. DESCRIPTION OF THE RELATED ART When performing a beam scan where the main part of antenna apparatus is fixed, although the beam scanning function for covering a large area in antenna apparatuses, such as in radar and communication applications, at high speed is required, array antenna apparatus which generally changes the excitation phase of two or more antenna elements is used. A conventional array antenna apparatus using the above-described method is explained with reference to Fig.9. Fig. 9 shows elements of the conventional array antenna apparatus for a radar application which changes an excitation phase, by equipping antenna elements with a phase shifter. The distribution composition apparatus 10 carries out an n (n is an integer) distribution of the transmitted signal supplied from a transmitting apparatus (not shown) at the time of transmission, and supplies it to the phase shifters 21-1,21-2, ···,21-n, respectively. The apparatus 10 also combines the received signals supplied from phase shifters 21-1, 21-2, ···,21-n at the time of reception, and outputs the combined result to a receiver ( not shown ). Phase shifters 21-1,21-2, ···,21-n perform phase control for an antenna beam scan, and they control the phase of the transmitted signal supplied from the distribution composition apparatus 10 at the time of transmission according to the value of a phase shift control signal from control equipment 40 described more fully below, and supply the transmitted signal to antenna elements 31-1,31-2, ··· ,31-n , respectively, for transmission. Phase shifters 21-1,21-2, ···,21-n also control the phase of the received signal supply from antenna elements 31-n at the time of reception, respectively , and supply it to the distribution composition apparatus 10 . While the antenna elements 31-1,31-2, ···,31-n emit to space the transmitted signal for which phase control was carried out by the phase shifters 21-1,21-2, ···,21-n, they can also receive the radar echo from an observed object, and supply it to the phase shifters 21-1, 21-2, ···, 21-n as a received signal , respectively. The control equipment 40 generates the phase shift control signal in accordance with a control signal, which is outputted to the phase shifters 21-1,21-2, ···,21-n, and controls phase shift. The conventional array antenna apparatus distributes the transmitted signal by means of the distribution composition apparatus 10 at the time of transmission, and carries out a beam scan of the target direction by performing phase control further at the phase shifters 21-1,21-2, ···,21-n . After the antenna elements 31-1,31-2, ···,31-n receive the radar echo from an observed object at the time of reception and carry out phase control by means of the phase shifters 21-1,21-2, ···,21-n the received signals are combined by the distribution composition apparatus 10 to obtain the received signal. However, with respect to the conventional array antenna apparatus having n antenna elements and phase shifters, since many phase shifters and associated control equipment were needed, there was a problem that the system was complicated and it was difficult to provide a miniaturized and lightweight construction of the conventional array antenna apparatus. There is also conventional array antenna apparatus which does not use phase shifters. In such array antenna apparatus an excitation phase is changed by changing the frequency of a transmitted signal. An example of such apparatus is shown in Fig. 10. The array antenna apparatus generally shown in Fig. 10 includes patch-like antenna elements distributed on the surface of a substrate 50. The antenna elements are connected in series to receive an electrical signal power supply by an electrical supply track 70, with the signals being supplied at one end of the track 70. An element of the array so connected, is supplied with signals provided by a frequency variable apparatus 80. That is to say, the phase adjustment in each antenna elements 61-1,61-2, ···,61-n is controlled by the frequency variable apparatus 80, and is made to form a beam in the target direction by changing the frequency of a transmitted signal. However, because there are restrictions on permissible frequency bands that can be used for the antenna elements 61-1,61-2, ···,61-n, with the conventional array antenna apparatus as described above, there was a problem that a beam inclination angle could not be selected arbitrarily by changing the frequency of a transmitted signal. Furthermore, it was difficult to suppress extraneous wave forms, and to change to rectangular polarization. The features of the preamble of claim 1 are known from US-A-5 189 433 SUMMARY OF THE INVENTION It is an object of the invention to overcome the above described deficiencies of conventional systems. In accordance with the invention there is provided array antenna apparatus having the features of claim 1. Advantageous embodiments are described in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a first array antenna apparatus not belonging to the invention. Fig. 2 illustrates a radiation pattern of each array antenna of the antenna apparatus of the first apparatus. Fig. 3 illustrates a second array antenna apparatus not belonging to the invention. Fig. 4 illustrates an example of a setting of the beam scanning range of each array antenna of the second apparatus. Fig. 5 illustrates array antenna apparatus not belonging to the invention. Fig. 6 illustrates a radiation pattern before antenna change control in the third apparatus. Fig. 7 illustrates a radiation pattern after antenna change control in the third apparatus. Fig. 8 illustrates an array antenna apparatus in accordance with an embodiment of the invention. Fig. 9 illustrates a conventional array antenna apparatus using phase shifters. Fig. 10 illustrates a conventional array antenna apparatus using a frequency variable apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Antenna systems and an embodiment of the invention will be explained with reference to the accompanying drawings. Fig. 1 illustrates an array antenna apparatus not belonging to the invention, and is adapted for use in a radar application. The array antenna apparatus of Fig. 1 comprises a control part 100 and an antenna part 200. The control part 100 includes a switch circuit 110. The antenna part 200 includes array antennas 241-244 to which switch circuit 110 is connected. Switch circuit 110 is coupled to receive a transmitted signal and a switch change signal supplied from a transmitting apparatus (not shown). In response, the switch circuit 110 outputs a transmitted signal to the array antennas 241-244 alternatively according to the switch change signal. Each of array antennas 241-244 comprises two or more antenna elements A distributed on the surface of a substrate 210. Each antenna element A is a patch that occupies a discrete limited area, having a predetermined shape, e.g. a square. The antenna elements A are formed of a dielectric and the substrate is an insulating material. Thus ,the antenna elements A arranged as the array antenna 241-244 on the substrate 210 form the antenna part 200. While antenna elements A emit a transmitted signal in to space, the radar echo from an observed object is received by the elements A. Electrical signal power is supplied to each antenna element by four electrical supply tracks 231-234 which connect the elements A of each array in series, thereby forming the four sets of array antennas 241-244. The ends of the electric-supply tracks 231-234 are connected to the switch circuit 110 of the control part 100 to receive electrical power. Moreover, although the array antennas 241-244 each form a beam of the same form as shown in Fig. 2, there is a different electric-supply track length between the antenna elements A for each array antenna, which results in a beam having an inclination angle which changes with the track length between elements. Hereafter, operation of the array antenna apparatus of the first apparatus is explained. The transmitted signal from a transmitting apparatus is supplied to one of the array antennas 241-244 chosen by the switch circuit 110 in accordance with the switch change signal, and is emitted in to space from each antenna element A. Since the beam inclination angle of each of array antennas 241-244 differs mutually, when selection of the array antennas 24 1-244 is switched, a beam will be alternatively formed in a different one of four directions. A received signal is generated from a radar echo from an observed object is processed in a reverse to that described for a transmitted signal. Therefore, according to the first array antenna apparatus, a beam can be alternatively formed in four different directions, without using phase shifters. Next, a second array antenna apparatus not belonging to this invention but describing the feature of claim 2 is described with reference to Fig. 3. In Fig. 3, elements that are the same as in Fig. 1 are identified by the same reference numerals, and an explanation of only the different features in Fig.3 is provided. The array antenna apparatus of Fig.3 comprises a control part 101 and the antenna part 200, the apparatus of Fig. 3 differs from that of Fig. 1 in the inclusion of the frequency variable apparatus 120 in the control part 101. The frequency of the transmitted signal from a transmitting apparatus (not shown) is changed arbitrarily, and the frequency variable apparatus 120 outputs the transmitted signal to the switch circuit 110. Hereafter, operation of the second array antenna apparatus is explained. Frequency is controlled by the frequency variable apparatus 120. The transmitted signal from the transmitting apparatus (not shown) is supplied through the apparatus 120 to the array antenna selected by the switch circuit 110, and is emitted to space from each antenna element A of the selected array antenna. Changing the frequency of the transmitted signal applied to the antenna elements A of the antenna array has the effect of changing the phase of the signal and thereby changing the direction of the beam that is formed, thus, there is a correspondence between frequency and phase. Here, if the array antenna 241 is chosen, for example, frequency is changed and a transmitted signal is supplied, since the phase of the transmitted signal in each antenna element A of the array antenna 241 changes, a beam inclination angle will change and, as a result, a beam scan will be performed. With respect to received signal generation from the radar echo from an observed object, the order operation is opposite to that carried out with transmission. Thus, with the second array antenna apparatus, a beam can be scanned within the limits of the array antennas 241-244, and carrying out the variable control of the frequency of a transmitted signal with the frequency variable apparatus 120. Moreover, a beam can be alternatively scanned in four directions by changing the above-mentioned switch circuit 110. Therefore, according to the second array antenna apparatus, the beam scan of two or more ranges can be carried out, without using phase shifters. Moreover, if the scanning ranges of the respective antennas 241-244 are arranged to provide a continuous range taken together as shown in Fig. 4, the total beam scan can include the range of a beam scans of each array antenna 241-244 when carried out in a continuous sequence. Next, a third array antenna apparatus not belonging to the invention but describing the feature of claim 3, is described with reference to Fig. 5. In Fig. 5, elements that are the same as in Fig. 1 are identified by the same reference numerals, and an explanation of only the different features in Fig.5 is provided. The features of the third array antenna apparatus include the control part 100 including switch circuit 110 and an antenna part 201 including array antennas 261-264. As in the case of the first apparatus, the elements of each of the array antennas 261-264 of the antenna part 201 are interconnected so that electrical signal power can be supplied in series on electric-supply tracks 251-254 to the antenna elements A distributed on the substrate 210. However, the electric-supply track between the antenna elements A is changed, respectively, and the array antenna 261 and the array antenna 262 arranged so that a different null point may be formed by each antenna, although a main beam of the same form including the same inclination angle is formed by each of antennas 261 and 262, as shown in Figs. 6 and 7. Similarly, the antenna elements A of the array antenna 263 and the array antenna 264 are arranged so that each antenna forms a different null point, although the main beam of the same form including the same inclination angle is formed by each of antennas 263 and 264. However, the array antennas 261,262 and the array antennas 263,264 are respectively set up so that the main beam is formed with a different inclination angle. Hereafter, the operation of the third array antenna apparatus is explained. The transmitted signal from a transmitting apparatus (not shown) is supplied to the array antenna chosen by the switch circuit 110 according to the switch change signal. As a result, a transmitted signal is emitted from the array antenna selected by the switch change signal, and a main beam is formed with an inclination angle beforehand set up by this. If the array antenna 261 and the array antenna 263 are switched alternatively for this reason, a beam can be formed in two directions. As for received signal generation from a radar echo or from an observed object, the order of processing is opposite to that carried out for the transmission. Here, when having received a radar echo, for example, using the array antenna 261 and an unnecessary electric wave occurs the apparatus on a side lobe of the array antenna 261 as shown in Fig. 6, switches to the array antenna 262 by means of the switch circuit 110. Thereby, as shown in Fig. 7, the unnecessary electric wave is hardly received, because the magnitude of the unnecessary wave is reduced by the null point of antenna 262. Therefore, according to the third array antenna apparatus, without using phase shifters, a beam can be formed in two different directions. Also if an unnecessary electric wave occurs on a side lobe direction of the selected array antenna apparatus, reception of the unnecessary electric wave can be reduced by switching to the array antenna having the same inclination angle of its main beam and a null point that differs in position. In addition, in the third apparatus, if it is modified to output a transmitted signal to the switch circuit 110 through the frequency variable apparatus 120 of the second apparatus, a beam scan with a reduction of unnecessary electric-wave reception will be attained by frequency control of the transmitted signal. Moreover, if it is made to continue the beam scanning range of each array antenna, it can scan cross broadly and a beam can be scanned continuously. Next, an array antenna apparatus of an embodiment of the invention is described to Fig. 8. In Fig.8, elements that are the same as a Fig. 1 are identified by the same reference numerals, and an explanation of only the different features of Fig. 8 is provided. The features of the array antenna apparatus of the embodiment of the invention include the control part 100 including the switch circuit 110 and an antenna part 202 including array antennas 281-284. The elements of the array antenna 281 and the array antenna 283 of the antenna part 202 are interconnected so that electrical signal power can be supplied in series on an electric-supply track 271 and an electric-supply track 273 to antenna elements A distributed on the substrate 210 as in the first apparatus. The elements of the array antenna 282 and the array antenna 284 are connected in parallel to receive electrical signal power and arranged so that electrical signal power may be supplied from a direction which is perpendicular to the direction of series connected electrical power supply. The array antenna 282,284 antenna elements A are distributed on th e substrate 210, respectively, on the electric-supply track 272 and the electric-supply track 274, respectively. Moreover, the array antenna 281 and the array antenna 282 are set up so that the beams by these polarizations may be formed on the same inclination square while generating polarizations which intersect perpendicularly mutually due to the above described electrical supply connections to the antennas. The array antenna 283 and the array antenna 284 are set up with the same relation as described for antennas 281 and 282. However, the group of the array antennas 281,282 and the group of the array antennas 283,284 are set up so that the beam of one group can be formed with an inclination angle which differs from that of the other group. Hereafter, operation of the array antenna apparatus of the embodiment of the invention is explained. A transmitted signal is supplied to the array antenna chosen by the switch circuit 110 according to the switch change signal, and is emitted into space. Thereby, a beam is formed with an inclination angle set up beforehand for the selected array antenna. For example, if the array antenna 281 and the array antenna 283 are switched alternatively, a beam can be alternatively formed in two directions. Moreover, if the array antenna 282 and the array antenna 284 are also switched alternatively, the array antenna 281 and the array antenna 283 can form alternatively a beam having a polarization which intersects perpendicularly, to the different two directions. Therefore, while a beam can be alternatively formed in two different directions according to the array antenna apparatus of the embodiment of the invention, without using phase shifters, it can also switch to a polarization which intersects perpendicularly with each beam. In addition, in the operation of this embodiment, if it is modified to output a transmitted signal to the switch circuit 110 through the frequency variable apparatus 120 of the second apparatus, a beam scan can also be carried out with a beam which a selected array antenna forms by frequency control. Moreover, a beam scan of large area can also be carried out, by switching alternatively the range in which a beam scan of each array antenna with possible polarization which intersects perpendicularly, if it is made to continue. Moreover, although the above case of operation explained the array antenna which used the discrete, patch antenna elements, it can be similarly carried out with an antenna using other antenna elements (for example, slot antenna elements) which can control a beam inclination angle.

Claims: Array antenna apparatus, comprising a first and second array antenna (281, 282) each having a beam inclination angle characteristic and each including a plurality of antenna elements connected to conduct electrical power applied thereto, and a switch circuit (110) for selectively directing transmission signals to the two array antennas (281, 282) and received signals from the two array antennas (281, 282), characterized by said first array antenna (281) including a first plurality of antenna elements having a horizontal polarization, connected in series to conduct electrical power applied thereto, and said second array antenna (282) including a second plurality of antenna elements having a vertical polarization, connected in parallel to conduct electrical power applied thereto from a direction which is perpendicular to the direction of the series connected electrical power application. The array antenna apparatus according to claim 1, characterized by adjusting the beam inclination angle with a variable frequency unit (120) for selectively varying a frequency of the transmission signals applied to the switch circuit (110). The array antenna apparatus according to claim 1 or 2, characterized by two array antennas which synthesize the main-beam at the same angle and nulls at a different angle. Array antenna apparatus according to any one of claims 1 to 3, characterized in that the first and second array antennas (281, 282) have a first beam inclination angle, and said array antenna apparatus furthermore includes: a third array antenna (283) including a third plurality of antenna elements connected in series to conduct electrical power applied thereto; a fourth array antenna (284) including a fourth plurality of antenna elements connected in parallel to conduct electrical power applied thereto, said third and fourth array antennas (283, 284) having a second beam inclination angle; and said switch circuit (110) being coupled to also selectively direct transmission signals to said third and fourth array antennas and received signals from said third and fourth antennas.

Inventors: MIKAMI AKIO, SAITO KENJIRO, MIKAMI, AKIO, SAITO, KENJIRO, Mikami, Akio, c/o Toshiba Corp., Saito, Kenjiro, c/o Toshiba Corp.
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1996
Main classification: H01Q3
IPC codes: H01Q21, H01Q3, H01Q13