Directional coupler, antenna device, and transmitting-receiving device

[0002] 1. Field of the Invention

[0003] The present invention relates to a directional coupler, an antenna device, and a transmitting-receiving device which are useful for a radar or the like with which the distance to a detection object or a relative velocity of the object is measured by transmission-reception of an electromagnetic wave in the millimetric wave band.

[0004] 2. Description of the Related Art

[0005] In recent years, a so called “millimetric wave radar for car-mounting” has been developed, of which the purpose lies in that for example, the distance to a vehicle running ahead or after, and the relative velocity are measured from a running vehicle. In general, the transmitting-receiving device of the millimetric wave radar of the above type includes a module which comprises a millimetric wave oscillator, a circulator, a directional coupler, a mixer, an antenna, and so forth which are integrated together, and is attached to the front or rear of the vehicle.

[0006] For example, as shown in FIG. 25, at the vehicle on the right side in FIG. 25, the relative distance and relative velocity for the vehicle running ahead (shown on the left side in FIG. 25) are measured for example by transmission-reception of a millimetric wave according to the FM-CW system. FIG. 26 is a block diagram showing the overall configuration of the millimetric radar. In the case shown in FIG. 25, the transmitting-receiving device and the antenna shown in FIG. 26 are attached to the front of the vehicle, and ordinarily, the signal processing device is provided in an optional location. In the signal processing section of the signal processing device, the distance to and the relative velocity of the vehicle running ahead are extracted as numerical information by means of the transmitting-receiving device. In the control-alarm section, based on the velocity of the vehicle running after and the distance between both the vehicles, an alarm is provided when predetermined conditions are satisfied, or when the relative velocity of the vehicle running ahead exceeds a predetermined threshold.

[0007] In the conventional millimetric radar, the directivity of the antenna is fixed. Therefore, there occurs the case that the desired detection or measurement is not performed depending on conditions. More particularly, for example, if vehicles run in plural traffic lanes as shown in FIG. 27, it can not immediately be determined whether a vehicle running ahead is present in the lane where the vehicle is running after, based on only the received electromagnetic wave reflected from the vehicle running ahead. More particularly, as shown in FIG. 27, when an electromagnetic wave is sent from a vehicle Cm by use of a radiation beam designated by the reference character B2, a reflected wave from the vehicle Ca running ahead, together with a reflected wave from a vehicle Cb running in the opposite lane, is received. Accordingly, the determined relative velocity is unduly high, due to the reflected wave from the vehicle running in the opposite lane. As a result, inconveniently, an error alarm is given. Further, in an example shown in FIG. 28, even if an electromagnetic wave is sent forward from the vehicle Cm by use of the radiation beam designated by the reference character B1, the vehicle Ca running ahead in the lane where the vehicle is running after can not be detected. Further, as shown in FIG. 29, even if an electromagnetic wave is sent forward from the vehicle Cm by use of the radiation beam designated by B1, the vehicle Ca running ahead can not be detected.

[0008] Accordingly, it is proposed that the above-described problems can be solved by varying the direction of the radiation beam. For example, in the example of FIG. 27, by varying the radiation beam in the range of B1 to B3, operational processing, and comparing the measurement results obtained in the respective beam directions, the two detection objects running ahead and adjacent in the angular directions can be separately detected. Further, in the example shown in FIG. 28, by analyzing image information obtained by steering operation (steering by a steering wheel) or by means of a camera photographing the forward view with respect to the vehicle, the curve of the lane is judged, and the radiation beam is directed in the direction in dependence on the judgment, for example, the radiation beam is directed to the direction indicated by the reference character B2, and thereby, the vehicle Ca running ahead can be detected. Further, in an example shown by FIG. 29, by analyzing image information from a camera photographing the forward view, the hilly situation of the road is judged, and for example, the radiation beam is directed upwardly, namely, to the direction designated by the reference numeral B2, and thereby, the vehicle Ca running ahead can be detected.

[0009] However, referring to the method of changing the directivity of an electromagnetic wave in the conventional transmitting-receiving device operative in the microwave band or millimetric wave band, the whole of a casing containing the transmitting-receiving device including the antenna is rotated only with a motor or the like to change (tilt) the direction of the radiation beam. Accordingly, the whole of the device is large in size, and it is difficult to scan with the radiation beam while the direction of the radiation is changed at a high speed.

[0010] Accordingly, it is an object of the present invention to solve the above-described problems and to provide a directional coupler in which the relative positions of two transmission lines can be changed while the coupling of the two transmission lines is maintained, an antenna device, and a transmitting-receiving device which can be easily miniaturized due to the directional coupler and of which the directivity can be switched at a high speed.

[0011] In order to achieve the above object, according to a first aspect of the present invention, there is provided a directional coupler comprising a first microstrip line and a second microstrip line adjacent to the first microstrip line, the relative positions of the first microstrip line and the second microstrip line being changeable.

[0012] According to a second aspect of the present invention, there is provided a directional coupler comprising a first strip line, a second strip line adjacent to the first strip line, the relative positions of the first strip line and the second strip line being changeable.

[0013] According to a third aspect of the present invention, there is provided a directional coupler comprising a first slot line and a second slot line adjacent to the first slot line, the relative positions of the first slot line and the second slot line being changeable.

[0014] According to a fourth aspect of the present invention, there is provided a directional coupler comprising a first coplanar line and a second coplanar line adjacent to the first coplanar line, the relative positions of the first coplanar line and the second coplanar line being changeable.

[0015] According to a fifth aspect of the present invention, there is provided a directional coupler comprising a first wave guide and a second wave guide adjacent to the first wave guide, the relative positions of the first coplanar line and the second coplanar line being changeable.

[0016] According to a sixth aspect of the present invention, there is provided a directional coupler comprising a first suspended line and a second suspended line adjacent to the first suspended line, the relative positions of the first suspended line and the second suspended line being changeable.

[0017] Thus, in a variety of applications, available is the directional coupler of which the relative positions of the two transmission lines can be changed while the coupling of the two transmission lines is maintained.

[0018] According to the present invention. preferably, there is provided an antenna device including the directional coupler according to any one of the first through sixth aspects of the present invention, a primary radiator coupled or connected to a part of the directional coupler, and a driving mechanism for driving the directional coupler and the primary radiator.

[0019] Further, according to the present invention, there is provided a transmitting-receiving device including the antenna device according to the seventh aspect of the present invention, and a transmitting-receiving circuit connected to the antenna device.

[0020] Thus, an antenna device and an transmitting-receiving device of which the sizes are relatively small, and with which scanning with a radiation beam can be performed while the radiation beam direction can be changed at a high speed, are provided.

[0021] FIG. 1 is a perspective view of an antenna device according to a first embodiment of the present invention;

[0022] FIG. 2, comprising FIGS. 2A, 2B and 2C, is a schematic side view of a primary radiator and a dielectric lens antenna showing the relationship of the relation in position between them to the directivity of a radiation beam;

[0023] FIG. 3 is a cross sectional view taken along the line X—X of FIG. 1;

[0024] FIG. 4 is a cross sectional view of another form of the first embodiment;

[0025] FIG. 5 is a perspective view of an antenna device according to a second embodiment of the present invention;

[0026] FIG. 6 is a cross sectional view taken along the line Y—Y of FIG. 5;

[0027] FIG. 7 is a cross sectional view of a further form of the second embodiment;

[0028] FIG. 8 is a cross sectional view of a still further form of the second embodiment;

[0029] FIG. 9 is a cross sectional view of another form of the second embodiment;

[0030] FIG. 10 is a cross sectional view of a further form of the second embodiment;

[0031] FIG. 11 is a cross sectional view of a still further form of the second embodiment;

[0032] FIG. 12 is a perspective view of an antenna device according to a third embodiment of the present invention;

[0033] FIG. 13 is a perspective view of an antenna device according to a fourth embodiment of the present invention;

[0034] FIG. 14 is a perspective view of an antenna device according to a fifth embodiment of the present invention;

[0035] FIG. 15 is a perspective view of an antenna device according to a sixth embodiment of the present invention;

[0036] FIG. 16 is a block diagram showing the configuration of a transmitting-receiving device according to the present invention;

[0037] FIG. 17 is a plan view of an antenna device as an exemplified application of a directional coupler of the present invention;

[0038] FIG. 18 is a plan view of an antenna device as an exemplified application of a directional coupler of the present invention;

[0039] FIG. 19 is a plan view of an antenna device as an exemplified application of a directional coupler of the present invention;

[0040] FIG. 20 is a plan view of an antenna device as an exemplified application of a directional coupler of the present invention;

[0041] FIG. 21 is a plan view of an antenna device as a further exemplified application of a directional coupler of the present invention;

[0042] FIG. 22 is a side view of a primary radiator and a dielectric lens antenna showing the concept of a method of beam scanning;

[0043] FIG. 23 is a side view of a primary radiator and a dielectric lens antenna showing the concept of a method of beam scanning;

[0044] FIG. 24 is a side view of a primary radiator and a dielectric lens antenna showing the concept of a method of beam scanning;

[0045] FIG. 25 is a block diagram showing the use situation of a radar for car-mounting;

[0046] FIG. 26 is a block diagram showing the configuration of the radar for car-mounting;

[0047] FIG. 27 is an illustration of the situation that in the radar for car-mounting, the radiation beam is tilted in the horizontal direction;

[0048] FIG. 28 is an illustration of the situation that the radiation beam in the radar for car-mounting is tilted in the horizontal direction; and

[0049] FIG. 29 is an illustration of the situation that the radiation beam in the radar for car-mounting is tilted in the vertical direction.

[0050] Hereinafter, an antenna device according to an embodiment of the present invention will be described with reference to FIGS. 1 through 15.

[0051] First, an antenna device according to a first embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a perspective view of the antenna device of the first embodiment.

[0052] As shown in FIG. 1, an antenna device 10aof the instant embodiment comprises a directional coupler and a primary radiator. The directional coupler comprises a first transmission line 20awhich comprises a microstrip line in which a line conductor 12 is formed on one of the main-faces of a dielectric substrate 11, and a ground conductor 13 (not shown in FIG. 1) is formed on the back side of the main-faces, and a second transmission line 30awhich consists of a microstrip line formed in a similar manner. The primary radiator consists of a patch antenna 14aconnected to the second transmission line 30a. The first transmission line 20aand the second transmission line 30acontain their portions which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other, and function as the directional coupler. More particularly, by designing properly, a half of a signal input through a port 2 can be output through a port 4, and the remaining half of the signal can be output through a port 1.

[0053] In the instant embodiment, the first transmission line 20ais fixed, while a driving mechanism 21 employing a voice coil motor, a pulse motor, or the like, is attached to the second transmission line 30a, and thereby, the second transmission line 30acan be shifted in the direction parallel to the line passing through a port 3 and the port 4 in FIG. 1. That is, the second transmission line 30acan be shifted while the linearly adjacent portions of the first transmission line 20aand the second transmission line 30aare maintained. Accordingly, while an electromagnetic wave is being radiated from the primary radiator connected to the second transmission line 30a, the position of the primary radiator can be changed. For example, as shown in the schematic side views of FIGS. 2A through 2C, if a dielectric lens 16 is arranged in the direction along which the electromagnetic wave of the primary radiator 15 is radiated, the directivity of the radiation beam can be changed as shown in FIGS. 2A through 2C by varying the position of the primary radiator 15 in the focal plane of the dielectric lens 16. That is, when the primary radiator 15 is disposed on the central axis of the dielectric lens 16, the electromagnetic wave is radiated in the central-axial direction. When the primary radiator 15 is arranged in departure from the central axis, the electromagnetic wave is radiated in a direction opposite to the departure.

[0054] As seen in the above-description, according to the present invention, the radiated bean can be caused to scan only by shifting the second transmission line 30awhich is relatively light in weight. Further, since the microstrip lines are used as the first transmission line 20aand the second transmission line 30a, as in the instant embodiment, the antenna device can be connected to MMIC or the like, not using a line converter and so forth. This enhances the applicability of the antenna device. In the antenna device 10aof the instant embodiment, as shown in FIG. 3 which is a cross-sectional view of the antenna device 10ataken along the line X—X in FIG. 1, the first transmission line 20aand the second transmission line 30aare formed separately as an example. However, for example, as shown in the cross-sectional view of FIG. 4, the second transmission line 30a1 may be arranged in a concave portion provided for the first transmission line 20a1.

[0055] Hereinafter, an antenna device including the directional coupler according to a second embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 is a perspective view of the antenna device of the instant embodiment. The basic function of the antenna device is the same as that of the first embodiment, and the detailed description of the antenna device of the instant embodiment will be omitted.

[0056] As seen in FIG. 5, the antenna device 10bof the instant embodiment comprises a directional coupler and a primary radiator. The directional coupler comprises a first transmission line 20bin which the ground conductor 13 is formed on one of the main-faces of the dielectric substrate 11, and the line conductor 12 is formed inside the dielectric substrate 11. The second transmission line 30bis formed in a similar manner. The primary radiator comprises a slot antenna 14bformed in the second transmission line 30b. The first transmission line 20band the second transmission line 30bare so arranged as to be opposite to each other in the vertical direction, so that the first transmission line 20band the second transmission line 30bfunction as a strip line. The first transmission line 20band the second transmission line 30bcontain the portions thereof which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other, and function as the directional coupler. The first transmission line 20bis fixed, while a driving mechanism (not shown in FIG. 5) employing a voice coil motor, a pulse motor, or the like is attached to the second transmission line 30b, and thereby, the second transmission line 30bcan be shifted in the direction parallel to the line passing through the port 3 and the port 4 in FIG. 5.

[0057] In the antenna device 10bof the instant embodiment, as shown in FIG. 6 which is a cross sectional view of the antenna device taken along the line Y—Y in FIG. 5, the first transmission line 20band the second transmission line 30bare so arranged as to be opposite to each other in the vertical direction as an example. However, as shown in the cross-sectional view of FIG. 7, the first transmission line 20b1 in which the ground conductor 13 is formed on the opposite sides of the dielectric substrate 11, and the line conductor 12 is formed inside the dielectric substrate, and the second transmission line 30b1 formed in a similar manner may be arranged side by side. Further, as shown in the cross-sectional view of FIG. 8, the first transmission line 20b2 in which the line conductor 12 is formed on one of the main-faces of the dielectric substrate 11, and the ground conductor 13 is formed on the other main-face, and the second transmission line 30b2 formed in a similar manner may be so arranged as to be opposite to each other in the vertical direction. Further, available are transmission lines 20b3 and 30b3 having the line conductors 12 of which the positions depart from each other as shown in the cross sectional view of FIG. 9. Moreover, as shown in the cross sectional view of FIG. 10, available are a first transmission line 20b4 having the ground conductor 13 formed on one of the main faces of the dielectric substrate 11 and the line conductor 12 formed inside the dielectric substrate 13, and a second transmission line 30b4 formed in a similar manner which are so arranged to be opposite to each other in the vertical direction, the position of the line conductors 12 departing from each other. Further, as shown in the cross sectional view of FIG. 10, available are a first transmission line 20b5 having the ground conductor 13 formed on one of the main faces and the line conductor 12 formed inside the dielectric substrate 11, and the second transmission line 30b5 having the line conductor 12 formed on one of the main faces of the dielectric substrate 11 and the ground conductor 13 formed on the other main-face, the second transmission line 30b5 being arranged in the concave portion of the first transmission line 20b5.

[0058] An antenna device including the directional coupler according to a third embodiment of the present invention will be now described with reference to FIG. 12. FIG. 12 is a perspective view of the antenna device of the instant embodiment. The basic function of the antenna device of the instant embodiment is the same as that of the antenna device of the first embodiment, and its detailed description will be omitted.

[0059] As shown in FIG. 12, the antenna device 10cof the instant embodiment comprises a directional coupler and a primary radiator. The directional coupler comprises a first transmission line 20cwhich comprises a slot line formed by two conductors 17 arranged on one of the main faces of the dielectric substrate 11 through a gap between them, and a second transmission line 30cwhich comprises a slot line formed in a similar manner. The primary radiator comprises a slot antenna 14bconnected to the second transmission line 30c. The first transmission line 20cand the second transmission line 30chave their transmission line portions which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other and function as a directional coupler. The first transmission line 20cis fixed, and a driving mechanism (not shown in FIG. 12) using a voice coil motor, a pulse motor, or the like is attached to the second transmission line 30c, and thereby, the second transmission line 30ccan be shifted in the direction parallel to the line passing through the port 3 and the port 4 in FIG. 12.

[0060] Further, an antenna device including the directional coupler according to a fourth embodiment of the present invention will be now described with reference to FIG. 13. FIG. 13 is a perspective view of the antenna device of the instant embodiment. The basic function of the antenna device of the instant embodiment is the same as that of the antenna device of the first embodiment, and its detailed description will be omitted.

[0061] As shown in FIG. 13, the antenna device 10dof the instant embodiment comprises a directional coupler and a primary radiator. The directional coupler comprises a first transmission line 20dwhich comprises a coplanar line comprises the line conductor 12 formed on one of the main-faces of the dielectric substrate 11 and the ground conductor 13 arranged through a space to the line conductor 12, and a second transmission line 30dwhich comprises a coplanar line formed in a similar manner. The primary radiator comprises a patch antenna 14aconnected to the second transmission line 30d. The first transmission line 20dand the second transmission line 30dhave their transmission line portions which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other and function as the directional coupler. The first transmission line 20dis fixed, and a driving mechanism (not shown in FIG. 13) using a voice coil motor, a pulse motor, or the like is attached to the second transmission line 30d, and thereby, the second transmission line 30dcan be shifted in the direction parallel to the line passing through the port 3 and the port 4 in FIG. 13.

[0062] Further, an antenna device including the directional coupler according to a fifth embodiment of the present invention will be now described with reference to FIG. 14. FIG. 14 is a perspective view of the antenna device of the instant embodiment. The basic function of the antenna device of the instant embodiment is the same as that of the antenna device of the first embodiment, and its detailed description will be omitted.

[0063] As shown in FIG. 14, an antenna device 10eof the instant embodiment comprises a directional coupler and a primary radiator. The directional coupler comprises a first transmission line 20ewhich comprises a guide wave, and a second transmission line 30ewhich comprises a guide wave as well. The primary radiator comprises a horn antenna 14cconnected to the second transmission line 30e. The first transmission line 20eis fixed, and a driving mechanism (not shown in FIG. 14) using a voice coil motor, a pulse motor, or the like is attached to the second transmission line 30e, and thereby, the second transmission line 30ecan be shifted in the direction parallel to the line passing through the port 3 and the port 4 in FIG. 14. The first transmission line 20eand the second transmission line 30ehave their transmission line portions which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other and function as a directional coupler. More particularly, at the surfaces of the first transmission line 20eand the second transmission line 30ewhich are adjacent to each other, holes 18aand 18bfor coupling are formed, respectively. The hole 18aof the first transmission line 20ehas a larger size in the shifting direction than each of the holes 18bof the second transmission line 30e. Accordingly, the first transmission line 20eand the second transmission line 30ekeep with each other when the second transmission line 30eis shifted, due to the holes 18aand 18bfor coupling, and the horn antenna 14ccan be shifted. In the instant embodiment, the antenna device 10ehaving three holes 18bfor coupling which are separated at a distance of λg/4 from each other is used. However, at least four holes for coupling may be formed.

[0064] Further, an antenna device including the directional coupler according to a sixth embodiment of the present invention will be now described with reference to FIG. 15. FIG. 15 is a perspective view of the antenna device of the instant embodiment. The basic function of the antenna device of the instant embodiment is the same as that of the antenna device of the first embodiment, and its detailed description will be omitted.

[0065] As shown in FIG. 15, an antenna device 10fof the instant embodiment comprises coupler and a primary radiator. The directional coupler comprises a first transmission line 20fwhich comprises a suspended line comprises a cylindrical ground conductor 13, the dielectric substrate 11 disposed in the center of the ground conductor 13, and the line conductor 12 formed on the dielectric substrate 11, and a second transmission line 30fwhich comprises a suspended line formed in a similar manner. The primary radiator comprises a slot antenna 14bconnected to the second transmission line 30f. The first transmission line 20fis fixed, and a driving mechanism (not shown in FIG. 15) using a voice coil motor, a pulse motor, or the like is attached to the second transmission line 30f, and thereby, the second transmission line 30fcan be shifted in the direction parallel to the line passing through the port 3 and the port 4 in FIG. 15. The first transmission line 20fand the second transmission line 30fhave their transmission line portions which are linearly adjacent to each other. Through the portions, the two transmission lines are coupled to each other and function as a directional coupler. More particularly, at the surfaces of the first transmission line 20fand the second transmission line 30fwhich are adjacent to each other, holes 18aand 18bfor coupling are provided, respectively. The hole 18aof the first transmission line 20fhas a larger size in the shifting direction than the hole 18bof the second transmission line 30f. Accordingly, the first transmission line 20fand the second transmission line 30fmaintain coupling with each other when the second transmission line 30fis shifted, due to the holes 18aand 18bfor coupling, and the slot antenna 14bcan be shifted.

[0066] In the above-described embodiments, as the first transmission line and the second transmission line, lines of the sane type, for example, the microstrip line and the microstrip line, are employed. However, the directional coupler may be formed of a combination of transmission lines of different types, for example, a microstrip line and a coplanar line or the like may be employed.

[0067] Hereinafter, a transmitting-receiving device in accordance with the present invention will be described with reference to FIG. 16. FIG. 16 is a block diagram showing the configuration of the transmitting-receiving device of the present invention.

[0068] As shown in FIG. 16, a transmitting-receiving device 40 of the present invention comprises an antenna 10, a circulator 41 connected to the antenna 10, an oscillator 42 connected to one of the ports of the circulator 41, a mixer 43 connected to the other port of the circulator 41, a second circulator 44 connected between the circulator 41 and the oscillator 42, and couplers 45 and 46. In this case, the oscillator 42 is a voltage-controlled oscillator. The oscillation frequency is changed by applying a voltage to its bias terminal. The antenna device 10 in FIG. 16 is the same as that shown in each of the first through sixth embodiments. A dielectric lens (not shown in FIG. 16) is arranged in the radiation direction of an electromagnetic wave from the primary antenna device. In the transmitting-receiving device 40 having the above-described configuration, a signal from the oscillator 42 is propagated through the circulator 44, the coupler 45, and the circulator 41 to the primary radiator of the antenna device 10, and radiated through the dielectric lens. A part of the signal from the oscillator 42 as a local signal is supplied through the couplers 45 and 46 to the mixer 43. The reflected wave from an object is supplied through the antenna device 10, the circulator 41, and the coupler 46 to the mixer 43 as an RF signal. The mixer 43 as a balanced mixer outputs as an IF signal a differential component between the RF signal and the local signal.

[0069] Hereinafter, exemplified applications of the directional coupler in accordance with the present invention will be described with reference to FIGS. 17 through 24. The embodiment described below can be applied to all the above described transmission lines. However, the description will be carried out in reference to the microstrip lines. Like parts of the first embodiment and the instant embodiment are designated by like reference numerals and signs, and their detailed description will be omitted.

[0070] An example of the antenna device with which the scanning with radiation beams can be performed in three sections, namely, in upper, middle, and lower sections will be now described with reference to FIGS. 17 through 20. FIGS. 17 through 20 are plan views of the antenna device of the instant embodiment, respectively.

[0071] As shown in FIG. 17, an antenna device 10a1 of the instant embodiment comprises a fixed first transmission line 20a, a shifting section A including three second transmission lines 30ax, 30ay, and 30azand three patch antennas 14ax, 14ay, and 14azconnected to the second transmission lines 30ax, 30ay, and 30az, respectively, and a dielectric lens 16 fixed to the upper side of them. Further, a terminal resistive film 19 is formed on one end of the first transmission line 20a.

[0072] In the antenna device 10a1 having the above-described configuration, for example, as shown in FIG. 17, when the first transmission line 20aand the second transmission line 30axhave their portions linearly adjacent to each other, both are coupled to each other, and an electromagnetic wave is radiated through the patch antenna 14ax. The shifting section A is shifted while the first transmission line 20aand the second transmission line 30axare kept in the coupled state, and thereby, the position of the patch antenna 14axis changed, so that the scanning of the radiation beam can be performed in the lower section.

[0073] The shifting section A is further shifted, so that the first transmission line 20aand the second transmission line 30aymove so as to have their portions linearly adjacent to each other, as shown in FIG. 18, when both are coupled to each other, and an electromagnetic wave is radiated through the patch antenna 14ay. That is, the shifting section A is shifted while the coupling state is maintained, and thereby, the position of the patch antenna 14ayis shifted, so that the scanning with the radiation beam can be carried out in the middle section.

[0074] Similarly, as shown in FIG. 19, when the first transmission line 20aand the second transmission line 30azmove so as to have the linearly-adjacent portions, both are coupled to each other, and an electromagnetic wave is radiated through the patch antenna 14az. Thus, while the coupling state is maintained, the shifting section A is shifted, and thereby, the position of the patch antenna 14azis shifted so that the scanning with the radiation beam in the upper section can be performed.

[0075] Further, when the shifting section A is shifted to the position shown in FIG. 20, the first transmission line 20ais not coupled to any of the second transmission lines, and no beam is radiated through the antenna device 10a1.

[0076] In the above example, a method for switching the three primary radiators is described. In addition to the method, other functions can be rendered by the directional coupler. More particularly, for example, in the directional coupler having one first transmission line and one second transmission line, the second transmission line is shifted, and thereby, the coupling state in which the first and second transmission lines have the linearly-adjacent portions is changed to the non-coupling state where the linearly-adjacent portions are absent. Thus, a signal sent from the first transmission line can be switched to “be transmitted” or “not to be transmitted” to the second transmission line. Accordingly, the directional coupler can be used as a switch.

[0077] Hereinafter, an example of the antenna device with which the scanning can be performed with plural radiation beams at the same time will be described with reference to FIGS. 21 through 24. FIG. 21 is a plan view of the antenna device of the instant embodiment. FIGS. 22 through 24 are side views showing the concept of the beam scanning, respectively.

[0078] As shown in FIG. 21, an antenna device 10a2 of the instant embodiment comprises a fixed section B having three first transmission lines 20ax, 20ay, and 20az, a shifting section A having the three second transmission lines 30ax, 30ay, and 30azto be coupled to the first transmission lines 20ax, 20ay, and 20az, the three patch antennas 14ax, 14ay, and 14azconnected to the second transmission lines 30ax, 30ay, and 30az, respectively, and three dielectric lenses 16a,16b,and 16cfixed to the upper side of them. An electromagnetic wave is sent through the patch antenna 14ax, which is one of the three patch antennas 14ax, 14ay, and 14az, and an electromagnetic wave is received through the other two patch antennas 14axand 14ay. To the three first transmission lines 20ax, 20ay, and 20az, an appropriate transmitting or receiving circuit, not shown in FIG. 21, is connected, and thereby, a transmitting-receiving device is formed. Terminal resistive films 19 are formed on one ends of the first transmission lines 20ax, 20ay, and 20az, respectively.

[0079] In the antenna device 10a2 having the above structure, the shifting section A is shifted by use of a driving means not shown in FIG. 21, and thereby, the three patch antennas 14ax, 14ay, and 14azare simultaneously shifted. By use of the antenna device 10a2 having the above function, an angle can be measured in a wide range at a desired detection distance with an appropriate measuring-angle resolution power.

[0080] More particularly, as shown in FIG. 22, at a point in time, the positions of the patch antennas 14ax, 14ay, and 14az, and the dielectric lenses 16a, 16b, and 16care so defined that a wave-sending beam is directed at 0° to the forward direction, one of the receiving beams to the right by 15° to the forward direction, and the other receiving beam to the left by 15° to the forward direction. In this case, the angle measurement can be carried out in the range between the two receiving beams. If the angle-measuring range is desired to be widened, provided that the defined positions of the patch antennas are fixed, a method for widening the ranges of the respective beams themselves and a method for widening the distance between the two beams may be provided. However, there is the problem that by the former method, the detection distance becomes short, while by the later method, the angle-measurement resolution power is reduced.

[0081] As seen in the instant embodiment, the shifting section A in which the three patch antennas 14ax, 14ay, and 14azare formed is shifted, so that for example, as shown in FIG. 23, the wave-sending beam is directed to the left by 15° to the forward direction, one of the receiving beams at 0° to the forward direction, and the other receiving beam to the left by 30° to the forward direction. Further, as shown in FIG. 24, the shifting section A is shifted in the opposite direction, so that the wave-sending beam is directed to the right by 15° to the forward direction, one of the receiving beam to the right by 30° to the forward direction, and the other receiving beam at 0° to the forward direction. In the above manner, the shifting section A is so shifted that the beam scans, and thereby, the angle-measurement can be performed in a wide range without the detection distance shortened or the angle-measurement resolution power reduced.

[0082] As described above, in the directional coupler including the two transmission lines, the relative position of the two transmission lines is changed while the coupling is maintained. Accordingly, when the primary radiator is connected to one of the transmission lines, the position of the primary radiator can be shifted while the electromagnetic wave is being radiated. That is, by shifting the transmission line which is relatively light in weight, the radiation beam from the antenna can be caused to scan. Thus, it is unnecessary to provide a large-sized driving means for moving the whole of the casing containing the transmitting-receiving device, and the antenna device can be miniaturized.

[0083] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.