Antenna-shared distributor and transmission and receiving apparatus using same

Abstract: An antenna-shared distributor (2) is provided such that a non- conductor section is provided in a part of two conductor planes (14, 15), a dielectric resonator (11) which resonates in the HE111 mode is disposed in that part, and first and second dielectric strips whose respective end portions face the dielectric resonator (11) are disposed, forming first and second dielectric lines (12, 13) and further, a voltage-control oscillator (1) and a mixer (3) are connected to the first and second dielectric lines (12, 13), respectively.

Description: The present invention relates to an antenna-shared distributor and, more particularly, to an antenna-shared distributor for a dielectric line for use in a millimetric-wave radar or the like to be mounted in a vehicle and a transmission and receiving apparatus using such distributor. Millimetric-wave radars to be mounted in a vehicle are used to measure a relative velocity between a subject vehicle and another vehicle and the distance between the subject vehicle and the other vehicle. Transmission and receiving apparatuses of such millimetric-wave radars are generally modules including a millimetric-wave voltage control oscillator, a circulator, a coupler, a mixer, an antenna and the like, and this module is mounted in the front or the back of a vehicle and used. In Fig. 11, the relative distance and the relative velocity between a truck 500 and an automobile 600 driving in front is measured by transmitting and receiving a millimetric wave from the truck 500 by an FM-CW method. Fig. 12 is a block diagram of a millimetric-wave radar used herein. The transmission and receiving apparatus and the antenna are mounted to the front of the vehicle. A signal processing section limits a transmission and receiving apparatus in order to cause it to transmit a millimetric wave by a predetermined method, and analyzes radio waves received by the antenna in order to compute, for example, the distance between two vehicles. When the distance between the two vehicles reaches below a predetermined distance, the signal processing section controls a warning section in order to call a driver to attention. Fig. 13 shows the construction of a transmission and receiving apparatus of the prior art, and is a schematic plan view illustrating a state in which a conductor plate which covers the top portion of a dielectric strip which will be described later is removed. In Fig. 13, reference numeral 72 denotes a circulator, with a voltage control oscillator 71 and a terminater 73 being disposed on two sides of the circulator 72. Reference numeral 81 denotes a dielectric resonator for transmission of a primary radiator, with a dielectric strip 74 being disposed between the circulator 72 and the dielectric resonator 81. Reference numeral 82 denotes a dielectric resonator for reception of a primary radiator, and reference numeral 85 denotes a mixer, with a dielectric strip 84 being disposed between the dielectric resonator 82 and the mixer 85. Further, a linear-shaped dielectric strip 76, dielectric strips 75 and 77 which each constitute a bent portion, and terminaters 78 and 79 are disposed. A portion proximate to the dielectric strips 74 and 75 is structured as a coupler 80, and a portion proximate to the dielectric strips 84 and 77 is structured as a coupler 83. Further, dielectric lenses 86 and 87 are mounted in the upper portion of the dielectric resonators 81 and 82, respectively. Fig. 14 is an equivalent circuit diagram of the transmission and receiving apparatus shown in Fig. 13. The voltage-control oscillator 71 includes a varactor diode and a Gunn diode. An oscillation signal therefrom is propagated to the dielectric resonator 81 through the circulator 72 and radiated to the outside through a window formed in the conductor plate in the upper portion of the dielectric resonator 81 and the dielectric lens 86. The circulator 72 and the terminater 73 constitute an isolator. An RF signal received via the dielectric lens 87 and the dielectric resonator 82 is propagated through the dielectric strip 84. At this time, a Lo signal (local signal) is introduced to the dielectric strip 84 by the couplers 80 and 83 and input to the mixer 85. The mixer 85 is formed of a Schottky barrier diode and generates an IF signal (intermediate frequency signal). However, in a transmission and receiving apparatus for a millimetric-wave radar, a curved line (bent portion) must be provided in a dielectric strip, and couplers comprising two dielectric strips which are brought close to each other must be provided at at least two places within the apparatus in order to supply a part of a transmission signal as a Lo signal (local signal) to the mixer. A large area is required to construct such a coupler. In particular, when a dielectric line is formed using a nonradiative dielectric line (NRD guide), the orthogonality between the LSM01 mode and the LSE01 mode is distorted in the curved portion, and coupling occurs between the modes. Therefore, a low-loss characteristic of the line is realized only at the radius of curvature and the curved corner in a narrow range of the line. Thus, the shape of the coupler is limited, and formation of the apparatus into a small size is difficult. Meanwhile, the aperture diameter of the antenna depends on the specifications of the transmission and receiving apparatus. When, for example, a transmission wave is within a spread of 3.5 m after 100 m in the forward direction, the beam angle is 2°, and the antenna aperture diameter must be approximately 170 mm in the 60 GHz band. Further, when a transmission wave is within a spread of 3.5 m after 50 m in the forward direction, the beam width angle is 4°. For this reason, the antenna aperture diameter must be approximately 90 mm. In the transmission and receiving apparatus of Fig. 13, since the area where the coupler is formed together with the voltage-control oscillator and the mixer becomes larger than the antenna size, the transmission and receiving apparatus is forced to be enlarged as a whole. Further, for the purpose of achieving a small size of the apparatus, shared use of a single antenna in transmission and reception is possible. However, in this case, a circulator for distributing a transmission signal and a receiving signal becomes necessary, and therefore a large reduction in size cannot be realized. EP 0 709 912 A1 describes, in its introductory portion, a radar module as one application of a non-radiative dielectric wave guide circuit. The radar module comprises a FM signal generator, a non-radiative dielectric wave guide isolator, a mixer circuit and an antenna block. The isolator comprises dielectric blocks constituting a mode suppressor and a dielectric ring constituting a central member of the isolator. Further, a dielectric strip is provided which constitutes an output line and a further dielectric strip is provided which constitutes a lineal line of a non-reflective terminal circuit. It is the object of the present invention to provide a compact antenna-shared distributor and a transmission and receiving apparatus using such a distributor. This object is achieved by an antenna-shared distributor according to claim 1 and by a transmission and receiving apparatus according to claim 8. To this end, according to one aspect of the present invention, an antenna-shared distributor is provided comprising: two facing conductor sections and a dielectric resonator disposed between the conductor sections. A non-conductor section is provided in at least one of the conductor sections and at a position facing the dielectric resonator. Further, a first dielectric line and a second first dielectric line are disposed close to the dielectric resonator. Since this antenna-shared distributor is formed of only a resonator and at least two dielectric lines facing with each other with the resonator interposed in between, the antenna-shared distributor has a simple construction. According to another aspect of the present invention, there is provided a transmission and receiving apparatus comprising an oscillator coupled to one of the dielectric lines disposed with the antenna-shared distributor interposed therebetween, and a mixer circuit coupled to the other dielectric line. In this transmission and receiving apparatus, since one antenna-shared distributor is only disposed between the oscillation circuit and the mixer circuit, the construction of the transmission and receiving apparatus is simple. The transmission and receiving apparatus may further include an electromagnetic guide in the shape of a horn which is disposed around the non-conductor section. The horn makes it possible to efficiently focus radio waves onto the dielectric resonator. The transmission and receiving apparatus may further include a dielectric lens at a position facing the non-conductor section. The dielectric lens makes it possible to increase the focus of radio waves radiated from the dielectric resonator. The above and further objects, aspects and novel features of the invention will become more apparent from the following detailed description when read in connection with the accompanying drawings Figs. 1A and 1B show the construction of an antenna-shared distributor and a transmission and receiving apparatus using such an antenna-shared distributor according to a first embodiment of the present invention; Figs. 2A, 2B and 2C show the construction of the antenna-shared distributor; Fig. 3 is an equivalent circuit diagram of the transmission and receiving apparatus shown in Figs. 1A and 1B; Figs. 4A and 4B are sectional views illustrating the construction of a dielectric line of each section used in the first embodiment of the present invention; Figs. 5A, 5B and 5C show the construction of a voltage-control oscillator and a mixer; Figs. 6A, 6B and 6C show the construction of an antenna-shared distributor according to a second embodiment of the present invention; Figs. 7A and 7B show the construction of a circuit unit of a transmission and receiving apparatus according to a second embodiment of the present invention; Fig. 8 shows the construction of a circuit unit of a transmission and receiving apparatus according to a third embodiment of the present invention; Figs. 9A, 9B and 9C are sectional views of a transmission and receiving apparatus according to fourth, fifth and sixth embodiments of the present invention; Figs. 10A1, 10A2, 10B1 and 10B2 are sectional views illustrating the construction of another dielectric line used in a transmission and receiving apparatus according to the present invention; Fig. 11 shows the usage of a millimetric-wave radar to be mounted in a vehicle, and the relationship between the beam width of a transmission wave and a detection distance; Fig. 12 is a block diagram illustrating the construction of the millimetric-wave radar to be mounted in a vehicle; Fig. 13 is a schematic plan view illustrating the construction of a transmission and receiving apparatus of the prior art; and Fig. 14 is an equivalent circuit diagram of the transmission and receiving apparatus shown in Fig. 13. The construction of an antenna-shared distributor for a dielectric line and a transmission and receiving apparatus using such an antenna-shared distributor according to a first embodiment of the present invention will be described below with reference to Figs. 1A, 1B to 5. A circuit unit 4 of Figs. 1A and 1B includes a voltage-control oscillator 1, an antenna-shared distributor 2, and a mixer 3. The antenna-shared distributor 2 is disposed in the center of the unit, and the voltage-control oscillator 1 and the mixer 3 are disposed on both sides of the antenna-shared distributor 2. The circuit unit 4, as shown in Fig. 1B, is mounted to the lower portion of a case 5 and is covered with a rear lid 6. Further, a dielectric lens 7 is mounted above the case 5. This dielectric lens 7 is made of a composite material of, for example, a resin and ceramic, with the specific inductive capacity thereof being set at approximately 4.0. Further, a matching layer having a specific inductive capacity of approximately 2.0 for preventing reflection is provided on the top surface and the bottom surface of the dielectric lens 7. A dielectric resonator 11, serving as a primary vertical radiator, is provided at the focus position of the dielectric lens 7 in the center of the antenna-shared distributor 2. Figs. 2A and 2B are a top plan view and a sectional view of the antenna-shared distributor 2, respectively. An opening o is provided in the center of a conductor plate 14. The conductor plate 14 may be such that the surface of a conductor plate is coated with a conductor; in this case, in place of the opening o, a portion having the coating of the conductor removed may be provided. The dielectric resonator 11 which resonates in the HE111 mode is disposed below the opening o in such a manner for the axis of the dielectric resonator 11 to become normal to the main surface of the conductor plates 14 and 15. Further, a first dielectric strip 12 and a second dielectric strip 13 are disposed between the conductor plates 14 and 15 in such a manner for the respective end portions of the dielectric strips 12 and 13 to face the dielectric resonator 11. The electromagnetic wave of the LSM mode in which an electric field having components at right angles to the direction of the length (in the x-axis direction in the figure) of the dielectric strip 12 and parallel (in the y-axis direction in the figure) to the conductor plates 14 and 15 and a magnetic field having components normal to the conductor plates 14 and 15 occur propagates within the dielectric strip 12. Since the dielectric resonator 11 resonates in the HE111 mode having electric-field components in the same direction as that of the electric field of the dielectric strip 12, the first dielectric strip 12 and the dielectric resonator 11 are easily coupled to each other. Then, a linearly polarized electromagnetic wave is radiated in a direction normal (in the z-axis direction in the figure) to the conductor plate 14 via the opening o. Further, the dielectric line 13 formed of a dielectric strip and the dielectric resonator 11 are coupled to each other, and the electromagnetic wave propagates within the dielectric line 13 in the LSM mode, as shown in Fig. 2C. This signal is a Lo signal to be sent to the mixer 3 shown in Fig. 1A. When a signal reflected from a target object enters the dielectric resonator 11, an LSM01-mode signal propagates within the dielectric line 13 as a result of the coupling between the dielectric line 13 and the dielectric resonator 11. This signal is supplied as an RF signal to the mixer 3. The power distribution ratio of the radiation power of the transmission signal to the Lo signal may be set according to the spacing between the dielectric resonator 11 and the dielectric strips 12 and 13. Fig. 3 is an equivalent circuit diagram of the transmission and receiving apparatus shown in Figs. 1A and 1B. The voltage-control oscillator 1 includes a varactor diode and a Gunn diode. An oscillation signal Tx from the voltage-control oscillator 1 is distributed by the antenna-shared distributor 2 and is radiated from an antenna formed of the dielectric resonator and the dielectric lens 7 within the antenna-shared distributor. A part of the oscillation signal Tx is made to be a Lo signal and sent out to the mixer 3. A received signal RX is also distributed by the antenna-shared distributor 2, and one of the signals is supplied as an RF signal to the mixer 3. As a result, the mixer 3 outputs an IF signal. Fig. 4A is a sectional view of a dielectric line within the antenna-shared distributor, in which the dielectric strip 12 is fitted into the grooves formed in the conductor plates 14 and 15. Fig. 4B is a sectional view of a dielectric line within the voltage-control oscillator 1, in which similarly dielectric strips 16a and 16b are fitted into the grooves on the surface of the conductor plates 21 and 22, and a substrate 20 is disposed between the dielectric strips 16a and 16b. The cross section of the dielectric line within the mixer 3 is similar to that shown in Fig. 4B. By determining the spacing between the two conductor plates, the depth of the groove, and the thickness and the specific inductive capacity of the dielectric strip, an NRD guide can be constructed with the dielectric strip portion made as a propagation area and the other area made as a non-propagation area (cut-off area). Figs. 5A, 5B and 5C show the construction of the interior of the voltage-control oscillator 1 and the mixer 3. As shown in Fig. 5A, inside the voltage-control oscillator 1, the dielectric strips 16a and 16b which connect to the dielectric strip 12 of the antenna-shared distributor 2 are provided, and an oscillation circuit 18 is provided on the substrate interposed between these two dielectric strips 16a and 16b. Further, inside the mixer 3, dielectric strips 17a and 17b which connect to the dielectric strip 13 of the antenna-shared distributor 2 are provided, and a mixer circuit 19 is formed on the substrate interposed between these two dielectric strips 17a and 17b. Fig. 5B is an enlarged view of the oscillation circuit 18. A suspended line 25 extends in a direction normal to the dielectric strips 16a and 16b, and a conductor pattern 26 for RF choke and further electrodes 23 and 24 are connected to the end of the suspended line 25. One pole of a Gunn diode 27 is connected to the suspended line 25. A varactor diode 28 is connected between the conductor pattern 26 for RF choke and the suspended line 25. The other pole of the Gunn diode 27 is grounded, and the application of a bias voltage to the Gunn diode between the electrode 23 and the ground causes the Gunn diode to oscillate. Since the conductor pattern 26 for RF choke can be assumed to be grounded in a high frequency region, the varactor diode 28 is connected equivalently in parallel to the Gunn diode 27. A modulation signal applied between the electrodes 23 and 24 causes the electrostatic capacity of the varactor diode to change, causing the oscillation frequency of the Gunn diode to be modulated. Fig. 5C is an enlarged view of the mixer circuit 19. The conductor patterns 26 for RF choke extend in a direction normal to the dielectric strips 17a and 17b, and electrodes 29 and 30 are formed in the end portions of the conductor patterns 26. A Schottky barrier diode 31 is mounted in that portion between the end portions of the two conductor patterns for RF choke which is interposed between the dielectric strips 17a and 17b. The Schottky barrier diode 31 is coupled to an RF signal and an Lo signal which are propagated through the dielectric strips 17a and 17b and generates an IF signal when a bias voltage is applied between the electrodes 29 and 30. Figs. 6A, 6B and 6C show two other construction examples of the antenna-shared distributor. A dielectric rod 40 which goes through the conductor plate 14 and connects to the dielectric resonator 11, such as that shown in Fig. 6A, may be provided. This dielectric rod 40 functions as a dielectric rod antenna, making it possible to increase the directivity of the antenna. Further, as shown in Figs. 6B and 6C, a plate 41 having a slot may be disposed between the dielectric resonator 11 and the conductor plate 14. The plate 41 may be such that an opening of any desired pattern is formed within a metallic plate or any desired pattern is formed by removing a part of a conductor plate on the circuit substrate. Varying the slot arrangement pattern makes it possible to control the directivity of radio waves from the antenna. Fig. 7A shows the internal construction of a transmission and receiving apparatus according to a second embodiment of the present invention. An oscillation signal from an oscillation circuit 38 is supplied to the antenna-shared distributor 2 via a circulator 42. A signal from the antenna-shared distributor 2 to a voltage-control oscillator 100 is supplied to a terminater 43 via the circulator 42. In the apparatus of Fig. 7A, the isolator 42 and the voltage-control oscillator 100 are different modules. Of course, as shown in Fig. 7B, all of an isolator 42', a terminater 43', and an oscillation circuit 18' may be housed inside a voltage-control oscillator 150. Fig. 8 shows the interior construction of a transmission and receiving apparatus according to a third embodiment of the present invention. The dielectric strips 12 and 13 are made to intersect at right angles to each other. When a transmission signal of the LSM01 mode is supplied from the voltage-control oscillator 1 via the dielectric strip 12 to the antenna-shared distributor 2, the dielectric resonator 11 excites in the HE111 mode and radiates a linearly polarized electromagnetic wave in the forward direction of Fig. 8, and at the same time radiates a signal of the LSE01 mode to the dielectric strip 13. This LSE01-mode signal becomes a Lo signal to the mixer 3. A reflection signal from the target object is made to enter the dielectric resonator 11 and an RF signal therefrom is supplied to the mixer 3 in the LSE01 mode. The power distribution ratio of the radiation power of the transmission signal to the Lo signal may be set according to the spacing between the dielectric resonator 11 and the dielectric strips 12 and 13. Fig. 9A is a sectional view of a transmission and receiving apparatus according to a fourth embodiment of the present invention. A part of the case 5 extends up to near the dielectric resonator 11. A opening portion H is formed above the dielectric resonator 11 in the extension portion of the case 5. The slope of the extension portion in which the opening portion H is formed forms the horn. In a fifth embodiment shown in Fig. 9B, the circuit unit 4 may be disposed within the case 5. In a sixth embodiment shown in Fig. 9C, a dielectric lens formed of a lamination of dielectric layers 61a to 61n having mutually different specific inductive capacity and a dielectric convex lens element 60 may be used. In this case, by decreasing the specific inductive capacity in such a way that the specific inductive capacity becomes smaller gradually from the topmost dielectric layer 61a to the bottommost dielectric layer 61n, the dielectric lens can be made thin. Figs. 10A1 and 10A2 show another dielectric line for use in a transmission and receiving apparatus of the present invention. A normal-type dielectric line 500 in which grooves are not formed in the upper and lower conductor plates may be used in an antenna-shared distributor. A dielectric line with a circuit substrate 506 interposed in the middle thereof may be used in the voltage-control oscillator and the mixer. As shown in Figs. 10B1 and 10B2, a wing-type dielectric line such that wings 503' and 504' extend to the right and left in the figures from dielectric lines 503 and 504 may be used. The wing-type dielectric lines 503 and 504 with the circuit substrate 506 interposed therebetween may be used. The compact and simple antenna-shared distributor and the transmission and receiving apparatus using such distributor according to the present invention makes it possible to save space when they are mounted in a vehicle. Further, the simple construction increases fault tolerance.

Claims: An antenna-shared distributor, characterized by two facing conductor sections (14, 15); a dielectric resonator (11) disposed between said conductor sections (14, 15); a non-conductor section which is provided in at least one of said conductor sections (14, 15) and which faces said dielectric resonator (11); a first dielectric line (12) disposed close to said dielectric resonator (11); and a second dielectric line (13) disposed close to said dielectric resonator (11). An antenna-shared distributor according to claim 1, wherein said non-conductor section is a hole (o) which goes through the conductor section (14). An antenna-shared distributor according to claim 1, further comprising: grooves which are provided in said conductor section and which hold said dielectric line. An antenna-shared distributor according to claim 1, further comprising: a dielectric wing section which extends along the surface of said facing conductor section from said dielectric line. An antenna-shared distributor according to claim 1, further comprising: a dielectric rod (40) which couples electromagnetically to said dielectric resonator (11). An antenna-shared distributor according to claim 5, wherein said dielectric rod (40) goes through said non-conductor section (o). An antenna-shared distributor according to claim 1, wherein said non-conductor section is a slot provided in said non-conductor section. A transmission and receiving apparatus, comprising: an oscillator (1; 100; 150); and a mixer (3); characterized by an antenna-shared distributor (2) including: two facing conductor sections (14, 15); a dielectric resonator (11) disposed between said conductor sections (14, 15); a non-conductor section which is provided in at least one of said conductor sections and which faces said dielectric resonator (11); a first dielectric line (12) disposed close to said dielectric resonator (11); and a second dielectric line (13) disposed close to said dielectric resonator (11); wherein said oscillator (1; 100; 150) is coupled to said first dielectric line (12); and wherein said mixer (3) is coupled to said second dielectric line (13). A transmission and receiving apparatus according to claim 8, wherein said oscillator (1) includes: a third dielectric line (16a, 16b) coupled to said first dielectric line (12); and an oscillating circuit (18) coupled to said third dielectric line (16a, 16b). A transmission and receiving apparatus according to claim 9, wherein said oscillator includes: a suspended line (25) coupled to said third dielectric line (16a, 16b); an RF choke (26) connected to said suspended line (25); and electrodes (23, 24) connected to said RF choke (26). A transmission and receiving apparatus according to claim 8, wherein said mixer (3) includes: a fourth dielectric line (17a, 17b) coupled to said second dielectric line (13); and a mixer circuit (19) coupled to said fourth dielectric line (17a, 17b). A transmission and receiving apparatus according to claim 11, wherein said mixer circuit includes: a switching element (31) coupled to said fourth dielectric line (17a, 17b); an RF choke (26) connected to said switching element (31); and electrodes (29, 30) connected to said RF choke (26). A transmission and receiving apparatus according to claim 8, further comprising: a horn-shaped electromagnetic guide (H) disposed around said non-conductor section. A transmission and receiving apparatus according to claim 9, wherein said oscillator includes: a circulator (42) having three terminals, inserted in the middle of said third dielectric line (16a, 16b), two terminals of which are coupled to said third dielectric line (16a, 16b); and a terminator (43) connected to the rest terminals of said circulator (42). A transmission and receiving apparatus according to claim 8, wherein said first dielectric line (12), said second dielectric line (13) and said dielectric resonator (11) are provided in line with each other. A transmission and receiving apparatus according to claim 8, wherein the line which connects the extension line of said dielectric resonator (11) and said first dielectric line (12) substantially intersects at right angles to the line which connects the extension line of said dielectric resonator (11) and said second dielectric line (13). A transmission and receiving apparatus according to claim 8, further comprising: a dielectric lens (7) at a position facing said non-conductor section.

Inventors: ISHIKAWA YOHEI, NISHIDA HIROSHI, SAITOH ATSUSHI, TANIZAKI TORU, ISHIKAWA, YOHEI, NISHIDA, HIROSHI, SAITOH, ATSUSHI, TANIZAKI, TORU
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: G01S7
IPC codes: G01S7, H01Q1, H01Q13, G01S13, H01Q19, H01P1, H03D9, H01P5, H04B1, H01P3