Electronic circuit device

Abstract: An electronic circuit device comprises a printed circuit board (3) having a first surface on which a circuit pattern (6) is formed on which components (7) are mounted and a second surface on which a ground plane (5) is formed, a coupling stub (15) being formed in part of the circuit pattern; and a plane antenna having an antenna element (1), formed on one surface of a dielectric substrate (2). The printed circuit board (3) and the plane antenna are unified such that the second surface of the printed circuit board (3) and the other surface of the dielectric substrate (2) are opposed to each other and the coupling stub (15) is placed in position to be coupled to the antenna element (1).

Description: Background of the Invention The present invention relates to an electronic circuit device according to the preamble of claim 1 which is known from US-A-4 724 443, and more particularily to an electronic circuit device which is useful where low cost is a requirement. Microstrip patch antennas are widely used with mobile radio communication devices utilizing microwaves and have features of low cost and ease of manufacture, as well as low profile and high gain. Demand is increasing for less expensive, more easily manufactured electronic circuit devices which include plane antennas such as microstrip patch antennas as described above. Figures. 1A and 1B illustrate an example of a prior art electronic circuit device which includes a plane antenna used as a discrete component. Figure 1A is a perspective view and Figure 1B is a side sectional view. In these Figures, reference numeral 1 denotes an antenna element, 2 an antenna substrate, 3 a printed circuit board, 4 a substrate of printed-circuit board 3, 5 a ground plane, 6 a circuit pattern, 7 discrete components, 8 a microwave transmitting/receiving section, 9 a feed point to the antenna element 1, and 10 a connecting pin. In Figures 1A and 1B, antenna element 1 is made of a conductor and is square, the length of one side measuring about λ/2 (λ is a wavelength used) long. It is formed on antenna substrate 2, which is made of a dielectric material, and has a contour larger than the antenna element, thereby constituting a microstrip patch antenna. With printed circuit board 3, ground plane 5 comprising a couductor covers the surface of substrate 4, which comprises of a dielectric material. Circuit pattern 6 is formed on the other side of substrate 4. Circuit pattern 6 has a circuit comprising of a microstrip line and is fixed in its prescribed positions by components 7. Antenna substrate 2 is mounted on that portion of ground plane 5 which corresponds in position to microwave transmitting/receiving section 8 on circuit pattern 6 by bonding with antenna element 1 turned up. Feed point 9 and microwave transmitting/receiving section 8 are connected by connecting pin 10, which passes through printed-circuit board 3. Figures 2A and 2B illustrate another example of the prior art electronic circuit device, which includes a plane antenna formed interrally with a case for housing an electronic circuit. Figure 2A is a perspective view and Figure 2B is a side sectional view. In these Figures, reference numeral 11 designates an antenna conductor plate and 12 a package. In Figures 2A and 2B, antenna conductor plate 11 is bonded to the top surface of package 12, which is formed of a dielectric material. Printed circuit board 3, as in Figures 1A and 1B, is mounted on the inner surface of package 12 with circuit pattern 6 turned down. Microwave transmitting/receiving section 8 on circuit pattern 6 and feed point 9 of antenna conductor plate 11 are connected to each other by means of connecting pin 10, which passes through package 12 and printed circuit board 3. With the prior art electronic circuit device shown in Figures 1A and 1B, antenna element 1 and connecting pin 10 are usually soldered together. Thus, a heat-resisting dielectric material such as glass epoxy is used for antenna substrate 2. This makes antenna substrate 2 difficult to manufacture by die molding. Moreover, holes must be bored in antenna substrate 2 and printed circuit board 3, the holes must be aligned with each other and soldering is required. This raises the manufacturing cost. In the prior art electronic circuit device shown in Figures 2A and 2B, the material used for package 12 usually has no heat resistance. Thus, antenna conductor plate 11 and connecting pin 10 have to be connected beforehand by welding or soldering. This gives additional trouble and requires that antenna conductor plate 11 be made thicker. This raises the manufacturing coast. From EP-A-0 271 458 it is known to form a coupling stub as a part of a ground plane. Summary of the Invention It is an object of the present invention to provide an electronic circuit device of the above type which can be manufactured easily and inexpensively. This object is solved by an electronic circuit device of the initially defined type having the characterizing features of claim 1. Preferred embodiments are listed in the dependent claims. Brief Description of the Drawings Figures 1A and 1B are a pesrpective view and a side view, respectively, of a prior art electronic circuit device using a plane antenna, Figures 2A and 2B are a perspective view and a side sectional view, respectively, of another prior art electronic circuit device using a plane antenna, Figures 3A and 3B are a perspective view and a side sectional view of an embodiment of the present invention, Figures 4A and 4B are a perspective view and a side sectional view of another embodiment of the present invention, Figure 5 is a perspective view and a side sectional view of still another embodiment of the present invention, Figures 6 is a perspective view and a side sectional view of further embodiment of the present invention, Figures 7A and 7B are a perspective view and a side sectional view of still further embodiment of the present invention, Figure 8 illustates a circuit arrangement of the embodiment, and Figure 9 is an equivalent circuit diagram of the embodiment shown in Figure 8. Description of the Preferred Embodiments As shown in embodiments of Figs. 3A through 7B, an electronic circuit device of the present invention includes a printed-circuit board 3 and a plane antenna 14. The bottom surface of plane antenna 14 is unified to the top surface of printed-circuit board 3. These surfaces have no antenna element opposed to each other, and at least one coupling stub 15, 18 or 20 is placed in position to be coupled to antenna element 1. Printed-circuit board 3 has circuit pattern 6 formed on its bottom surface and ground plane 5 formed on its top surface. Various components are mounted on circuit pattern 6. Part of ground plane 5 forms at least one coupling stub 15, 18 or 20 which is connected to circuit pattern 6. Circuit pattern 6 is formed on the bottom surface of printed circuit board 3 and components 7 are mounted on circuit pattern 6. Ground plane 5 covers the top surface, or the reverse side of printed circuit board 3. Coupling stubs 15, 18 or 20, connected with microwave transmitting/receiving section 8 on circuit pattern 6, are formed on part of ground plane 5. Plane antenna 14 has antenna element 1 formed on antenna substrate 2 or package 12 which are made of a dielectric material. The bottem surface of plane antenna 14 is bonded to the top surface of printed circuit board 3. These surfaces have no antenna element opposed to each other, and coupling stub 15, 18 or 20 is placed in position to be coupled to antenna element 1. Microwave transmitting/receiving section 8 on circuit pattern 6 of printed circuit board 3 and antenna element 1 are thereby coupled to each other through coupling stub 15, 18 or 20 for transmission of microwave power therebetween. Thus, a microwave can be transmitted from printed circuit board 3 via antenna element 1 or received by printed circuit board 3 through antenna element 1. In the electronic circuit device of the present invention, antenna element 1 is not directly connected to printed circuit board 3. This obviates the need for welding or soldering of antenna element 1. Thus, the antenna itself can be manufactured inexpensively and the number of manufacturing processes reduced. Figs. 3A and 3B show an exploded perspective view and aside sectional view of an electronic circuit device according to a first embodiment of the present invention. Like reference numerals are used to designate parts or components corresponding to those in Figs. 1A and 1B. Reference numeral 15 designates a coupling stub, 16 a feed point of coupling stub 15, and 17 a through hole adapted to connect feed point 16 to microwave transmitting/receiving section 8. In Figs. 3A and 3B, antenna element 1 is made of a conductor and is square or rectangular, the length of one side measuring about λ/2. The antenna element comprises a thin metal film formed on the antenna substrate 2 by deposition or plating and having a somewhat larger contour than antenna element 1. Alternatively, antenna element 1 may be fabricated by bonding a metallic foil to antenna substrate 2 with adhesive tape or attaching a conductor plate to the antenna substrate by suitable means. Antenna pattern 1 and antenna substrtate 2 constitutes a microstrip patch plane antenna 14. Printed circuit board 3 is formed , for example, of a glass epoxy plate covered with copper. Ground pattern 5 is formed to cover the whole surface of substrate 4, which consists of an insulating material, and circuit pattern 6 is formed on the reverse side of substrate 4. A microstripline circuit is formed on circuit pattern 6, and components 7 are mounted in positions to form a desired cirtcuit. Part of ground plane 5 is cut out to form coupling stub 15d. Feed point 16 of coupling stub 15 and microwave transmetting/receiving section 8 on printed circuit board 3 are connected to each other by means of through hole 17. Antenna substrate 2 is attached, for example, by bonding, to that portion of ground plane 5 where coupling stub 15 is provided, with coupling stub 15 oriented parallel to one side of antenna element 5 and antenna element 5 turned up. Coupling stub 15 forms a quarter-wavelength (λ/4) open-end stub. By being connected to microwave transmitting/receiving section 8, coupling stub 15 is coupled to antenna element 1 to provide a feed mode in which a node is produced in the center of antenna element 1 in the direction orthogonal to coupling stub 15. Thus, microwave power is transmitted between microwave transmitting/receiving section 8 and antenna element 1 so that the microwave is transmitted or received through antenna element 1. Figs. 4A and 4B are a perspective view and a sectional view, respectively, of a second embodiment of the present invention in which like reference numerals are used to designate parts corresponding to those in Figs. 3A and 3B. In Figs. 4A and 4B, antenna element 1 is provided on the top surface of dielectric package 12, which is formed integrally with the antenna substrate, as in the embodiment of Figs. 1A and 1B. In this case as well, antenna element 1 and package 12 forms plane antenna 14. To the inner surface of package 12 is attached printed circuit board 3, as in the first embodiment of Figs. 1A and 1B, with circuit pattern 6 turned down. Antenna pattern 1 is formed on that portion of the top surface of package 12 which corresponds to coupling stub 15 in printed circuit board 3. In this embodiment as well, coupling stub 15 forms a quarter-wavelength (λ/4) open-end stub. By being connected to microwave transmitting/receiving section 8, coupling stub 15 is coupled to antenna element 1 so that microwave power is transmitted between microwave transmitting/receiving section 8 and antenna element 1, thus transmiting or receiveing a microwave from antenna pattern 1. Fig. 5 is an exploded perspective view of a third embodiment of the present invention in which like reference numerals are used to designate parts corresponding to those in Figs. 3A and 3B. Reference numeral 18 designates a coupling stub and 19 a feed point of coupling point 18. Coupling stubs 15 and 18 are formed parallel to two adjoining sides of antenna element 1 with their feed points 16 and 19 connected by means of through holes to microwave transmitting/receiving section 8 on the printed circuit board. When coupling stubs 15 and 18 are fed in parallel and in phase, a feed mode is produced in which a node is produced along a diagonal line of antenna element 1. However, when coupling stubs 15 and 18 are fed in phase quadrature through a phase shifting means, a circularly polarized wave feed mode results. Fig. 6 is a perspective view of a fourth embodiment of the present invention. This embodiment is distinct from the above embodiments in that antenna element 1 covers the surface of antenna substrate 2. According to the embodiment of Fig. 6, antenna element 1 and antenna substrate 2 can be easily manufactured by cutting a dielectric plate having its whole surface covered with a conductor foil. Figs. 7A and 7B are an exploded view and a side sectional view, respectively, of a fifth embodiment of the present invention. In the Figures, like reference numerals are used to designate parts corresponding to those in Figs. 3A and 3B. Reference numeral 20 designates a coupling stub and 21 a feed point. In the embodiment of Figs. 7A and 7B, coupling stub 20 is formed by clipping ground plane 5 to form a quarter-wavelength (λ/4) shorted stub. As in the embodiment of Figs. 3A and 3B, by connecting feed point 21 to microwave transmitting/receiving section 8, coupling stub 20 is coupled antenna element 1 to provide a feed mode which is produced in the center of antenna element 1 in the direction orthogonal to coupling stub 20. Thus, microwave power is transmitted between microwave transmitting/rerceiving section 8 and antenna element 1, so that the microwave is transmitted to or received from antenna element 1. The microwave transmitting/receiving section connected to the coupling stub will next be described in detail. Fig. 8 is a schematic diagram of the microwave transmitting/receiving circuit and Fig. 9 is its equivalent circuit diagram. In Fig. 8, coupling stub is formed parallel to one side of antenna element 1 and a matching circuit 20 is connected to an end of coupling stub 15. As described above, antenna element 1 and coupling stub 15 are coupled to each other via dielectric antenna substrate 2. Coupling stub 15 is provided on the side of printed circuit board 3 opposite to the side on which matching circuit 20, modulating diode 21 and chip resistor 22 are mounted. Coupling stub 15 and matching circuit 20 are connected to each other by a through hole at feed point 16. In Fig. 8, the solid lines represent components mounted on printed circuit board 3. To avoid coupling with other circuits, coupling stub 15 is provided in a position where no components are mounted. The matching circuit connected to coupling stub 15 is adapted to match modulating diode 21, to be described later, with the coupling stub. The other end of the matching circuit is connected to the anode of modulating diode 21 and a bias circuit 23 which connects the anode of the diode to ground. Bias circuit 23 is formed of a line having a characteristic impedance which is much higher than that of the microstrip line, e.g., the characteristic impedance of matching circuit 20, and has a length of about quater the wavelength used (λ/4). This will provide a high impedance for signals within a microwave frequency band in use. In the equivalent circuit of Fig. 9, matching circuit 20 and coupling stub 15 are represented together by a coupling capacitor C and bias circuit 23 is represented by a biasing (grounding) coil L. The cathode of modulating diode 21 is connected to a line having a low characteristic impedance and a length of about λ/4. This line serves to connect the cathode of modulating diode 21 to ground for signals within the frequency band used and is represented by a capacitor CG in the equivalent circuit of Fig. 9. Modulating diode D is equivalently connected to antenna A under a matched condition and its cathode is connected to ground. On the other hand, the cathode of modulating diode D is connected to a signal generating integlated circuit (IC) SG via a resistor R. Signal generating integrated circuit SG generates a code signal to be transmitted. Each electronic circuit device is allocated a separate code beforehand. The embodiment of Fig. 8 is adapted to generate a signal representing which of a number of parts is moving on a belt conveyer in a factory. For this reason, serial date such as a code generated by signal generating integrated circuit SG is applied to the cathode of modulating diode D. Modulating diode D is a variable capacitance diode whose capacitance varies with the code output from signal generating integrated circuit SG. In the embodiment of Fig. 8, a unmodulated wave (CW) is generated by a fixed station, which is received by antenna 1 and then applied to modulating diode D via matching circuit 20. Thus, the unmodulated wave is phase modulated with variation in diode capacitance. The phase modulated wave is transmitted in the opposite direction to the input unmodulated wave CW and is then outputted from antenna A. Though not shown, the fixed station includes an oscillator for generating an unmodulated wave and a homodyne detector. That is, the fixed station detects the modulated wave produced by modulating diode 21 and transmitted from antenna A to recover a signal (code) generated by signal generating integrated circuit SG. By this operation, the unmodulated wave CW generated by the fixed station is received and modulated, and the modulated wave is returned to the fixed station. In the embodiment of the present invention, each mobile station is provided with the circuit of Fig. 8 and the code generated by signal generating IC SG varies from mobile station to mobile station. Thus, when a mobil station enters an area where an unmodulated wave generated by a fixed station can be received and a modulated wave can be returned to the fixed station, the type of mobile station can be clearly identified by the fixed station. For example, where various types of parts are moving on a belt conveyer, if each type of part is assigned a separate code by signal generating integrated circuit SG, then the types of moving parts can be identified. In addition, in the present invention, since a received signal is modulated and then returned, there is no need for an oscillator to generate a microwave signal. It is only required to drive signal generating integrated circuit SG, thus making battery drive possible as shown in Fig. 8. As described above, according to the present invention, the antenna element and the microwave transmitting/receiving section are not directly connected to each other and the microwave is transmitted through the coupling stub. Therefore, there is no need for welding or soldering for connecting the antenna element and the antenna element need not be made thicker, thus decreasing the number of manufacturing processes and the material cost. The present invention may also be applied to other plane antennas in addition to the microstrip patch antenna described above. Reference signs in the claims are intended for better understanding and shall not limit the scope.

Claims: An electronic circuit device, comprising: a printed circuit board (3) having a first surface on which a circuit pattern (6) is formed on which components (7) are mounted; and a second surface on which a ground plane (5) is formed; a coupling stub (15, 18, 20) being connected to said circuit pattern (6); a plane antenna (14) having an antenna element, formed on one surface of a dielectric substrate (2, 12); said printed circuit board (3) and said plane antenna (14) being unified such that the second surface of said printed circuit board (6) and the other surface of said dielectric substrate (2, 12) are opposed to each other and said coupling stub (15, 18, 20) is placed in position to be coupled to said antenna element; characterized in that said coupling stub (15, 18, 20) is formed as a part of said ground plane (5); said components (7) mounted on said printed circuit board (6) include a modulating diode (21) connected to said coupling stub (15, 18, 20) via a matching circuit (20); and a battery-driven signal generating circuit (SG) coupled to said modulating diode (21) for generating data to be transmitted; wherein an unmodulated wave received by said plane antenna (14) is modulated by said modulating diode (21) in accordance with said data from said battery-driven signal generating circuit (SG) and transmitted outside said plane antenna (14). An electronic circuit device according to claim 1, wherein said modulating diode (21) is a variable capacitance diode (21) which capacitance varies with said data from said battery-driven signal generating circuit (SG) so as to phase-modulate said unmodulated wave. The electronic circuit device according to claim 1 or 2, in which said antenna element has a square shape which measures half the wavelength of a service frequency band. The electronic circuit device according to claim 1 or 2, in which said antenna element has a rectangular shape which one side measures half the wavelength of a service frequency band. The electronic circuit device according to claim 3, in which said coupling stub (15, 18, 20) is a quarter-wavelength-long open stub provided parallel to one side of said antenna element. The electronic circuit device according to claim 3, in which said coupling stub (15, 18, 20) is a quarter-wavelength-long shorted stub provided parallel to one side of said antenna element. The electronic circuit device according to claim 3, in which said coupling stub (15, 18, 20) comprises two stubs provided parallel to two adjoining sides of said antenna element. The electronic circuit device according to claim 1, in which said dielectric substrate (2, 12) on which said antenna element is formed, is formed of part of a case surrounding said printed circuit board (3).

Inventors: SUGAWARA HIDEO, SUGAWARA, HIDEO
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1990
Main classification: H01Q9
IPC codes: H01P3, H01Q9, H01Q13, H01P5