Abstract:
An oscillator wherein deviation in the position of a cap of a package is monitored when removing and replacing the cap to adjust the characteristics of the oscillator, and which has stable characteristics. The oscillator comprises a package, a resonator stored in the package, a circuit board and a member for securing the package, the member for securing being attached to the circuit board and contacting two opposing inside faces of the package.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an oscillator and a communications device in which a circuit board and a resonator and the like are stored in a package. 
     2. Description of the Related Art 
     By way of background, an example of an oscillator will be discussed as shown in FIGS. 6 and 7, it being understood that this oscillator was not known at the time of the present invention and, therefore, is not prior art to the instant application. FIG. 6 is an exploded perspective view of the oscillator, and FIG. 7 is a cross-sectional view taken along the line Z—Z of FIG.  6 . 
     As shown in FIGS. 6 and 7, oscillator  110  comprises a package  111 , a case  130 , a resonator  120  and a circuit board  140 . The package  111  comprises a steel cap  112  and a stem  113 . Terminal pins  114  are provided at three corners of the stem  113 . The case  130  has a two-level concave portion  131  in its center, and is provided on top of the stem  113 . The resonator  120  comprises an electrode  122 , which is provided on two opposing faces of a dielectric substrate  121 , and a substantially circular electrode removal portion  123  is provided roughly in the center of the electrode  122 . Furthermore, the electrode  122  is also provided on the four side faces of the dielectric substrate  121 . The resonator  120  is held in the concave portion  131  of the case  130 , and the two-level structure of the concave portion  131  creates a space near an electrode removal portion  123  in the bottom face of the resonator  120 . 
     The circuit board  140  comprises a circuit pattern, such as a stripline, provided on an insulated substrate  141 . A FET  142 , a varactor diode  152 , a chip capacitor  143  and chip resistors  144   a ,  144   b  and  144   c  and the like are provided at predetermined positions on the substrate  141 . The circuit board  140  is mounted on the case  130 , and terminal electrodes  149 ,  150  and  153  of the circuit board  140  are connected to the terminal pins  114 . 
     The case  130 , with the resonator  120  therein, is placed on the stem  113  and the circuit board  140  is mounted on the case  130 . Thereafter, a cap  112  is provided over the assembly. The cap  112  is hermetically sealed to the stem  113 , forming the oscillator  110 . 
     The characteristics of an oscillator are greatly affected by the relative positions of the resonator and the circuit board or the cap. That is, when the positions of the resonator and the cap change, the distribution of the electromagnetic field changes, greatly affecting the characteristics of the oscillator. This effect is particularly noticeable at high-frequency bands such as microwave and milliwave bands, which require positioning with precision of below 0.1 mm. 
     Therefore, in order to obtain the desired characteristics, it is necessary to repeatedly measure the characteristics of the oscillator while adjusting the relative position. Each time, the cap and the circuit board are removed and the position of the resonator is altered. Then, the circuit board is remounted and the cap is replaced. 
     However, some deviation in position of the cap inevitably occurs each time the cap is replaced. Consequently, when the cap is removed and the position of the resonator and the like is altered, the deviation in the position of the cap thereafter changes the distribution of the electromagnetic field, making it difficult to measure characteristics of the oscillator appropriately and with stability. Furthermore, due to the deviation in the position of the cap, the path of a ground electrode from the cap to the stem is also unstable, affecting the characteristics of the oscillator. 
     SUMMARY OF THE INVENTION 
     The oscillator of the present invention has been realized in consideration of the problems described above. 
     The oscillator of the present invention comprises a package, a resonator held in the package; a circuit board; and a member for securing the package, the member for securing contacting two opposing inside faces of the package. 
     Consequently, the cap of the package is secured, and the electromagnetic field distribution of the oscillator is stable. 
     Preferably, the member for securing comprises a metal plate, connected in one direction to a ground electrode of the circuit board. 
     Consequently, the path of ground current is stabilized. 
     Preferably, the member for securing, which contacts two opposing inside faces of the package, has an elastic member for securing which contacts one inside face, and a rigid member for securing which contacts the other inside face. 
     Consequently, the force applied to the cap by the member for securing is not excessive. 
     Preferably, the member for securing contacts inside faces of the package in two directions, which are roughly at a right angle to each other. 
     Consequently, the cap is secured with more stability. 
     Preferably, the member for securing comprises a single plate-like member. 
     Consequently, the member for securing needs only a small number of components, making it easier to form. 
     The member for securing, which contacts one of the inside faces of the package, preferably has a sawtooth shape. 
     Consequently, the member for securing contacts the inside face of the package at many points. 
     A communications device of the present invention comprises a circuit for transmitting, a circuit for receiving and an antenna, the circuit for transmitting and/or the circuit for receiving comprising the above oscillator. 
     As a result, a communications device with stable characteristics can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of an oscillator of the present invention; 
     FIG. 2 is a cross-sectional view taken along the line X—X of FIG. 1; 
     FIG. 3 is an exploded perspective view of a second oscillator of the present invention; 
     FIG. 4 is a cross-sectional view taken along the line Y—Y of FIG. 3; 
     FIG. 5 is a schematic view of a communications device of the present invention; 
     FIG. 6 is an exploded perspective view of a general oscillator; and 
     FIG. 7 is a cross-sectional view taken along the line Z—Z of FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An oscillator according to an embodiment of the present invention is discussed with reference to FIGS. 1 and 2. 
     As shown in FIGS. 1 and 2, the oscillator  10   a  of the present invention comprises a package  11 , a case  30 , a resonator  20 , a circuit board  40  and a member for securing  60 . The package  11  comprises a cap  12  and a stem  13 . The cap  12 , the case  30  and the stem  13  should preferably have roughly the same coefficient of linear expansion as the resonator  20 . For instance, they may comprise steel. The cap  12  and the stem  13  are hermetically sealed together. Furthermore, terminal pins  14  are provided at three corners of the stem  13 . 
     The resonator  20  comprises an electrode  22 , provided on two opposite faces of a dielectric substrate  21 , and a substantially circular electrode removal portion  23  is provided roughly in the center of the electrode  22 . Furthermore, the electrode  22  is also provided on the four side faces of the dielectric substrate  21 , and functions as a ground. The resonator  20  of such a constitution functions as a resonator when an electromagnetic field becomes concentrated near the substantially circular electrode removal portion  23 . 
     A concave portion  31 , into which the dielectric resonator  20  is disposed, is provided roughly in the center of the case  30 . A step projects from the inner wall of the concave portion  31 . This step should be wide enough to support the bottom face of the resonator  20 . Consequently, a space is formed below the electrode removal portion  23 , provided in the bottom face of the resonator  20  and the stem  13  (FIG.  2 ). 
     The circuit board  40  comprises a stripline pattern on an insulated substrate  41 , a FET  42 , a chip capacitor  43 , chip resistors  44   a ,  44   b  and  44   c , a film-like terminal resistor  45  and a varactor diode  52 . One end of a main line  46 , comprising a stripline, is connected to the gate of the FET  42 , and the other end is connected to a film-like terminal resistor  45 . Furthermore, the stripline  47 , which connects to the source of the FET  42 , is connected via the chip resistor  44   a  to a ground electrode  48   a . One of the striplines connecting to the drain of the FET  42  is connected via the chip resistor  44   b  to an input terminal electrode  49 . The input terminal electrode  49  connects via the chip capacitor  43  to a ground electrode  48   b . The drain of the FET  42  is connected via a capacitor component, comprising a gap provided in the stripline, to an output terminal electrode  50 . 
     An auxiliary line  51 , comprising a stripline, is connected at a predetermined position via the varactor diode  52  to the ground electrode  48   a . Furthermore, a stripline is extracted at another position on the auxiliary line  51 , and connects via the chip resistor  44   c  to a bias terminal electrode  53 . When a voltage is applied to the varactor diode  52 , the capacitance of the varactor diode  52  changes, whereby the oscillating frequency of the oscillator  10  can be changed. 
     The member for securing  60  is formed by working a metal such as phosphoric bronze. Two adjacent sides  61   a  and  61   b  of the flat plate-like member for securing  60  have a sawtooth-shape, and the other two sides  62   a  and  62   b  are straight. The sawtooth shape of the two sides  61   a  and  61   b  provides elasticity, and the straight shape of the other two sides  62   a  and  62   b  provides rigidity. Furthermore, when forming the oscillator  10   a , a hole  63  is preferably provided roughly in the center of the member for securing  60 , which is clasped between the resonator  20  and the circuit board  40 , in order to achieve electromagnetic coupling between the resonator  20  and the striplines of the circuit board  40 . The member for securing  60  has a slightly larger area than the opening of the cap  12  as viewed from above such that when the cap  12  is mounted on the stem  13 , part of the member for securing  60  contacts the inner walls of the cap  12 , and the resilient characteristic of the member for securing  60  firmly secures it to the cap  12 . 
     The case  30  is provided on the stem  13  and the resonator  20  is housed in the concave portion  31  of the case  30 . The member for securing  60  is mounted to the case  30 , and the circuit board  40  is mounted above the member for securing  60 . After the circuit board  40  has been mounted, the circuit board  40  and the member for securing  60  and the case  30  are fixed in place by a screw  64  (or other suitable element). As a result, the ground electrode on the bottom surface of the circuit board  40 , connected via a through hole to the ground electrodes  48   a  and  48   b  on the top surface of the circuit board  40 , is connected to the member for securing  60 . The member for securing  60  may be connected to the circuit board  40  and the case  30  using a conductive adhesive or the like. 
     The terminal pins  14 , provided at three corners of the stem  13  and the case  30 , are inserted through holes  55   a ,  55   b  and  55   c , provided respectively in the input terminal electrode  49 , the output terminal electrode  50  and the bias terminal electrode  53  of the circuit board  40 , and connect respectively to the terminal electrodes  49 ,  50  and  53 . The holes  55   a ,  55   b  and  55   c , provided in the circuit board  40 , are the same shape as the terminal pins  13  so as to be always connected thereto. 
     Thereafter, when the cap  12  is placed over the top as shown in the cross-sectional view of FIG. 2, as a result of the elasticity of the sawtooth-shaped ends  61   a  and  61   b  of the member for securing  60  and the rigidity of the straight ends  62   a  and  62   b , the sawtooth-shaped end  61   a  bends downward and contacts the inside wall of the cap  12 . The cap  12  receives the force of the member for securing  60  on its inside face, thereby securing the position of the cap  12 . Therefore, when the cap  12  is removed, in order to adjust the positions of the resonator  20  and the circuit board  40 , and then replaced, the position of the cap  12  remains fixed. Furthermore, since a metal member for securing  60  is used, the ground electrodes of the circuit board  40  are connected to the cap  12  by the member for securing  60 . As a consequence, the ground current flowing through the cap  12  passes through the member for securing  60 , and the stable positional relationship between the cap  12  and the member for securing  60  ensures a stable ground current path. As is clear from the above explanation, the area of the open portion of the cap  12  and the area of the member for securing  60  are determined so as to achieve the above action. The exact area depends on the rigidity of the member for securing  60 , and the rigidity of the cap  12 , and the like. The area should be determined so that the device can be secured in the manner described above. 
     In the present embodiment, the member for securing  60  is made elastic by having ends  61   a  and  61   b  which have a sawtooth shape, but alternatively, the ends of the member for securing  60  may be made elastic by, for instance, reducing their thickness. Furthermore, in the present embodiment, opposing inside faces of the cap  12  in two directions are secured by the member for securing  60  having elastic ends  61   a  and  61   b  and rigid ends  62   a  and  62   b , but the cap  12  can be secured when both ends of the member for securing  60  are rigid. Moreover, in the present embodiment, the member for securing  60  comprises phosphoric bronze, but it may for instance comprise conductive rubber or the like. 
     The present embodiment described a voltage-controlled oscillator using a varactor diode  52 , but the present invention is not limited to this. For instance, the present invention can be applied to an oscillator which does not use an auxiliary line portion, or to an oscillator which uses a gunn diode instead of the FET  42 , or such like. 
     A second embodiment of the present invention will now be described with reference to FIGS. 3 and 4. Portions which are the same as in the previous embodiment are represented by the same reference numerals. 
     In this embodiment, a member for securing  70  comprises two metal pieces  71   a  and  71   b . The end of one metal piece  71   a  has a sawtooth shape, and the end of the other metal piece  71   b  is straight. The two metal pieces  71   a  and  71   b  are affixed to the ground electrodes  48   a  and  48   b  on the top face of the circuit board  40  by screws  64 . Thereafter, as in the first embodiment, when the cap  12  is placed on top, the metal piece  71   a , which has a sawtooth-shaped end, bends downward and contacts the inside face of the cap  12 , as shown in FIG.  4 . The metal piece  71   b  which has a straight end does not bend, and contacts with an inside face of the cap  12  which is opposite to the above inside face. 
     The cap  12  receives the force of the member for securing  70  on its inside face, thereby fixing the cap  12  in position. Therefore, when the cap  12  is removed, in order to adjust the positions of the resonator  20  and the circuit board  40 , and then replaced, the position of the cap  12  remains fixed. Furthermore, since a metal member for securing  70  is used, the ground electrodes of the circuit board  40  are connected to the cap  12  by the member for securing  70 . As a consequence, the ground current flowing through the cap  12  passes through the member for securing  70 , and the stable positional relationship between the cap  12  and the member for securing  70  ensures a stable path of ground current. 
     A communications device of the present invention will now be described with reference to FIG.  5 . 
     The communications device  80  of the present invention comprises a duplexer  81 , comprising a filter for transmitting and a filter for receiving, an antenna  82 , which connects to a terminal for antenna connection of the duplexer  81 , a circuit for transmitting  83 , connected to input/output terminals of the filter for transmitting of the duplexer  81 , and a circuit for receiving  84 , connected to input/output terminals of the filter for receiving of the duplexer  81 . 
     The circuit for transmitting  83  has a power amplifier (PA) for power-amplifying the transmission signal, which passes through the filter for transmitting and is emitted from the antenna  82 . Furthermore, a reception signal is passed from the antenna  82  through the filter for receiving, and is received by the circuit for receiving  84 . After passing a low-noise amplifier (LNA) and a filter (RX) in the circuit for receiving  84 , the signal is input to a mixer (MIX). The base oscillator is a phase-locked loop (PLL), comprising an oscillator (VCO)  10   a  and a divider (DV), and outputs a local signal to the mixer. The mixer outputs at intermediate frequency. 
     As a result, it is possible to provide a communications device which is less time-consuming and inexpensive to manufacture. This embodiment described an example using the oscillator as the circuit for receiving, but the communications device of the present invention is not limited to this, and can be applied when the oscillator is used as the circuit for transmitting, or when an oscillator is used as both. 
     The present invention described above employs a member for securing which contacted the inside face of the cap of a package. As a result, the position of the cap is secured, so that when the cap is removed and then replaced after adjusting the positions of the resonator and the circuit board, its position is always fixed. Therefore, the characteristics of the oscillator can always be measured under the same conditions, making it possible to obtain an oscillator having stable characteristics. 
     Furthermore, a metal member for securing is used, one end thereof being connected to a ground electrode of the circuit board. Consequently, the path of ground current flowing through the cap is stable, making it possible to provide an oscillator having good characteristics. 
     Furthermore, the member for securing comprises an elastic member for securing, which contacts one of two opposite inside faces of the cap, and a rigid member for securing, which contacts the other of the inside faces. Consequently, the elasticity of one inside face allows the cap to receive excess force using the member for securing, reducing the danger that the cap will be warped. 
     Furthermore, the member for securing contacts opposing inside faces of the cap in two directions which are roughly at a right angle to each other. Consequently, the cap can be secured with even more stability than when the member for securing contacts opposing inside faces of the cap in only one direction, making it possible to provide an oscillator with stable characteristics. 
     Furthermore, the member for securing comprises a single plate-like member. Consequently, the number of components can be reduced, and the member for securing can be manufactured easily. Furthermore, even when the member for securing is provided between the case and the circuit board, the circuit board does not shake and remains stable. 
     The elastic portion of the member for securing, which contacts the inside faces of the cap, has a sawtooth shape. Consequently, the member for securing contacts many points on the inside face of the cap, further stabilizing the cap in a secure position. Furthermore, the path of ground current flowing through the cap is stabilized. 
     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.