Abstract:
An oscillator structure includes at least one oscillator circuit and at least one resonator. The oscillator circuit is disposed on a support and the resonator is situated essentially within the support and/or is a constituent part of the support. The resonator is preferably formed by an electrical conductor and the oscillator circuit is preferably formed by an integrated electronic circuit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of copending International Application No. PCT/DE98/03803, filed Dec. 29, 1998, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     FIELD OF THE INVENTION 
     The invention relates to an oscillator structure having at least one oscillator circuit and at least one resonator. 
     Oscillators are electronic oscillation generators, i.e. circuits for producing electrical oscillations. The electrical oscillations generally have a sinusoidal waveform. However, a different waveform, for example in the form of a square, sawtooth, triangular or delta shape, is also possible. The oscillators contain an amplifier and at least one feedback device. An effect produced by the feedback device is that part of an output signal from the amplifier is fed back to its input. 
     A multiplicity of electronic devices contain an oscillator. Besides signal generators, function generators and pulse generators, transmitters and receivers in the radiofrequency to microwave range are of particular interest. 
     An oscillator structure of that generic type may, in particular, be a VCO (voltage controlled oscillator), which is stabilized by a resonator. 
     A special feature of a VCO is that its frequency can be controlled by a voltage applied to it. The oscillator is stabilized by using a resonator. VCOs are suitable both for logic circuits and for radiofrequency applications. When used in the radiofrequency range, an oscillatory response can be tuned by a varactor diode, for example. That allows the oscillator structure to be used in the gigahertz range. 
     The known oscillator structures have proved themselves in many different ways in practice. However, the large dimensions of the oscillator structure are a disadvantage. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide an oscillator structure having at least one oscillator circuit and at least one resonator, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which takes up as little volume as possible and which can be integrated into a housing. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, an oscillator structure, comprising a conductive support; at least one oscillator circuit disposed on the conductive support; and at least one resonator formed by an exposed electrical conductor disposed below the oscillator circuit. 
     Thus, the invention provides for the oscillator structure to be constructed in such a way that the oscillator circuit and the resonator are physically isolated from one another. This allows the oscillator circuit to have the smallest possible dimensions and, at the same time, means that a resonator of sufficient size for the necessary electrical properties can be produced. 
     A reduction in the space requirement for the oscillator structure is achieved by the resonator being situated within a support for the oscillator circuit and/or being a constituent part of that support. 
     The result of placing the oscillator circuit on a support which already contains the resonator is that the dimensions of the oscillator structure can be kept very small. 
     Whereas the resonator is made of an electrically conductive material, the support can be conductive or nonconductive. The term support should in no way be understood as being restrictive. In particular, it should be understood as meaning any mount or base for the oscillator circuit. 
     The support can also be formed by a film, for example. In this case, the conductor is expediently formed by a metalization layer applied to the film. Such a metalization layer can also be used if the support is made from a plastic or ceramic substrate. 
     The support may also be made from a metal and may be in the form of a punched sheet-metal strip (lead frame), for example. 
     The invention also refers, in particular, to the integration of the oscillator structure on the support in a housing, in particular as a component. 
     In this case, the support is disposed in a housing plane, preferably in a lower region of the housing. The oscillator circuit is situated on this support. 
     A further reduction in the necessary space can be achieved by the conductive support part situated below the oscillator circuit containing at least one electrical conductor. 
     In accordance with another feature of the invention, the electrical conductor has a strip shape. Other structures of the electrical conductor, such as a meander shape or a spiral shape, are also expedient, with the selected shape being matched to the frequency. 
     The construction of the electrical conductor as an exposed part of a conductive support, which is connected to the support at one end, has the particular advantage of permitting a part of the support surface which is below the oscillator circuit to be used directly for forming an electrical resonant circuit. In this case, in an electrical equivalent circuit diagram, the exposed conductor represents an inductor, defined by the mechanical dimensions of the conductor, with a resistor connected in parallel. Preferably, the electrical conductor is connected to a ground potential at one point. This is done, by way of example, through the support, which is preferably constructed as a support surface. At another point, the electrical conductor is electrically connected to a capacitance. 
     In accordance with a further feature of the invention, in order to improve the electrical properties further, one end of the preferably strip-shaped electrical conductor is disposed on the support, and the other end of the electrical conductor is used as a coupling point for inputting or outputting an electrical signal. 
     In accordance with an added feature of the invention, the electrical conductor is situated essentially within a conductive support surface. Such a configuration has the advantage of reducing the influence of external interference fields to a large extent. 
     In accordance with an additional feature of the invention, a further reduction in the space requirement can be achieved if the oscillator circuit is formed by an integrated electronic circuit. 
     In accordance with yet another feature of the invention, the integrated electronic circuit contains at least one varactor diode. 
     A varactor diode is a surface-contact diode with a pn junction at which a depletion layer is formed that can be varied by using a control voltage in the reverse direction. The insulating depletion layer forms a capacitor with the conductive covering surfaces. The capacitor has a surface which remains constant and a plate spacing that can be changed by using the control voltage. A varactor diode is preferably distinguished by a large ratio between the largest and the smallest useful capacitance, a low series resistance and therefore a high quality. Due to the use of a varactor diode device, the integrated electronic circuit contains a voltage-controlled, variable capacitor. This controls the natural frequency of the resonator. 
     The varactor diode can be formed from various basic materials. Besides silicon, which is particularly easy to handle in technological terms, gallium arsenide is particularly suitable for high frequencies. With gallium arsenide, the mobility of the charge carriers is approximately four times greater than in silicon and the series resistance of the varactor diode is correspondingly lower. 
     In accordance with yet a further feature of the invention, there is provided an amplifier for exciting the electrical oscillation. The amplifier can be disposed at any desired point, but it is a particularly expedient feature that the amplifier is incorporated into the integrated electronic circuit. 
     In accordance with yet an added feature of the invention, the amplifier is incorporated together with the varactor diode. 
     In principle, the oscillator circuit, which is preferably formed by an integrated electronic circuit, may be mechanically connected to the support in any desired manner. However, in accordance with yet an additional feature of the invention, the integrated electronic circuit is connected to the support through the use of an adhesive layer. A connection using an adhesive layer has a number of advantages. Such a connection is very simple to produce. Furthermore, it is possible for the adhesive layer to insulate the integrated electronic circuit from a support and/or a resonator. The connection using an adhesive layer is particularly expedient if the electronic circuit is in the form of a chip. The chip then advantageously has no metalization on the back. 
     In accordance with again another feature of the invention, the integrated electronic circuit is connected to the preferably conductive support through the use of a connecting wire (bonding wire). 
     In accordance with a concomitant feature of the invention, there is provided a connecting wire connected to the coupling point of the exposed electrical conductor. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in an oscillator structure having at least one oscillator circuit and at least one resonator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
    
    
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 contains both a diagrammatic plan view of a housing having a support which contains an exposed electrical conductor, as well as a diagram of an electrical equivalent circuit; 
     FIG. 2 is a view similar to FIG. 1 with an oscillator formed by an integrated electronic circuit; and 
     FIGS. 3 and 4 are views similar to FIG. 1 respectively showing meander and spiral-shaped conductors. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawings in detail, there is seen an illustration which relates to an exemplary embodiment of an oscillator structure according to the invention in a commercially available IC housing, such as a housing having an SCT596 structure. 
     FIGS. 1 and 2 show how a support  20 , which is preferably a punched sheet-metal strip (lead frame), and further connections  60 ,  70 ,  80  and  90 , which are preferably made of metal, are situated in a housing  10 . The surface area of the support  20  is on the order of magnitude of 1 mm 2 . 
     The housing  10  is preferably made of a molded plastic based on epoxy resin having a dielectric constant in a range of from 3 to 5. 
     The metal part referred to as the support  20  and the connections  60 ,  70 ,  80  and  90 , which likewise have an areal construction, are preferably a lead frame for a semiconductor assembly from which the structures described herein are punched. The support  20  has cutouts  25  and  28  between which an electrical conductor  30  having a tongue-like construction is exposed. The electrical conductor  30  may also be referred to as a conductor strip in this case. The electrical conductor  30  preferably has a length on the order of magnitude of 1 mm. By way of example, the dimensions of the electrical conductor  30  are: 800 μm×250 μm. The electrical conductor  30  may also have a meander or spiral shape as is respectively shown in FIGS. 3 and 4. 
     One end of the electrical conductor  30  is in contact with the support  20 . An opposite end of the electrical conductor  30 , in a region of a coupling point  35 , has an apparatus for inputting or outputting an electrical signal. 
     The planar support  20  has a side region which contains contacts  40  and  50  used for connecting a ground potential. The contacts  40  and  50  are likewise in the plane of the main surface of the support  20 , but perpendicular to the electrical conductor  30 . The contacts  40  and  50  are constructed differently in order to obtain an identification which prevents rotation through 180°. However, both contacts  40 ,  50  are soldered to ground in the same way. 
     A resonant frequency of the electrical conductor  30  acting as a resonator results from a length of the electrical conductor  30  and a dielectric constant of the housing. The dielectric constant of the housing is in a range from 2 to 6, with 4 being a usual value. 
     The connections  60 ,  70 ,  80  and  90  enable a supply voltage and an oscillator control voltage, a so-called VCO tuning voltage, to be applied and they enable a signal output and connection options for external circuit elements to be created. It is expedient for a grounding capacitor to be connected, in order to block out interference influences. 
     FIG. 1 also contains an electrical equivalent circuit diagram, in which the exposed conductor represents an inductor, defined by the mechanical dimensions of the conductor, with a resistor connected in parallel. 
     FIG. 2 is used below to explain how the support structure illustrated and discussed above with the aid of FIG. 1 is completed by adding an integrated electrical circuit to produce an oscillator structure. 
     An integrated electronic circuit  105  is connected to the support  20  through the use of an insulating adhesive layer  100 . Selected regions (“bonding pads”)  110 ,  120 ,  130  and  140  of the integrated electronic circuit  105  are connected to the connections  60 ,  70 ,  80  and  90  through connecting wires  160 ,  170 ,  180  and  190 . This allows a supply voltage or an oscillator control voltage to be applied to the selected regions  110 ,  120 ,  130  and  140  of the integrated electronic circuit  105 . In addition, connection options for external circuit elements are created in this way. The integrated electronic circuit  105  may contain at least one varactor diode  106  which interacts with the resonator in an electrical resonant circuit. The integrated electronic circuit  105  may also contain at least one amplifier  107 . 
     A further connecting wire  200  is used to connect the integrated electronic circuit  105  directly to the contact  40  for the support plate  20  and therefore to the ground potential. 
     Another selected region  210  of the integrated electronic circuit  105  is connected through the use of a connecting wire  230  to the coupling point  35  disposed at the free end of the electrical conductor  30 . 
     The oscillator structure described above combines the advantages of integrability into a housing, preferably a plastic housing, with superb electrical properties, such as a tunable capacitance and as little influencing as possible by external interference fields. 
     This construction of the oscillator structure according to the invention is particularly advantageous. However, it is likewise possible to construct the oscillator structure in a different way, so that the oscillator structure is integrated, by way of example, directly on a printed circuit board or film, on a hybrid substrate or in a microsystem.