DE3709356A1 - Microwave oscillator - Google Patents

Abstract

A microwave oscillator in push-pull circuit with two active non-linear elements and at least one frequency-determining element, oscillations of the second harmonic being taken from the oscillator at a point of symmetry of the fundamental oscillation, supplies a very stable frequency and is of simple and rugged construction and can be easily and accurately calibrated due to the fact that at least one of the frequency-determining elements (9, 10, 32, 50) comprises a dielectric resonator (13, 14, 51) coupled to a microstrip line (11, 12). <IMAGE>

Description

The invention relates to a microwave Oscillator in push-pull circuit with two active, not linear elements and at least one frequency determ element, the oscillator at a symmetry point of the fundamental vibration Vibrations of the second harmonic niches are removed.

From DE-OS 31 36 348 a microwave oscillator is in Push-pull circuit with two transistors known in the at a point of symmetry of the fundamental vibration, the Schwin second harmonic. Such Oscillators, also known as harmonic oscillators, find in the radar and communications technology for the Generation and transmission of micro and millimeter waves use in civil and military fields. they be such. B. shown in DE-OS 31 36 348 before trains built with bipolar transistors, since these in Compared to other active elements a special one Allow extensive reduction of phase noise. Since bipolar transistors only in the X-band, i.e. H. until about 12 GHz, can be used for even higher frequencies zen, especially for the increasingly used Ku band, Harmonic oscillators are used that are out of the reason vibration also a second harmonic vibration, d. H. with twice the frequency of the fundamental, deliver.

Microwave oscillators for radar and news technology must have vibrations with very stable, d. H. from Temperature fluctuations and aging processes in the  used components deliver independent frequencies. They should also be simple and robust be easy to match. The one from DE-OS 31 36 348 Known microwave oscillator meets these requirements not to the desired extent.

The object of the invention is a microwave ozilla to create gate of the type mentioned at the beginning Provides vibration with very stable frequency, simple and is robustly built and can be easily and precisely adjusted.

The object is achieved in that at least one of the frequency determining elements of the mentioned microwave oscillator one to one Microstrip coupled dielectric resonator includes.

Compared to the coils described in DE-OS 31 36 348 and capacities is a frequency-determining element that as a basic component a microstrip line contains, much simpler, easier and more precise adjustable, as well as more robust against mechanical stress chung, such as B. shocks and the like, and against aging of the materials used. These Dielectric resonators also have advantages preferably from a cylindrical body made of ceramic Material. You will be in close proximity to the Microstrip line attached to their substrate. Your Coupling to the line can be done by simply moving it the respective requirements of the microwave oscillator can be adjusted as desired. The dielectric resonators also have small dimensions and very stable Resonance frequencies due to low temperature coefficient and high grades, on. This will make the microwave oscillators according to the invention small, light  and inexpensive, so that they are especially for the Satellite reception in the field of consumer electronics are usable.

For the microwave oscillator according to the invention as active elements, for example high-frequency diodes Find use; the active elements are preferred however designed as a three-pole. As such, esp special bipolar transistors due to their good signal transmission properties at high frequencies, especially due to the low phase noise also field effect transistors used.

The frequency-determining elements are according to one advantage stick embodiment of the invention on the frequency of Fundamentals tuned and thus place those in the Oszilla Tor with the greatest amplitude vibration in their frequency. The through the nonlinearity of the second harmonic formed by active elements is thereby also stabilized in frequency. The invention According to the microwave oscillator can also on the Second harmonic frequency tuned frequency determining element, so that the frequency of the Fundamental vibration through the predetermined frequency of the second Harmonics is determined.

Further advantageous embodiments of the invention are in the other subclaims.

Some embodiments of the invention are in the Drawing shown and are described in more detail below explained. Show it  

Fig. 1 is a microwave oscillator in push-pull circuit with two frequency-determining elements according to the invention,

Fig. 2 shows a modification of the microwave oscillator with a modified frequency-determining element,

Fig. 3 shows an embodiment for a band rejection filter for use in the oscillators of Fig. 1 and 2,

Fig. 4 shows a further modification of the oscillator of Fig. 1 modified with a notch filter,

Fig. 5 shows another embodiment of an inventive microwave oscillator with a further modification of the frequency-determining elements and

Fig. 6 examples of active elements used in the microwave oscillators according to FIGS. 1 to 5.

Fig. 1 shows as a first embodiment of a microwave oscillator according to the invention, a first basic type with two frequency-determining elements, each containing a dielectric resonator. Two active elements 1 and 2 , each with three poles 3 , 4 , 5 and 6 , 7 , 8, are arranged therein. The first poles 3 and 6 are connected to a first and second frequency-determining element 8 and 10 , respectively. These each consist of a microstrip line 11 or 12 , a dielectric resonator 13 or 14 coupled thereto, a bandstop filter 15 or 16 inserted into the microstrip line, and a line 11 or 12 to ground at the end of the microstrip facing away from the active element switched terminator was 17 or 18 . The second poles 4 and 7 of the active elements 1 and 2 are connected via a connection impedance 19 , 20 to the input 21 of a matching network 22 , the output 23 of which is connected to a load resistor 24 , to which the vibrations of the second harmonics are fed will. Otherwise, the third poles 5 and 8 of the active elements 1 and 2 are connected to ground, and the first and second poles 3 , 4 and 6 , 7 of the active elements 1 and 2 are connected to one another by a wiring impedance 25 and 26, respectively.

The active elements 1 , 2 of the microwave oscillator according to FIG. 1 are connected in series via their second and third poles 4 , 5 and 7 , 8 and the connection impedances 19 and 20 and in this way form a push-pull oscillator. The dielectric resonators 13 and 14 are tuned to the frequency of the fundamental oscillation. The oscillator of FIG. 1 is also symmetrical structure, ie the active elements 1, 2, the frequency-determining elements 9, 10, the connection impedances 19, 20 and the Beschaltungsimpedanzen 25, 26 are equal to each other. For reasons of symmetry, a current I 1 then flows at the frequency of the fundamental oscillation through the connection impedances 19 and 20 , but not into the input 21 of the matching network 22 , the potential for the fundamental oscillation of which is constantly at ground. A signal of the frequency of the fundamental oscillation does not therefore appear at the load resistor 24 .

Due to the nonlinearities of the active elements, vibrations of higher harmonics of the fundamental vibration, in particular of the second harmonic, are also excited in the microwave oscillator according to FIG. 1. Their amplitudes are set to the highest possible values by appropriate dimensioning of the frequency-determining elements 9 , 10 and the connection impedances 19 , 20 and the wiring impedances 25 , 26 . This is achieved especially through low-loss elements. When using bipolar transistors as active elements 1 , 2 , the connection impedances 19 , 20 are preferably low-loss inductances and the wiring impedances 25 , 26 are designed as low-loss capacitances. They represent a low load for the basic vibration and thus enable a high modulation of the active elements 1 , 2 .

While for the fundamental and all higher, odd harmonics, the input 21 of the matching network 22 is at ground, the second and also the higher even harmonics of the fundamental at the second poles 4 and 7 of the active elements 1 and 2 currents flowing in unison are excited. These are designated I 2 for the second harmonic and are entered in FIG. 1. The amplitudes of the currents of the higher even harmonics are generally small compared to the amplitude of the currents I 2 . Then essentially twice the current I 2 flows out via the input 21 of the matching network 22 . With respect to input 21 , the arrangement according to FIG. 1 thus represents an oscillator for the oscillation of the second harmonic. Since the fundamental oscillation is not effective at the input 21 due to the basic structure of the microwave oscillator, a filter can also be used here to suppress it to be dispensed with. The matching network 22 only serves to adapt the load resistor 24 , for example formed by the input resistance of a line coupling out the oscillation of the second harmonic, to the circuit effective at the second harmonic and its impedances. This ensures an optimal power arrangement.

In the identically executed frequency determining elements 9 and 10 in FIG. 1, the microstrip line 11 or 12 forms a coupling line for the dielectric resonator's 13 or 14 . Since this is matched to the frequency of the fundamental oscillation and thus does not influence the oscillations at other frequencies, ie also at the second harmonic, they can reach the terminating resistor 17 or 18 unhindered via the coupling line. Without additional measures, the terminating resistor 17 or 18 would then act as an additional load for the higher harmonics and cause a considerable reduction in the output power at the load resistor 24 .

In order to prevent this disadvantage, fenleitung 11 and 12 bandstop filters 15 and 16 are inserted into the microstrip lines, which are tuned to the second harmonic and the vibrations of this frequency from the dielectric resonator 13 and 14 and from the terminating resistor 17 and 18th keep away. The bandstop filters 15 , 16 are also preferably low-loss, so that they form an ohmic load neither in the fundamental nor in the second harmonic. The distance 1 'of the bandstop filter 15 or 16 from the active element 1 or 2 facing the end of the microstrip line 11 or 12 and the input resistance Z 15 or Z 16 of the bandstop filter 15 or 16 for the second harmonic are so coordinated that the input resistance Z 9 or Z 10 of the frequency-determining element 9 or 10 seen from the first pole 3 or 6 of the active element 1 or 2 assumes a value for the second harmonic that enables an optimal adaptation of the load resistor 24 and thus ensuring maximum decoupling of the vibrations of the second harmonic.

The dielectric resonator 13 and 14 is in a stand from 1 of the active element 1 or 2 facing the end of the microstrip line 11 or 12 popped to this. The microstrip line 11 or 12 has a characteristic impedance Z 0 . The terminating resistor 17 or 18 preferably has the same value. The length l is selected such that the impedance of the microstrip line 11 or 12 at the location of the resonator 13 or 14 is transformed to a value of the input resistance Z 9 or Z 10 which corresponds to the amount required to oscillate the oscillator. and phase relationship is fulfilled, ie that the input resistance Z 9 or Z 10 has the resonance characteristic caused by the resonator to stabilize the frequencies of the vibrations emitted by the oscillator to the desired extent.

Basically, a terminating resistor 17 or 18 is not required in the frequency-determining elements 8 or 10 . The microstrip line 11 or 12 is then operated in idle mode at the end facing away from the active element 1 or 2 . In principle, a short circuit is also possible there if the cable length is selected accordingly. A defined terminating resistor 17 or 18 , however, offers the advantage of a precisely determinable vibration behavior of the oscillator and thus a clear tuning characteristic.

The dielectric resonator 13 or 14 can be used both in the function of a reaction and a reflection resonator. Basically, the resonator 13 or 14 forms a magnetic dipole, which couples with its external magnetic field to the microstrip line 11 or 12 and thereby acts as a parallel resonant circuit in series with the line at the coupling point. A corresponding coupling can be adjusted in a simple manner by adjusting the position of the dielectric resonator 13 or 14 relative to the microstrip line 11 or 12 . In the mode of operation as a reaction resonator, a significant proportion of the energy of the basic vibration reaches the terminating resistor 17 or 18 and can be decoupled there, so that the arrangement according to FIG. 1 can also supply the basic vibration. The terminating resistor 17 or 18 then acts on the one hand as a damping resistor for the dielectric resonator 13 or 14 and on the other hand as a load resistor for the basic vibration. It can be formed, for example, by the input resistance of a line for dissipating the energy of the basic vibration. The load on the oscillator due to the emission of energy during the fundamental oscillation should not be too strong, which is achieved by appropriate selection of the distance between the resonator 13 and 14 and the microstrip line 11 and 12 , respectively. If, on the other hand, a decoupling of the fundamental oscillation is not desired, the dielectric resonator 13 or 14 is converted into the function of a reflection resonator by changing the strength of its coupling to the micro strip line 11 or 12 . The energy of the fundamental vibration is reflected as much as possible by the dielectric resonator 13 or 14 in the direction of the active element 1 or 2 . The terminating resistor 17 or 18 then serves only as a damping resistor for setting the tuning characteristic.

FIG. 2 shows a modification of the microwave oscillator according to FIG. 1. Elements which correspond to parts from FIG. 1 are provided with identical reference numerals. The arrangement according to FIG. 2 corresponds essentially to that of FIG. 1 for the case of a reflection resonator. In addition, a separate decoupling line is coupled to the dielectric resonator 14 , which is terminated at its end facing away from the resonator 14 by a fundamental load resistor 31 . This can again be formed by the input resistance of a line for dissipating the energy of the basic resonance taken from the dielectric resonator 14 via the decoupling line 30 , and the terminating resistor 18 then serves only as a damping resistor for the resonator 14 . This is operated in the resulting frequency-determining element 32 , which takes the place of the frequency-determining element 10 , operated as a transmission resonator. Here, too, the load on the oscillator due to the release of energy during the fundamental vibration should not be too great. This can be achieved in a simple manner in that the distance between the dielectric resonator's 14 and the coupling line 30 is selected accordingly. Any weak coupling can be set by increasing this distance.

Basically, it is possible to operate frequency-determining elements of different types next to each other in a microwave oscillator. B. connect the frequency-determining element 9 to the active element 1 and the frequency-determining element 32 to the active element 2 . However, the same frequency-determining elements are preferably to be used in order to obtain an exactly symmetrical arrangement with respect to higher harmonics.

The point of view of symmetry also applies to the decoupling of the fundamental oscillation, which in principle can also take place on only one of the frequency-determining elements, but as a result of which the oscillator is loaded asymmetrically, which, depending on the amount of the decoupled energy of the fundamental oscillation, leads to an impermissibly high proportion of the fundamental oscillation and can lead to odd higher harmonics at the load resistor 24 . If only one output for the fundamental oscillation is really needed, it should be connected to one of the frequency-determining elements 9 , 10 and 32 , while the other frequency-determining element has an - internally arranged - terminating resistor 17 , 18 or basic oscillation load resistor 31 for receiving one contains the corresponding amount of energy of the fundamental vibration.

Various configurations are also possible for the bandstop filter 15 or 16 . Fig. 3 shows an embodiment with a stripline circuit. This consists of several strip conductors 40 , the length of which corresponds to approximately a quarter of the wavelength at the frequency of the second harmonic and which are arranged at a mutual distance of one quarter of the wavelength at right angles to the longitudinal axis of the microstrip line. In the example of FIG. 3, this is illustrated using the microstrip line 12 and the bandstop filter 16 . The ends of the strip line 40 facing the microstrip line 12 are arranged in an insulated manner, the ends facing away are connected to ground.

A particularly advantageous embodiment for a band blocking filter is shown in Fig. 4, which shows a modification of the microwave oscillator according to Fig. 1, another corresponding parts are again provided with identical reference characters. In this example, the frequency-determining element 10 has, as a band-stop filter 16, a dielectric resonator which is tuned to the frequency of the second harmonic and otherwise corresponds in structure to the dielectric resonators 13 , 14 . The bandstop filter 16 forming dielectric resonator is coupled in the manner of a reflection resonator to the microstrip line 12 at a distance 1 'from its end facing the active element 2 . Like the dielectric resonator 13 or 14 for the fundamental oscillation, the bandstop filter 16 now acts for the frequency of the second harmonic like an inserted in position 1 'in series in the microstrip line 12 parallel resonant circuit, thus the oscillations of the frequency to which it is tuned prevents further spreading on the microstrip line 12 .

A band-stop filter constructed with a dielectric resonator is considerably more space-saving than a comparable band-stop filter with strip conductors. An additional advantage is that the optimal position 1 'of the bandstop filter 16 on the microstrip line 12 for maximum performance of the second harmonic African in the load resistor 24 can be set exactly by simply moving the resonator 16 . Thus, manufacturing tolerances of the optimal input resistance Z 10 of the frequency-determining element 10 at the second harmonic at the end of the microstrip line 11 facing the active element 2 , resulting from the individual harmonic components of the microwave oscillator, can lead to a maximum output of the second harmonic at the load resistor 24 be balanced.

A band blocking filter 16 constructed with a dielectric resonator also blocks only the frequency of the second harmonic in a very narrow frequency band. In contrast, all higher harmonics are passed on unhindered to the terminating resistor 18 and absorbed there. This also suppresses undesired higher harmonics at the load resistor 24 .

If the microwave oscillator in all parts with the exception of the dielectric resonators 13 , 14 and the bandstop filter 15 , 16 is sufficiently broadband, ie suitable for processing vibrations within a large frequency range, it is possible to provide a standardized basic circuit for a microwave oscillator , which can be equipped with differently dimensioned resonators depending on the desired frequency. An embodiment of the bandstop filter with a dielectric resonator matched to the frequency of the second harmonic is also advantageous for this.

In addition, with lower requirements for the content of higher harmonics in the oscillation supplied to the load resistor 24, instead of a band-stop filter 15 or 16 , a low-pass filter, for example with strip conductors in the type described in FIG. 3, can also be provided by the active element 1 or 2 only the basic vibration to the dielectric resonator 13 or 14 passie ren. However, as with the bandstop filter with strip conductors according to FIG. 3, the higher harmonics to the active element 1 or 2 and thus to the load resistor 24 are returned.

Fig. 5 shows a second basic type of microwave oscillators according to the invention with only one frequency-determining member 50. In addition, the oscillator corresponds to Fig. 5 the example shown in Fig. 1, and matching components are again provided with identical reference numerals. In the oscillator according to Fig. 5, the microstrip lines 11, 12, the band rejection filter 15, 16 and the terminating resistors 17, 18 grouped together by a common dielectric resonator 51 to the frequency-determining member 50. This is connected in series between the first poles 3 and 6 of the active elements 1 and 2 , respectively. The common dielectric resonator 51 establishes the connection between the oscillator halves formed by the two active elements and acts both as a transmission resonator and as a feedback resonator. The terminating resistors 17 , 18 form damping resistors for the microstrip lines 11 , 12 and thus for the resonator 51 . For its position 1 along the microstrip lines 11 and 12 , the same applies to the previous figures. The bandstop filter 15 , 16 are constructed in the manner described.

If the coupling between the common dielectric resonator 51 and the microstrip lines 11 and 12 is set such that sufficient energy of the basic vibration reaches the terminating resistors 17 , 18 , an additional coupling of the basic vibration can also be provided in the microwave oscillator according to FIG. 5 will. The resonator 51 then also acts as a double-sided reaction resonator for each of the microstrip lines. Optionally, both termination resistors 17 , 18 or only one of them can be formed by a line for dissipating the energy of the fundamental wave.

Fig. 6 shows some examples of the formation of the active elements of the example of the active element 1. According to FIG. 6a) and b), a bipolar transistor is therefor used, with either the its base terminal to the first terminal 3 and its emitter terminal of the second pole 4 or with its emitter terminal of the first pole 3 and with its base terminal to the second terminal 4 forms , with the collector connection serving as third pole 5 in both cases. According to Fig. 6c) and d) a field effect transistor in Fig. 6a) and b) are used as the active element 1 correspondingly, the gate connection to the base connection, the drain connection to the emitter connection and the source connection to the collector connection. In a corresponding manner as the active element 1 , the active element 2 is constructed.

Claims (9)

1. microwave oscillator in push-pull circuit with two active, non-linear elements and at least one frequency-determining element, the oscillator at a point of symmetry of the fundamental oscillation, vibrations of the second harmonic are taken, characterized in that at least one of the frequency-determining elements ( 9 , 10 , 32 , 50 ) to a microstrip line ( 11 , 12 ) coupled dielectric resonator ( 13 , 14 , 51 ). 2. Microwave oscillator according to claim 1, characterized in that the active elements ( 1 , 2 ) are designed as three poles. 3. Microwave oscillator according to claim 1 or 2, characterized in that the frequency-determining elements ( 9 , 10 , 32 , 50 ) are matched to the frequency of the basic oscillation. 4. Microwave oscillator according to claim 2 or 3, characterized in that each active element ( 1 , 2 ) on a first pole ( 3 , or 6 ) with a frequency-determining element ( 9 or 10 , 32 ; 50 ) and is connected at a second pole ( 4 or 7 ) to a common load ( 24 ) for the vibrations of the second harmonic. 5. Microwave oscillator according to one or more of the preceding claims, characterized in that in the micro strip line device ( 11 or 12 ) of each frequency-determining element ( 9 , 10 , 32 , 50 ) between the active element ( 1 or 2 ) and the dielectric resonator ( 13 or 14 ) a tuned to the second harmonic band stop filter ( 15 or 16 ) is inserted. 6. A microwave oscillator according to claim 5, characterized in that the bandstop filter ( 15 or 16 ) is formed with a dielectric resonator. 7. Microwave oscillator according to one or more of the preceding claims, characterized in that at the end of the microstrip line ( 11 or 12 ) facing away from the active element ( 1 or 2 ) at least one frequency-determining element ( 9 or 10 , 32 , 52 ) the fundamental vibration can be removed. 8. A microwave oscillator according to one or more of the preceding claims, characterized in that at the end of the microstrip line facing away from the active element ( 1 or 2 ) ( 11 or 12 ) at least one frequency-determining element ( 9 or 10 , 32nd , 50 ) a terminating resistor ( 17 or 18 ) is connected to ground. 9. A microwave oscillator according to one or more of the preceding claims, characterized in that with at least one dielectric resonator ( 13 or 14 ), a further microstrip fenleitung ( 30 ) is coupled to derive the fundamental.