DE2441194B2 - TRANSISTOR OSCILLATOR - Google Patents

Description

The invention relates to a transistor oscillator for the microwave range in the CLAPP circuit, which is a capacitive three-point circuit deals with a capacitance arranged in series with the circular inductance (cf. FIG. 1).

Of the oscillator circuits commonly used in micro wave technology, the CLAPP oscillator offers the best options for broadband frequency tuning, since the circuit inductance Ls can be compensated for by the reactance of the capacitance Cs. The highest oscillation frequency results from the value of the collector base capacitance Ccb and the smallest circuit inductance. The feedback network consists of the capacitive voltage divider between collector and emitter as well as emitter and base. At higher frequencies, the parasitic capacitances Cce and C ^ e can advantageously be used as a capacitive voltage divider for the feedback network.

The invention is based on the object for such a broadband tunable transistor oscillator to specify a solution for a simple and mechanically stable structure that with little Components and should be done with the least possible test field effort.

This object is achieved in a transistor oscillator of the type mentioned at the beginning according to the invention through the construction in stripline technology and through a series-connected to the collector base capacitance, additional small capacitance between the base and ground and through an HF throttling λ / 4-long pieces of line, the ends of which have block capacitors are short-circuited.

In a further development of the invention, the additional capacitance consists of a line that is open at the end, whose electrical length is less than λ / 4, or is controlled by a trimmer capacitor or varactor elements educated.

From US-PS 35 13 411 it is known per se in a transistor oscillator to the collector base capacitance to connect a small capacitance in series between Bas.s and ground. Through the Series connection of such an additional capacity reduces the overall effective capacity

Furthermore, from FR-PS 12 14 582 a tunable transistor amplifier with a resonance circuit in the collector branch is known, in which a series resistor is connected between the collector and the resonance circuit in order to minimize the influence of the collector base capacitance on the resonance frequency of the resonance circuit. An inductance is connected in parallel to this series resistance The circuitry means and the circuit structure are here different from the embodiment according to the invention, which is also particularly advantageous. Because of the additional capacitance between base and ground in the transistor oscillator according to the invention, through which, on the one hand, high oscillation frequencies are achieved and, on the other hand, by changing the bandwidth, which can be varied with the circular capacitance, there is also no need for a high-frequency galvanic grounding of the base, in which in general parasitic inductances occur. An oscillator circuit of simple construction with few components is thus obtained, as a result of which the circuit is largely insensitive to parasitic influences and defined values for output power and tunable bandwidth can be achieved without subsequent adjustment work. In addition, the defined possibilities of intervention on the oscillation frequency result in the derivation of a large number of further oscillator variants from the oscillator circuit according to the invention.

Further details of the invention are explained in more detail below with reference to the exemplary embodiments shown in the drawing. In the drawing shows
F i g. 1 shows a known CLAPP oscillator, FIG. 2 shows a CLAPP oscillator modified according to the invention,

F i g. 3 shows the overall circuit diagram of the oscillator, FIG. 4 the microwave part of the oscillator, F i g. 5 the equivalent sound pattern of the microwave part and FIG. 6 to 12 different variants of the invention Oscillator.

The CLAPP oscillator shown in Fig. 1 is, like the Colpitts oscillator, a capacitive three-point circuit, the divider circuit of which is formed by the collector-emitter capacitance Cce and the emitter-base _{capacitance C fB} . The oscillator is connected in series with the oscillating inductance Ls and a capacitance Cs .

Based on this known CLAPP oscillator, the oscillator according to the invention according to FIG. 2 in series with the collector base capacitance, a small capacitance Cbm is also connected in series, which is arranged between the base of the transistor and ground. By connecting the collector base capacitance Ccb in series with the further small capacitance Cum between base and ground, the effective circular capacitance is reduced and this causes an increase in the oscillation frequency. Furthermore, the insertion of the series capacitance Cbm eliminates the need for a high-frequency, galvanic grounding of the base, in which parasitic inductances generally occur.

In Fig.3 is the overall circuit diagram of the oscillator shown. The microwave part of the circuit is made

from the line pieces I _u h and h. the varactor diodes V ₁ , V ₂ for the electronic tuning of the frequency and the microwave transistor Tr. The line section A forms the additional capacitance Cbm; it is connected at its one end to the base of the microwave transistor Tr ; the two series-connected, oppositely polarized varactor diodes Vi, V _{2 are} connected to its collector, to which the line section k is connected in the longitudinal branch and the conductive _{element / 3} forming the oscillating inductance L _{s is} connected in the transverse branch. The direct current part comprises a reverse polarity protection diode D, the emitter resistor Re, the base voltage divider A ₁ , R ₂ , the varactor resistor Rv and the blocking capacitors Ci, C ₂ , C * All direct currents and the varactor voltage are supplied via λ / 4-long high-resistance line sections / 4 , y ₅ , 4 fed. The line section J ₇ is used for direct current return for the collector of the microwave transistor Tr and the varactor diode Vl. It is a short-circuited line with a length of λ / 4.

This electrical structure results in a simple mechanical structure that allows the Circuit with a minimum of components in stripline technology on a plastic or Realize ceramic substrate and use different transistor types.

4 shows a circuit diagram in which only the microwave part of the oscillator is shown. For the sake of clarity, the parasitic influences of the λ / 4-long direct current supply lines on the oscillation frequency due to short-circuit-no-load transformation are neglected in this electrical equivalent circuit. This circuit diagram essentially only contains the frequency-determining elements that are based on the equivalent circuit diagram according to FIG. 5 will be described in more detail. The elements of the transistor Tr are outlined in dashed lines. Ccb denotes the junction capacitance between collector and base, Cbm denotes the additional capacitance between base and ground (for / 1 less than λ / 4), Ls denotes the oscillating inductance (short-circuited line section / 3 less than λ / 4), with Cn, Cv 2 the varactor capacitances which form the oscillating capacitance Cs according to FIGS. 1 and 2, with Tr the microwave transistor, with Cce, Ceb the feedback voltage divider and with Cem an undesired stray capacitance between emitter and ground. Rn is d; e load Ru transformed with high impedance by the line section I ₂ For the dimensioning of the resonant circuit, it should be noted that the circuit part shown to the left of the vertical dashed dividing line in the figure remains capacitive in the desired frequency range, the part along the dividing line remains inductive.

Of the frequency-determining elements of the circuit, the capacitive reactance of the junction capacitance Ccb and / ι formed from the capacitive properties of the open-ended line additional capacitance Cbm is composed. Cßwist can be adjusted by changing the length of the line section h and can be replaced by other capacitive elements such as trimmers or varactor diodes. The inductive reactance is formed from the sum of the positive reactance of the oscillating inductance Ls and the negative reactance of the varactor elements Cn, Cw. By changing the series-connected capacitances Cm and Cw, an inductive reactance can be set over a large frequency band, the amount of which is the same as the capacitive reactance of the circuit. The resonant circuit inductance Ls consists of the line piece h and a short-circuit connection, for example a screw, which leads to ground. Detuning the resonant circuit by compensating for the inductive reactance enables broadband tuning of the oscillation frequency. The capacitances Cm and Cvi can be replaced by other capacitive elements.

A number of other microwave transmitters can be derived from the equivalent circuit diagram of the oscillator Derive properties, the different variants being shown in FIGS. 6 to 12 and in will be described below.

F i g. 6 shows a fixed frequency oscillator with one-time frequency adjustment. In this oscillator, the capacitances Cm and Cn are replaced by a short circuit. The load is coupled by tapping the oscillating inductance Ls- The balancing process consists in shortening the line section h , whereby the oscillation frequency is shifted to a higher frequency.

The F i g. 7, 8 and 9 each show a fixed-frequency oscillator with frequency tuning by means of trimmer capacitors. F i g. 7 shows an oscillator in which the additional capacitance Cbm is a trimmer element and the varactor capacitances Cm and Cw are bridged. Since the tuning screw of the cylinder capacitor is connected to ground, the oscillator can be tuned when the housing is closed. When the oscillator of Figure 8, the Zusatzicapazität Cbm from the line piece 1 \ is formed, however, the series circuit of the Varaktorkapazitäten Cn and Cw is here replaced by the trimmer capacitor Cs At the maximum set trimmer capacitance Cs of the line piece / 1 may have a lower resonant frequency can be determined by cutting. From this frequency on, the trimmer enables broadband tuning. In the oscillator according to FIG. 9, the additional capacitance Cbm and the oscillating capacitance Cs are formed by trimmer elements. This arrangement enables a very broad-band mechanical tuning, since both the circuit capacitance and the circuit inductance are changed.

Figures 10, 11 and 12 show electronically tunable oscillators. In this case, when electronically tunable oscillator having trimmable initial frequency 10The electronic tuning is done according to Figure by compensating the inductive reactance-resistance of the Schwinginduktivität Ls with one or more series-connected Varaktorelementen Vi, V ₂ -. The lower oscillation frequency and initial frequency can be obtained by shortening the line piece / 1 must be matched. FIG. 11 shows an electronically tunable oscillator with a tunable initial frequency, in which, in contrast to the oscillator according to FIG. 10, the additional capacitance Cbm is formed by a trimmer capacitor instead of the line section / 1. 12 shows an electronically tunable oscillator with an electronically tunable initial frequency, in which the oscillating capacitors and the additional capacitances consist of varactor elements Vi, V ₂ and V3, V4 . Here, the same bias voltage can be used when tuning the two pairs of varactor elements, whereby a very broad-band electronic tuning is achieved because of the simultaneous change in the circuit inductance and circuit capacitance, or one uses for the

the varactor elements forming the additional capacitance have their own bias voltage, which results in the lower oscillation frequency (Initial frequency) can be tuned electronically. The second oscillator variant thus has two independent frequency modulation inputs.

For this purpose 3 sheets of drawings

Claims (4)

Patent claims: 1. Transistor oscillator for the microwave range in Clapp circuit, characterized by the construction in stripline technology and by an additional small capacitance {Cbm) connected in series to the collector base capacitance and lying between base and ground and by an H F throttling through λ / 4-long cable pieces (A, / 5, h), ^{| 0} whose ends are short-circuited via block capacitors (Ci, Ci, Q). 2. Transistor oscillator according to claim 1, characterized in that the additional capacitance {Cbm) consists of a line open at the end (/), the electrical length of which is less than λ / 4 3. Transistor oscillator according to claim 1, characterized in that the additional capacitance {Cbm) consists of a trimmer capacitor. 4. Transistor oscillator according to claim 1, characterized in that the additional capacitance {Cbm) of varactor elements (Vi, Vi) is formed.