RU1781812C - Generator - Google Patents

Abstract

Use The invention relates to microwave radio engineering and can be used as a tunable generator in apparatus for various purposes. SUMMARY OF THE INVENTION: a generator comprising a Noi volumetric cylindrical resonator with a movable first end wall, into which an active semiconductor element and a first varactor are connected with the first coupling element, the second coupling element, the second varactor and the first and second are introduced communication loops. In this case, the first and second varactors are mounted on the second end wall, the second communication element is mounted on the side wall of the resonator, and the first and second communication loops are used to couple the first and second varactors to the resonator, respectively. 5 silt

Description

The invention relates to the field of microwave radio engineering and can be used in equipment for various purposes, including highly stable microwave generators with a PLL circuit 1 for transmitting digital information via radio-relay and satellite links.

A tunable generator is known that contains generator and varactor diodes placed as a single unit inside the resonator. The frequency of the generator is mechanically tuned using a movable metal sleeve worn on a rod to supply voltage to the varactor diode

The disadvantages of the known resonators - low temperature stability of the frequency and a significant level of phase noise - are due to the low quality factor of the used resonators, which is further reduced due to the strong coupling with the attractor

In modern communication equipment where it is necessary to ensure high frequency stability and low phase noise, microwave generators stabilized by high-quality cylindrical cavity resonators with operating Noi oscillations are used. The intrinsic Q factor of such resonators in the 3 cm range is about 15000-20000.

A microwave tunable generator is known, comprising a generator diode inside a rectangular waveguide a and a Noi cylindrical cavity resonator coupled to the waveguide by two holes in the end wall. In addition, the generator includes a varactor diode mounted in a separate waveguide volume, connected to the resonator with an opening in the qi | LjBKl-L

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Lindric wall. When the bias voltage changes on the varactor, a slight electrical tuning of the generator frequency occurs, which is used to create frequency modulation in the PPC service communication channel, which includes this microwave generator.

This device is the closest to the claimed technical essence and is selected as a prototype.

The disadvantage of the prototype is the narrow band, which is manifested in the fact that when the main cylindrical resonator is mechanically modified, the waveguide volume in which the varactor is installed must be carefully reconfigured. Reconfiguration is complicated by the fact that it is necessary to take measures to suppress spurious oscillations inside the cylindrical resonator and especially of them vibration Es, which has the same critical frequency with Noi's operating oscillation. Thus, the prototype is electrically tuned only in the vicinity of one frequency to which it is previously tuned. In other words, electrical tuning is not provided over a wide range of mechanical frequency tuning.

An object of the invention is to provide electrical frequency tuning over a wide range of mechanical tuning while balancing the output power of the generator.

This goal is achieved by the fact that in the tunable microwave generator containing a volumetric cylindrical resonator with a working oscillation Noi with a movable and fixed end walls, connected through a communication hole with an active semiconductor device, and the first varactor, according to the invention, a second varactor and two identical loops are introduced connection, while both varactors are placed on the fixed end wall of the resonator T and the coupling is made in the cylindrical wall of the resonator at a distance X0 from the fixed end wall Ki is determined from the ratio emom:

sin

(lHo)

where And, and 2 - the length of the resonator at the lower and upper frequencies of the range of mechanical tuning;

QI and Q2 are the externally loaded Q-factor of the resonator at the lower and upper frequencies, determined when the communication hole is placed in the middle

5 between the end walls of the resonator at one or another frequency, the communication loops are located at a distance of 0.48 R (R is the radius of the resonator) from the longitudinal axial line of the resonator, axisymmetrically and at the same distance from the communication hole, and oriented in the circular direction lines, and the beginning of each loop is electrically connected to the fixed end wall, and the corresponding varactor is connected to the end of each loop.

Comparative analysis with the prototype shows that the claimed technical solution contains new elements and

0 interconnection and, thus, meets the criterion of novelty.

When studying other technical solutions known in the art, the features that distinguish the claimed solution from the prototype are not detected, which indicates that the claimed solution meets the criterion of significant differences

FIG. 1 shows a tunable

0 microwave generator, cut along the diametrical plane of the resonator; in FIG. 2 is a sectional view taken along section AA, a view of the stationary end wall of the resonator with two communication loops; in FIG. 3 - fixed end wall

5 resonators (isometrics) at a magnification scale; in FIG. 4 - a separate communication loop with a varactor inside the resonator, (option 1); in FIG. 5 is a separate loop of communication with a varactor on a microstrip board outside the resonator (option 2).

The tunable microwave generator contains a cylindrical volume resonator 1 with a fixed end wall 2 and a movable end wall (plunger)

5 3. An active semiconductor device 4, for example, a Gunn diode, is installed in a waveguide 5 connected to a resonator 1 by a communication hole 6. On a fixed end wall 2 there are placed varactors 7 and 8 connected to communication loops 9 and 10, respectively The beginning of each loop is connected to the surface of the end wall 2 through capacitors 11 and 12. A bias voltage is applied to the varactor 7 through a wire 13.

5 The device operates as follows.

When the plunger 3 moves, the volume of the resonator 1 changes and a mechanical tuning of the generation frequency occurs. The frequency is electrically tuned by means of two waverkers 7 and 8, connected to the resonator 1 by loops 9 and 10. The arrangement of these loops is chosen so that two functions are performed:

1. Connection of varactors 7, 8 with a working oscillation of the Noah resonator in the magnetic field.

2. The separation of the frequencies of the working Noah and the parasitic oscillations,

The first function is provided by the orientation of the loops in the resonator in the direction of the circular line, while the loops interact with the magnetic field of the Noah oscillation.

The second requires clarification. The parasitic oscillation of Es occurs in the resonator mainly due to the inhomogeneity of the communication hole 6. The electric field in the opening of the hole b weakly excites the oscillation Es, whose field pattern has two antinodes of the electric field E in azimuth (4). These antinodes are located near the end walls of the resonator axisymmetrically at a distance of 0.48 R from the axis (R is the radius of the cylindrical resonator) at the same distance from the communication hole 6, which is why two communication loops 9, 10 were used in the device located in places of these antinodes. With this arrangement, the loops give a shift in the resonance frequencies of the Noah and Esch oscillations, opposite in sign:

the Noi vibration frequency shifts upward (see a similar problem in (5);

-frequency of oscillation Es is shifted downward, since the conductive loops are

at the antinodes of the electric field of this oscillation. A significant frequency spacing reduces the coupling coefficient between the Noah and Esch oscillations to almost zero and, thus, eliminates the effect of the spurious oscillation Es on the operation of the generator. However, this is not sufficient to provide stable electrical frequency tuning over a wide range of mechanical tuning. The instability is associated with a change in the coupling of the resonator 1 with the active device 4 during the movement of the plunger 3 against the background of a decrease in the intrinsic quality factor of the resonator due to varactors.

The operation of the generator and the constancy of the output power depends on the QBH / QO coupling parameter, which characterizes the real part of the resonator conductivity brought to the active device. Here: QBH - externally loaded Q-factor of the resonator under load through the communication hole b,

Qo is the intrinsic Q factor of the resonator taking into account the decreasing effect of the varactors.

The smaller the value of Aries / Oo. the more reliable the generator works.

A separate Noi cylindrical resonator in the 11 GHz band has its own Q factor of about 15000, and a modern varactor (for example, AA 623 A-6) does not exceed 270. With relatively weak coupling, the varactor reduces the resulting intrinsic Q factor to a lesser extent, but still nprtriluioce electrical tuning of 10 MHz (to overlap with the margin the temperature drift of the frequency while stabilizing it by the PLL loop), the varactor reduces the resulting intrinsic Q-factor of the resonator Q0 by about half.

Against this background, a change in the external loaded Q-factor of the QBH resonator during mechanical frequency tuning is adversely affected. The formula for calculating 0Bv is given in 6. Due to the strong frequency dependence of the passage of electromagnetic energy through the hole (coefficient M in formula (2)), the value of QBH. varies from 1500 to 800 in the range of mechanical frequency tuning from 10.7 to 11.7 GHz, if, as usual, the communication hole 6 is located in the middle between the end walls of the resonator. As a result, in the frequency range, the QBH / QO coupling parameter varies from 0.1 to 0.2, as a result of which the output power decreases at the low-frequency edge of the range until the generation fails.

To ensure stability of the electrical frequency tuning and constant output power of the generator, the communication hole 6 is offset & side of the plunger 3 so that the dependence of the movement of the plunger

I

sin 2 (Ј)

offset the change

QBH values. Based on the formula (2), the location X0 of the communication hole is determined from the relationship:

. / LH0h

sm -}

sin ()

2

where h and z are the length of the resonator at the lower and upper frequencies of the mechanical tuning range;

Qi and Q2 - externally loaded Q-factor of the resonator at the lower and upper frequencies, defined under the condition

placing the communication hole 6 in the middle between the end walls of the resonator at one and the other frequency.

Moreover, at the edges of the mechanical frequency tuning range, the value of the external loaded Q-factor QBH is the same, and in the middle of the range it differs slightly from it. Consequently, over the entire range of mechanical frequency tuning, the magnitude of the RH / Oo coupling parameter is unchanged, which provides stable electrical frequency tuning and constant output power of the generator.

Various design options for connecting a single loop to a varactor are shown in FIG. 4 and 5.

In one design shown in FIG. 4, the beginning of the communication loop 9 is electrically connected to the stationary end wall 2 of the resonator through a flat capacitor 11. The end of the loop 9 is connected to a varactor 7 mounted on the end wall 2 inside the resonator. The bias voltage is supplied to the varactor 7 through the wire 13. The capacitors 11 and 14 and the length of the thin wire 15 between them serve as a low-pass filter to prevent the leakage of microwave energy into the bias circuit.

In another embodiment shown in FIG. 5, the start of the communication loop 9 is directly electrically connected to the stationary end wall 2 of the resonator. The end of the loop 9 is connected through a segment of coaxial 16 to a varactor 7 mounted on the end wall 2 on the intermediate microstrip plate 17. The microstrip loop 18 serves to electrically short the output of the varactor to the end wall 2. A bias voltage is applied to the same output of the varactor.

In conclusion, it should be noted that the main provisions of the invention are valid not only for a waveguide generator with a Gunn diode (Fig. 1), but also for other types of generators with a cylindrical resonator.For example, not only waveguide 5 with diode 4 can adjoin the communication hole 6 ( Fig. 1), but also a microstrip board with a microwave transistor. In this case, the resonator is connected to the microstrip line through the transition of the slit-microstrip line.

Thus, in comparison with the prototype, the claimed technical solution provides electrical frequency tuning in a wide range of mechanical tuning while equalizing the generator output power.

FORMULA AND ZOBRETIN

A generator containing a volumetric cylindrical resonator with an operating Noah oscillation and a radius R, the first end wall of which is made movable, and

the second is a fixed, active semiconductor element coupled through a first coupling element to a volumetric cylindrical resonator, and a first varactor, characterized in that, with

In order to provide electrical frequency tuning in a wide range of mechanical tuning during equalization of the generator output power, a second varactor, a second communication element, are introduced.

the first and second communication loops, with the first and second varactors mounted on the second end wall, the second communication element is placed on the side wall of the volumetric cylindrical resonator at a distance

X0 from the second end wall, selected from the ratio

sin (gfi sin ()

Q

Q2

where 11 and 2 are the lengths of the volumetric cylindrical resonator at the lower and upper frequencies

mechanical adjustment range,

QI and Q2 are the external loaded Q factors of the volumetric cylindrical resonator at the lower and upper frequencies, and the first and second coupling loops are located at

0.48 R from the longitudinal axis of the volumetric cylindrical resonator axisymmetrically relative to the second coupling element and connected at one end to the second end wall, and the other to

first and second varactors, respectively.

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