RU156871U1 - INTERFERENCE SWITCH OF RESONANT MICROWAVE COMPRESSOR - Google Patents

Abstract

An interference switch of a resonant microwave compressor containing a T-shaped H-tee with input and output straight shoulders, a half-wave short-circuited side shoulder and a microwave switch, characterized in that the short circuit of the side shoulder of the main T-shaped H-tee is made of two additional T- shaped H-tees, the input straight half-wave shoulder of the first additional H-tee is combined with the lateral half-wave shoulder of the main H-tee, the input straight half-wave shoulder of the second additional H-tee ynika combined with a half-wave of the first additional lateral shoulder-H tee output direct shoulders additional quarter-H-tees are short-circuited, and the microwave switch is a half-wavelength shorted sidearm second additional N-tee at a distance from the short-equal to a quarter wavelength in the waveguide.

Description

The utility model relates to the field of radio engineering and can be used in resonant microwave compressors as an energy output device for generating powerful microwave pulses of nanosecond duration.

Known interference switches of a resonant microwave compressor containing a T-shaped H-tee from a standard single-mode rectangular waveguide with a short-circuited half-wave straight or side arm and a microwave switch located in this arm at a distance of λ / 4 from the short-circuit [R. Alvarets, D. Birke, Bern D., Lauer E., Scalapino D., Microwave energy compression in time for use in charged particle accelerators. - Nuclear technology abroad, 1982, No. 11, S.36-39; D.L. Birx, D.J. Scalapino., A cryogenic microwave switch. - IEEE Transactions on magnetic, 1979, V. MAG-15, No. 1, P. 33-35], where λ is the wavelength in the waveguide. Due to the limited dielectric strength of the insulating medium and the small cross-sectional area of the waveguide, such a switch has a relatively low operating power. For example, in the 10 cm wavelength range, this power does not exceed 200 MW.

Similar switches based on a T-shaped H-tee from a circular waveguide are also known, along which in addition to the working Ni wave, an E ₀₁ wave can propagate, which practically does not affect the switch’s performance [RU No. 2328062, publ. 06/27/2008, Bull. No. 18; RU No. 2387055, publ. 04/20/2010, Bull. No. 11]. The use of such a waveguide makes it possible to increase the cross-sectional area by more than 1.5 times in comparison with a round single-mode waveguide and by more than 3 times in comparison with a standard rectangular waveguide. Almost the same number of times the operating power of the switch and compressor can be increased. However, for the same reasons that are noted for switches from a single-mode rectangular waveguide, the power of such devices is also limited. In the 10 cm wavelength range, such a device with isolation with a mixture of gaseous nitrogen and SF6 gas under an overpressure of 4-8 atm allows microwave pulses of up to 400 MW to be produced when the device is manufactured from a waveguide with a diameter of 90 mm.

Theoretically, the power of microwave pulses generated by a compressor with a gas-discharge switch from a single-mode waveguide can be higher. However, the power is limited by the design elements of the microwave switch, which reduce the electric strength and the threshold of stable operation of a single-mode interference switch, which stimulates the search for alternative options.

So, for example, an interference switch of a resonant microwave compressor is proposed [Artemenko S.N., Avgustinovich V.A., Zhukov A.A., Interference switch of a resonant microwave compressor. Utility Model Patent No. 140527, Priority dated 10.29.2012, Registered 05/10/2014], made on the basis of a T-shaped H-tee from an oversized rectangular waveguide, the cross-sectional area of which is several times larger than the cross-sectional area of any single-mode waveguide. Accordingly, the operating power level of such a switch is several times higher than the power level of a switch made of a single-mode waveguide. At the same time, the switch from the oversized waveguide also has a limitation of the operating power associated with the finite electric strength of the insulating medium and the limitation of the cross-sectional area. The transverse dimensions of such a waveguide are limited due to the requirement that the travel time of the working wave along the switching arm of the switch is small compared with the travel time along the storage resonator. Otherwise, the switching time will be longer than the travel time of the wave along the resonator, which leads to a decrease in the efficiency of energy output from the resonator.

Known switches for a resonant microwave compressor based on a T-shaped H-tee from a rectangular waveguide, for example, single-wave [Alvarets R., Birke D., Bern D., Lauer E., Scalapino D., Compression of microwave energy over time for use in accelerators charged particles. - Nuclear technology abroad, 1982, No. 11, S. 36-39; D.L. Birx, D.J. Scalapino., A cryogenic microwave switch. - IEEE Transactions on magnetic, 1979, V. MAG-15, No. 1, P. 33-35] or oversized [Artemenko C.H., Avgustinovich VA, Zhukov AA, Interference switch of a resonant microwave compressor. Utility Model Patent No. 140527, Priority dated 10.29.2012, Registered on 05/10/2014].

In technical essence, the closest to the claimed switch of the resonant microwave compressor (prototype) is made on the basis of a T-shaped H-tee from a single-mode rectangular waveguide with a microwave switch located in the short-circuited straight arm mounted from the short circuit at a distance of 1/4 of the working wavelength in the waveguide [ Alvarez R., Birke D., Bern D., Lauer E., Scalapino D., Microwave energy compression in time for use in charged particle accelerators. - Nuclear technology abroad, 1982, No. 11, S. 36-39]. As you know, switches of this type are characterized by a high transient attenuation in the "closed" mode and are practically matched in the "open" mode, which, when switched quickly, ensures their high efficiency as devices for removing energy from the resonator. However, as noted, the level of operating power of such switches is limited by the electric strength of the insulating medium and the cross-sectional area of the waveguide from which the switch is made.

The technical result consists in increasing the operating power and increasing the stability of the switch by lowering the power of the switched wave by the execution of the switch in the form of a cascade connection of several H-tees.

This result is achieved by the fact that in the interference switch of the resonant microwave compressor, containing, like the prototype, a T-shaped H-tee with input and output straight arms, a half-wave short-circuited side arm and a microwave switch, in contrast to the prototype, a short circuit of the side arm of the main T -shaped H-tee is made of two additional T-shaped H-tees, the input straight half-wave shoulder of the first additional H-tee is combined with the side half-wave shoulder of the main H-tee, in the direct straight half-wave arm of the second additional H-tee is combined with the half-wave side arm of the first additional H-tee, the output straight quarter-wave shoulders of the additional H-tees are short-circuited, and the microwave switch is located in the short-circuited half-wave side arm of the second additional H-tee at a distance from the short-circuit quarter of the wavelength in the waveguide.

In the future, in the proposed switch, as adopted above, the prototype H-tee will be called the main one, and the remaining H-tees will be called additional. According to this terminology, in the proposed cascade of the primary and secondary H-tees, the input straight arm of each subsequent H-tee is connected to the lateral arm of the previous H-tee. The second straight shoulder of each additional H-tee is selected by the quarter-wave shoulder and is short-circuited. The commuting arm is the short-circuited half-wave lateral arm of the additional second (terminal) H-tee. In this arm, at a quarter of the wavelength in the waveguide from the short circuit, at the maximum of the electric field of the working wave, there is a microwave switch. The input shoulders of the additional H-tees are also half-wavelength, and the output short-circuited are quarter-wavelength. The decrease in switching power is achieved by the organization of the cascade of H-tees, agreed on the side of the side shoulder. As is known, in such H-tees the wave power in the lateral shoulder is two times less than the wave power supplied from the side of the straight shoulder. This means that when using only the main and one additional H-tee in the switch, the decrease in the switched power will be 2 ² . If two additional H-tees are used, the decrease will be ~ 2 ³ , i.e. almost eight times the value.

In FIG. 1 is a diagram of a resonant microwave compressor with an energy output device in the form of an interference switch, with a cascade of two additional H-tees in the side arm. The switch consists of the input and output of the main H-tee 1, its straight arms 5 and 8, additional H-tees 2, 3 with input half-wave straight shoulders 6 and 7, output quarter-wave straight shoulders 9 and 10, as well as a short-circuited switching side arm 11 additional H-tee 3 with microwave switch 4.

FIG. Figure 2 shows the calculated dependences of the amplification of the wave power in various elements of the microwave compressor with such a switch - in the resonator (curve 13) and the lateral arms of three H-tees (curve 14 - in the side arm of the main H-tee 1, curve 15 - in the arm of the first additional H tee 2 and curve 16 - in the shoulder of the second H-tee 3) - from the phase incursion of the wave in the resonator when the generator frequency deviates from the working frequency. The dependence of the amplification of the wave power in a cavity with a conventional switch (curve 12) is also shown here. The dependences are built on the basis of the following expressions (1) - (4) for a microwave compressor, studied experimentally as an example of a specific embodiment of the proposed switch with calculated values of the wave attenuation constants along the device elements: α≈0.0015 - along the resonator and β, γ, δ , ε, ξ≈0,0005 - along the shoulders of the H-tees 1, 2, 3 of the switch.

As follows from a comparison of the curves 12 and 13, the excess of the gain of the microwave compressor with a conventional switch over the gain with a cascade switch is a little more than 0.5 dB. The main reason for the excess is the additional energy loss to fill the cascade, which has a slightly larger volume than the H-tee of a conventional switch. To a lesser extent, the weaker transient attenuation of the cascade switch (Fig. 3) is also due to the longer shoulder lengths of its H-tees. Therefore, the studied switch is most suitable for microwave compressors with a sufficiently small volume of the switch compared to the volume of the storage resonator. However, from the dependencies of FIG. 2 it follows that such a switch can really allow to reduce the level of switched power by almost 2 ³ times. If, according to the dependencies of FIG. 2, the gain in the cavity reaches ~ 24.5 dB, then in the switching arm of the terminal second H-tee it does not exceed ~ 15.7 dB against ~ 21.5 dB for a conventional switch.

FIG. 3, 4 demonstrate transient attenuation of the switches in the accumulation mode (Fig. 3) and output (Fig. 4). In FIG. 3 - upper curve 17 - for cascade switch, lower 18 - for conventional switch. In FIG. 4 - upper curve 19 - for a conventional switch, lower 20 - for a cascade switch.

The output mode was simulated by changing the phase of the wave in the switching arm by 180 °. In the conventional switch it is carried out with a change in phase of the wave amplitude d _3, and in cascade with one H-tee - wave with amplitude d ₆ and two H-tees - wave with an amplitude of d _9. The corresponding dependences of the wave amplification at the output of the microwave compressor with a conventional and cascade switch with two H-tees are shown in FIG. four.

Graphs of FIG. 2, 3, 4 are constructed on the basis of relations (1) - (4) obtained by analyzing the operation of the device by the scattering matrix method:

,

Where

,

для волны с амплитудой b₂ в резонаторе,

for a wave with amplitude b ₂ in the resonator,

. И, наконец, для амплитуд волн в боковых плечах дополнительных Н-тройников имеемfor a wave with amplitude d ₂ at the compressor output and amplitude d ₃ in the side arm of the main H-tee. IN 2)

. And finally, for the wave amplitudes in the lateral arms of additional H-tees, we have

where b ₂ is the wave amplitude in the resonator;

d ₂ - wave amplitude at the compressor output;

d ₃ , d ₄ - the amplitude of the input and output waves of the lateral shoulder of the main H-tee;

d ₆ , d ₉ - wave amplitudes in the lateral shoulders of the additional second and third H-tee.

In these relations, α, β, γ, δ, ε, ξ and φ, ψ, θ, κ are the damping constants and the phase incursion of the waves with their double range in the cavity and shoulders of the H-tees:

α is the attenuation constant of the wave with double run along the resonator;

β is the wave attenuation constant for its double run along the lateral shoulder of the main H-tee;

γ is the wave attenuation constant for its double range along the short-circuited shoulder of the main H-tee;

δ is the wave attenuation constant for its double run along the lateral shoulder of the first additional H-tee;

ε is the damping constant of the wave during its double run along the short-circuited shoulder of the first additional H-tee;

ξ is the constant of wave attenuation at its double run along the lateral shoulder of the second additional H-tee;

φ is the phase incursion of the wave with double run along the resonator;

ψ is the phase incursion of the wave with double run along the lateral shoulder of the main H-tee;

θ - the phase incursion of the wave with double run along the lateral shoulder of the first additional H-tee;

κ is the phase incursion of the wave with its double run along the lateral shoulder of the second additional H-tee.

The device operates as follows. In the accumulation mode, the energy in the switch is stored only in the input straight arms 5, 6, 7 of the N-tees 1, 2, 3 and the switching side arm 11 of the second additional H-tee 3. In the short-circuited quarter-wave straight arms 8, 9, 10, the energy is not stored . When switching to output mode, the H-tees of the cascade open sequentially in the reverse order, starting from the second additional (terminal) H-tee 3. After the microwave switch 4 is activated in the side arm 11 of the terminal H-tee 3, this H-tee 3 opens, and the half-wave length of its input arm changes to the quarter-wave total length of the input straight arm 7 and the short-circuited second straight arm 10 of the H-tee 3. This leads to the sequential filling of all elements of the chain of H-tees 1, 2, 3 with a working wave and inver uu phase of the wave emitted at the output main tee H-1 of the input port 6 of the first additional H 2-tee, and opening the switch. Moreover, since in the lateral arm 11 of the H-tee 3, the wave power is eight times less than the wave power in the input arm 5 of the main H-tee 1, this provides both the ability to increase the operating power of the switch and increase the stability of its operation.

Studies of the operability and advantages of the proposed switch were performed on a compressor of a 10-cm wavelength range with an operating frequency of f ₀ ≈ 2800 MHz and energy output through a conventional switch based on one H-tee, as well as through a cascade switch with two and three identical H-tees. H-tees were made of a circular waveguide with a diameter of 90 mm. In addition to the main wave, a wave of type E ₀₁ can propagate along a waveguide of this diameter at a frequency of 2800 MHz. At such an operating frequency, this wave does not have a noticeable effect on such basic characteristics of H-tees as transient attenuation in the “open” and “closed” modes and the operating power.

A copper cylindrical resonator with a diameter of 120 mm and a length of ~ 550 mm was used as an energy storage device, which was coupled to a switch through a Chebyshev-type smooth matching junction with a power reflection coefficient of not more than 0.005. The matching band was ~ 300 MHz. The total cavity length was 710 mm. The working mode of oscillations was H _{11 (11)} with the measured intrinsic Q factor Q ₀ ≈3 × 10 ⁴ and the estimated time T _{from the} double mean free path along the resonator of ~ 5.1 ns. Therefore, the maximum calculated gain G of the compressor at a minimum duration of the generated pulses equal to the time T _{s of the} double mean free path along the resonator was G≈Q ₀ / 2πf ₀ T _c ≈25.1 dB.

A magnetron microwave generator with a pulse power adjustable in the range of ~ 0.8–2 MW and a fixed duration of ~ 3 μs served as a source of input pulses. With such a pulse duration and the indicated Q factor of the resonator, the optimal input coupling coefficient was ~ 1.3. The accumulation efficiency in this case is ~ 0.53, and the gain is ~ 24.9 dB. Thus, the maximum calculated compressor pulse power was 625 MW for a duration of ~ 5.1 ns. The calculated field strength in the switching arm of a conventional switch is close to 290 kV / cm. In a cascade switch with one additional H-tee, this tension can drop to ~ 145 kV / cm and with two tees to ~ 105 kV / cm.

Before conducting studies of the cascade switch, a control experiment was performed with a conventional switch. The trigatron type microwave discharger was used as a microwave switch. The arrester was a purged gas-filled quartz tube oriented along the diameter of the switching section of the H-tee parallel to the power lines of the electric field H _{11 of the} working wave, with an electric backlight discharger at one of the ends of the tube. The working atmosphere in the tube was argon with the addition of 5-10% SF6 gas under an overpressure of 3-4 atm. The cavity was insulated with nitrogen with the addition of 30–40% SF6 gas under an overpressure of 4–6 atm. Under such conditions and an input pulse power of up to 2 MW, the microwave compressor generated pulses with a power of up to 300 MW with a gain of up to 22 dB, and a duration of about 4.8 ns in level - 3 dB.

When the gas discharge tube of the microwave switch was filled only with argon, stable spontaneous breakdowns began in the tube with an input pulse power of not more than 1 MW and output pulses of ~ 100 MW. The emergence of stable spontaneous breakdowns served as a criterion for achieving the threshold operating power of the switch.

The cascade switch experiment program included three steps. At the first stage, we studied the work with a cascade of H-tees of the usual configuration, i.e. not subject to approval from the lateral shoulder. This configuration is traditionally used in the developed compressors with a conventional switch. According to studies, in this design, the wave power in the storage volume and the switching arm of the switch is comparable and the output of the microwave compressor is quite well matched, which ensures energy output almost during the double travel of the wave along the resonator.

At the second stage of research, H-tees were specially coordinated from the side of the lateral shoulder. The coordination was ensured by the selection of the inductive diaphragm and the place of its installation in the lateral shoulder of the H-tee at a certain distance from the joint of his shoulders. The achieved value of the coefficient of standing voltage waves (VSWR) did not exceed 1.2 in the frequency band ~ 300 MHz.

The third stage included matching the output of the cascade switch made of H-tees coordinated from the side of the lateral arm. As experiments showed, the compressor output with such a switch is matched worse than a switch with H-tees that are not matched on the side of the side arm. Coordination was carried out by a movable diaphragm of a collet type installed in the output arm of the main H-tee.

The research ended with experiments with a cascade switch of three H-tees, coordinated from the side of the lateral shoulder and with a coordinated output.

The main result of the experiments of the first stage boils down to the fact that a distinctive feature of the switch with a cascade of uncoordinated H-tees is the practical absence of an increase in the electric strength and, accordingly, the compressor operating power. The increase in the input and output power was within the measurement accuracy and did not exceed, respectively, 1.1 MW and 110 MW when the microwave switch was working with a tube filled with argon. The maximum gain was no more than 20dB.

The second series of experiments involves the study of the operation of a compressor with a cascade switch of H-tees, coordinated from the side of the side arms. This coordination led to a significant increase in the dielectric strength of the switch, but increased the rise time of the pulse and lengthened the pulse. Such a change is due to an increase in the transient time on the matching elements and a mismatch in the compressor output. The increase in electric strength was manifested in the possibility of the microwave switch operating almost exclusively on argon with an input pulse power of up to 2 MW and a tube pressure of 0-0.5 ati. In this case, the pulses elongated to 6.2 ns, the gain reached ~ 20.5 dB, and the power was -220-230 MW. This means that when a gas discharge tube is filled with a mixture of argon and SF6 gas under a pressure of 3-4at, an almost twofold increase in the power of the compressor output pulses is possible and the power is brought to a level of about 400-450 MW.

Matching the compressor output with a cascade switch with one H-tee in the side shoulder allowed us to get rid of the “tail” of the pulse and increase the gain to ~ 21 dB, and the power to ~ 250 MW.

A cascade of three H-tees with matched shoulders and exit was investigated in the final series. These experiments confirmed a further decrease in the level of switched power and especially clearly demonstrated the effect of the energy stored in the cascade on the parameters of the generated pulses, in particular, on the duration and power. This was manifested in an increase in duration to 9–10 ns and a decrease in gain to 18 dB. This effect is associated with a sufficiently large energy reserve in the cascade due to the comparability of its volume with the volume of the resonator and the inertia of the processes occurring in it. The inertia is due to the reactivity of the matching elements of the three tees of the cascade. Therefore, this switch configuration is acceptable for compressors with larger storage cavities.

Thus, the possibility of increasing the performance of a resonant microwave compressor with energy output through an interference switch based on a waveguide H-tee is confirmed. The possibility can be realized by performing a switching side switch arm in the form of a cascade of serially connected H-tees, coordinated from the side of the side shoulder, for example, by connecting each subsequent H-tee with an input straight shoulder to the side shoulder of the previous H-tee. The most effective such device can be in microwave compressors, the time of energy output in which is much longer than the travel time of the wave along the device. Cascading devices can be useful in compressors with solid-state switches, which have a significantly lower level of operating power than gas-discharge or electron-beam switches.

Cascade switches will be operable even when they are made from oversized H-tees or from packages of ordinary H-tees with a rectangular oversized commuting arm with a working wave H ₀₁ . Microwave compressors created with such switches will be able to generate multi-gigawatt microwave pulses.

Claims (1)

An interference switch of a resonant microwave compressor containing a T-shaped H-tee with input and output straight shoulders, a half-wave short-circuited side shoulder and a microwave switch, characterized in that the short circuit of the side shoulder of the main T-shaped H-tee is made of two additional T- shaped H-tees, the input straight half-wave shoulder of the first additional H-tee is combined with the side half-wave shoulder of the main H-tee, the input straight half-wave shoulder of the second additional H-tee ynika combined with a half-wave of the first additional lateral shoulder-H tee output direct shoulders additional quarter-H-tees are short-circuited, and the microwave switch is a half-wavelength shorted sidearm second additional N-tee at a distance from the short-equal to a quarter wavelength in the waveguide.

Images