RU2803456C1 - Module for forming a quasi-random signal of microwave frequencies - Google Patents

Abstract

FIELD: microwave engineering.

SUBSTANCE: part of communication systems using quasi-random signals, including pulses, to interfere with radio communications and radar. The module for generating a quasi-random signal of microwave frequencies contains a segment of a coplanar strip line, a lithium niobate crystal, a device for separating incident and reflected waves, a device for adding incident waves, a signal generator with linear frequency modulation of oscillations, a sync pulse generator for starting a signal generator with linear frequency modulation. A segment of a coplanar strip line is made on a dielectric substrate, the lower side of which is metallized, the side screens located on the upper side are connected to the metallization of the lower surface through plated hole. The current-carrying strip is sseparated from the side screens by gaps, on the upper side, on the side of the current-carrying strip and the side screens, there is a lithium niobate crystal, the transverse dimensions of which, facing the current-carrying strip, cover the gaps between the current-carrying strip and the side screens, and the longitudinal dimensions of the crystal do not exceed the length of the current-carrying coplanar stripes. The input of the coplanar strip line receives an incident wave of linear-frequency-modulated oscillations from the first output of the device for the separator of incident and reflected waves, which is the input of the wave reflected from the lithium niobate crystal. The wave reflected from the lithium niobate crystal enters the second output of the device for separating the incident and reflected waves, connected to the first input of the device for combining the incident waves. The output of the coplanar strip line is connected to the second input of the incident wave interference. The output of the module for forming a quasi-random signal of microwave frequencies is the output of the device for adding incident waves.

EFFECT: expansion of the operating frequency range in which a quasi-random signal is formed.

1 cl, 10 dwg

Description

The invention relates to the field of microwave technology and can be used as part of communication systems that use quasi-chaotic signals, including pulsed ones, to create interference in radio communications and radar, and can also be used for full-scale modeling of the interference environment during radiophysical research.

Known for the “Complex for semi-natural modeling of a noise environment”, RU 190950, application 2019100153 dated 01/09/2019. The purpose of the utility model is to create a complex of semi-natural modeling of the interference environment, providing research to analyze the impact of various types of interference on radar stations and the development of noise protection algorithms. In contrast to the known means of generating a noise environment with fixed polarization parameters of the electromagnetic field (linear or circular), the complex of semi-natural modeling of the interference environment also allows you to generate polarization noise, polarization imitation and pulse noise in the classical and extended basis of signals (with a controlled polarization vector).

Klystron self-oscillators of chaos are common (S.V. Grishin, B.S. Dmitriev, V.N. Skorokhodov. Generation of giant amplitude pulses in a klystron self-oscillator of chaos // Letters to ZhTP, 2019, volume 45, issue 19. October 12. DOI : 10.21883/PJTF.2019.19.48315.17928). The self-oscillator is assembled according to a noisetron circuit, which contains two five-resonator transient klystrons connected in series in a ring, one of which operates in the mode of linear signal amplification (linear klystron), and the other in the mode of nonlinear signal amplification (nonlinear klystron). The obvious disadvantage of the chaos generator is its narrow frequency band (in the above article from 2700 MHz to 2900 MHz).

There is a known noise generator based on an avalanche-transit diode in the millimeter wavelength range (E.A. Myasin. Noise generation in a single-frequency generator based on an avalanche-transit diode in the millimeter wavelength range under the influence of low-frequency harmonic oscillations // Letters to ZhTP, 2021, volume 47, issue November 22, 26). The excitation of noise oscillations and the maximum expansion of the spectrum of high-frequency noise in a generator based on an avalanche-transit diode with an increase in the amplitude of low-frequency oscillations are associated with a short-term decrease in the diode current below the starting generation current.

There is a known method for generating microwave noise oscillations in generators based on an avalanche-transit diode (RU 2661283, Method for generating microwave noise oscillations, published July 13, 2018, Bulletin No. 20), which consists in setting the voltage higher in the power supply circuit of the avalanche-transit diode disruptive, characterized in that they change the width of the spectrum of microwave oscillations, depending on the quality factor of the electrodynamic system of the generator, by changing the set voltage under the influence of a modulating low-frequency noise voltage with a changing value of its level and with a spectrum width and cutoff frequency of at least 3 MHz. The disadvantage of this method is the narrow noise frequency band due to the limited operating mode of the nonlinear element - the avalanche diode. In addition, an increase in voltage above the breakdown voltage reduces the reliability of the noise generator.

A known generator of chaotic oscillations, RU 2768369, publ. 03/24/2022, Bulletin. No. 9. The generator circuit provides a technical result consisting in expanding the possibilities of restructuring the characteristics of the generated chaotic signal without changing the parameters of the energy-storing elements due to the fact that the chaotic attractor is modified without changing the ratings of the reactive elements by changing the parameters of the transfer characteristic of the nonlinear impedance converter. The chaotic oscillation generator contains a resistor, a two-pole element with capacitive reactance, a two-pole element with negative inductive reactance, a two-pole element with inductive reactance, a nonlinear impedance converter and a linear current converter, wherein the nonlinear impedance converter contains a first voltage amplifier, first, second and third resistors, a first and a second active four-terminal network and a first current generator, a two-pole element with negative inductive reactance contains a two-pole element with inductive resistance, a third active four-terminal network, second and third current generators, a linear current converter contains a transistor, a second voltage amplifier, first and second current mirrors, a fourth, fifth and sixth current generators.

The disadvantage of the generator of chaotic oscillations according to patent RU 2768369 is the limitation of the frequency range due to the limited frequency characteristics of the elements in the generator circuit.

The closest solution is the invention RU 2740397 “Method for generating chaotic microwave pulses of subnanosecond duration”, publ. 01/14/2021, Bulletin. No. 2. In the method of generating chaotic microwave pulses, which consists in excitation, using microstrip converters, of surface and reverse bulk magnetostatic spin waves in the arms of an irregular L-shaped waveguide located in a constant magnetic field, connected to the feedback circuit of a self-oscillator having two series-connected active elements , one of which is designed to operate in the mode of linear amplification of the microwave signal connected to the output arm of the waveguide, and the other, connected to the input arm of the waveguide, in the mode of saturating its output power, forming the power level of the microwave signal with the possibility of forming three-wave and four-wave nonlinear spin-wave interactions, according to the invention, in the input arm of an L-shaped ferromagnetic waveguide, reverse bulk magnetostatic spin waves with negative anomalous dispersion are excited, and in the output arm, surface magnetostatic spin waves with positive normal dispersion are excited due to the direction of a constant magnetic field perpendicular to the input microstrip converter and parallel to the output microstrip converter, wherein four-wave nonlinear spin-wave interactions are formed in the input arm of the L-shaped waveguide, and three-wave nonlinear spin-wave interactions are formed in its output arm.

The disadvantage of RU 2740397 method for generating chaotic microwave pulses of subnanosecond duration and the device that implements it is the narrow spectral frequency band - from 2.5 GHz to 5 GHz, since wave processes are limited by the possibility of the formation of three-wave and four-wave nonlinear spin-wave interactions.

The technical result of the invention is to expand the operating frequency range in which a quasi-chaotic signal is generated.

The main technical problem solved by the proposed solution is aimed at expanding the operating frequency range in which a quasi-chaotic signal is formed due to the occurrence of many resonances in a structure consisting of a coplanar stripline transmission line, in the upper half-plane of which a bulk lithium niobate crystal is located, electromagnetic coupling of the crystal with the coplanar stripline The line is ensured by the presence of two gaps between the current-carrying strip and the side screens.

The stated technical problem is solved by the fact that the module for generating a quasi-chaotic signal of ultra-high frequencies, containing a section of a coplanar strip line, a lithium niobate crystal, a device for separating incident and reflected waves, a device for adding incident waves, a signal generator with linear frequency modulation, a clock pulse generator for starting the signal generator with linear-frequency modulation, characterized in that a section of a coplanar strip line is made on a dielectric substrate, the lower side of which is metallized, the side screens located on the upper side are connected to the metallization of the lower surface through metallized holes, the current-carrying strip is separated from the side screens by gaps on the upper side on the side of the current-carrying strip and the side screens there is a lithium niobate crystal, the transverse dimensions of which, facing the current-carrying strip, cover the gaps between the current-carrying strip and the side screens, and the longitudinal dimensions of the crystal do not exceed the length of the current-carrying strip of the coplanar line; the incident a wave of linearly frequency-modulated oscillations from the first output of the incident and reflected wave separator device, which is the input of the wave reflected from the lithium niobate crystal; the wave reflected from the lithium niobate crystal enters the second output of the incident and reflected wave separator device, connected to the first input of the addition device incident waves, the output of the coplanar strip line is connected to the second input of the incident wave combining device, the output of the module for generating a quasi-chaotic microwave signal is the output of the incident wave combining device.

The invention is illustrated by drawings in Figs. 1 – fig. 10:

in fig. Figure 1 shows the design of a module for generating a quasi-chaotic microwave signal;

in fig. Figure 2 shows the electric field pattern (equipotential lines) in a coplanar strip line with a grounded base, two side screens and filling the upper half-plane with a crystal;

in fig. Figure 3 shows a section of a coplanar strip line with a lithium niobate crystal installed on it;

in fig. Figure 4 shows the frequency dependence of the transmission coefficient modulus and frequency dependence of return losses a piece of coplanar strip line without a lithium niobate crystal;

in fig. Figure 5 shows the frequency dependence of the phase shift And a piece of coplanar strip line without a lithium niobate crystal installed on its upper surface;

in fig. Figure 6 shows the frequency dependence of the transmission coefficient modulus a segment of a coplanar strip line with a lithium niobate crystal mounted on its upper surface with an XZ plane;

in fig. Figure 7 shows the frequency dependence of the modulus of the return loss coefficient a segment of a coplanar strip line with a lithium niobate crystal mounted on its upper surface with an XZ plane;

in fig. Figure 8 shows the frequency dependence of the phase shift a section of a strip line with a lithium niobate crystal mounted on its upper surface with an XZ plane;

in fig. Figure 9 shows the frequency dependence of the phase shift a section of a strip line with a lithium niobate crystal mounted on its upper surface with an XZ plane;

in fig. Figure 10 demonstrates the frequency dependence of voltage at the output of the module for generating a quasi-chaotic microwave signal, provided that the voltage amplitude of the linear-frequency signal supplied to the input of the coplanar stripline is constant.

The module for generating a quasi-chaotic microwave signal (see Fig. 1) contains: a section of a coplanar strip line with a current-carrying strip 1 on a dielectric substrate 7; lithium niobate crystal 2; device for separating incident and reflected waves 3; device for adding incident waves 4; linear frequency modulation signal generator 5; clock generator 6; metallization of the bottom side of the substrate 8; side screens 9,10, separated from the current-carrying strip by gaps; metallized holes 11 connecting the side screens with the metallization of the lower side of the substrate. The input of the module for generating a quasi-chaotic microwave signal is the input of the clock pulse generator, and the output is the output of the incident wave combining device.

The input of the generation module receives a signal that triggers the operation of the clock pulse generator 6. From the output of the clock pulse generator, the signal is fed to the input of the signal generator 5 with linear frequency modulation, which lies in the range, for example, from 10 MHz to 25 GHz. The chirp signal, through a device for separating the incident and reflected waves 3, is supplied to the input of the current-carrying strip 1 of a piece of coplanar strip line located on the dielectric substrate 7. On the back side of the substrate 7, metallization 8 is applied. In the gaps between the current-carrying strip 1 and planar screens 9, 10, connected through metallized holes 11 with metallization of the lower side of the substrate, an electromagnetic field (EMF) is formed, the picture of which in the form of equipotential lines is shown in Fig. 2. The electromagnetic field in the gaps of the coplanar line in the presence of side screens and a grounded base is divided into two connected flows. The first is in the dielectric substrate 7, the second is in the crystal 2 (see Fig. 1 and Fig. 2). The substrate is made of a homogeneous and isotropic dielectric, and the lithium niobate crystal, being uniaxial and characterized by a trigonal crystal system, has anisotropy of dielectric properties (Yariv A., Yukh P. Optical waves in crystals. M.: Mir, 1987). The electromagnetic field excites electromagnetic oscillations in the lithium niobate crystal by two resulting dipole-type sources in in-phase mode. When a microwave quasi-T wave propagates along a current-carrying strip of a coplanar strip line and along the axisz crystal electric field has two components, along the axisx and along the axis respectively (see Fig. 3). This causes an electro-optical effect for waves polarized in the directionsx’ and y’, with the axesx’ and y’ and turned at an angle relative to the axesx And (Fig. 3) crystal structure (Zyuryukin Yu.A., Pavlova M.V., Drevko D.R. Wave equations for describing the Pockels effect in crystals and their analysis using the example of a lithium niobate crystal // News of universities "PND", t. 18, No. 5, 2010, pp. 125-137). Velocities of the considered waves with components And are different, because relative static dielectric constants: ε_eleven= 84.6, ε₃₃=29.1 (E. A. Pospelova, I. S. Azanova. Periodic domain structure in lithium niobate single crystals. https://elis.psu.ru/node/381044). A “slow” wave is formed with a speed and “fast” with speed. Due to the alternating process of changing fields And the situation reverses with frequencyfs a linear frequency modulated signal acting on a piece of coplanar strip line and a crystal.

Consequently, the fields in the gaps between the current-carrying strip and the side screens of the CPL change the polarization state of the incident electromagnetic wave in the bulk of the crystal. Since the crystal has significantly significant dimensions, its bottom layer, lying on the current-carrying strip and the side screens of the CPL, is subject to interaction And , varying from the bottom surface to the top surface along the x- axis and from the centers of the gaps to the side surfaces along the y -axis. In this case, a transformation of a quasi-T wave occurs in the current-carrying strip, characteristic of strip transmission lines with transverse dimensions much smaller than the wavelength. This transformation is caused by the influence of the field components arising inside the crystal due to polarization and “splitting” of the quasi-T wave of the strip structure into: firstly, the natural waves of the crystal as a volumetric dielectric resonator with a spectrum of natural waves; secondly, to waves associated with the main quasi-T wave, the phase velocities of which are significantly different. The emergence of combined waves due to the transformation of the quasi T-wave leads to their interference, because phase velocities are different. As shown by experimental studies of the frequency characteristics of a coplanar line segment without a crystal and with a crystal located on it (see Fig. 3) on a P426 vector network analyzer produced by JSC NPF Mikran, the above processes lead to amplitude and phase quasi-chaotic oscillations, which are illustrated graphs of Fig. 4 – fig. 10. Figure 4 and Figure 5 show the frequency characteristics of a section of a coplanar strip line without a crystal: transmission coefficient modulus , return losses , phase gain , phases of the backscattering coefficient . From the given dependencies (Fig. 4) it is clear that up to a frequency of approximately 20 GHz, the characteristics of a coplanar line segment have the form characteristic of transmission lines with moderate losses and an almost linear phase-frequency characteristic of the transmission coefficient (Fig. 5). Installation of a lithium niobate crystal leads to the appearance of many resonances in the characteristic strip structure in the frequency band from about 4 GHz to 20 GHz, as illustrated in FIG. 6. Moreover, since the input impedance of the device changes when resonant oscillations occur in the crystal and coplanar strip line, the frequency dependence of the return losses is also characterized by many resonances (Fig. 7). Emerging resonance phenomena in the coplanar strip line-niobate crystal system due to the interference of waves with different phase velocities lead to quasi-chaotic changes in the phase of the transmission coefficient , which is shown in Fig. 8, as well as to changes – fig. 9. Analysis of frequency dependences | S ₁₁ ( f )|, | S ₂₁ ( f )| (Fig. 6, Fig. 7) shows different positions of the maxima of the dynamic range of quasi-chaotic signals on the frequency axis. Thus, the greatest level of difference between max(| S ₂₁ ( f )|) and min(| S ₂₁ ( f )|) is observed in the band 10.0–17.5 GHz, and the range of changes between max(| S ₁₁ ( f ) |) and min(| S ₁₁ ( f )|) is maximum in the band 4.0 – 10.0 GHz. Approximately _the same dependence is typical for quasi-chaotic changes in the phases arg( S21 ( f )) and arg( S11 ( f )) (Fig _. 8 and Fig. 9). The spectral density of a quasi-chaotic signal is equalized as follows. A device for separating the incident and reflected waves 3 is installed between the linear frequency modulated signal generator 5 (Fig. 1) and the input of the coplanar strip line. The incident wave arrives at the input port of device 3, the reflected wave arrives at the output port of this device and, due to its directional properties, branches off to the reflected signal port. Then reflected from the input port of the coplanar strip line is fed to the first input port of the signal adding device 4. The signal passed through the coplanar strip line with a lithium niobate crystal placed on it from its output port is fed to the second input port of the adding device 4. At the output of the signal adding device 4, the vector sum of the signal reflected from the input port and the signal from the output port of the coplanar strip line is obtained. Let us denote the voltages of the waves propagating in the module as follows:

– the voltage of the wave incident at the input of the coplanar line after the signal passes from the output of the signal generator 5 with linear frequency modulation through the device for separating the incident and reflected waves 3;

– voltage of the wave line reflected from the input of the coplanar wave line supplied to the first input of the wave combining device 4;

– voltage at the output of a segment of a coplanar strip of a wave line falling on the second input of the wave combining device 4.

We assume that the function known. Then at the output of addition device 4 we obtain the total voltage

. (1)

Let us assume that the amplitude is equal to 1. When determining the total voltage from expression (1), the initial experimentally obtained frequency dependences of the modulus of the transmission coefficient are taken as (Fig. 6), reflection coefficient module (return loss) (Fig. 7), reflection coefficient phases (Fig. 8), reflection coefficient phases (Fig. 9). Moving on to the complex recording form And we get And .

Frequency dependence shown in Fig. 10. From a comparison of Figs. 6 and fig. 10 we see that the addition of the wave energy reflected from a segment of a coplanar line with a lithium niobate crystal and the wave energy passing through the coplanar line and crystal increases the average level and equalizes the frequency dependence .

Thus, based on the experimental characteristics carried out, the performance of the proposed module for generating a quasi-chaotic microwave signal is shown.

Claims (1)

A module for generating a quasi-chaotic signal of ultra-high frequencies, containing a section of a coplanar strip line, a lithium niobate crystal, a device for separating incident and reflected waves, a device for adding incident waves, a signal generator with linear frequency modulation of oscillations, a clock pulse generator for starting a signal generator with linear frequency modulation, characterized in that a section of a coplanar strip line is made on a dielectric substrate, the lower side of which is metallized, the side screens located on the upper side are connected to the metallization of the lower surface through metallized holes, the current-carrying strip is separated from the side screens by gaps, on the upper side from the side of the current-carrying strip and side screens there is a crystal made of lithium niobate, the transverse dimensions of which, facing the current-carrying strip, cover the gaps between the current-carrying strip and the side screens, and the longitudinal dimensions of the crystal do not exceed the length of the current-carrying strip of the coplanar line; an incident wave of linear frequency is received at the input of the coplanar strip line. modulated oscillations from the first output of the device for separating incident and reflected waves, which is the input of the wave reflected from the lithium niobate crystal, the wave reflected from the lithium niobate crystal enters the second output of the device for separating incident and reflected waves, connected to the first input of the device for adding incident waves, the output is coplanar The strip line is connected to the second input of the incident wave combining device; the output of the module for generating a quasi-chaotic microwave signal is the output of the incident wave combining device.