RU2327278C2 - Method of generation of wide-band shf chaotic signals and generator of wide-band shf chaotic signals - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to generation of the wide band SHF chaotic signals and may be used in communication, radars, instruments. The method allows reducing the irregularity of spectral characteristic and features a consecutive signal amplification by, at least, two amplification stages, the first operating in a minor amplification mode, while the other one, in a mode of nonlinear amplification. The signal is limited after amplification in the third amplification cascade which operates in a limiting mode. A part of the signal, after limitation, is branched off in the load, and the part of signals left after branching off is sent to the first amplification cascade. The generator incorporates the first and second amplification cascades, the limitation cascade made as the third amplification cascade, and a microband coupler.

EFFECT: reduced irregularity of spectral characteristic.

10 cl, 7 dwg

Description

FIELD OF THE INVENTION

The present invention relates generally to radio engineering and, in particular, to the formation of broadband microwave (microwave) chaotic signals.

State of the art

Chaotic signals are increasingly used in various fields of technology, such as communications, radar, measurement technology, medicine, etc.

Various methods and devices are now known for generating (generating) broadband microwave chaotic signals. Thus, a chaotic generator is known (US patent No. 6842745, publ. 11.01.2005), in which there are four operational amplifiers, covered by several feedback loops. This circuit is quite complex and does not allow to obtain a microwave signal due to the use of operational amplifiers.

It is known to use two traveling wave tubes (TWTs) to generate chaotic oscillations, the first TWT operating in linear amplification mode, and the second TWT working in nonlinear mode on a falling section of the amplitude characteristic (USSR author's certificate No. 1125735, publ. 11/23/1984). Such a generator is large and does not allow to obtain wideband signals without additional modulation.

Another microwave chaotic signal generator is made on microstrip lines, into the gaps of which two bipolar transistors are soldered, as a result of which two dynamic systems are formed (USSR patent No. 1806439, publ. 30.03.1993). This generator implements a method for generating broadband microwave chaotic signals, however, the unevenness of the spectral characteristics of these dynamic systems is quite large, because the basis of this method is the interaction of two coupled multi-frequency microwave generators.

The closest analogues to the objects of the claimed group of inventions are described in US patent No. 6127899 (publ. 03.10.2000). A method for generating broadband microwave chaotic signals is known from this patent, which consists in sequentially amplifying the signal with at least two amplifying stages, limiting the signal after amplification, and supplying the signal after limiting to the first of the mentioned amplifying stages.

From the same U.S. Patent No. 6,127,899, a broadband microwave chaotic signal generator is known comprising first and second amplification stages connected in series and a limiting stage, the output of which is connected to the input of the first amplification stage.

The disadvantage of these methods and the generator is that to obtain chaotic signals, it is necessary to have an additional generator of periodic oscillations with controlled amplitude and frequency.

Disclosure of invention

The problem to which the present invention is directed is the creation of such a method for generating and generator of broadband microwave chaotic signals that could overcome the above disadvantages of existing analogs and provided broadband and ultra-wide microwave chaotic signals with low spectral characteristics in a simple circuit without using additional modulation and generation.

To achieve the specified technical result in the first of the claimed group of objects - a method for generating broadband microwave chaotic signals, which consists in sequentially amplifying the signal with at least two amplifier stages, limiting the signal after amplification and applying the signal after limiting to the first of the mentioned amplifier stages , in accordance with the present invention, the amplification of the signal is carried out by amplifier stages so that the first of them operates in the amplification mode is small second signal, and the second - in the mode of non-linear signal amplification; the signal is limited in the third amplifier stage, which operates in the signal limit mode and forms, together with the first and second amplifier stages, an amplifier path; branch part of the signal after limiting the load; the first of the amplification stages serves the remainder of the signal after the branch.

An additional feature of the method of the present invention is that the signal branch is performed using a frequency selective coupler.

Another feature of the method of the present invention is that they pass the signal after at least one of the amplification stages through the corresponding frequency-selective structure having a predetermined frequency response.

Another feature of the method of the present invention is that, according to predetermined laws, either the amplification of the amplification stages or the parameters of the frequency-selective structures are changed, whereby the parameters of the generated signals are controlled.

Finally, another feature of the method of the present invention is that the sequential amplification and limitation of the signal in the amplification path is repeated in at least one other amplification path parallel to this amplification path, and the signals of all parallel amplification paths are summed, after which the signal is branched into the load.

In order to achieve the same technical result, in the second of the claimed group of objects — a broadband microwave chaotic signal generator, comprising first and second amplification stages connected in series and a limiting stage, the output of which is connected to the input of the first amplifier stage, in accordance with the present invention, the first amplifier stage operation in the mode of amplification of small signals, the second amplifier stage is designed to operate in non-linear amplification of signals, and the cascade is limited The circuit is made in the form of a third amplifier stage, designed to operate in the limiting mode, while the output of the third amplifier stage is connected to the input of the first amplifier stage through a microstrip signal coupler to the load.

An additional feature of the generator of the present invention is that at least one of the series connections of the amplifier stages and the connection of the third amplifier stage to the signal coupler to the load is made through the corresponding microstrip frequency-selective structure.

Another feature of the generator of the present invention is that the amplifier stages and / or frequency-selective structures are made adjustable to allow control of the parameters of the generated signal.

Finally, another feature of the method of the present invention is that at least one additional amplification path is introduced into it, which includes amplification stages similar to the mentioned amplification stages, while the inputs of all first amplification stages are connected to the corresponding outputs of the signal coupler to the load , and the outputs of all third amplifying stages are connected to the inputs of the adder, the output of which is connected to the signal coupler to the load.

Brief Description of the Drawings

In the following drawings and in the text of the further description, the same reference numbers indicate the same or similar elements.

Figure 1 depicts a General block diagram of a generator of broadband microwave chaotic signals, illustrating the principle of generating such signals of the present invention.

2 depicts one embodiment of a broadband microwave chaotic signal generator of the present invention.

Figure 3 represents a specific example of the implementation of the generator with the structure of figure 2 when modeling it in the ADS package.

Figure 4 shows the implementation of the signal and its power spectrum for typical chaotic modes of the generator during circuit simulation in the ADS package.

5 depicts another embodiment of a broadband microwave chaotic signal generator of the present invention.

6 is a functional topological diagram of a microstrip embodiment of a broadband microwave chaotic signal generator of the present invention.

Fig.7 is an example of a power spectrum of one of the typical modes of the layout of the generator of the present invention in the embodiment of Fig.2.

Detailed Description of Embodiments

The block diagram of a broadband microwave chaotic signal generator shown in FIG. 1 illustrates the general principle of generating such signals according to the present invention.

A broadband microwave chaotic signal generator comprises a first amplifier stage 1, which operates in a small signal amplification mode (“linear amplifier”), a second amplifier stage 2, which operates in a non-linear signal amplification mode (“non-linear amplifier”), and a third amplifier stage 3, which works in signal limiting mode (“amplifier-limiter”). All of these amplifier stages 1, 2, and 3 are connected in series, starting from the first, while the output of the third amplifier stage 3 is connected to the input of the frequency-selective coupler 4. This frequency-selective coupler 4 provides a branch of the amplified and limited signal to load 5 and supply the remaining part of the signal to the input of the first amplifier stage 1.

Thus, amplifier stages 1-3 and coupler 4 form a closed loop, which allows you to generate a chaotic signal in the same way as in the scheme of the aforementioned US patent No. 6842745. However, in the present invention, in addition to replacing the diode limiter with an amplifier stage operating in the limit mode, the amplifier stages 1-3 themselves are made not on operational amplifiers, but on microwave transistor amplifiers. The coupler 4 is a frequency selective, and not just a resistor divider. All this allows you to get a broadband microwave chaotic signal.

To improve the characteristics of the generated signal in a real generator of a broadband microwave chaotic signal between the first and second amplifier stages 1, 2, between the second and third amplifier stages 2, 3 and between the third amplifier stage 3 and the frequency-selective coupler 4, the first, second and third frequency -selective structures 6, 7 and 8, respectively (figure 2). In practice, such frequency-selective structures can be installed selectively, say, only between amplification stages 1, 2 and 2, 3, or just one frequency-selective structure in any of these positions. If necessary, additional amplifier stages (for example, another linear amplifier) can be added to the generator circuit, and then the number of frequency-selective structures can be correspondingly increased for installation between each pair of amplifier stages.

The method for generating a broadband microwave chaotic signal described above is illustrated by an example of circuit simulation of such a generator in the ADS (Advanced Design System) software package. Structurally, such a generator corresponds to the circuit of FIG. 2. A detailed representation of the blocks of this generator is shown in FIG. As amplifiers, the MSA-0986 chip is used, designed to operate in the frequency range up to 6 GHz. This chip is included in the bias circuit, which is standard for this device and sets the operating mode of the device (figa). The bias circuit consists of a voltage source V0, resistance R0, inductance L0, and two blocking capacitances Cs. The parameters of the elements V0, R0, L0 and Cs in the bias circuit of the amplifier can be changed in order to set the desired operating mode, i.e. either a small signal amplification mode, or a nonlinear amplification mode, or a signal limiting mode, depending on the role of a particular amplifier in the generator circuit of the present invention.

The function of the frequency-selective structure is performed by the RLC circuit shown in Fig.3b and consisting of a chain of series-connected resistance R1, inductance L1, capacitance C1 and an RL-circuit connected in parallel to it, consisting of series-connected resistance R2 and inductance L2, as well as the capacitance C2 connected in parallel to them. Shown in figb variant of the frequency-selective structure is not the only possible. In particular, RC or RLC chains of various structures can be used as a frequency selective structure.

The parameters of the elements R1, L1, C1, R2, L2, C2 can vary for different frequency-selective structures to achieve the desired frequency characteristics of the generator of the present invention and to obtain the desired power spectrum of the generated chaotic signal.

In the generator of FIGS. 2 and 3, the input signal is amplified in the first amplifier 1 operating in the small-signal amplification mode and filtered by the first frequency-selective structure 6. The filtered signal is fed to the input of the second amplifier 2 operating in the non-linear signal amplification mode. The signal from the output of the second amplifier 2 is again filtered using the second frequency-selective structure 7, and then it is limited in the third amplifier 3 operating in the signal limiting mode. The signal limited in the third amplifier 3 is filtered using the third frequency-selective structure 8. Then, part of this signal is branched off to load 5 using the frequency-selective coupler 4. The remaining part of the signal after the branch is again fed to the input of the first amplifier 1, and the procedure is repeated.

Chaotic oscillations in such a generator are realized by selecting the values of the parameters of the elements used. On figa shows an example of the implementation of the received signal, and figb presents the power spectrum of this signal for one of the typical chaotic modes of such a generator. The envelope shape of this power spectrum is determined by the characteristics of specific frequency-selective structures 6, 7 and 8.

Figure 5 shows a block diagram of a more complex structure of the generator of the present invention. In this block diagram, in parallel with the chain of the first to third amplification stages 1-3 connected in series, another chain of the fourth to sixth amplified stages 11-13 connected in series is added, the mode of each of which is similar to the corresponding mode of the amplification stages 1-3. There may be several such chains. The outputs of the last amplification stages 3, 13 of all the chains are connected to the inputs of the adder 10, the output of which is connected to the input of the first frequency-selective coupler 4, corresponding to the coupler 4 in Figs. 1 and 2. A part of the signal not supplied to the load 5 is fed to the second frequency -selective coupler 9, which divides this part into components by the number of parallel circuits and supplies the inputs of the first amplifying stages 1, 11. Thanks to this inclusion, the spectrum of the generated frequencies is expanded and the of affection (unevenness) of the spectrum.

In the particular case of frequency-selective structures 6-8 and frequency-selective couplers 4, 9 can be made in the form of microstrip lines. An example of such an embodiment of the present invention is shown in Fig.6.

The generator of FIG. 6 consists of three microcircuit amplifiers 1-3, connected in series and closed in a ring circuit through a microstrip coupler 4. The latter branches most of the signal into the load, and sends the remainder to the input of the first amplifier 1. The main waveguide structure of the generator of FIG. .6 is a 50 ohm microstrip line. The segments of microstrip lines connecting the microcircuit amplifiers are microwave resonators and play the role of frequency-selective structures 6-8. As microcircuit amplifiers, standard industrially produced amplifying elements are used, which are matched to the input and output of 50 Ohms.

An analysis of the currents flowing through these amplifiers indicates that the first (in the direction of signal propagation in the ring circuit) amplifier 1 operates in a small signal amplification mode, the second amplifier 2 operates in a nonlinear signal amplification mode, and the third amplifier 3 operates in a limiting mode signal, thereby playing the role of the main nonlinear element of the generator of Fig.6.

The range and band of the generated frequencies fully correspond to the similar parameters of the amplifiers used. So, if the working band of the microcircuit amplifier according to the passport data corresponds to 100-5500 MHz, then it is precisely it that occupies the power spectrum of the output signal of this generator. One of the typical power spectra of the output signal in the mode of generating chaotic oscillations for the case of using amplifiers of the type MSA-0986 is shown in Fig.7.

The coupler function is performed by a balanced microstrip element, calculated on the average frequency of the generated frequency range. This coupler is turned on in such a way that about 90% of the signal power at the output of the third microcircuit amplifier enters the load.

The models of the generators were implemented using microstrip technology. As the substrate, we used materials 1 mm thick with a dielectric constant ε = 2.8 and ε = 10.0.

The following microcircuit amplifiers were used in the mock-ups:

1. MSA-0986 (a low-power silicon bipolar amplifier from Agilent Technologies) with a working frequency band of 100-5500 MHz at a level of 3 dB; the gain and maximum output power, measured at a frequency of 1000 MHz, are respectively 7.3 dB and +10.5 dBm; operating voltage + 7.8 V; current 35 mA.

2. SGA-6286 (SiGe technology, Sirenza Microwaves) with a frequency band of 0-5.5 GHz; gain and maximum output power, measured at a frequency of 1.95 GHz, are respectively 12.4 dB and +17.8 dBm; operating voltage - 4 V; current 75 mA.

In both cases, the power spectrum of the output chaotic signal extends from hundreds of MHz to 5000-5500 MHz (see Fig.7). The signal power in the load was 10-12 mW when using MSA-0986 and 12-15 mW for 80A-6286.

In the process of operation of the generator according to any of the above schemes, the method of generating a broadband microwave chaotic signal of the present invention is implemented as follows.

Let us consider a single passage, for example, by a harmonic signal of a chain of three amplifier stages 1-3 operating in the modes of small signal amplification, nonlinear amplification, and limitation, respectively. If the input signal level is low, then the first amplifier stage 1 amplifies it almost linearly or, in other words, without distorting the waveform. The harmonic signal amplified by the first amplifier stage 1 relative to the next (second) amplifier stage 2 falls into the region of its nonlinear amplification, which leads to the appearance of waveform distortions at the output of the second amplifier stage 2 and is reflected in the appearance of harmonics (subharmonics) in the spectral characteristic signal. Finally, the last stage is the passage of the signal with harmonics through the third amplifier stage 3. The amplitude of the signal at the output of the second amplifier stage 2 is such that the third amplifier stage 3 can no longer amplify it, working in the signal limiting mode (i.e., in saturation mode) . The signal acquires even stronger form distortions, enriching the spectral characteristic with the appearance of additional frequency components.

If we further weaken this signal, returning it to the low signal level described above at the input of the amplification chain, and repeat the process under consideration (amplification - limitation - attenuation), then taking into account the signal delays in amplification stages that always exist in practice and the effect of frequency pulling in Microwave path, the influence of noise, etc., the signal becomes noise-like in shape, and its spectral characteristic becomes solid.

The described function of the signal attenuator in the method of the present invention is performed by a coupler 4, which branches out most of the signal to load 5 and directs the remainder to the input of the first amplifier stage 1.

The presence of frequency-selective structures between amplifying cascades, as well as the use of a frequency-selective coupler, does not violate the general concept of generation, but helps to form a chaotic signal with specified spectral characteristics. The frequency band of the generated chaotic signal is determined by the corresponding working gain band used in the amplification stages circuit.

Since modern microwave amplification assemblies have a working band from almost 0 to several GHz, the present invention makes it possible to realize broadband and ultrawideband chaotic signals with a small spectral non-uniformity without an additional generator of periodic oscillations with controlled amplitude and frequency.

Claims (10)

1. A method of generating broadband microwave chaotic signals, which consists in the fact that carry out sequential amplification of the signal by at least two amplifier stages; limit the signal after amplification; applying a signal after limiting to the first of said amplification stages, characterized in that said signal amplification is carried out by said amplification stages so that the first of them operates in a small signal amplification mode, and the second in a non-linear signal amplification mode; said signal limiting is carried out in a third amplification stage, which operates in a signal limiting mode and forms, together with the first and second amplification stages, an amplification path; branch part of the signal after limiting the load; the aforementioned first of the amplification stages serves the remainder of the signal after the branch. 2. The method according to claim 1, characterized in that the said signal branch is performed using a frequency selective coupler. 3. The method according to claim 1, characterized in that the signal is passed after at least one of the aforementioned amplification stages through an appropriate frequency-selective structure having a predetermined frequency response. 4. The method according to claim 1, characterized in that the gain of said amplification stages is changed according to predetermined laws, whereby the parameters of the generated signals are controlled. 5. The method according to claim 1, characterized in that the parameters of the mentioned frequency-selective structures are changed according to predetermined laws, whereby the parameters of the generated signals are controlled. 6. The method according to claim 1, characterized in that said series amplification and signal limitation in said amplification path is repeated in at least one additional amplification path parallel to said amplification path, and the signals of all parallel amplification paths are summed, after which the aforementioned branching the signal into the load. 7. A broadband microwave chaotic signal generator comprising first and second amplification stages and a restriction stage connected in series, the output of which is connected to the input of the first amplification stage, characterized in that said first amplification stage is designed to operate in a mode of amplification of small signals, said second amplification stage is designed to operate in non-linear amplification of signals, and said limiting stage is made in the form of a third amplifying stage, designed to I work in the limiting mode, while the output of the said third amplifier stage is connected to the said input of the first amplifier stage through a microstrip signal coupler to the load. 8. The generator according to claim 7, characterized in that at least one of the aforementioned series connections of the amplifier stages and the connection of the third amplifier stage with a signal coupler to the load is made through the corresponding microstrip frequency-selective structure. 9. The generator according to claim 8, characterized in that the aforementioned amplifier stages and (or) frequency-selective structures are made adjustable to provide the ability to control the parameters of the generated signal. 10. The generator according to claim 7, characterized in that at least one additional amplifier path is introduced into it, including amplifier stages similar to said amplifier stages, while the inputs of all first amplifier stages are connected to the corresponding outputs of the said signal coupler to the load and the outputs of all third amplifying stages are connected to the inputs of the adder, the output of which is connected to the input of the said signal coupler to the load.

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