RU2234190C2 - Method and device for direct on-air data transmission and reception - Google Patents

Abstract

FIELD: communications engineering.

SUBSTANCE: proposed method and device make use of radio-relaying communication systems of space lines. Signal being transmitted is excited in opposite polarizations and differential signal is received from antennas. The latter are connected in parallel and in series.

EFFECT: enhanced noise immunity.

3 cl, 4 dwg

Description

The invention relates to the field of radio communications and radar and can be used in wireless information communications of both narrowband and broadband communication systems without changing existing standards, in television, in radar, including subsurface, in the precise guidance of controlled objects, in global navigation systems, in space communications and management.

The control of interference in wireless communication systems is crucial to increase the range of its use. In the practice of radio communication, there are several options for increasing the communication range - increasing the power of the transmitted signal, increasing the sensitivity of reception and distribution of the signal in a wide band. The increase in transmit power is usually limited by the situation (for example, the allowable weight of the transmitter in satellite communications) or by the communication method (for example, mobile communication, where the increase in power is limited by the user's security requirement). The increase in receiver sensitivity is limited by the rms interference power.

Until the last quarter of the last century, narrow-band communication was practically the main type of ether communication. It is characterized by low noise immunity, and a sufficiently powerful interference of natural or artificial origin could damage the receiving device (PU), and even relatively small interference in the working frequency band led to the loss of information.

A known method of protection against impulse noise of the receiving path (RU 2153767, CL ⁷ N 04 V 1/10, N 04 Q 1/10, 03/17/98). The method is carried out by closing the path for the duration of exposure to impulse noise, thereby protecting the PU from failure. In fact, it is not interference that is suppressed, but the channel for the duration of the interference. In this case, part of the information is lost, and communication is ineffective during a significant development of interference, for example, when passing through a thunderstorm front or in a region of high rock tension immediately before the main fault in the center of the earthquake.

A significant part of the problems of combating interference was solved by the method of a broadband communication system, the noise immunity reserve of which is provided by the base of the noise-like signal used (pseudo-random sequence duration). However, in the context of the growing number of operating wireless communication systems that has been observed over the past decade, with the general increase in the energy saturation of the regions of human activity, situations arise when the level of interference received at the input of a broadband communication system (SSS) exceeds the dynamic range of the receiving device.

A similar situation is possible in the case of targeted suppression of the existing communication system by powerful narrow-band interference, since it is the narrow-band interference that is most easily generated by the jammer. In this case, the input microwave stages of the receiving device, namely the input amplifier and mixer, go into non-linear operation. Distortions of the useful noise-like signal resulting from non-linear transformations in the input stages of the receiving device cannot be compensated by subsequent digital processing, since the nature of such distortions is difficult to predict.

Known broadband communication systems or systems using noise-like signals (SHPS) for encoding information [L. Varakin Communication systems with noise-like signals. - M .: Radio and communications, 1985. - 384 p.]. One of the most important advantages of SHSS, which ensured their rapid development, is its high stability with respect to a wide class of interference, both of artificial and natural origin. The noise immunity of the HSS is determined by the ratio of signal power and interference power at the output of a matched filter (correlator):

where R _S and R _P - signal power and interference power at the input of the receiving device;

B = FT - the base of the used ShPS.

The above ratio means that for fixed values of P _C and P _P at the input of the HSS receiving device, the noise immunity q at the output of the PU can be increased only by increasing the base of the noise-like signal used.

A known method of correlation processing of broadband signals (RU 2153701, CL ⁷ G 06 G 7/19, H 04 B 1/10, 04.16.1998), consisting in the selection of interference by multiplying the input mixture of the interference and the useful signal with a reference broadband signal, synchronous with a useful broadband signal, and further notching the received signal.

The method provides a way out of the real-time transmission of the signal by delaying it for a time longer than the duration of the noise-like signal, which, when the base station is heavily loaded, leads to a limitation of the number of simultaneous servicing of subscribers and a decrease in the information transfer rate. In addition, the processing channel is complicated due to the use of several multipliers, signal subtractors, bandpass filters. And, most importantly, the application of the method is effective only in case of not overloading the input stages - amplifiers and mixers.

The closest to the essence and adopted as a prototype is the suppression method used to protect the ShSS from interference, the level of which exceeds the allowable margin of noise immunity provided by the base [Milstein LB Interference suppression methods in radio systems with broadband signals. - TIIER. -1988. - T. 76, No. 6. - S. 19-36]. The method consists in compensating for interference in the control unit by creating a copy of it and then subtracting the created copy of the interference from the input signal. At the same time, it is believed that the input microwave superficial (microwave) stages of the control unit are not overloaded, that is, they transform the input mixture of the useful signal, noise and interference linearly, without introducing significant distortions into the received signal.

However, in case of overloading the input stages of the control unit, signal distortion by the input microwave stages does not allow creating a copy of the interference, and the loss of information unique to the user can be fatal.

The proposed method allows you to protect from interference any on-air communication system or radar system, including subsurface sounding, regardless of the type of modulation and the used frequency band due to the fact that they excite and receive radio signals with polarized antennas, and receive a polarized radio signal by subtracting the signal of an antenna of one polarization from an antenna signal of opposite polarization. It is possible to transmit information when the antennas of opposite polarization are excited by signals in antiphase, and directional transmission-reception of information with protection against interception, when antennas of the same polarization are aligned coaxially to the transmitter-receiver at the same distance, and the excited signal is divided into fragments, excited in one antenna signal containing a sequence of odd fragments while maintaining the duration of the length of the even fragments, and, after the duration of the first fragment, excite in n rotivophase signal containing a sequence of even fragments while maintaining the duration time of the odd fragments.

Using the method leads to the effective suppression of almost all types of interference, with the exception of thermal noise, which determine the lower limit of the working dynamic range.

A device for researching rocks in a well is known according to the application of France (FR 2613842, class ⁴ G 01 V 3/30, E 21 B 47/04, 10/14/08, containing two synchronous transmitters emitting high-frequency electromagnetic pulses in antiphase, and a receiver whose output is connected to the processing and registration channel. The transmitter antennas are located symmetrically relative to the receiver antenna and in the same plane with it as the parallel to the study surface. When the device is operating in a homogeneous environment, the received total signal from both transmitting antennas is close to zero, which somewhat extends the upper boundary of the dynamic range of the device. When heterogeneity appears on the research profile (well wall), the balance of the difference emitted signal is sharply disturbed and the receiving signal becomes abnormally distinguishable. However, the device does not allow to reduce the lower limit of the dynamic range, determined by the level of interference, and therefore the sensitivity of the device is mediocre.

The known device "Differential radar" (RU 2148842, CL ⁶ G 01 V 3/12, 05/10/2000) is the closest in technical essence. This device contains one transmitting, two receiving vibrating antennas and a processing and recording channel with connecting one receiving antenna to the processing and recording channel through a phase inverter and an adder and the second through an adder, which significantly expands the boundaries of the dynamic range by reducing the total direct received in the processing channel antennas of the emitted signal and reducing the level of common mode interference. In addition, the relative position of the antennas can significantly sharpen the maximum directivity.

However, despite the high noise suppression and improved directivity, the difference signal of such a device is many times lower than the received antenna signal. Therefore, a significant expansion of the dynamic range of the device due to the high noise suppression is not used to the full, and this does not allow to achieve high shooting efficiency.

In addition, the distances between the antennas of the locator and the lengths of their vibrators are determined by the requirement to create a reflector-director antenna system, i.e. Each of the antennas of the locator should be for the other antenna either a director or a reflector. This means that all antennas have slightly different vibrator lengths, that is, they are not identical with respect to the received signal, including interference, which reduces the quality of noise suppression. It is clear that when moving along the profile during sounding, all parameters of this finely tuned locator will change depending on changes in the electrical parameters of the sensing surface located in the near zone of the locator. It will also make it difficult to obtain an accurate measurement procedure.

A phase inverter introduces some delay into one of the receiving channels, which also reduces the identity of the channels and the quality of noise suppression.

The proposed device is devoid of these drawbacks and provides high performance due to the fact that in a device containing one transmitting and two receiving antennas, moreover, all antennas are polarized and receiving antennas have mutually opposite polarization directions, receiving antennas are connected in parallel and in antiphase (parallel sequentially), and their output is connected to the input circuits of the receiving device. Alternatively, there are two transmitting antennas and they have the opposite polarization direction and are connected in the same way as receiving ones in parallel-serial fashion, which doubles the amplitude of the received useful difference signal in comparison with the primary one received by one of the antennas. This effectively suppresses all signals that differ from the useful signal in that they are fed to antennas of different polarization in phase.

The invention is reflected in the drawings, in which Fig. 1 shows time plots of signals from receiving antennas and a difference signal, and Fig. 2 shows the connection of antennas to excite a signal in antiphase or to receive a signal in the subtraction mode.

The essence of the proposed method is illustrated in figure 1

The graph 1 of Fig. 1 shows a useful signal with interference 4, excited in antiphase by two oppositely polarized antennas, received by one of the polarized receiving antennas. In graph 2, a signal with the same interference 4 received by another antenna. On the graph 3 is the difference signal of the antennas at the input of the receiving device.

Figure 2 shows the connection diagram of two antennas 5 and 6 of opposite polarization, for example circular, and a conditional graph of the output-input signal 7-7 ¹ at the input-output of the antennas 5 and 6, connected in parallel-series.

As you know, the polarization of any signal can theoretically be decomposed into two components - into two mutually perpendicular linear polarizations or into two opposite rotation circular components. Both representations are equivalent, but preferably one that matches polarization discrimination of the receiving antennas.

The interference is most likely unpolarized, that is, it contains an equal mixture of both basic circular polarizations. The antenna selects its polarization and filters out another. Therefore, the signal from the interference in two receiving, identical in everything, except for the direction of polarization, in parallel placed and spatially maximally close polarized antennas will be the same, whatever their polarization, either because the antennas are polarized equally, or - although the polarization is opposite interference equally to each polarization.

The useful signal transmitted in antiphase by two antennas of opposite polarization will be received by two antennas of opposite polarization, located as close as possible to each other, exactly as the signal was transmitted - by each antenna in antiphase between each other (1, 2, Fig. 1). The polarization interference components will be perceived by both antennas in a single phase (4, Fig. 1). Since the polarization components of the interference are equal, then when subtracting the signals of the antennas they are mutually destroyed, and the useful signal when subtracting in antiphase will double in amplitude (3, Fig. 1). This improves the signal-to-noise ratio and makes it possible to reliably distinguish a useful difference signal against any background of any intensity of interference, since interference suppression occurs even at the input of microwave input amplifiers and mixers, eliminating overload.

Unlike the prototype, where a copy of the interference is created, followed by subtracting it from the mixture of the useful signal and the interference (thermal noise makes a small contribution compared to the interference), the META COMMUNICATION method allows you to suppress the interference without creating a copy of it, to some extent approximate to the original, that is, without hardware costs even at the input of the electronic components of the receiving device.

It can be noted that if the signals of the antennas are added, that is, to connect the antennas not in parallel-serial, but in parallel, then the total signal will be a noise signal doubled in amplitude without the presence of a useful signal.

It is easy to imagine that if a signal is transmitted by only one polarized antenna, then of the two receiving antennas it will be perceived only by that antenna whose polarization corresponds to the polarization of the transmitted signal. The second receiving antenna, the polarization of which is opposite to the polarization of the signal, will not accept it. But the interference will be perceived by both antennas equally and in a single phase, and when subtracting the antenna signals mutually destroyed. A useful signal will stand out in phase or out of phase without change.

The proposed method allows communication in the case of a requirement of increased security from interception. To do this, it is necessary to assign antennas of the same polarization in the receiver and transmitter coaxially in the direction to the transmitter-receiver at the same distance, and break the excited signal into fragments, and transmit these fragments alternately with one or the other antennas, i.e., excite a signal containing one antenna a sequence of odd fragments with preserving the time duration of the even fragments, and after a time duration of the first fragment to excite in antiphase a signal in another antenna containing ость even fragments with preservation of the time duration of the odd fragments.

Since the antennas of the same polarization at the receiver and the transmitter are aligned towards each other, the distance of the signals of each polarization is the same (it must be remembered that the signal excited by the antenna, for example, left circular polarization, is perceived at the distance of direct vision or in mirror reflection, for example, from plane media interface only by an antenna of the right circular polarization). At the receiving end of the communication line, when the signal of one antenna is subtracted from the signal of the other, it will be like “embedding” a sequence of even fragments into a sequence of odd fragments, making up a single transmitted signal. Intercepting it, not knowing the separation distance between transmitting antennas, which may not be repeated in communication sessions, will be very problematic.

As a result, we obtain a hidden, noise-resistant communication channel, the reception of information in which is possible only if the separation distances of the antennas and the direction of the communication beam, determined on the transmitting side, are known.

The device in figure 2 is suitable for transmitting and receiving signals. In the case of transmitting a signal, the antennas are connected to the output of the terminal power amplifier, and when the signal arrives at the common input 7, a signal is excited in phase - in one antenna and in antiphase - in another. In the reception mode, the signal of one antenna is subtracted from the signal of the other, and the antennas are connected to the input circuits of the receiving device 7 ¹ . The capacitance C, connecting one of the input-output buses with the potential of the “common” point for alternating current, is shown in figure 2, to conditionally show the possibility of phasing the signal.

It should be noted that the proposed method of broadcast transmission-reception of information “Meta COMMUNICATION” is a universal method of suppressing interference, regardless of whether the communication is narrow-band or broad-band. This method can be used with existing types of communication equipment and applies to wireless local area networks, cellular communications (up to global information systems), personal telecommunication systems, regardless of existing standards - it is enough to connect two antennas of opposite polarization, connected in parallel, in series, in accordance with figure 2.

Effective noise reduction will simplify the receive paths. So, we can confidently say that there is no need for barrage, notch and other filters, including adaptive use.

Effective suppression of interference will lead to an increase in the range of reliable communication without increasing transmission power, which, in turn, opens up prospects for the possibility of communication between subscribers of the cellular network directly (if they are within direct visibility), bypassing the relay network and base stations. Yes, and the relay network itself will become more discharged, and the cost of cellular communication - cheaper.

Perhaps a significant reduction in the transmission power of the cell phone.

The theoretical possible dynamic range of cellular communications is 120 dB (from units of microvolts - thermal noise of modern input semiconductor circuits - to units of volts). Almost interference reaches 60 dB. So, in Riga (Latvia), the integral level of interference at the output of a 180-MHz dipole antenna was 600-800 uV at different times of the day. In the United Arab Emirates (Abu Dhabi), the level of interference was already 1000-1500 uV. This can be explained by the proximity of the tropical thunderstorm zone and the region’s high energy density.

An increase in the dynamic range by 20 dB will push the boundary of reliable communication within line of sight by 10 times. Therefore, it is necessary either to increase the transmitting signal by power by 40 dB, i.e. to increase the transmitter power by 100 times, which is unacceptable from the point of view of ergonomics and ecology, or to effectively reduce the effect of interference.

It should be noted that the proposed method is equally effective on all frequency ranges. This is especially important for the shortwave (KB) range, where the method using noise-like signals is not so effective. In the KB range, where the ionosphere plays a decisive role in signal propagation, the narrow-band signal in the usual sense remained the advantage (the width of the spectrum, taking into account the expansion, should not exceed several tens of kilohertz). This means that the speed of information transmission on such a channel cannot be more than kilobits / sec. Otherwise, signal distortions occur due to unequal propagation conditions of the spectral components of the signal. This is due to the fact that the reception of SHS is the collection of a signal in a wide frequency band, and the imbalance of the spectral components of the signal, especially in phase, leads to selective distortion.

The full benefits of noise-like signals (SHPS) are realized in the VHF bands and at higher frequencies. Moreover, the speed of information transfer and the degree of expansion of the spectrum are not limited by anything, except for the difficulties of technical implementation, consisting mainly in limiting the time parameters of electronic devices. The application of the proposed method will reduce the base of SHPS, thereby reducing the requirements for the speed of electronics, or with the same base to increase the allowable number of simultaneous subscribers and the speed of information transfer.

Communication technology using noise-like signals has long been used in radar, where, incidentally, the main advantages of such signals first appeared. In radar, the target detection range is determined by the pulse energy, that is, the product of power by its duration. Increasing the detection range by increasing power has its technical limits. Increasing the pulse duration worsens another parameter - resolution, which determines the ability to detect targets. The resulting contradiction is resolved by the use of complex signals representing a long high-frequency pulse, phase-manipulated according to the law of a pseudo-random sequence of signals.

Using the correlator, the long pulse is compressed in the receiver to the duration of the signal element of the pseudo-random sequence, while the energy increases significantly due to an increase in the number of elements of the pseudo-random sequence, which improves the resolution and increases the detection range.

But for the correlator to work, a copy of the signal is necessary, which creates additional difficulties, since the exact value of the frequency and other parameters of the signal at the receiving end may not be known. In addition, correlation meters are cumbersome in hardware - in the simplest case, this is a multiplier, an integrator, and a threshold device. And to view the entire range (target detection at one azimuth at various distances), the correlators must be multi-channel.

Using the proposed method will allow you to go in the radar to simple sounding signals, greatly simplifying the radar equipment. The same applies to navigation equipment.

For experiments according to the invention, the requirements for the emitted-received ultra-wideband signal were decisive when choosing the type of antenna.

The most ultra-wideband and frequency independent antenna is the log-periodic spiral invented by Ramsey (Ramsey V.H., 1957 IRE Nat Con. Rec 1 (1957), 114). It is constructed using the principle of angles (Ramsey, see above), the principle of complementarity (Dyson JD IRE Trans., AP-7 (1959), 181) and the principle of logarithmic periodicity (Ultra-wideband antennas. Ed. By L. L. Benenson, M .: Mir, 1964).

Numerous experiments have shown that in the frequency band with an overlap of 1:20, the antenna parameters (input impedance, radiation pattern) practically do not change. The radiation pattern of the logospiral antenna has axial symmetry, and with a beam width of 70-80 ° (at a level of 3 dB), such an antenna wins in gain compared to a biconical or dipole 10 dB in the range from 0.2 GHz to 3, 6 GHz. The VSWR of the logospiral antenna did not exceed 1.7 in the entire frequency range. Antenna resistance Z ₀ = 189 Ohms.

Another advantage of a spiral antenna is that it interacts only with a circularly polarized wave of a certain polarization. For example, it emits and receives an electromagnetic wave of only left polarization. In case of specular reflection from a plane interface between two media, the polarization of the reflected wave is the inverse polarization of the incident wave. And the antenna is insensitive to the electromagnetic wave of such a polarization.

The calculations showed that the mismatch of the phase center of the various Fourier harmonics for the selected type of antenna in the operating frequency range can be neglected.

When conducting field experiments with radar equipment for subsurface sounding according to the invention, it was found that the noise suppression efficiency largely depends on the identity of the receiving antennas and in the experiments exceeded 40 dB. Therefore, the manufacture of pairs of antennas must be carried out by printing using a single photo template.

Claims (3)

1. The “META-COMMUNICATION” method of broadcasting information reception and reception, which consists in the use of transmitting antennas in the opposite direction of polarization, exciting them with an information signal, and in reception - in compensating for interference by subtracting the antenna signal of one polarization from the signal of the opposite polarization antenna, characterized in that the transmit and receive antennas are turned on in parallel-sequentially for antiphase excitation in the transmission, and at the reception, the difference information signal received from the antennas is fed to the input one receiver circuit. 2. The method according to claim 1, characterized in that the antennas of the same polarization in the receiver and transmitter are aligned coaxially towards the transmitter and receiver at the same distance. 3. The Meta-COMMUNICATION device of on-air information transmission-reception, containing a block of antennas connected in transmission to the output of the terminal amplifier of the transmitting device, and in reception to the input circuits of the receiving device, characterized in that the antenna block antennas are made with opposite polarization, are aligned and are connected in parallel-series for their antiphase excitation on the transmission and receiving a differential signal at the reception.

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