RU2775644C1 - Method for complexing signals of elements of a phased antenna array into a general analogue-digital conversion trail - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to the field of radio engineering. This effect is achieved by the fact that the phase keying of the signals of the elements of the antenna array is carried out by individual binary sequences orthogonal on the accumulation interval in the correlator, while the structure of the keying sequence is allowed to mismatch with the structure of the received signal and the symbol repetition rate in the keying sequence is reduced relative to the received signal. Signal separation is performed by multiplying the digital composite signal by the same individual sequences, followed by correlation processing.

EFFECT: multiplexing the signals of elements of a phased antenna array (PAA), providing the possibility of simultaneous reception of several different signals on one PAA.

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Description

The invention relates to the field of radio engineering and can be used in communication, radar and navigation systems to improve the energy, weight, size and cost characteristics of phased antenna arrays with digital beamforming.

Improving the noise immunity and accuracy of radar stations and satellite navigation equipment of consumers, as well as the throughput of radio communication systems, is achieved by using antenna terminals based on phased antenna arrays (PAR). Widespread use has been made of digital beamforming HEADLIGHTS, which allow you to simultaneously create and independently control several main lobes of the radiation pattern. A well-known disadvantage of such systems is the need to use N paths of analog-to-digital conversion (ADC) in receivers with phased array, as well as N paths for frequency conversion and signal amplification, where N is the number of elements of the phased array web, see, for example, [1] - Digital antenna gratings and high-speed analog-to-digital converters / E.M. Dobychin, Yu.V. Koltsov // M: MAI, 2012. - p. 168.

This circumstance significantly increases the power consumption and cost of the antenna array and makes the task of reducing the number of electronic components used in the antenna topical. One of the ways to solve the problem is to compress L signals of elementary PAR emitters into one analog-to-digital conversion path with subsequent extraction of L initial signals.

Among the signals used in radio navigation systems, signals with direct spread of the spectrum by modulating the carrier with noise-like signals are common ([2] - GLONASS. Principles of construction and operation / Edited by A.I. Perov, V.N. Kharisov. Ed. 4- e, revised and additional // M: Radiotekhnika, 2010. 800 p.).

A known method of receiving radio navigation signals using HEADLIGHTS without signal compression in the ADC path ([3] - Digital antenna arrays in mobile satellite communications / V.I. Slyusar // First Mile, 2008. No 4 - p. 10-15). In the circuit that implements this method and is shown in Fig. 1, an electromagnetic wave is incident on the receiving elements 1 _{1 ... 4 of} the antenna array. High-frequency signals are formed at their output, which are fed to frequency conversion devices 2 _{1 ... 4} , in which frequency selection, signal amplification, signal spectrum transfer to an intermediate frequency (IF) are carried out. The signals to the IF are fed to the input of analog-to-digital converters 3 _{1 ... 4} , from the output of which digital samples of the IF signals are fed to the phase shifters 4 _{1 ... 4} and the adder 5 from the composition of the beam-forming system 6. The signal of the beam-forming system 6 is fed to the input of the correlation processing unit 7, connected to the input of the mixer 8, the second input of which is fed digital samples of the intermediate frequency signal from the IF generator 9. With an appropriate choice of the initial phase and frequency of the IF generator 9, at the output of the mixer 8, samples of a mixture of a periodic pseudo-random sequence (RRP) of pulses of positive and negative polarity ( "chips") A(t _k ) and noise n(t _a ), where t _k is a discrete time, which are fed to the input of the correlator 10. The local replica of the PSP A(t _k - τ) delayed relative to the input signal by an unknown value τ. At the output of the correlator 10, the accumulation results are formed

which are used in the tracking circuit for the delay 12 to determine the time t ₀ - the moment of arrival of the signal at the input of the receiver. The number of samples K in the correlator 10 is chosen so as to simultaneously process an integer S of the SRP periods:

t _K -t ₀ \u003d S⋅M⋅T _h ,

where M is the number of chips in one PSS period,

T _h - chip duration,

M⋅T _h is the length of one period of the PSP.

A known method of multiplexing the signals of L antenna elements into one ADC receiver (see patent [4] - KR 101327163 (B1), H04B 7/04, H04J 11/00, publ. 06.11.2013.). In the circuit that implements this method and is shown in Fig. 2 multiplexing of signals into one path of the ADC receiver is carried out by serial connection using the switch 13 of the input of the ADC 3 to the outputs L of the frequency conversion devices 2 _1...4 (in Fig. 2 L=4). The disadvantage of this method is the need to use an ADC with a conversion time L times less than in the circuit described earlier for the receiver (Fig. 1). This significantly tightens the requirements for the sampling frequency and bandwidth of the ADC, the limiting realizable value of which limits the achievable value of L.

The method selected as a prototype as the closest in terms of the totality of features to the invention is described in the patent [5] - US 9966989 (B2), H04B 1/707, H04B 7/06, H04B 7/08, H04J 13/00, H04J 13 /10, publ. 05/08/2018. The operation of the device that implements this method on the example of an eight-element antenna array is explained using the functional diagram shown in Fig. 3. Known prototype method is as follows. The output signals of the receiving elements 1 _{1...8 of} the antenna array are fed to the input of the modulators 14 _1...8 , where they are phase-shifted with M-sequences of the same structure as the received signal, but delayed in time relative to the received signal by several to the second inputs of modulators 14 _1…8 from PSP generators 1 _1…8 . The signals from the outputs of the modulators 14 _1...8 turn out to be M-sequences of the same structure, but additionally shifted in time relative to each other by values that are multiples of the duration of the SRP chip, i.e. much more than before modulation. Manipulated in this way, the signals of the antenna elements are quasi-orthogonal to each other. These signals are combined into a composite signal using adder 5, which is fed to the input of a common frequency conversion device 2, from the output of which the IF signal is fed to ADC 3. Then, the digitized composite signal is correlated by correlation processing units 7 _{1 ... 8} in order to separate the signals, the separated signals are fed to the input of the beam-forming system 6 to form the required radiation pattern of the HEADLIGHTS.

The disadvantages of the prototype method are:

- the impossibility of simultaneous reception of two or more signals with different structures; for one of the signals, the requirement that the structure of the M-sequence of the received signal and the signals of the PSP generators 11 _{1 ... 8} match will be violated.

- the need to modulate the signals of the antenna elements with pulses following the modulation frequency of the received signal. In the case of broadband systems, the duration of one symbol (chip) T _h of the modulating sequence of the received signal can be 1-10 ns, which significantly complicates the hardware implementation of the proposed method.

The technical result to which the invention is directed is to reduce the requirements for the speed of modulators in a phased antenna array with digital beamforming relative to the prototype and to provide the possibility of simultaneous reception of several different signals on one headlight.

The essence of the invention is as follows. In the method of compressing the signals of the HEADLIGHTS elements into a common path of analog-to-digital conversion, before the formation of a composite signal, phase manipulation of the output signals s _i (f) of the HEADLIGHTS antenna elements (i∈[1; L], L is the number of AEs) is carried out, unlike the prototype, individual binary sequences P _i (t) of voltage pulses of positive and negative polarity of the same amplitude, orthogonal in the interval of signal accumulation in correlators, and to extract the signal s _j (t) (j∈[1; L]), the digital composite signal is multiplied by those the same individual sequences P _j (t) with subsequent correlation processing, while the technical result is achieved by allowing a mismatch between the structure of the manipulating sequence and the structure of the received signal and reducing the symbol rate in the manipulating sequence relative to the received signal.

Brief description of the drawings.

On FIG. 1 shows a typical functional diagram of a device that implements the reception of a radio navigation signal based on the phased array without signal compression.

On FIG. 2 shows a typical functional diagram of a device that implements a known method for receiving a radio navigation signal with multiplexing the signals of the HEADLIGHTS elements into a common analog-to-digital conversion path.

On FIG. 3 shows a functional diagram of a device that implements the known prototype method using an eight-element antenna array as an example.

On FIG. 4 shows a functional diagram of a device that implements the claimed method of compressing the signals of phased antenna array elements into a common analog-to-digital conversion path using an eight-element antenna array as an example.

A detailed description of the invention and its feasibility are illustrated in FIG. 4 is a functional diagram of a device that implements the proposed method in one of the possible embodiments using an eight-element antenna array as an example.

The electromagnetic wave incident on the HEADLIGHT with the help of antenna array elements 1 _{1 ... 8} is converted into high-frequency electrical signals, which are then manipulated in modulators 14 _{1 ... 8} by sequences P ₁ (t) ... P ₈ (t) of voltage pulses of positive and negative polarity of the same amplitude, generated using generators PSP 11 _1...8 , and the duration of one pulse in the sequence may be greater than the duration of the chip PSP T _h . The sequences P _i (t) are selected according to the criterion of orthogonality on the accumulation interval T _K in the correlator 10:

The manipulated high-frequency signals are combined into a composite signal using adder 5, which is amplified and transferred to a convenient intermediate frequency using frequency converter 2, and digitized in ADC 3. From the digitized composite signal at an intermediate frequency, the signals of the antenna array elements transferred to an intermediate frequency are restored, by manipulating copies of the composite signal with the help of modulators 14 _9...16 pulse sequences P ₁ (t)...P ₈ (t), generated using the generators PSP 11 _9...16 . The restored signals are fed to the appropriate inputs of the beamforming system 6 to form the required radiation pattern of the HEADLIGHTS. The recovered signals contain the by-products of signal compression into a common analog-to-digital path. To suppress unwanted components and extract the signal from the noise, the correlation processing of the signal of the beam-forming system 6 is carried out by the correlation processing unit 7.

Let us trace the passage of signals from the antenna elements through the device in Fig. 4. Let the signal received by the i-th antenna element have the form

where A(t) is a modulating signal with binary phase shift keying,

ω _RF - circular frequency of the radio signal carrier,

t _i - signal delay at the output of the i-th antenna element relative to the first antenna element, t ₁ =0.

Assuming that the PAR canvas is sufficiently compact (so that t _i <<Т _h for i=1…L), we can write an approximate relation

The accumulation interval T _K of the correlator is chosen equal to or a multiple of the repetition period of the radio signal envelope:

and the envelope itself is an arbitrary M-sequence.

The signals of the generators PSP 11 _1...8 represent a set of orthogonal on the interval T _K sequences P _i (t) pulses of the same amplitude of positive and negative polarity (for example, the Walsh function or M-sequence), and, unlike the prototype, the duration of the "chips" sequences P _i (t) is much greater than the duration of the chip sequence A(t). In this case, the composite signal S _RF (t) at the output of the adder 5 has the form

Due to the fact that the duration of the “chips” of the sequences P _i (t) is much greater than the duration of the sequence chip A(t), the spectrum width of the composite signal is equal to the spectrum width of the original radio signal. Similarly, the composite signal of the intermediate frequency at the output of ADC 3, up to a multiplier, has the form

The signals s _IFj (t) at the output of modulators 14 _{9 ... 16} have the form

In beamforming system 6, each signal is multiplied by a weighting factor B _j, , the carrier is delayed by t _j =-t _i , and then all signals are summed:

The first term is the useful output signal of the beamforming system 6, the second term is a by-product of signal compression into a common analog-to-digital path. The signal from the output of the beamforming system 6 is fed to the correlation processing unit 7. Due to the linearity of the correlator, we will further consider only the passage of the side signal from the output of the beamforming system 6:

where it is taken into account that A ² (t)=const.

The considered shows that the claimed method of compressing the signals of the elements of a phased antenna array into a common path of analog-to-digital conversion is feasible and provides the achievement of a technical result, which consists in reducing the requirements for the speed of modulators in the phased array with digital beamforming and providing the possibility of simultaneous reception on one phased array of several different signals.

Sources of information

1. Digital antenna arrays and high-speed analog-to-digital converters / E.M. Dobychin, Yu.V. Koltsov // M: MAI, 2012. - p. 168.

2. GLONASS. Principles of construction and functioning / Ed. A.I. Perov, V.N. Kharisov. Ed. 4th, revised. and additional // M: Radio engineering, 2010. 800 p.

3. Digital antenna arrays in mobile satellite communications / V.I. Slusar // First Mile, 2008. No 4 - p. 10-15.

4. KR 101327163 (B1), H04B 7/04, H04J 11/00, publ. 11/06/2013.

5. US 9966989 (B2), H04B 1/707, H04B 7/06, H04B 7/08, H04J 13/00, H04J 13/10, publ. 05/08/2018.

Claims (1)

A method for compressing the signals of phased antenna array elements into a common analog-to-digital conversion path, in which the signals received using the antenna array elements are phase-shift keyed with binary sequences, the keyed signals are combined into a composite signal, transferred to a convenient intermediate frequency, at which analog-to-digital conversion and extraction of the original signals from the composite signal, form a given radiation pattern, characterized in that the phase keying of the signals of the elements of the antenna array is performed by individual binary sequences orthogonal over the accumulation interval in the correlator, while the structure of the keying sequence is allowed to mismatch with the structure of the received signal and the frequency is reduced symbols in the keying sequence relative to the received signal, and signal separation is performed by multiplying the digital composite signal by the same individual sequences with subsequent correlation processing.

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