RU183781U1 - DEVICE FOR DOPPLER FREQUENCY DEFINITION DETERMINATION DETERMINATION BY THE INFORMATION PHASOMANIPULATED SIGNAL BY APPROXIMATION OF PHASE DEFLECTION - Google Patents

Abstract

The utility model relates to the field of electro-radio engineering, namely to radio communication technology, and can be used in single-frequency data transmission systems, as well as in radio sounding systems for measuring the Doppler shift of the carrier frequency of a signal in information-measuring devices without a priori information about the modulating message. The device comprises a phase detector, a key, a memory unit, an adder, a counter, a phase converter, a first multiplier, a second multiplier, a first accumulator adder, a second accumulator adder, a divider, and a coefficient multiplier.

The technical result in the implementation of the claimed solution is the determination of the Doppler frequency offset by the information (i.e., unknown) phase-shift signal with absolute, relative or phase-difference phase shift keying. 1 ill.

Description

The utility model relates to the field of electro-radio engineering, namely to radio communication technology, and can be used in single-frequency data transmission systems, as well as in radio sounding systems for measuring the Doppler shift of the carrier frequency of a signal in information-measuring devices without a priori information about the modulating message.

As is known, the Doppler shift of the carrier frequency of the signal can be caused by the movement of the source and / or receiver, as well as the movement of the surface reflecting the radio signal (for example, KB radio communication is characterized by a change in the height of the ionosphere layer). In particular, the presence of Doppler frequency shift leads to a significant decrease in the noise immunity of data transmission systems.

To increase the efficiency of modern radio communication systems, it is necessary to constantly know the propagation conditions between the transmitting and receiving sides at a given frequency at a particular moment in time. For this, testing (probing) of the channel is carried out in order to obtain estimates of the channel parameters, such as signal-to-noise ratio (SNR), the presence of multipath, Doppler frequency shift, and others. For such testing, the vast majority of systems use various test signals.

In particular, linear frequency modulation (LFM) signals are often used to measure Doppler frequency shift. For example, in RF patent No. 2316898 [RU A method for simultaneously measuring the frequency dependences of the Doppler frequency offset and propagation time of short-wave signals in the ionospheric radio line, 02/10/2008], or in the method for estimating Doppler bias described in [Sharif BS, Neashan J., Hinton OR, Adams ae A computationally efficient doppler compensation system for underwater acoustic communication // Oceanic Engineering, IEEE Journal of. - 2000. Vol. 25, No. 1. - P. 52-61].

Methods are also known in which a narrow-band tonal (harmonic) signal is emitted at a single carrier frequency or modulated by a pseudo-random M-sequence to estimate the Doppler shift. For the case of using a harmonic signal, the received signal is converted using the Fourier transform, a spectrum is obtained, a signal is selected with a maximum frequency that is correlated with the carrier frequency of the emitted frequency to determine the Doppler scaling factor, and then the magnitude of the Doppler shift is determined [Oppenheim E. Application of digital signal processing. - M .: Mir, 1980, 553 s]. When using modulated signals, various correlation methods are usually used, for example, [Johnson M., Freitag L., Stojanovic M. Improved Doppler tracking and correction for underwater acoustic communications // in Proc. ICASSP '97, Munich, Germany, Apr. 1997, P. 575-578].

The disadvantage of these methods is that special test signals are used to evaluate the Doppler frequency shift, which reduces the information speed.

Known patent No. 4706286 [US Sturza; Mark A., Method and circuit for extraction of Doppler information from a pseudonoise modulated carrier, November 10, 1987], based on a second-order nonlinear operation and adopted as a prototype. The method described in this patent involves: mixing the received signal with the local oscillation frequency at least two times less than the estimated frequency of the Doppler shift, as well as mixing the received signal with the local oscillation frequency at least twice the expected frequency of the Doppler shift, filtering the low-frequency components, mixing the resulting low-frequency components and subsequent low-pass filtering, after which, using the Fourier transform, an estimate of the Doppler frequency shift is obtained. A device that implements this method is also described in patent No. 4706286 [US Sturza; Mark A., Method and circuit for extraction of Doppler information from a pseudonoise modulated carrier, November 10, 1987] and contains a series-connected input bandpass filter, an amplifier whose output is connected to the first input of the first and second mixer (multiplier), to the second input of which the first and second local oscillators are connected, whose frequencies are at least two times, respectively, less and more than the expected Doppler shift frequency, the outputs of the mixers are connected to the first and second low-pass filters whose outputs are connected respectively to the first and second input m third mixer, which output is connected to the input of the third low pass filter whose output is connected to the processor performing the Fourier transform, after which the result of analyzing the obtained spectrum obtained estimate of the Doppler frequency shift.

The disadvantage of the prototype is that this described method and device gives a serious error in determining the Doppler frequency shift for signals with phase shift keying, the symbol duration of which does not fit an integer number of periods (for example, for aviation modems of the ARTNC 635 standard). In addition, the accuracy of the resulting estimate is directly related to the selected sampling rate and the number of samples at which the Fourier transform is calculated and, in a number of existing data transmission systems (for example, in KB and VHF systems), will also give a significant error.

The aim of the invention is the determination of the Doppler frequency offset by the information phase-manipulated signal.

которое подают на вход преобразователя фазы, осуществляющего операцию This goal is achieved in that the device for determining the Doppler frequency shift by the information phase-manipulated signal by approximating the phase deviation contains a phase detector, the output of which receives the phase value of the next k-th symbol Ф _k , the input of which is the input of the device, and the output is connected to the first input of the key and the second input of the adder, while the second input of the key is connected to the output of the counter, while upon receipt of the number k = 0 from the counter, the key closes from the key output to the input of the memory block and enters phase value F _0, and when k ≠ 0 the switch is open, resulting in the memory unit phase value F ₀ is stored, the output of which is supplied with the sign "minus" to the first input of the adder, the adder output to receive the phase difference value

which is fed to the input of the phase converter performing the operation

выход преобразователя фазы подключен к первому входу первого умножителя, второй вход которого соединен с выходом счетчика, а выход первого умножителя подключен к первому входу первого сумматора накопителя, второй вход которого соединен с выходом счетчика и при k=0 начальное значение первого сумматора накопителя обнуляется, а при поступлении k=К_max, равного максимальному номеру символа информационной последовательности, на которой осуществляется оценка доплеровского смещения частоты, с выхода первого сумматора накопителя на первый вход делителя подают результат суммирования X, при этом выход счетчика также соединен с первым и вторым входами второго умножителя, выход которого соединен с первым входом второго сумматора накопителя, второй вход которого соединен с выходом счетчика и при k=0 начальное значение второго сумматора накопителя обнуляется, а при поступлении k=K_max с выхода второго сумматора накопителя на второй вход делителя подают результат суммирования Y, выход делителя, в котором осуществляют деление X/Y, подключен к входу умножителя на коэффициент, в котором осуществляют умножение на коэффициент

где - длительность символа, F_симв – частота следования символов, в результате получая на выходе умножителя на коэффициент, являющегося выходом устройства, значение доплеровского сдвига частоты.

the output of the phase converter is connected to the first input of the first multiplier, the second input of which is connected to the output of the counter, and the output of the first multiplier is connected to the first input of the first adder of the drive, the second input of which is connected to the output of the counter and when k = 0 the initial value of the first adder of the drive is reset, and upon receipt of k = K _max , equal to the maximum symbol number of the information sequence at which the Doppler frequency offset is evaluated, from the output of the first accumulator adder to the first input the divider serves the result of summing X, while the output of the counter is also connected to the first and second inputs of the second multiplier, the output of which is connected to the first input of the second adder of the drive, the second input of which is connected to the output of the counter and at k = 0 the initial value of the second adder of the drive is reset, and admission k = k _max from the output of the second adder to the second storage divider input is supplied addition result Y, output of the divider, wherein the division is performed X / Y, is connected to the input on the multiplier factor, wherein impl stvlyayut multiplication coefficient

where - the symbol duration, F _Char - symbol repetition frequency, thus obtaining at the output of multiplier by a coefficient which is the output device, the value of Doppler frequency shift.

The block diagram of the proposed device is shown in FIG. 1. It contains a phase detector 1, the input of which is the input of the device, and the output is connected to the first input of the key 2 and the second input of the adder 4. Key 2, the output of which is connected to the input of the memory unit 3, the output of which is connected to the first input of the adder 4, the output which is connected to the input of the phase 6 converter, which is connected to the first input of the first multiplier 7. Counter 5, the output of which is connected to the second input of the key 2, the second input of the first multiplier 7, the first and second inputs of the second multiplier 8, to the second input of the first and second sum drive matrices 9 and 10. The output of the first multiplier 7 is connected to the first input of the first accumulator adder 9, and the output of the second multiplier 8 is connected to the first input of the second accumulator adder 10. The output of the first and second accumulators 9 and 10 are connected, respectively, to the first and second inputs the divider 11, and the output of the divider 11 is connected to the input of the multiplier by a factor of 12, the output of which is the output of the device.

The operation of the device is as follows.

The input signal receives an input signal with absolute, relative or phase difference phase shift keying. Moreover, the signal is informational, i.e. its modulated bit information sequence is not known in advance. The signal, in the General case, may also contain well-known test inserts, while the modulation of these test inserts should also be absolute, relative or phase difference phase shift keying. In the phase detector 1, the absolute value of the phase of the symbol Ф _k is determined, which contains the following components:

where k - symbol number, φ _k - symbol phase value (0, π), ψ - permanent phase offset, Δƒ - value of the Doppler shift frequency, symbol -Duration (thus = 1 / F _Char), ξk - phase error bound with noise.

The duration of the input signal corresponds to an information sequence of length K _{max + 1} characters. Note also that even if, for example, relative phase shift keying is used, i.e. an information symbol is embedded in the phase difference of two adjacent symbols, then the phase value of each symbol also contains the component _{φ k} .

Counter 5 starts counting k = 0, 1, 2, 3, ... K _max . Moreover, when the number k = 0 arrives at the second input of the key 2, then the key 2 closes, as a result of which the phase value Ф ₀ transmitted from the output of the phase detector 1 to the first input of the key 2 comes from the output of the key 2 to the input of the memory unit 3, where it is stored until a new value replaces it. For all other values of k, key 2 is open.

As a result, the first input of adder 4 with a minus sign receives the value of the phase of the zero symbol Ф ₀ , and the second input of adder 4 from the output of the phase detector 1 alternately receives the values of the remaining symbols Ф _k , k = 0, 1, 2, 3, ... K _max . The output of the adder get the values:

In this case, regardless of the type of modulation (absolute, relative, or phase difference phase shift keying) and the type of information sequence transmitted, the values Δϕ _{k, 0} are 0, ± π.

получая значение

Полученное значение фазы подают на первый вход первого умножителя 7, на второй вход которого с выхода счетчика 5 поступает значение к. С выхода первого умножителя 7 на первый вход первого сумматора накопителя 9 поступает значение

При этом на второй вход первого сумматора накопителя 9 с выхода счетчика поступает значение к, и если k=0, то хранящееся (накопленное) значение суммирования приравнивают 0, т.е. Х=0. В сумматоре накопителе 9 осуществляют операцию

Если на второй вход сумматора накопителя 9 поступает значение k=K_mwi, то с выхода первого сумматора накопителя 9 на первый вход делителя 11 подают результат суммирования X.From the output of the adder 4 to the input of the phase 6 converter, ΔФ _{k, 0} подают

getting value

The obtained phase value is fed to the first input of the first multiplier 7, to the second input of which the output of counter 5 receives the value of k. From the output of the first multiplier 7, the value of the first adder of the drive 9 receives the value

At the same time, the value k arrives at the second input of the first adder of drive 9 from the counter output, and if k = 0, then the stored (accumulated) summation value is equal to 0, i.e. X = 0. In the adder drive 9 carry out the operation

If the value k = K _{mwi is} supplied to the second input of the accumulator 9 adder, then the summation result X is output from the output of the first adder of the accumulator 9 to the first input of the divider 11.

The value k is supplied to the first and second inputs of the second multiplier 8 from the counter output. The value k ^{2 is} output from the output of the second multiplier 8 to the first input of the second adder of the drive 10. In this case, the value k arrives at the second input of the second adder of the drive 10 from the counter output, and if k = 0, then the stored (accumulated) summation value is equal to 0, i.e. 7 = 0. In the adder drive 10 carry out the operation Y-Y + k ² . If the value k = _{Kmak is} supplied to the second input of the accumulator adder 10, then the summation Y is output from the output of the second accumulator adder 10 to the second input of the divider 11.

В результате на выходе умножителяIn the divider 11, XIY is divided. The result is fed to the input of the multiplier by a factor of 12, in which multiplication by a coefficient

As a result, the output of the multiplier

by a factor of 12, which is the output of the device, the value of the Doppler frequency shift is obtained.

The proposed device provides the determination of the Doppler frequency offset by the information (i.e., unknown) phase-shift signal with absolute, relative or phase-difference phase shift keying.

Compared with the prototype, the device requires a significantly smaller number of computational operations, because all operations of multiplication and addition are carried out with separate values, and in the prototype with sample vectors of the input signal and local oscillator signals. In addition, in the inventive device, the accuracy of the resulting estimate of the Doppler frequency shift is higher and practically independent of the selected sampling frequency.

Claims (1)

The device for determining the Doppler frequency shift by the information phase-manipulated signal by approximating the phase deviation contains a phase detector, the output of which receives the phase value of the next kth symbol Ф _k , the input of which is the input of the device, and the output is connected to the first input of the key and the second input of the adder, in this case, the second key input is connected to the output of the counter; in this case, when the number k = 0 is received from the counter, the key is closed and the phase value Ф ₀ arrives at the input of the memory block, and for k ≠ 0, the latch is open, as a result, the value of the phase Ф ₀ is stored in the memory block, from the output of which it is supplied with a minus sign to the first input of the adder, the output of the adder receives the phase difference value ΔФ _{k, 0} = Ф _k -Ф ₀ , which is fed to the input of the phase converter performing the atan2 operation (sin (ΔФ _{k, 0} ), cos (ΔФ _{k, 0} )), the output of the phase converter is connected to the first input of the first multiplier, the second input of which is connected to the output of the counter, and the output of the first multiplier is connected to the first the input of the first adder drive, the second input of which is connected to the output ohm meter and when k = 0, the initial value of the first accumulator adder is reset and when entering k = K _max, equal to the maximum number of the information sequence symbol in which the evaluation of the Doppler frequency shift, the output of the first accumulator adder by the first divider is supplied addition result input X while the output of the counter is also connected to the first and second inputs of the second multiplier, the output of which is connected to the first input of the second adder of the drive, the second input of which is connected to the output of the counter a, and when k = 0, the initial value of the second adder is reset drive and admission k = K _max from the output of the second adder accumulator to the second divider input is supplied addition result Y, output of the divider, which is performed X / Y division, connected to the multiplier input the factor in which the multiplication by the factor 1 / (2πT _Char) = F _Char / (2π), where T _Char - symbol duration, F _Char - frequency symbol repetition, thus obtaining at the output of multiplier by a coefficient which is the output device, Doppler shift value ha frequency.

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