RU2286648C2 - Parallel short-wave modem - Google Patents

Abstract

FIELD: radio engineering; digital data transfer in short-wave radio station.

SUBSTANCE: novelty is that prior-art parallel short-wave modem having modulator and demodulator is provided with N amplitude keyers newly introduced in modulator, as well as p narrow-band filters, p 90 deg. phase shifters, where p is number of pilot signals in group signal, p amplitude detectors, p reset integrators, and mp quadrature single side-band converters, in demodulator.

EFFECT: ability of retaining serviceable condition of modem on occurrence of fast fading.

1 cl, 13 dwg

Description

The present invention relates to the field of radio engineering and can be used to transmit discrete information in short-wave (KB) radio stations.

The short-wave communication channel, due to the ionospheric propagation of radio waves, is multipath. It can be characterized by two main parameters: the interval of the time delay of the rays Δt _l and the interval of Doppler frequency shifts F _d . When overlapping neighboring information symbols, so-called intersymbol distortions (ISI) occur.

In parallel modems, the elimination of ISI is achieved due to the long duration of the information symbol T _AND ≫Δt _L. In this case, it becomes possible to introduce between the adjacent information symbols a protective interval T _S > Δt _L , within which MSI arise. This interval is excluded from signal processing.

However, at relatively large values of F _D , when F _D T _AND ≥0.01, the influence of fluctuations in frequency (phase) and amplitude begins to appear inside the information symbol (K. Feer. Wireless digital communication. Transl. From English / Ed. B . I. Zhuravleva. - M.: Radio and Communications, 2000, p. 232).

As a result, the probability of errors increases both with coherent demodulation (due to inaccurate tracking of the carrier phase) and with incoherent (due to the destruction of the temporal correlation).

In the work “New studies of a high-speed parallel KB modem” (Marc COUTOLLEAU, Pierre VILA et al., NEW STUDIES ABOUT A HIGH DATA RATE HF PARALLEL MODEM, - IEEE, No. 4, 1998), a coherent parallel modem is proposed with the number of subcarriers equal to 79, of which, in the first transmission frame of three frames, 27 subcarriers are used as pilot. In the next two frames, pilot subcarriers are not used. Pilot components are used to adjust the reference vibrations in adjacent channels.

The time spent on tuning and its implementation in only one frame out of three reduces the accuracy of tracking the phase of the carrier.

Structurally closest to the proposed one can be considered the MS-5 modem (MS-5 Discrete Information Transmission Equipment. / Edited by A.M. Zaezdnoy and Yu.B. Okunev. - M .: Communication, 1970), adopted as a prototype.

The functional diagram of the prototype modem, according to its description, is shown in figa and 1b, where it is indicated:

Figa:

I is the modulator;

1 - block information conversion (BPI);

2 - synchronization unit;

3 ¹ , ... 3 ^N - phase manipulators;

4 - frequency grid generator (RNG);

5 - adder;

6 - submodulator of one sideband (OBP);

7 - carrier frequency generator;

N is the number of channel signals.

Figb:

II - demodulator;

8 - detector OBP;

9 - controlled carrier frequency generator;

10 - block adjustment of the carrier frequency;

11 - frequency grid generator;

12 - block recovery clock frequency (BVTCH).

13 ¹ , ... 13 ⁴ - narrow-band filters;

14 ^1,1 , 14 ^2,1 , ... 14 ^{1, N} , 14 ^{2, N} - multipliers;

15 ^1,1 , 15 ^2,1 , ... 15 ^{1, N} , 15 ^{2, N} - integrators with reset;

16 - decision processing unit;

17 ¹ , 17 ² - keys.

The parallel shortwave prototype modem consists of modulator I and demodulator II. The composition of the modulator I (figa) includes an information conversion unit (BPI) 1, the information input of which is the input of the modulator I, and the synchronization input is connected to the output of the synchronization block 2. N outputs of the BPI 1 are connected to the information inputs of the corresponding phase manipulators 3 ¹ , ... 3 ^N , the reference inputs of which are connected to the corresponding N outputs of the frequency grid generator (RNG) 4. The outputs of each of 3 ¹ , ... 3 ^N phase manipulators are connected to the corresponding N inputs of the adder 5, the output of which through the submodulator is one side field wasps (OBP) 6 is connected to the output of the modulator I, and the reference input of the submodulator OBP 6 is connected to the output of the carrier frequency generator 7.

Demodulator II (figb) contains a serially connected carrier frequency adjustment unit 10, a controlled carrier frequency generator 9 and an OBP 8 detector, the signal input of which is the input of demodulator II and connected to the first input of the carrier frequency adjustment unit 10, the second input of which is connected to the reference the input of the detector OBP 8, the output of which through the first key 17 ^{1 is} connected to the inputs of the first and second narrow-band filters 13 ¹ and 13 ² , and through the second key 17 ^{2 is} connected to the inputs of the third and fourth narrow-band filters 13 ³ and 13 ⁴ . The outputs of the filters 13 ¹ -13 ^{4 are} connected respectively to the first, second, third and fourth inputs of the HVDC 12. The output of the detector OBP 8 is connected to the inputs of each of the N pairs of quadrature correlation information channels, each of which consists of series-connected multipliers 14 ^1,1 , 14 ^2,1 , ... 14 ^{1, N} , 14 ^{2, N} and its corresponding integrator with reset 15 ^1,1 , 15 ^2,1 , ... 15 ^{1, N} , 15 ^{2, N} , outputs 2N of integrators 15 connected to the corresponding 2N inputs of the decision processing unit 15, the output of which is the output of the demodulator II. The control inputs of the integrators with the reset 15 ^1,1 , 15 ^2,1 , ... 15 ^{1, N} , 15 ^{2, N are} connected to the third output of the BVTCH 12, the first and second outputs of which are connected respectively to the control inputs of the keys 17 ¹ and 17 ² . Demodulator II also contains a frequency grid generator 11, N pairs of quadrature outputs of which are connected to the reference inputs of the respective multipliers 14 ^1,1 , 14 ^2,1 , ... 14 ^{1, N} , 14 ^{2, N.}

The operation of modulator I is as follows.

The input stream of binary information symbols is divided into N parallel streams (N is the number of modem channels), encoded and converted in BPI 1 into information signals for phase manipulators 3 ¹ , ... 3 ^N. Channel frequency signals (subcarriers) are supplied to the reference inputs of the phase manipulators 3, which are generated by the frequency grid generator 4. The values of the channel frequencies are determined by the formula (arising from the orthogonality condition on the interval T _and )

where i and K are integers.

Adjacent frequencies differ from each other by an amount

therefore, all channel signals are orthogonal.

In each of the phase manipulators 3, the reference signal (subcarrier) is phase-manipulated by an information signal from the corresponding output of BPI 1. The number of phase gradations can be 2, 4, 8. In adder 5, all phase-manipulated subcarriers are added, forming a group signal with frequency division ( OFDM). The synchronization unit 2 sets the position of the information symbols and the guard interval, as shown in figure 2, from which it follows that the value of the clock interval T _T equal

where T _And - the duration of the information symbol;

T _W - the value of the guard interval.

The guard interval can be formed in the modulator I by eliminating the passage of the output signal of the adder 5 at a time T ₃ , or it can be excluded when processing the signal in the demodulator II. In the prototype device, the second option is used.

Due to the use of relative phase shift keying, RNG 4 synchronization is not required.

In the OBP 6 submodulator, this group signal is transferred to the region of the upper or lower sideband relative to the carrier f ₀ , which is generated by the generator 7.

The demodulator (Fig 1B) works as follows.

,

- частота опорного сигнала, вырабатываемого генератором 9. Если

, все поднесущие получают частотный сдвиг Δf₀. Этот сдвиг компенсируется путем подстройки

с помощью блока 10.The input signal in the detector OBP 8 is converted to the original group signal (as at the output of the adder 5), if

,

- the frequency of the reference signal generated by the generator 9. If

, all subcarriers receive a frequency shift Δf ₀ . This shift is compensated by tuning

using block 10.

Then, every 7th channel signal is processed by the jth pair of N pairs of quadrature correlation information channels (j≤N), including multipliers 14 ^1,1 , 14 ^2,1 , ... 14 ^{1, N} , 14 ^{2, N} and reset integrators 15 ^1,1 , 15 ^2,1 , ... 15 ^{1, N} , 15 ^{2, N.} Pairs of reference signals in the quadrature of the signals are generated by the RNG 11. The amplitudes x _{j, n} and y _{, n of the} signals from the outputs of the integrators with the reset of the 15th jth pair of quadrature channels are used to calculate the phase of the nth information symbol of the jth channel

and two phases measured on adjacent symbols determine the phase difference

which characterizes the value of the information symbol with relative phase modulation. All these calculations are carried out in the decision processing unit 16.

The clock frequency recovery unit 12 serves to determine the start and end moments of information symbols that specify the position of the integration interval at which the channel signals are separated without mutual influence on each other. For the operation of the temporary discriminator included in the HDTV 12, an inter-channel interference signal (MCI) is used, which occurs when the orthogonality of the channel signals is violated due to a shift in the integration interval.

If the integration interval coincides with the information symbol, due to the orthogonality of all channel signals, the MKI signal is zero. With an increase in the offset of the integration interval, the signal power of the MCI increases. In the prototype device, narrow-band filters 13 ¹ , ... 13 ⁴ are used to isolate the necessary channel signals (Fig.1b), and filters 13 ¹ and 13 ^{4 are} tuned to the same frequency component of the initial group signal, and filters 13 ² and 13 ³ - to another. It is also assumed that the amplitudes of the channel signals at adjacent information symbols are practically unchanged. Then, when the integration interval coincides with the information symbol, when there is no MCI, the difference in the amplitudes of the signals at the outputs of each of the filters 13 ¹ , ... 13 ⁴ corresponding to neighboring information symbols is zero:

и

где

измерена при опережении интервала интегрирования (временного окна) на ¹/₂Т_З, a

- при запаздывании на ¹/₂Т_З относительно истинного положения. Соответствующие временные окна формируются в БВТЧ 12 и управляют ключами 17¹ и 17². Ключи 17¹ и 17² отпираются на время опережающего и запаздывающего временных окон по управляющим сигналам соответственно с первого и второго выходов БВТЧ 12.The time discriminator uses two values:

and

Where

measured at forestall integration interval (time window) by _^1/2 T _W, a

- at lag by _^1/2 T _W with respect to the true position. Corresponding time windows are formed in the HDTV 12 and control keys 17 ¹ and 17 ² . The keys 17 ¹ and 17 ^{2 are} unlocked for the time leading and lagging time windows on the control signals, respectively, from the first and second outputs of the BVTCH 12.

и

, возрастает при увеличении смещения интервала интегрирования относительно информационного символа. Выходной сигнал одноканального временного дискриминатора определяется формулойThe average value

and

, increases with increasing offset of the integration interval relative to the information symbol. The output signal of a single-channel temporary discriminator is determined by the formula

This signal is used to correct the temporary position of the clock pulses.

Diagrams of the temporary discriminator are shown in figure 3. Figure 3a shows the temporary position of information symbols, and Figure 3b shows the temporary position of leading and retarded windows.

However, due to the influence of selective fading, it is necessary to use several channels spaced apart in frequency. The prototype device uses two channels: k-th and l-th.

A generalized functional diagram of a two-channel temporary discriminator is shown in figure 4, its operation algorithm can be represented as

where the indices "n" and "h" mean that the amplitudes are measured on odd and even beats;

Signs "+" and "-" refer to the amplitudes measured in advance, respectively at ¹ / _{2T W} and retarded by _^1/2 T _W time windows;

the indices “k” and “l” refer to the k-th and l-th pilot signals.

The inputs of the first-fourth time discriminator in Fig. 4 correspond to the first-fourth inputs of the clock recovery unit 12 in Fig. 1b, the signals of the time windows at the first and second outputs of the HVDC 12 correspond to the signals of Fig. 3b, and the signal from the third output of the HVDC 12 the integration interval in the channels of the demodulator corresponds to the signal in figa.

However, the prototype device does not provide a given low probability of error at large values of F _D T _AND due to intra-character phase fluctuations.

The objective of the invention is to ensure the operability of the modem with fast fading.

It is known that the frequency coherence interval in the KB channel is several hundred hertz; therefore, one adjustment of the carrier frequency of the group signal is clearly not enough.

In the proposed device, this disadvantage is overcome,

- firstly, by introducing into the group signal the required number of pilot signals based on the frequency coherence band;

- secondly, by the direct use of these pilot signals to form reference signals during coherent demodulation of information signals.

To solve the problem in a parallel short-wave modem, consisting of a modulator and a demodulator, the modulator contains an information conversion unit, the information input of which is the input of the modulator, and N of its outputs are connected to the information inputs of the corresponding N phase manipulators, the reference inputs of which are connected to the corresponding N outputs frequency grid generator (RNG), an adder with N inputs, the output of which through a submodulator of one side band (OBP) is connected to the output of the modulator, and the reference One OBP submodulator is connected to the output of the carrier frequency generator, and the synchronization unit, the first output of which is connected to the synchronization input of the information conversion unit, the demodulator contains serially connected carrier frequency adjustment unit, a controlled carrier frequency generator and the OBP detector, the signal input of which is the input of the demodulator and is connected with the first input of the carrier frequency adjustment unit, the second input of which is connected to the reference input of the OBP detector, the output of which through the first key is connected to the inputs of the first and second narrow-band filters, and through the second key is connected to the inputs of the third and fourth narrow-band filters, the outputs of the first, second, third and fourth narrow-band filters are connected to the corresponding inputs of the clock recovery unit (BHF), the first and second outputs of which are connected respectively to control inputs of the first and second keys, RNG with pairs of quadrature outputs, 2N quadrature correlation channels, each of which consists of series-connected corresponding a multiplier and an integrator with a reset, the outputs of 2N integrators with a reset are connected to the corresponding 2N inputs of the decision processing unit, the output of which is the output of the demodulator, and the control inputs of 2N integrators with a reset are connected to the third output of the HDTV, according to the invention N amplitude manipulators are introduced, the outputs of which connected to the corresponding N inputs of the adder, the signal inputs of the N amplitude manipulators are connected to the outputs of the corresponding N phase manipulators, and the information inputs are connected to the corresponding additional N outputs of the information conversion unit, the additional p outputs of the RNG are connected to the corresponding additional p inputs of the adder, and the second output of the synchronization unit is connected to the synchronizing input of the RNG, p narrow-band filters are introduced into the demodulator, connected in series with the corresponding p-phase shifters 90 °, where p is the number of pilot signals in the group signal, p amplitude detectors, p integrators with reset and mp quadrature converters OBP, and the i-th pair of quad RNG full-scale outputs are connected to 3 and 4 inputs of all p pieces of i-quadrature OBP transducers (i = 1, 2, ... m), the first inputs of which are connected to the outputs of the corresponding narrow-band filters and the second inputs are connected with the outputs of the corresponding phase shifters 90 °, the output of the OBP detector is connected to the inputs of all introduced p narrow-band filters, the output of the jth introduced narrow-band filter (j = 1, 2, ... p) is also connected to the signal inputs of all 4m pieces j-x multipliers and through introduced j-amplitude amplified children the ctor and the jth integrator with a reset are connected to the corresponding jth input of the decision processing unit, the four outputs of the quadrature converters of the OBP are connected to the reference inputs of the corresponding 4 multipliers, the control inputs of the p integrators introduced with the reset are connected to the third output of the HDTV, the fourth output of which connected to the synchronizing input of the RNG.

Graphic materials presented in the application:

Figure 1 - Functional diagram of the prototype modem:

1a - modulator;

1b - demodulator.

Figure 2 - Graph of the modem.

Figure 3 - Diagrams of the temporary discriminator.

Figure 4 - Generalized functional diagram of a two-channel temporary discriminator.

Figure 5 - Functional diagram of the proposed modem:

5a - modulator;

5b - demodulator.

6 - Frequency distribution of information and pilot channels.

7 - Charts of the synchronization of subcarriers clock frequency.

Fig. 8 is a functional diagram of a modulator of one sideband.

Figure 9 - Functional diagram of the Converter one side strip.

Figure 10 - Functional diagram of the recovery block clock frequency (BHTCH).

11 - Plot voltage at the outputs of the HVDC.

Fig - Functional diagram of a temporary discriminator.

Functional diagrams of the proposed device are presented in figa and figb, where it is indicated:

Figa:

I is the modulator;

1 - information conversion unit;

2 - synchronization unit;

3 ¹ , ... 3 ^N - phase manipulators;

4 ¹ , ... 4 ^N - amplitude manipulators;

5 - frequency grid generator;

6 - adder;

7 - submodulator OBP;

8 - carrier frequency generator.

Figb:

II - demodulator;

9 - detector OBP;

10 - controlled generator of a carrier frequency;

11 - block adjustment of the carrier frequency;

12 - synchronized frequency grid generator;

13 - block recovery clock;

14 ^1,1 , ... 14 ^{m, 1} , ... 14 ^{1, p} ... 14 ^{m, p} - quadrature converters of OBP;

15 _k ¹ , 15 _l ² , 15 _l ³ , 15 _k ⁴ , 15 ^{4 + 1} , ... 15 ^{4 + p} - narrow-band filters, of which:

15 _l ² , 15 _k ⁴ - filters tuned to the frequency of the k-th pilot signal;

15 _l ² , 15 _l ³ - filters tuned to the frequency of the l-th pilot signal;

16 ^{k, j} (k = 1, 2, ... 4m; j = 1, 2, ... p) - multipliers;

17 ¹ , ... 17 ^p , 17 ^kj (k = 1, 2, ... 4m; j = 1, 2, ... p) - integrators with a reset;

18 ¹ , 18 ² - keys;

19 ¹ , ... 19 ^p - phase shifters 90 °;

20 ¹ , ... 20 ^P - amplitude detectors;

21 is a decision processing unit.

The proposed parallel shortwave modem consists of a modulator I and a demodulator II. Modulator I (figa) contains BPI 1, the information input of which is the input of modulator I, and the synchronization input is connected to the first output of synchronization unit 2, the second output of which is connected to the input of the RNG 5. The first N outputs of BPI 1 are connected to the information inputs of the corresponding phase manipulators 3 ¹ ... 3 ^N, reference inputs are connected to respective first outputs N RNG 5, additional 1 N BPI outputs coupled to data inputs of respective amplitude manipulators 4 ¹ ... 4 ^N, signal inputs of which Comm Nena with respective outputs of the phase manipulator 3 ¹ ... 3 ^N. The outputs of the amplitude manipulators 4 ¹ ... 4 ^{N are} connected to the corresponding first N inputs of the adder 6, the additional p inputs of which are connected to the corresponding additional p outputs of the RNG 5. The output of the adder 6 through the submodulator OBP 7 is connected to the output of the modulator I, and the reference input of the submodulator OBP 7 is connected to the output of the carrier frequency generator 8.

и

, а через второй ключ 18² соединен с входами узкополосных фильтров

и

. Выходы фильтров

,

,

,

соединены соответственно с первым, вторым, третьим и четвертым входами блока восстановления тактовой частоты (БВТЧ) 13, первый и второй выходы которого соединены с управляющими входами 18¹ и 18² ключей соответственно. Выход детектора ОБП 9 соединен также с входом каждого из p узкополосных фильтров 15^4+l, ... 15^4+p, выход каждого из которых через соответствующий амплитудный детектор 20¹, ... 20^p соединен с соответствующим интегратором со сбросом 17¹, ... 17^p. Демодулятор II содержит также 2N квадратурных корреляционных каналов, каждый из которых состоит из последовательно соединенных соответствующих перемножителя 16^k,j (k=1, 2, ... 4m; j=1, 2, ... p) и интегратора со сбросом 17^k,j. Выходы всех интеграторов со сбросом 17¹, ... 17^p, 17^k,j через блок обработки решений 21 соединены с выходом демодулятора II, при этом управляющие входы всех интеграторов 17 соединены с третьим выходом БВТЧ 13, четвертый выход которого соединен с синхронизирующим входом ГСЧ 12, имеющим m пар квадратурных выходов, причем i-я пара квадратурных выходов ГСЧ 12 соединена с третьими и четвертыми входами всех р штук i-x (i=1, 2,.... m;) квадратурных преобразователей ОБП 14^i,1, ... 14^i,p, вторые входы которых соединены с выходами соответствующих фазовращателей на 90° 19¹, ... 19^p, а первые входы соединены с выходами соответствующих узкополосных фильтров 15⁴⁺¹, ... 15^4+p, выход j-го узкополосного фильтра 15^4+j (j=1, 2, ..., p) соединен также с сигнальными входами всех 4m штук j-x перемножителей 16^1,j, 16^2,j, ..., 16^4m,p, опорные входы которых соединены с соответствующими четырьмя выходами квадратурных преобразователей ОБП 14^1,j, 14^2,j, ..., 14^m,j.Demodulator II (Fig. 5b) contains a serially connected carrier frequency adjustment unit 11, a controlled carrier frequency generator 10 and an OBP 9 detector, the signal input of which is the input of demodulator II and connected to the first input of the carrier frequency adjustment unit 11, the second input of which is connected to the reference the input of the detector OBP 9, the output of which through the first key 18 ^{1 is} connected to the inputs of narrow-band filters

and

, and through the second key 18 ^{2 is} connected to the inputs of narrow-band filters

and

. Filter Outputs

,

,

,

connected respectively to the first, second, third and fourth inputs of the clock recovery unit (HVTCH) 13, the first and second outputs of which are connected to the control inputs 18 ¹ and 18 ² keys, respectively. The output of the OBP 9 detector is also connected to the input of each of p narrow-band filters 15 ^{4 + l} , ... 15 ^{4 + p} , the output of each of which is connected to the corresponding integrator with a reset 17 ¹ through the corresponding amplitude detector 20 ¹ , ... 20 ^p , ... 17 ^p . Demodulator II also contains 2N quadrature correlation channels, each of which consists of a series-connected respective multiplier 16 ^{k, j} (k = 1, 2, ... 4m; j = 1, 2, ... p) and an integrator with reset 17 ^{k, j} . The outputs of all integrators with a reset 17 ¹ , ... 17 ^p , 17 ^{k, j} through the decision processing unit 21 are connected to the output of the demodulator II, while the control inputs of all integrators 17 are connected to the third output of the HDTV 13, the fourth output of which is connected to the clock input RNG 12 having m pairs of quadrature outputs, and the ith pair of quadrature outputs of the RNG 12 is connected to the third and fourth inputs of all p pieces ix (i = 1, 2, .... m;) of quadrature converters OBP 14 ^{i, 1} , ... 14 ^{i, p} , the second inputs of which are connected to the outputs of the corresponding phase shifters by 90 ° 19 ¹ , ... 19 ^p , and the first inputs are connected to the outputs of the corresponding narrow-band filters 15 ^{4 + 1} , ... 15 ^{4 + p} , the output of the j-th narrow-band filter 15 ^{4 + j} (j = 1, 2, ..., p) is also connected to the signal inputs of all 4m pieces jx of multipliers 16 ^{1, j} , 16 ^{2, j} , ..., 16 ^{4m, p} , the reference inputs of which are connected to the corresponding four outputs of the quadrature converters OBP 14 ^{1, j} , 14 ^{2, j} , ... , 14 ^{m, j} .

The operation of the modulator in figa is generally similar to the operation of the prototype modulator in figa, except for four points:

- p pilot signals spaced in frequency are introduced into the group signal of the prototype modulator-prototype, as shown in Fig.6;

- to ensure the possibility of using combined amplitude-phase manipulation of the QAM type, N amplitude manipulators 4 ¹ , ... 4 ^{N are} introduced;

- to tightly link the phases of all subcarriers and pilot signals to clock pulses, RNG 5 synchronization is applied (the connection between the second output of synchronization block 2 and the RNG input 5);

- for clock synchronization, two pilot signals are used from the outputs (N + k) and (N + l) of the RNG 5, k, l <p.

From Fig.6 it follows that the bands of the pilot channels do not overlap with the bands of information channels. This is done in order to extract pilot signals using narrow-band filters 15 (Fig.5b) to eliminate inter-channel interference.

, синхронизируемых тактовыми импульсами. Для обеспечения возможности синхронизации в демодуляторе II такая синхронизация осуществляется в модуляторе I путем синхронизации всех поднесущих на выходах ГСЧ 5 (фиг.5а) тактовыми импульсами со второго выхода блока синхронизации 2, как показано на фиг.7.As will be shown below, the reference signals for coherent demodulation of information signals are generated from the pilot signal and auxiliary oscillations with frequencies that are multiples of

synchronized by clock pulses. To enable synchronization in demodulator II, such synchronization is carried out in modulator I by synchronizing all subcarriers at the RNG outputs 5 (Fig. 5a) with clock pulses from the second output of synchronization unit 2, as shown in Fig. 7.

The subcarrier frequencies are still determined by formula (1).

Thus, the synchronized frequency grid generator 5 instead of sinusoidal signals should produce phase-manipulated signals with carrier frequencies equal to the channel ones.

The demodulator in Fig.5b works as follows. Both the prototype demodulator and the proposed demodulator contain N pairs of quadrature correlation information channels, each of which consists of a series-connected respective multiplier and an integrator with a reset. A significant difference lies in the formation of reference signals of the multipliers. In the prototype demodulator, reference signals are generated by a highly stable frequency grid generator 11 (Fig. 1b), and in the proposed demodulator, 2m pairs of quadrature reference signals (4 m in total) are formed from one pilot signal to serve m pairs of information correlation channels (Fig. 6) . Obviously, 2N = 4mp.

где F_пj - частота j-го пилот-сигнала.The input signal in the detector OBP 9 is converted into the original group signal (such as at the output of the adder 6 in figa). Of the p pilot signals included in it, the kth and lth are used both for generating reference signals of quadrature correlation information channels and for clock synchronization, p pilot signals are allocated by the corresponding channel filters 15 ^{4 + l} , ... 15 ^{4 + p} . Each j-th pilot signal (j = 1, 2, ... p) is phase-shifted by 90 ° in the corresponding block 19 ¹ , ... 19 ^p , and a pair of squared pilot signals are supplied to the first and second the inputs of the corresponding quadrature Converter OBP 14 ^{i, j} , where the index i (i = 1, 2, ... m) means the number of a pair of "served" information channels (Fig.6), j = 1, 2, 3, ... , p for each i. The frequencies of the i-th pair are equal

where F _pj is the frequency of the j-th pilot signal.

The third and fourth inputs of the quadrature converter OBP 14 ^{i, j} from the corresponding outputs of the frequency generator 12 receive two squared sinusoidal signals with a frequency F _i = (i + 1) Δf. As a result of the frequency conversion ^, a pair of squared sinusoidal signals with a frequency of [F _pj + (i + 1) Δf] is formed at the first and second outputs of the OBP 14 ^{i, j} converter, and at a frequency of [F _pj - (at the third and fourth outputs) i + 1) Δf].

These signals are reference during quadrature demodulation of the corresponding information signals carried out in correlation channels, each of which contains a 16 ^{k, j} multiplier and its corresponding integrator with a reset of 17 ^{k, j} (k = 4i-3, 4i-2, 4i-1, 4i; j = 1, 2, 3, ..., p for each i), as a result of which the projections of the signal vectors x _{i, j, n} , y _{i, j, n} and x _{-i, j, n} , y are determined _{-i, j, n} .

From these projections in the decision processing unit 21 (Fig. 56), the position of the signal in the QAM constellation is determined.

Because the transmission coefficient of the channel varies over time, and the values of the projections of the signal vector are randomly changed, which leads to errors in determining its position in the constellation. To combat this phenomenon, normalization of projections is used by dividing them in block 21 by the amplitude of the pilot signal, the value of which is formed by a chain consisting of an amplitude detector 20 ^j and an integrator with a reset of 17 ^j . Thus, due to the high degree of correlation between fluctuations of the pilot and “serviced” information signals, it becomes possible to reduce the likelihood of errors when demodulating multiposition signals in the conditions of fast fading.

As the proposed device as a whole, and its individual blocks can be made both in analog and digital form. Functional and circuit diagrams of almost all blocks are given in the description of the prototype (Equipment for the transmission of discrete information MS-5. / Edited by A. M. Zaezdny and Yu. B. Okunev. - M .: Communication, 1970).

Tracking changes in carrier frequency is most easily done using single-band modulation with partially suppressed carrier. At the same time, blocks 10 and 11 in FIG. 5b are combined into a PLL system according to the scheme shown in the book (Lindsay V. Synchronization systems in communication and control. Transl. From English / Edited by Yu.N. Bakaev and M.V. Kapranova. - M .: Sov. Radio, 1978, fig. 4.19, p. 172).

The scheme of the OBP submodulator is known and is given, for example, in the book (Lathi B.P. Information Transmission Systems. Trans. From English / Ed. By B.I. Kuvshinov. - M.: Communication, 1971, Fig. 3.18, p. 136). The OBP 7 submodulator (Fig. 5a) with a partially suppressed carrier based on this scheme can be performed as shown in Fig. 8, where it is indicated:

7.1 ¹ and 7.1 ² - phase shifters 90 °;

7.2 ¹ and 7.2 ² - multipliers;

7.3 - attenuator;

7.4 - adder.

The formation of one side strip is based on the ratios

where (α + β) means the total frequency located in the upper sideband (PFS);

(α-β) means the difference frequency located in the lower sideband (NBP).

At input 1, the sum of the channel signals of the form cosβ = cos (2πF _i t) acts, and at input 2, the carrier signal cosα = cos (2πf ₀ t) acts. The carrier signal attenuated by attenuator 7.3 is summed in block 7.4 with a single-band signal.

The formation of each reference signal requires two quadrature components of one pilot signal and two quadrature components of one signal from the output of the RNG 12 (Fig.5b). Each quadrature converter OBP 14 (figb) produces two pairs of quadrature reference signals to serve two correlation information channels that are symmetrical relative to the pilot channel.

The functional diagram of the quadrature converter OBP 14 is shown in Fig.9, where it is indicated:

14.1 ¹ , ... 14.1 ⁴ - multipliers;

14.2 ¹ , 14.2 ² - adders;

14.3 ¹ , 14.3 ² - subtraction schemes.

The quadrature converter OBP 14 contains multipliers 14.1 ¹ , ... 14.1 ⁴ , adders 14.2 ¹ , 14.2 ² and subtraction schemes 14.3 ¹ , 14.3 ² . The first input of the converter OBP 14 is connected to the first inputs of the multipliers 14.1 ¹ and 14.1 ³ , the second input of the converter OBP 14 is connected to the first inputs of the multipliers 14.1 ² and 14.1 ⁴ . The third input of the converter OBP 14 is connected to the second inputs of the multipliers 14.1 ¹ and 14.1 ⁴ , the fourth input of the converter OBP 14 is connected to the second inputs of the multipliers 14.1 ² and 14.1 ³ . The outputs of the multipliers 14.1 ¹ and 14.1 ^{2 are} connected to the corresponding inputs of the adder 14.2 ¹ , the output of which is the first output of the OBP 14 converter, and with the corresponding inputs of the subtraction circuit 14.3 ^{1, the} output of which is the third output of the OBP 14 converter. The outputs of the multipliers 14.1 ³ and 14.1 ^{4 are} connected to the corresponding inputs of the subtraction circuit 14.3 ² , the output of which is the second output of the converter OBP 14, and with the corresponding inputs of the adder 14.2 ² , the output of which is the fourth output of the converter OBP 14.

The operation of the quadrature transducer OBP 14 (figb) is based on trigonometric relations

In these relations, also (α + β) means the total frequency (PFS), and (α-β) - the difference frequency (NBP).

:ΔF, 2ΔF,...mΔF, т.е. являются гармониками частоты

.Thus, in the formation of 2m pairs of quadrature reference signals involved the corresponding pilot signal and m pairs of quadrature signals from the outputs of the RNG 12. These signals have frequencies that are multiples of

: ΔF, 2ΔF, ... mΔF, i.e. are harmonics of frequency

.

, то для получения синхронных опорных сигналов приходится синхронизировать ГСЧ 12 тактовыми импульсами (фиг.7) так же, как и в модуляторе. При этом sin(2πF_пjt) будет соответствовать sin(2πF_it), a cos(2πF_пjt) будет соответствовать cos(2πF_it), т.е. использование соотношений (10) будет правомерным.Because in the demodulator (figb) with the input signal is synchronized only the oscillation of the clock frequency

, then to obtain synchronous reference signals, it is necessary to synchronize the RNG 12 with clock pulses (Fig.7) in the same way as in the modulator. In this case, sin (2πF _pj t) will correspond to sin (2πF _i t), and cos (2πF _pj t) will correspond to cos (2πF _i t), i.e. the use of relations (10) will be legitimate.

Functional diagram of the clock recovery unit 13 in Fig. 5b, according to Fig. 5.5 on page 79 of the description of the prototype, shown in figure 10, where indicated:

13.1 - temporary discriminator;

13.2 - crystal oscillator;

13.3 - adder;

13.4 - key;

13.5 - switch;

13.6 - differentiating circuit;

13.7 - frequency divider;

13.8 - block decoders;

13.9 - pulse shaper.

The clock frequency is obtained by dividing the pulse frequency in the divider 13.7 from the output of the crystal oscillator 13.2. The correction of the position of the clock pulses is carried out by adding a pulse to the pulse sequence from the output of the crystal oscillator 13.2 or by eliminating the pulses from this sequence by the control signal from the output of the temporary discriminator 13.1. Correction is made once on a tact duration T _t . At the output of the adder 13.3, a sequence is formed with an added pulse from the output of the differentiating circuit 13.6, and at the output of the key 13.4, a sequence with an excluded pulse is formed. The pulse is excluded by locking the key 13.4 by the signal from the output of the driver 13.9. The switch 13.5 passes one or another sequence to the output, depending on the polarity of the output signal of the temporary discriminator 13.1. The decoder unit 13.8 generates pulses, on the basis of which the driver 13.9 generates time window signals that control the keys 18 ¹ and 18 ² (Fig.5b), reset pulses of the integrators 17 (Fig.5b) and clock pulses for synchronizing the frequency generator 12 (Fig. 5 B).

The voltage diagrams at the outputs of the clock recovery unit 13 (Fig.5b) are shown in Fig.11. The sequence of pulses U _s that serve to reset the integrators 17 (Fig.5b), controls the keys included in their composition, which close the outputs of the integrators to the ground.

The functional diagram of the temporary discriminator 13.1 (Fig.9) is shown in Fig.12, where it is indicated:

1 ¹ , 1 ² , ... 1 ⁴ - switches;

2 ¹ , 2 ² , ... 2 ⁸ - peak detectors;

3 ¹ , 3 ² , ... 3 ⁵ - subtracting devices;

4 ¹ , 4 ² , ... 4 ⁴ - device capture module (half-wave rectifiers);

5 ¹ , 5 ² - adders;

6 - threshold device.

In switches 1, the input information symbols are divided into even and odd. In peak detectors 2, the corresponding amplitudes are calculated. Then, the output signal U _{d is} calculated according to expression (8).

To form the relay resulting discriminatory characteristics at the output, a threshold device 6 with a zero threshold is used.

, происходит исключение импульса на выходе коммутатора 13.5 (фиг.9), а если наоборот - добавление.If

, the pulse is eliminated at the output of the switch 13.5 (Fig. 9), and if on the contrary, the addition.

Generators of frequency grids can be made in various ways: purely digital (for example, as described in the journal Engineering Microelectronics, 2001, No. 9, p. 15) or discrete-analog, as shown in the description of the prototype device.

The decision processing unit 21 (Fig. 5b) can be made on the basis of a microprocessor, for example, TMS 320 Cxx, Motorola 56xxx, Intel, etc., which contains the corresponding calculation program.

Claims (1)

A parallel short-wave modem consisting of a modulator and a demodulator, the modulator comprising an information conversion unit, the information input of which is the input of the modulator, and N of its outputs are connected to the information inputs of the corresponding N phase manipulators, the reference inputs of which are connected to the corresponding N outputs of the frequency grid generator (RNG ), an adder with N inputs, the output of which through the submodulator of one sideband (OBP) is connected to the output of the modulator, and the reference input of the submodulator of OBP is connected to the carrier frequency generator, and the synchronization unit, the first output of which is connected to the synchronizing input of the information conversion unit, the demodulator contains serially connected carrier frequency adjustment unit, a controlled carrier frequency generator and OBP detector, the signal input of which is the demodulator input and connected to the first input of the adjustment unit carrier frequency, the second input of which is connected to the reference input of the OBP detector, the output of which through the first key is connected to the inputs of the first and second narrow-field filters, and through the second key is connected to the inputs of the third and fourth narrow-band filters, the outputs of the first, second, third and fourth narrow-band filters are connected to the corresponding inputs of the clock recovery unit (BHF), the first and second outputs of which are connected respectively to the control inputs of the first and the second key, RNG with pairs of quadrature outputs, 2N quadrature correlation channels, each of which consists of a series-connected respective multiplier and integrator with sat Osom, the outputs of 2N integrators with a reset are connected to the corresponding 2N inputs of the decision processing unit, the output of which is the output of the demodulator, and the control inputs of 2N integrators with a reset are connected to the third output of the HVDC, characterized in that N amplitude manipulators are inserted into the modulator, the outputs of which are connected to the corresponding N inputs of the adder, the signal inputs of N amplitude manipulators are connected to the outputs of the corresponding N phase manipulators, and the information inputs are connected to the corresponding additional N information conversion outputs, additional p outputs of the RNG are connected to the corresponding additional p inputs of the adder, and the second output of the synchronization unit is connected to the synchronizing input of the RNG, p narrow-band filters are introduced into the demodulator, connected in series with 90 ° introduced phase shifters, where p is the number pilot signals in a group signal, p amplitude detectors, p integrators with reset and mp quadrature converters OBP, and the i-th pair of quadrature outputs of the RNG is connected to the 3rd and 4th the inputs of all p pieces ix quadrature converters OBP (i = 1, 2, ... m), the first inputs of which are connected to the outputs of the respective entered narrow-band filters, and the second inputs are connected to the outputs of the corresponding phase shifters 90 °, the output of the detector OBP is connected to the inputs of all introduced p narrow-band filters, the output of the jth introduced narrow-band filter (j = 1, 2, ... p) is also connected to the signal inputs of all 4m pieces of jx multipliers and through the introduced series-connected j-th amplitude detector and j-th integrator with reset connected corresponding j-th input block of processing solutions, four outputs quadrature SSB converters are connected to respective reference inputs of the multipliers 4, p control inputs entered integrators with reset are connected to the third output BVTCH fourth output connected to the synchronization input of the RNG.

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