CC BY
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Visnyk NTIJU KP1 Seriia Radiolekhnika tiadioaparat.obuduuannia, "2021, Iss. 87, pp. 5—13
621.391.17
Optimum Coherent and Incoherent Demodulators of BPSK and DBPSK Radio Signals with Manchester Encoding
Parfeniuk V. H., Sdbadash S. S., Stavimuk R. L.
S. Korolov Zhytomyr Military institute, Ukraine E-mail: slrob2J,3&gmaü. com. sabadashss&ukr.ncl. r.slavisiuk&gmaü. com
Algorithms and schemes of optimal coherent, and incoherent demodulators of binary radio signals wit.li phase and differential phase shift-keying (DPSK) wit.li Manchester encoding of the modulating signal are proposed. The use of DPSK makes it. possible to effectively deal with the phase ambiguity of the reference oscillation generator of the correlation receiver. This solution allows you to overcome the so-called «reverse work» effect, in the demodulator of signal with phase-shift, keying. Differential and Manchester encoding finds it's application in various areas of use of digital systems for information transmission (DSIT): from local and personal area networks, to space optical communication systems. There are many types of DSIT: radio communication systems (in the Bluetooth standards, in NFC technology, as well as in high-resolution space remote sensing (SRS)), wired data transmission systems (in the local area networks of the Ethernet, family), so are optical communication systems (FSO, ISOWC and SpaceWire). It's shown that, the joint, use of DPSK and Manchester encoding provides higher noise immunity when used in DSIT and retain the advantages of Manchester encoding with respect, to symbolic synchronization of the demodulator. The given algorithms and schemes are based on the use of reception in general and the features of Manchester encoding, which allows using the full energy of the information bit. for demodulation. To assess the potential noise immunity of the proposed demodulator schemes, it's assumed that, the modulated signals are orthogonal in the amplified sense. The conducted mathematical modeling of the proposed technical solutions confirmed their operabilit.y and higher noise immunity compared to the symbol-by-symbol reception. It's proposed to use the developed algorithms and schemes of demodulators in the receivers of the SRS with high resolution, in the receivers of optical communication systems and in the receiving part, of the equipment, of local networks of the Ethernet, family.
Keywords: Manchester encoding: BPSK: DBPSK: Ethernet.: reception in general: symbol-by-symbol reception: soft, decision making: orthogonal in the amplified sense signal
DOI: 10.20535/RADAP. 2021.87.5-13
Introduction
In the development of digital systems for information transmission (DSIT). the main issues to be solved are the choice of signals that provide maximum noise immunity and a specified information rate for a given channel [1]. As it is commonly known, the maximum noise immunity is provided by opposite signals, for which the cross-correlation coefficient is equal to — 1. Such signals can be generated by using phase-shift keying with a phase difference 180°.
However, in spite of the high noise immunity of binary phase-shift keying (BPSK). its direct application in DSIT is associated with significant difficulties. They are caused by the need to generate a coherent reference oscillation for the demodulator of the correlation receiver. It is also known that all possible schemes nsed for the generation snch an oscillation are characterized by the phase ambiguity of the output signal which
causes the so-called «reverse work» effect. Therefore, in practice, differential phase shift-keying (DPSK) is often nsed instead of phase-shift keying.
Duo to its qualities, differential encoding of the modulation signal most often finds its application in local and personal area networks, satellite radio relay-arid other DSIT. In general, differential encoding can be nsed for different types of phase shift-keying. For example, it is known that the popular Bluetooth standard implements such types of phase shift-keying as ^/^DQPSK (^/4-shifted Differential Quadrature Phase-Shift Keying) and 8-DPSK [2, 3]. Another example describes that DPSK is nsed in a spaceborne sensor called the Advanced very-High-R.esolntion Radiometer (AVHRR), as well clS ct simpler version the sensor with Higli-Resolntion Picture Transmission (HRPT) [4]. In the original sources of the AVHRR
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Parfoniuk V. H., Sabadash S. S., Stavisiuk R. L.
HR.PT. this typo of modulation is called Digital Split Phase Modulation.
It is known that a special case of BPSK is Manchester encoding [5]. In this case, the information symbols controls the phase of a square wave carrier whose frequency is the data rate. At the same time. information symbols are encoded with a pair of Manchester symbols. In this regard, the idea of differential encoding, phase shift-keying and Manchester encoding should be considered in tandem to combine their qualities when used in DSIT.
However, an analysis of recent publications on the described topic indicates an increase in trends in research and development of free space optics (FSO) technology [6 8]. One of the most important applications of FSO technology is the possibility of its use in satellite applications. Among such systems, the inter-satellite optical wireless communication (IsOWC) system is known [7. 8]. The use of DPSK with Manchester encoding in IsOWC makes it possible to improve the quality performance of the system, in particular, to provide low power, compact size etc [7]. Differential Manchester encoding finds its application as an optional coding scheme for the SpacoWiro telecommunications network for spacecraft [9].
In addition to the above of application,
differential Manchester encoding is proposed to be used in semi-coherent and incoherent detectors of the communication system with backscattering of the environment. It is known that ambient backscattor communication is a newly emerged paradigm, which regarded as a promising solution for enabling large-scale deployment of future Internet of Things networks [10]. Besides that, in the article [11] proposes a novel method of Manchester encoding using the adiabatic technique logic in NFC (Near Field Communication) passive tags for energy consumption minimization. The proposed method can bring large interrogation range, increase security and maximizes the reader's battery-life.
Thus, the topic of this article remains relevant in the development of systems for information transmission in various areas of application, let us move on to the statement of the research problem.
1 Statement of the problem
The theory of optimum coherent and incoherent reception of BPSK and binary DPSK (DBPSK) signals is described in sufficient detail in [1.12.13]. In known studies, optimum reception algorithms are considered for bipolar representation of the modulating binary non-return-to-zero signal (NRZ encoding) [5]. One of the disadvantages of NRZ encoding is the lack of self-synchronization properties: for long sequences of same symbols (logical ones or zeros) NRZ signal does not change. It's also known that the use of Manchester encoding for the envelope of BPSK or DBPSK radio
signals in DSIT provides significant advantages for generating symbolic synchronization signals for the demodulator, since the spectrum of the modulating signal in this case contains a harmonic component that coincides in frequency with the bit rate and has good self-synchronization properties [8].
In turn, the use of Manchester encoding for each information bits assumes the formation of two symbols of half the duration, which causes the expansion of the signal spectrum and requires the bandwidth double increasing of the channel. It should be also noted that in the case of optimum symbol-by-symbol reception of such a signal, the signal-to-noise ratio (SNR) will be twice lower and will reduce immunity. It follows from the above that there IS 3. task of developing such coherent and incoherent algorithms for optimum demodulation of radio signals with Manchester encoding. which are received using the full energy of the information bit. but it remains possible to realize their advantages regarding the formation of symbol synchronization signals.
2 Analysis of recent research and publications
The algorithms of optimum reception using all energy of an information bit with Manchester encoding of an envelope can be created, using not symbol-by-symbol reception, but the reception of the information bit clS ct whole including two symbol.
In addition. Manchester encoding can be considered as the use of error-correcting code with duplicated number of elements (correlation code). However, such a block code only makes it possible the detection of errors under symbol-by-symbol reception. In this case, the losses of energy of the information's bit can be reduced by implementing decoding in a broad sense with soft decision-making, combining demodulation and decoding operations [14]. A variant of such a solution of the problem using Manchester encoding is proposed in [15].
3 Purpose and objectives of research
The research task is to develop coherent and incoherent algorithms for optimum demodulation of BPSK and DBPSK radio signals in order to increase the immunity of DSIT and maintain the advantages of Manchester encoding. It is also necessary to assess the potential noise immunity of the developed demodulation algorithms using known approaches on this issue.
4 Results
Consider the problem of distinguishing two (binary) deterministic signals. Assume that the signal s1(t)
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represents the binary symbol «1», and the signal s0(t) represents the symbol «0».
According to the accepted assumptions the mathematical model of the signal at the receiver input
y(t) = Asi(t) + (1-A) so(t) + n (t), 0 < t < T, (1)
where A is an unknown parameter that can take one of two values: A =1 (transmitted signal s1(t)) and A = 0 (transmitted signal s0(t)); n(t) is an interference in the form of additive white Gaussian noise; T is the duration of information's bit.
The model of the received signal (1) suggest that at the input of the receiver there is one of two possible signals of the same duration and energy it is not known which (s1 (t) or so(t)). To simplify the problem, it is assumed that the a priori probabilities of the presence of each of them are assumed to be known.
The received realization y(t) shall be used for finding the value of the parameter A*, i.e. for finding out which of the signals — s1(t) or s0(t) — is present in the realization (1). In other words, the task is testing two hypotheses: hypothesis H0 — the realization y(t) contains s1(t), i.e. A* = 1; hypothesis H1 — the realization contains the signal s0(t),i.e. A* =0.
In this case, the algorithm for optimum coherent reception of signals by the criterion of an ideal observer f , ] for the decision on the transmitted signal s1(t) can be represented as follows:
T T
J y(t) S1(t) dt y(t) so(t) dt, (2a) 0 0
and for the decision on the transmitted signal s0(t)
y(t) Sl(t) dt < y(t) so(t) dt,
(2 b)
Clock Bitstream
^ Information t symbols
Manchester t code
Fig. 1. Bitstream encoding by the Manchester code
Let symbol «0» of the Manchester code corresponds to the elementary signal — S0 cos w0t, and the symbol «1» corresponds to S0 cos u0t. Then the information symbols «1» and «0» will correspond to the signals s\(t) and s0(t) which are sequences of two elementary signals in the interval [0, T] which can be represented as follows:
Sl(t)=
so(t) =
-S0 cosu0t, 0 <t<T/2;
S0 cosu0t, T/2 <t<T,
S0 cosu0t, 0 <t<T/2;
-S0 cosu0t, T/2 <t<T,
(3)
where S0 is the signal amplitude.
Taking into account (3), the algorithm of optimum coherent reception (2) can be represented as follows:
X —Y > 0, transmitted, signal s1(t) ;
(4)
where f y(t) Si(t) dt are the correlation integrals, the 0
ratio of which evaluates the parameter A, i = 0, 1.
Assume that the data are transmitted using BPSK with a phase difference 180°. According to the rule of bitstream encoding by the Manchester code (as per IEEE 802.3 standard flC]), the information symbol «1» (Fig. la) is encoded by a sequence of two symbols «01» of the Manchester code, and the information symbol «0» is encoded by the sequence of symbols «10» (Fig. lb).
X —Y < 0, transmitted signal s0(t),
where to reduce the formula X and Y are denoted as T T/2
X = J y(t)cos w0tdt; Y = J y(t)cos w0tdt. (5)
T/2 0
X, Y are the correlation integrals which are determined on intervals [T/2, T] and [0, T/2] with a duration of t = T/2, respectively (Fig. ).
The block diagram of the coherent demodulator which implements the algorithm (4) is shown in Fig. 2. In addition to the multiplier and integrator which calculate the value of the correlation integral on the duration of the Manchester code symbol t = T/2, the scheme contains a carrier regenerator (CR), a symbol synchronization device (SSD), a delay line on T/2, subtracter and a decision-making device (DMD) for the transmitted data symbol. DMD makes a decision in accordance with the signal sign at the output of the subtracter at the end of the moment T of the signal. The positive sign corresponds to the transmitted signal s1(t), md the negative corresponds to s0(t).
8
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Fig. 2. Block diagram of the optimum coherent demodulator of BPSK (DBPSK) signals with Manchester
encoding (differential Manchester encoding)
CR shown in Fig. 2 restores the continuous carrier and can be built according to the known schemes of phase synchronization devices based on Pistolkors, Si-forov, Costas [1.5.17]. The integrator performs current integration within 0... T/2. The SSD generates symbol sync pulses (SSP) with a frequency f sym = 1/T which determine the time moments of DMD operation. They are also used to reset the integrator (after doubling the f sym). A demodulated sequence of symbols u is formed at the DMD output.
To assess the potential noise immunity of a coherent demodulator, we can use the general formula for optimum reception of BPSK signals [5,13], in which the signals (3) are orthogonal in the amplified sense.
It is worth noting that the orthogonality condition in an amplified sense can be represented in a general form [13,18] using analytical signals
Si(t) S*(t) dt = 0,
(6)
p,.
2 erfc {Vq2)
: ^erfc
(7a)
packages for mathematical calculations. Therefore, this article will use just such a variant of the error function.
The scheme shown in Fig. 2 can also be used for coherent demodulation of DBPSK signals if a differential decoder is added to its output, as shown by dashed line in Fig. 2. In this case the probability of error caused by the presence of a decoder at the demodulator output will increase approximately twice [5,13] and can be calculated by the formula
PP,
- =erfc ^v^2) .
(7b)
where Si(t) = s() +jst(t), Sk(t) = sk(t) +jsk(t) are analytical signals; S*(t) = sk(t) — jsk(t) is a function complex conjugate with Sk(t); si(t), sk(t) are the Hilbert-transformed signals si(t), sk(t), respectively; T is the duration of signals Si(t) and Sk (t).
Then, according to (2) and taking into account the SNR q2, the ratio of the signal energy in the interval T
ty N0, the potential noise immunity of the coherent demodulator of BPSK signals can be represented as
The signals encoded by the Manchester code can also be received clS ct whole in channels with slow fluctuations of an initial phase of signals when the DBPSK is used. As result, we obtain the scheme of the optimum incoherent demodulator using the approach proposed in [13].
DBPSK assumes the bitstream encoding by differential Manchester code. This method is used by-IEEE 802.5 specification for Token Ring LAN [2].
The rulos for encoding with the Manchester code are presented in Fig. 3. The information symbol «1» of the bitstream (Fig. 3a) is encoded by a sequence of two Manchester code symbols that are inverted relative to the previous two symbols, and the information symbol «0» is encoded by a sequence of two Manchester code symbols that coincide with the previous two symbols (Fig. 3b).
Clock
where erfc (x) = —^ / e f2 dt is the complementary V^ X
error function; q2 = E^/N^, E^ = 2ES = PST is signal energy per information's bit; Es is the energy of the Manchester code symbol; Ps =0,5Sg is the signal power.
It should be noted that various variations of interconnected formulas for calculating the probability of error based on the Gaussian probability distribution are known [1]. However, it is more convenient to use the formula erfc (x) due to its presence in known software
Bitstream
Information
t symbols
Differential Manchester code
Fig. 3. Differential encoding of tho bitstream by tho Marichoster code
So, in case of DBPSK, tho valnes of tho transmittod information synibol are detormined not by tho two symbols of tho Marichoster codo thomselvos in tho timo
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interval [0, T], but by a sequence of four symbols of the Manchester code in the interval [0, 2T].
Let symbol «0» of the Manchester code correspond to the elementary signal —S0 cos w0t, and the symbol «1» to S0 cos w0t. Then the information symbols «1» and «0» correspond to the signals si(t) and s0(t) which are sequences of four elementary signals in the interval [0, 2T]. The information symbols «1» and «0» correspond to the signals transmission
Gaussian noise with constant spectral density assumes calculating the square of the modulus of the correlation integral for each signal [13] and comparing their values:
Z\ > zl zl < zl,
transmitted, signal s1(t); transmitted signal so(t),
Sl(t) =
so(t) =
Sq cos (wot + p —So cos (wot + <p Sq cos (wot + <p ' —Sq cos (wot + p So cos (wot + ip — So cos (wot + <p So cos (wot + tp
0 <t< T/2; T/2 <t < 3T/2; 3T/2 <t < 2T,
0 <t< T/2; T/2 <t< T;
T <t < 3T/2; 3T/2 <t < 2T,
where
zi =
(8)
71 =
L0 =
y(t) Si (t) dt
y(t) so(t) dt
+
+
y(t) s**(t) dt
y(t) so(t) dt
(9)
(10a)
(10b)
0, 1:
where p is a random initial phase with a uniform distribution.
The algorithm of optimum incoherent reception for two signals of equal duration and equal energy with random initial phases against the background of white
s* (t) is the Hilbert-transformed signal Si (t), i Ts = 2T = At is the signal duration.
Taking into account (8) and (10). the algorithm for optimum incoherent reception (9) of DBPSK signals with differential Manchester encoding for the decision on the transmitted signal s1(t) will be presented in formula
T/i T 3T/i 2T
J y(t) cos w0tdt — J y(t)cos w0tdt — J y(t)cos w0tdt + J y(t)cos w0tdt
T/i
3T/i
+
+
T/i T 3T/i IT
J y(t)sin w0tdt — J y(t)sin w0tdt — J y(t)sin w0tdt + j y(t)sin w0t dt 0 T/i T 3T/i
T/i T 3T/i 2T
— J y(t)cos w0tdt + j y(t)cos w0tdt — J y(t)cos w0td,t + J y(t)cos w0td,t
+
o
T/i
T/i T
T 3T/i
3T/i TT
(11)
+
— j y(t)sin w0tdt + j y(t)sin w0tdt — j
T/i
By performing simple transformations and reductions in (11) and using the following notation:
y(t)sin w0tdt + J y(t)sin w0tdt 3T/i
s1(t) algorithm can be represented as follows: zi — Zi = Va — Vb > 0,
(13a)
nT/i
Xn = j y(t)cos w0tdt;
(n-1) T/i nT/i
Yn = J y(t)sin wot dt,
(n-1) T/i
and for the decision on the transmitted signal s0 (t)
(12)
Zi — Z20 = Va — Vb < 0,
(13b)
where to reduce the formula Va mid are denoted as Va = (X1X4 + X2x3) — (X1X3 + X2x4);
Vb = (Y1Y3 + Y2Y4) — (Y1Y4 + Y2Y3).
(14)
where n = 1, 2, 3, 4 is the symbol number of the Manchester code in the interval [0, 2T], we get the algorithm for optimum incoherent reception of DBPSK signals with differential Manchester encoding in a simplified form. For the decision on the transmitted signal
It should be noted that the sequence of symbols of the differential Manchester code can be the inverse of the encoding example, which in Fig. 3b. Inversion of symbols can occur when an even number of symbols «1» is presented in the bitstream. It can be assumed
2
2
2
2
2
2
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HapcJ)oiiioK B. F., Ca6a,aaiii C. C., CiaiiicioK P. ,11.
that such a situation should affect the results obtained when constructing the algorithm described above. However, as calculations show, formulas (13)-(14) will not change from the inversion of signals (8). This indicates the invariance of the developed algorithm from the inversion of the sequence of Manchester code symbols.
So. on the basis of the proposed algorithm (13). it is possible to construct a block diagram of an incoherent demodulator of DBPSK signals with differential Manchester encoding (Fig. 4).
The scheme (Fig. 4) includes an in-phase channel that calculates the value of Va and a quadrature channel that calculates the value of Vb in accordance with (14) on an interval of four elementary symbols of the Manchester code [0, 2T]. Channel integrators calculate the values of correlation integrals (12) periodically on the interval of the duration of the Manchester code symbol t = T/2. Components X1 and Y1 are formed immediately from the output of the integrators, and components X2; Y2, X3; Y3 and
X4; Y4 are obtained from the outputs of three series-connected delay line on T/2. In addition, for direct calculate the values of Va and Vb multipliers, adders and subtracters are nsod in the scheme. From the output of the last snbtractor voltage is formed, which is proportional to the difference Va — DMD functions in the same way as in the scheme of the coherent demodulator (Fig. 2) make a decision according to the signal sign at the output of the subtracter. The positive sign corresponds to the transmitted signal s1(t), but the negative to s0(t). The SSD (does not shown in Fig. ) generates SSP with a frequency fsym = 1/T which determines the time moments of DMD decisionmaking to reset the integrators (after doubling the
fsym)'
From analysis (8) and (11) it follows that the decision on the transmitted signal will not be affected by the random initial phase. Therefore, in the scheme of an incoherent demodulator, the oscillation generator with the carrier frequency wq must be independent.
Fig. 4. Block diagram of the optimum incoherent demodulator of DBPSK signals with differential Manchester
encoding
To assess the potential noise immunity of an incoherent demodulator of DBPSK signals, the general formula for their optimum reception can be used, given that the signals (8) are also orthogonal in the amplified sense according to (6). Then, according to (10), taking into account the SNR q2, the ratio of the signal energy in the interval of the information bit T to the noise spectral density N0, the potential noise immunity of the incoherent demodulator of DBPSK signals with differential Manchester encoding can be determined as
Pf
1
err 2 ^
(15)
To verify the operability of the developed demodulator schemes and evaluate their potential noise immunity, mathematical modeling was performed using virtual demodulators developed on a PC in the Lab VIEW 2020 development environment for a visual programming. Modeling confirmed the operability of the proposed schemes of the demodulators of signals with Manchester encoding and the possibility of using
2
9
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11
formulas (7) arid (15) to assess their potential noise in Fig. 5b for the incoherent demodulator of DBPSK immunity. signals with differential Manchester encoding.
The calculation of results and modeling data are shown in Fig. 5a for the coherent demodulator and
Pt 10
err -1
10
10
-2
-3
,-4
10 10"5 10"6 10" ~
\ ;
! ' V* \ \ \ ;
= \\ \ \ ;
= A \ \ ;
= \li \ \ ;
A \ \
0 2 4 6 8 10 12 q2, dB (a)
Pt 10
err
,-1
10
10
10
10
10
10"
-2
-3
,-4
,-5
-6
\ ;
\ \ ;
\ \ ;
I \ \ ;
\ \
A \ \
0 2 4 6 8 10 12 q2, dB (b)
Fig. 5. Curves of potential noise immunity of coherent (a) and incoherent (b) reception of BPSK signals with Manchester encoding and DBPSK signals with differential Manchester encoding
Fig. 5a additionally shows calculations for the coherent reception of BPSK signals with Manchester encoding (dash-dotted line). The dashed lines correspond to the symbol-by-symbol reception of information bits of the Manchester code, the dash-dotted line correspond to calculation by the formula (7a). the solid lines correspond to calculations by the formulas (7 b) and (15). respectively, and markers correspond to modeling results.
From the analysis of the obtained graphs it follows that the modeling results confirm the expected potenti-3
schemes compared to symbol-by-symbol reception of information bits of the Manchester code.
schemes can be used in other DSITS that use DBPSK with Manchester encoding.
In addition, taking into account the using of Manchester encoding in a family of wired networking technologies known as Ethernet [2. 16]. the proposed algorithms can be modified into low-frequency demodulation algorithms by replacing the elementary radio signals —S0 cos w0t mid S0 cos w0t with bipolar signals.
The prospects for further research in this area are associated with the possibility of using other known methods of encoding the modulating signal, in particular. it's worth paying attention to such types of encoding as 3B/4B, 8B/10B and 64B/66B.
Conclusions
The implementation of decoding in a broad sense with soft decision making, in which the operations of demodulation and decoding are combined, makes it possible to reduce the bit losses of energy for the proposed demodulators compared to symbol-by-symbol processing of signals with Manchester encoding.
The obtained results allow us to assert that the proposed schemes of demodulators can be used as part of the receiving devices of DSIT. in particular to increase the noise immunity of the IsOWC and the receiving devices SpaceWire telecommunications networks for spacecraft. Also, the above demodulators
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[18] Zhuk A. P., Sazonov V. V'., Orel D. V'., Pashintsev V. P. (2019). Computer Modeling of Orthogonal in the Amplilied Sense Signal. Proceedings of the 21st International Workshop on Computer Science and Information Technologies (CS1T 2019), pp. 215 217. DOl: 10.2991/CS1T-19.2019.37.
Оптимальш когерентш й некогерентш демодулятори ФМ-2 та ВФМ-2 радю-сигнал!в 13 манчестерським кодуван-ням
Парфенюк В. Г., Сабадаш С. С., Ставгсюк Р. Л.
Заиропоповаш алгоритми та схеми оитималышх ко-герептпих i пекогерептпих демодулятор!в бшарпих ра-дюсигпашв 1з фазовою i в1дпоспою фазовою машпуля-гцею (ВФМп) та манчестерським кодуваппям модулюю-чого сигналу. Використаппя ВФМп дозволяв ефективпо боротися 1з фазовою пеодпозпачшстю генератора опорного коливаппя кореляц1йпого приймача. Дане piniemm дозволяв подолати так звапий ефект «зворотпо! роботи» в демодулятор! фазомашпульовапих сигпал1в. В1дпоспе i мапчестерське кодуваппя зпаходить свое застосувап-пя в р1зппх областях використаппя цифрових систем передаваппя 1пформац11 (ЦСП1): в!д локалышх i персо-палышх обчислюва..лы1их мереж до косм!чпих оптичпих систем зв'язку. Серед таких ЦСП1 можпа видглити як системи рад!озв'язку (в стандартах Bluetooth, в технологи NFC, а також в косм1чннх системах дистапцшпого зопдувашш Земл! (ДЗЗ) з високою розд1..лыюю здатш-стю), дротов! системи передаваппя дапих (в локалышх мережах с!мейства Etlieruet), так i оптичш системи зв'язку (FSO, IsOWC i SpaceWire). Показано, що сшльпе використаппя ВФМп i мапчестерського кодуваппя за-безпечуе б1..льш високу завадостшшсть при застосува1ш! в ЦСП1 i збер!гае переваги мапчестерського кодуваш1я стосовпо симво..лыю1 сипхрошзаци демодулятора. Наведен! алгоритми i схеми груитуються па використапш прийому в идлому i особ..лгшостей мапчестерського ко-дуваш1я. що дозволяв застосовувати для демодуляц!! повпу enepriio 61тово1 посилки. Для оцшки потмщ1й-iio'i завадост!йкост! запропоповашсс схем демодулятор!в прийпято. що модульовап! сигпали е ортогопалышми в посилепому розумпип. Проведепе математичпе моделю-ваппя запропоповашсс Texninmix piuieiu. тдтвердило i'x працездатшсть та б1..льш високу завадост!йк!сть пор!впя-по 1з посимволышм приймаппям. Пропопуеться викори-стовувати розроблеш алгоритми i схеми демодулятор!в в приймачах систем ДЗЗ високо! розд1..лыю1 здатпост!. в приймачах оптичшгх систем зв'язку i в приймальшй частит обладпаппя локальпих мереж с!мейства Etlieruet..
Клюноог слова: мапчестерське кодуваппя: ФМ-2: ВФМ-2: Etlieruet.: приймаш1я в цглому: посимвольпе приймаппя: м'яке прийпяття р1шепь: ортогопальш си-гпа..ли в посилепому розумшш
Оптимальные когерентные и некогерентные демодуляторы ФМ-2 и ОФМ-2 радиосигналов с манчестерским кодированием
Парфенюк В. Г., Сабадаш С. С., Стависюк Р. Л.
Предложены алгоритмы и схемы оптимальных когерентных и пекогерептпых демодуляторов бипарпых радиосигналов с фазовой и относительной фазовой манипуляцией (ОФМп) и манчестерским кодированием модулирующего сигнала. Использования ОФМп позволяет эффективно бороться с фазовой неоднозначностью
Оптимальш когерентш й некогерентш демодуляторе ФМ-2 та ВФМ-2 радюсигн&шв ¡з манчестерсышм кодуванням
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генератора опорного колебания корреляционного приёмника. Данное решение позволяет преодолевать так называемый эффект «обратной работы» в демодуляторе фазоманипулированных сигналов. Относительное и манчестерское кодирование находит свое применение в разных областях использования цифровых систем передачи информации (ЦСПИ): от локальных и персональных вычислительных сетей до космических оптических систем связи. Среди таких ЦСПИ можно выделить как системы радиосвязи (в стандартах Bluetooth, в технологии NFC, а также в космических системах дистанционного зондирования Земли (ДЗЗ) с высоким разрешением), проводные системы передачи данных (в локальных сетях семейства Ethernet), так и оптические системы связи (FSO, IsOWC и SpaceWïre). Показано, что совместное использование ОФМн и манчестерского кодирования обеспечивает более высокую помехоустойчивость при применении в ЦСПИ и сохраняет преимущества манчестерского кодирования касаемо символьной синхронизации демодулятора. Приведенные алгоритмы и
схемы основываются на использовании приёма в целом и особенностей манчестерского кодирования, что позволяет применять для демодуляции полную энергию битовой посылки. Для оценки потенциальной помехоустойчивости предложенных схем демодуляторов принято, что модулированные сигналы являются ортогональными в усиленном смысле. Проведенное математическое моделирование предлагаемых технических решений подтвердило их работоспособность и более высокую помехоустойчивость по сравнению с посимвольным приёмом. Предлагается использовать разработанные алгоритмы и схемы демодуляторов в приёмниках систем ДЗЗ высокого разрешения, в приёмниках оптических систем связи и в приёмной части оборудования локальных сетей семейства Ethernet.
Ключевые слова: манчестерское кодирование; ФМ-2; ОФМ-2; Ethernet; приём в целом; посимвольный приём; мягкое принятие решений; ортогональные сигналы в усиленном смысле
