Barker-like systems of sequences and their processing

New systems of binary sequences, that give the similar correlation properties after signal processing as that of the Barker sequences, are suggested and analyzed. The author considers processing of such systems, as well as ways of their application to radio systems and their comparison with compleme...

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Дата:2013
Автор: Holubnychyi, A.G.
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Опубліковано: Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України 2013
Назва видання:Технология и конструирование в электронной аппаратуре
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Цитувати:Barker-like systems of sequences and their processing / A.G. Holubnychyi // Технология и конструирование в электронной аппаратуре. — 2013. — № 6. — С. 19-24. — Бібліогр.: 7 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
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spelling irk-123456789-563932014-02-18T03:16:08Z Barker-like systems of sequences and their processing Holubnychyi, A.G. Системы передачи и обработки сигналов New systems of binary sequences, that give the similar correlation properties after signal processing as that of the Barker sequences, are suggested and analyzed. The author considers processing of such systems, as well as ways of their application to radio systems and their comparison with complementary sequences. Предложены и проанализированы новые системы бинарных последовательностей, которые дают такие же свойства функции автокорреляции после обработки сигналов, что и последовательности Баркера. Рассмотрены принцип их обработки, пути использования в радиосистемах, выполнен их сравнительный анализ с комплементарными последовательностями. Запропоновано та проаналізовано нові системи бінарних послідовностей, які дають такі ж властивості функції автокореляції після обробки сигналів, що і послідовності Баркера. Розглянуто принцип їх обробки, шляхи використання в радіосистемах, виконано їх порівняльний аналіз з комплементарними послідовностями. 2013 Article Barker-like systems of sequences and their processing / A.G. Holubnychyi // Технология и конструирование в электронной аппаратуре. — 2013. — № 6. — С. 19-24. — Бібліогр.: 7 назв. — англ. 2225-5818 http://dspace.nbuv.gov.ua/handle/123456789/56393 621.396.9 en Технология и конструирование в электронной аппаратуре Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Системы передачи и обработки сигналов
Системы передачи и обработки сигналов
spellingShingle Системы передачи и обработки сигналов
Системы передачи и обработки сигналов
Holubnychyi, A.G.
Barker-like systems of sequences and their processing
Технология и конструирование в электронной аппаратуре
description New systems of binary sequences, that give the similar correlation properties after signal processing as that of the Barker sequences, are suggested and analyzed. The author considers processing of such systems, as well as ways of their application to radio systems and their comparison with complementary sequences.
format Article
author Holubnychyi, A.G.
author_facet Holubnychyi, A.G.
author_sort Holubnychyi, A.G.
title Barker-like systems of sequences and their processing
title_short Barker-like systems of sequences and their processing
title_full Barker-like systems of sequences and their processing
title_fullStr Barker-like systems of sequences and their processing
title_full_unstemmed Barker-like systems of sequences and their processing
title_sort barker-like systems of sequences and their processing
publisher Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
publishDate 2013
topic_facet Системы передачи и обработки сигналов
url http://dspace.nbuv.gov.ua/handle/123456789/56393
citation_txt Barker-like systems of sequences and their processing / A.G. Holubnychyi // Технология и конструирование в электронной аппаратуре. — 2013. — № 6. — С. 19-24. — Бібліогр.: 7 назв. — англ.
series Технология и конструирование в электронной аппаратуре
work_keys_str_mv AT holubnychyiag barkerlikesystemsofsequencesandtheirprocessing
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fulltext Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 19 SIGNALS TRANSFER AND PROCESSING SYSTEMS UDC 621.396.9 A. G. HOLUBNYCHYI, Ph.D. (Eng.) Ukraine, Kyiv, National Aviation University E-mail: a.holubnychyi@nau.edu.ua BARKER-LIKE SYSTEMS OF SEQUENCES AND THEIR PROCESSING Barker sequences (codes) are generally well known in telecommunication systems (DSSS tech nology, synchronization) and radar techno- logy. They are characterized by low sidelobes of normalized autocorrelation function (ACF) |RSL(τ)| ≤ 1/N (N is the length of sequence) [1]. Binary Barker sequences (elements ai ∈ {±1}) are only known for lengths N = 2; 3; 4; 5; 7; 11; 13. There are no these sequences for odd lengths N > 13, but it is unknown about an existence of these sequences for even lengths N > 4 [2, p. 109]. Ternary Barker sequences (elements ai ∈ {0, ±1}) are also known up to length N = 31 [3, p. 23]. There is a known kind of sequences called “Generalized Barker Sequences (Codes)”, they are polyphase sequences which consist of ele- ments ai ∈ {exp(j⋅2πk/M)}, k≤M [4]. Polyphase Barker sequences are known up to length N = 77 [5]. The problem boils down to a controversy con- cerning the existence of sequences or systems of sequences with a greater length that would make it possible to obtain after their processing an ACF- signal with a low value of side lobes and a narrow central-lobe (as that of the Barker sequences). One of the solutions of this problem is the complemen- tary sequences [6]. They are pairs of sequences of lengths N = 2n⋅10k⋅26m (n ≥ 0, k ≥ 0, m ≥ 0; except for the case n = k = m = 0) with a property that the result of adding of sidelobes of their ACF is equal to zero. Complementary sequences are used in pulse compression radar systems, telecommu- nication systems IEEE 802.11b/g and other ap- plications. Although the complementary sequences are a good technical solution, the optimal ACF structure synthesis problem still hasn’t been solved in general, and there may be some other kinds of sequences that can, for instance, provide better noise stability of radio systems and consistency with some digital modulation techniques, e.g., QAM. New systems of binary sequences, that give the similar correlation properties after signal processing as that of the Barker sequences, are suggested and analyzed. The author considers processing of such systems, as well as ways of their application to radio systems and their comparison with complementary sequences. Keywords: Barker sequences, complementary sequences, correlation properties, sidelobe suppression, signal processing. This research is a continuation of the research described in [7] and concerns the problem of syn- thesis of the optimal ACF structure. The goal of this study is to suggest new systems of binary se- quences (generation rules for such sequences) and their application in signal processing, which would make it possible to obtain ACF-signals with the maximum normalized absolute value of sidelobes 1/Nmax (as that of the Barker sequences), where Nmax is the maximum length of sequence in the system of sequences. Systems of Barker-like Sequences Systems of sequences being suggested consist of the Barker sequence a = {–1; 1; –1; –1; –1} (length N = 5) and binary sequences of lengths N = 20⋅2q, q = 0, 1, 2, 3, ..., which can be ob- tained by using the generation rule – , ; (– ) , ; (– ) , ; , – , – ; – , , – ; ,( / – ); , / . for subtype for subtype for subtype for subtype a i i m a i n a A a B i N n a A a B i N n m N n N 1 1 1 2 1 1 2 1 2 2 2 1 4 1 1 4 – – – i m n n n n n n 2 1 2 2 2 1 2 1 = = = + = = + = + = = Z [ \ ] ] ] ] ]] ] ] ] ] ] ) ) (1) Such systems of sequences allow to obtain, after the joint signal processing (considered below), an ACF-signal with the maximum normalized abso- lute value of sidelobes 1/Nmax, which would match to the maximum value of sidelobes in a Barker sequence of length Nmax, if it existed. Therefore, such systems of sequences may be called “Barker- like systems of sequences”. Such system can contain subtype A or subtype B sequences (signs of some ACF sidelobes depend Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 20 SIGNALS TRANSFER AND PROCESSING SYSTEMS on the subtype, but their absolute values do not depend on the subtype). Generation rule (1) generally gives binary se- quences of lengths N = 4k, k = 1, 2, 3, ..., but in our case only lengths N = 20⋅2q, q = 0, 1, 2, 3, ... are required. The ACF of sequences that have been obtained by (1) is partly presented for certain τ values and N ≥ 12 in ( ) , ; 1 , –1 , , ; , , , – ; – , . for subtype for subtypeR N A B m m N N 0 1 3 0 2 4 0 4 1 16 4 τ τ τ τ τ = = = = + = = ` j Z [ \ ] ] ] ] ]] ) (2) It is important that the central lobe of ACF R(0) = N is always separated from the first high sidelobe by low sidelobes (0 or ±1); high sidelobes are concentrated between zero sidelobes (at τ = 2 + 4m, m = 0, 1, 2, 3, ...). The structure of sequences which have been obtained by (1) is shown in Fig. 1. Signal processing and ways of using Barker- like systems of sequences Signal processing and ways of application of the suggested systems of sequences are based on the following property of the systems: the result of multiplication of ACF-signals (at the outputs of matched filters), that exist at the same time interval and match to these sequences, constitutes a signal that is similar to the ACF-signal with a narrow central-lobe (equals to the duration of the Fig. 1. Structure of suggested subtype А (a) and subtype В (b) sequences a) b) Fig. 2. Signals in the considered example of Barker-like system of sequences U1(t) 1 –1 U2(t) 1 –1 0 4 8 12 16 t 0 2 4 6 8 10 12 14 16 18 t Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 21 SIGNALS TRANSFER AND PROCESSING SYSTEMS Fig. 3. Matched filters for sequences N1=5 (a) and N2=20 (b) Fig. 4. Forms of signals after MF for sequences N1=5 (a) and N2=20 (b), and the result of their multiplication (c) a) b) inverter delay line a) b) c) Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 22 SIGNALS TRANSFER AND PROCESSING SYSTEMS Fig. 5. Signal processing of Barker-like systems of sequences shortest element of sequences in all the system) and low sidelobes (normalized absolute values do not exceed 1/Nmax). Let us take a detailed look at signal processing by using the example of the Barker-like system consisting of two sequences {–1; 1; –1; –1; –1} (N1 = 5, Barker sequence) and {–1; 1; –1; –1; 1; –1; –1; –1; 1; –1; –1; –1; –1; 1; –1; –1; –1; 1; 1; 1} (N2 = 20, sequence of subtype A). In Fig. 2 are shown signals for those sequences (the same time interval, e. g. 20 µs, is used). Matched filters (MF) for signals of each sequence are shown in Fig. 3, and ACF-signals after the matched filters and the result of their multiplication (central-lobes of ACF-signals are reduced to the zero moment) are illustrated in Fig. 4. In the case of the suggested systems of sequences the multiplication of ACF makes it possible to combine their advantages (low sidelobes of ACF1 and narrow central-lobe of ACF2) and neutralize their disadvantages (wide central-lobe of ACF1 and high sidelobes of ACF2). It is possible because the ACF of suggested sequences has a comb structure: the central-lobe is always separated from the first high sidelobe by low sidelobes (0 or ±1) — this results in the appearance of a narrow central-lobe after multiplication. High sidelobes are also sepa- rated from one another by zero sidelobes. Thus low and high sidelobes of different ACFs are partially or totally cross-thinned — this leads to partial or total sidelobe suppression. Characteristics of some of the suggested Barker- like systems of sequences (data are confirmed by computer modeling) are given in Table 1. Theoretical justification of the fact, that the maximum normalized absolute value of ACF sidelobes is 1/Nmax for any possible number of sequences in a system, is expected in further re- search. Using the Barker sequence of length N = 5 in the suggested systems is important for the considered case, because if other basic binary Barker sequence (e.g., N=13) and system (e.g., N1=13 and N2=52) were used, the resultant maximum normalized absolute value of sidelobes wouldn’t be 1/Nmax (for the case N1=13 and N2=52 it would be 7/169, which is more than 1/Nmax = 1/N2 = 1/52). In Fig. 5 is shown the signal processing system for Barker-like systems of sequences. Delay lines (2q+1 – 0.5)τq+2 in this system are used to align in time the centers of the central lobes. In Table 2 an example of possible modulation scheme for DSSS technology is shown. In this example we have used the system of sequences N1=5 and N2=20 and QPSK modulation with Gray coding. In our example, for correct operation of the signal processing system in a DSSS-transmitter, to transmit Table 1 Characteristics of some of the suggested Barker-like systems of sequences Sequences in the system Central-lobe width of ACF in the result of multiplication Maximum normalized value of sidelobes of ACF in the result of multiplication Example of the suitable modulation N1 = 5 and N2 = 20 TS /20 1/20 QPSK N1 = 5, N2 = 20 and N3 = 40 TS /40 1/40 8-PSK N1 = 5, N2 = 20, N3 = 40 and N4 = 80 TS /80 1/80 16-PSK or 16-QAM N1 = 5, N2 = 20, N3 = 40, N4 = 80 and N5 = 160 TS /160 1/160 32-QAM N1 = 5, N2 = 20, N3 = 40, N4 = 80, N5 = 160 and N6 = 320 TS /320 1/320 64-QAM TS – signal duration. T 20 2 –w w S 2$ τ = (2q+1–0.5)τq+2 Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 23 SIGNALS TRANSFER AND PROCESSING SYSTEMS a zero bit, it is necessary to invert only one chip flow, which matches to the sequence N2 = 20; the chip flow for the sequence N1 = 5 is constant and doesn’t depend on the bit value. Generally, in such systems may be inverted a certain odd number of chip flows, but not more than the total number of these flows. Comparison of Barker-like systems of sequences with complementary sequences One of the nearest analogs of the suggested Barker-like sequences are the complementary sequences. Their comparison is shown in Table 3. Thus, by the criterion of value of ACF sidelobes after signal processing, the proposed systems of sequences are slightly inferior to known comple- mentary sequences and equal to Barker sequences. Another important factor in the application of the proposed systems of sequences is noise stability of a telecommunication or radar system. In the case of application of such systems of sequences, after signal processing non-stationary noise tends to ap- pear if stationary noise is at the input (unlike com- plementary systems, where after signal processing the stationary noise appears). However, multipli- cation of useful signals during signal processing (used for Barker-like systems of sequences) may give better noise stability than adding of useful signals (used for complementary systems). The issue of noise stability when using the suggested Barker-like systems of sequences will be addressed in further research. Conclusions The proposed systems of binary sequences and signal proces sing using such systems make it possible to obtain ACF-signals with the same maximum normalized absolute value of sidelobes as the one for the Barker sequences. It has been established using computer modeling, that the maximum length of binary sequences of such systems is at least 320. Comparison of the suggested sequences with the known complementary sequences shows that Bit 1 0 Chips (N1=5) –1 1 –1 –1 –1 –1 1 –1 –1 –1 Chips (N2=20) -1 1 -1 -1 1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 1 1 1 1 -1 1 1 -1 1 1 1 -1 1 1 1 1 -1 1 1 1 -1 -1 -1 QPSK phases π 4 3π 4 π 4 π 4 5π 4 7π 4 7π 4 7π 4 3π 4 π 4 π 4 π 4 π 4 3π 4 π 4 π 4 π 4 3π 4 3π 4 3π 4 3π 4 π 4 3π 4 3π 4 7π 4 5π 4 5π 4 5π 4 π 4 3π 4 3π 4 3π 4 3π 4 π 4 3π 4 3π 4 3π 4 π 4 π 4 π 4 Table 2 Example of using of the considered sequences in DSSS Table 3 Comparison of Barker-like systems of sequences with complementary sequences Parameter Barker-like systems of sequences Complementary sequences The main principle of signal processing Multiplication of results of matched filtering of each sequence Adding of results of matched filtering of each sequence Quantity of sequences in the system L ≥ 2 L = 2 Lengths of sequences in the system N1 = 5 (Barker) Nw = 20⋅2w–2, w = 2, ..., L N1 = N2 = 2n⋅10k⋅26m, n ≥ 0, k ≥ 0, m ≥ 0, except for the case n = k = m = 0 Maximum normalized value of sidelobes of ACF in the result of signal processing 1/(20⋅2L–2) 0 Central-lobe width in the result of signal processing TS/NL TS/N1 Suitable modulation 2L-level shift keying modulation (e.g., 64-QAM for L = 6) 4-level shift keying modulation (e.g., QPSK) Òåõíîëîãèÿ è êîíñòðóèðîâàíèå â ýëåêòðîííîé àïïàðàòóðå, 2013, ¹ 6 24 SIGNALS TRANSFER AND PROCESSING SYSTEMS both this types are complementary, but matched filtering results in the case of the proposed sequences are multiplied, while for the known sequences the results are added. Due to their properties after signal processing, the suggested systems of sequences can be used in the pulse-compression radar technology, in synchro nizing system, and in DSSS technology for wideband signal forming and data transfer. REFERENCES 1. Barker R. H. Group synchronizing of binary digital sequences. Communication Theory, London, Butterworth, 1953, pp. 273–287. 2. Babak V. P., Bilets`kii A. Ya. [Deterministic signals and spectra] Kiev: Tekhnika, 2003. (in Russian) [Бàбàê В. П., Білецький А. Я. Детерміновані сигнали і спектри.– Кèїâ: Òåõíіêà, 2003] 3. Gantmakher V. E., Bystrov N. E., Chebotarev D.V. Noise-like signals. Analysis, synthesis, processing, St-Petersburg, Nauka i tekhnika, 2005. [Гàíòмàõåð В. Е., Быñòðîâ Н. Е., Чåбîòàðåâ Д.В. Шóмîïîдîбíыå ñèãíàëы. Анализ, синтез, обработка.– Санкт-Петербург: Наука и òåõíèêà, 2005] 4. Golomb S. W., Scholtz D. A. Generalized Barker Sequences. IEEE Trans. on Inf. Theory, 1965, vol. 11, no 4, pp. 533–537. DOI: 10.1109/TIT.1965.1053828 5. Nunn C. J., Coxson G. E. Polyphase pulse compression codes with optimal peak and integrated sidelobes. IEEE Trans. on Aerospace and Electronics Systems, 2009, vol. 45, no 2, pp. 775–781. DOI: 10.1109/TAES.2009.5089560. 6. Turyn R. J. Hadamard matrices, Baumert-Hall units, four-symbol sequences, pulse compression, and surface wave encodings. Journal of Combinatorial Theory (Series A), 1974, vol. 16, no 3, pp. 313–333. DOI: 10.1016/0097- 3165(74)90056-9. 7. Holubnychyi A. Generalized binary Barker sequences and their application to radar technology. Proc. of the Signal Processing Symposium (SPS-2013), Poland, Jachranka, 2013, pp. 1–9. DOI: 10.1109/SPS.2013.6623610. Received 05.09 2013 О. Г. ГОЛУБНИЧИЙ Уêðàїíà, м. Кèїâ, Нàціîíàëьíèé àâіàціéíèé óíі âåðñèòåò E-mail: a.holubnychyi@nau.edu.ua БАРКЕРОПОДІБНІ СИСТЕМИ ПОСЛІ ДОВНОСТЕЙ ТА ЇХ ОБРОБКА Запропоновано та проаналізовано нові системи бінарних послідовностей, які дають такі ж властивості функції автокореляції після обробки сигналів, що і послідовності Баркера. Розглянуто принцип їх об- робки, шляхи використання в радіосистемах, виконано їх порівняльний аналіз з комплементарними послідовностями. Ключові слова: послідовності Баркера, комплементарні послідовності, кореляційні властивості, приду- шення бічних пелюсток, обробка сигналів. А. Г. ГОЛУБНИЧИЙ Уêðàèíà, ã. Кèåâ, Нàцèîíàëьíыé àâèàцèîííыé óíèâåðñèòåò E-mail: a.holubnychyi@nau.edu.ua БАРКЕРОПОДОБНЫЕ СИСТЕМЫ ПОСЛЕДОВАТЕЛЬНОСТЕЙ И ИХ ОБРАБОТКА Предложены и проанализированы новые системы бинарных последовательностей, которые дают такие же свойства функции автокорреляции после обработки сигналов, что и последовательности Баркера. Рассмотрены принцип их обработки, пути использования в радиосистемах, выполнен их сравнительный анализ с комплементарными последовательностями. Ключевые слова: последовательности Баркера, комплементарные последовательности, корреляционные свойства, подавление боковых лепестков, обработка сигналов.