RU2575402C2 - Method of generating in-phase and quadrature components of complex envelope of spectral-efficient radio signals - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to methods of generating radio signals with spectral-efficient modulation types (FBPSK, T-OQPSK, FQPSK, GMSK, FQAM), which are widely used in setting up space information transmission and control radio links. A method of generating in-phase and quadrature components of a complex envelope of spectral-efficient radio signals comprises generating, based on a source transmitted information stream, {x_l} multi-position symbols of in-phase (d_Ii) and quadrature (d_Qi) channels depending on a given modulation mode; generating, through corresponding processing, corresponding sequences of the multi-position symbols d_Ii and d_Qi based on I₁(t) and Q₁(t) signals of the corresponding channels, responsible for the transfer of the said sequences of symbols, additional I₂(t) and Q₂(t) of the corresponding channels, responsible for the intersymbol interference of the said sequences of symbols, and special I'₃(t) and Q'₃(t) signals of the corresponding channels, responsible for communication between the said components of the complex envelope of spectral-efficient radio signals with the synchronisation of moments thereof, and calculating the in-phase I(t) and quadrature Q(t) components of the generated spectral-efficient radio signal in the form of a weighted sum of the said signals of the corresponding channels with two weight coefficients which determine noise-immunity and spectral characteristics of the generated spectral-efficient signal.

EFFECT: enabling the generation of in-phase and quadrature components of the complex envelope of the listed types of spectral-efficient radio signals, as well as 16-position radio signals.

1 tbl

Description

The present invention relates to the field of radio engineering, and in particular, to methods for generating radio signals with spectrally efficient types of modulation, in particular, such as Gaussian minimum frequency shift keying (GMSK), quadrature phase shift keying with quadrature channel offset and trellis coding (T-OQPSK) and special quadrature phase shift keying developed by Dr. C. Feer (FQPSK), which are widely used in the organization of space radio control lines and information transfer.

At present, spectral-efficient types of radio signals, in particular GMSK, T-OQPSK, and FQPSK signals, are widely used for organizing space radio control and information transmission lines [1, 2]. In the framework of [2 ... 4], it was shown that radio signals with GMSK and FQPSK can be considered as OQPSK signals with a specially introduced coupling between in-phase and quadrature components. Moreover, this connection in the case of FQPSK signals is due to a nonlinear element of the “hard limiter” type, and in the case of GMSK signals and other types of signals with continuous phase modulation (CPM), by means of additional pulse sequences. In addition, FSOQ radio signals with relatively high spectral efficiency are known, also based on the relationship between the in-phase and quadrature components of the complex envelope introduced by a special encoding device [5].

A device for the formation of spectrally effective radio signals with FQPSK [6]. The device uses a tabular method of generating in-phase and quadrature components of the radio signals, followed by increasing the frequency through a quadrature modulator. In this case, the main blocks of the device are a serial-parallel data converter, a delay element, a memory block and a multiplexer. The first of these blocks separates the transmitted information stream into the in-phase and quadrature channels. The delay element performs a time shift of the quadrature channel signal by half a symbol interval. The memory block stores possible implementations of the in-phase and quadrature components. The multiplexer, in accordance with the information flows of the in-phase and quadrature channels arriving at its input, selects the necessary cells in the memory block to implement the desired digital modulation scheme. Further, the components of the complex envelope thus obtained are fed to the input of the quadrature modulator, where the final formation of the desired radio signal takes place.

The disadvantage of this device is, firstly, the relatively low decay rate of out-of-band radiation (40 dB / dec) due to gaps in the implementation of the first derivative of the complex envelope of the radio signal, and secondly, the inability to implement radio signals with other spectrally effective types of modulation, such like GMSK, TFM and other varieties of CPM.

A known GMSK modulation scheme based on the representation of a radio signal in the form of a linear combination of phase-shifted radio signals formed by elementary pulses of a special form C ₀ (t) and C ₁ (t) [3, 4]. This scheme includes an encoding device that separates, according to a certain rule, the transmitted information sequence into four streams — the main and additional streams of the in-phase and quadrature channels. Further, the generated information sequences are fed to pre-modulation filters with impulse characteristics of the form C ₀ (t) and C ₁ (t). In this case, the main information flows are modulated by the pulse C ₀ (t), and the additional ones by the pulse C ₁ (t). After that, a delay by the value of the bit interval is introduced into the components of the quadrature channel. Next, the main and additional components of the in-phase and quadrature channels are combined in pairs. The two signals obtained in this way are fed to a quadrature modulator, where the radio signal with GMSK is directly generated.

The disadvantage of this approach is, firstly, the dependence of the shape of the elementary pulses C ₀ (t) and C ₁ (t) on the bandwidth of the pre-modulation Gaussian filter, as a result of which, in practice, the change in the spectral efficiency of the information transmission radio line is accompanied by the need to recalculate these time functions. Secondly, this device does not allow the direct implementation of radio signals with FQPSK.

The closest set of features to the proposed method is a method of forming spectrally effective radio signals based on a controlled connection between in-phase and quadrature components [7]. This approach is based on the presentation of radio signals based on three OQPSK signals. The first component (I ₁ (t); Q ₁ (t)) is responsible for the transmission of information, the second (I ₂ (t); Q ₂ (t)) is responsible for the depth of intersymbol communication, and the third (I ₃ (t); Q ₃ (t)) - for the relationship between the in-phase and quadrature components of the complex envelope. In this case, the formation of the first and second components is carried out on the basis of the same information sequences using, respectively, elementary pulses p ₁ (t) and p ₂ (t):

$$p_{\mathrm{one}}\left(t\right)={\sin }^2\left(\pi t/\left(2T_S\right)\right)\cdot rect\left(t/\left(2T_S\right)\right)\left(\mathrm{one}\right)$$

$$p_2\left(t\right)={\sin }^2\left(\pi t/\left(T_S\right)\right)\cdot rect\left(t/\left(2T_S\right)\right)\left(2\right)$$

where T _S is the character interval, rect (u) = 1 for u∈ [0; 1) and rect (u) = 0 for u∉ [0; 1). To obtain the third component, the following expressions are used [7]:

, $$Q_3\left(t\right)=sign\left(Q_1\left(t\right)\right)\left|I_2\left(t\right)\right|$$

, $$I_3(t)=sign(I_{\mathrm{one}}\left(t\right))\cdot \left|Q_2\left(t\right)\right|$$

, $$Q_3\left(t\right)=sign\left(Q_{\mathrm{one}}\left(t\right)\right)\left|I_2\left(t\right)\right|$$

,

- функция определения знака аргумента. Подобный подход к представлению спектрально-эффективных радиосигналов позволяет в одном устройстве объединить формирователи GMSK, TFM, T-OQPSK и FQPSK-сигналов. При этом основные спектральные и энергетические характеристики регулируются посредством двух коэффициентов, определяющих вес второй и третьей компонент при формировании радиосигнала.Where

- function to determine the sign of the argument. Such an approach to the representation of spectrally efficient radio signals makes it possible to combine GMSK, TFM, T-OQPSK and FQPSK signals in one device. In this case, the main spectral and energy characteristics are regulated by two coefficients that determine the weight of the second and third components during the formation of the radio signal.

A disadvantage of the known device is the presence of gaps in the complex envelope of the signal when implementing multi-position modulation schemes, in particular when generating sixteen-position radio signals. In turn, this fact increases the level of out-of-band emissions and reduces the spectral efficiency of the corresponding space radio control and information transmission lines.

The proposed method allows to eliminate this drawback and to eliminate gaps in the generated in-phase and quadrature components of the complex envelope of various spectrally effective radio signals, including sixteen position signals.

The technical result of the invention is the ability to form in-phase and quadrature components of the complex envelope of such types of spectrally effective radio signals as FBPSK, T-OQPSK, FQPSK, GMSK, including sixteen-position radio signals.

и $$Q_3^{\text{'}}\left(t\right)$$

, описываемые выражениями:The technical result is achieved by synchronizing the moments of the change of signs and reducing the absolute value of the components I ₃ (t) and Q ₃ (t) to zero. The proposed method for generating the in-phase and quadrature components of the complex envelope of spectrally effective radio signals, in contrast to the prototype, provides the necessary synchronization through the proposed procedure for obtaining signals responsible for the relationship between the in-phase and quadrature components of the complex envelope. That is, instead of the signals I ₃ (t) and Q ₃ (t) in the proposed method, the components are used $$I_3^{\text{'}\text{'}}\left(t\right)$$

and $$Q_3^{\text{'}\text{'}}\left(t\right)$$

described by the expressions:

$$I_3^{\text{'}\text{'}}\left(t\right)=I_S\left(t\right)\cdot \left|Q_2\left(t\right)\right|,Q_3^{\text{'}\text{'}}\left(t\right)=Q_S\left(t\right)\left|I_2\left(t\right)\right|.\left(3\right)$$

Here, the components I _S (t) and Q _S (t) are calculated according to the formulas:

, $$Q_S\left(t\right)={\displaystyle \sum _{i=0}^{N_Q-1}sign\left(d_{Qi}\right)rect\left(t-i{T}_S\right)}$$

, $$I_S\left(t\right)={\displaystyle \sum _{i=0}^{N_I-\mathrm{one}}sign\left(d_{Ii}\right)rect\left(t-\left(i+0.5\right)T_S\right)}$$

, $$Q_S\left(t\right)={\displaystyle \sum _{i=0}^{N_Q-\mathrm{one}}sign\left(d_{Qi}\right)rect\left(t-i{T}_S\right)}$$

,

where d _Ii , d _Qi are the multi-position symbols of the in-phase and quadrature channels transmitted over the in-phase and quadrature channels, respectively, N _I , N _Q are the number of symbols of the in-phase and quadrature channels, respectively.

, где N_b - количество передаваемых бит) побитно поступает на кодирующее устройство, в котором производится выделение слов и формирование потоков синфазного {d_Ii} $$(i=\overline{0;\left(N_I-1\right))}$$

и квадратурного {d_Qi} $$(i=\overline{0;\left(N_Q-1\right))}$$

каналов. При этом в зависимости от заданного режима модуляции процедура кодирования описывается одной из формул:Thus, the proposed method for the formation of in-phase and quadrature components of the complex envelope of spectrally effective radio signals is as follows. Source Information Sequence {x _l } ( $$l=\overline{0;\left(N_b-\mathrm{one}\right)}$$

, where N _b is the number of transmitted bits) is bitwise transmitted to an encoding device in which words are extracted and common-mode flows are generated {d _Ii } $$(i=\overline{0;\left(N_I-\mathrm{one}\right))}$$

and quadrature {d _Qi } $$(i=\overline{0;\left(N_Q-\mathrm{one}\right))}$$

channels. Moreover, depending on the given modulation mode, the encoding procedure is described by one of the formulas:

for FBPSK

, N_I=N_Q=N_b;d _Ii = 1-2x _i , d _Qi = d _Ii , $$\forall i=\overline{0;\left(N_b-\mathrm{one}\right)}$$

, N _I = N _Q = N _b ;

for gmsk

, $$i=\overline{0;\left(N_I-1\right)}$$

$$d_{Ii}={\left(-\mathrm{one}\right)}^i\left(\mathrm{one}-2{\displaystyle \sum _{l=0}^{2i-\mathrm{one}}{x}_l\left(\mathrm{mod}2\right)}\right)$$

, $$i=\overline{0;\left(N_I-\mathrm{one}\right)}$$

, $$i=\overline{0;\left(N_Q-1\right)}$$

$$d_{Qi}={\left(-\mathrm{one}\right)}^i\left(\mathrm{one}-2{\displaystyle \sum _{l=0}^{2i}{x}_l\left(\mathrm{mod}2\right)}\right)$$

, $$i=\overline{0;\left(N_Q-\mathrm{one}\right)}$$

N _I = N _b / 2, N _Q = N _b / 2, x _-1 = 0

for T-OQPSK, FQPSK

,d _Ii = 1-2x _2i , $$\forall i=\overline{0;\left(N_I-\mathrm{one}\right)}$$

,

,d _Qi = 1-2x _{2i + 1} $$\forall i=\overline{0;\left(N_Q-\mathrm{one}\right)}$$

,

N _I = N _b / 2, N _Q = N _b / 2;

for FQAM

,d _Ii = 3-2 (x _4i + 2x _{4i + 1} ), $$\forall i=\overline{0;\left(N_I-\mathrm{one}\right)}$$

,

,d _Qi = 3-2 (x _{4i + 2} + 2x _{4i + 3} ) $$\forall i=\overline{0;\left(N_Q-\mathrm{one}\right)}$$

,

N _I = N _Q = N _b / 2, and the missing bits in the original sequence are replaced by zeros.

в соответствии с выражениями:Next, the multi-position symbols of the in-phase and quadrature channels are fed to pre-modulation filters with impulse response p ₁ (t) (see formula (1)), where signals I ₁ (t) and $$Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t\right)$$

in accordance with the expressions:

; $$I_{\mathrm{one}}\left(t\right)={\displaystyle \sum _{i=0}^{N_I-\mathrm{one}}{d}_{Ii}{p}_{\mathrm{one}}\left(t-i{T}_S\right)}$$

;

, $$Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t\right)={\displaystyle \sum _{i=0}^{N_Q-\mathrm{one}}{d}_{Qi}{p}_{\mathrm{one}}\left(t-i{T}_S\right)}$$

,

в соответствии с выражениями:In parallel with this, the multi-position symbols of the in-phase and quadrature channels also arrive at pre-modulation filters with an impulse response p ₂ (t) (see formula (2)), where I ₂ (t) and $$Q_2^{\text{'}\text{'}}\left(t\right)$$

in accordance with the expressions:

, $$I_2\left(t\right)={\displaystyle \sum _{i=0}^{N_I-\mathrm{one}}{d}_{Ii}{p}_2\left(t-i{T}_S\right)}$$

,

, $$Q_2^{\text{'}\text{'}}\left(t\right)={\displaystyle \sum _{i=0}^{N_Q-\mathrm{one}}{d}_{Qi}{p}_2\left(t-i{T}_S\right)}$$

,

и дополнительный $$Q_2^{\text{'}}\left(t\right)$$

сигналы квадратурного канала поступают на элементы задержки, где осуществляется временной сдвиг этих составляющих на величину T_S/2, в результате чего получаются сигналы Q₁(t) и Q₂(t):After that the main $$Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t\right)$$

and additional $$Q_2^{\text{'}\text{'}}\left(t\right)$$

the signals of the quadrature channel arrive at the delay elements, where the time shift of these components by the value of T _S / 2 is carried out, as a result of which the signals Q ₁ (t) and Q ₂ (t) are obtained:

, $$Q_1\left(t\right)=Q_1^{\text{'}}\left(t-T_S/2\right)$$

. $$Q_2\left(t\right)=Q_2^{\text{'}\text{'}}\left(t-T_S/2\right)$$

, $$Q_{\mathrm{one}}\left(t\right)=Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t-T_S/2\right)$$

.

Multiposition symbols of the in-phase and quadrature channels are fed to blocks that perform the function of taking a sign (i.e., the function sign ()), and then to pre-modulation filters with the characteristic rect (t / T _S ). These transformations are mathematically described by expressions of the form:

, $$I_S^{\text{'}\text{'}}\left(t\right)={\displaystyle \sum _{i=0}^{N_I-\mathrm{one}}sign\left(d_{Ii}\right)rect\left(t-i{T}_S\right)}$$

,

. $$Q_S\left(t\right)={\displaystyle \sum _{i=0}^{N_Q-\mathrm{one}}sign\left(d_{Qi}\right)rect\left(t-i{T}_S\right)}$$

.

смещается во времени на половину символьного интервала T_S/2, в результате чего формируется сигнал I_S(t):Next signal $$I_S^{\text{'}\text{'}}\left(t\right)$$

is shifted in time by half the symbol interval T _S / 2, as a result of which a signal I _S (t) is formed:

$$I_S\left(t\right)=I_S^{\text{'}\text{'}}\left(t-T_S/2\right)$$

и $$\left|I_2\left(t\right)\right|$$

перемножаются соответственно с компонентами I_S(t) и Q_S(t) согласно выражениям (3). В результате данных операций получаются составляющие $$I_3^{\text{'}}\left(t\right)$$

и $$Q_3^{\text{'}}\left(t\right)$$

.The components I ₂ (t) and Q ₂ (t) have the function of determining the modulus of a number, and the signals thus obtained $$\left|Q_2\left(t\right)\right|$$

and $$\left|I_2\left(t\right)\right|$$

multiplied respectively with the components I _S (t) and Q _S (t) according to expressions (3). As a result of these operations, components are obtained $$I_3^{\text{'}\text{'}}\left(t\right)$$

and $$Q_3^{\text{'}\text{'}}\left(t\right)$$

.

After that, the required in-phase and quadrature components of the complex envelope of the generated spectrally-efficient radio signal are calculated according to the expressions:

, $$I\left(t\right)=I_{\mathrm{one}}\left(t\right)-0.5\left(\mathrm{one}-A_{\mathrm{one}}\right)I_2\left(t\right)-0.5\left(\mathrm{one}-A_2\right)I_3^{\text{'}\text{'}}\left(t\right)$$

,

, $$Q\left(t\right)=Q_{\mathrm{one}}\left(t\right)-0.5\left(\mathrm{one}-A_{\mathrm{one}}\right)Q_2\left(t\right)-0.5\left(\mathrm{one}-A_2\right)Q_3^{\text{'}\text{'}}\left(t\right)$$

,

where A ₁ , A ₂ - weighting factors that are responsible for the spectral and energy characteristics of the signals and when implementing known types of modulation should be selected based on the table.

Since the spectral and energy characteristics of the spectrally effective radio signals generated by the proposed method are determined only by the values of the weight coefficients A ₁ , A ₂ , it is possible to generate new, unknown signals that combine parameters of various known types of modulation.

Bibliography

1. Report Concerning Space Data System Standards. Bandwidth-Efficient Modulations: Summary of Definition, Implementation, and Performance. Green Book. Issue 2. October 2009. - URL: http://public.ccsds.org/publications/archive/413x0g2.pdf.

2. Feer K. Wireless digital communications. Modulation and spreading methods. - M .: Radio and communications, 2000 .-- 520 p.

3. Kaleh G.K. Simple Coherent Receivers for Partial Response Continuous Phase Modulation // IEEE Journal on Selected Areas in Communications. Vol. 7, No. 9. Dec. 1989. P. 1427-1436.

4. Simon M.K. Bandwidth-Efficient Digital Modulation with Application to Deep-Space Communications. - JPL Publication 00-17, June 2001 .-- 237 p.

5. US Patent No. 4,338,579 H04L 27/12 - Frequency Shift Offset Quadrature Modulation and Demodulation.

6. US patent No. 4567602 H03K 1/02 - Correlated Signal Processor.

7. Kirillov C.H., Pokrovsky P.S. Software-controlled shaper of radio signals with non-linear types of modulation // Nonlinear World, No. 3, 2013. P. 150-157.

Claims (1)

The method of forming in-phase and quadrature components of the complex envelope of spectrally effective radio signals, which consists in the following steps:
- the formation on the basis of the initial transmitted information stream {x _l } of multi-position symbols in-phase (d _Ii ) and quadrature (d _Qi ) channels, depending on the given modulation mode;
- the formation in pre-modulation filters with impulse response p ₁ (t), which receive the corresponding multi-position symbols d _Ii and d _Qi , the main signals in-phase I ₁ (t) and quadrature $$Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t\right)$$

channels responsible for transferring the corresponding sequences of multi-position symbols d _Ii and d _Qi ;
- parallel formation in pre-modulation filters with impulse response p ₂ (t), which receive the corresponding multi-position symbols d _Ii and d _Qi , additional common-mode signals I ₂ (t) and quadrature $$Q_2^{\text{'}\text{'}}\left(t\right)$$

responsible for the intersymbol interference of the corresponding sequences of multi-position symbols d _Ii and d _Qi ;
- receiving signals Q ₂ (t) and Q ₁ (t) as a result of a time shift of half the symbol interval T _S / 2, respectively, additional $$Q_2^{\text{'}\text{'}}\left(t\right)$$

and main $$Q_{\mathrm{one}}^{\text{'}\text{'}}\left(t\right)$$

quadrature channel signals in delay elements;
- the formation in pre-modulation filters with the characteristic rect (t / T _S ), to which the corresponding multi-position symbols d _Ii and d _Qi , through common-mode signals, come in through the character determination blocks $$I_S^{\text{'}\text{'}}\left(t\right)$$

and quadrature Q _S (t) channels;
- the formation of the signal I _S (t) as a result of a time shift of half the symbol interval T _s / 2 auxiliary signal $$I_S^{\text{'}\text{'}}\left(t\right)$$

common mode channel;
- receiving special signals $$I_3^{\text{'}\text{'}}\left(t\right)$$

and $$Q_3^{\text{'}\text{'}}\left(t\right)$$

responsible for the relationship between the in-phase and quadrature components of the complex envelope of spectrally effective radio signals, with the synchronization of their moments of sign change and absolute value by multiplying the signals I _S (t) and Q _S (t) by the modulated signals Q ₂ (t) and I ₂ (t), respectively;
- calculation of the in-phase I (t) and quadrature Q (t) components of the complex envelope of the generated spectrally effective radio signal by weighted summation of the main I ₁ (t) and Q ₁ (t), additional I ₂ (t) and Q ₂ (t), as well as special $$I_3^{\text{'}\text{'}}\left(t\right)$$

and $$Q_3^{\text{'}\text{'}}\left(t\right)$$

signals, respectively, in-phase and quadrature channels with weighting factors A ₁ and A ₂ determining the noise immunity and spectral characteristics of the generated spectrally-efficient radio signal, according to the expressions:
$$\begin{array}{l}I\left(t\right)=I_{\mathrm{one}}\left(t\right)-0.5\left(\mathrm{one}-A_{\mathrm{one}}\right)I_2\left(t\right)-0.5\left(\mathrm{one}-A_2\right){I^{\prime }}_3\left(t\right),\\ Q\left(t\right)=Q_{\mathrm{one}}\left(t\right)-0.5\left(\mathrm{one}-A_{\mathrm{one}}\right)Q_2\left(t\right)-0.5\left(\mathrm{one}-A_2\right){Q^{\prime }}_3\left(t\right).\end{array}$$