RU2246181C2 - Receiver for quadratic-modified signals with displacement for multichannel communications system with coded channel separation - Google Patents

Abstract

FIELD: data transfer technologies.

SUBSTANCE: device tracks carrying frequency and data signal delay, for that code sequences are used, contained in common and quadratic components of received signal.

EFFECT: higher reliability and effectiveness.

2 cl, 2 dwg

Description

The invention relates to the field of information transmission by means of electromagnetic waves and can be used in cellular and satellite radio communications, telemetry systems, in radio control systems and fiber-optic information transmission systems.

Known cellular communication systems with code-time division of channels, using for the synchronization of the channel the so-called preambles (part of the time interval in the channel used to transmit clock signals) [1]. However, these systems have the following disadvantages.

1. Low energy efficiency, since to ensure reliable synchronization, it is necessary to allocate up to 40% of the channel energy for transmitting clock signals.

2. Low temporal efficiency of using the channel, since up to 40% of the time interval allotted for the transmission of each transmission of information is used to transmit clock signals.

3. When using systems of this type, it is not always possible to meet environmental safety requirements, since significant energy costs, which are necessary to ensure reliable synchronization of the system, lead to a high spectral power density in the coverage area of the communication system and, as a result, to violation of the requirements for environmental safety.

Also known are code division multiple communication cellular communication systems that use pilot signal [2] and [3] to synchronize receivers.

Their distinctive feature is that the pilot signal, which is used to synchronize the receivers of the system, is transmitted simultaneously with the information. However, in these systems, the use of a pilot signal also requires additional energy costs, which, if necessary, ensure reliable synchronization of the system, can be up to 30% of the energy allocated for information transfer, which leads to a high spectral power density in the coverage area of the communication system and, as a result to violation of environmental safety requirements.

Closest to the proposed invention is a receiver of pseudo-random signals [3] (prototype), including a series-connected first frequency converter (IF), the first input of which is the input of the receiver, the first intermediate frequency filter (PLL), the second PLL, the first multiplier (P), phase detector (PD), phase error filter (PFD), first control element (UE), controlled generator (UG), the output of which is connected to the second input of the first IF, the second P connected in series, the first input of which is connected to the output the first phase converter, the third phase converter, the first adder (C), the second frequency converter, the second C, delay error filter (FDF), the second UE, a controlled clock (UTG), a reference signal generator (GOS), the first output of which is connected to the second the input of the first P connected in series to the third P, the first input of which is connected to the output of the first PLL, the fourth PLL, the output of which is connected to the second input of the first C, as well as a reference generator (OG), the first output of which is connected to the second input of the PD, and its second the output through the phase shifter (PV) is connected to the second input House second IF output FFO via an amplifier (DC) connected to the second input of the second C, CRP second output connected to the second input of the second P and its third output connected to the second input of the third P.

The aim of the present invention is to provide a quadrature modulated bias signal receiver (OQPSK), which would ensure high energy efficiency of the communication system with code division multiplexing due to the use of all the radiated power only for information transfer, and would also provide environmental safety requirements for the communication system by reducing the spectral power density of the emitted signals while ensuring high reliability of the system synchronization.

This goal is achieved by the fact that in the known receiver of pseudo-random signals, including a series-connected first IF, the first input of which is the input of the receiver, the first phase-converter, second phase-converter, the first П, ФД, ФФО, the first УЭ, УГ, the output of which is connected to the second input of the first IF, serially connected to the second P, the first input of which is connected to the output of the first PLL, the third PLL, the first C, the second IF, the second C, FOZ, the second UE, UTG, GOS, the first output of which is connected to the second input of the first P, the third are connected in series P, p the first input of which is connected to the output of the first PLL, the fourth PLL, the output of which is connected to the second input of the first C, as well as the exhaust gas, the first output of which is connected to the second input of the PD, and its second output through the PV is connected to the second input of the second IF, the output of the PFD through The DC is connected to the second input of the second C, the second GOS output is connected to the second input of the second P, and its third output is connected to the second input of the third P, the first, second, third and fourth phase-phase converters, the first, second and third multipliers, phase detector are excluded reference generator the first and second adders, the amplifier, and additionally introduced new elements and connections between the elements, namely: the first wide-band low-pass filter (VLF) connected in series, the input of which is connected to the output of the second frequency converter, the first analog-to-digital converter (ADC), the first quadrature correlator (KK), low-pass filter (LPF) and decoder (D), the output of which is the output of the receiver, the second output of the first KK is connected to the input of the FFD, the output of the UG is connected to the input of the PV, the first input of the second IF is connected to the input the receiver, the output of the first inverter through the second CFC and the second ADC connected in series is connected to the second input of the first KK, the first and second inputs of the second KK, the second output of the second KK through the first digital adder (DS) is connected to the input of the phase converter, the output of the first ADC is connected to the first and the second inputs of the third KK, the second output of the third KK is connected to the second input of the first KS, the first output of the GOS is connected to the fourth input of the second KK, the second output of the GOS is connected to the third input of the first KK and the fourth input of the third KK, the third output of GOS is connected to even the third input of the first KK and the third input of the second KK, and its fourth output is connected to the third input of the third KK, and KK includes serially connected first multiplier (P), the first input of which is the first input of KK, and the second input is the fourth input of KK, third broadband low-pass filter (low-pass filter), the second DS, the output of which is the first output of the QC, and also connected in series with the second P, the first input of which is the second input of the QC, and its second input is the third input of the QC, the fourth LPF, the third DS, the third alternating current resident, a second input coupled to an output of the second CA, and low-pass filter (LPF), the output of which is the second output of the QC SHFNCH fourth output connected to the second input of the second CA, and the output of the third SHFNCH connected to the second input of the third CS.

Distinctive features of the proposed device are additional elements introduced into the receiver circuit, namely: the first and second CFC, the first and second ADCs, the first, second and third QC, low-pass filter, D, CS and the corresponding connections between them, which helps to increase energy efficiency through the use of all radiated power to transmit information, as well as the fulfillment of environmental safety requirements during the operation of a communication system by reducing the spectral power density of radiated signals while ensuring high reliability of system synchronization, which meets the criterion of "novelty."

Since the totality of the introduced elements and their relationship to the filing date of the application in the patent and scientific literature are not found, the proposed technical solution corresponds to the inventive step.

The block diagram of the device is shown in FIG. 1 and 2. The numbers in FIG. 1 marked:

1 - phase shifter on π / 2 (PV);

2 - controlled generator (UG);

3, 17 - control element (UE);

4 - phase error filter (FFO);

5, 11 - frequency converter (IF);

6, 12 - broadband low-pass filter (SHFNCH);

7.13 - analog-to-digital converter (ADC);

8, 14, 20 - quadrature correlator (QC);

9 - low-pass filter (low-pass filter);

10 - decoder (D);

15 - digital adder (CA);

16 - delay error filter (FDF);

18 - controlled clock generator (UTG);

19 - reference signal generator (GOS).

In the figure, 2 numbers indicate:

1, 4, 7 - multiplier (P);

2, 5 - broadband low-pass filter (HFNCH);

3, 6 - digital adder (CA);

8 - low-pass filter (low-pass filter).

The work of the receiver. Let us consider the operating procedure of the receiver according to the block diagram shown in FIG. 1, and provided that the receiver is in a state of capturing a received signal. The capture was carried out by the initial synchronization device, which is not considered in the claimed device.

Suppose the receiver input at time t _k receives the signal type

where S _I (t _k ) is the in-phase component of the signal;

S _Q (t _k ) is the quadrature component of the signal.

In turn,

where A _m is the amplitude of the signal;

r _i is the i-th information symbol taking the value 1 or -1;

d ' _j , d _j - j-th elements of the code sequence, taking values 1 or -1;

ω _c is the circular frequency of the received signal;

φ is the initial phase of the carrier;

n _I (t _k ), n _Q (t _k ) - in-phase and quadrature components of normal white noise in terms of power spectral density N _0/2 ;

T is the duration of the element of code sequences.

At the same time, signals of the form are fed to the second input of the first inverter (11) directly and to the second input of the second inverter (5) through the PV (1) from the output of the UG (2)

S _0I (t _k ) = cos (ω ₀ t _k ),

S _0Q (t) = sin (ω ₀ t _k ),

where ω ₀ is the circular frequency of the controlled generator.

Then the signal at the first input of the first KK (8) and at the first and second inputs of the third KK (20) after filtering in the first LPF (6) and transformations in the first ADC (7) has the form

and the signal at the second input of the first KK (8) and at the first and second inputs of the second KK (14) after filtering in the second LPF (12) and transformations in the second ADC (13) has the form

where x _k = (ω _c -ω ₀ ) t _k + φ = Δωt _k + φ;

Δω is the frequency difference between the received and reference signals.

The third code input of the first QC (8) from the second GOS output (19) receives the reference code sequence of pseudorandom symbols d _j identical and coinciding in time (within the duration of the code sequence element T) with the code sequence d _j contained in the received signal S _I (t _k ).

The reference code sequence of pseudorandom symbols d ' _j , identical and coinciding in time (within the duration of the code element T) with the code sequence d' _j contained in the received signal, is received at the fourth input of the first KK (8) from the third output of the GOS (19) S _Q (t _k ), but shifted in time by 0.5 clock cycles relative to the sequence supplied to the third input.

After processing the received and reference signals in (8), at its first output, a signal appears corresponding to the transmitted binary information sequence r _i , which through the low-pass filter (9) goes to the decoder (10), in which error correction and correction takes place, and then information symbols arrive at the output of the receiver, and a signal proportional to the phase difference of the carrier frequency of the received signal ω _c and the frequency ω _{0 of the} ultrasonic signal (2) appears on the second output of the first KK (8). This signal through the FFO (4) enters the first UE (3), which, acting on the UG (2), adjusts its reference frequency ω ₀ to the carrier frequency of the received signal ω _c .

At the third input of the third KK (20) from the fourth output of the GOS (19), a reference code sequence of pseudorandom symbols is received that is identical and lags by 0.5 clock cycles (0.57) relative to the code sequence d' _j contained in the received signal S _Q (t _k ).

At the fourth input of the third KK (20), from the second output of the GOS (19), a reference code sequence of pseudorandom symbols is received that is identical and ahead in time of the code sequence d ' _j contained in the received signal S _Q (t _k ).

After processing the received and reference signals in (20), a signal proportional to the temporal offset of the received signal relative to the reference signals, which is fed to the second input of the first DS (15), appears on its second output.

The third code input of the second QC (14) from the third GOS output (19) receives the reference code sequence of pseudorandom symbols that is identical and lags by 0.5 clock cycles (0.5T) relative to the code sequence d _j contained in the received signal S _I (t _k )

The fourth code input (14) from the first output (19) receives the reference code sequence of pseudorandom characters that is identical and ahead by 0.5 clock cycles in time of the code sequence d _j contained in the received signal S _I (t _k ).

After processing the received and reference signals at the second output (14), a signal appears proportional to the value of the temporal offset of the received signal relative to the reference, which is fed to the first input of the first DS (15).

In (15), the resulting error signal is generated, which is proportional to the mismatch in the actual delay of the received signal S (t _k ) relative to the reference ones formed by the GOS (19).

The resulting error signal for the delay from the output (15) through the FOZ (16) is supplied to the RE (17), which, acting on the UTG (18), adjusts its clock frequency to the clock frequency of the code sequence contained in the received signal. In turn, the UTG (18) controls the operation of the GOS (19), ensuring the appearance of signals at its outputs with the required delay relative to the received one.

The work of the spacecraft (8, 14 and 20) we will consider according to the scheme presented in figure 2, in two modes: in the mode of receiving information and in the mode of tracking the delay.

Work QC in the mode of receiving information. When the QC operates in the information reception mode, a signal of the form (5) is supplied to the first input P (1), and to its second input, a reference code sequence, which is identical to the code sequence contained in the signal (5), and coincides with it in delay accuracy determined by the operation of the delay tracking circuit, but not exceeding the duration of the code sequence element.

A signal of the form (4) is supplied to the first input of the second KK multiplier (4), and a reference code sequence, which is identical to the code sequence contained in the signal (4), and coincides with the delay in accuracy with the accuracy determined by the operation of the circuit, at its second input tracking the delay, but not exceeding the duration of the code sequence element.

In (1) and (4), the convolution of input and reference signals is carried out. The result of the convolution from the output (1) through the LPF (2) is fed to the first input of the DS (3) and to the second input of the DS (6), the result of the convolution from the output P (4) through the LPF (5) is fed to the second input of the DS (3) and at the first input of the CA (6).

At the output of the LPF (2), the signal can be represented as

and at the output of the creep filter (5) - in the form

Then, at the output of the DS (3), which performs the addition function, a signal of the form

The first term in this expression with sufficiently accurate synchronization [cos (x _k ) ≈1] is an information symbol, and the subsequent terms are noise. This signal from the output of the CA (3) is fed to the first output of the QC and to the second input P (7).

At the output of the CA (6), which performs the function of subtraction, a signal of the form

which is fed to the first input P (7). The signal from the output (7) through the low-pass filter (8) is fed to the second output of the QC. The signal at the second output of the QC has the form

Where

The expression after the last equal sign in (10) determines the carrier synchronization error. With a small frequency detuning, the error value is proportional to the value (2x _k + ξ _k ), which is a phase error. In this mode, the QC works (8).

The operation of the QC circuit in the delay tracking mode.

When the QC operates in the delay tracking mode, a signal of the form (4) or (5) is supplied to the first input P (1) and to the first input P (4), and a reference code sequence that is identical to the code sequence is supplied to the second input (1) contained in the signal (4) or (5), and is ahead of it by a time interval equal to half the duration of the code sequence element contained in the signal (4) or (5), and the reference code sequence identical to reference code sequence received at the second input (1), but delayed pressed relative to it for a time interval equal to the duration of the code sequence element. Subsequently, the signals from the outputs P (1) and (4) are subjected to the same processing as in the case described above. However, taking into account the supplied input and reference signals at the second output of the QC, the signal will have the form

or

where S _1I (T / 2) is the signal at the output of the LPF (2) when a signal of type (5) is applied to its first input;

S _2I (T / 2) - signal at the output of the LPF (5) when a signal of type (5) is applied to its first input;

S _1Q (T / 2) - signal at the output of the LPF (2) when a signal of type (4) is supplied to its first input;

S _2Q (T / 2) - signal at the output of the LPF (5) when a signal of type (4) is applied to its first input.

These expressions characterize the error value for the delay of the received signal (5) or (4) relative to the reference ones in common-mode or quadrature channels, respectively.

It should be noted that when the QC works in the delay tracking mode:

- it performs the functions of a delay discriminator, which is invariant to the transmitted information, i.e. incoherent;

- the first QC output is not used.

Let us evaluate the performance of the claimed device by the value of the s / w ratio at the output of the information channel, as well as in the channels for tracking the phase of the carrier frequency and the delay of the received signal. Since the signals at the outputs of the above-mentioned channels are random and ergodic, the s / w ratio at the output of the information channel can be obtained by time averaging of expression (8).

The mathematical expectation of the signal level, its dispersion and the s / w ratio at the first output of the QC (8) (information channel) are of the form

M [S _I + S _Q ] = A _m cos (x);

D [S _I + S _Q ] = N _0/2 ;

s / w = 2P _c / N ₀ .

From the expressions it follows that in the information channel the potential value of the s / w ratio is achieved, corresponding to the coherent (optimal) signal reception.

Sources of information

1. New standards for broadband radio communication based on W-CDMA technology: M .: International Center for Scientific and Technical Information, 1999 (Fig. 4.25, p.89; Fig. 4.26, p.90).

2. In the same place (Fig. 3.11, p. 56).

3. Aces G.I. Statistical theory of the reception of complex signals: - M .: Soviet Radio, 1977 (Fig. 4.20, p.213) (prototype).

4. Application of integrated circuits: a practical guide. In 2 kn. Prince 2. Trans. from English / Ed. A. Williams. - M .: Mir, 1987 (Fig. 8.33, p. 51).

Claims (2)

1. The receiver of quadrature modulated signals with bias (OQPSK) of a multi-channel code division multiplex communication system, which includes the first frequency converter, the first input of which is the receiver input, a phase error filter connected in series, the first control element, a controlled generator, the output of which connected to the second input of the first Converter, as well as a series-connected phase shifter and a second frequency Converter, characterized in that it additionally introduced first connected broadband low-pass filter, the input of which is connected to the output of the second frequency converter, the first analog-to-digital converter, the first quadrature correlator, the low-pass filter and the decoder, the output of which is the output of the receiver, the second output of the first quadrature correlator is connected to the input of the phase error filter and the output of the controlled generator is connected to the input of the phase shifter, the first input of the second frequency converter is connected to the input of the receiver, the output of the first converter The frequency converter is connected through a second broadband low-pass filter and a second analog-to-digital converter in series with the second input of the first quadrature correlator, as well as with the first and second inputs of the second quadrature correlator, the second output of which is connected through the first digital adder to the delay filter input, the output of the first analog-to-digital converter is connected to the first and second inputs of the third quadrature correlator, the second output of the third quadrature correlator is is dined with the second input of the first digital adder, the first output of the reference signal generator is connected to the fourth input of the second quadrature generator, the second output of the reference signal generator is connected to the third input of the first quadrature correlator and the fourth input of the third quadrature correlator, the third output of the reference signal generator is connected to the fourth input of the first the quadrature correlator and the third input of the second quadrature correlator, and the fourth output of the reference signal generator is connected to the third input the house of the third quadrature correlator, while the first quadrature correlator generates a signal at the first output corresponding to the transmitted binary information sequence, and at the second output - a signal proportional to the phase difference of the carrier frequency of the received signal and the frequency of the controlled oscillator, the second and third quadrature correlators form at the second outputs signals proportional to the time offset of the in-phase and quadrature components of the signal relative to the reference ones, respectively, and the generator the pn signal generates at the first output a reference code sequence that is identical and half a cycle in time in time the code sequence d _j contained in the in-phase component of the received signal, at the second output, a reference code sequence that is identical and half a cycle in time in the code sequence d ' _j , contained in the quadrature component of the received signal, at the third output, a reference code sequence that is identical and lags by a half-cycle relative to the code sequence atelnosti d _j, contained in the in-phase component of the received signal and the fourth output - reference code sequence identical to and lagging in poltakta respect to the code sequence d _'j, contained in the quadrature component of the received signal, where the d _j and d' _j - _j-th elements of a code sequence taking values 1 or -1, and d ' _j = d _j (t _k -T / 2). 2. The device according to claim 1, characterized in that the quadrature correlator includes a first multiplier connected in series, the first input of which is the first input of the quadrature correlator, and the second input is the fourth input of the quadrature correlator, the third broadband low-pass filter, the second digital adder, the output of which is the first output of the quadrature correlator, as well as a second multiplier connected in series, the first input of which is the second input of the quadrature correlator, and its second input d - the third input of the quadrature correlator, the fourth broadband low-pass filter, the third digital adder acting as a subtracter, the third multiplier, the second input of which is connected to the output of the second digital adder, and the low-pass filter, the output of which is the second output of the quadrature correlator, the fourth broadband output a low-pass filter is connected to the second input of the second digital adder, and the output of the third broadband low-pass filter is connected to the second input of the third digit Vågå adder.

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