Device for restoration of bearing frequency of signals with amplitude-phase manipulation

FIELD: radio engineering, possible use during coherent demodulation of signals with combined amplitude-phase manipulation.

SUBSTANCE: prototype device includes second memorizing device and logarithm computation block, while outputs of first and second analog-digital converters are connected, respectively, to first and second inputs of second memorizing device, output of which is connected to input of logarithm computation block, output of which is connected to second input of multiplier.

EFFECT: increased resistance of interference due to removal of false clamp point by phase on discriminatory characteristic.

4 dwg

 

The invention relates to electrical engineering and can be used for coherent demodulation of the combined amplitude-phase shift keying (AFM).

Known demodulator shestnadtsetirichnoe quadrature amplitude manipulation, containing the first and second phase detectors, filter, generator, first and second limiters (see RF patent №2013018, IPC 5 H 04 L 27/22, publ. BI No. 9, 15.05.94 g) [1].

The disadvantage of this demodulator is its low immunity, associated with the presence of point a false capture phase of its discriminatory characteristic in the neighborhood of ϕ≈23° (see [1, 2]). The operation of the demodulator in a state of false capture phase, which in the known device cannot be detected and corrected, leads to a complete loss of information at the output of the demodulator.

It is also known a device for the recovery of the carrier frequency signals shestnadtsetirichnoe quadrature amplitude manipulation, containing the first and second phase detectors, the first and second low pass filters, Phaser and four adder (see RF patent №2019054, IPC 5 H 04 L 27/34, publ. in BI No. 16, 30.08.94,) [2].

A disadvantage of the known device consists in its low noise immunity associated with possible loss of information due to the presence of false capture by f the see when ϕ ≈23° (see [2, 3]). In General, the presence of false grabs phase is the principal feature of devices for recovery of the carrier frequency signal with the amplitude-phase shift keying, which is explained by multimodality, i.e. the presence of multiple maxima of the likelihood function in the evaluation phase of the recovered carrier such signals (see, for example, N. Parkhomenko, Botashev BM, Shelepin Y.S. Research schemes recovery of the carrier frequency signals quadrature amplitude manipulation // Problems of Radioelectronics. Ser. IDW. - M.: NIEIR. - 1991. - VIP, p.65-76) [3].

To eliminate the possibility of false captures empirically synthesize such schemes recovery of the carrier frequency, which do not have points of false grips phase discriminatory characteristic.

A common shortcoming of this approach is the following. Because such devices do not correspond to theoretically optimal, i.e. those whose structure is derived from theory of estimates of signal parameters, such devices have a high dispersion of the recovered carrier in the vicinity of the working point ϕ=0°. This leads to low noise immunity of such devices.

Thus, the known demodulator shestnadtsetirichnoe quadrature amplitude manipulation, containing two phase detector, phase shifter,six adders and the generator, voltage controlled (VCO) (see RF patent №2020767, IPC 5 H 04 L 27/22, publ. in BI No. 18, 30.09.94,) [4]. In the known device is the recovery of the carrier frequency signals shestnadtsetirichnoe quadrature amplitude manipulation.

A disadvantage of the known device is its low noise immunity associated with high variance of the control voltage at the output of the VCO when the ϕ=0°despite the fact that the known device has a discriminatory feature in phase, no false points of seizures.

The rational combination of high noise immunity when ϕ=0° and minimal loss of information due to the exclusion of false grips is the use of those devices that have undesirable points false grips, special measures to change the shape of discriminatory characteristics when ϕ≠0°. Elimination of false points of seizures in this case is guaranteed to compensate for the criterion of immunity slight increase in the variance of the control voltage when the ϕ≠0°.

Known technical solutions closest to the claimed device (prototype) is a device for the recovery of the carrier frequency signal with the amplitude-phase shift keying, containing the first and second phase detectors, the first and storageinterface, loop filter, a voltage controlled oscillator, a phase shifter, the first and second analog-to-digital converters, the first constant storage unit, a multiplier, myCitadel and a unit for computing the arctangent, and the first inputs of the first and second phase detectors are combined and input device, the outputs of the first and second phase detectors are connected to the inputs of, respectively, first and second integrators, the output of the loop filter is connected to the input of the generator, voltage-controlled, the output of which is connected with the second input of the second phase detector and the input of the phase shifter, the output of which is connected to a second input of the first phase detector, the outputs of the first and second integrators are connected to the inputs of, respectively, first and second analog-to-digital converters, the output of the first analog-to-digital Converter connected to the first input of the unit for computing the arctangent and the first input of the first constant storage unit, the output of the second analog-to-digital Converter connected to the second input of the unit for computing the arctangent and the second input of the first permanent mass storage device, the output and the first input of the multiplier are connected, respectively, with the input of the loop filter and the output of myCitadel, the first and the second input of which is connected according to the government, with the release of the unit for computing the arctangent and the output of the first persistent storage device (see RF patent № 234816, IPC(7) H 04 L 27/34, publ. in BI No. 23, 2004 [5] - prototype).

A disadvantage of the known device is its low immunity when recovering a carrier frequency signal with the combined amplitude-phase shift keying (AFM), due to the presence of false points capture phase of its discriminatory character.

It is known that in most cases when recovery of the carrier frequency AFM signal is obtaining estimates the initial phase ϕ0signal by the maximum likelihood method [6, s], [9, s-92].

From theory of assessments known that the estimation of the maximum likelihood ϕ0is this assessment that serves as the root of an equation of the form :

where- the partial derivative for parameter ϕ;

ln(x) - natural logarithm of x;

the likelihood function of the parameter ϕ

(see, for example [6, s-289, f.(6.2.10); 7, p.148-149, f.(8.10)-(8.11); 8, s-235, f.(8.1)-(8.2)]).

If the signal energy of the manipulated parameters of the likelihood function in equation (1) must be pre-averaged over all values of UN-assessed parameters (in the case of the AE signal with amplitude shift keying - for all possible values of normative amplitudeeach of the signal points of the AFM signal) [9, pp.92-93, f.(4.29)].

Thus, when solving the likelihood equations need to look for this value in the initial phase ϕ0that gives the global maximum of the function

Due to the impossibility of fairly simple analytical representation offor an arbitrary signal AFM synthesis scheme carrier recovery based on the direct use of the expressions (1) and (2) is not possible.

However, it is obvious that the device prototype not produced significant operations on the signal provided by the expressions (1) and (2): there is no averaging of estimates the initial phase ϕ for all possible values of normative amplitude of the input signal and there is no subsequent taking the logarithm.

Under the regulatory amplitude of the AFM signal is the reference value of the amplitudethat is one of the two manipulated parameters: amplitude and phasecorresponding to each signal point SnAFM signal.

The device prototype such operations are not implemented, and to control GUN signal is of the form

where acfthe average amplitude of the AFM signal.

When this is included in the expression (3) cofactor Andcfis not the sum of the values of:

Thus, in the device prototype uses a simplified algorithm for obtaining the discriminatory characteristics of U(ϕ0)that in the vicinity of points ϕ0≠0° leads to making decisions that are different from the maximum likelihood and, consequently, to the appearance of false points of the hooks on discriminatory characteristic.

The technical result is to increase the noise immunity by eliminating points of false grips phase discriminatory characteristic.

Technical result is achieved by performing the following operations on the signal:

- input AFM signal is subjected to quadrature correlation processing using the reference oscillation output of the VCO and receive quadrature signals;

- quadrature signals obtained by the correlation processing, is subjected to analog-to-digital conversion and get the digital in-phase and quadrature samples;

- obtained digital in-phase and quadrature samples to calculate the first evaluation phase as the arctangent relations and quadrature-phase samples;

- using digital in-phase and quadrature counts as address code of the first permanent memory (ROM), at its output to get the second evaluation phase;

- using digital in-phase and quadrature counts as address code of the second constant storage unit, at its output receive regulatory amplitude AFM signal;

- serves the normative value of the amplitude of the AFM signal to the computing unit of the logarithm and get its output logarithm regulatory amplitude (ON) AFM signal;

- subtract from the first evaluation phase of the second evaluation phase, and the result of the subtraction is multiplied by the logarithm of the regulatory amplitude AFM signal;

signal obtained by multiplying the logarithm of the regulatory AFM amplitude of the signal is filtered in a loop filter and serves as a control voltage to the input of the VCO;

- at the output of the VCO receives the recovered carrier frequency of the input AFM signal.

The technical result is achieved in that the device for recovering a carrier frequency signal with the amplitude-phase shift keying contains the first and second phase detectors, the first and second integrators, a loop filter, a voltage controlled oscillator, a phase shifter, the first and second analog-to-digital converters, the first constant storage unit, a multiplier, myCitadel and block you is ilenia of arctangent, and the first inputs of the first and second phase detectors are combined and input device, the outputs of the first and second phase detectors are connected to the inputs of, respectively, first and second integrators, the output of the loop filter is connected to the input of the generator, voltage-controlled, the output of which is connected with the second input of the second phase detector and the input of the phase shifter, the output of which is connected to a second input of the first phase detector, the outputs of the first and second integrators are connected to the inputs of, respectively, first and second analog-to-digital converters, the output of the first analog-to-digital Converter connected to the first input of the unit for computing the arctangent and the first input the first permanent mass storage device, the output of the second analog-to-digital Converter connected to the second input of the unit for computing the arctangent and the second input of the first permanent mass storage device, the output and the first input of the multiplier are connected, respectively, with the input of the loop filter and the output of myCitadel, the first and the second input of which is connected, respectively, with the output of the unit for computing the arctangent and the output of the first constant storage device.

According to the invention it introduced the second persistent storage device and a computing unit of the logarithm, p is ICEM outputs of the first and second analog-to-digital converters connected, accordingly, with the first and second inputs of the second constant storage unit, the output of which is connected to the input of the unit for computing the logarithm, the output of which is connected with the second input of the multiplier.

This allows you to perform new operations on the signal using analog-to-digital conversion quadrature signals to obtain information about the logarithm regulatory AFM amplitude of the input signal and to consider it when doing basic operations on signals. In the inventive device, the logarithm of the regulatory AFM amplitude of the input signal is calculated by the code address of the second ROM and the form factor is involved in the calculation of the control voltage for the VCO. As will be shown later on, this account of the logarithm of the standard (reference) AFM amplitude of the signal leads to the formation of discriminatory characteristics, devoid of false points of seizures in phase, and finally to improve the noise immunity of the device.

Figure 1 shows a functional diagram of the inventive device.

Figure 2 shows a plot of the signal plane AFM signal. Thus in figure 2 the pointcomplies with regulatory position AFM signal on the signal plane, a Sn- the position due to a non-zero phase error in the carrier frequency.

Figure 3 shows discrimination shall include a description of the claimed device, figure 4 - discriminatory characteristics of the prototype in example 16-way AFM signal.

Device for recovering a carrier frequency signal with the amplitude-phase shift keying (see figure 1) contains the input 1 of the device, the first and second phase detectors (PD) 2 and 3, the phase shifter 4, the VCO 5, the first and second integrators 6 and 7, the loop filter 8, the first and second analog-to-digital converters (ADC) 9 and 10, the first persistent storage device (ROM) 11, a second ROM 12, block 13 to calculate the logarithm, block 14 calculation of arctangent, myCitadel 15 and the multiplier 16.

The first inputs of the first and second phase detectors 2 and 3 are combined and input 1 of the device, the outputs of the first and second phase detectors 2 and 3 are connected to the inputs of, respectively, first and second integrators 6 and 7, the output of the loop filter 8 is connected to the input of the generator 5, voltage-controlled, the output of which is connected with the second input of the second phase detector 3 and the input of the phase shifter 4, the output of which is connected to a second input of the first phase detector 2.

The outputs of the first and second integrators 6 and 7 are connected to the inputs of, respectively, first and second analog-to-digital converters 9 and 10, the output of the first analog-to-digital Converter 9 is connected to the first input unit 14 calculation of the arctangent and the first input of the first pic is wannago storage device 11.

The output of the second analog-to-digital Converter 10 is connected with the second input unit 14 calculation of the arctangent and the second input of the first constant storage unit 11, the output and the first input of the multiplier 16 is connected, respectively, with the input of the loop filter 8 and the output vicites 15, the first and the second input of which is connected, respectively, with the output of block 14 calculation of the arctangent and the output of the first constant storage unit 11.

The outputs of the first and second analog-to-digital converters 9 and 10 are connected, respectively, with first and second inputs of the second persistent storage device 12, the output of which is connected to the input unit 13 to calculate the logarithm, the output of which is connected with the second input of the multiplier 16.

The device operates as follows.

Input AFM signal is

whereand ϕnaccordingly, manipulated the amplitude and phase corresponding to the information symbol Infrom the sequence {In},

n(t) is additive white Gaussian noise (abgs).

Since the proposed device, as will be shown, automatically takes into account the amplitudesignal AFM in its operation, then the operation of the device to the M - position the ion signal AFM - you can spend on the example of one certain signal point (see figure 2).

Now, let the input device receives the signal AFM, corresponding to the model (4).

For simplicity, assume that the input abgs missing, i.e. n(t)=0 in the formula (4), but the carrier signal generated at the output of the VCO 5, has a phase mismatch ϕaboutwith respect to the input AFM signal (4). Thus, the signal at the output of the generator 5 can be represented in the form

After quadrature correlation processing input AFM signal using the reference oscillation (5) in blocks 2-7 and analog-to-digital conversion on the output of the first ADC 9 and the second ADC 10 are formed in-phase and quadrature digital samples Xnand Ynthat makes sense in-phase and quadrature coordinates taken AFM signal on the signal plane (see figure 2), shown in the plane of the point Sn.

Unit 14 the calculation of the arctangent generates at its output the signal

where Y is the signal at its first input;

X - signal at its second input.

Thus, the output of block 14 is formed in the first evaluation phase ϕ1corresponding to the true angular coordinate location of the point Sn.

In turn, supplied to the input of the first ROM 11 digital about the scores X nand Ynsense code addresses are address information stored in the first ROM 11. In the first ROM 11 in accordance with the view taken M - way AFM signal contains information about the normative value of the angular coordinatefor each current signal point Sn. The normative value of the phaseis one of the two values of the manipulated parameters describing each signal point Sn(see figure 2).

The first ROM 11 is programmed so that its output is generated ϕ2for any value of Xnand Ynsatisfying the condition

When this

whereandaccordingly, the in-phase and quadrature coordinates of the Central point of the signal region dened by expression (7).

In accordance with the logic of the first ROM 11 generated at the output of the first ROM 11 second assessment phase ϕ2is a normative value, i.e. the value that the device for recovering a carrier attributes as normative angular coordinate for all signal points Snentering the zone (7). This automatically taken into account, the projections of the current signal point on the ordinate axis, i.e. the real (non-normalized) amplitude of the input signal.

In accordance with the logic vicites 15 at its output, a signal is generated

At the input of the second ROM 12 digital samples Xnand Ynare address information stored in the second ROM 12. In the second ROM 12 in accordance with the view taken M-way AFM signal contains information about the standard (reference) value of the amplitudefor each current signal point Sn.

The second ROM is programmed so that its output is generatedfor any value of Xnand Ynsatisfying the condition (7).

Thus, the first ROM 11 and the second ROM 12 for any signal point Sngive at its output values of the normative phaseand amplitude, i.e. the reference values corresponding to the point.

The output unit 13 to calculate the logarithm, a signal is generated ON

Taking into account expressions (9) at the output of multiplier 16 is formed by the signal U16at the input of loop filter 8

Fixed ϕ0the expectation of the expression (11) accounted for the utter

From the expression (12) it follows that the averaged signal Uφin the loop filter 8 gives the tension, the expectation of which U(ϕ0) in proportion to the angle of misalignment ϕ0that allows you to control the VCO 5 to achieve ϕ0→0° and, therefore, coherently to recover the carrier frequency.

Here, as before, the symbol U(ϕ0denotes the signal at the input of the VCO 5, i.e. discriminatory characteristics of the device for recovering a carrier.

On discriminatory characteristic U(ϕ0for the signal QAM-16, is shown in figure 3, it is seen that in the inventive device are missing the point of false grips phase discriminatory characteristic.

The device is a prototype, as it is seen by its discriminatory characteristic shown in figure 4, in the range ϕ={-45°; +45°} has six points of false grips around values ϕ: -33; -26; -19; +19; +26 and +33°.

In the device prototype linear area of the true capture occupies an area of {-17°; +17°}that 1.6 is less than the total areas of false seizures in the range of angles ϕ -45 to +45°.

It defines the low immunity of the device prototype.

The absence of discriminatory characteristics of the proposed device the point of false seizures in phase with the same amount of linear plot discriminatory characteristics {-17° ; +17°} the proposed device provides higher noise immunity in comparison with the prototype.

Sources of information

1. RF patent 2013018, IPC 5 H 04 L 27/22, publ. in BI No. 9, 1994

2. RF patent 2019054, IPC 5 H 04 L 27/34, publ. in BI No. 16, 1994

3. Parkhomenko NG, Botashev BM, Shelepin Y.S. Research schemes recovery of the carrier frequency signals quadrature amplitude manipulation // Problems of Radioelectronics. Ser. IDW. - M.: NIEIR, 1991, VIP, p.65-76.

4. RF patent 2020767, IPC 5 H 04 L 27/22, publ. in BI No. 18, 1994

5. RF patent 2234816, IPC 7 H 04 L 27/34, publ. in BI No. 23, 2004 - prototype.

6. Had Soured J. Digital communication. - M.: Radio and communication. - 2000.

7. Kotousov A.S. Theoretical bases of radio systems. - M.: Radio and communication. - 2002.

8. Stiffler J. J. Theory of synchronous communications. - M.: Communication. - 1975.

9. Radio system. Ed. Umetalieva. - M.: Higher. school. - 1990.

Device for recovering a carrier frequency signal with the amplitude-phase shift keying, containing the first and second phase detectors, the first and second integrators, a loop filter, a voltage controlled oscillator, a phase shifter, the first and second analog-to-digital converters, the first constant storage unit, a multiplier, myCitadel and a unit for computing the arctangent, and the first inputs of the first and second phase detectors combined and t is Auda input device, the outputs of the first and second phase detectors are connected to the inputs of respectively the first and second integrators, the output of the loop filter is connected to the input of the generator, voltage-controlled, the output of which is connected with the second input of the second phase detector and the input of the phase shifter, the output of which is connected to a second input of the first phase detector, the outputs of the first and second integrators connected with inputs respectively of the first and second analog-to-digital converters, the output of the first analog-to-digital Converter connected to the first input of the unit for computing the arctangent and the first input of the first constant storage unit, the output of the second analog-to-digital Converter connected to the second input of the unit for computing the arctangent and a second input of the first permanent mass storage device, the output and the first input of the multiplier are connected, respectively, with the input of the loop filter and the output of myCitadel, the first and the second input of which is connected respectively with the output of the unit for computing the arctangent and the output of the first constant storage device, characterized in that it introduced the second persistent storage device and a computing unit of the logarithm, and the outputs of the first and second analog-to-digital converters connected respectively with the first and the WTO is the second inputs of the second persistent storage device, the output of which is connected to the input of the unit for computing the logarithm, the output of which is connected with the second input of the multiplier.



 

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