Synthesizer of frequency-modulated signals

FIELD: radio engineering.

SUBSTANCE: synthesizer of frequency-modulated signals comprises a phase detector, a low pass filter, a controlled generator, a divider with an alternating division ratio (DADR), a reference generator, a divider with a fixed division ratio (DFDR), an information source, M (M>1) generators of sine and cosine components of manipulation frequencies, M scale amplifiers for sine outputs and M scale amplifiers for cosine outputs, the first and second switchboards, a controlled phase inverter, the first and second multipliers, a control unit, a summator, a quadrature signal shaper.

EFFECT: higher efficiency of digital information transfer, removal of limitation for transferred information.

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The proposed device is a radio and can be used in receiving and transmitting devices, designed to create a frequency-modulated radio signals.

For transmission and reception of signals used for frequency modulation, harmonic oscillations of the carrier frequency.

The modulation frequency of the oscillator is described, for example, in the sources of information[1], [3], [7], but has the disadvantage of low frequency stability or out-of-band components.

Most often to generate harmonic vibrations are applied synthesizers based on phase-locked loop (PLL), the basic requirements for which to generate a predetermined carrier frequency or frequency of the local oscillator with high stability of output fluctuations. This possibility is considered in the literature, for example[1], [2], [3], [8].

A typical block diagram of the synthesizer is given in [4] (figure 1.15). p.33.

However, all known technical solutions do not provide for the transmission of digital signals with a large number of identical symbols, such as the units.

For clarification, consider a special case. Let the transmitted FM signal with a deviation of the output frequency is 5 kHz and a transmission rate of 8 kbps (bit time 0.125 MSC), one bit of the phase shift relative to the carrier oscillation, were the φ ₁=2π·0,125×5 or φ₁=2π·of 0.625. When the transfer of N consecutive identical symbols φ_N=2π of 0.625×N. the output of the phase modulator phase should vary less in the division ratio of DPCD time, i.e. k times and make φ_N=27π·of 0.625×(N/k). In [1] it is shown (C)that the maximum value of deviation of the phase in the analog phase modulator ±2π/3, and in the same book (pp.272) the maximum value of deviation of the phase of the digital phase modulator ±π. Similar results are shown in many other sources.

Thus, for this example the same number of characters must not exceed for the considered case of N_MAX=k/1,25. If we consider the transfer of characters in various combinations, the limitation will be more severe. Therefore, the existing frequency modulators impose a constraint on the transmitted information, which is not valid.

The closest in technical essence to the present invention is FM synthesizer harmonic oscillations, is given in [5], Chapter 1, figure 1.8, adopted for the prototype.

Functional diagram of the device of the prototype is presented in figure 1, where indicated:

1 - source of information;

4 - phase detector (PD);

5 - lowpass filter (LPF);

6 - driven generator (UG);

7 - reference generator (DG);

8 is a frequency divider with a fixed ratio Deleni the (DFCD);

9 is a frequency divider with variable division factor (DPCD);

19 - integrator;

20 - phase modulator (FM).

The device prototype contains connected in series source 1, the integrator 19, 20 FM, FD 4, LPF 5 and YR 6 whose output is the output of the device and through DPCD 9 is connected with the second input of the PD 4. In addition, the output of the EXHAUST gas 7 through DPCD 8 is connected with the second input of FM 20.

The device operates as follows.

Reference generator 7 generates a reference frequency oscillation, the frequency of which is divided into a fixed number in DFCD 8. From the output of divider 8 high-frequency voltage is applied to the second input of the phase modulator 20, at the first input of which is applied the voltage of the low frequency from the information source 1 that has passed through the integrator 19. The output voltage of the phase modulator 20 is supplied to the first input of the phase detector 4, which produces a voltage proportional to the phase difference between the high-frequency voltages on the first and second inputs FD 4, and the first input of a high-frequency voltage output from the FM 20, and the second input of the high frequency voltage output from the controlled oscillator 6, passed through the divider with a variable division ratio of 9. The output voltage of the phase detector 4 is integrated in the low pass filter 5 and is in the od controlled oscillator 6 and changes the frequency so to the phase-frequency vibrations to a second input of the phase detector 4 is equal to the phase at the first input of the phase detector 4. For this reason, the output voltage UG 6 will have a phase equal to the phase of high-frequency oscillations at the first input of the PD 4, increased by a factor of division DPKG 9 k times. In other words, the frequency of harmonic oscillations at the output ANGLE 6 will be larger than the frequency of the oscillations at the first input of the phase detector 4 in k times, and the deviation of the phase-frequency vibrations will be more than the deviation of the phase at the first input of the phase detector 4 in k times.

However, the phase modulators have limited the maximum deviation phase, which limits the number of transmit consecutive characters in the value of N_MAXmore precisely, any combination of symbols in which the number of ones and zeros differs by N_MAXwill be distorted. Thus, the synthesizer prototype when the digital signal does not work effectively.

The objective of the proposed technical solutions - improving the efficiency of transmission of digital information, i.e. the removal of restrictions on the transmitted information.

To solve the problem in the synthesizer frequency - modulated signals containing serially connected phase detector (PD), low pass filter, a controllable oscillator and a frequency divider with a variable coefficient of the m division (DPCD), the output of which is connected with the second input of the PD, and the output of the controlled oscillator is the output of the synthesizer, connected in series reference oscillator and the frequency divider with a fixed division factor (DFCD), as well as a source of information, according to the invention, introduced M (M>1) generators sine and cosine components of the frequency manipulation, sine and cosine outputs them through the appropriate M-scale amplifiers for sine outputs and M large-scale amplifiers for cosine outputs connected to respective inputs of the first and second switches, the control inputs of which are connected to the first output control unit, the second output of which is connected to control input of the controlled phase inverter, the output of which is connected to the second input of the adder, the output of which is connected to the first input FD, out DFCD connected to the input of the shaper quadrature signal, the sine output of which is connected to the first input of the first multiplier and cosine output to the first input of the second multiplier, the output of which is connected to the input of the control phase inverter, the output of the first multiplier connected to the first input of the adder, in addition, the outputs of the first and second switches are connected with the second inputs respectively of the first and second multipliers, the output of the source of the information is connected to the input of the control unit.

Functional diagram of the device is shown in figure 2, where indicated:

1 - source of information;

2 - the block of management;

3 - shaper quadrature signal;

4 - phase detector (PD);

5 - lowpass filter (LPF);

6 - driven generator (UG);

7 - reference generator (DG);

8 is a frequency divider with a fixed division factor (DFCD);

9 is a frequency divider with variable division factor (DPCD);

10, 11, the first and second multipliers;

12 - controlled phase inverter;

13, 14, the first and second switches;

15₁, 15₂, ... 15_Mlarge - scale amplifiers harmonic oscillations of a sine channels generators FM;

16₁, 16₂, ... 16_Mlarge - scale amplifiers harmonic oscillations of the cosine channels generators FM;

17₁, 17₂, ... 17_Mgenerators sine and cosine components of the frequency manipulation;

18 - adder.

Currently widely used generators of harmonic signals, simultaneously generating the sine and cosine components. For example, in the description of [9] digital receiver Analog devices AD6620 provides a functional diagram, in which there are complex NCO (Numerically Controlled Oscillator - generator with digital control), which has two outputs: sine and cosine.

Form the l quadrature channel generator with two outputs sine and cosine) has several implementation options, for example, [10], s, RES; s, RIS; [11], p.72 RIS, RIS and other

The proposed device comprises a reference generator 7 connected through DPCD 8 driver quadrature signal 3, the sine output of which is connected to the first input of the first multiplier 10, cosine shaper's output quadrature signal 3 is connected to the first input of the second multiplier 11, while the second inputs of multipliers 10 and 11 are connected to the outputs of the first 13 and second 14 switches respectively. The output of the first multiplier 10 is connected to the first input of the adder 18, and the output of the second multiplier 11 through controlled phase inverter 12 is connected to the second input of the adder 18, the output of which is connected to the first input of the phase detector 4, the output of which through successive chain of the LPF 5, UG 6 and DPCD 9 connected to the second input of the PD 4, and the output of the controlled oscillator 6 is the output of the frequency synthesizer.

Information source 1 is connected to the input of the control unit 2, the first output of which is connected to the control inputs of the switches 13 and 14, and the second output control unit 2 is connected to the control input of the phase inverter 12. In addition, the sine and cosine outputs of the M generators sine and cosine components of the frequency manipulation 17 through the corresponding large-scale amplifiers 15₁, 15₂, ... 15_Mfor the sine output is impressive and large-scale amplifiers 16 ₁, 16₂, ... 16_Mfor cosine outputs connected to respective inputs of the first 13 and second 14 switches.

Before considering the operation of the device, consider the principle of forming multi-frequency telegraphy (MCT). Consider the simplest case of a 4-point frequency telegraphy, i.e. there are four information positions 0, 1, 2 and 3. Let 0 corresponds to the frequency deviation-2ΔF, may 1 corresponds to the deviation frequency ΔF, may 2 corresponds to the frequency deviation ΔF, may 3 corresponds to the deviation frequency 2ΔF.

Similarly, you can submit work for an arbitrary number of positions. Note again that the deviation of the output signal of the synthesizer will be more in time, ie-2kΔF, -kΔF, kΔF, 2kΔF.

You may want to pass the position 3, i.e., to set the deviation of 2ΔF. In accordance with the above, the inputs of the first multiplier 10 will act harmonic signals sin(2πf₀t) and sin(2π2ΔFt), and the inputs of the second multiplier 11 will act harmonic signals cos(2πf₀t) and cos(2π2ΔFt). The voltage u(t) at the output of the adder 18 can be written in the form

u(t)=sin(2π2ΔFt)sin(2πf₀t)±cos(2π2ΔFt)cos(2πf₀t)

or in accordance with the formula for the cosine of the sum of the two angles

u(t)=-cos(2π(f₀±2ΔF)t).

Thus, the frequency is changed at the first input of the phase detector 4, which will lead the change of the output frequency of the synthesizer on 2ΔF, and phase - 2ΔFt. In this approach, the phase increases linearly with time and essentially no limit to its growth in value. Therefore, there is no limitation on the transmitted information on the number of consecutive identical characters.

Consider the work of the proposed device as a whole.

The proposed device operates as follows. Generators sine and cosine components of the frequency manipulation 17₁, 17₂, ... 17_Mproduce harmonic oscillations at frequencies ∆ F₁, ∆ F₂, ... ∆ F_Mwith each generator produces sine and cosine components of harmonic oscillations with the appropriate frequency. Sinusoidal components from the generator 17₁, 17₂, ... 17_Mare connected to the inputs of a large-scale amplifiers harmonic oscillations 15₁, 15₂, ... 15_M(provide conversion of phase modulation in the frequency - multiplication by 1/F_i). Cosine components from the generator 17₁, 17₂, ... 17_Mare connected to the inputs of a large-scale amplifiers harmonic oscillations 16₁, 16₂, ... 16_M(provide conversion of phase modulation in the frequency - multiplication by 1/ ∆ F_ii takes values from 1 to M). The output voltage of the large-scale amplifiers sinusoidal Garm the technical oscillations 15 ₁, 15₂, ... 15_Mare fed to the inputs of the first switch 13, to the control input of which is instructed from the control unit 2, this command connects the output of the switch 13 and, hence, to the input of the first multiplier 10 one of the M sinusoidal harmonic components. Number (from 0 to M) of the harmonic component is determined by the control unit 2 of the digital information from source 1.

The output voltage of the large-scale amplifiers cosine harmonic oscillations 16₁, 16₂, ... 16_Mare fed to the inputs of the second switch 14, to the control input of which is instructed from the control unit 2, the command connects to the output of switch 14 and, hence, to the input of the second multiplier 11 through controlled phase inverter 12 one of M cosine harmonic components. Number (from 0 to M) of the harmonic component is determined by the control unit 2 of the digital information from source 1, phase switching in a controlled phase inverter 12 is done by the command of the control unit 2 depending on the sign of the deviation frequency. To another input of the first multiplier 10 is supplied sinusoidal voltage from the output of the imaging unit 3, and to another input of the second multiplier 11 - cosine voltage from another output of the shaper 3. The output voltages of the multipliers 10 and 11 su is marouda the adder 18, the output of which is fed to the first input of the phase detector 4. To the second input of the phase detector 4 is energized from the output of the controlled oscillator 6 UG through the divider with a variable division ratio of 9, the phase difference between the harmonic oscillations of the first and second inputs of the phase detector 4 is the error signal, which is output from the phase detector 4 is fed through a low pass filter 5 to the control input of the controlled oscillator 6 and rebuilds the generator 6 frequency so that its phase is divided in the divider with a variable division ratio of 9 becomes equal to the phase of the harmonic oscillations at the first input of the phase detector 4. Thus, the output frequency of the harmonic oscillations of the controlled oscillator 6 is shifted in frequency by the amount kΔF_iand phase changes on 2πΔF_it. With the change of sign in a controlled phase inverter 12, the output frequency of the harmonic oscillations of the controlled oscillator 6 is shifted in frequency by the value - kΔF_iand the phase is changed to-2πΔF_it. Note that the number of positions at M generators is 2M due to a change in sign.

The control unit can be performed, for example, according to the scheme shown in figure 3, where D1 is a shift register; D2 - counter; D3.2, D3.3 - controlled inverters; D4 - decoder.

The control unit operates in the following manner and on the ohms. The data in serial form is loaded into the shift register D1, count on D2 after the arrival of the three clock pulses generates an enable signal to the shift register, in which the latter gives the previously recorded information to the output in parallel form. Elements D3.2 and D3.3 used as controlled inverters. The decoder on the element D4 converts a binary combination in the position code representing a set of signals to control the polarity and switching of generators. Item D3.1 is used as an inverter. Counter D2 element D3 mode divide-by-three.

The control unit is implemented according to the scheme in figure 3, can be performed on the chips of the firm Texas Instruments: element D1 - SN74hc595; D2 - SN74alsl61; D3 - SN74als86; D4 - SN74als139.

Sources of information

1. The generation of oscillations and the formation of radio signals. Edited Vinculadas and DNA. - M.: Publishing house of MPEI. 2008. - 416 S.: ill.

2. Radio transmitting devices. Shahgeldyan CENTURIES, Kozyrev V.B. have been, Shoukin A.A. and others edited Vol. - 2nd ed., revised and enlarged extra - M.: Radio and communication, 1990. - 432 S.: ill.

3. Radio transmitting devices. Shahgeldyan CENTURIES, Kozyrev V.B. have been, Shoukin A.A. and others, Ed. by V.V. Shahgeldyan. - 3rd ed., revised and enlarged extra - M.: Radio and communication, 2003. - 560 S.: ill.

4. Manasevich Century. frequency Synthesizers (Theory and design): TRANS. from English. / R is D. Galina. M: Communications, 1979. - 384 S. Il.

5. Tikhomirov NM, Romanov S. Kaliev, Linisin A.V. Formation of FM signals in synthesizers with locked loop. - M.: Radio and communication, 2004. - 210 S.: ill.

6. System phase sync / Akimov V.N., Belyustina L.N., White NR. and others; Ed. by Val, LN. Belyustinoi - M.: Radio and communication, 1982 - 288 C., Il.

7. Gonorovski I.S. Radio circuits and signals. - M.: "Soviet radio". 1971. - 672 S.

8. Kapranov M.V. elements of theory of systems of phase synchronization. - M.: MPEI Publishing house, 2006. - 208 S.

9. ANALOG DEVICES 65 MSPS Digital Receive Signal Processor. AD6620.

10. Dixon P.K. Broadband system. TRANS. with ang. Ed. Vigorelle. - M.: Communication, 1979. - 304 S., Il.

11. theory of signal transmission in railway transport. Gorelov GV Fomin A.F., and other M.: Transport, 2001. - 415 S.

The synthesizer frequency-modulated signals containing serially connected phase detector (PD), low pass filter, a controllable oscillator and a frequency divider with variable division factor (DPCD), the output of which is connected with the second input of the PD, and the output of the controlled oscillator is the output of the synthesizer, connected in series reference oscillator and the frequency divider with a fixed division factor (DFCD), as well as a source of information, characterized in that the input M (M>1) generators sine and cosine sostavljajushcheju manipulation, the sine and cosine outputs them through the appropriate M-scale amplifiers for sine outputs and M large-scale amplifiers for cosine outputs connected to respective inputs of the first and second switches, the control inputs of which are connected to the first output control unit, the second output of which is connected to the control input of the control phase inverter, the output of which is connected to the second input of the adder, the output of which is connected to the first input FD, out DFCD connected to the input of the shaper quadrature signal, the sine output of which is connected to the first input of the first multiplier and cosine output to the first input of the second multiplier, the output of which is connected with the input of the control phase inverter, the output of the first multiplier connected to the first input of the adder, in addition, the outputs of the first and second switches are connected with the second inputs respectively of the first and second multipliers, the output of an information source connected to the input of the control unit.