Digital synthesiser of frequency and phase modulated signals

FIELD: physics; communication.

SUBSTANCE: present invention pertains to electronics and computer technology, meant for synthesising frequency and phase modulated signals and can be used in radar, navigation and adaptive communication systems. The digital synthesiser of frequency modulated and phase modulated signals contains a reference generator, delay unit, first memory register, first digital accumulator, second memory register, second digital accumulator, adder, code converter, digital-to-analogue converter, low pass filter, third memory register, frequency divider with varying division factor, fourth memory register and a third digital accumulator.

EFFECT: provision for independent control of synthesised signals on frequency and on phase.

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The invention relates to electronic computing, designed for the synthesis of frequency-modulated and fazokodirovannymi signals and can be used in radar, navigation, and adaptive communication systems.

The invention allows for independent modulation of the synthesized signal both in frequency and in phase.

Known digital frequency synthesizers fazokodirovannymi signals containing a block of continuous memory three memory registers, two digital drive, a divider with a variable division ratio, the reference generator, the delay block, the code Converter, d / a Converter, low pass filter, waiting multivibrator and two adder [1].

The closest technical solution (prototype) to the proposed digital frequency synthesizer containing serially connected reference generator and the delay unit, connected in series, the first block of continuous memory, the first digital memory, the second register memory, the second digital memory, the code Converter, digital to analog Converter, a low pass filter; the second block of continuous memory and preset counters; inputs digital synthesizer are the inputs of the first and second blocks of the ROM, and the output is the output of the lowpass filter []. However, in the known digital synthesizers there is no possibility to set the initial phase of the synthesized signal.

The invention allows to extend the functionality of digital synthesizers and provides an opportunity to synthesize the frequency-modulated and fazokodirovannymi signals.

Positive effect - the ability to control the initial phase of the synthesized signal is due to the fact that in the digital synthesizer is frequency-modulated and fazokodirovannymi signals connected in series reference generator and the delay unit; sequentially connected first memory register, the first digital memory, the second register memory, the second digital drive connected in series code Converter, digital to analog Converter, a low pass filter whose output is the output of the entire device, and inputs the digital synthesizer is frequency-modulated and fazokodirovannymi signals are the inputs of the first and third memory registers; connected in series, the third memory register, a frequency divider with variable division factor and the first digital storage medium; the outputs of the delay block is connected to the clock input of the divider with a variable division ratio, clock input digital to analogue Converter, a clock in which the od of the first and second digital drives moreover, it is new that entered serially connected fourth memory register, the third digital memory and the adder, the second input of the adder connected to the output of the second digital memory and the output of the adder connected to the input of the code Converter, the older the output of the discharge amount of the adder is connected to the control input of the inversion of the code Converter; the output of the delay block is connected to the clock input of the third digital memory; and a third input of the digital synthesizer is frequency-modulated and fazokodirovannymi signal is input to the fourth memory register.

Figure 1 shows the structural diagram of the digital synthesizer is frequency-modulated and fazokodirovannymi signals, figure 2 - graphs of the signals at the DAC output device.

Digital synthesizer is frequency-modulated and fazokodirovannymi signals (figure 1) contains a reference oscillator 1, the delay unit 2, the first memory register 3, the first digital memory 4, the second register memory 5, the second digital memory 6, an adder 7, the code Converter 8, a d / a Converter 9, a low-pass filter 10, the third memory register 11, a frequency divider with a variable division ratio of 12, the fourth memory register 13, the third digital memory 14.

Digital synthesizer is frequency-modulated and f is modelirovaniya signals is as follows. The input of the first memory register 3 receives the code start frequency_i, and the input of the third memory register 11 code D_kthat defines the division factor of the divider 12 and the rate of change of frequency of the digital computer synthesizer.

The reference generator 1 outputs a signal of the reference frequency sine wave which is fed to the input of the delay block 2 forming spaced in time sequence of rectangular pulses of the form "meander", which are received at the clock inputs of the divider with a variable division ratio of 12, the first and second digital drives 4 and 6, and the clock input d / a Converter 9 and serve to synchronize the operation of the digital synthesizer.

With the first clock pulse at time t₁(2) code start frequency_ifrom the first memory register 3 is written in the first digital memory 4, code division ratio of D_kfrom the third memory register 11 is recorded in the divider with a variable division ratio of 12, and code the initial phase H_ifrom the fourth memory register 13 is written in the third digital memory 14.

Then with each clock pulse code And the output of the first digital drive 4 will change as follows:

Code And is fed to the input of the second digital nakopitel is 6, the result of the sum which will vary according to the formula:

Code is supplied to the second input of the adder 7, and the first input signal code H_iwith an output of the third digital memory 14.

Code S at the output of the adder 7 is changed according to the formula:

The result of the summation output of the adder 7 is fed to the input of the code Converter 8, and the high-order code amount S_SGNis iconic and is supplied to the control input of the inversion of the code Converter 8. The rest of the N high-order bits (where N - bit DAC) through the code Converter receives information on digital to analogue Converter (DAC) 9. If S_SGN=0, the DAC goes straight binary code amount, if S_SGN=1, then d / a Converter 9 is fed back code amount.

DAC output 9 is formed a stepped signal "triangular" form, which is fed to low-pass filter 10. The lowpass filter 10 has a cut-off frequency f_cp<f_m/2, where f_m- clock frequency, and transmit the output of the synthesizer only the first harmonic of the generated signal.

If we assume that φ_i=H_i- the initial phase, f₀=C_i+1 - the initial frequency; 0.5f'=1/D_k- the rate of change of the frequency synthesized signal, Δt=T is the repetition period of the clock pulses, then the output Phil is tra bass 10, a signal is generated, the amplitude of which changes according to the formula:

where f₀- initial frequency of the synthesized signal, f' is the rate of change of the frequency synthesized signal φ_i- the initial phase of the signal. Thus, in a digital synthesizer has the opportunity to control the phase and frequency of the synthesized signal.

Sources of information

1. The patent of Russian Federation №2204196, IPC H03L 7/18, Digital synthesizer fazokodirovannymi signals / Ryabov I. Ryabov, VI - Appl. 13.03.2001. Publ. 10.05.2003. Bull. No. 13.

2. The patent of Russian Federation №2058659, MKI NV 19/00, the Digital frequency synthesizer / Ryabov I., fishchenko P.A. - Appl. 23.09.1993. Publ. 20.04.1996. Bull. No. 11. (Prototype).

Digital synthesizer is frequency-modulated and fazokodirovannymi signals connected in series reference generator and the delay unit; sequentially connected first memory register, the first digital memory, the second register memory, the second digital drive connected in series code Converter, digital to analog Converter, a low pass filter whose output is the output of the entire device, and inputs the digital synthesizer is frequency-modulated and fazokodirovannymi signals are the inputs of the first and third memory registers; connected in series, the third register is memory, the frequency divider with variable division factor and the first digital drive; the corresponding outputs of the delay block is connected to the clock input of the divider with a variable division ratio, to the clock input of a digital to analogue Converter, the clock inputs of the first and second digital drives, wherein the entered serially connected fourth memory register, the third digital memory and the adder, the second input of the adder connected to the output of the second digital memory and the output of the adder connected to the input of the code Converter, the older the output of the discharge amount of the adder is connected to the control input of the inversion of the code Converter; the output of the delay block is connected to the clock input of the third digital drive; and the third input of the digital synthesizer is frequency-modulated and fazokodirovannymi signal is input to the fourth memory register.