RU2358384C2 - Digital synthesiser of frequency and phase modulated signals - Google Patents

Abstract

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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Description

The invention relates to electronic computer technology, is intended for the synthesis of frequency-modulated and phase-modulated 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 phase.

Known digital frequency synthesizers of phase-modulated signals containing a constant storage unit, three memory registers, two digital storage devices, a divider with a variable division ratio, a reference generator, a delay unit, a code converter, a digital-to-analog converter, a low-pass filter, a waiting multivibrator and two adders [1] .

The closest technical solution (prototype) to the proposed one is a digital frequency synthesizer, containing a series-connected reference generator and a delay unit, series-connected the first permanent storage unit, the first digital storage device, the second memory register, the second digital storage device, code converter, digital-to-analog converter, lower filter frequencies; a second permanent storage unit and a counter with a preset; the inputs of the digital synthesizer are the inputs of the first and second blocks of the ROM, and the output is the output of the low-pass filter [2]. However, in known digital synthesizers, it is not possible to set the initial phase of the synthesized signal.

The invention allows to expand the functionality of digital synthesizers and makes it possible to synthesize frequency-modulated and phase-modulated signals.

A positive effect - providing the ability to control the initial phase of the synthesized signal - is achieved due to the fact that the digital synthesizer of frequency-modulated and phase-modulated signals, containing a series-connected reference generator and a delay unit; connected in series with a first memory register, a first digital storage device, a second memory register, a second digital storage device; a series-connected code converter, a digital-to-analog converter, a low-pass filter, the output of which is the output of the entire device, and the inputs of the first and third memory registers are the inputs of the digital synthesizer of frequency-modulated and phase-modulated signals; a series-connected third memory register, a frequency divider with a variable division ratio and a first digital storage device; the outputs of the delay unit are connected to the clock input of the divider with a variable division coefficient, the clock input of the digital-to-analog converter, the clock inputs of the first and second digital drives, the new one being that the fourth memory register, the third digital drive and the adder are connected in series, the second adder input is connected to the output of the second digital drive, and the output of the adder is connected to the input of the code converter, and the output of the senior output bit of the sum of the adder is connected to ode control inversion code converter; the output of the delay unit is connected to the clock input of the third digital drive; and the third input of a digital synthesizer of frequency-modulated and phase-modulated signals is the input of the fourth memory register.

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

A digital synthesizer of frequency-modulated and phase-modulated signals (Fig. 1) contains a reference generator 1, a delay unit 2, a first memory register 3, a first digital memory 4, a second memory register 5, a second digital memory 6, adder 7, code converter 8, digital-to-analog a converter 9, a low-pass filter 10, a third memory register 11, a frequency divider with a variable division ratio 12, a fourth memory register 13, a third digital storage 14.

A digital synthesizer of frequency-modulated and phase-modulated signals operates as follows. At the input of the first register of memory 3, the initial frequency code C _{i is} received, and at the input of the third register of memory 11, a code D _k determining the division coefficient of the divider 12 and the rate of change of the frequency of the digital computer synthesizer.

The reference generator 1 generates a reference frequency signal of a sinusoidal shape, which is fed to the input of the delay unit 2, forming a time-spaced sequence of rectangular pulses of the form "meander", which are fed to the clock inputs of the divider with a variable division factor 12, the first and second digital drives 4 and 6 , as well as the clock input of the digital-to-analog converter 9 and are used to synchronize the operation of the digital synthesizer.

With the first clock pulse at time t ₁ (Fig. 2), the initial frequency code C _i from the first memory register 3 is recorded in the first digital storage device 4, the division coefficient code D _k from the third memory register 11 is recorded in the divider with a variable division coefficient 12, and the initial phase code H _i from the fourth memory register 13 is recorded in the third digital drive 14.

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

Code A is fed to the input of the second digital drive 6, the summation of which will change according to the formula:

Code B enters the second input of the adder 7, and its first input receives the code N _i from the output of the third digital drive 14.

The S code at the output of the adder 7 is changed by the formula:

The result of the summation from the output of the adder 7 is fed to the input of the code converter 8, and the most significant bit of the code of the sum S _SGN is significant and is fed to the inversion control input of the code converter 8. The remaining N high-order bits (where N is the DAC bit capacity) are transmitted to the digital-to-analog information through the code converter converter (DAC) 9. If S _SGN = 0, then the binary direct sum code is sent to the DAC, if S _SGN = 1, then the reverse sum code is sent to the DAC 9.

At the output of the DAC 9, a “triangular” -shaped signal is generated, which is fed to the low-pass filter 10. The low-pass filter 10 has a cutoff frequency f _cp <f _m / 2, where f _m is the clock frequency, and only the first harmonic of the generated signal is passed to the output of the synthesizer .

If we assume that φ _i = H _i is the initial phase, f ₀ = С _i +1 is the initial frequency; 0.5f '= 1 / D _k is the rate of change of the frequency of the synthesized signal, Δt = T is the repetition period of the clock pulses, then a signal is formed at the output of the low-pass filter 10, the amplitude of which changes by the formula

where f ₀ is the initial frequency of the synthesized signal, f 'is the rate of change of the frequency of the synthesized signal, φ _i is the initial phase of the signal. Thus, in the digital synthesizer, it became possible to control the phase and frequency of the synthesized signal.

Information sources

1. Patent of the Russian Federation No. 2204196, IPC H03L 7/18, Digital synthesizer of phase-modulated signals / Ryabov I.V., Ryabov V.I. - Declared. 03/13/2001. Publ. 05/10/2003. Bull. No. 13.

2. Patent of the Russian Federation No. 2058659, MKI Н03В 19/00, Digital frequency synthesizer / Ryabov IV, Fischenko P.A. - Declared. 09/23/1993. Publ. 04/20/1996. Bull. No. 11. (Prototype).

Claims (1)

A digital synthesizer of frequency-modulated and phase-modulated signals, containing a series-connected reference generator and a delay unit; connected in series with a first memory register, a first digital storage device, a second memory register, a second digital storage device; a series-connected code converter, a digital-to-analog converter, a low-pass filter, the output of which is the output of the entire device, and the inputs of the first and third memory registers are the inputs of the digital synthesizer of frequency-modulated and phase-modulated signals; a series-connected third memory register, a frequency divider with a variable division ratio and a first digital storage device; the corresponding outputs of the delay unit are connected to the clock input of the divider with a variable division coefficient, to the clock input of the digital-to-analog converter, clock inputs of the first and second digital drives, characterized in that the fourth memory register, the third digital drive and adder are connected in series, the second adder input is connected to the output of the second digital drive, and the output of the adder is connected to the input of the code converter, and the output of the senior output bit of the sum of the adder One to the control input of the inverse code converter; the output of the delay unit is connected to the clock input of the third digital drive; and the third input of a digital synthesizer of frequency-modulated and phase-modulated signals is the input of the fourth memory register.

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