SU978314A1 - Signal synthesizer - Google Patents

Description

(5) DIGITAL FREQUENCY SYNTHESIZER

one

The invention relates to radio engineering and can be used in the construction of measuring generators with a low level of side oscillations, as well as in radio transmitting devices as a driver or frequency manipulator.

A known frequency synthesizer comprising a series-connected reference frequency generator, a D-trigger, a linearly varying voltage generator, a comparator, a trigger and a low-pass filter, as well as a series-connected frequency code setting unit, an accumulator, a memory register and a multiplication-division unit as well as the first digital-to-analog converter, the one-bit inputs of which are connected to the corresponding one-bit outputs of the frequency code setting block, and the second digital-to-analog converter, the output of which is pogo connected to another input of the comparator, while

The output of the reference frequency generator is connected to the signal input of the accumulating adder, the auxiliary output of which is connected to another input of the D-flip-flop and to the control input of memory register 1.

A disadvantage of the known device is the complexity of the device, since the multiplication-division block is an arithmetic unit.

to a device that performs the operations of dividing the overflow code by the number corresponding to the code of the set frequency and multiplying the quotient obtained by the corresponding factor.

15 In terms of equipment, the multiplication-division block is the most complex in the synthesizer.

The purpose of the invention is to simplify the synthesizer.

20

Claims (2)

The goal is achieved by the fact that in a digital synthesizer istot containing a series-connected reference frequency generator. iD-trigger, linearly varying voltage generator, comparator, trigger and low-pass filter, as well as a series-connected frequency code setting unit, accumulating an adder and memory register, as well as the first digital-to-analog converter, whose bit inputs are connected with the corresponding one-bit outputs of the frequency code setting block, and a second digital-to-analog converter, the output of which is connected to the other input of the comparator, while the output of the support generator (Noah's frequency is connected to the signal input on dripping adder, the auxiliary output of which is connected to another input of the D-flip-flop and to the control input of the memory register, the bit outputs of the memory register are connected to the corresponding bit inputs of the second digital-analog converter, and the output of the first digital-analog converter is connected to another linear voltage generator oscillator input. The figure shows a structural electrical circuit of the proposed digital frequency synthesizer. The synthesizer contains a 1-reference frequency generator, a frequency code setting block 2, accumulating adder 3, a memory register k, a first digital-to-analog converter (DAC) 5, a second DAC 6, a D-flip-flop 7, a generator of linearly varying voltage ( CLAY), comparator 9, trigger 10 and filter 11 Bottom often The device works as follows. The code of the required output frequency from the outputs of block 2 of setting the frequency code goes to accumulating sum 3, having a capacity N, and to the inputs of the first DAC $, the voltage from its output goes to GLINE 8 as the supply voltage of the circuit. With the pulse frequency in the generator 1 in the accumulating adder 3. addition of the accumulated number with the number M corresponding to the code at the output of the block 2. Through To the periods of the pulses of the generator 1, an accumulating accumulator 3 overflows, a pulse appears at its overflow output, which is fed to the control input of the memory register k and to the 9th D input of the O-t-rigger 7-V register 4, a code of the number P remaining in accumulative adder 3 after its overflow is recorded. The second DAC 6 converts the code of this number into a voltage applied to the first input of the comparator 9. The second input of the comparator 9 receives sawtooth pulses from the output of GLIN 8, whose duration is equal to the follow-up period of the reference frequency pulses, and the position is determined by the pulses from output D- trigger 7 delayed by overflow pulses also for the period of the reference frequency. When the voltage levels at both inputs coincide, the comparator 5 generates pulses whose duration varies during operation. ora The trigger 10 operates in the counting mode necessary to obtain 11 symmetric pulses at the input of the filter. In order to eliminate the dependence of the comparison result on the values of the M number corresponding to the set output frequency, the voltage at the output of GLINE 8 with the change of M must vary in span, therefore, the output voltage of the first DAC 5 is used as the supply voltage of GLINE 8, the value of which is proportional to the number M. The proposed device also allows you to increase the maximum frequency of the signal at the comparator output. When using the proposed device as a sensor of a fine grid of frequencies or as a frequency manipulator, the value of the number M in the process of work varies slightly. In this case, the magnitude of the sawtooth voltage at the second input of the comparator 9 varies slightly, which leads to a decrease in the level of the spectral components of the output signal. DETAILED DESCRIPTION OF THE INVENTION A digital frequency synthesizer comprising a series-connected reference frequency generator, a D-trigger, a linearly varying voltage generator, a comparator, a trigger, and a low-pass filter, as well as a series-connected frequency code setting unit, accumulation