RU2354065C1 - Frequency modulator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention may be used for generation of frequency-modulated signals in networks and communication systems. Frequency modulator comprises source of reference voltage, integrator with reset, comparison unit, time digitiser, memorising unit, counter, generator of Walsh functions, multiplier, generator of rectangular pulses, element NOT and switch.

EFFECT: increased efficiency of frequency band application.

4 dwg, 1 tbl

Description

The invention relates to radio engineering and can be used to generate frequency-modulated signals in communication networks and systems, in various radio engineering devices.

A known frequency modulator containing a quantizer, a storage device, a comparison device, an integrator, a negative voltage source, a counter and a generator of Walsh functions (see. Harmut H.F. Information transfer by orthogonal functions. - M.: Communication, 1975, p. 130, fig. .3.25).

However, the output signals generated by this device have a large effective spectrum width, which leads to low bandwidth efficiency.

Closest to the technical nature of the present invention is a frequency modulator containing a reference voltage source, an integrator with a reset, a comparison unit, a time sampler, a storage unit, a counter, a Walsh function generator, a square wave generator, a switch and a multiplier, the time sampler and a storage unit are connected in series, as well as in series, are connected a reference voltage source, an integrator with a reset, a comparison unit and a Walsh function generator, a bl Single comparisons connected to the input of the counter, the installation entry integrator with reset, the clock input of the generator of rectangular oscillations, yield n-th (where N = 2 ⁿ - number of elements of the Walsh functions formed Walsh function generator), a counter discharge is connected with setting entry time sampler and memory unit, the output of which is connected to another input of the comparison unit, the first input of the switch is connected to the output of the square wave generator, the second input of the switch is connected to the output of the reference voltage source, the first input of the multiplier is connected to the output of the Walsh function generator, the second input is connected to the output of the switch, the control input of which is connected to the output of the (n-1) th discharge of the counter, while the output of the multiplier is the output of the device (see USSR copyright certificate No. 1665530, class. H04L 27/10, bull. No. 27 dated 07.23.91).

However, the output signals generated by this frequency modulator have a relatively large effective spectrum width, which leads to low bandwidth efficiency.

The aim of the invention is to reduce the effective width of the spectrum of the output signals, which improves the efficiency of use of the frequency band.

This goal is achieved by the fact that in a known frequency modulator containing a reference voltage source, an integrator with a reset, a comparison unit, a time sampler, a storage unit, a counter, a Walsh function generator and a multiplier, the time sampler and storage unit are connected in series and also connected in series reference voltage source, reset integrator, comparison unit and Walsh function generator, output of the comparison unit is connected to the counter input and the installation input of the integrator with reset, the output of the nth (where N = 2 ⁿ is the number of elements of the Walsh function generated by the Walsh function generator) of the discharge of the counter is connected to the installation inputs of the temporary sampler and the storage unit, the output of which is connected to another input of the comparison unit, the first input of the multiplier is connected to the output Walsh function generator, and the output of the multiplier is the output of the frequency modulator, a rectangular pulse generator, an element NOT and a switch are introduced, and the clock input of the rectangular pulse generator is connected to the output of the block and comparison, the rectangular pulse generator output is connected to the input of NOT circuit and the first input switch, the second input of which is connected to the output of NOT circuit, and an output coupled to a second input of the multiplier.

Figure 1 presents the structural diagram of the frequency modulator, figure 2 is a timing diagram illustrating the process of generating the output signal in the proposed frequency modulator, figure 3 is a view of the Walsh functions at the output of the generator 7 Walsh functions and the type of signals at the output of the proposed frequency modulator , Fig.4 is a view of the signals at the output of the prototype.

The frequency modulator contains a reference voltage source 1, an integrator 2 with a reset, a comparison unit 3, a time sampler 4, a storage unit 5, a counter 6, a Walsh function generator 7, a multiplier 8, a square-wave generator 9, an element 10, a switch 11.

The frequency modulator operates as follows.

In the initial state, the Walsh function generator 7 is ready to form the Walsh function with the arrival of pulses at its clock input. The generator 9 before starting the modulator is set to its initial zero state by applying a pulse to the corresponding input.

At the time θ = 0, the sampler 4 (Fig.2, b) reads the value of the signal received at the input of the frequency modulator (Fig.2, a). The resulting voltage is stored in the storage unit 5 (figure 2, c). At the output of the integrator 2 (figure 2, g) a linearly increasing voltage is formed. The comparison unit 3 (Fig. 2, e) compares this voltage with the voltage at the output of the storage unit 5 and returns the integrator 2 to its original state when the voltages turn out to be the same. As a result, a sawtooth voltage is formed at the output of the integrator 2. The amplitude and duration of the teeth of this saw are proportional to the voltage at the output of the storage unit 5. From the output of the comparison unit 3, the pulses that return the integrator 2 to its original state are also fed to the input of the counter 6. At the nth output of the counter (figure 2, f) ( where N = 2 ⁿ is the number of elements of the Walsh function generated by the generator of 7 Walsh functions) a pulse appears if 2 ⁿ pulses are received from comparison unit 3. This pulse returns the storage unit to its original state and records using the sampler 4 the sample value of the signal. In this case, the distance between the reference points depends on the magnitude of the signal values at the instant of reading. After generating this pulse, the counter returns to its original state when all the bits of the counter are reset.

The pulses from the output of the comparison device 3 also go to the clock input of the generator 7 of the Walsh functions, at the output of which a certain Walsh function is formed (Fig. 2, g), which arrives at the first input of the multiplier 8.

The pulses from the output of the comparison unit 3 are also received at the clock input of the generator 9 of rectangular pulses.

As a generator 9 of rectangular pulses, a conventional trigger with a counting input controlled by pulse signals can be used. Such a trigger changes its state to the opposite when the next pulse arrives at its counting input. That is, when the first pulse arrives at the counting input of the trigger, it is set to "1" and a rectangular pulse begins to form at its output (see Fig. 2, h). When the second pulse arrives at the counting input of the trigger, it is set to "0", ie the formation of a rectangular pulse at the output of the trigger ends. When the third pulse arrives at the counting input of the trigger, a rectangular pulse begins to form at its output again, and so on. As a result, the duration of the rectangular pulses is equal to the duration of the elements of the Walsh function Δt.

The operation of the counter 6 and the generator 7 of the Walsh functions is synchronous because pulses from the output of the comparison unit 3 are received at the counting input of the counter 6 and the clock input of the generator 7 of the Walsh functions (see Fig. 2, e). The pulse at the output of the counter 6 appears when 2 ⁿ pulses from the output of the comparison unit 3 arrive at its input. Since each Walsh function consists of 2 ⁿ elements, then during the arrival time of these 2 ⁿ pulses from the output of the comparison unit 3, the completely corresponding Walsh function will be generated at the output of the Walsh function generator 7 and the generator will again be ready to form. Upon receipt of the following pulses at its clock input from the output of the comparison unit 3, the Walsh function is formed at the output of the generator 7.

The pulses from the output of the generator 9 rectangular pulses are fed to the input of the element NOT, the output of which forms a sequence of rectangular pulses, the duration of which is also equal to the duration of the elements of the Walsh function Δt (see figure 2, and).

The pulses from the output of the rectangular pulse generator 9 are supplied to the first input of the switch 11, and the pulses from the output of the element 10 are supplied to the second input of the switch 11. The switch 11 is controlled before the frequency modulator starts operation. This can be done manually by the human operator. It should be emphasized that during the entire communication session, the generator 7 of Walsh functions periodically generates only one Walsh function.

If the generator 7 of the Walsh functions generates a Walsh function with serial number 0, ..., 2 ^n-1 -1, then before starting the frequency modulator, the operator sets the switch 11 to the left position (i.e., commutes the output of the switch with its first input, in other words, connects the second input of the multiplier 8 with the output of the generator 9 of rectangular pulses).

2^n-1,…, 2ⁿ-1, то перед началом работы частотного модулятора оператор устанавливает переключатель 11 в правое положение (то есть осуществляет коммутацию выхода переключателя с его вторым входом, иначе говоря, соединяет второй вход перемножителя 8 с выходом элемента НЕ 10). На фиг.1 переключатель 11 установлен так, как описано во втором случае.If the generator 7 of the Walsh functions generates a Walsh function with a serial number

2 ^n-1 , ..., 2 ⁿ -1, then before starting the frequency modulator, the operator sets the switch 11 to the right position (that is, it switches the output of the switch with its second input, in other words, connects the second input of the multiplier 8 to the output of the element 10 ) In figure 1, the switch 11 is installed as described in the second case.

If at the output of the generator 7 Walsh functions, the Walsh function is generated with the serial number 0, ..., 2 ^n-1 -1 (for example, for N = 8 - a function with one of the serial numbers 0; 1; 2; 3), then before the beginning of the work of the frequency modulator, the output of the switch 11 is switched with its first input. As a result, the pulses from the output of the generator 9 of rectangular pulses (Fig.2, h) are fed to the second input of the multiplier 8, the output of which will be formed only the odd pulses of the Walsh function, arriving at the first input of the multiplier 8.

If at the output of the generator 7 Walsh functions, the Walsh function with serial number 2 ^n-1 , ..., 2 ⁿ -1 is formed (for example, for N = 8 -function with one of the serial numbers 4; 5; 6; 7), then before starting the work of the frequency modulator, the output of the switch 11 is switched with its second input. As a result, the pulses from the output of the element NOT 10 (Fig.2, and) are fed to the second input of the multiplier 8, the output of which will be formed only even pulses of the Walsh function, arriving at the first input of the multiplier 8.

As a result, over a period of time θ _j , where j is the sequence number of the orthogonality interval, a frequency-modulated output signal is generated at the output of the multiplier 8 (Fig. 2, j).

Figure 2 shows the timing diagrams illustrating the process of generating the output signal in the proposed frequency modulator. Figure 3 presents a view of the Walsh functions at the output of the generator 7 of the Walsh function with the duration of the elements Δt, figure 3 also shows the signals at the output of the proposed frequency modulator, figure 4 is a view of the signal at the output of the prototype at the same frequency of pulses from the output of the comparison device 3 to the input of the generator 7 Walsh functions in the proposed frequency modulator and prototype.

The system of output signals generated by the proposed frequency modulator (Fig. 3), as well as the system of output signals generated by the prototype (Fig. 4), is orthogonal, as can be easily seen by multiplying two signals included in one system and integrating the result of multiplication over signal duration time.

If all the spectra of the signals included in the system have the same width and occupy the same frequency band, then F _syst = F (where F _sist is the bandwidth occupied by the signal system, F is the spectrum width of a single signal). With different spectral widths F _syst = F _max - the maximum width of the spectrum (see Varakin L.E. Theory of signal systems. - M.: Soviet radio, 1978, p. 11).

The effective spectral width W _{μ eff of a} broadband signal is determined by the formula:

where Δt is the duration of the signal elements, μ is the number of signal blocks, N is the number of signal elements (see Varakin L.E. Theory of signal systems. - M .: Soviet radio, 1978, p. 208, ratio 11.11).

In this case, a block is a sequence of elements having a phase of 0 or π, that is, a sequence of positive or negative signal elements (see Varakin L.E. Theory of signal systems. - M.: Soviet radio, 1978, p.177, first line).

In the prototype (see USSR author's certificate No. 1665530, class H04L 27/10, bull. No. 27 of 07/23/91) output signals are generated having the number of blocks:

или

or

(см. фиг.4).and the value of the largest effective width of the spectrum of the output signal is determined from relation (1) taking into account

(see figure 4).

In the proposed frequency modulator, all output signals have the same number of blocks:

and the value of the largest effective spectrum width of the output signal

(фиг.3).is determined from relation (1) taking into account

(figure 3).

Values of the maximum effective width of the spectrum of output signals generated by an analog (see Harmut Kh.F. Information transfer by orthogonal functions. - M .: Svyaz, 1975, p.180, Fig. 3.25) formed by a prototype (see USSR author's certificate No. 1665530 , CL H04L 27/10, bull. No. 27 dated 07.23.91) and formed by the proposed frequency modulator are presented in the table.

Number of Signal Elements four 8 16 32 64 Output signals Maximum Effective Spectrum Width for Output Signals Formed by analog 10,583 21,909 44.54 89.8 180.31 Molded by prototype 8,944 16.94 32,985 64,992 128,996 Formed by the proposed frequency modulator 7,483 15,491 31,496 63,498 127,499

According to the results of the table, we can conclude that the effective width of the spectrum of the output signals generated by the proposed modulator is much smaller than that of the signals generated by the analogue and prototype. In particular, the width of the spectrum of the output signals generated by the proposed frequency modulator is less than that generated by the analogue by 29.29% for signals with any number of elements N, and less than by the prototype generated by 16.33% for N = 4 , by 8.71% - for N = 8, by 4.51% - for N = 16, etc.

Using the invention allows the creation of frequency modulators that reduce the width of the spectrum of the output signals, which increases the efficiency of using the frequency band.

Claims (1)

A frequency modulator comprising a reference voltage source, a reset integrator, a comparison unit, a time sampler, a storage unit, a counter, a Walsh function generator and a multiplier, the time sampler and a storage unit being connected in series as well as a reference voltage source, a reset integrator, connected in series, a comparison unit and a Walsh function generator, the output of the comparator is connected to the input of the counter and the installation of the integrator with reset input, output n-th, where N = 2 ⁿ - number of elements funct and Walsh, formed by the generator of Walsh functions, the discharge of the counter is connected to the installation inputs of a temporary sampler and a storage unit, the output of which is connected to another input of the comparison unit, the first input of the multiplier is connected to the output of the generator of Walsh functions, and the output of the multiplier is the output of the frequency modulator, characterized in that a rectangular pulse generator, an element NOT and a switch are led into it, and the clock input of the rectangular pulse generator is connected to the output of the comparison unit, the output of the gene Rathore rectangular pulses connected to the input of NOT circuit and the first input switch, the second input of which is connected to the output of NOT circuit, and an output connected to the second input of the multiplier.

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