RU2405243C1 - Demodulator of am and ft signals - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention can be used in radio communication systems to arrange simultaneous reception to common receiver of amplitude-modulated AM voice information and information on FT data transmission via two different radio communication channels tuned to one and the same carrier frequency. Demodulator of AM and FT signals includes twelve signal multipliers, five low frequency filters, two amplifiers, three sinusoidal wave generators, three control elements, three phase changers, five adders, integrator and threshold device.

EFFECT: providing the possibility of simultaneous reception of voice information with AM amplitude modulation and FT data transmission via radio communication channel, which are tuned to one and the same carrier frequency and with fluctuating initial phases of received signals.

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Description

The invention relates to the field of radio communication and can be used in radio communication systems for organizing the simultaneous reception on a single receiver of amplitude-modulated (AM) telephone information and data transfer information (CT) via two different radio channels tuned to the same carrier frequency as from various radio stations, and from one radio station having an appropriate modulator.

Known circuits of signal demodulators with amplitude modulation (AM), frequency modulation (FM, CT), phase modulation (FM, FT), as well as with the simultaneous modulation of several signal parameters with the same information message [1].

However, the known schemes [1] do not allow simultaneous demodulation of several (two or more) signals that contain different messages.

Closest to the claimed invention is a demodulator AM and CT signals [2], which is selected as a prototype.

The main disadvantage of the prototype is that it does not allow demodulation of signals in channels with an unknown and randomly changing initial phase of the AM and BT signals, which include most radio channels.

The main task to be solved by the claimed invention is aimed at providing the possibility of simultaneous reception of telephone information with amplitude modulation (AM) and transmission of radio frequency data via radio channels tuned to the same carrier frequency, but with fluctuating initial phases of the received signals.

The specified technical result is achieved by the fact that in the demodulator AM and CT of signals, which contains eight signal multipliers, two low-pass filters (LPFs), two amplifiers with a gain coefficient K _у = 2, two sinusoidal oscillation generators, two phase shifters that shift the initial phases, the signals arriving at their input by 90 °, an integrator, a threshold device, and three adders, an additional third generator of sinusoidal oscillations, four signal multipliers, one phase shifter, which carries out the shift of the initial phase, are additionally introduced 90 ° dull signal at its input, two signal adders and three low-pass filters (LPFs), the input of the first LPF being connected to the output of the first signal multiplier, the first input of which is connected to the first inputs of the second, third, fourth, fifth and sixth signal multipliers and is the input of the device, and the second input is connected to the output of the first phase shifter, the input of which is connected to the output of the first generator of sinusoidal oscillations and to the first input of the seventh signal multiplier, the output of which is connected to the second input of the second a signal multiplier, the output of which is connected to the input of the second low-pass filter, the output of which is connected to the input of the first control element, the output of which is connected to the input of the first sinusoidal oscillator, the second input of the seventh signal multiplier is connected to the first input of the eighth signal multiplier and to the output of the first amplifier with a gain To _y = 2, the output of which is the output of the device on which there is an estimate of the amplitude of the AM signal, the input of the first amplifier is connected to the output of the first low-pass filter, the second input is eight o the signal multiplier is connected to the output of the first phase shifter and to the second input of the first signal multiplier, the output of the eighth signal multiplier is connected to the second inputs of the ninth and tenth signal multipliers, the second inputs of which are connected to the outputs of the eleventh and twelfth signal multipliers, the output of the ninth signal multiplier is connected to the second input the first signal adder, the first input of which is connected to the output of the fourth signal multiplier, and the output is connected to the input of the third low-pass filter, the output of which is connected to the first input of the second signal adder, the second input of which is connected to the output of the fourth low-pass filter, the input of which is connected to the output of the third signal adder, the second input of which is connected to the output of the tenth signal multiplier, and the first input to the output of the fifth signal multiplier, the second input of which is connected to the output of the twelfth a signal multiplier, the input of which is connected to the output of the second sinusoidal oscillator and the input of the second phase shifter, the input of the second sinusoidal oscillator is connected to the second o control element, the input of which is connected to the output of the second signal adder and to the input of the third control element, the output of which is connected to the input of the third sine wave generator, the output of which is connected to the input of the third phase shifter and to the first input of the eleventh signal multiplier, the output of which is connected to the second input the fourth signal multiplier, the output of the second and third signal phase shifters is connected to the first and second inputs of the fourth signal adder, the output of which is connected to the second input of the third multiplier signal, which output is connected to the input of the fifth low-pass filter, whose output is connected to an input of the second amplifier with a gain K _v = 2, the output of which is coupled to second inputs of the eleventh and twelfth multipliers signals, in addition, outputs of the second and third phase shifters are connected to the the first and second inputs of the fifth signal adder, the output of which is connected to the second input of the sixth signal multiplier, the output of which is connected to the input of the integrator, the output of which is connected to the input of the threshold device The property whose output is the output of the demodulator of the PM signal.

At the same time, the demodulator AM and CT signals structurally consists of five channels:

- channel estimation (demodulation) AM signal;

- channel assessment (measurement) of the initial random phase of the AM signal;

- channel estimation (measurement) of the amplitude of the signal of the channel;

- channel assessment (measurement) of the initial random phase of the signal of the channel;

- channel, demodulation of the BT signal.

The drawing shows a structural diagram of the inventive demodulator.

The channel (evaluation) of demodulation of the AM signal contains the first signal multiplier 1, the first input of which simultaneously receives the sum of AM and TH modulated signals from the intermediate frequency amplifier of the receiver, the first low-pass filter 2 (low-pass filter), the first amplifier 3 with a gain of K _y = 2 , the first phase shifter 4 and the first tunable generator of sinusoidal oscillations 9.

The channel for evaluating (measuring) the initial random phase of the AM signal contains a second signal multiplier 5, the first input of which simultaneously receives the sum of AM and CT modulated signals from the intermediate frequency amplifier of the receiver, the second low-pass filter 6, the first control element 7, the seventh signal multiplier 8 and the first adjustable sine wave generator 9.

The channel for estimating (measuring) the amplitude of the BT signal contains a third signal multiplier 10, the first input of which simultaneously receives the sum of AM and CT modulated signals from the intermediate frequency amplifier of the receiver, the fifth low-pass filter 11, the second amplifier 12 with a gain of K _y = 2 and the fourth signal adder 13.

The channel for estimating (measuring) the initial random phase of the signal of the frequency converter contains a fourth signal multiplier 14, the first input of which simultaneously receives the sum of AM and frequency modulated signals from the intermediate frequency amplifier of the receiver, the first signal adder 15, the third low-pass filter 16, the eleventh signal multiplier 17, the ninth multiplier signals 18, the eighth signal multiplier 19, the third sine wave generator 20, the third control element 21, the third phase shifter 22, the second adder 23, the second phase shifter 24, the second generator s nusoidal oscillations 25, the second control element 26, the twelfth signal multiplier 27, the tenth signal multiplier 28, the fifth signal multiplier 29, the first input of which simultaneously receives the sum of AM and CT modulated signals from the intermediate frequency amplifier of the receiver, the third signal adder 30 and the fourth low-pass filter 31 .

The channel demodulating the signal of the frequency converter contains a sixth signal multiplier 33, the first input of which simultaneously receives the sum of AM and frequency modulated signals from the intermediate frequency amplifier of the receiver, an integrator 34, a threshold device 35, from the output of which useful information about the frequency signal and the fifth signal adder are taken 32.

The device operates as follows.

1) In the demodulation mode of the AM signal, a signal of the form arrives at the first input of the signal multiplier 1 from the output of the intermediate frequency amplifier of the receiver

Here:

A _AM - unknown amplitude of the AM signal, carrying useful information;

And _Th - unknown amplitude of the BT signal;

A _Th - the intermediate circular frequency of the signal, known at the reception;

ω ₀ - random (unknown at the reception) initial phase of the AM signal;

φ ₁ is the random (unknown at the reception) initial phase of the BW signal;

± Δω - shift (deviation) of the frequency of the frequency signal.

Let in signal (1) the frequency deviation of the frequency of the frequency signal + Δω.

The second input of the signal multiplier 1 receives voltage from the phase shifter of signal 4 through 90 °

Here:

- оценка (измеренное значение) начальной фазы сигнала AM, которое поступает из канала оценки (измерения) начальной случайной фазы сигнала AM

- estimation (measured value) of the initial phase of the AM signal, which comes from the channel of estimation (measurement) of the initial random phase of the AM signal

At the output of signal multiplier 1, then we have

, на выходе ФНЧ 2, имеющем частоту среза много меньше Δω, получимWith high accuracy in estimating the initial phase of the AM signal, i.e., with

, at the output of the low-pass filter 2, having a cutoff frequency much less than Δω, we obtain

, которое поступает на выход устройства.From the output of the low-pass filter 2, the voltage (4) is supplied to amplifier 3 with a gain of K _y = 2, where the evaluation (demodulated value) of the AM signal is performed

that goes to the output of the device.

Now suppose that in signal (1) the deviation of the frequency of the BH signal is Δω.

The second input of the signal multiplier 1 also receives voltage (2).

At the output of signal multiplier 1, then we have

, на выходе ФНЧ 2 с частотой среза, много меньшей Δω, будем иметьWith high accuracy in estimating the initial phase of the signal AM, to

, at the output of the low-pass filter 2 with a cutoff frequency much less than Δω, we will have

.From the output of the low-pass filter 2, the voltage (6) is supplied to amplifier 3 with a gain of K _y = 2, where the estimate (demodulated value) of the AM signal is also performed

.

2) In the evaluation (measurement) mode of the initial phase of the AM signal, a signal of the form (1) is also supplied to the first input of the signal multiplier 5 from the output of the intermediate-frequency amplifier of the receiver.

The second input of the signal multiplier 5 receives voltage from the signal multiplier 8 type

Let the frequency deviation in the signal (1) + Δω, then the signal at the output of the signal multiplier 5 has the form

This signal is fed to the input of the low-pass filter 6, which has a cutoff frequency much less than Δω, therefore, the control signal receives the control signal 7

.which adjusts the initial phase of generator 8 until it becomes

.

Let the frequency deviation in the signal (1) be Δω, then the signal at the output of the signal multiplier 5 has the form

This signal is fed to the input of the low-pass filter 6, which has a cutoff frequency much less than Δω, therefore, a control signal is fed to the input of the control element 7

.which adjusts the initial phase of generator 8 until it becomes

.

3) In the mode of estimating the amplitude of the BW signal, a signal of the form (1) is received at the first input of the signal multiplier 10 from the output of the intermediate frequency amplifier of the receiver. Let the frequency deviation of the frequency signal + Δω.

The second input of the signal multiplier 10 receives voltage from the output of the signal adder 13

Then at the output of the signal multiplier 10 and at the input of the low-pass filter 11 we have

, на выходе ФНЧ 11 с частотой среза, много меньшей Δω, будем иметьWith a high accuracy of the estimation of the initial phase of the BH signal, i.e.

, at the output of the low-pass filter 11 with a cutoff frequency much less than Δω, we will have

Now let the frequency deviation of the frequency signal -Δω.

The second input of the signal multiplier 10 receives voltage from the signal adder 13

Then, at the output of the signal multiplier 10 and at the input of the low-pass filter 12, we have

, на выходе ФНЧ 11 с частотой среза, много меньшей Δω, будем иметьWith a high accuracy of the estimation of the initial phase of the BH signal, i.e.

, at the output of the low-pass filter 11 with a cutoff frequency much less than Δω, we will have

.The voltage (14) or (17) is fed to the input of the amplifier 12 with a gain of K _y = 2, where the amplitude of the signal is estimated

.

4) In the evaluation mode of the initial phase of the BH signal, a signal of the form (1) is received at the first inputs of the signal multipliers 14 and 29 from the output of the intermediate frequency amplifier of the receiver.

Signals with voltages respectively arrive at the second input of signal multipliers 14 and 29 from signal multipliers 17 and 27, respectively.

Here:

- оценка (измеренное значение) амплитуды сигнала ЧТ, значение которого определяется в канале оценки сигнала ЧТ;

- an estimate (measured value) of the amplitude of the BT signal, the value of which is determined in the channel for evaluating the TB signal;

- оценка начальной фазы сигнала ЧТ.

- Estimation of the initial phase of the PT signal.

Consider the case when the frequency deviation in the input signal (1) is + Δω, then at the output of the signal multiplier 14 and the first input of the signal adder 15 we have a voltage

In the signal adder 15, the voltage equal to the first term of the voltage (20) is subtracted from the voltage (20), which is formed at the output of the signal multiplier 18, therefore, at the output of the signal adder 15 and at the input of the low-pass filter 16 we have

Thus, at the output of the low-pass filter 16, which should have a cutoff frequency much less than 2Δω, we have the voltage applied to the first input of the signal adder 23

Consider what voltage is supplied at this moment to the second input of the signal adder 23.

At the first input of the signal multiplier 29, we also have voltage (1) with a frequency deviation + Δω.

The second input of the signal multiplier 29 receives voltage from the output of the multiplier 27 of the form (19).

Then, at the output of the signal multiplier 29 and the first input of the signal adder 30, we have a voltage

In the signal adder 30, the voltage equal to the first term of the voltage (23) is subtracted from the voltage (23), which is generated at the output of the signal multiplier 28, therefore, at the output of the signal adder 30 and at the input of the low-pass filter 31 we have

Thus, at the output of the low-pass filter 31, which should have a cutoff frequency much less than 2Δω, we have the voltage supplied to the second input of the signal adder 23

не станет равным φ₂.Thus, at the output of the signal adder 23 we have a voltage of the form (22), which acts on the control elements 21 and 26, which adjust the phases of the controlled oscillators 20 and 25, when the channel of the initial phase of the signal is evaluated

will not be equal to φ ₂ .

It can also be shown that when the input signal (1) acts with a frequency deviation -Δω, the same thing happens, that is, at the first input of the signal adder 23 we will have a voltage of U ₁₆ = 0, and at the second input

Thus, at any moment of time, the initial phases of the tunable generators 20 and 25 will be tuned.

If the input signal (1) does not have a clock signal, then at the outputs of the signal multipliers 17 and 27 we will have zero voltages, and the channel for evaluating the initial phase of the signal will not work.

5) Consider the operation of the device in the mode of demodulation of the FM signals. A signal of the form (1) also arrives at the first input of the signal multiplier 33. At its second input, a signal comes from the output of the signal adder 32

Let the frequency deviation in the signal (1) + Δω, then the signal at the output of the signal multiplier 33 has the form

This voltage is supplied to the input of the integrator 34.

The first, second, third, fourth and fifth terms of expression (11) change in time with a frequency of 2ω ₀ t, 2Δωt and Δωt. Therefore, the effect of their integration during the duration of the elementary parcel T _{0 is} very small, and these terms can be neglected.

на выходе интегратора будем иметьAt

at the output of the integrator we will have

Let now the frequency deviation in the signal (1) -Δω, then the signal at the output of the signal multiplier 33 has the form

This voltage is supplied to the input of the integrator 34.

The first, second, third, fourth and fifth terms of expression (29) change in time with a frequency of 2ω ₀ , 2Δωt and Δωt. Therefore, the effect of their integration during the duration of the elementary parcel T _{0 is} very small, and these terms can be neglected.

на выходе интегратора будем иметьAt

at the output of the integrator we will have

From the output of the integrator 34, the voltage (28) or (30) is supplied to the input of the threshold device 35, which determines U ₃₄ more or less than 0.

If U ₃₄ > 0, then a decision is made that "0" was transmitted.

If U ₃₄ <0, then a decision is made that "1" was transmitted.

The application of the proposed demodulator in radio stations will allow for simultaneous telephone conversations in AM mode and data transmission in the PT mode in a single radio channel.

Literature

1. V.I. Tikhonov, N.K. Kulman. Nonlinear filtering and quasi-coherent signal reception. Moscow, Soviet Radio, 1975

2. G.V. Kozhukhov. Demodulator AM and TH signals. RF patent for the invention No. 2287217 (prototype).

Claims (1)

A demodulator of AM and CT signals, containing eight signal multipliers, two low-pass filters (low-pass filters), two amplifiers with a gain of K _y = 2, two sinusoidal oscillation generators, two phase shifters that shift the initial phases of the signals received at their input by 90 ° , an integrator, a threshold device and three signal combiners, characterized in that a third sine oscillator, four signal multipliers, one phase shifter, shifting the initial phase of the input d signal at 90 °, two signal adders and three low-pass filters (LPF), the input of the first LPF connected to the output of the first signal multiplier, the first input of which is connected to the first inputs of the second, third, fourth, fifth and sixth signal multipliers and is an input devices, and the second input is connected to the output of the first phase shifter, the input of which is connected to the output of the first sinusoidal oscillator and to the first input of the seventh signal multiplier, the output of which is connected to the second input of the second signal multiplier Whose output is connected to an input of the second low pass filter whose output is connected to the input of the first control element, whose output is connected to the input of the first generator of sinusoidal oscillation, the second input of the seventh multiplier signal is coupled to a first input of an eighth multiplier signals and with output of the first amplifier with a gain of K _in = 2, the output of which is the output of a device that has an estimate of the amplitude of the AM signal, the input of the first amplifier is connected to the output of the first low-pass filter, the second input of the eighth signal multiplier with is single with the output of the first phase shifter and with the second input of the first signal multiplier, the output of the eighth signal multiplier is connected to the second inputs of the ninth and tenth signal multipliers, the second inputs of which are connected to the outputs of the eleventh and twelfth signal multipliers, the output of the ninth signal multiplier is connected to the second input of the first signal adder the first input of which is connected to the output of the fourth signal multiplier, and the output is connected to the input of the third low-pass filter, the output of which is connected to the first input of the second sum a signal, the second input of which is connected to the output of the fourth low-pass filter, the input of which is connected to the output of the third signal adder, the second input of which is connected to the output of the tenth signal multiplier, and the first input with the output of the fifth signal multiplier, the second input of which is connected to the output of the twelfth signal multiplier, the input of which is connected to the output of the second generator of sinusoidal oscillations and the input of the second phase shifter, the input of the second generator of sinusoidal oscillations is connected to the output of the second control element which is connected to the output of the second signal adder and to the input of the third control element, the output of which is connected to the input of the third sine wave generator, the output of which is connected to the input of the third phase shifter and to the first input of the eleventh signal multiplier, the output of which is connected to the second input of the fourth signal multiplier, the output of the second and third signal phase shifters is connected to the first and second inputs of the fourth signal adder, the output of which is connected to the second input of the third multiplier with latter is present, whose output is connected to the input of the fifth low-pass filter, whose output is connected to an input of the second amplifier with a gain K _v = 2, the output of which is coupled to second inputs of the eleventh and twelfth multipliers signals, in addition, outputs of the second and third phase shifters are connected to the first and second the inputs of the fifth signal adder, the output of which is connected to the second input of the sixth signal multiplier, the output of which is connected to the input of the integrator, the output of which is connected to the input of the threshold device, the output of which is Exit signal demodulator Th.