SU1626387A1 - Amplitude-keyed suppressed-carrier signal transmitter - Google Patents

Description

one

(21) 4650235/09

(22) 02/14/89

(46) 02.02.91. Bul №5

(71) Leningrad Electrotechnical Institute of Communications. prof. M.A. Bonch-Bruevich

(72) A.A. Alexan, V.A. Galakhov, V.L. Mozheiko and V.G. Moses (53) 621.396.61 (088.8)

(56) Transistor harmonic oscillators in a key mode. / Ed. I.A. Popov. - M.: Radio and Communication, 1985, p. 172, fig. 6.13.

(54) KEY TRANSMITTER OF AMPLIFICALLY MODULATED VIBRATIONS WITH SUPPRESSED CARRIER

(57) The invention relates to radio engineering. The goal is to reduce the envelope distortion of the output signal. For this purpose, a modulating signal is supplied to the input of the first comparator 1, as well as to the inputs of the inverter 3 and the amplifier-limiter 12, which is compared with the signal of the saw-tooth generator 4 in the first and second comparators 1 and 2 The first and second blocks of coincidence 5 and 6 form a signal with a pulse-width modulation (PWM) of twice the sampling rate, respectively, for a positive and negative half-wave modulation signal. At the output of the logic adder 7, a PWM signal is generated, corresponding to the output signal module, which is amplified by key power amplifier 8 and filtered by low pass filter 9. Key generator 10 high frequency generates a high-frequency pulse signal, which, the passage through the band-pass filter 11, forms a signal with a suppressed carrier. The high-frequency input of the high-frequency key generator 10 is supplied with a signal from the reference oscillator | 13 pulse signals through controlled phase inverter 14 controlled by amplifier-limiter 12 so that the phase of the signal at the output of controlled phase inverter 14 is reversed every half-period of the modulating signal. This allows the rejection of a balanced modulator. 2 Il.

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The invention relates to radio engineering and is intended for use in signal transmission systems over communication channels.

The purpose of the invention is to reduce the distortion of the envelope of the output signal.

FIG. 1 shows a block diagram of a key transmitter of amplitude modulated oscillations with suppressed carrier; in fig. 2 - timing diagrams explaining the operation of the scheme.

The transmitter contains the first 1 and second

2 comparators, inverter 3, generator 4 sawtooth voltage, first 5 and second 6 blocks of coincidence, logical adder 7, key power amplifier 8, low pass filter 9, high frequency key generator 10, band pass filter 11, limiting amplifier 12, reference oscillator 13 pulse signals

and controlled phase inverter 14.

The transmitter operates as follows.

To the non-inverting input of the first comparator 1, as well as to the inputs of the inverter

3 and limiting amplifier 12, a modulating signal is supplied, and the components of this signal are directly and inverted in inverter 3

in the first 1 and second 2 comparators with the voltage of the sawtooth 4 generator 4 (Fig. 2a). The signals received at the non-inverting and inverting outputs of the first 1 and second 2 comparators are shown in FIGS. 26, c, d, e, respectively. At the output of the first block 5 of coincidence, a signal with a pulse width modulation (PWM) of twice the sampling rate is generated corresponding only to the positive half-wave of the modulating signal (Fig. 2e). Similarly, at the output of the second block 6 of coincidence, a signal with a PWM is formed, corresponding to a negative half-wave of the modulating signal (Fig. 2g). As a result of the addition of these signals in the logic adder 7, the PWM signal corresponding to the output signal module (Fig. 2h) is generated at the output of the latter. This signal is amplified by a highly efficient key amplifier 8 of power to a desired level, and in the low-pass filter 9, useful low-frequency spectral components are extracted from it. As a result, the signal at the output of the low-pass filter 9 repeats in shape the absolute magnitude of the modulating signal (Fig. 2i). This signal is fed to the input of the high frequency key generator 10.

In this case, the input of the high frequency of the key generator 10 high frequency is

A pulse signal from a controlled phase inverter 14 steps up, which changes the phase to the opposite when the polarity of the modulating signal changes. Reverse phase change is performed by controlling the phase inverter 14 with the help of amplifier-limiter 12 and reference generator 13 of pulse signals. When the logical unit exists at the output of the limiting amplifier 12, the controlled phase inverter 14 does not invert the signal from the reference oscillator 13 pulsed signals, in the case of a logical zero it inverts.

FIG. 2k shows the voltage at the output of the amplifier-limiter 12, FIG. 2L is the voltage at the output of the reference generator 13 of the pulse signals, and FIG. 2m is the voltage at the output of the controlled phase inverter 14.

As a result, a high-frequency pulse signal (FIG. 2n) is generated at the output of the key high-frequency generator 10 with a required power level that coincides in phase with the signal at the output of the controlled phase inverter 14 and has an amplitude determined by the signal at the output of the low-pass filter 9.

Band-pass filter 11 suppresses the spectral components of the output signal, determined by the presence of harmonics in the pulsed high-frequency signal. As a result, the signal at the output of the key transmitter of amplitude-modulated oscillations with suppressed carrier contains only the upper and lower side frequencies (Fig. 2n),

Thus, a suppressed carrier signal is generated without the use of a balanced modulator, high linear detector, and high frequency limiter amplifier, which reduces the envelope distortion of the output signal.

Claims (1)

Claims of the invention A key transmitter of amplitude-modulated oscillations with suppressed carrier, comprising an amplifier-limiter, a sawtooth generator, the output of which is connected to the inverting input of the first and serially connected key power amplifier, low-pass filter, key high-frequency generator and band pass filter which is the output of a key transmitter of amplitude-modulated oscillations with suppressed carrier, characterized in that, in order to reduce distortion, s output, which has been entered in an inverter connected in series, the second U L lm