SU77480A3 - Phase Modulation Method - Google Patents

Description

In the known phase modulators, the carrier voltage is divided into two phase-shifted voltages that are differentially modulated in amplitude and then added again. In this case, to obtain the most linear modulation, the two carrier voltages of equal amplitude must have a phase difference of 90 °.

According to the proposed phase modulation method, amplitude modulation is performed only on one of the carrier voltages. According to the invention, the amplitude-modulated voltage is added to the carrier that is phase-shifted by 135 °, and the amplitude of the modulated voltage is 0.707 of the amplitude of the unmodulated voltage. By properly regulating a single modulator system, one can obtain results that in practice are not inferior to the two-carrier modulation action.

FIG. Figure 1 shows a phase modulator block diagram in which two amplitudes of carrier voltages are out of phase and differentially modulated in amplitude, after which they are again added together; in fig. 2 blockhema device operating on the proposed method; here, the two carrier voltages are unequal in amplitude and phase shifted, but only one of them is modulated in amplitude, then these voltages are added and the resulting voltage is thus modulated in phase and also to some extent and in amplitude; in fig. 3 and 4 are diagrams of two variants of the device according to FIG. 2; in fig. 5 is a schematic diagram of the phase modulator shown in FIG. one.

In the device (FIG. 1), the source voltage source is connected to the modulator 3 via the phase shifter 2, and to the modulator 4 directly. The modulating voltage from the input is supplied differentially to modulators 3 and 4 via transformer 5, i.e., with a phase difference of 180 °. Both amplitude-modulated carriers

No. 77480-2 output is added, resulting in voltages varying in phase within the limits depending on the initial phase difference of the unsigned voltages supplied to the modulators 3 4.

FIG. Figure 2 shows a device in which only one of the two different phase voltages is modulated. The source voltage source 1 is connected through an amplifier 6 to the power supply circuit, and through the phase shifter 7 to the modulator 8. The output of the modulator is also connected to the power supply circuit. The modulating voltage is supplied only to the modulator 5; the amplifier 6 is a valve protecting the modulator 8 from the possibility of parasitic oscillations.

Mathematical analysis shows that both types of modulators with a given depth of amplitude modulation of the component voltages (both or one depending on the circuit) give the same phase and some undesirable amplitude modulation. The advantage of a single module system is its comparative simplicity.

If the modulators 3 Е4 (Fig. 1) or the amplifier 6 and the modulator 8 (Fig. 2) also function as frequency multipliers, then the initial phase difference of the carrier voltages also increases. If, for example, the frequency is doubled, then the initial phase difference in the circuit of FIG. 1, set by the phase shifter, must be equal to 45 ° or 135 °, after doubling the frequency, the phase difference will be equal to 90 ° or 270 °.

In the above case, the modulators perform two functions: modulate the amplitude according to the signal and multiply the frequency. Such a modulator consists of a modulator lamp, the input circuit of which is tuned to the carrier frequency and the output to the desired, in this case the second, harmonic. If desired, the functions of the modulator and the multiplier can be divided; in this case, after the usual modulator lamp, a separate multiplication lamp is switched on.

The modulating voltage is supplied to the modulators 5 and - in a push-pull circuit via a transformer 5. The modulated load voltages are added to the common anode circuit of the modulators 5 and, or in the last stage of the frequency multipliers, if used.

If in the diagram of FIG. 2, the frequency is doubled, the phase shift in the phase shifter 7 must be equal to 67.5 ° or 112.5 °, so that after multiplying the phase difference is equal to 135 ° or 225 °. Amplifier 5 acts as a frequency multiplier, and a modulating voltage is applied to the modulator 8 so that it acts as a modulator and as a multiplier. Summation occurs in the common anode circuit.

Frequency multipliers can be included before or after the modulators, but in any case before summation, since otherwise it would not be possible to reduce the required initial phase difference of the carrier voltages.

In the circuit of FIG. 3, only one of the two collapsible voltages is modulated. The source / connected circuit 9, tuned to the carrier frequency. The phase shifter RC operates in conjunction with a push-pull tuned circuit 9 so that the GI and GZ grids of amplifier 6 and modulator 8 are supplied with a voltage differing in phase by 135 °, which is the best for a modulator of this type. The phase shifter RC also reduces the voltage amplitude; the magnitude of the latter is chosen so that the voltage amplitude supplied to the modulator 8 is 0.707 amnlity of the voltage supplied to the amplifier 6. The total voltage arises in tuned circuit 10, to which anodes 11 c 12 are connected and tuned to the carrier frequency. The modulating voltage is supplied via jack 13 and transformer 14 to the locking grid 15 of the modulator 8. A transmitter 16 is connected to circuit 10.

In the diagram of FIG. 4 modulators and an amplifier lamp simultaneously operate as frequency multipliers. The carrier frequency is taken from a quartz-stabilized oscillator 17. A quartz PC is connected to the oscillator lamp grid, and a tuned circuit 18 is included in the anode circuit of this lamp.

Through the phase shifter RC, the voltage is supplied to the grid of the GI modulator and multiplier lamp 19, and through the capacitor Ci to the grid of the G yu-laying lamp 20. The capacitor C serves to control the amplitude. Without frequency multiplication, a phase difference of 135 ° would be needed, but with frequency doubling, the initial phase difference should be 67.5 °; The phase shifter RC is adjusted to this value. The capacitor Ci can adjust the voltage applied to the lamp 20 so that the amplitude of the voltage at the output of the lamp 19 is 0.707 of the amplitude of the voltage at the output of the lamp 20. The modulating voltage is supplied in the same way as in the diagram in FIG. 2. Circuit 21 is tuned to the desired harmonic carrier frequency.

The circuit of FIG. 5 illustrates a method of multiplying a frequency in a differential modulator in which both multiplier stages are modulated. When the frequency is doubled, the loop 22 is tuned to the second harmonic of the carrier frequency created in loop 23 by the generator 24: the phase shifter RC is set to a phase shift of 45 °; the amplitudes of both voltages are equalized by the capacitor Cj. The modulating voltages are fed through a push-pull transformer 25 to the anti-single-grid grids 26 and 27. With an initial phase difference of the carrier voltage of 45 °, the phase difference of the modulated voltages at the anode prices x lamps 28 and 29, due to doubling, will be 90 °. The voltage supplied through the transformer 25 thus modulates in phase the energy arising in the tuned circuit 22 within 9 (F on either side of the middle of the specified limit.

The ratio of the amplitudes of the two collapsible voltages is controlled either by the anode voltage selection of modulators, amplifiers or multipliers, or by a variable capacitor, as in FIG. 4 and 5.

There are various options described schemes. In the diagram of FIG. 5 you can, for example, triple the frequency; in this case, the RC phase shifter is adjusted by a phase shift of 30 °. Anode circuits can be connected in parallel, as shown in the diagram, or on a push-pull circuit. In the latter case, the phase changes from 90 ° to 270 °, which, in terms of modulation depth and distortion, does not matter, but can improve the effect of the multipliers.

In a dual modulator, the device shown in FIG. 3 phase shifters and make modulators work as doublers. This phase shifter gives a shift of 135 °, which after doubling gives a phase difference of 270 °, i.e. the optimum value.

Subject invention

A phase modulation method using multiple channels and amplitude modulation, characterized in that the amplitude modulated voltage is added to a carrier that is out of phase by 135 °.

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