DE560226C - Arrangement for single sideband modulation - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
SEPTEMBER 29, 1932

REICH PATENT OFFICE

PATENT LETTERING

Vr 560226 CLASS 21 a * GROUP

Arrangement for single sideband modulation

Patented in the German Empire from July 10th τ 930

The invention relates to an arrangement for single-sideband modulation, in which the high- and low-frequency components of two modulations are phase shifted by ⁰ and 90 are combined in a common circle.

The invention is primarily distinguished from the known methods of this type characterized in that to achieve the 90 °

to phase shift of the low-frequency component in the one modulation path an implementation The low frequency takes place in modulated high frequency with any carrier frequency, a sideband through a filter sieved out and a phase-shifted carrier wave added before demodulation will.

This arrangement is shown in Fig. 1 of the accompanying drawings. In it is

ao D ₁ an independent intermediate exciter from which the carrier wave for the first modulation path is taken. This carrier wave is transmitted to the detuned circuits 1 and 2, so that the currents produced in the cathode tubes α and b are phase-shifted from one another. Instead of circles 1 and 2, other means for phase shifting can also be used.

If the vibrations in the tube a are now modulated from the line 1 and the transformer T ₁ and the modulation tube M ₁ , normal modulated waves are produced in the circuit 1 '. If these modulated waves are now passed through a filter F ₁ , which eliminates the one modulated sideband, - and if a phase of the carrier waves generated by the exciter D ₁ is added by the circuit 2, then T _{2 is obtained in the transfermator} after the demodulation in the tube d , the same audio frequencies as in the transformer T ₁ , but with a phase shift, because

id

- «J.

A sin (cot - \ - φ) -] cos (ω - p) t \

AWAY

= a.

sin (pt -j- φ)

The phase shift can always be adjusted so that it is 90 °.

It is clear that in telephony it is essential that the relative phase shift of all frequencies is equal to 90 °. Therefore, the filter F must have such a characteristic that all frequencies of the one sideband passed through are the same

*) The patent seeker stated as the inventor:

Josef von Plebanski in Warsaw.

or have almost the same phase. Otherwise, not all of the audio frequencies would be 90 ° out of phase with the original frequencies in the transformer T ₁ after passing through the transformer T _2.

If now the tubes O ₁ and O _{2 are} modulated by the modulation tubes M ₃ and M _2, which are fed by the exciter D ₂ with a mutual phase shift of 90 ° generated by the circles 3 and 4 or by another arrangement in the circle 7 , you get the difference or sum of the currents in circles 5 and 6.

In circuit 5, the current i _{s is the} same

A sin (ot + B sin oit sinfit

B B

- Asm cot - | cos (ω - p) t cos (co + p) t.

In circuit 6 the current i _{G is} equal to A coswt + B cospt cos cot

R R

= A coswt- \ cos (00— p) t- \ cos (ω

2 %

In circuit 7 the current i _{7 is} equal to A] ZzSmUt + - \ + B cos (ω— p) t

or

sin \ (ot —— I - B cos (ω + f>) t. \ 4 /

In this case, the modulation may not be deep enough due to the elimination of a sideband. As a result, the carrier wave is reduced by adding a suitable phase of the carrier wave from the exciter D ₂ via the oscillating circuit 8, and this can be done with or without amplification.

By means of the oscillating circuit 8, the phase can be set in opposite directions and thereby the carrier wave can be eliminated if necessary.

Instead of two exciters D ₁ and D ₂ , a single independent exciter can be used using the fundamental wave and possibly one of its harmonic waves. In both cases, the exciters can act directly on circuits 1, 2, 3, 4, 8, or special neutrodyne tubes can be switched on to prevent the modulation from affecting the frequency of the exciters.

The modulated one sideband to be taken at points p and q can be amplified and used in any suitable manner.

Because the regulation of the overall circuit for modulation of a sideband is a bit complicated is, so can be obtained in circuit 7 for the purpose of wave change in the transmitter Modulation with respect to their wavelength in any suitable manner, e.g. B. by superheterodyne arrangements changed will.

As already mentioned, the most essential part of the circuit according to the invention is a Filter circuit covering a frequency band with essentially the same phase shift lets through.

The filter according to FIG. 2, which takes the place of the circuits 1 'and F of FIG. 1, is best suited for this purpose.

It is known that in the case of an artificial line L (Fig. 2) the resistance R can always be chosen so that no reflected waves are present in the system. In this case- different phases can be obtained in the different branches of the line.

If a plurality of tuned circuits 8g are coupled to an artificial line at different points in the manner shown in FIGS. 2, 4, 5 and 5a, the frequency characteristic according to FIG. 3 with small phase differences is obtained in the tube V.

The above circuits can be tuned so that the phases for a frequency band stay the same.

In Figs. 2 and 4, the circles are not coupled to one another. In Fig. 5 and 5a, however, the circles are coupled to one another. Resistors are denoted by r , which can be switched on to regulate the electromotive forces in the various circuits. These circles can work on an aperiodic circle connected to the grid of a tube.

The filter can work on a second artificial line or a tuned circuit (Figures 5 and 6).

The filters shown in FIGS. 2, 4, 5, 6 can, under certain circumstances, be reversed Phase curve. So if you have the filters described above with currently known combined by z. B. they cascade in tube circuits, so the phase characteristics of the whole Arrangement can easily be made rectilinear. The phase shift for a certain Band can be the same.

Claims (12)

Patent claims: i. Arrangement for single sideband modulation, in which the high and low frequency Parts of two modulation gears are 90 ° out of phase and are combined in a common circle, characterized in that to achieve the 90 ° phase shift of the low-frequency component in one modulation path is a conversion of the low-frequency in modulated high frequency with any carrier frequency takes place that a sideband is screened out by a filter and that a phase-shifted carrier wave is added prior to demodulation. 2. Arrangement for single sideband modulation according to claim 1, characterized in that that the filter to achieve an in-phase frequency band contains an artificial line, which in any Way at points of different phase is coupled with a series of tuned circles, all of which with are coupled to an aperiodic circle. 3. Arrangement for single sideband modulation according to claim 1 and 2, characterized characterized in that in these circuits resistors are connected to the voltages from the artificial line to regulate and to reduce the effect of these circles on the artificial line to a minimum. 4- arrangement for single sideband modulation according to claim 1 and 2, characterized by mutual coupling of these circles. 5. Arrangement for single sideband modulation according to claim 1 and 2, characterized characterized in that the aperiodic output circuit is coupled only to one or to individual rather than to all circuits of the filter is. 6. Arrangement for single sideband modulation according to claim 1 and 2, characterized characterized in that one of the filter circuits directly onto the grid of a tube is working. 7. Arrangement for single sideband modulation according to claim 1 and 2, characterized by using a second artificial output line or an artificial output circuit in the filter. 8. Arrangement for single sideband modulation according to claim 1 to 7, characterized in that that the filters are cascaded with other known filters in tube circuits. 9. Arrangement for single sideband modulation according to claim 1, characterized in that that a further phase of the carrier wave is added to the modulated sideband in the common circle (7) will. 10. Arrangement for single sideband modulation according to claim 1, characterized in that that for generating the carrier waves in the one modulation path and in the common circuit two separate ones High frequency generators are used. 11. Arrangement for single sideband modulation according to claim 1, characterized in that for generating the carrier waves in one modulation path and in the common circuit only one high-frequency generator is used, from which the fundamental wave and a harmonic is used. 12. Arrangement for single sideband modulation according to claim 1 to 11, characterized characterized in that the wavelength can be changed in the common circle to change the wavelength of the transmitter. 1 sheet of drawings