SU69061A1 - Amplification path with phase correction - Google Patents

Description

In amplifiers whose cascades are interconnected using passive quadrupoles, the phase shifts in frequency increase from stage to stage because the frequency-phase characteristics usually have a negative frequency derivative, resulting in positive phase shifts in the low-frequency region and negative in the high-frequency region (Fig. I). This complicates the correction of amplifiers and extremely complicates the use of deep contrast.

In the proposed amplifier, the noted deficiency does not occur, due to the introduction of an intermediate stage, covered by a deep counter-current, the voltage of which passes through a link having a normal frequency-phase characteristic with a negative frequency derivative.

This feature of the proposed amplifier and constitutes the essence of the present invention, explained in the following description and FIG. 2-11.

FIG. 2 shows the usual circuit of the amplifier stage, covered by a deep counter-current. If the complex values of the cascade gain factor without feedback and the feedback coefficient are written in the form | K | and, respectively, 1/5 | -e, the gain coefficient of the cascade with feedback will be.

If. g

ifK

J (4K + fsi)

,

l | 8 | -e-Jfi)

(one)

From this expression it follows that the shift between the output and input voltages of the cascade with a strong negative feedback is almost equal to the phase shift introduced by the feedback circuit, and opposite to its sign.

Therefore, if the amplifier stage is turned on, performed according to the scheme of FIG. 2, in the path, the frequency-phase characteristic of which is necessary to compensate, then giving a circuit D

93 a normal phase characteristic with a negative frequency derivative (Fig. La), one can obtain a frequency-phase characteristic of the cascade with a positive frequency derivative (Fig. 1b), which can be widely used for correction and stabilization purposes. However, the main condition for the stability of such a corrector will be compliance with the criteria that the diagram in polar coordinates, expressing the dependence of the DSD vector on frequency (Fig. 3), should not cover the points and (2) This condition imposes a known restriction on the value of the limiting compensation shift, which will lie between 90 and 180 °. If a larger compensation angle is required, then several such cascades should be installed in series. The described method can be widely used to compensate for phase distortions where it is required, for example, in telegraph and even in television installations, but its application should be particularly effective in stabilizing amplification paths with large phase shifts covered by deep counter-relation. The skeletal diagram of the proposed tract with deep contrast is shown in FIG. 4. Here, / is the main amplification path, at the output of which a filtering link is inserted, which significantly attenuates the ultrasonic harmonics of the distortions at the output of the high-power stage and allows limiting the width of the probable generation frequencies 2.5-3 times the width of the useful spectrum. The opposite is advisable to take from the output of the filtering link, which will reduce the frequency spectrum covered by the effective counter-current due to their rapid attenuation and completely unload the pre-amplification path from the very harmful additional load by ultrasonic harmonics that are absent at the output. True, there should be a rapid increase in negative phase shifts at the same time, however, since for the frequency band of possible generation their limiting value is precisely known, they can be easily compensated by the considered method. Next in FIG. 4, additional F / cascades are introduced into the path of additional amplification (covered by an individual deep counter-coupling in accordance with Fig. 2 and used as phase compensators. Their number is determined by the maximum phase shift F in the probable generation band of the main path (i.e. frequencies, where the K-fj of the main path is greater than 1) and can be defined as 0-180 ° fc UFK where 99f is the phase-compensation limit angle of each stage. The number of such cascades set at a low level of amplification is usually from one to three Moving to specific forms of the proposed phase compensators, it should be noted that the voltage of the individual countermeasure can be applied either to the input transformer, not to affect the input voltage, or directly, as shown in Fig. 5. In the latter case, for the input voltage source Uex, the transient resistance will represent the input load. - .. j (4) l - Kf L l + K, which cannot contribute to a significantly negative effect, since the input the resistance, although significantly reduced in magnitude, however, will have a compensating azu, and it can be chosen as large as desired. The following can be used as phase shifters in / -cei: 1. Low-frequency filters G– and

U-shaped types (Fig. 6a and b) for phase compensation at high frequencies and high frequency filters of the same types for phase compensation at low frequencies (Fig. 6c and d). The former can give a compensation angle of up to 65-70 ° with very small frequency distortions up to angles to the latter can provide twice as large compensation angles, however, generation is possible with use, since the limiting phase angle is 270 °. Thus, they must be applied jointly with phase compensators and limiters in path K (Fig. 7).

To a large extent, it reduces the danger of generating an M-type filter (for example, fig. 6e), since here it is possible only in a narrow frequency spectrum. Of interest is a circuit that uses a rationally designed transformer that simultaneously performs the functions of a high and low pass filter (Fig. 7).

2. Leveling amplitude circuits with constant input impedance (eg. Fig. 8). These schemes can produce marginal compensation shifts of the order of 120 ° without generation.

A common drawback of the quadrupole d-chain, recommended in paragraphs. 1 and 2 is an increase in the gain factor of the phase-compensation stage at the boundary and outside the compensation frequency band, which necessitates the use of frequency-amplitude limiters in the gain path, usually somewhat degrading the phase response of the path.

3. In view of this, a special integer represents the use in the circuit

opposition phase shifters with constant input impedance and output voltage (the so-called phase circuits).

The latter are known in the form of crossed (bridge) chains and, in this form, are most conveniently applicable to the push-pull scheme (for example, Fig. 9) and

T-shaped bridge circuits (with phase-wound transformer windings T), most convenient in a single-ended circuit (Fig. 10). The main property of the phase loops shown in FIG. 9 and 10, is a 180 ° limit shift monotonously increasing over the entire frequency spectrum. It is quite natural that at the specified limit shift the generation is inevitable, therefore they should be applied together with the limiters and phase compensators included in the path K. In particular, the diagrams shown in Figs. 9 and 10, can give a very high compensation effect if one chooses the parameters of the amplitude limiter i, C and the phase-compensator g, Cz, Gz, Cd in path K so that the diagram of the / C-phase compensator would satisfy FIG. 3, while the marginal shift of the yS chain would reach almost 180 ° in the compensable frequency band, and the chains in the path / would cause a phase-compensation and limiting effect.

4. Finally, of some interest are the simple phase compensator circuits of FIG. On and 116, similar in frequency response to phase compensators used previously.

This circuit makes it possible to turn any amplification stage into a phase compensator, moreover, if pentodes are used, its gain will be on the order of 6-10, i.e., within the normal range.

Subject invention

Claims (2)

1. A power path with phase correction, characterized by the introduction of an intermediate stage covered by a deep counter-current, the voltage of which passes through a link having a normal frequency-phase characteristic with a negative frequency derivative. 2. The use of the device according to claim 1 for correcting the frequency characteristics of any path by the method of reverse distortion. FIG. one FIG. 2 Sx 6. sneeze FIG. 3 , / Vu .fb FIG. four g; To / g FIG. five 4Sx - 5wz 77ra # i7 L f-TWnrjWW p-TTSSTJWnry-jJ Si fi IL 1 |. FIG. 6 waamtj With f- CH b 41- F 1 FIG. 9 Sir Mr. SJ 4fe -T-lllll / - txz  Saop's. 967 FIG. ten USuiFig. and