DE1256707B - Adjustable equalizer circuit like a Bode equalizer - Google Patents

Description

GERMAN 455i7 * W PATENT OFFICE

EXPLORATION PAPER H04m

German class: 21 a2 - 36/13

Number: 1 256 707

File number: S 102079 VIII a / 21 a2

J 256 70T filing date: July 31, 1962

Opened on: December 21, 1967

The invention relates to an adjustable equalizer circuit in the manner of a Bode equalizer with a frequency-dependent Operating damping, in which the ohmic terminating resistances of the two auxiliary poles can be changed to set the desired damping are.

In electrical communication systems, circuits are required whose frequency-dependent or frequency-independent operating damping can be set. With many such circuits a real resistance is used as the setting element, the value of which is changed. In addition However, potentiometers and rotary resistors are unsuitable because the contacts are unreliable. Usually Switches are used that allow a larger number of fixed resistors to be selected can be switched on. Disadvantages are, among other things, those that are still present Contacts that can only be adjusted gradually, the sudden change in resistance when switching over and the large number of components required.

The so-called magnetoresistive effect in semiconductors is known. It's also from the magazine "ETZ", edition A of August 1, 1955, issue 15, pp. 513 to 517, known the ohmic resistance value of semiconductors through a magnetic field. By a changeable stream becomes this generates a correspondingly changing magnetic field through which the ohmic resistance value is controlled in a resistance body with galvanomagnetic effect. In this reference however, it is expressly pointed out that it was only possible to use the lowest temperatures in bismuth to achieve such a large change in resistance in the magnetic field that a real amplification is possible. In addition, it is further emphasized that this interesting application possibility until At the time of this publication it was not yet possible to establish itself in the technology, because the galvanomagnetic Effects recently were very small, and it is also concluded that they lead to change In this condition materials would have to be found whose properties are beyond those of bismuth and germanium go far beyond.

From the German patent specification 839 220 are also known fine resistance regulators, which are called magnetic field-dependent Resistors, such as semiconductors, are formed and used for control purposes. the Changes in resistance in a bismuth body used as a semiconductor can thereby be carried out be that, for example, the bismuth body in an adjustable equalizer circuit like a Bode equalizer

Applicant:

Siemens Aktiengesellschaft, Berlin and Munich, Munich 2, Wittelsbacherplatz 2

Named as inventor:

Dr.-Ing. Johann-Gerhard Zirwas.

Unterpfaffenhofen

held in an unchangeable position and the magnet is arranged adjustable or that both in unchangeable Can be left position and the magnet either provided with a magnetic shunt or whose field is generated and controlled electromagnetically. In addition, the bismuth body can be opposite be moved in a fixed field. The disadvantage here, however, is that such a magnetic field semiconductors that can be influenced in their ohmic resistance value, such as e.g. B. bismuth, a very high one Have temperature coefficients, which is why one often avoids the use of such controlled semiconductors and preferably conventional resistors are used, although the aforementioned Disadvantages must be accepted.

In addition, an adjustable voltage divider arrangement is known, in which, using the dependence of the effective resistance value of magnetic field-sensitive substances on a variable magnetic field, two resistance _{sections of a magnetic field-dependent resistance body from a semiconducting A w} B _v connection located on both sides of a voltage divider, are arranged in such a way that the resistance of the two resistance bodies or resistance sections changes in the opposite sense under the influence of the changing magnetic field, with the approximate preservation of the total resistance of the arrangement. The change in the magnetic field can take place by mutual movement of the resistance bodies and the means generating the magnetic field or by adjusting a part which is movable in the field and more or less shields the resistors. To generate the magnetic field strength, a permanent

709 709/337

Claims (1)

use magnet. However, such an arrangement is not suitable for use in equalization networks suitable, since the two resistors are electrically connected directly to one another. The object of the invention is to utilize the magnetoresistive effect in semiconductors adjustable equalizer circuit like a Bode equalizer, especially for communication systems, to create in which the aforementioned disadvantages of known equalization circuits are avoided. The equalization circuit is designed according to the invention so that two terminating resistors each of which can be influenced in its ohmic resistance value by a magnetic field, as a platelet trained semiconductors are used, which are each arranged in an air gap of a Ε-shaped magnet system, on the middle of the a winding for the setting current is applied to its end, rectangular reinforced beam whose two outer legs consist of permanent magnets of opposite polarity. The design of an equalizer according to the invention means that not only those explained at the outset are explained Disadvantages of the known adjustable equalizer circuits avoided. Will this be adjustable When the equalizer is used in an automatically operating control circuit, there are advantages from the inertia-free reaction of the semiconductor to the field change. So far, in control loops NTC thermistors are mostly used for automatic control. But this is a great temperature dependency connected, which is avoided in an equalization circuit according to the invention. Da Bode equalizer two oppositely controlled resistors required, two magnetic field-dependent can be used in the sense of the invention Semiconductor resistors are particularly advantageously arranged so that they are through the Control current of a single electromagnet are controlled in opposite directions. The invention is described with reference to the embodiment shown in the figure. The figure shows the circuit of an equalizer with frequency-dependent damping, which is designed as a Bode equalizer in a known manner with the two series resistors Z and the bridging resistor R. The input terminal pair is designated with 1, 1 ' and the output terminal pair with 2, 2' . The frequency dependence is determined by the auxiliary four pole VPI and FPII, whose input is parallel to the resistor i? or in series with the resistor. The damping stroke is determined by the oppositely controlled resistors _j R ₁ and R ₂ . According to the invention, these are designed as field plates (semiconductor wafers) and are located in the air gaps S ₁ and S ₂ . By the two permanent magnets NS and N'S 'is in each case generates a permanent magnetic field in the two air gaps, which is superimposed on the magnetic field of the winding W, if this winding _S is energized through the terminals K by a SteuerstromJ. This increases the resulting field in one air gap while it decreases in the other air gap. Since the resistance of the field plate depends on the magnetic field strength, the damping of the equalizer is controlled with it. If no adjustment is made, it is sufficient to change _{only the resistance ii 1} or R _2. The use of quadrupole poles can also be dispensed with if the resistors R or Z are bridged in a known manner with frequency-dependent two-pole poles or connected in series and one or the other resistor Z or R or both of them are brought into the controlling magnetic field as field plates. Claim: Adjustable equalizer circuit in the manner of a Bode equalizer with frequency-dependent operating attenuation for setting the desired Attenuation the ohmic terminating resistances of the two auxiliary poles can be changed, characterized in that two terminating resistors are each replaced by a magnetic one Field which can be influenced in its ohmic resistance value, designed as a plate Semiconductors are used, each of which is in an air gap of a Ε-shaped magnet system are arranged, on the middle, at its end rectangular reinforced bar a Winding for the setting current is applied and its two outer legs made of permanent magnets opposite polarity exist. Considered publications:
German Patent No. 839 220;
German interpretative document No. 1,069,755;
»Electrotechnical Journal«, Issue A
(ETZ-A) from August 1, 1955, no. 15, pp. 513 to 517. 1 sheet of drawings 709 709/337 12.67 © Bundesdruckerei Berlin