DE1032342B - Modulation device using the Hall effect - Google Patents

Description

If the greatest possible zero point constancy is to be achieved with a direct current amplifier, the carrier frequency method is best used. The DC measuring voltage to be amplified is converted into an AC voltage by a relay chopper and then amplified by an AC amplifier. The conversion of the direct voltage can also be carried out in an alternating current controlled switching rectifier or in a ring modulator. Recently, the Hall effect has also been used in semiconductors for the purpose of modulation. A so-called shaft generator is essentially a rectangular plate made of a semiconducting material which has a high mobility of electrons or holes. If a current is introduced or discharged on two opposite sides of the plate and the surface of the plate is penetrated by a magnetic field, a voltage, the so-called Hall voltage, can be picked up on the sides where there is no power connection. This Hall voltage is proportional to the current flowing through the plate and the magnetic field. Such a Hall generator can be used in two different ways for modulating an alternating current with a fluctuating direct voltage. Firstly, the direct current quantity can be fed to the Hall generator as current and the carrier frequency can be passed through the Hall generator as a magnetic alternating quantity of constant amplitude. An alternating voltage proportional to the direct current is then obtained on the two free sides of the generator. But you can also feed the direct current through the turns of a coil with an iron core and then get a magnetic field proportional to the direct current. The carrier frequency flows through the semiconductor wafer as an alternating current of constant amplitude. The tapped Hall voltage is then also proportional to the fluctuating direct current. Both methods have serious disadvantages. In the first method, the alternating magnetic field in the conductor loop in which the Hall voltage arises induces an additional alternating voltage, which is noticeable as a zero point error in the carrier frequency direct current amplifier. This induced alternating voltage can only be compensated to a certain extent, since the Hall voltage is also superimposed on the second harmonic in addition to the fundamental wave of the carrier frequency. In the second method, in order to achieve good efficiency, the magnetization circuit must run largely in a ferromagnetic material. Such materials are always affected by hysteresis; therefore, a residual field strength modulation device still remains with a measuring current of zero
using the hall effect

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dr.-Ing. Heinrich Kalusche

and Dipl.-Ing. Viktor Stigler, Karlsruhe,

have been named as inventors

unknown size and sign exist, which are also reflected in a subsequent DC amplifier acts as a zero point error.

The above-mentioned disadvantages are achieved with a modulation device that makes use of the Hall effect, wherein a modulation voltage is the magnetic field of a Hall generator via an electromagnet Affected with iron core, resolved when, according to the invention, the electromagnet at the same time by one High frequency current is magnetized. The following expression results for the Hall voltage:

where R ₁ , - ^ H = + H '^ sin «j ₂ i and ω _{χ is} the carrier frequency and o> _{2 is} the high frequency. H ₌ and H ~ are the amplitudes of a magnetic constant or alternating field. The Hall voltage thus contains the frequencies Cu ₁ , ω ₂ + Cu ₁ and CO ₂ -OJ ₁ as the modulation product. The frequencies O) ₂ IcO ₁ , which are caused by the HF pre-magnetization, can easily be eliminated by filters, so that the Hall voltage after the sieving

= R _h -1 ^ sin

1,

where R _{h is} only proportional to the constant magnetic field, i.e. the desired modulation product remains. The residual magnetism of the iron circle, which would otherwise be present as a result of the hysteresis, can no longer interfere, since the iron core is constantly controlled as a result of the HF magnetization and therefore remanence can no longer be effective.

The high frequency current in the bias coil naturally also induces a high frequency

809 557 / 28S

voltage in the DC winding of the magnet. This can also be done by an upstream Low-pass filter must be kept away from the input terminals of the modulator. The same effect is achieved when both RF magnetization and DC magnetization are over the same coil take place.

The invention is explained in more detail in the drawing.

Fig. 1 shows the actual modulator;

Fig. 2 shows a block diagram of the equipment required for a carrier frequency amplifier represent.

In Fig. 1, a semiconductor wafer 2 is attached in the air gap of an electromagnet with an iron core 1, on the opposite sides α and b a circuit with the current / is applied. The modulated Hall voltage is picked up on sides c and d of the semiconductor wafer. The electromagnet 1 is provided with two coils 3 and Ί, one of which is used as a direct current control winding and the other for HF bias. Both coils can also be combined in one winding.

In Fig. 2, 5 represents an alternating current amplifier, the over a low-pass filter 6 from a Hall modulator 7 is charged with an alternating voltage modulated according to the input direct current. Between the input terminals and the Hall modulator there is a low-pass filter 8, which is the one in the Hall modulator high frequency that occurs at the input terminals. The low-pass filter 6 prevents the in the modulated AC voltage occurring high-frequency components penetrate the AC amplifier. A high frequency generator 9 supplies the Hall modulator with the required high frequency. A Carrier frequency generator 10 supplies both the Hall modulator and a phase-sensitive one Rectifier 11 with the carrier frequency. The phase-sensitive rectifier forms the amplified AC voltage back into DC voltage.

Claims (6)

Patent claims: 1. Modulation device using the Hall effect, with a modulation voltage influences the magnetic field of a Hall generator via an electromagnet with an iron core, characterized in that the electromagnet is simultaneously magnetized by an HF current. 2. Modulation device according to claim 1, characterized in that the RF magnetization of the electromagnet has a special Winding takes place. 3. Modulation device according to claim 1, characterized in that the RF magnetization is also taken over by a winding for the modulation voltage. 4. Modulation device according to claim 1 or the following, characterized in that the RF voltage induced in a winding for the modulation voltage through a low-pass filter of the modulation voltage source is disconnected. ' 5. Modulation device according to claim! or following, characterized in that a Low-pass filter holds back the HF voltage contained in the Hall voltage. 6. Modulation device according to claim 1 or the following, characterized in that it is used in a DC amplifier device. 1 sheet of drawings © 809 557/289 6.58