SU363182A1 - FRACTURING LINK ACTIVE;? S-FILTER - Google Patents

Description

This invention relates to the field of radio engineering.

The fractional link of the active 7 C-filter is known, containing an operational amplifier and a double T-shaped RC-uocf, whose forward input arms are separated and connected to the input source and to the output of the operational amplifier through a resistive divider.

However, this link does not provide separate adjustment and filter settings.

In the proposed link, an additional capacitor is connected between the junction of two consecutive resistive arms of the T-shaped bridge and the output of the operational amplifier.

The drawing shows the scheme of the proposed fractional link.

The serial shoulders of the double T-bridge 1 at the input are separated by a resistor 2, which together with the 3 n 4 resistors form the main voltage divider. An additional capacitor 5 is connected between the point of connection of two resistive series double bridge arms / and the output of the operational amplifier 6 (terminals 7 and 8 are closed) or the output of the input source 9 (terminals 7 and 10 are closed).

In the case that terminals 7 and 10 are closed, the fractional link transfer function is

, A: TI

I - - I

; d: W

D,

III - Il2S +

+ j x-ta

where X is

(B is the frequency of tuning the double bridge 1, C, L2 are the transfer coefficients of the main voltage divider on the resistors 2, 3. 4;

DS - attenuation of the loaded double bridge 1;

i is the gain of amplifier b; , / i2 - coefficients, the values of which are proportional to the resistance of the resistor 2 or when changing places of the bridge 1.

. / IN

J -

 /

F (x)

DII / XTI

- (Y14-M-5 + + L - - -

JJ-, 2- /

here

 -} /

R, R,

, Rs, R - resistance values of resistors 2, 3, 4, respectively;

b - coefficient depending on the ratio of the capacities of the additional capacitor 5 and the capacitor in the parallel arm of the double bridge.

If you close the terminals 7 and 8, then the corresponding formulas will take the form

Dn

AI 4- AJ + S +

+ J -

VXTs

J XTi -

JCr i

F (x)

H

- (fti + Lg) + 5

+ L--

 X

2

By selecting 6 fti + / Z2, it is possible to obtain absolute zeros of the transmission coefficients of the double bridge / both in the feedback circuit and in the direct transmission circuit.

The elimination of detuning along these two circuits using a conventional amplifier has a positive effect on the parameters of the fractional link. At the same time, the possibility of obtaining a given feedback loop detuning allows

in the circuit, an operational amplifier and take advantage of the resulting benefits.

It is necessary to emphasize both small values of the capacities of additional capacitors (approximately DQ times less than the values of capacitors in the parallel arm of a double bridge) and low requirements for its stability (Q times softer than usual requirements for the stability of bridge elements) . Here, D and Q are the attenuation of the double bridge / and the quality factor of the device, respectively.

Subject invention

The fractional link of the active C-filter, containing an operational amplifier and a double T-shaped / C-bridge, whose serial input arms are separated and connected to the input source and output of the operational amplifier through a resistive divider, characterized in that in order to ensure separate adjustment and filter settings while simplifying the design, an additional capacitor is connected between the junction of two successive resistive arms of the T-shaped bridge and the output of the operational amplifier.

R

CI3p

L

iJ