Attenuator:
Attenuator Network : An attenuator network must fulfil following conditions. It must give correct input impedance, It must give correct output impedance and It must provide specified attenuation. In general, attenuation is expressed in decibel as follows, where D is the attenuation in decibel. But we can express attenuation in neper as follows, where N is the attenuation in neper. In this topic, we shall study symmetrical attenuators such as symmetrical T type, symmetrical π type, lattice type and bridged T type, alongwith asymmetrical attenuators such as ‘L’ type attenuator. Any Attenuator Network is designed for specified characteristic resistance R0 and attenuation. Let us find design equations for various Attenuator Network one by one. Symmetrical T Type Attenuators: Consider properly terminated symmetrical T network as shown in the Fig. 10.3. According to current divider rule, But for symmetrical networks, For properly terminated network, input impedance Rin is given by, From equation (2), From equation (2), we can write, Equations (A) and (B) are called design equations of symmetrical T attenuators. Symmetrical π Type Attenuator: Consider properly terminated symmetrical π network as shown in the Fig. 10.5.Let the characteristic impedance be pure resistive …
Attenuators in Network Analysis : In various transmission equipments, it is many times required to supress or reduce the levels of the currents and voltages at certain points. To fulfill the need of attenuation, a four terminal resistive network called attenuators is used. Attenuators in Network Analysis are designed to provide a known amount of attenuation between input and output terminals without changing the matching of the impedance at a given value. Attenuators are resistive networks, so all frequencies are attenuated by same degree of amount preventing attenuation distortion. As all the components are resistive in the attenuators networks, no phase shift will be introduced by such networks. Hence the phase constant (β) will be zero and the propagation constant (γ) will be equal to only the attenuation constant (α). Attenuators in Network Analysis are either symmetrical or asymmetrical networks. Attenuators are either of fixed value or adjustable value type. Generally fixed attenuator providing constant attenuation are called pads. The variable attenuators are generally used in radio broadcasting stations as volume controls. Attenuation …