Theory and design of an adjustable equalizer

An adjustable equalizer was developed to compensate for the changes of attenuation in carrier transmission lines. It is built of bridged-T circuits and all-pass filters forming a ladder structure the input of which is connected to a series or parallel branch of a voltage divider, and the output-to an adjustable resistor the value of which determines the attenuation. All-pass filters are used as correcting components in order to approximate more closely the specified attenuation characteristics. Expressions for the attenuation and phase are derived, and a graphic method is described for determination of the phase when the attenuation is prescribed. An example of the complete circuit is shown.