Kenneth A Clayton

Author:

Kenneth C. Clayton

ISBN #:

0884103005

US Patent:

58059881, Sep 8, 1998

Filed:

Dec 22, 1995

Appl. No.:

8/577889

Inventors:

Kenneth Wilson Clayton - Plano TX
Robert Rudolf Rotzoll - Allen TX

Assignee:

Microtune, Inc. - Plano TX

International Classification:

H04B 126

US Classification:

455333

Abstract:

The system and method for switching a radio frequency (RF) signal between mixers can provide a large automatic gain control (AGC) range while maintaining low noise levels by using a switching circuit to select between at least two mixers that are switched between a common load using reverse biasing. To turn off a specific mixer, RF inputs to that mixer are reverse biased, which shuts off the current to the load. The full AGC of the switching circuit is approximately the sum of the AGC of each mixer. Each mixer has a limited AGC range, which limits the amount of current swing needed for the full AGC of the switching circuit. By dividing the switching circuit between two or more mixers, the transistor devices in each mixer may be sized appropriately with respect to the current levels being used in each mixer. For instance, in a mixer designed specifically for low noise applications, the transistor devices can be very large. For a mixer that is designed to tolerate more noise, the transistor devices may be smaller, which allows more precise tailoring of the ft of the particular mixer.