Low phase shift, high frequency attenuator

摘要

A wideband RF attenuator circuit that has a reduced impact on the phase of an applied signal when switched between an attenuation state and a non-attenuating reference or bypass state. A low phase shift attenuation at high RF frequencies can be achieved by utilizing a switched signal path attenuator topology with multiple distributed transmission line elements per signal path to provide broadband operation, distribute parasitic influences, and improve isolation to achieve higher attenuation at higher frequencies while still maintaining low phase shift operational characteristics. In an alternative embodiment, extension to even higher frequencies can be achieved by utilizing a quarter-wave transmission line element at the signal interfaces of each signal path, thereby improving insertion loss and power handling.

主权项

1. A radio frequency attenuator circuit including:
(a) an In port and an Out port; (b) a bypass path including a plurality of serially-connected distributed transmission line elements, a plurality of shunt switches coupled between a respective one of the plurality of distributed transmission line elements and a reference voltage, and first and second state switches respectively coupled between the plurality of distributed transmission line elements and the In and Out ports; and (c) at least one attenuation path, each such attenuation path including a plurality of serially-connected distributed transmission line elements, a plurality of shunt switches coupled between a respective one of the plurality of distributed transmission line elements and a reference voltage, at least one attenuator element serially connected to the plurality of distributed transmission line elements, and first and second state switches respectively coupled between the plurality of distributed transmission line elements and the In and Out ports.