Circulator, Radio Frequency, NSN 5985-010566104

Microwave Applications Group (MAG) is pleased to offer this proposal in an effort to address obsolescence issues and become a qualified source of supply for NSN 5985-01-056-6104; Part Number 4HA-8471-B or 910916-1; Circulator, Radio Frequency; as used on the AN/FPS-115 PAVE PAWS Radar System. The PAVE PAWS is a critical system in providing missile warning and space surveillance for protection of the United States and allied nations. Documentation for the subject Circulator lists Western Microwave Labs as the suggested source of supply. Western Microwave was bought by Signal Technology Corporation (STCO) sometime in the 1990s. It is unknown if any other companies are capable or willing to support this program by supplying the subject Circulator, but the fact that the device is listed by DLA as a subject to address obsolescence and source of supply issues leads MAG to believe that a source is currently unavailable. In the corporate world today, many original manufacturers of defense program devices have either been merged into other organizations, are no longer in business, or are unwilling to support programs with smaller delivery requirements.  From reviewing the schematic displayed on Sheet 11 of the provided legacy documentation, it is apparent that the Circulator is constructed from a pair of 3-port Y-junction circulators.  The basic operating principles of ferrite Y-junction circulators is summarized in this section to present a simplified non-mathematical description highlighting Y-junction circulator operating characteristics. Note that the example given is for a rectangular waveguide device, while the subject Circulator is a coaxial device. The realizations of both types of Y-junction devices are basically the same, with the differences occurring in the RF interfaces to the rest of the system.  A junction circulator is a 3-port device formed by a symmetrical Y-shaped waveguide transmission line arrangement coupled to a magnetically biased ferrite core — the actual circulation occurring at the intersection of the three transmission lines and the ferrite core. A simple model illustrating the junction circulator operation is presented in the technical volume along with a brief discussion of circulation and ferromagnetic resonance concepts which will give a better understanding of the circulation region.