N093-220 TITLE: Ultra Low PIM Diplexer

TECHNOLOGY AREAS: Electronics, Space Platforms

ACQUISITION PROGRAM: Mobile User Objective System (MUOS), an ACAT I program.

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Improve the passive inter-modulation (PIM) performance of diplexers for future communications satellites.

DESCRIPTION: Intermodulation or intermodulation distortion is the result of two or more signals being mixed together to form additional frequencies that are not desired. Intermodulation occurs in non-linear systems, which generally have active components that require a power source in addition to the input signal. Passive intermodulation (PIM) can occur in components with junctions of dissimilar metals or metals and oxides. The junctions effectively form diodes, which are non-linear. This leads to intermodulation in systems designs where there should theoretically be none.

Since the use of nonlinear materials is usually prohibited in the transmit signal path of a diplexer, typically the major source of nonlinearities is imperfect metal-to-metal contacts associated with the assembly of the diplexer from multiple metal parts. These imperfect contacts can occur due to workmanship issues such as flatness tolerance or insufficient contact pressure, and are also typically related to thermal issues such as expansion and contraction at these interfaces. Diagnosing and attempting to correct such microscopic workmanship problems is typically extremely difficult and time consuming, and can be futile given the usual schedule pressures.

Since PIM is a nonlinear phenomenon that depends on the transmit signal levels and the order of interest, one can''t define "ultra-low PIM" by specifying a single power level. Probably the simplest way to quantify "ultra-low PIM" is to provide an example, i.e., the Mobile User Objective System (MUOS) diplexer. The current 7th-order PIM specification (which assumes two simultaneous 400 W transmit signals) for the MUOS diplexer is -113 dBm. A beyond state-of-the-art improvement in diplexers will enable a significant increase in system capability. A level of -130 dBm or lower for this particular transmit signal level and PIM order could be considered very good PIM performance. It is believed that a level significantly below -130 dBm is achievable, and this could therefore be considered "ultra-low PIM" for this application.

Since the achievable PIM performance of a diplexer is typically limited by workmanship issues, a new manufacturing process, new materials, or a new design philosophy that minimizes the effects of workmanship issues, would be very beneficial.

PHASE I: Develop a new manufacturing process, new materials, or a new design philosophy that minimizes the effects of workmanship issues on the PIM performance of diplexers.

Tasks under this phase could include:
� Develop a new manufacturing process, new materials, or a new design philosophy
� Develop a model to show the expected PIM performance of the proposed solution
� Describe trade-offs to be explored in Phase 2

PHASE II: Develop a prototype diplexer and demonstrate its performance against expectations.
� Refine the design and develop a prototype(s) based on Phase I efforts.
� Evaluate measured performance characteristics versus expectations and make design adjustments as necessary.

PHASE III: This phase will focus on manufacturing the diplexers for MUOS or follow on satellite systems.

PRIVATE SECTOR COMMERCIAL POTENTIAL DUAL-USE APPLICATIONS: This technology can be applied to any system using diplexers, including satellite communications and terrestrial wireless communications.

REFERENCES:
1. "Passive intermodulation interference in communication systems", Lui, P.L., Electronics & Communication Engineering Journal, Volume 2, Issue 3, Jun 1990 Page(s):109 - 118

2. "Surface Treatment and Coating for the Reduction of Multipactor and Passive Intermodulation (PIM) Effects in RF Components," D. Wolk, J. Damaschke, C. Vicente, B. Mottet, H.L. Hartnagel, L. Galán, I. Montero, E. Roman, M. Alfonseca, J. de Lara, D. Raboso

3. "Systems Methodology for PIM Mitigation of Communications Satellites," 2003, Rabindra (Rob) Singh, Eric Hunsaker,

4. International workshop in Multipactor, Corona and Passive Intermodulation (MULCOPIM) 2008, http://www.cfp.upv.es/mulcopim08/cd_interior_mulcopim/inicio/index.html

KEYWORDS: MUOS; PIM; passive intermodulation; diplexer; SATCOM

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