Transmission Line Resistance Compression Networks and Applications to Wireless Power Transfer

Microwave-to-dc rectification is valuable in many applications, including RF energy recovery, dc-dc conversion, and wireless power transfer. In such applications, it is desired for the microwave rectifier system to provide a constant RF input impedance. Consequently, variation in rectifier input impedance over varying incident power levels can hurt system performance. To address this challenge, we introduce multiway transmission line resistance compression networks (TLRCNs) for maintaining near-constant input impedance in RF-to-dc rectifier systems. A development of TLRCNs is presented, along with their application to RF-to-dc conversion and wireless power transfer. We derive analytical expressions for the behavior of TLRCNs, and describe two design methodologies applicable to both single and multistage implementations. A 2.45-GHz four-way TLRCN network is implemented and applied to create a 4-W resistance compressed rectifier system that has narrow-range resistive input characteristics over a 10-dB power range. It is demonstrated to improve the impedance match to mostly resistive but variable input impedance class-E rectifiers over a 10-dB power range. The resulting TLRCN plus rectifier system has >50% RF-to-dc conversion efficiency over a >10-dB input power range at 2.45 GHz (peak efficiency 70%), and standing wave ratio <;1.1 over a 7.7-dB range, despite a nonnegligible reactive component in the rectifier loads

Pleural effusion in sarcoidosis: a report of six cases.

Six (4 percent) of 150 patients with sarcoidosis had a pleural effusion. A review of the literature revealed seven more patients with pleural sarcoidosis. Analysis of the 13 patients reported so far did not reveal any clinical, radiological, or laboratory feature which may be of diagnostic significance. The diagnosis of pleural sarcoidosis was based on clinical or radiographic grounds and histological evidence of noncaseating granulomata. In three of the patients pleural fluid resolved spontaneously; the other three were treated with corticosteroids. It is suggested that pleural involvement in sarcoidosis, especially in Negroes, may be more frequent than is generally realized and the effusion may occur either at the time of initial presentation or later in the course of the disease