3.5-GHz-Band Low-Bias-Current Operation 0/20-dB Step Linearized Attenuators Using GaAs-HBT Compatible, AC-Coupled, Stack Type Base-Collector Diode Switch Topology

Kazuya YAMAMOTO  Miyo MIYASHITA  Nobuyuki OGAWA  Takeshi MIURA  Teruyuki SHIMURA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.7   pp.1515-1523
Publication Date: 2007/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.7.1515
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
Keyword: 
wireless LAN,  attenuator,  diodes,  heterojunction bipolar transistors (HBTs),  linearity,  intermodulation distortion,  linearization,  monolithic microwave integrated circuit (MMIC),  

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Summary: 
This paper describes two different types of GaAs-HBT compatible, base-collector diode 0/20-dB step attenuators--diode-linearizer type and harmonics-trap type--for 3.5-GHz-band wireless applications. The two attenuators use an AC-coupled, stacked type diode switch topology featuring high power handling capability with low bias current operation. Compared to a conventional diode switch topology, this topology can improve the capability of more than 6 dB with the same bias current. In addition, successful incorporation of a shunt diode linearizer and second- and third-harmonic traps into the attenuators gives the IM3 distortion improvement of more than 7 dB in the high power ranging from 16 dBm to 18 dBm even in the 20-dB attenuation mode when IM3 distortion levels are basically easy to degrade. Measurement results show that both the attenuators are capable of delivering power handling capability (P0.2 dB) of more than 18 dBm with IM3 levels of less than -35 dBc at an 18-dBm input power while drawing low bias currents of 3.8 mA and 6.8 mA in the thru and attenuation modes from 0/5-V complementary supplies. Measured insertion losses of the linearizer-type and harmonics-trap type attenuators in the thru mode are as low as 1.4 dB and 2.5 dB, respectively.