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This paper presents the analysis, design, and performance characteristics of a new planar balun structure. The design is based on the log-periodic antenna theory. The design guidelines, as well as simulation and measured results, are presented. It is shown that the new balun has greater than one octave bandwidth. A comparison to the half-wave balun is also included. The log-periodic balun will find applications in wireless communication circuits or devices such as mixers, amplifiers, and antennas.

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-The design and analysis of a novel wideband, monolithic, bandpass, π π π π-network, voltage controlled attenuator (VCA) is presented. A 24 to 32 GHz VCA was developed using 0.15µ µ µ µm GaAs pHEMT technology. This is the first reported VCA to use a bandpass filter topology to achieve the required operating frequency band and eliminate the effects of parasitic capacitances of the pHEMTs. The bandpass filter absorbs the parasitic capacitances and thereby eliminates their detrimental effects.The measured attenuation dynamic range is 12dB ± ± ± ± 0.5dB with minimum insertion loss of 2-3dB. The input power handling capability is up to 0dBm. The VCA is well matched and may be placed in a 50Ω Ω Ω Ω system [1].

In this paper, a novel electronically tunable active duplexer suitable for reconfigurable wireless transceiver applications is presented. The theory, design, and measured results of a varactor tunable active duplexer are summarized. The prototype active duplexer presented in this paper provides an electronically adjustable isolation of 20-50 dB between isolated ports and a gain of approximately 5 dB between coupled ports in the tunable range from 1.62 to 1.82 GHz in both transmit and receive modes of operations. The measured noise figure of the duplexer varied from 1.77 to 2.44 dB in the tuning range. The measured output powers at the 1-dB gain compression point and third-order intercept point, varied from 8.5 to 9.5 dBm and 20 to 29.5 dBm, respectively, in the tuning range. The design guidelines, measured -parameters, and results of yield analysis of the duplexer are presented. The proposed duplexer can be implemented as a monolithic microwave integrated circuit.Index Terms-Active duplexer, duplexer, reconfigurable duplexer, tunable active duplexer.