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In this paper, a uniplanar dual-band dipole antenna merged with an asymmetrical broadside-coupled balun that offers wideband impedance matching is presented. The balun has compact size and simple layout profile; on the other hand, its shape can be arbitrarily changed as long as the determined centerline length is maintained. By properly increasing the spacing between the long-arm and short-arm dipoles, the effect of the mutual coupling is improved such that dual-band frequency characteristics can be controlled and optimized, respectively. To validate the transition capability of the proposed balun, the balun has been employed to feed the dual-band antenna. Measurements show that the peak gains in the lower and upper bands are 3 dBi@ 2 GHz and 4 dBi@ 3.5 GHz, respectively, and the radiation patterns are almost omnidirectional at H-plane.

A low-noise amplifier (LNA) employing novel self-biased shunt-feedback mechanism for X band applications is presented. The shunt-shunt feedback impedance is not only used to eliminate the use of gate-biased voltage, but also neutralize the miller capacitor of the input transistor. With combining current-reused technique into the amplifier, it is benefit to boost power gain and maintain low power consumption. A source-degeneration inductor is also introduced at the input transistor to ensure good input matching and stability across the required bandwidth. A prototype was fabricated in 0.18-µm CMOS process to demonstrate the proposed LNA architecture. The measurements show that a maximum power gain of 10 dB, a minimum noise figure (NF) of 4.5 dB, −6 dBm input-referred third-order intercept point (IIP 3 ), and drawing 7.6 mA from a 1.8-V supply.