A wideband monopole antenna with dual band‐stop function for WLAN (2.4 GHz/5 GHz) is presented. By cutting away an arched slot from the radiation patch and inserting spur‐lines into the ground, dual band‐stop functions for 2.4 GHz and 5 GHz WLAN bands are obtained. The proposed antenna operates over 1.9–11 GHz for VSWR <2, while providing a band‐stop function in the frequency bands of 2.2–2.5 GHz and 5.15–6.1 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1646–1649, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23570

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impedance over the operation bands can be achieved. This length controls the additional capacitive reactance between the section C-D and the shorter radiating arm, which can also compensate for inductive coupling contributed to the shorting portion.ABSTRACT: In this study, a tunable bandpass filter with a hairpin line resonator and loading capacitors using varactor diodes was proposed. The filter was modified by adding varactor diodes to the coupling part to compensate for losses. The designed filter had a simple structure and the characteristics of wide tuning range of 87.9% from 430 to 1105 MHz and low insertion loss of less than 4.42 dB.ABSTRACT: This article presents the design and the measurement results of a 3-to 5-GHz down-converter fabricated in a 90-nm CMOS technology. The circuit consists of a single-ended low-noise amplifier and two I/Q double-balanced mixers. A transformer-based on-chip single-ended-to-differential conversion allows gain and noise performance to be optimized at a very low power. The down-converter achieves a 23-dB conversion gain, a noise figure of 3.4 dB, and an input thirdorder intercept point of Ϫ8 dBm, while drawing only 9 mA from a 1.2-V supply voltage. The down-converter exhibits competitive performance compared to the best state-of-the-art ultra-wideband circuits in the same frequency range.

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