Shunted-line stepped-impedance resonator

As the demand for wireless products increases, low cost and high integration have become the major issues in RF circuit design. It is critical for RF system designers to offer multistandard operation while at the same maintaining competitive hardware costs. For example, global system for mobile communications (GSM) and wideband code division multiple access (WCDMA) mobile communications standards operate in frequency bands of 900, 1,800, and 1,900 MHz. The difference between these two is that GSM is a 2G technology and WCDMA is a part of the newer 3G group of technologies. Wireless local area network (WLAN) products using IEEE 802.11b [27] and IEEE 802.11g [29] standards operate in the unlicensed industrialscientific- medical (ISM) 2.4-GHz band, and products using IEEE 802.11a [28] and 802.11n [30] operate in the ISM 5-GHz band. Previously, the dual-band RF front end was realized with two single-band filters and a duplexer. S uch an approach requires a large circuit size. As a result, dual-band filters have recently be - come attractive components for use in wireless communication devices operating at RF and microwave frequencies [1][20].