In this article, a multiband antenna for various wireless communications is proposed for WWAN, Bluetooth, WiMAX, WLAN, and Downlink satellite system. The antenna consists of a radiating patch and a rectangular ground plane with four L-shaped stubs which are embedded as side arms to obtain a resonating band for WWAN (1.9GHz), Bluetooth (2.4 GHz), WiMAX (2.5, 3.5, and 5.5 GHz), and WLAN (5.5 GHz) wireless systems and a C-shaped stub is etched on the radiating patch to obtain a higher WLAN band (2.4, 5.2, and 5.8 GHz) and a satellite downlink system (7.5 GHz). The proposed antenna exhibits circular polarization at WWAN band and linear polarization for remaining applications. Also, the proposed antenna exhibits an omnidirectional radiation pattern.

In this paper, a three layered stacked circularly polarized rectangular dual band microstrip antenna with a defected ground structure (DGS) and a feed network with stub (showing dual wideband characteristic) is designed, fabricated, and tested for WLAN, Zig bee, Wi-Max, and IMT band applications. The proposed antenna is fabricated on an FR4 substrate with dielectric constant (εr) of 4.4; tanδ of 0.0024 and a height of 1.57 mm.The antenna has a surface area of 4.8 × 4.1 cm2 and a total height of 5.1 mm. The designed antenna covers two wireless bands from 2.39 to 2.64GHz and 3.39–3.76 GHZ with impedance bandwidths (VSWR < 2) of 250 MHz (9% bandwidth centered at 2.515 GHz) and 370 MHz (10% bandwidth centered at 3.57 GHz), respectively. This antenna is capable of covering IEEE 802.11b/g/n standards of WLAN from 2.4 to 2.485 GHz, bluetooth applications from 2.4 to 2.483 GHz, ZigBee applications from 2.4 to 2.485 GHz, IEEE 802.16/ Wi-MaX applications from 3.4 to 3.69 GHz and international mobile telecommunications (IMT) band from 3.4 to 3.6 GHz. As the antenna is circularly polarized, the misalignment of the receiver with transmitter does not affect the performance of the system. The antenna designing was done using CST MWS V'10 and the prototype of the designed antenna was tested for the validation of S11 (dB) and gain results against the simulated ones experimentally. The proposed antenna shows a gain of 4.08 dBi at 2.5 GHz and a gain of 5.024 dBi at 3.51 GHz.

A 2.4 GHz CMOS blocker filtering low-noise amplifier (BF-LNA) suitable for Bluetooth™ application is presented. The circuit employs a differential amplifier topology with a current mirror active load and a notch filter. Each path amplifies differentially with the common mode input signal, but there is a notch filter rejecting only the wanted signal at one path. By subtracting the two signals from each path, the large interferers are rejected and only the wanted signal is amplified. Therefore, it becomes a narrow-band amplifier with blocker filtering capability, realizing a receiver system without need of the off-chip SAW filter. The BF-LNA is designed using a 0.13-μm CMOS process. The measured performances are a gain of 11.4 dB, and a noise figure of 1.85 dB. Attenuation levels at 400 MHz apart from the target frequency are −13 and −29 dBc at each sideband. The P1dB,in and IIP3 are −8.2 and 1.46 dBm, respectively. The proposed BF-LNA can reject large interferers at the front-end of the receiver system with a good noise figure.