A Band-Notched Antenna With Two Radiation Zeros Using Grounded Coplanar Waveguide Filter for 2.4/5 GHz WLAN Applications

In this article, a band-notched dual-polarized crossed dipole antenna is proposed for 2.4/5 GHz WLAN applications. The proposed antenna works on the WLAN 2.4-GHz (2.4–2.48 GHz) and 5-GHz (5.15–5.85 GHz) bands for a VSWR <2 with two radiation zeros within 3.4–3.6 GHz. First, an ultra-wideband crossed dipole antenna with an operating frequency of 2.4–5.8 GHz is designed using the grounded coplanar waveguide (GCPW) feeding structure. Second, a miniaturized defected microstrip structure (DMS) is embedded in the GCPW feeding strip to form a stopband behavior with a radiation zero. Finally, combining with the design of a C-shaped split ring resonator (SRR) on the arms of the dipole antenna, a band notch (3.4–3.6 GHz) with two radiation zeros can be realized. These two radiation zeros can be adjusted independently to achieve a wide stopband performance. As a result, compared with the original ultra-wideband dipole antenna, the realized gains of the proposed antenna in the 3.4–3.6 GHz range are all suppressed from 8 dBi to less than −8 dBi. The proposed antenna can realize the stable unidirectional radiation pattern and a high gain of around 7 dBi in the lower band and 8.5 dBi in the higher band of WLAN. As a demonstration, the proposed antenna is fabricated and measured, and the measurement results are in good agreement with the simulation results.

Design of a compact reconfigurable bandpass filter using interdigital capacitor, DMS slots and varactor diode for wireless RF systems

This paper proposes a new design of a reconfigurable bandpass filter based on an interdigital capacitor and varactor diode for wireless and mobile applications. The designed reconfigurable bandpass filter has been implemented on an RT 6010 substrate with a relative dielectric constant of 10.2, thickness of 1.27 mm, and loss tangent of 0.0023. In order to reduce the filter size, the defected microstrip structure (DMS) is used due to its easy design, high compactness, high quality factor and easy integration with other RF devices. The suggested reconfigurable filter has a simple structure with a very attractive compact size of 4.7 × 8.4 mm2, low insertion loss than -1 dB, and tuning range (2–2.6 GHz).

Dual-band bandpass filter based on two U-shaped defected microstrip structure

This paper presents design of dual-band bandpass filter by integrating conventional quarter-wavelength short circuit stubs bandpass filter with U-shaped defected microstrip structure notch filter. Based on the parametric analysis, it is found that high attenuation level can be achieved by using two U-shaped defected microstrip structure separated by specific distance. The designed circuit simulated using advanced design system and fabricated based on Roger 4350B. The simulation results are in good agreement with measured results. The designed filter covered two pass bands centered at 2.51 GHz and 3.59 GHz with 3-dB fractional bandwidth of 15.94% and 15.86%, respectively, return losses better than 15 dB, and insertion losses better than 1 dB. The designed device can be used for wireless communication applications such as WLAN and WiMAX.

Effect of the defected microstrip structure shapes on the performance of dual-band bandpass filter for wireless communications

Due to the progression growth of multiservice wireless communication systems in a single device, multiband bandpass filter has attract a great attention to the end user. Therefore, multiband bandpass filter is a crucial component in the multiband transceivers systems which can support multiple services in one device. This paper presents a design of dual-band bandpass filter at 2.4 GHz and 3.5 GHz for WLAN and WiMAX applications. Firstly, the wideband bandpass filter is designed at a center frequency of 3 GHz based on quarter-wavelength short circuited stub. Three types of defected microstrip structure (DMS) are implemented to produce a wide notch band, which are T-inversed shape, C-shape, and U- Shape. Based on the performance comparisons, U-shaped DMS is selected to be integrated with the bandpass filter. The designed filter achieved two passbands centered at 2.51 GHz and 3.59 GHz with 3 dB bandwidth of 15.94 % and 15.86 %. The proposed design is very useful for wireless communication systems and its applications such as WLAN and WiMAX

L-Shaped Slot-Loaded Stepped-Impedance Microstrip Structure UWB Antenna

A stepped planar microstrip structure is proposed and demonstrated as a candidate of the ultra-wideband (UWB) antenna in the paper. In the structure, two L-shaped slots are introduced into the rectangular microstrip patch to broaden the current path at both edges of the radiating patch. The impedance bandwidth of the antenna can be extended by using the stepped impedance resonator (SIR) structure at one end of the radiation patch and connecting with the feed line. The symmetrical two I-shaped slots are loaded on the SIR microstrip to improve in-band performance and further widen the operating band. The proposed new structure can have an improvement in the in-band characteristics while extending the operating bandwidth. A broadband impedance bandwidth of 2.39 GHz to 13.78 GHz at S11 < −10 dB is demonstrated based on the proposed novel structure. The reflection coefficient and radiation characteristics are characterized in the paper. The tiny antenna, with the benefit of small area 36 mm × 23 mm, shows potential applications in ultra-wideband communication systems, wireless energy harvesting systems, and other wireless systems.

Determination of Transmission Coefficients and Energy Density of an Overlay Microstrip Patch Antenna for Microwave Filters and Feeds Designs Using Microwave Methods

In designing filters and antenna feeds at microwave frequency, the energy density and stop bands are of vital importance. To this development, this work is set out to determine the transmission coefficients behavior of substrates along with their energy density for a microstrip structure using finite element method (FEM) and Vector network analyzer (VNA). In this work, a 15, 30 and 50 mm PTFE samples were used as an overlay substrate material on a patch microstrip antenna. Simulations and measurement were then carried using FEM and VNA, respectively. Transmission coefficient obtained via FEM and VNA were compared and the behavior of the substrates at 10 GHz were noted which is the area of broad stop band. Results from simulation and measurement showed that the energy density of the 50 mm thick substrates was 1.67 x 10-5 J/m3 while the attenuated power for the 15, 30 and 50 mm thick substrates at 10 GHz were 6.8, 8.0 and 14.6 dB, respectively. Based on these findings, it is concluded that the 50 mm thick PTFE substrates has the deepest stopband at 10 GHz and more suitable for filter designs and antenna feeds.