In this paper, a new wire inverted-F antenna (IFA) is proposed, which is structured by grids of thin wires. This novel wire grid IFA is ~0.3λ long and ~0.14λ high and renders 41% fractional bandwidth which is nearly 5 times higher than the bandwidth of a classic IFA. In addition to the novel structure and high bandwidth, the distinguishing feature of the design process employed is its computational efficiency. While the constituent wires of the wire grid (WG) model are one-dimensional (1D) thin wires, they can indirectly form very thick arms leading to bandwidth enhancement. The thin-wire structure of the WG-IFA provides the opportunity to carry out the analysis and design accurately and fast in a 1D MoM-based software like NEC.
This paper describes the concept, design, and measurement of a multi-band circularly polarized printed slot antenna with a single microstrip feed line. The antenna design for circular polarization (CP) at 1.5 GHz for GPS, 2.4 GHz for Bluetooth, and 3.75 GHz for WiMAX application is given. The proposed antenna also provides a fourth linear polarized band over 5.2 to 6 GHz covering the WLAN band. The design is such that all three CP bands can be tuned for any other desired frequencies. Three configurations of the proposed antenna with different design parameters for different circularly polarized bands are reported in the paper. A prototype of the proposed antenna is fabricated, and measured results are compared with those of the simulations.
In this paper two novel coplanar waveguide (CPW) fed printed ultra wide band (UWB) monopole antennas with dual band-notching characteristics are proposed. The modified ground technique with symmetric ground plane in antenna-1 and asymmetric ground planes in antenna-2 is exploited to cover UWB application. Both antennas are compact with dimensions of 30 x 30 x 1.6 mm3 and have dual band-notched characteristics with first notched band for integrated band of WiMax 3.5/5.5 GHz and C-band satellite communications 3.7-4.2 GHz, and second notched band for WLAN 5.2/5.8 GHz bands. Antenna with symmetric ground plane achieves the impedance bandwidth of 2.9-11.5 GHz, and antenna with asymmetric ground plane achieves the impedance bandwidth of 2.9-11.89 GHz, respectively with VSWR < 2 except in the notched bands. The antennas are designed and optimised in CST Microwave Studio. The simulated VSWR of the proposed antenna designs is compared with the measured VSWR of fabricated antennas, and it is found that they are in a good agreement. Both antennas exhibit monopole-like radiation patterns with significant gain in entire operating band. Maximum gain of the proposed antenna with symmetric ground plane is 5.3 dBi at 8 GHz, and that with asymmetric ground plane is 4.5 dBi at 7 GHz.
Electromagnetic (EM) wave absorption characteristics for a Bonsai tree are investigated at GSM-900 band. Finite Difference in Time Domain (FDTD) method is hybridized with Friis transmission equation to carry out all the required EM simulations. The tree has been modelled using CT scan based 3D dataset considering different electrical parameters. Maximum local electric (E) field, magnetic (H) field, Specific Absorption Rate (SAR) and Shielding Effectiveness (SE) have been calculated for the tree placing at distance of 5 m away from a radiating Base Station Antenna (BSA) with 20 W input power. The maximum local E field, H field, 1-g SAR and SE obtained by the simulation are found to be 70.1 V/m, 0.09 A/m, 0.135 W/kg and 13.18 dB, respectively. Plants are found to be good natural electromagnetic radiation shield.
In this paper, an ultrathin asymmetric chiral metamaterial multi-band circular polarizer using combined twisted double-gap split-ring resonators (DGSRRs) is proposed and investigated. Experiment and numerical simulations are in good agreement, indicating that when a y-polarized wave is incident on this chiral metamaterial propagating along -z direction, the right circularly polarized (RCP) wave is emitted at 5.58 GHz and 9.34 GHz, while left circularly polarized (LCP) wave is excited at 6.41 GHz and 7.65 GHz, in addition to large polarization extinction ratio of more than 18 dB at the four resonant frequencies. The surface current distributions are studied to illustrate the transformation behavior for both circular polarizations.
A novel compact UWB antenna with 3.5/5.5 GHz dual notch-band characteristics is presented. The proposed antenna has a simple structure and compact size of 30×35mm2. Firstly, a compact modified rotated monopole antenna that covers UWB band is achieved. Then by inserting a λ/4 stub and etching two symmetrical λ/4 L-shape slots on the UWB antenna achieved before, a dual band-notched ultra-wideband antenna is obtained. The prototypes of UWB antenna with and without notched bands were fabricated and measured. Good performance of dual notched bands, stable gain and omnidirectional radiation patterns make the proposed antenna promising for UWB application.
The paper presents a compact planar Ultra Wide Band filter employing folded stepped impedance resonators with series capacitors and Dumb bell shaped Defected Ground Structures. An interdigital quarter wavelength coupled line is used for achieving the band pass characteristics. The transmission zeros are produced by Stepped Impedance Resonators. The filter has steep roll off rate and good attenuation in its lower and upper stop bands, contributed by the series capacitor and DGS respectively.
A single-layer wideband printed antenna for dual-polarized applications is proposed in this paper. Two orthogonal linear polarizations are achieved by adopting a hybrid feeding technique. The horizontal polarization is excited by an aperture-coupled microstrip feed line while the coplanar waveguide (CPW) feed line is responsible for the vertical polarization. Measurements demonstrate a fairly wide common impedance bandwidth of 56.3% (1.61-2.87 GHz) with SWR ≤ 2 could be achieved. By loading a rectangular patch in the narrow rectangular slot, the isolation between two ports can be improved to better than 40dB over the entire bandwidth. Moreover, the average gains of the proposed antenna are about 5.8 dBi and 5 dBi for port 1 and port 2, respectively.
A new family of metamaterial-inspired monopole antennas designed for GPS operation is reported. By adding a simple Split-Ring Resonator (SRR) into the near-field region of a monopole antenna resonating at 2.45 GHz, we have created a second resonance situated in the L1-band (f=1,537 for example) lower than the monopole's one. At this new resonance, the directivity of the structure was enhanced and its profile was reduced. Four SRR-configurations were considered depending on the orientation of the slot into the resonator. The structure was first optimized by adjusting the resonator size and the coupling distance between it and the monopole. Next, the directivity of the structure was improved by adjusting both the SRR-slot position and the coupling distance. Finally, the optimized structure in terms of size and directivity was realized and characterized.
A compact dual-band MIMO antenna with high port isolation for WLAN applications is proposed. The proposed antenna is basically composed of two monopoles and designed at 2.4/5.2 GHz. High port isolation is achieved by introducing a T-shaped junction on the top surface of the substrate and etching two slots on the ground. The measured bandwidth of the proposed antenna are 2.34-2.55 GHz and 5.13-5.85 GHz, which are suitable for WLAN applications, and the measured isolation between the two monopoles is higher than 20 dB in both bands. Meanwhile, the envelope correlation coefficient of the antenna at both operating bands is lower than 0.001, which means that the antenna has high diversity gain. Good agreement is achieved between the predicted result and the measured data. The overall size of the proposed antenna is 38 mm×43 mm×1.6 mm.
Research centers and industries often need to measure the microwave electromagnetic emission of hot bodies, in order to calculate their temperature. It is well known that the most critical part of a microwave radiometer is its receiver, to obtain a very sensitive system that can also measure low emissions this needs, among other features, to be very sensitive, necessitating the use of expensive low noise amplifiers. For some time now, low-cost components for the reception of satellite TV have been available on the consumer market. These are known as Low Noise Block (LNB), and they include, as a front-end, an amplifier with very low intrinsic noise. In this study, we wanted to test the feasibility of designing and using a 12 GHz total power radiometer, using, as a front-end, an LNB. The system was tested, in different configurations, to measure the emission due to natural sources (Earth, Sun and a sunny wall).
A new compact CPW-fed slot antenna for UWB applications is presented in this paper. The slot in the ground plane is asymmetric which helps in wide band impedance matching. The radiating element is a star-shaped geometry fed by a double stepped co-planar waveguide. Three antennas are designed with this geometry. Out of these three antennas, a compact antenna is proposed. The size of the proposed antenna is 27.2 x 32.2 mm2, and it has a measured impedance bandwidth of 8.7 GHz (3-11.7 GHz). The radiation patterns are stable with respect to frequency and of bi-directional shape in E-plane and omnidirectional shape in H-plane. The measured and simulated results are in good agreement.
Circularly polarized millimeter-wave travelling-wave antennas, using substrate integrated circuits (SICs) technology, are designed, fabricated and tested. By using the SICs technology, compact antennas with low losses in the feeding structure and with good design accuracy are obtained. The elementary antenna which is composed of two inclined slots is characterized by full-wave simulations. This characterization is used for the design and development of linear antenna arrays with above 16 dB gain and low side lobe level (<-25 dB), using di®erent power aperture distributions, namely uniform, Tchebychev and Taylor. Experimental results are presented at 77 GHz showing that the proposed antennas present good performances in terms of impedance matching, gain and axial ratio. These antennas have potential applications in integrated transceivers for communication and radar systems at millimeter-wave frequencies.
A new ultra-wideband antenna with enhanced, nearly constant gain is presented. This quasi-planar antenna is composed of a CPW-fed printed monopole and a short horn, both made out of a single substrate. The measurements demonstrate an almost at peak gain of 5.5 dBi0.7 dB from 2.5 GHz to 15 GHz with the average gain difference in XZ plane is roughly 2 dB up to 8 GHz, which further rise to 6 dB at 10 GHz. The antenna also has a nearly linear phase response in this band. Well tested performance both in frequency and time domains, along with broad azimuth pattern, results in minimal ringing of a radiated pulse. The new antenna is suitable for establishing good line of sight link for UWB transmission and other broadband applications.
This paper presents a frequency and pattern reconfigurable stacked patch microstrip array antenna fed by aperture-coupled technique. The antenna consists of three substrate layers with radiating elements sorted at substrate layer 1 (top patches) and substrate layer 2 (bottom patches). The layers have different sizes to indicate different operating frequencies. On the ground plane, the four sets of two different aperture slot shapes (I-shaped and H-shaped) are used to transfer the wave and signal to particular radiating elements during the PIN diode switches configurations. The I-shaped slots are used to activate the bottom patches while the H-shaped slots are used to activate the top patches. Four PIN diode switches are placed at the feed line, positioned between the I- and H-shaped slots. Next, by changing the PIN diode switches configuration to ten cases, the proposed antenna has capabilities to change the operating frequencies and the pattern characteristics itself. The measured results of return loss, gain and radiation patterns are slightly shift compared to the simulated results.
A novel CPW-fed antenna capable of triple-band operation for WLAN/WiMAX applications is presented and investigated in this paper. The proposed antenna simply consists of three elements viz. folded open stub, L-shaped open stub, and Y-shaped resonator. By using the three elements, triple-band antenna operating at 2.5/3.5/5.5 GHz can be achieved. The antenna impedance bandwidths for |S11| ≤ -10 dB are 2.39-2.69, 3.38-3.73 and 5.0-5.99 GHz, covering all the WLAN/WiMAX operation bands. The tri-band antenna has good omnidirectional radiation patterns in H-plane and moderate gains across all the operation bands with compact size of 30 × 18 mm2. Experimental results show that the antenna is successfully simulated and measured, and the tri-band antenna can be achieved by adjusting the lengths of the three elements and gives good gains across all the operation bands.
A novel ultra-wideband four-way in-phase multilayer power divider based on the microstrip-to-slotline transition is proposed in this paper as a complemental slotline power divider with high isolation. Due to the introduction of three lumped isolation resistors, the isolations between output ports in the new structure have been improved. The design expressions have been derived by making use of odd-mode and even-mode method. Both simulated and measured results have proved that the proposed power divider has good impedance matching at all ports, high isolations between output ports, excellent amplitude and phase balance, as well as flat group delay over the wide frequency range from 3.8 GHz to 11 GHz.
A small patch antenna is associated with passive (reactively loaded) elements (varactors) in order to auto adjust the resonant frequency in a single-channel multi-frequency configuration appropriate for biomedical applications. As a supplementary study of the authors in the field of detection of temperature abnormalities in human tissue phantom using microwave radiometry, this paper adds a contribution to frequency readjustment when a shift occur due to the fact that the human body is a complex and stratified dielectric object. The optimization of the array is performed using a Genetic Algorithm (GA) tool as a method of choice. The adjustment in the measurement frequency is performed by altering the values of the passive elements according to the shift needed.
A dual-band circularly polarized antenna is presented in this paper. A rectangular patch antenna with gap-feeding structure is firstly designed, and 3-dB axial-ratio bandwidth from 2.35 to 2.48 GHz is obtained. A parasitic square ring is placed on the rear of the rectangular patch as a band-notch unit operating around 2.4 GHz. Then an original wide circularly polarized band is split into two bands from 2.25 to 2.31 GHz and from 2.46 to 2.53 GHz. By adopting differential feeding, symmetrical patterns are achieved. Measurement results show that two 3-dB axial-ratio bands of 2.6% (2.25-2.31 GHz) and 2.0% (2.51-2.56 GHz) are obtained with a small frequency ratio of 1.11.
In this paper, a novel microstrip-fed compact antenna with triple band-notched characteristics is presented for ultrawideband (UWB) applications. The antenna consists of a circular radiating patch, a 50 Ω microstrip feed line, a partially slotted ground plane, and a pair of modified capacitance loaded loop (MCLL) resonators. The novel resonators are symmetrically located in the vicinity of the feed line to achieve triple band-notched characteristics, such as 3.4-3.7 GHz for WiMAX, 5.15-5.825 GHz for WLAN, 7.25-8.395 GHz for X-band satellite communication. The good performance of triple notched bands, stable gain and omnidirectional radiation patterns in the operating bands make the proposed antenna a good candidate for UWB utilization.