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We examine a rectangular cavity resonator method to accurately characterize the complex permittivity of dielectric materials over a wide frequency range of 1–5 GHz by exploiting the fundamental mode and higher-order TE(1,0,l) modes. For this purpose, a rectangular waveguide is coupled with a cavity resonator through a large inductive aperture. The permittivity characterization at both even and odd TE(1,0,l) modes enables continuous determination of the permittivity over operating frequencies. The characterization of the permittivity for even TE(1,0,l) modes suffers from potential errors due to the displacement of materials. This paper also proposes a method to compensate for these errors and improve the accuracy in the even modes. The experimental results of the fabricated cavity are presented using different materials (frequency-independent and frequency-dependent). The measured complex permittivity results show a good agreement with the reported results over a wide bandwidth available in the literature.

A soft implantable drug delivery device integrated wirelessly with wearable devices was developed to treat fatal seizures., Personalized biomedical devices have enormous potential to solve clinical challenges in urgent medical situations. Despite this potential, a device for in situ treatment of fatal seizures using pharmaceutical methods has not been developed yet. Here, we present a novel treatment system for neurological medical emergencies, such as status epilepticus, a fatal epileptic condition that requires immediate treatment, using a soft implantable drug delivery device (SID). The SID is integrated wirelessly with wearable devices for monitoring electroencephalography signals and triggering subcutaneous drug release through wireless voltage induction. Because of the wireless integration, bulky rigid components such as sensors, batteries, and electronic circuits can be moved from the SID to wearables, and thus, the mechanical softness and miniaturization of the SID are achieved. The efficacy of the prompt treatment could be demonstrated with animal experiments in vivo, in which brain damages were reduced and survival rates were increased.

A theoretical model of a cylindrical ferrite resonator antenna with a dc magnetic bias, applied in the direction parallel to the antenna height, is proposed. ${\mathrm {HE}}_{\mathrm {11\delta }}$ mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. The proposed model is validated through an experimental investigation of the HE $_{{\mathrm {11\delta }}}$ mode antenna. This communication utilizes a Li-ferrite suitable for the antenna applications. The presented theory is shown to correlate well with the measured results. It is also found that HE $_{{\mathrm {11\delta }}}$ mode splitting behavior of the antenna involves frequency and polarization, and bandwidth tuning performances. Therefore, the antenna is a good candidate for a multifunctional antenna.

In this letter, a multiband full-metal-rimmed antenna covering 10 frequency bands for personal wireless communication terminals is presented. The design antenna is based on simple and effective techniques that are used for metal-rimmed smartphone applications. The proposed antenna with full metal rim is designed on RO4350B substrate within the volume of 130 × 70 × 5 mm3. We employed RO4350B substrate with inserted vias as metal rim with height of 5 mm, which surrounds the inner circuit board. The circuit board substrate has a ground plane, which is connected to the metal rim via extended substrate patch. This connection divides the rim into two metal rim strips. The combination of these two strips allows the design to operate on 10 bands. Performing perturbation on the ground plane further adds more operating bands and makes the design an excellent candidate for multiband operation. The designed antenna can be used to serve on GSM850/900, GPS, DCS, PCS, UMTS, WiBro at 2.35 GHz, Bluetooth, ISM, SDM-B at 2.65 GHz, WiMAX at 3.5 GHz, and C-band at 4 GHz wireless communication bands. A prototype antenna was fabricated and tested for input reflection coefficient, radiation performances, antenna gain, and efficiency. The measured and simulated results have been presented and discussed.

A compact quad-band microstrip antenna operating on frequency range from 2 to 6 GHz for wireless applications is proposed in this paper. A rectangular CSRR is placed at the patch whereas ground is loaded with one square and two circular CSRRs along with two rectangular slots around the microstrip feed.The physical dimension of the proposed antenna thus, optimized using HFSS software is found to be 37×37×1.6 mm3 which is compact in size. Proposed antenna is fabricated and measured. Four frequency bands having bandwidths of 475.1 MHz, 107.3 MHz, 207.6 MHz,and 159 MHz for respective resonant frequencies at 2.7 GHz, 3.8 GHz,5.4 GHz and 5.98 GHz are obtained. Simulated and measured results obtained using VNA for reflection coefficient and VSWR are in good agreement. Simulated peak gain is achieved to be 1.02 dB, 1.55 dB, 2.061 dB & 2.063 dB atcorresponding resonant frequencies. The simulated radiation patterns at resonant frequencies are drawn.

In this paper, a compact microstrip patch antenna with offset feeding technique is proposed for WLAN (2.4/5.2 GHz) and Wi-MAX (3.5 GHz) applications. The design includes defected ground structure (DGS) for bandwidth improvement. A single complimentary split ring resonator (CSRR) is introduced on the main patch. Along with a CSRR ring, the main radiator is also loaded with a rectangular slot. The proposed antenna is compact with a size of 24 × 24 × 1.6 mm3. The design is validated and optimized by using Ansofts’ HFSS 13.0, EM full wave software. Experimental and simulated results are compared, and a good agreement between them is observed.

A novel antenna with both horizontal and vertical polarizations is proposed for 1.7–2.1 GHz LTE band small cell base stations. Horizontal polarization is achieved by using the Vivaldi antennas at the main PCB board in azimuth plane, whereas the vertical polarization is obtained using the rectangular monopole with curved corners in proximity of the horizontal elements. A prototype antenna associated with 8-elements (four horizontal and four vertical) is fabricated on the FR4 substrate with the thickness of 0.2 cm and 0.12 cm for Vivaldi and monopole antennas, respectively. Experimental results have validated the design procedure of the antenna with a volume of 14 $\times $ 14 $\times $ 4.5 cm $^{3}$ and indicated the realization of the requirements for the small cell base station applications.

A compact coplanar waveguide (CPW)-fed F-shaped stub printed antenna is presented. The first and second resonance modes are excited due to F-shaped stub connected to modified CPW ground plane and third resonance mode due to modified L-shaped CPW feeding. The impedance bandwidths of 190 MHz (2.06–2.25 GHz) for UMTS band, 530 MHz (4.61–5.14 GHz) for 4.9 GHz public safety WLAN, 1490 MHz (5.45–6.94 GHz) for 5.5 GHz WiMAX, 5.8 GHz WLAN, and ITS (intelligent transport systems) bands application is achieved. The proposed antenna provides circular polarization (CP) in the 4.9 GHz public safety WLAN band with 3-dB axial ratio (AR) bandwidth of 170 MHz (4.88–5.05 GHz) and linear polarization in the other two bands. By employing a single switch between F-shaped arms and changing the state of switch, antenna exhibits narrowband and wideband functionality with dual- and triple-band behaviour while keeping antenna size 25 × 25 mm2.

This paper presents a wearable aperture coupled microstrip patch antenna for Industrial, Scientific and Medical (ISM band) applications. In the proposed work, wearable material such as jeans is used as the feed substrate and wash cotton is used as the antenna substrate. The antenna operates in the ISM frequency band of 2.40–2.48 GHz, with the impedance bandwidth of 80 MHz (|S11| < −10 dB). The parameteric study and the outcome of the proposed antenna are presented and discussed in detail.

This paper investigates the channel characterization of Rayleigh fading channel using K- band frequency-modulated continuous wave (FMCW) radar system. An IF (intermediate frequency) signal of K-band FMCW radar can be treated as time and frequency domain signals due to a unique property of linear frequency modulation (LFM). First, channel sounder FMCW radar stability has been confirmed by measuring power flatness of transmitted radio frequency signal and estimated range in anechoic chamber before conducting the experiment for channel characterization of Rayleigh fading channel. Next, the measurement setup has been conducted in reverberation chamber which emulates multipath fading phenomena. In reverberation chamber, four different cases have been examined by changing the boundary conditions inside it with and without flat microwave absorbers. This investigation leads to obtained scattered plots, normalized propagation delay profiles (PDPs), mean excess delay, root-mean-square (RMS) delay spread and envelope distribution of Rayleigh fading channel at about 24.591 GHz.

The design studies of Microstrip filter integrated with Peano fractal defected ground structure (DGS) presented in this paper. A low pass filter (LPF) having a cut-off frequency of 1.9 GHz using modified Peano fractal DGS proposed. A modified Peano fractal structures are inserted in different sections of a conventional dumbbell shaped DGS and compared their performance figures such as roll-off factor, insertion loss, selectivity, effective capacitance and effective inductance, etc. All iterations of the Peano fractal DGS have been compared. On the basis of best simulated results, FRF (Fractal-Resonator-Fractal) configuration of the Peano fractal DGS has been proposed. The prototypes of the proposed design fabricated and frequency responses measured. The measured and simulated results agree with each other.

Use of defected ground structure (DGS) to reduce the size of patch antenna is presented in this paper. In order to get a dipole like radiation pattern for some specific application a dumbbell shaped DGS is used in the common ground plane of back to back combined single fed proximity coupled antenna. A size reduction of about 60% is achieved. Parametric analysis has been done to see the resonance behavior of the antenna with DGS.

The goal of this paper is to use defected ground structure (DGS) in microstrip antennas for dual band operation at microwave frequencies. The soft nature of the DGS facilitates improvement in the performance of microstrip antennas. A design study on microstrip patch antenna with speciflc DGS slot has been presented in the proposed work. In this paper, a stacked microstrip patch antenna (SMPA) has been designed for broadband behavior, and then skew- F shaped DGS has been integrated with a detailed study of possible DGS slots in a small area for dual band operation. The design and optimization of both the SMPA and DGS structures along with the parametric study were carried out using CST Microwave Studio V.9. Further, the dual band antenna, i.e., the SMPA with skew-F shaped DGS, has been fabricated, and the experimental results have shown a good agreement with the simulation ones.

A printed wide-slot antenna with a centred rectangular parasitic patch, fed by a fork-like tuning stub with rectangular parasitic elements adjacent to the main feed line is proposed and discussed. The proposed wide-slot antenna eliminates the need of rotation of the slot and parasitic patches both in the ground plane for the improvement in impedance bandwidth. The experimental results indicate that the presented antenna has a bandwidth (-10 dB) of more than 148% ranging from 2 to 13.5 GHz. The total size of the proposed antenna configuration is 44.3 × 44.3 × 0.508 mm 3 .

In this paper, a compact narrow band bandpass filter is proposed with hexagonal dumbbell shaped defected ground structure in ground plane of a 50Ω microstrip line and a closed loop resonator in the conducting strip. This arrangement provides better coupling in pass band. Using DGS structure, forward transmission loss (S21) is −0.5 dB and return loss (S11) is −26.7 dB at the centre frequency 5.4 GHz with narrow bandwidth of 500 MHz. A conventional parallel coupled line bandpass filter has also been implemented with exactly same design goals for the sake of comparison. The proposed bandpass filter with DGS is quite promising with 60% size reduction.

A modified ground plane structure that can enhance the performance of the closely packed radiating elements is proposed and studied in this paper. The structure consists of a two element square patch array having defected ground structure (DGS). Two different classes of DGSs were used (i) to reduce the size of the whole array and (ii) to reduce the mutual coupling between the radiating elements. Size reduction of approximately 26% and at the same time mutual coupling reduction of about 12dB was achieved with 0.5 0 spacing between the radiating elements at the center frequency of 5.25 GHz. A bandwidth of 235MHz was obtained, making it suitable for WLAN applications. Although developed for a 2-element array, the developed principle can easily be extended for larger arrays.

The Electromagnetic bandgap (EBG) structures have been used to improve the performance of the antennas. In this work, an extensive design study of some specific antennas will be presented. The design of antennas with one-dimensional EBG, so called Defected ground structure (DGS) has been carried out for various parameters improvement. The present study includes dumbbell shaped slots in the ground plane of the antennas. The initial results are indicating that using a DGS in the ground plane of the planar structures increases their electrical length and prevent the propagation in a particular band.

Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. Although the DGS has advantages in the area of the microwave filter design, microstrip antenna design for different applications such as cross polarization reduction and mutual coupling reduction etc., it can also be used for the antenna size reduction. The etching of a defect in the ground plane is a unique technique for the antenna size reduction. The DGS is easy to be an equivalent LC resonator circuit. The value of the inductance and capacitance depends on the area and size of the defect. By varying the various dimensions of the defect, the desired resonance frequency can be achieved. In this paper the effect of dumbbell shaped DGS, to the size reduction of a microstrip patch antenna is investigated. Then a cavity backed structure is used to increase the efficiency of the microstrip patch antenna, in which the electric walls are placed surrounding the patch. The simulation is carried out with IE3D full wave EM simulator.