A printed discone antenna with dual-band notched characteristics is presented for ultra-wideband applications. The proposed antenna consists of a radiation patch which has an outline expressed by binomial function and a trapeziform ground plane. Dual band-stop performance is achieved by etching a pair of Z-shaped slots on the ground plane and protruding a pair of π-shaped strips in the elliptical slot cut in the radiation patch, respectively, which can reject potential interference with the 3.25-3.8 GHz and 5-6 GHz bands. Surface current distributions and input impedance of the antenna are given to analyze the effects of the two resonant structures. The characteristics of the notched bands can be controlled independently by tuning related parameters. Moreover, the performances of the antenna are validated along with simulated and measured results.

This article reports on the design of a wideband compact microstrip-fed tapered slot antenna aimed at microwave imaging of a brain stroke. The antenna is immersed in a carefully designed coupling liquid that is used to facilitate higher signal penetration in the brain and thus increased dynamic range of the imaging system. A parametric analysis is used to find out the required properties of the coupling liquid. A suitable mixture of materials is then used to implement those properties. In order to protect the antenna from the adverse effects of the coupling medium, dielectric sheets are used to cover the radiator and the ground plane. To verify the proposed design in brain imaging, the antenna is tested using a suitable head model. It is shown that the antenna with a compact size (24 mm × 24 mm) on RT6010 substrate (dielectric constant = 10.2) operates efficiently over the band from 1 GHz to more than 4 GHz with more than 10 dB return loss. The time domain performance of the antenna supports its capability to transmit a distortion-less pulse with a high fidelity factor inside the head tissues.

There is some evidence that exposure of various animals to a power-frequency magnetic field can cause increases in body mass. However, the precise nature of the relationship is not clear, particularly for long-term exposure. To clarify the relationship between long-term power-frequency magnetic field exposure (2 years) and animal body mass, we conducted a pooled analysis of data in two studies to examine the impact of power-frequency magnetic field exposure on body mass as compared with sham-exposed rats of both sexes. Relative body mass was the response variable, and the study duration (in weeks), magnetic flux density ($\upmu$T), and daily exposure time (hours/day) were the explanatory variables with adjustment for the study. We analyzed by sex. The P-value (P) was defined as the probability of having observed our data (or more extreme data) when the null hypothesis was true. In multiple linear regression analyses of male and female rats, performed separately, we obtained estimates of the effect on relative body mass of study duration (coefficients 0.0225 and 0.0201, respectively; both P<0.0001), magnetic flux density (coefficient 0.0002 for males, P<0.0001; coefficient -0.0002 for females, P=0.0015), and daily exposure time (coefficient 0.046 for males, P=0.0007; coefficient -0.072 for females, P<0.0001). Our pooled analysis has shown that there is a possible relationship between duration of exposure to power-frequency magnetic fields and body mass in rats.

In this paper, we propose a multi-beam and multi-range (MBMR) radar with frequency modulated continuous wave (FMCW) waveform and digital beam forming (DBF) algorithm to cover a detection area of long range and narrow angle (150 m, ±10°) as well as short range and wide angle (60 m, ±30°) as a single 24 GHz sensor. The developed radar is highly integrated with multiple phased-array antennas, a two-channel transmitter and a four-channel receiver using K-band GaAs RF ICs, and back-end processing board with subspace-based DBF algorithm. The proposed 24 GHz MBMR radar can be used for an adaptive cruise control (ACC) stop-and-go system which typically consists of three radars, such as two 24 GHz short-range radars for object detection in an adjacent lane and one 77 GHz long-range radar for object detection in the center lane.

Small size capacitor loaded ground plane slots are used to reduce the mutual coupling between elements in a microstrip antenna array design. The proposed compact slots are inserted between the adjacent E-plane coupled elements in the array to limit the propagation of surface waves between the elements of the array. In order to validate the feasibility of the proposed structure, a two-element array with 0.5λ_o distance between centers of two patches is designed, fabricated, and measured. The measured results show a reduction in mutual coupling of 17 dB obtained between elements at the operation frequency of the array.

Compact K-Band CMOS baluns are designed, fabricated and characterized in a 130 nm CMOS technology. These baluns include a tunable active balun, a L-C lumped element balun, and two asymmetric planar transformer baluns. The detailed design processes are presented, including the topology selection, the transistor, inductor and transformer sizing, and the layout considerations. These topologies are compared in various aspects such as insertion loss, phase and amplitude imbalance, bandwidth, chip area, power consumption, and the difficulty to design and integration. An impedance tuning approach is implemented to chose the proper balun topology and to simply the balun integration. The baluns are on-wafer characterized and the measurement results compare the state-of-the-art realizations..

This paper presents characterization and modeling of microwave characteristics of SiC foam material. Transmission and reflection measurements are performed in X, K and Ka band for the samples of two different pore sizes and three different thicknesses. Effective and frequency dependent dielectric permittivity is extracted for 50PPI 10 mm sample, while for the other samples it was not possible because of density gradient in the samples. By calculation of Mie scattering efficiencies approximate magnitude of dominant loss mechanism (scattering or absorption) at certain frequencies is predicted.

This study quantifies the detuning and impedance mismatch of antennas implanted inside the human body. Maximum frequency shifts caused by variations in the electrical properties of body tissues and different anatomical distributions were derived. The results are relevant to the design of implantable antennas. They indicate the bandwidth enhancement and initial tuning necessary for correct functioning. The study was carried out using electromagnetic modeling based on the finite-difference time-domain method and high-resolution anatomical models. Four anatomical computer models of two adults and two children were used. The implanted antennas operated in the Medical Implant Communication Service band. The most important detuning and impedance mismatch was found for subcutaneous locations and in areas where a layer of fat tissue was present. The maximum frequency shift towards higher frequencies was 70 MHz. The frequency shift did not occur symmetrically around 403 MHz, but was shifted towards higher frequencies.

An improved designable composite right/left-handed transmission line (CRLH-TL) is presented in this paper, whose operating frequency-band and transmission characteristics can be tuned, respectively, by three structure variables. The equivalent characteristic impedance is studied carefully, and CRLH-TLs with arbitrary characteristic impedances are obtained. Some useful empirical formulae are derived for engineering application. Then, a sample of 50-Ω CRLH-TL, which can be used directly as a wide-band filter, is fabricated with the center frequency of 2.8 GHz. The measured results show that a relative 3-dB bandwidth of 74.6% is achieved, in good agreement with the simulated results. Moreover, the phase-frequency responses of our proposed CRLH-TLs are discussed in detail. A novel hybrid ring is then proposed, where 70-Ω CRLH-TL is used. At the center frequency of 5.8 GHz, equal power dividing is achieved with return loss and isolation more than 20 dB and 30 dB, respectively. The sample is finally fabricated and good agreements among theoretical analysis, simulated results, and measured results are obtained.

Terahertz (THz) spectroscopy can potentially be used to probe and characterize inhomogeneous materials. However, identification of spectral features from diffuse scattering by inhomogeneous materials has not received much attention until now. In this paper, THz diffuse scattering from granular media is modeled by applying radiative transfer (RT) theory for the first time in THz sensing. The diffuse scattered field from compressed polyethylene (PE) pellets containing steel spheres was measured in both transmission and reflection modes using a THz time domain spectroscopy (THz-TDS) system. The RT model was validated by successfully reproducing qualitative features observed in experimental results. Diffuse intensity from granular media containing lactose was then simulated using RT theory. In the results, spectral features of lactose were observed in the diffuse intensity spectra from the granular media.

Impact of electromagnetic interference on front-end receiver behaviour is theoretically and experimentally studied outside the bandwidth of the antennas. Microwave chaotic generation is observed. Under certain conditions, reflected waves combined to the non linearity of the front-end receiver leads to a chaotic signal generation between the antenna and the front-end receiver. Different antennas, such as patch, loop, monopole and horn, are tested. Theoretical and experimental results are presented for each antenna.

Recently, we proposed a wireless ambulatory gait analysis system that provides a high ranging accuracy using ultra-wideband (UWB) transceivers. In this paper, we further investigate the performance of our proposed system including ranging using suboptimal templates, power consumption, and sensor-fusion. We show that the proposed system is capable of providing a 1.1 mm ranging accuracy (1.17 cm for current systems) at a signal-to-noise-ratio (SNR) of 20 dB using suboptimal-based receivers in industry accepted body-area-network UWB channels. For the angular-displacement, our system provides an accuracy that is less than 1^o for the knee-flexion angle. This accuracy is superior to the accuracy reported in the literature for current technologies (less than 4^o). Finally, we propose the integration of UWB sensors with force sensors. The system performance and design parameters are investigated using simulations and actual measurements. Ultimately, the proposed system is suitable for taking accurate measurements, and for tele-rehabilitation.

This paper presents a novel modified composite right/left-handed (CRLH) unit cell to achieve sharp rejection at 5.8 GHz. Design formulas are theoretically derived and numerically verified. Based on this unit cell, ultra-wideband (UWB) bandpass filters with two and three cells are designed, fabricated, and on-wafer measured. The measurement results show that the CRLH bandpass filter has a rejection of >60 dB at 5.8 GHz, a minimum insertion loss of 1.1 dB, and 3-dB bandwidths of 3.09-4.79 GHz and 3.22-4.61 GHz for the two and three unit cells, respectively.

This paper deals with several aspects relative to the Multiple-Input Multiple-Output (MIMO) propagation channel. Measurement campaigns, made in a real gold mine at 2.4 GHz under line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios, have been analyzed to obtain the relevant statistical parameters of the channel. It was shown that the MIMO exploit the multipath propagation in rich scattering environment to increase the capacity. Hence, the channel is characterized in terms of K-factor, path loss, shadowing, and capacity. Results show a propagation behavior that is specific for these underground environments with rough surfaces.

A novel compact bandpass filter (BPF) with wide upper-stopband has been proposed in this paper. The structure is based on spiral-shaped resonators. Cross coupling is used to generate two transmission zeros at the lower and upper stopbands. Therefore, the out-of-band performance is improved. In addition, two spur-lines are adopted in the feed lines to reject the spurious response. The central frequency f₀ of this filter is at 2.45 GHz with a minimum insertion loss of less than 1 dB and a 3 dB bandwidth of 12.5%. Four transmission zeros are located at 2 GHz, 3 GHz, 5.5 GHz, and 8 GHz. The attenuation is greater than 20dB in a wide upper stopband up to 9.8 GHz.

A new image reconstruction algorithm for early breast cancer detection using ultra-wideband microwave signals is proposed. In this algorithm, the backscattered electric and magnetic fields are measured and combined in a novel way; the direction of power flow with respect to a given focal point is used to localize tumors. Significant improvement in signal-to-mean raito (SMR) and signal-to-clutter ratio (SCR) are achieved when driving signals consist of waves with multiple polarizations. Numerical results demonstrate nearly 5.5 dB improvement of SMR and SCR over the traditional Confocal Microwave Imaging method when a single 8 mm breast tumor is present. Breast Cancer Facts Figures 2011-2012

We report on experimental and numerical studies on the coupling effect of a single split ring resonator (SRR) and its mirror image inside an X-band hollow waveguide. It is shown that, for single SRR with gap bearing side perpendicular to $E$ field, the magnetic resonance exhibits red/blue shift as SRR moves to the gap facing/backing waveguide edge, due to the capacitance and magnetic dipoles coupling effect between original SRR and its mirror image, respectively. Furthermore, electric dipole interplay dominates the coupling effect between SRR and its image when SRR has the gap bearing side parallel to the E field, although SRR is excited by E and H field simultaneously.

A standalone, printed monopole antenna with a two-branch shorting strip and a grounding wire to achieve a small size and yet multi-band operation for penta-band wireless wide area network (WWAN) operation (824-960/1710-2170 MHz) is presented. The antenna was formed on a low-cost, single-layered dielectric substrate with the dimensions 10 mm×50 mm. By applying the proposed grounding wire and the dual-shorting strip, two resonant modes in close proximity in the antenna's lower band were obtained to cover the GSM850/900 operation. Further, the proposed shorting strip led to two additional, higher-order resonance excitation at about 1700 and 1800 MHz to assist in the formation of a wide upper band to cover the GSM1800/1900/UMTS operation. The proposed antenna also showed good radiation properties. Details of the design are described and discussed in the article.

A new class of miniaturized dual-mode substrate integrated waveguide (SIW) band-pass filters is proposed, which are loaded by double/single T-shaped structures. By introducing a double T-shaped structure in original dual-mode SIW band-pass filter, the resonant frequency is lowered from 9.46 GHz to 8.91 GHz due to the longer effective length. The introduced single T-shaped structure performs an even lower resonant frequency of 6.88 GHz for the same reason. Compared with dual-mode band-pass filters in references, the proposed dual-mode SIW band-pass filters with double/single T-shaped structures have the advantages such as compact size (like microstrip dual-mode filters) and high Q factors (like SIW dual-mode filters). The proposed filters are fabricated and measured, and the experimental results are in good agreement with simulated ones.

The cosine window function with the parameters optimized by Genetic Algorithm (GA) is applied in bistatic planar near-field scattering measurements so as to effectively improve the measurement precision. With the infinitely long ideal conductor cylinder as the target under test, the bistatic planar near-field scattering measurement technique is studied by the method of computer simulation and some useful results and basic laws are obtained. The calculation results show that the truncation errors caused by finite scan plane in the far-field Radar Cross Section (RCS) of the target under test obtained by near-field to far-field transformation can be reduced greatly by the weighting process of the measured scattered near-field data by means of the cosine window function with the parameters optimized by GA.