Wireless capsule endoscopy (WCE) was developed as a painless diagnostic tool for endoscopic examination of the gastrointestinal (GI) tract, but, to date, the low operating power of the capsule and the high data rate of the RF telemetry system are still key concerns. Innovative, novel solutions must be developed to address these concerns before WCE can be used extensively in clinical applications. In this paper, we propose a novel RF transmitter for WCE applications that only requires 1.5 V to transmit the required data as opposed to using a DC power supply. Our proposed, direct-conversion transmitter system consists of a current reuse oscillator, an envelope filter, and an L-section matching network. The oscillator is powered by the transmitting data which keep the oscillator in turned on and off for the transmitting 1 and 0 bit respectively and results in the on-off keying (OOK) of the modulated signal at the output of the oscillator. The rate of data transmission at the modulated signal is limited by the transient period of the oscillator start-up. When the start-up time of the oscillator is optimized, an OOK modulation rate of 100 Mb/s can be attained. In order to eliminate the oscillator decay noise, we used an envelope filter connected in series with the oscillator to filter out the decay part of the oscillation. Finally, the output impedance of the envelope filter is matched to the 50-Ω antenna with an L-section, low-pass, matching network to ensure maximum power transmission. The entire transmitter system was simulated in a 0.18-μm Complementary metal-oxide-semiconductor (CMOS) process.

This paper presents a new type of a negative coupling structure for designing elliptic-response filters with cross-coupling. The proposed coupling structure consists of short-circuited coupled transmission lines. Using the fact that insertion phase of the coupled line structure is different from that of an inductive iris, it is shown that the proposed coupling structure can be used as the negative coupling structure. In order to verify the proposed coupling structure, we designed a 4th-order cross-coupled elliptic-response bandpass filter with substrate integrated waveguide resonators. A pair of transmission zeros in measurement and simulation results validates that the proposed structure can be used as the negative coupling structure.

In this paper, we reformulate the quasi-static spectral domain analysis (SDA) applicable to a lossy anisotropic multilayer asymmetric coplanar waveguide (ACPW). The SDA formulation also incorporates two-layer model of a conductor thickness and the concept of effective permeability to account for the low frequency dispersion due to the magnetic field penetration in an imperfect conductor. The paper further presents the single layer reduction (SLR) formulation and circuit model to compute frequency dependent line parameters of a lossy anisotropic multilayer ACPW. The accuracy of formulation is comparable to that of the HFSS and CST, without using complex and time consuming full-wave methods. The results of CST for ε_eff, Z₀, α_d, α_c of multilayer ACPW, in the frequency range 1 GHz-100 GHz, deviate from results of HFSS up to 0.49%, 1.53%, 2.06% and 10.73% respectively; whereas corresponding deviations of the present SDA and SLR combined formulation are up to 1.38%, 2.09%, 3.57% and 8.87%.

In the present paper a novel mathematical model of physical processes of transient electromagnetic waves excitation and propagation in a biconical transmission line with radially inhomogeneous magneto-dielectric filling is proposed. The model is based on time domain mode expansions over spherical waves. The basis functions of the mode expansions are calculated analytically. The mode expansion coefficients are governed by Klein-Gordon-Fock equation with coefficients depending on a radial spatial coordinate. The explicit finite difference time domain computational scheme is derived to calculate the mode expansion coefficients. Dependences of cutoff frequencies of higher modes of TE and TM waves on the line geometry and dielectric filling are studied. In order to calculate electromagnetic field in the line with higher accuracy, just finite number of terms in the mode expansions is required. Electromagnetic field excited by the transient electric ring current is calculated in both homogeneous and radially inhomogeneous biconical transmission line. It is shown that there is a possibility to increase the bandwidth of the line via introduction of partial dielectric filling without changing the line geometrical size.

As the distribution of the multiuser interference plus noise in time-hopping ultrawide bandwidth (TH-UWB) systems can not be reliably approximated by Gaussian probability density function (PDF), the bit error rate (BER) performance of the conventional matched filter receiver in TH-UWB multiuser systems degrades. In this paper we study a novel TH-UWB receiver based on two PDFs approximating the distribution of the multiuser interference plus noise. Firstly we investigate the difference between the distribution of the multiuser interference plus noise when the received pulse is collided by interfering pulses and that when it is not. Then two PDFs are developed to approximate the distribution of multiuser interference plus noise in these two cases respectively instead of using one PDF for both cases as done in other research works. Based on these two PDFs, a new detection scheme of TH-UWB receiver is proposed. The results show that BER performance of the proposed receiver is improved by 50% or more as compared to the conventional matched filter receiver, blinking receiver, Gaussian mixture receiver and p-order receiver using simulations.

This paper proposes an efficient parallel shooting and bouncing ray (SBR) method on the graphics processing unit (GPU) cluster for solving the electromagnetic scattering problems. At each incident direction, the parallel SBR method partitions the virtual aperture into sub-apertures, and distributes the computational process of each sub-aperture over GPU nodes. As ray tubes in the virtual aperture do not have the same computational time, the parallel efficiency highly depends on how to partition the virtual aperture. This paper addresses this issue by a dynamic partitioning scheme according to the computational time at the previous angle, which can achieve excellent load balance. Numerical examples are presented to demonstrate the accuracy, high parallel efficiency, good scalability and versatility of the proposed method.

The reduction in the radiation efficiency of an antenna in a mobile handset due to user's hand effects in the talking and data modes is studied. A parameter called "body loss" is defined to evaluate the degradation of the radiation efficiency. A C-fed on-ground (OG) PIFA antenna, which can cover two typical LTE bands of 0.75 GHz-0.96 GHz and 1.7 GHz-2.1 GHz, is used to study the property of the hand-effect body loss in two CITA test positions: the talking and data modes. Three different positions of the proposed antenna in the talking mode are compared, and the position with the antenna located on the bottom of the mobile handset and facing the head phantom is recommended for minimal body loss. A new modified design with a smaller antenna width is proposed to reduce the hand-effect body loss in the talking and data modes.

A 2-D analytic based eddy-current transient model for a conducting plate is derived that is capable of accounting for continuous changes in the input conditions. Only the source field on the surface of the conducting plate needs to be known. In addition, a 2-D steady-state analytic based eddy-current model that is capable of accounting for frequency and velocity changes in two directions is derived. Both analytic based models have been validated using finite element code. The transient and steady-state models are integrated into an electromechanical system where the magnetic source is a Halbach rotor. The accuracy of both calculation methods is compared. The stiffness and damping coefficients are derived using the steady-state model.

Arrangements of bilayer anisotropic structures are inspected in this paper that manifest wonderful behaviors. One of these arrangements can pass TM & TE modes spontaneously in low frequencies and reflect them in higher frequencies and function as a low-pass filter. Another arrangement can reflect TE mode and pass TM mode in a particular frequency band and vice versa and function as a polarizer. All the analyses are based on the calculations of the hybrid matrix of layers by means of a recursive algorithm. Also the effect of the μ & ε tensors on the specifications of the filters is discussed.

The pattern of each element in conformal array has a different direction for the curvature of conformal carrier, which results in polarization diversity of conformal array antenna. Polarization parameters of incident signals are considered in snapshot data model in order to describe the polarization diversity of conformal array antenna. It is required that the polarization parameters and direction of arrival (DOA) of incident signals are estimated together. An integrated frequency and DOA estimation method is proposed in this paper for cylindrical conformal array antenna. The frequency estimation of signal source is obtained by constructing state-space matrix. Through well-designed configuration of elements on cylindrical carriers along with estimation of signal parameters via propagator method (PM), the decoupling scheme for DOA and polarization parameters is implemented. A novel parameter pairing method for frequency and DOA of multiple sources utilizing the interpolation technique is given, based on which the fast frequency-DOA estimation algorithm is developed. Effectiveness of the proposed method is demonstrated by simulation experimental results.

A novel type of radio frequency identification (RFID) reader antenna is proposed for mobile ultra-high frequency (UHF) RFID device. By folded-dipole loop structure with parasitic element, a small antenna size of 31 * 31 * 1:6 mm³ is achieved. The antenna with different parasitic element size can work on different UHF RFID bands. The antenna prototype is fabricated and the measured bandwidth is around 13.5 MHz (915.5-929 MHz), which covers the China RFID Band (920-925 MHz). The measured reading distance achieves 65 mm with the near-field RFID tag and 1.17 m with the far-field tag. The measurement agrees well with simulated result and shows that antenna is desirable for both near-field and far-field UHF RFID applications.

Schools and universities often need to support theoretical lectures on Radio Astronomy with practical lessons; in addition, science centres need instruments to explain this subject to the general public. However, professional radio telescopes are largely inaccessible to students and the public, because they tend to be very costly and are still fairly uncommon. It would seem, therefore, interesting to explore the possibility of designing a low-cost radio telescope for teaching purposes. The most critical part of a radio telescope is its receiver; considering the low intensity of radiation from the radio sky, this needs, among other features, to be very sensitive, necessitating the use of expensive low noise amplifiers, often cooled to low temperatures. 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 demonstrative radio telescope, using, as a front-end, an LNB mounted in the focus of an offset parabolic mirror. Unlike other designs, we made the system suitable for environments with high electromagnetic noise, such as schools in urban centres, by using a bandpass filter in the Intermediate Frequency section.

A straightforward approach is proposed to retrieve the effective electromagnetic parameters of a slab of bianisotropic material from the scattering parameters. We first obtain the values of the impedance and refractive index of a slab of metamaterial, followed by the deduction of the expressions for determining these electromagnetic parameters including permittivity, permeability and magnetoelectric coupling coefficient. Then, comparisons between the results coming respectively from retrieval technique and analytical method are made. Finally, we demonstrate the properties of split-ring resonator materials in other two orientations with respect to the incident plane wave and apply the proposed method to anisotropic materials to reveal its generality.

This paper presents a novel synthesis technique for microwave bandpass filters with frequency-dependent couplings. The proposed method is based on the systematic extraction of a dispersive coupling coefficient using an optimization technique based on the zeros and poles of scattering parameters representing two coupled resonators. The application of this method of synthesis is illustrated using two examples involving four and five-pole generalized Chebyshev filters implemented in substrate-integrated waveguide (SIW) technology. As a dispersive inverter, a parallel shorted stub with an additional septum was used. The septum lends greater flexibility to the dimensional synthesis, in that it increases the allowable range of the coupling coefficients. The measured and simulated results are in excellent agreement, which confirms the validity of the proposed approach.

In this paper, we adopt the Levenberg-Marquardt (LM) algorithm to implement the nonlinear multivariable optimization for azimuth/elevation angle-of-arrival (AOA) estimation based on the Capon beamforming algorithm. The formulation is based on the fact that the cost function of the Capon algorithm can be expressed in a least-squares form. The performance in terms of the root mean square error (RMSE) and the computational complexity is illustrated via numerical results.

The fuzzy fractal characteristics of return signals from aircraft targets in conventional radars offer a description of dynamic features which induce the targets' echo structure, therefore they can provide a new way for aircraft target classification and recognition with low-resolution surveillance radars. On basis of introducing fuzzy fractal theory, the paper analyzes the fuzzy fractal characteristics of return signals from aircraft targets in a VHF-band surveillance radar by means of the fuzzy fractal analysis, and puts forward a fuzzy-fractal-feature-based classification method for aircraft targets with a low-resolution radar from the viewpoint of pattern recognition. The analysis shows that the fuzzy fractal characteristic parameters such as the local fuzzy fractal dimension (LFFD) and local degree of fractality (LGF) can be used as effective features for aircraft target classification and recognition. The results of classification experiments validate the proposed method.

We propose an automatic and accurate technique for classifying normal and abnormal magnetic resonance (MR) images of human brain. Ripplet transform Type-I (RT), an efficient multiscale geometric analysis (MGA) tool for digital images, is used to represent the salient features of the brain MR images. The dimensionality of the image representative feature vector is reduced by principal component analysis (PCA). A computationally less expensive support vector machine (SVM), called least square-SVM (LS-SVM) is used to classify the brain MR images. Extensive experiments were carried out to evaluate the performance of the proposed system. Two benchmark MR image datasets and a new larger dataset were used in the experiments, consisting 66, 160 and 255 images, respectively. The generalization capability of the proposed technique is enhanced by 5 × 5 cross validation procedure. For all the datasets used in the experiments, the proposed system shows high classification accuracies (on an average > 99%). Experimental results and performance comparisons with state-of-the-art techniques, show that the proposed scheme is efficient in brain MR image classification.

Two ultra-wideband (UWB) microstrip bandpass filters (BPFs) are proposed by using tunable E-shaped dual-mode microstrip Stepped-Impedance Resonator (SIR). For the lower band filter measurement results show there is a passband of 3.1 GHz to 5.2 GHz and its 3 dB fractional bandwidth is 51%. The UWB upper band filter may be obtained by tuning E-shaped SIR. The measurement results show there is a passband of 6 GHz to 10.6 GHz and its 3 dB fractional bandwidth is 55%. Compared with the similar investigation using the cascade of electromagnetic band gap (EBG)-embedded multiplemode resonator (MMR) and fork resonator, the proposed approach has some advantages, such as easier adjustment of bandwidths, better passband performances and smaller size etc.

A high-directivity patch antenna with broadside directivity is attractive, since a narrow beam can be obtained without the need of using an array of antennas. Therefore, the solution becomes simpler as there is no need for a complicated feeding network. In this sense, this paper presents a novel patch antenna design with high directivity in the broadside direction by using genetic algorithms (GA). The proposed GA method divides the overall patch area into different cells taking into account that cells have a small overlap area between them. This avoids optimized geometries where cells have only an infinitesimal connection. Therefore, the proposed method is robust for manufacturing. The antenna operates in a higher-order mode at 4.12 GHz and the geometry fits inside a patch of 40 mm × 40 mm on a substrate with a relative permittivity of 3.38 and a thickness of 1.52 mm resulting in a directivity of 10.5 dBi. The specialty of this design is the use of GA to select the optimized shape and the feeding position instead of a known shape and a fixed feeding position. The antenna has been fabricated and the simulation results are in good agreement with the measurements. This results in a simpler design of a single high-directivity patch, which can substitute an array of two elements operating in the fundamental mode.

In this paper, a novel miniaturized nested split-ring resonator (SRR) structure is proposed. The nested SRR structure incorporates multiple split-ring resonators in a compact nested structure, and has more split gaps than the conventional SRR structure. Compared with conventional SRR, this nested SRR has better performance on miniaturization and high-Q value. To verify good characteristics of the proposed resonator structure, a novel resonator-embedded band-pass filter (BPF), which is constructed by four nested resonators, is designed. This novel BPF is very compact and has good in- and out-band performances. The proposed nested SRR unit cell has size of 0.04λ_g x 0.04λ_g(λ_g is the signal wavelength at the 2.4 GHz central frequency of the pass-band). Its stop-bands are extended 0.5~2 GHz at lower band and 2.7~5.4 GHz at upper band with a rejection level of higher than 20 dB, and its 1-dB pass-band is 2.2~2.55 GHz with 1.8 dB optimized insertion loss. The measured and simulated results are well complied with each other.