Volume 74, Issue 3-4 -

The radar coincidence imaging (RCI) doesn’t rely on relative motion between target and radar, but its super-resolution characteristics requires a large sample size of the radiation fields. In the actual operation, transmitting too many signals at once not only requires large antenna array, but also easily causes aliasing. Thus the model of adaptive frame-iteration compressive sensing (AFCS) was proposed in this paper. Compared to the traditional antenna array, MIMO antenna array [1] transmits signals independently and ensures low enough correlations between every array element. Based on the spatial multiplexing characteristics of MIMO antenna array, in each iteration-frame the randomly selected array elements transmit incoherent signals, and the scattering coefficients of target plane can be obtained by correlation processing of the echo signal and the reference signal. Moreover, according to the distribution of scattering coefficients, we can combine frame-iteration and compressive sensing to realize super-resolution imaging. Numerical simulation results demonstrate that the proposed model is feasible.

Two-dimensional (2D) direction-of-arrival (DOA) estimation with arbitrary planar sparse array has attracted more interest in massive multiple-input multiple-output application. The research on this issue recently has been advanced with the development of atomic norm technique, which provides super resolution methods for DOA estimation, when the number of snapshots is limited. In this paper, we study the problem of 2D DOA estimation from the sparse array with the sensors randomly selected from uniform rectangular array. In order to identify all azimuth and elevation angles of the incident sources jointly, the 2D atomic norm approach is proposed, which can be solved by semidefinite programming. However, the computational cost of 2D atomic norm is high. To address this issue, our work further reduces the computational complexity of the problem significantly by utilizing the atomic norm approximation method based on the concept of multiple measurement vectors. The numerical examples are provided to demonstrate the practical ability of the proposed method to reduce computational complexity and retain the estimation performance as compared to the competitors.

With the advantage of high flexibility, unmanned aerial vehicle (UAV) can be deployed in a high height to provide high probability of line-of-sight (LoS) transmission for the ground units. Thus, UAV can bring much gain for communication systems. In this paper, we consider that a set of UAVs are deployed in the air to work as relays to aid the ground device-to-device (D2D) pairs. For the reason that the communication resource on one relay is limited and the positions of the relays are different, network performance is significantly impacted by relay assignment. Considering that there is no central controller in this relay network, centralized relay assignment approaches cannot be used. Thus, we propose a novel decentralized relay selection approach based on relay exchange, aiming to maximize the total capacity of the network. With the proposed approach, the total capacity of the relay network is strictly non-decreasing with the increase of the iteration steps. Numerical results show that the proposed approach have attractive properties.

A two-port MIMO Dielectric Resonator Antenna (DRA) has been studied and developed. The proposed antenna consists of a single Rectangular DRA (RDRA). The antenna is integrated with the substrate and electrified using coaxial feed, which excites hybrid TM mode in the DR. The mutual coupling within both the ports has been reduced by employing copper shielded on two vertical walls of a rectangular cavity in the centre of DRA. A parametric study has been done to attain optimum parameters, and then the proposed antenna has been fabricated. The presented antenna with acceptable MIMO characteristics covers a measured bandwidth of 1.24 GHz (2.16 GHz – 3.4 GHz) for |S 11 | ≤ −10 dB, which can operate on LTE bands. The measured isolation between the two ports in the operating band is more than 25 dB. The proposed antenna renders easy fabrication and feeding with good MIMO characteristics. Therefore, the proposed 3D printable MIMO antenna is worthy for LTE applications.

Due to the fields in the near-field area of an electric dipole source which is sharply and rapidly varying with distance, a novel approach to introduce an underwater low-frequency excited source is proposed in this paper. The approach is built up to combine the theoretical solution for an electric dipole in a conductive medium with the total-field scattered-field boundary to reduce the error in modeling the source. The spatial distributions of the magnetic field amplitude at a distance of 1 km above the sea surface are discussed. The numerical results verified the accuracy and validity of the approach by comparing with the results of the Sommerfeld numerical integration method.

This paper includes a design analysis of an inductorless low-power (LP) low-noise amplifier (LNA) with active load for Ultra Wide Band (UWB) applications. The proposed LNA consists of two parallel paths, one is the common source (CS) path and second is the CG path. The CG path has the edge advantage of improving overall Noise figure (NF) due to wide band impedance matching in UWB, while the CS path provides high power gain. A method for noise cancellation is adopted, to reduce the noise of CS path with the help of CG path. The proposed LNA successfully simulated in 90 nm CMOS technology. The results of proposed work indicate optimization at frequency 5.70 GHz with 3 dB bandwidth of 4.3 GHz–8.9 GHz. All simulations have been done for a range of frequency 03 GHz–13 GHz in Cadence virtuoso software. The results quoted 1.15 dB NF, −18.12 dB S 11, 13.7 dB S 21, maximum operating power gain (GP) 11.756 dB at frequency 5.7 GHz and available power gain (GA) is 10.17 dB at frequency 8.61 GHz, with 0.6 V, 0.92 mW broad band LNA.

In this paper, a new method to decrease the dimensions of the microstrip structures and reducing the overall size of the class F amplifiers is presented. First, by using the PHEMT transistor with a conventional harmonic control circuit (HCC), a low-voltage class F amplifier in the L band frequency at the operating frequency of 1.75 GHz is introduced, which named primitive class F power amplifier. Then, this amplifier is optimized by using capacitor loaded transmission lines (CLTLs). The measurement results of the amplifier show that by using the CLTL structure, the overall size has been reduced 85% (0.23 λ g × 0.17 λ g ). The maximum power-added efficiency (PAE) of the power amplifier is about 77.5 % and the power gain which has been reached to 18.33 dB. The desirable features of this power amplifier, along with its very small size, make this power amplifier a good choice to use for the global system for mobile communications.

In this paper, a waveguide consisting of a core of As 2 Se 3 chalcogenide glass and the upper and lower claddings of MgF 2 with two zero-dispersion wavelengths (ZDW) has been proposed. By optimization of the dimensions of the core and the claddings, their effects on the dispersion curve have been investigated and a suitable structure with a flat dispersion curve, an effective mode area of ​​1.6 μm 2 in a pump wavelength of 2.8 μm, and hence, a nonlinear coefficient greater than 34 w −1  m −1 has been obtained. A broadband supercontinuum in a wavelength range of 1.5 μm to 15 μm has been generated by applying an input pulse with duration of 100 fs and a maximum power of 2 kw to this waveguide. Due to the large width of the supercontinuum generated (SCG), the short length of the waveguide (maximum 5 mm), and a low input power, this structure is suitable for use in optical integrated circuits and its various applications.

This paper presents a position-independent reflection-only method for determining complex permittivity and permeability of a sample. In this method, both the short and match calibration kits are used to measure the reflection coefficients. Only one sample positioned arbitrarily is measured using a one-port vector network analyzer (VNA), while the complex permittivity and permeability of the sample are determined simultaneously. Experimental results in X-band for the Acrylonitrile Butadiene Styrene plastic (ABS) are included to exhibit the validity of the proposed method. The results show that the complex permittivity and permeability determined by the proposed method have a good agreement with the parameters determined by the well-known Nicolson–Ross–Weir (NRW) method. In addition, a magnetic material is simulated to further validate the proposed method.