A new Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar (SAR) has been developed at Multimedia University, in collaboration with Agency of Remote Sensing Malaysia. The SAR operates at C-band, single $VV$-polarization, with 5 m x 5 m spatial resolution. Its unique features include compact in size, light weight, low power and capable of performing real-time imaging. A series of field measurements and flight tests has been conducted and good quality SAR images have been obtained. The system will be used for monitoring and management of earth resources such as paddy fields, oil palm plantation and soil surface. This paper reports the system design and development, as well as some preliminary results of the UAVSAR.

Electromagnetic interference (EMI) has an adverse effect on the performance of electronic circuit communication systems. This study derives a series of equations to analyze the effects of the EMI induced in a conducting wire on the noise spectrum of a RC Phase Shift Oscillator (RCPSO). It is shown that the extent to which EMI affects the RCPSO depends on the interference power, interference frequency, induced power, output resistance of the oscillator circuit, and parasitic capacitance. Specifically, higher EMI frequencies and amplitudes have a greater effect on the RCPSO output. The results presented in this study are in good agreement with those predicted from general EMI theory.

Ultra-wideband (UWB) microwave radar imaging techniques provide a non-invasive means to extract information related to an object's internal structure. For these applications, a short-duration electromagnetic wave is transmitted into an object of interest and the backscattered fields that arise due to dielectric contrasts at interfaces are measured. In this paper, we present a method that may be used to estimate the time-of-arrival (TOA) parameter associated with each reflection that arises due to a dielectric property discontinuity (or dielectric interface). A second method uses this information to identify the locations of points on these interfaces. When data are collected at a number of sensor locations surrounding the object, the collection of points may be used to estimate the shape of contours that segregate and enclose dissimilar regions within the object. The algorithm is tested with data generated when a cylindrical wave is applied to a number of numerical 2D models of increasing complexity. Moreover, the algorithm's feasibility is evaluated using data generated from breast models constructed from magnetic resonance (MR) breast scans. Results show that this is a promising approach to identifying regions and the internal structure within the breast.

A new approach to reduce the numerical dispersion of the six-stages split-step unconditionally-stable finite-difference time-domain (FDTD) method is presented, which is based on the split-step scheme and Crank-Nicolson scheme. Firstly, based on the matrix elements related to spatial derivatives along the x, y, and z coordinate directions, the matrix derived from the classical Maxwell's equations is split into six sub-matrices. Simultaneously, three controlling parameters are introduced to decrease the numerical dispersion error. Accordingly, the time step is divided into six sub-steps. Secondly, the analysis shows that the proposed method is unconditionally stable. Moreover, the dispersion relation of the proposed method is carried out. Thirdly, the processes of determination of the controlling parameters are shown. Furthermore, the dispersion characteristics of the proposed method are also investigated, and the maximum dispersion error of the proposed method can be decreased significantly. Finally, numerical experiments are presented to substantiate the efficiency of the proposed method.

The classical interpolation-based Polar Format Algorithm (PFA) for spotlight synthetic aperture radar (SAR) results in numerous computation load, which, reduces processing speed and increase system complexity. To decrease computation load, this paper proposes a novel non-interpolation PFA algorithm for sensor flying along non-lineal flight trajectories, which are specially designed curves in conical surface. Then an innovative auto-adaptive Pulse Repetition Frequency (PRF) technique is put forward to uniformly sample signal in azimuth direction. The computation load of the new PFA is merely left to azimuth chirp z-transforms (CZTs) and range fast Fourier transforms (FFTs) after dechirp processing and residual video phase (RVP) compensation. Two flight modes (ellipse trajectory mode and hyperbola trajectory mode) are analyzed. A lineal approximation method is proposed to simplify non-lineal sensor trajectory analysis. Computer simulation results for multiple point targets validate the presented approach. Comparison of computation load between this PFA and traditional PFA is represented in Appendix B.

In the present study, evaluation of L-band SAR data at different polarization combinations in linear, circular as well as hybrid polarimetric imaging modes for crop and other landuse classifications has been carried out. Full-polarimetric radar data contains all the scattering information for any arbitrary polarization state, hence data of any combination of transmit and receive polarizations can be synthesized, mathematically from full-polarimetric data. Circular and various modes of hybrid polarimetric data, (where the transmitter polarization is either circular or orientated at 45°, called π/4 and the receivers are at horizontal and vertical polarizations with respect to the radar line of sight) were synthesized (simulated) from ALOS-PALSAR full-polarimetric data of 14th December 2008 over central state farm central latitude and longitude 29°15'N/75°43'E and bounds for northwest corner is 29°24'N/75°37'E and southeast corner is 29°07'N/75°48'E in Hisar, Haryana (India). Supervised classification was conducted for crops and few other landuse classes based on ground truth measurements using maximum-likelihood distance measures derived from the complex Wishart distribution of SAR data at various polarization combinations. It has been observed that linear full-polarimetric data showed maximum classification accuracy (92%) followed by circular-full (89%) and circular-dual polarimetric data (87%), which was followed by hybrid polarimetric data (73-75%) and then linear dual polarimetric data (63-71%). Among the linear dual polarimetric data, co-polarization complex data showed better classification accuracy than the cross-polarization data. Also multi-date single polarization SAR data over central state farm during rabi (winter) season was analyzed and it was observed that single date full-polarimetric SAR data produced equally good classification result as the multi-date single polarization SAR data.

In this paper, the shooting and bouncing ray (SBR) method in combination with the truncated wedge incremental length diffraction coefficients (TW-ILDCs) is implemented on the heterogeneous CPU-GPU architecture to effectively solve the electromagnetic scattering problems. The SBR is mapped to the GPU because numerous independent ray tubes can make full use of the massively parallel resources on the GPU, while the TW-ILDCs are implemented on the CPU since they require complex and high-precision numerical calculation to get the accurate result. As the computation times of neighboring aspect angles are similar, a dynamic load adjustment method is presented to achieve reasonable load balancing between the CPU and GPU. Applications, including the radar cross section (RCS) prediction and inverse synthetic aperture radar (ISAR) imaging, demonstrate that the proposed method can greatly improve the computational efficiency by fully utilizing all available resources of the heterogeneous system.

A fast Inverse Polynomial Reconstruction Method (IPRM) is proposed to efficiently eliminate the Gibbs phenomenon in Fourier reconstruction of discontinuous functions. The framework of the fast IPRM is modified by reconstructing the function in discretized elements, then the Conformal Fourier Transform (CFT) and the Chirp Z-Transform (CZT) algorithms are applied to accelerate the evaluation of reconstruction coefficients. The memory cost of the fast IPRM is also significantly reduced, owing to the transformation matrix being discretized in the modified framework. The computation complexity and memory cost of the fast IPRM are O(MN log 2L) and O(MN), respectively, where L is the number of the discretized elements, M is the degree of polynomials for the reconstruction of each element, and N is the number of the Fourier series. Numerical results demonstrate that the fast IPRM method not only inherits the robustness of the Generalized IPRM (G-IPRM) method, but also significantly reduces the computation time and the memory cost. Therefore, the fast IPRM method is useful for the pseudospectral time domain methods and for the volume integral equation of the discontinuous material distributions.

An evolutionary learning algorithm based on differential evolution strategy (DES) and continuous ant colony optimization (CACO) for wideband antenna design is proposed. The advantages of this hybrid method are demonstrated with several mathematical functions and a linear array pattern synthesis. This method is applied to design an E-shaped wideband patch antenna, which achieves the impedance bandwidth 4.8 ~ 6.53 GHz. We compare the hybrid method with the traditional DES and CACO optimization algorithms, and the advantage of this hybrid method over the DES and the CACO is also demonstrated.

As wireless communication moves from long to short ranges with considerably lower antenna heights, the need to understand and be able to predict the impact of vegetation on coverage and quality of wireless services has become very important. This paper focuses on vegetation attenuation measurements for frequencies in the range 0.4-7.2 GHz in mango and oil palm plantations to evaluate vegetation attenuation models for application in wireless sensor network planning and deployment in precision agriculture. Although a number of models have been proposed and evaluated for specific frequencies, results show that these models do not perform well when applied to different vegetation types or at different frequencies. A global assessment of the models using a broad range of frequencies shows that the COST 235 model gives more consistent results when there is vegetation in the propagation path. For grid-like plantation, the study shows that the RET model provides the best prediction of path loss for measurements between two rows of trees. However, taking into account the limited number of parameter values available for the RET model and the potential inaccuracy that may results from the use of a wrong parameter value, a sub-optimal model which combines the ITUR model with ground reflection does offer a more consistent prediction. The differences in the average values of RMS error between RET, ITUR and free space loss models when combined with ground reflection is less than 1.6 dB.

The study on effects of microwave electromagnetic interference on CMOS RS flip-flops is reported in this paper. Using device simulation method, the relation between the susceptibility of CMOS RS flip-flops and microwave electromagnetic interference frequency as well as pulse width has been analyzed. It is found that the effects of microwave electromagnetic interference get suppressed gradually with increasing frequency. Furthermore, the interference power threshold is inversely proportional to the pulse width, and the interference energy threshold is directly proportional to the pulse width conversely. In addition, because of the difference in the structure of these two categories of CMOS RS flip-flops, they have different susceptibility to microwave electromagnetic interference.

The trapezoidal recursive convolution (TRC) finite-difference time-domain (FDTD) method is extended to study the bistatic scattering radar cross sections (RCS) of conductive targets covered with inhomogeneous, time-varying, magnetized plasma medium. The two-dimensional TRC-FDTD formulations for electromagnetic scattering of magnetized plasma are derived. Time-varying parabolic density profiles of plasma are assumed in this paper. The bistatic radar cross sections are calculated under different conditions using 2-D TE model for a conductive cylinder covered with magnetized plasma. The numerical results show that plasma cloaking system can successfully reduce the bistatic RCS, that the plasma stealth is effective, and that the appropriate parameters of plasma can enhance its effectiveness.

A multispectral 24 x 24 bolometric matrix structure of terahertz (THz) absorbers operating at 0.3-0.4 THz was proposed and experimentally investigated. Each pixel of the structure was implemented as a fragment of an ultra-thin metamaterial absorber. The matrix structure consisted of four types of pixels with nearly perfect absorptivity. Three pixels were at 0.30, 0.33, 0.36 THz respectively with identically oriented polarization sensitivity, and the fourth pixel was at 0.33 THz oriented with polarization sensitivity orthogonal to foregoing ones. The backside of the structure included a high-performance infrared emissive layer. Resonant absorption of THz radiation induced the structure heating and increasing IR emission from the emissive layer, which was henceforth detected by the IR camera. The terahertz imaging system, capable to operate in real time, with spectral and polarization discrimination was demonstrated. The experimental results showed good spectral and polarization resolution together with acceptable spatial resolution.

Spotlight SAR interferometry is an attractive option for high resolution mapping and monitoring. In this paper, the signal spectral characteristics and the interfeometric properties of spaceborne spotlight SAR are analyzed completely, and the effect of the azimuth-variant Doppler to spotlight SAR interferometry is studied. Moreover, a new coregistration algorithm, which contains coarse coregistration, azimuth spectral filter, and accurate coregistration with adaptive subspace projection, is proposed for spotlight SAR interferometry. The algorithm is validated with real data experiment.

This paper presents a new three-phase LC-ring voltage controlled oscillator (VCO) using the TSMC 0.18μm 1P6M CMOS process. The VCO consists of three single-ended complementary Colpitts VCOs coupled via a varactor ring. Tuning range of VCO is 0.59 GHz, from 8.22 GHz to 8.81 GHz, while the control voltage was tuned from 0 V to 1.1 V and the VCO core power consumption is 2.82 mW at the supply voltage of 1.1 V. The measured phase noise is -118.14 dBc/Hz at 1 MHz offset frequency from 8.40 GHz. The VCO occupies a chip area of 1.018×0.74 mm² and provides a figure of merit of -192.14 dBc/Hz.

A magnetically tunable passive narrow-band split-mode mm-wave phase shifter based on dielectric resonance in yttrium iron garnet (YIG) is investigated. The novelty here is the demonstration of a phase shifter in the frequency region between two split dielectric resonances in YIG. It is shown that, under certain conditions, the differential phase shift from the split modes add up, resulting in a larger phase shift than for a single mode phase shifter. Two prototype phase shifters operating in the U- and W-bands at frequencies much higher than ferromagnetic resonance (FMR) in YIG have been designed and characterized. Phase shifts up to 30° with low losses and acceptable standing wave ratio are obtained for moderate bias magnetic fields. Equivalent transmission-line model taking into account coupling between the split resonances is presented and there is reasonable agreement between theory and experiment for both insertion loss and differential phase shift. Suggestions on further improvements of prototype filter characteristics have been outlined.

An ultra-wideband (UWB) balanced bandpass filter (BPF) is proposed and designed using defected ground structures (DGSs). A multimode resonator on top layer with a coplanar waveguide on bottom layer is used to design a UWB BPF. U-shaped and H-shaped DGSs loaded with capacitor are used to design to provide common mode rejection within a lower band, while a set of dumbbell-shaped DGSs are utilized to provide common mode rejection within an upper-band. The proposed UWB balanced BPF shows the performance of good common mode rejection in and out of the UWB passband.

Tray-type quasi-optical (QO) power combiners are able to combine the high- and medium-output power of QO systems with the well-known advantages of pulsed ultra-wideband (UWB) systems. In this work, an alternative low-profile tray-type passive structure for 3 GHz-10 GHz power combining is proposed. The purpose of the proposed solution is to reduce the physical size with respect to other existing architectures by using hybrid coaxial lines. In spite of the reduced size, the structure maintains ultra-wideband operation and high combining efficiency, as proved through measurements. Therefore, the proposed structure is suitable for integration with monolithic microwave integrated circuit (MMIC) amplifiers for medium- and high-power generation, depending on the type of MMICs which are integrated into the passive combiner. Numerical analyses of the designed power combiner integrated with some MMIC amplifiers reveal its benefits in terms of increased output power and wider dynamic range compared to isolated MMICs.

In this work, a dual circular polarized steering antenna for satellite communications in X band is presented. The antenna consists of printed elements grouped in an array. This terminal works in a frequency band from 7.25 GHz up to 8.4 GHz (15% of bandwidth), where both bands, reception (RX) and transmission (TX) are included simultaneously and Left Handed Circular Polarization (LHCP) and Right Handed Circular Polarization (RHCP) are interchangeable. The antenna is compact, narrow bandwidth and reaches a gain of 16 dBi. It has the capability to steer in elevation to 45°, 75°, 105° and 135° electronically with a butler matrix and 360° in azimuth with a motorized junction.

An ANN-based small-signal equivalent circuit model for 130 nm MOSFET device is proposed in this paper. The proposed model combines the conventional small-signal equivalent circuit model and artificial neural networks (ANNs) to achieve higher accuracy. Good agreement is obtained between proposed model and measured results confirming the validity and effectiveness of proposed model.