A large deployable reflector antenna is considered and designed for the application of a synthetic aperture radar (SAR) system requiring high gain for the high resolution of a detected image within a distance of a few hundred kilometers. For its lightweight and strong characteristics, carbon fiber reinforced polymer (CFRP), is introduced as a composite material and fabricated for conductivity evaluation. Effective electrical characteristics are obtained as a function of carbon fiber direction, using measured S-parameters in a rectangular waveguide. By taking into account the changes of the effective electrical characteristics that depend on the fiber direction of reflector antenna, the radiation pattern is investigated at X-band in terms of gain and polarization variation effects. The proposed reflector antenna made of quasi isotropic (QI) CFRP panel can realize the insensitive characteristics depending on the incident polarization.

Design formulas for the asymmetric coupled-section Marchand balun are derived. The characteristic impedance, port impedance and electrical length of asymmetrical coupled transmission lines across two layers comprise the design formulas for designing the Marchand balun. A Marchand balun is realized based on the deduced design formulas using two identical asymmetrical coupled transmission lines fabricated across two layers. The conventional approach for designing the Marchand balun exploits the coupling coefficients of coupled transmission lines, and then provides ranges for their characteristic impedances which may but lead to inaccurate design. More accurate design method is established using the design formulas derived without using the coupling coefficients of coupled transmission lines. One example to verify the derived design formulas is taken and fabricated, showing measurement results of bandwidth from 0.62 to 1.44 GHz with the return loss of more than 10 dB, where S21 and S31 show better than -4 dB. Over these frequencies the measurement results show the phase and amplitude imbalances of ±2 ^° and 0.2 dB, respectively.

In this paper, we propose a theoretical approach to estimate the power level of electromagnetic waves radiated into a structure by a specific external source. The target structure is a multistory building on a university campus that is used primarily for academic purposes and is much larger than the target wavelength. To verify the accuracy and efficiency of the proposed theoretical approach, measurements were carried out and a commercially available simulation tool, Wireless Insite, was adopted. We then analyzed the influence of an area of vegetation as an external environmental factor that could affect the radiated electromagnetic waves because of its location in front of the target structure. For this, a precise simulation environment was designed to derive the quantitative values of the electromagnetic attenuation caused by the external environmental factor. Furthermore, those values were applied to the theoretical approach. The results of the theoretical approach accounting for the external environmental factor were similar to those of the actual measured results. The results were also similar to those of the simulation tool, Wireless Insite, but the theoretical approach provided more efficient analysis results in terms of time consumption and computer resources.

In this paper, electromagnetic wave analysis was performed efficiently in a large structure using the theoretical method. While taking into consideration the important assumptions of the employed theoretical method, we created an environment for measurement and simulation. A shield room with an aperture was selected as the target structure, and a measurement system based on frequency domain was constructed and used. Using the simulation tool, Wireless Insite, electromagnetic wave analysis was performed by modeling the measurement environment. To verify the efficiency and accuracy of the theoretical method, the results of the actual measurement, the commercially available simulation tool, and the theoretical method were compared. These results showed that the theoretical method can be more efficiently interpreted than the commercially available simulation tool in an electrically large structure.

Efficient earth observation using spaceborne synthetic aperture radar (SAR) requires the analysis of high-resolution wide-swath (HRWS) systems, which have a fine resolution and a short revisit time through wide-area observation, and quadrature-polarimetric (quad-pol) systems, which can obtain a quad-pol image and have many applications. The operational method of SAR generally affects system performance involving the system parameters and antenna patterns, and thus analyzing HRWS quad-pol SAR systems is essential to the system design. In this paper, an extension of the modified SweepSAR technique to a quad-pol observation scenario is performed and a comparison to ScanSAR and conventional SweepSAR is provided for a simulated scenario. On the basis of the system requirements, we selected the optimal parameters and designed a reflector antenna suitable for a wide-swath quad-pol SAR system. As a result of comparing the wide-swath quad-pol SAR operation modes, the modified SweepSAR mode demonstrated advantages in terms of system performance, such as the ambiguity ratio and swath width, and reflector antenna design for a spaceborne SAR system.

The power divider/combiner is very important component for power amplifier design in low power MMIC design and high power system using hybrid scheme. In addition to that, the power divider/combiner is applied for impedance matching, antenna polarization, and phase control in phased array antenna. In this paper, we will consider the power divider/combiner working at two arbitrary frequencies with different power ratios at two output ports including a rigorous analysis and simulation. In order to determine the optimized design parameters, the even-odd mode analysis is carried out rigorously using impedance matching condition and lumped components such as R, L, and C. The validation of analysis and design parameters can be verified using two commercially available softwares based on circuit theory and FIT algorithm, respectively.