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A band-pass filter (BPF) is an essential part of a wireless communication system as it functions to reduce interference and noise. Many structures have been proposed to achieve a high-quality BPF. Typically, these structures utilize vias. However, vias has several drawbacks, including impedance discontinuities, increased resistance values, and complex structures. In this study, we propose a dual-band BPF based on a cascaded closed ring resonator (CCRR) without using vias. Specifically, the proposed structure consists of multiple CCRRs connected at the corner pattern and incorporates capacitive coupling to the input impedance. Additionally, the CCRR configuration has dual sizing to achieve dual-band performance. Subsequently, the proposed BPF is simulated and fabricated using Duroid Rogers RT 5880 with dielectric constant εr = 2.2, dissipation factor tan δ = 0.0009, and thickness h = 1.575 mm. The measurement results demonstrated that the dual-band BPF operated at a resonant frequency of 2.50 GHz with a transmission coefficient (S21) value of -2.18 dB in the first band. In the second band, a resonant frequency of 3.70 GHz was obtained with an S21 value of -1.43 dB. The bandwidth in the first band was 160 MHz, and in the second band, it was 110 MHz. Moreover, based on the measurement results, the reflection coefficient (S11) in the first band was -11.05 dB, while in the second band, it was -23.3 dB. The excellent agreement between the simulation and measurement validates the proposed method.

Collision is the main issue in safe transportation, including in the railway system. Sensor systems have been developed to detect obstacles to prevent a collision, such as using cameras. One disadvantage of the camera systems is that performance detection decreases in a not clean environment, like the target position behind the fogs. This paper discusses the development of frequency modulated continuous wave (FMCW) radar signal processing for high-speed railway collision avoidance. The development of radar signal processing combines a two-dimensional constant false alarm rate (2D-CFAR) and robust principal component analysis (RPCA) to detect moving targets under clutter. Cell average (CA) and Greatest of CA (GOCA) CFAR are evaluated under a cluttered wall environment along the railway track. From the experiment, the development of FMCW radar can detect stationary or moving obstacles around 675 meters in front of the locomotive. Combining 2D-CFAR and RPCA algorithm outperforms average background subtraction in extracting moving targets from strong clutter signals along the railway track.

Microwave imaging, such as images for radiological inspection in the medical profession, is one of the applications utilized in ultra-wideband (UWB) frequency ranges. The Vivaldi antenna is one of the most popular antennas for this purpose. The antenna is utilized because of its simple, lightweight, and compact design, as well as its excellent efficiency and gain capabilities. In this work, we present a high-gain Vivaldi antenna for microwave imaging applications. The proposed Vivaldi antenna is designed using a double-slot structure method with the addition of corrugated edges and a semicircle director aimed at improving the gain. The antenna is designed to operate at frequencies ranging from 3.1 to 10.6 GHz. Based on the modeling findings, the suggested antenna attain a bandwidth of 7.5 GHz with operating frequencies from 3.1 GHz to 10.6 GHz for a VSWR of less than two. In comparison to a typical single slot antenna, the suggested antenna provides a substantial boost in gain performance. The increase in gain is proportional to the frequency of operation. The constructed antenna has a lower bandwidth than the simulated one, with operating frequencies of 3.5 GHz – 3.75 GHz and 4.25 – 10.89 GHz, respectively, and useable bandwidths of 250 MHz and 6.64 GHz. All these results suggest that the antenna is suitable for microwave imaging applications.

This paper presents the design, simulation, realization and analysis of flexible microstrip patch antenna for S-band applications. The proposed design also adopts the conformal structure by utilizing flexible substrate. Conformal or flexible structure allows the antenna to fit with any specified shape as desired. The antenna patch dimensions is 43 mm × 25 mm without SMA connector. The patch is etched on the flexible dielectric substrate, pyralux FR 9111, with a relative dielectric constant of εr = 3 and the thickness of substrate, h = 0.025 mm. The antenna is designed to resonate at 3.2 GHz. The return loss (RL) of the simulation is -35.80 dB at the center frequency of 3.2 GHz. The fabricated antenna prototype was measured at different bending angles scenarios including 0º, 30º, 60º, and 90º. The measurement of antenna prototype shows that the center frequency is shifted to the higher frequency of 3.29 GHz, compared to the simulation result. Among these scenarios, measurement at bending angle of 90º gives the best performance with RL = - 31.38 dB at 3.29 GHz, the bandwidth is 80 MHz, and the impedance ZA = 48.36 + j2.04 Ω. Despite a slight differences from simulation results, the designed antenna still performs well as expected.

This article proposes a reconfigurable low-profile monopolar antenna with triple-band independent tuning capability. The antenna is based on the concept of a center-fed patch with shortings to achieve omnidirectional radiation patterns. Instead of using vias, varactor-loaded stubs are utilized to create reconfigurable equivalent shorting points. The triple bands can be achieved by using three sets of stubs. This configuration results in three magnetic current loops that spatially overlap at different independently tunable frequencies. Measurement results show that the design obtains three independent tunable frequencies centered at 2.51, 3.56, and 4.62 GHz with -10 dB relative tuning ranges of 22.8%, 22.8%, and 16.7%, respectively. The antenna radiates omnidirectionally with vertical polarization in the three sweeping bands. The proposed concept can be extended to a larger number of bands by adding sets of stubs with considerations of coupling and impedance matching.

In this paper, the microstrip planar fourtear antenna that operate at frequency range 2300 – 2500 MHz was investigated, Some applications suitable to operate in this frequency are WiMAX at 2.3 and 2.5 GHz and WLAN at 2.4 GHz. Simulations performed with the aid of Finite Element Emthod (FEM) based software which can calculte and comply the appropriate design to be able to operate at the desired working frequency. The analyzed parameters include : SWR, impedance, return loss, radiation patterns, gain, and polarization. From the measurement, bandwidth obtained is equal to 7.69% in the frequency range of 2318,250-2500 MHz in VSWR < 2. Radiation pattern measurement was unidirectional and the polarization was elliptical.

In this paper, design and realization of FIR filter with a bandwidth of 40 MHz at 50-90 MHz frequency has been proposed. The design was destined to be implemented on the Inter Satellite Links (ISL). This kind of filter had been selected due to a need in linear phase responseon the ISL data communication. Equiripple method was used to design the filter becauseof its reliability in minimizing the magnitude errors. The design of this FIR filter was conducted with theoretical calculation and simulation using the R2012b Matlab. For the implementation, FPGA was used with a VHDL as the programming language with a help of Xilinx ISE Design Suite 14.5. Simulation results in Matlab and Simulink indicated that the filter design could be well implemented on ISL at frequency of 50 MHz - 90 MHz with stopband of 60 db. The phase responseresult of the realized design is quite linear so that the filter is suitable for data communication on the ISL.