Railway ground vibration and mitigation measures: benchmarking of best practices

Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their residents. Among the different sources, the one coming from the rail transit system will play a central concern in the following years due to its sustainability. Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry. This paper aims to describe and compare the different mitigation systems existing and reported in literature through a comprehensive state of the art analysis providing the performance of each measure. First, an introduction to the ground-borne vibration and noise generated from the wheel-rail contact and its propagation through the transmission path is presented. Then, the impact and the different ways of evaluating and assessing these effects are presented, and the insertion loss indicator is introduced. Next, the different mitigation measures at different levels (vehicle, track, transmission path and receiver) are discussed by describing their possible application and their efficiency in terms of insertion loss. Finally, a summary with inputs of how it is possible to address the future of mitigation systems is reported.

Terahertz meta-chip switch based on C-ring coupling

Terahertz switch is one of the key components of future communication, radar, and imaging systems. Limited by the strong electromagnetic coupling in subwavelength scale, the traditional terahertz switch is difficult to meet the increasing application requirements. In this paper, a parallel topology terahertz meta-chip switch based on the combination of equivalent circuit theory and electromagnetic coupling is proposed. The meta-chip is realized by adjusting the density of two-dimensional electron gas of InP-HEMT, which converts the electromagnetic coupling between the microstructure and microstrips. By using the 90 nm gate length InP-HEMT process, a C-ring loaded meta-chip is fabricated and tested in this paper. The results show an insertion loss lower than 1 dB with a 10 dB switching ratio, which is 20% higher than that without C-ring while ensuring the rather low insertion loss. It shows that the presented mechanism has positive significance for the design of terahertz band functional devices.

USE OF THE FAN-SHAPED IDTS – EFFICIENT METHOD FOR CREATING THE WIDEBAND SAW FILTERS WITH A LOW INSERTION LOSS AND HIGH RECTANGULARITY OF FREQUENCY RESPONSE

This paper presents an efficient method for creating the wideband SAW filters with high rectangularity, flat amplitude response and low insertion loss in passband – use of fan-shaped IDTs with inclined electrodes. The authors consider the approaches for realization of the fan-shaped filters. The quantitative and qualitative characteristics of the fan-shaped SAW filters with a relative bandwidth ∆f/f0 = 4–75 %, shape factor 1,1–1,96 and insertion loss of 5–18 dB are given for each approach.

Application of Ni-doped ZnO nanorods in surface acoustic wave ultraviolet photodetectors

A surface acoustic wave ultraviolet photodetector was fabricated on a ZnO thin film with pure and Ni-doped ZnO nanorods deposited on a Si substrate. Piezoelectric ZnO thin films were grown on Si through radio-frequency magnetron sputtering, and ZnO nanorods were synthesized on ZnO thin films by using the hydrothermal method. The crystalline structure, surface morphology, and luminescent characteristics of ZnO films and nanorods were examined using X-ray diffraction and photoluminescence spectrometers and scanning electron microscope. The performance of the surface acoustic wave photodetector was evaluated using the variations in surface capacitance, insertion loss, and phase shift. ZnO nanorods became shorter and thicker with an increase in the concentration of Ni doping; however, the variations in surface capacitance of Ni-doped ZnO nanorods were greater than those of pure ZnO nanorods obtained under ultraviolet irradiation. Devices with Ni-doped ZnO nanorods exhibited larger shifts in insertion loss and phase than those with pure ZnO nanorods did.

Multilayer metallic filters for Q/V band IMUX

Current designs of space IMUX filters are based on dual-mode circular waveguide cavities, on dielectric resonators or, at the lower end of the frequency spectrum, on coaxial resonators. This paper presents a new kind of IMUX filter aimed at high operating frequencies (Ka, Q, and V bands) which was developed in the frame of an ESA funded study named KALOS-DEVAQ. The new filter implements a quasi-elliptic frequency response and is characterized by simple geometry. The mechanical structure is composed of stacked metallic plates and it is well suited to be manufactured, at a low cost, with high accuracy. Despite the lower unloaded Q factor, the new configuration allows achieving a comparable flatness of insertion loss and group delay, thanks to the application of the pre-distortion technique. The increased insertion loss does not affect the system performances because it can be compensated by the amplification stages in the RF chain.

PENGARUH PERUBAHAN DIMENSI TERHADAP NILAI ISOLASI PADA BRANCH LINE COUPLER

Luasnya perairan nasional menjadi tantangan tersendiri bagi pemerintah dalam upaya pengamanan wilayah laut dari tindakan pelanggaran hukum. Indonesia perlu mengawasi betul-betul wilayah yang paling rawan agar sumber daya ikan nasional bisa dinikmati oleh masyarakat. Caranya, pangkalan bagi kapal-kapal pengawas (KKP, Bakamla, TNI AL) perlu dibangun di wilayah tersebut. Salah satu upaya yang perlu dilakukan yaitu peningkatan pengawasan secara ketat pemerintah dengan cara meningkatkan keamanan sekaligus menyusun aturan yang tepat agar bisa mencegah terjadinya pelanggaran hukum. kemampuan TNI AL dan Polri untuk menjaga seluruh wilayah laut, maka mereka harus menggunakan radar pengawas pantai. Radar pulsa ini mempunyai gelombang elektromagnetik yang diputus secara berirama, dan hanya memiliki satu antena yang digunakan untuk mengirim dan menerima sinyal. Untuk mengirim dan menerima sinyal, radar ini membutuhkan pemisah yang disebut duplekser. Duplekser berfungsi untuk mengisolasi sinyal yang ditransmisikan dan sinyal yang diterima dan komponen utama dari duplexer adalah Branch-Line Hybrid Coupler. Coupler memiliki parameter yang menunjukkan kinerja seperti: Return Loss, Power Coupling, Insertion Loss dan nilai isolasi. Dalam penelitian ini dilakukan penelitian untuk mengetahui pengaruh perubahan dimensi terhadap nilai isolasi pada Branch line coupler. Isolasi sangat penting karena mempengaruhi kinerja duplekser. Nilai yang lebih kecil semakin baik kinerja duplekser tersebut. Penelitian ini dilakukan dengan memodifikasi panjang dan lebar saluran impedansi Coupler. Branch-Line Coupler dirancang dalam bentuk mikrostrip dan difabrikasi menggunakan substrat FR-4 yang memiliki konstanta dielektrik 4,6, tebal 1,3 mm, dan frekuensi operasi 3 GHz. Untuk mendapatkan nilai optimasi karakteristik isolasi, kanal impedansi harus dimodifikasi, yaitu panjang dan lebar seri lengan (Z0 = 50 ), panjang dan lebar seri lengan (Z0 = 35,35 ), dan panjang dan lebar lengan shunt (Z0 = 50 ). Hasil optimasi isolasi didapatkan -67.786 dB.

Directivity Enhancement in Non-Reciprocal Bandpass Filters using an Evolutionary Algorithm

In this letter, a non-reciprocal filter with enhanced directivity is analyzed methodically and the filter parameters are optimized using an evolutionary algorithm. The return loss, insertion loss, and isolation characteristics of the filter exhibit a trade-off that makes manual tuning a trial-and-error method. The veracity of the numerical modeling is conformed by designing a 150 MHz lumped element non-reciprocal bandpass filter based on the parameters extracted using an evolutionary algorithm based particle swarm optimization (PSO). The simulated and measured results comply well with the modeling and the results exhibit maximum directivity of 28.2 dB without degradation in insertion loss (1.1 dB) and return loss (16.2 dB) within the passband. The algorithm can be utilized in designing non-reciprocal filters having different center frequencies and bandwidths.

Directivity Enhancement in Non-Reciprocal Bandpass Filters using an Evolutionary Algorithm

In this letter, a non-reciprocal filter with enhanced directivity is analyzed methodically and the filter parameters are optimized using an evolutionary algorithm. The return loss, insertion loss, and isolation characteristics of the filter exhibit a trade-off that makes manual tuning a trial-and-error method. The veracity of the numerical modeling is conformed by designing a 150 MHz lumped element non-reciprocal bandpass filter based on the parameters extracted using an evolutionary algorithm based particle swarm optimization (PSO). The simulated and measured results comply well with the modeling and the results exhibit maximum directivity of 28.2 dB without degradation in insertion loss (1.1 dB) and return loss (16.2 dB) within the passband. The algorithm can be utilized in designing non-reciprocal filters having different center frequencies and bandwidths.