AbstrakRadar penembus dinding memiliki potensi untuk dapat digunakan dalam penanganan pasca bencana dan gangguan keamanan.Tulisan ini membahas hasil perancangan dan pembuatan sistem Radar Penembus Dinding Ultra Wide Band Frequency Modulated Continous Wave (UWB-FMCW) yang digunakan untuk mendeteksi keberadaan suatu objek di balik dinding. Dalam penelitian ini dikembangkan pembangkit chirp UWB menggunakan kombinasi DDS dan VCO sebagai komponen utama pembangkit gelombang FMCW untuk mendapatkan linearitas yang tinggi, merealisasikan tranceiver dalam arsitektur homodyne, mengembangkan modul akuisisi, serta merealisasikan perangkat lunak untuk melakukan pengolahan sinyal dan menampilkannya dalam bentuk citra secara real time menggunakan MS Visual C++. Sistem radar penembus dinding didesain untuk memiliki resolusi 6 cm dan jarak tidak ambigu 30 m, pada rentang pita frekuensi kerja 500 -3000 MHz. Dari hasil pengujian dalam skala laboratorium radar ini mampu melakukan identifikasi objek dibalik dinding yang terbuat dari kayu setebal 3 cm pada jarak 4 m dan menampilkannya dalam bentuk citra A-Scan dan B-Scan secara real time.Kata kunci: radar, penembus dinding, pembangkit chirp UWB, akuisisi data berkecepatan tinggi, deteksi objek, FMCW. AbstractThe through-wall radar has the potential to be used in post-disaster and security disturbances. This study aims to design and realize the through wall radar system based on Ultra Wide Band and Frequency Modulated Continuous Wave (FMCW-UWB) technology to detect an object behind the wall. In this study, we develop an UWB Chirp using DDS and VCO as a main component to obtain FM linearity, realizing transceiver in homodyne architecture, develop a data acquisition module using USB interface, as well as the realization of the software to perform signal processing and displays the image in real time in the form of using MS Visual C++. The through wall radar system is designed to have a resolution of 6 cm and unambiguous distance of 30 m, in the range of working frequency band 500-3000MHz. Based on the laboratory test result, the designed radar is able to identify objects behind 3cm thick wood walls at a distance of 4m and displays the image in the form of A-Scan and B-Scan in real time.
AbstrakDuplekser merupakan perangkat yang dapat mengisolasi receiver dari transmitter saat keduanya saling berbagi antena yang sama, digunakan agar komunikasi bisa berjalan secara full duplex. Ada dua metode transmisi duplex yaitu frequency division duplex (FDD) dan time division duplex (TDD). FDD merupakan teknik duplex yang menggunakan dua frekuensi yang berbeda untuk melakukan komunikasi dalam dua arah, sedangkan TDD menggunakan frekuensi tunggal dan frekuensi tersebut digunakan oleh semua kanal untuk melakukan pengiriman dan penerimaan data.Gabungan dua bandpass filter dengan metoda pseudo-interdigital untuk aplikasi LTE (long term evolution). Metode ini lebih unggul dibandingkan duplekser dengan metoda hybrid. Duplekser bekerja pada FDD LTE band ke-7 yaitu frekuensi uplink 2500-2570 MHz dan downlink 2620-2690 MHz. Dari hasil pengukuran diperoleh sebagai berikut: nilai frekuensi center pada uplink 2639 MHz dan pada downlink 2659 MHz, insertion loss pada uplink 1,561 dB dan downlink 1,74 dB, bandwidth ±70 MHz, isolasi 23,03 dB, serta nilai return loss 23,5 dB pada uplink dan downlink 23,45 dB.Kata kunci: duplekser, FDD (frequency division duplex), uplink, downlink, LTE (long term evolution), pseudo-interdigital. AbstractDuplexer is a device that can isolate the receiver from the transmitter while both share the same antenna, it is used so that communication can be run in full duplex. There are two methods of transmitting duplex, i.e. frequency division duplex (FDD) and time division duplex (TDD). Duplex FDD is a technique that uses two different frequencies for communication in both directions, while TDD uses a single frequency and the frequency is used by all channels for sending and receiving data.A combination of two bandpass filters with the method for application Pseudo-Interdigital LTE (long term evolution). This method is superior to the hybrid duplexer method. Duplexer LTE FDD band worked on the 7th the uplink frequency 2500-2570 MHz and 2620-2690 MHz downlink. From the measurement results, it is obtained as follows: the value of the center frequency of 2639 MHz uplink and 2659 MHz downlink, insertion loss in 1.561 dB uplink and 1.74 dB downlink, ± 70 MHz bandwidth, isolation 23.03 dB, and return loss of 23.5 dB and 23.45 dB on uplink and downlink respectively.
A novel method for eliminating noise from a noised speech signal in order to improve its quality using combined power spectral subtraction and multi-layer perceptron network is presented in this paper. Firstly, the contaminated speech signal was processed by spectral subtraction to enhance the clean speech signal. Then, the signal was processed by a neural network using the spectral subtraction parameters and result of estimated speech signal in order to improve its signal quality and intelligibility. IntroductionThe speech enhancement is an important tool for supporting many applications especially in the telecommunication areas such as in the mobile communication. Others, this capability has direct influences to the performance of the human-machine interface applications such as speech recognition and speaker recognition which are very popular currently. In many situations, the high level noise degrading speech signal can decrease the performance of those applications. Moreover, it degrades the speech quality and intelligibility, and also affects negatively to the listener's perception especially in mobile communication cases [1]. This is the main problem of the speech enhancement which almost all of these speech enhancement approaches rely on the estimation of a short-time spectral gain [2].There are several types of speech enhancement algorithm investigated by researchers over the world which can be separated to two groups e.g. single channel and multichannel speech method. Based on several researches, the multi-channel speech enhancement has better performance than single channel methods. However, because of its simplicity and low cost implementation, the single channel method is still worthy to be explored and improved. The most popular single channel speech enhancement method is spectral subtraction.Spectral subtraction is well known noise reduction method and it is one of the first algorithms for speech enhancement facing musical noise. Firstly, it was investigated by Boll in 1979 [3]. In its first method, spectral subtraction is purposed for eliminating musical noise. In the same year, the spectral subtraction was improved by Berouti in 1979 [4]. He developed an oversubtraction constant for over-estimating the noised speech signal. Although the development of spectral subtraction has been begun since 1979, this method has been used in many applications until now because it is relatively inexpensive in computation [5]. However, spectral subtraction suffers from a problem of introducing artifacts like noise while removing residual noise. It then will influence to the both quality and intelligibility of estimated speech signal. Hence, current researches on spectral subtraction techniques are concentrated on decreasing or removing this noise. [6]
The effect of Ti2+-Mn4+substitution on microwave absorption has been studied for BaFe12-2xTixMnxO19 ferrite, where x varies from 0.2, 0.4, 0.6 and 0.8.Ti2+-Mn4+ ions were obtained from TiO and MnO2 precursors which were mechanically alloyed together with BaCO3 and Fe2O3 precursors. X-ray diffraction (XRD) patterns for sintered samples confirmed that the materials are consisted with single phase BHF structure. Unit cell volume and crystallite size was found increase with increasing x. Crystallite size for all samples below 70 nm, but the grain morphology shown that the grains is in range of 200 - 400 nm, which concluded that each grain are polycrystalline. The saturation magnetization is increases up to x = 0.4 and decrease for higher x values, while the coercivity remains decreases monotonically. These results were interpreted in terms of the site preferential occupation of Ti2+ and Mn4+ at low level substitution.These substitution revealed of enhanced reflection loss (RL) up to 25 dB forx=0.6.It suggested that the synthesized can be employed as effective microwave absorbers in various devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.