• Journal of Advanced Navigation Technology
• /
• v.13 no.4
• /
• pp.475-481
• /
• 2009

This paper focuses the performance improvement of the train radio system (TRS) supporting the safe and accurate operations. The causes of troubles and the performance drift in TRS have been analyzed and measurement indexes have been selected. Frequency shifts of transmitters causing from train vibrations have been shown, and the improvement of frequency stability has been confirmed by use of vibration- proof pads.

• Journal of Digital Convergence
• /
• v.12 no.12
• /
• pp.257-264
• /
• 2014

Through MCU model, Radio Frequency communication is completed using universal asynchronous receiver and transmitter. The communicatin with PC and MCU is completed using RS-232 cable. At first interconnected communication with PC and MCU is necessary for RF communication because tha UART is based technique for RF communication. Program imbeded in microcontroller unit is ran during RF signal is transmitted to other RF module. Data connected with PC and MCU is transmitted between PC and MCU during PC and MCU is connected.

• Journal of Communications and Networks
• /
• v.15 no.6
• /
• pp.576-580
• /
• 2013

In this paper, we investigate the capacity of a multipoint-to-point cognitive radio network. In existing works, the asymptotic capacity is only obtained in the high peak power region at secondary transmitter (ST) or obtained without considering the interference from primary transmitter (PT) for easy analysis. Here, we analyze the asymptotic capacity by considering an arbitrary peak power at the ST and the interference from the PT based on extreme value theory. Simulation results show that our approximated capacity is well-matched to the exact capacity. Furthermore, the scaling law of our capacity is found to be double logarithm of the number of secondary users.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.5
• /
• pp.55-59
• /
• 2014

Multi-band and multi-mode transmitters are needed for SDR and CR. Recently many types of polar transmitters have been studied in order to implement a multi-band and multi-mode transmitter. Polar transmitters have many advantages, such as a simple structure, high efficiency and etc. In this paper we consider the number of D/A bit and the effects of a delay mismatch as design parameters for implementing polar transmitters. From the simulation we know that a 10 bit D/A is sufficient and a delay mismatch must be maintained small than 1/64 chip for satisfying the spectrum mask characteristics. We implement a polar transmitter based on the design parameters and the measured output signal meet the spectrum mask of 800MHz CDMA.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.44 no.4 s.316
• /
• pp.45-49
• /
• 2007

The isolation between transmitter and receiver has been a critical problem in a pulse-modulated RFID (Radio Frequency Identification) system where transmitter and receiver use the identical frequency. A method using a switch, a mixer, a BPF (band-pass filter), and an additional oscillator in the transmitter is proposed to improve the isolation between transmitter and receiver in an RFID system. The Proposed system up-converts the outgoing wave from a frequency different from the received signal and improves the isolation. The proposed method provided additional 20 dB improvement on the isolation.

• Journal of IKEEE
• /
• v.20 no.1
• /
• pp.54-60
• /
• 2016

In this paper, out-of-band emission regulations and measurement methods of terrestrial DTV broadcasting services are analyzed, and a novel method to evaluate the out-of-band emission characteristics of DTV transmitter is proposed. Experimental results show that proposed method can be easily used to measure the characteristics of DTV transmitter with inexpensive measuring equipments. With a few modifications, proposed method can be widely adopted to measure the RF performances of the general radio equipments efficiently.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.2
• /
• pp.271-279
• /
• 2008

In this paper, we investigate interference between short-range radiocommunication devices(SRDs) with frequency hopping spread spectrum(FHSS) and direct sequence spread spectrum(DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-carlo(MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space. The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate(BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than band-width does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

• Journal of Broadcast Engineering
• /
• v.12 no.3
• /
• pp.266-277
• /
• 2007

Recently, Transmitter Identification(TxID) technology has been issued as a technology of ATSC DTV. ATSC DTV networks are comprised of a plurality of transmitters, broadcasting the same signal sing one frequency network(SFN) connected to EDOCR. In this single frequency network, TxID technology has been recognized as a technology in the ATSC DTV system since it enables the broadcast authorities and classify multiple transmitters. However, conventional TxID uses extremely long spreading sequence to identifying transmitters, so it increases H/W complexity and registers. Thus, to solve those hardware problems, we propose an efficient signal processing technology using decimation algorithm. Furthermore, we certified the availability of the proposed algorithm via various simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.2
• /
• pp.43-48
• /
• 2011

Cognitive radio is accepted as an effective and promising approach for resolving the spectrum scarcity problem by allowing secondary users to borrow unused spectrum from primary users. A method of identifying busy and empty spectrum at the given time and space, which is called spectrum sensing, constitutes an essential element of the cognitive radio. In this paper, we propose a receiver-centric spectrum sensing scheme which attempts to detect the primary receiver rather than the primary transmitter. It is shown that the proposed receiver-centric sensing approach results in more efficient spectrum utilization than the conventional transmitter-centric sensing.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.1
• /
• pp.10-18
• /
• 2010

The polar transmitter is applied to the narrowband communication systems such as GSM (Global System for Mobile Communications), EDGE (Enhanced Data Rates for GSM Evolution), and GPRS (General Packet Radio Service). To apply polar transmitter for the wideband communication like OFDM (Orthogonal Frequency Division Multiplexing) where the high PAPR (Peak-to-Average Power Ratio) problem occurs, this paper proposes a windowed-sinc function based PAPR reduction scheme. The proposed algorithm mitigates the effect of excessive suppression due to successive peaks or relatively high peaks of the signal. The BER (Bit Error Rate) and EVM (Error Vector Magnitude) performances are measured for various window types and lengths. The simulation results demonstrate that the proposed algorithm achieves significant improvement in terms of BER and PAPR reduction performance with similar spectrum performance to the conventional peak windowing scheme.