• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1151-1156
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• 2012

In this paper, the baseband filter is proposed in order to maintain a constant sensitivity regardless of distances for 77 GHz automotive radar system. Using existing DCOC loop circuit can remove DC offset and also cancel differences of received power depending on the distance. Measured results show that the maximum gain is 51 dB and high pass cutoff frequency can be tuned from 5 kHz to 15 kHz. The slope of high pass filter can be tuned from -10 to -40 dB/decade for the distance compensation. The measured NF and IIP3 are 26 dB and +4.5 dBm with 4.3 mA at 1.0 V supply voltage, respectively. The fabricated die size $500{\mu}m{\times}1,050{\mu}m$ excluding the in/out pads.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.158-162
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• 2012

In this paper, we propose a wireless modem, which used OFDM/64QAM method and the ISM band with 2.4GHz radio frequency. In this paper proposed the case of a modem, the main program to process the baseband processor, processing speed, operating voltage, and reliability should be ensured. So we have designed with Ralink's RT2870, witch was used for Wi-Fi solution. The RT2870 provides full support for wireless LAN standard, and supports various modulation formats, 2.4GHz and 5GHz bands, both of which support chip. In this paper, we also output the modulated signal transmitted wirelessly to the 2.4GHz band RF RT2850 chip processing was applied and using 40MHz band 2.422 ~ 2.462GHz wireless bands were designed to occupy. By applying bi-directional transmission between wireless transmitter and receiver, it can be effectively connected with any kinds of wireless LAN with 2.4GHz ISM band. Therefore it could economically be used as peripheral equipments for POS system or personal wireless device based on Android platform.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.1
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• pp.18-27
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• 2004

In this paper, we presents an analytical simulation procedure for evaluation in baseband digital modulated signals distortions in the present of RF power amplifier(SSPA) nonlinear behavior and backoff operations of OFDM wireless transmission system. we obtained the optimum nonlinear transfer function of designed SSPA with the SiGe HBT bias currents of OFDM multi-channel wireless transmission system and compared this transfer function to SSPA nonlinear modeling functions mathematically, we finds optimum bias conditions of designed SSPA. With the derived nonlinear modeling function of SSPA, We analysed the PSD characteristics of in-band and out-band output powers of SSPA EVM measurement results of distorted constellation signals with the input power levels of SSPA. The results of paper can be applied to find the SSPA linearly with optimum bias currents and determine the SSPA input backoff bias for AGC control circuits of SSPA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.69-72
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• 2012

In the bandpass sampling(BPS), the sampling frequency is lower than the frequency of the RF(radio frequency) signal being sampled. In this method, the baseband spectrum directly appears by the sampling itself, so that it is not necessary to use any down converter, making the receiver's hardware simpler. The second-order BPS uses two identical BPS samplers operating with an offset timing to each other. By a processing with their two sampled signals, it can be possible to cancel the aliasing or interference component if any due to the bandpass sampling. The interpolant filter, which is to manipulate the phase characteristics of the sampled signal, affects the performance of the cancellation. In this paper, a multiband interpolant filter is introduced, with which multiple interference signals from multiple RF bands can be cancelled simultaneously. We suggest several phase characteristics for the interpolant filter and have evaluated their performances through computer simulations. It has been shown that the filter with a continuous phase function gives the better performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1876-1882
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• 1999

In this paper, we have proposed a FCB detection algorithm for the GSM system which is european cellular standard. The detection algorithm can be implemented using received signal sampler, correlator, and post detection combiner. GSM mobile phone can use the proposed algorithm for detection of the Broadcasting Channel, and to obtain the initial timing estimate. The proposed algorithm has a architecture which is suitable for DSP or ASIC implementation, and required memory size is small. The performance of the algorithm is a function of the processing data window size and the threshold values. Proper window size and the threshold values can be determined by analyzing the correlator and combiner. The proposed algorithm has been implemented using DSP, and the performance was verified using baseband simulation. The simulation assumed frequency offset values of 0ppm and 15ppm with the receiver filter bandwidth set at both minimum and maximum. It is shown that the algorithm is robust under various assumptions, and suitable for real implementations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9C
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• pp.729-734
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• 2010

In the initial stage of the communications between a base station and a satellite transponder, the base station transmits the frequency-sweeping un-modulated up-link carrier within a certain frequency range to acquire the doppler frequency shift and signal power between the base station and the satellite in orbital flight. The satellite transponder acquires and tracks the carrier in order to initialize the communication. To control such initialization process, the satellite receiver should analyze the input carrier signal in various ways. This paper presents an SNR estimation algorithm to control the initialization process. The proposed algorithm converts the input signal into the baseband polar coordinate representation and estimates the SNR via the statistics of the angular signal components as well as the status parameters to control the receiver. The Monte-Carlo simulations shows the validity of the estimation proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.806-813
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• 2009

This paper presents a modem chip design for high-speed wireless communications. Among the high-speed communication technologies, we design the UWB (Ultra-Wideband) modem SoC (System-on-Chip) Chip based on a MB-OFDM scheme which uses wide frequency band and gives low frequency interference to other communication services. The baseband system of the modem SoC chip is designed according to the standard document published by WiMedia. The SoC chip consists of FFT/IFFT (Fast Fourier Transform/Inverse Fast Fourier Transform), transmitter, receiver, symbol synchronizer, frequency offset estimator, Viterbi decoder, and other receiving parts. The chip is designed using 90nm CMOS (Complementary Metal-Oxide-Semiconductor) procedure. The chip size is about 5mm x 5mm and was fab-out in July 20th, 2009.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.305-313
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• 2013

As an FMT (Filtered Multi-Tone) transmission method of Wideband VHF communication system specified by the ETS (European Telecommunications Standards) EN 300 392-2, this paper introduces three existing realization methods, i.e., the direct filtering method using different band SRRC (Square-Root Raised Cosine) filters for each subcarrier, the PPN-DFT method using the IDFT-PPN (Poly-Phase Network) and PPN-DFT at the transmitter and receiver, respectively, and the Extended DFT method. Then, it proposes the extended IDFT-SDFT (Sliding Discrete Fourier Transform) that computes the DFT values only for interested subcarriers every sample time, and shows that it has an advantage of blind symbol timing (using no training symbol) individually for each user signal (independently of other users' signals) in the multi-user environment where the subcarriers are assigned in contiguous or interleaved blocks to each user and each user signal possibly experiences different channels.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.1
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• pp.49-59
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• 2009

In this paper a watermarking algorithm is proposed to optimize the capacity of the digital watermark insertion in an experimental threshold using the characteristics of human visual system(HVS), adaptive scale factors, and weight functions based on discrete wavelet transform. After the original image is decomposed by a 3-level discrete wavelet transform, the watermarks for capacity optimization are inserted into all subbands except the baseband, by applying the important coefficients from the experimental threshold in the wavelet region. The adaptive scale factors and weight functions based on HVS are considered for the capacity optimization of the digital watermark insertion in order to enhance the robustness and invisibility. The watermarks are consisted of gaussian random sequences and detected by correlation. The experimental results showed that this algorithm can preserve a fine image quality against various attacks such as the JPEG lossy compression, noise addition, cropping, blurring, sharpening, linear and non-linear filtering, etc.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.4
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• pp.23-31
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• 2018

This paper presented the implementation and design of the 2T-2R wireless HD video streaming systems over 1.7 GHz frequency band using 3GPP LTE-TDD standard on NI USRP RIO SDR platform. The baseband of the system used USRP RIO that are stored in Xilinx Kintex-7 chip to implement LTE-TDD transceiver modem, the signal that are transmitted from USRP RIO up or down converts to 1.7 GHz by using self-designed 1.7 GHz RF transceiver modules and it is finally communicated HD video data through self-designed 2x9 sub array antennas. It is that communication method between USRP RIO and Host PC use PCI express x4 to minimize delay of data to transmit and receive. The implemented system show high error vector magnitude performance above 32 dBc and to transmit and receive HD video in experiment environment anywhere. The proposed hybrid beam forming system could be used not only in the future 5G mobile communication systems under 6 GHz frequency band but also in the systems over 6 GHz frequency band like ones in mmWave frequency bands.