• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.341-346
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• 2009

M-WiMAX (Mobile-Worldwide Interoperability for Microwave Access) system, which uses OFDM (Orthogonal Frequency Division Multiplexing) technique, is known to be proper for mobile high-speed data transmission system. Nevertheless, M-WiMAX is seriously sensitive to IQ imbalance caused by the LO (Local Oscillator) at the receiver. In this paper, we analyze the effect of IQ imbalance on the system, and then propose a joint optimization scheme that can optimize DFE (Digital Front-end) of mobile modem by combining operation duplicated between AGC (Automatic Gain Control) and the estimation and compensation of IQ imbalance. Simulation results show that the proposed scheme achieves the same performance of the conventional scheme while reducing the complexity of the H/W implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.77-86
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• 2010

In this paper, we present a noncoherent IR-UWB (Impulse Radio-Ultra Wide Band) ranging system with an AFE (Analog Front End) composed of a simple integrator and an 1-bit ADC (Analog-to-Digital Converter), and define AFE characteristics affecting the ranging performance. This system is realistic and easy to implement, since the integrator simply accumulates signal energies and the simple 1-bit ADC is applied instead of the multi-bit ADCs for coherent IR-UWB systems. On the other hand, its ranging accuracy is largely affected channel environments such as noise, multipath fading and so on, since the noncoherent receiver simply squares and integrates the received signals. However, despite these practical importances, there are few conventional researches on the performance analysis according to AFE characteristics in IR-UWB ranging systems. To this end, we analyze in this paper ranging performance according to AFE characteristics for the noncoherent IR-UWB ranging system in various wireless channel environments, and through these results we also present system parameters to be considered in UWB hardware designs.

• ETRI Journal
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• v.26 no.6
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• pp.555-559
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• 2004

We propose an efficient digital IF down converter architecture for dual-mode WCDMA/cdma2000 based on the concept of software defined radio. Multi-rate digital filters and fractional frequency conversion techniques are adopted to implement the front end of a dual-mode receiver for WCDMA and cdma2000. A sub-sampled digital IF stage was proposed to support both WCDMA and cdma2000 while lowering the sampling frequency. Use of a CIC filter and ISOP filter combined with proper arrangement of multi-rate filters and common filter blocks resulted in optimized hardware implementation of the front end block in 292k logic gates.

• ETRI Journal
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• v.27 no.5
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• pp.484-490
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• 2005

We fabricated 40 Gb/s front-end optical receivers using spot-size converter integrated waveguide photodiodes (SSC-WGPDs). The fabricated SSC-WGPD chips showed a high responsivity of approximately 0.8 A/W and a 3 dB bandwidth of approximately 40 GHz. A selective wet-etching method was first adopted to realize the required width and depth of a tapered waveguide. Two types of electrical pre-amplifier chips were used in our study. One has higher gain and the other has a broader bandwidth. The 3 dB bandwidths of the higher gain and broader bandwidth modules were about 32 and 42 GHz, respectively. Clear 40 Gb/s non-return-to-zero (NRZ) eye diagrams showed good system applicability of these modules.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.210-216
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• 2004

In this paper, we propose a noncoherent On-Off Keying (OOK) Ultra Wide Band (UWB) system based on power detection with noise power calibration for low power applications. The proposed UWB system achieves good bit error rate performance which is favorably comparable to that of the system using the ideal adaptive threshold, while maintaining simple receiver structure, In addition, low power Analog Front-End (AFE) blocks for the proposed noncoherent UWB transceiver are proposed and verified using CMOS technology. Simulation results on the pulse generator, delay time generator and 1-bit Analog-to-Digital (AID) converter show feasibility of the proposed UWB AFE system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1235-1240
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• 2008

In this paper, we presented an active RFID system in 2.45GHz range including LNA, Mixer and gain block. And in this work, a link budget model for RFID applications are proposed. We describe the detailed design and implementation of our system. Our components in RFID system has features such as low Noise Figure, reliable energy budget, and standard compliance with ISO 18000-4. Our receiver is effective for development and evaluation of prototype applications because of the flexibility of the design hardware. So, our platform will be suitable for versatile item management applications.

• Journal of information and communication convergence engineering
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• v.18 no.4
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• pp.254-259
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• 2020

Phased-array antennas comprise a demanding antenna design methodology for commercial wireless communication systems or military radar systems. In addition to these two important applications, the phased-array antennas can be used in beamforming for wireless charging. In this study, a four-way analog beamforming front-end module (FEM) for a hybrid beamforming system is developed for 2.4 GHz operation. In a hybrid beamforming scheme, an analog beamforming FEM in which the phase and amplitude of RF signal can be adjusted between the RF chain and phased-array antenna is required. With the beamforming and beam steering capability of the phased-array antennas, wireless RF power can be transmitted with high directivity to a designated receiver for wireless charging. The four-way analog beamforming FEM has a 32 dB gain dynamic range and a phase shifting range greater than 360°. The maximum output RF power of the four-way analog beamforming FEM is 40 dBm (=10 W) when combined the four individual RF paths are combined.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.767-773
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• 2008

Galileo is a new civil Global Navigation Satellite System(GNSS) developed by Europe. GIOVE-A, a satellite to test Galileo system performance, transmits navigation signal on orbit. Evaluation of Galileo system and development of Galileo receiver needs to analyze GIOVE-A signals. In this paper, we received GIOVE-A signals and processed it using GIOVE-A Interface Control Document(ICD). Signal acquisition, tracking and navigation message decoding made grasping current signal status possible. Bandwidth increase by BOC modulation is one of the difference from GPS. Therefore, we investigated feasibility of conventional GPS L1 RF front-end to receive GIOVE-A E1 signal by evaluation of receiving performance of navigation signal on each bandpass filter of RF front-end.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.1
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• pp.43-50
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• 2016

In this paper, new automatic LC calibrator is proposed for realizing a passive LC filter with almost constant frequency characteristic regardless of the PVT variations. The SAW-less GPS RX front-end is implemented using a 65nm CMOS process using the proposed LC calibrator. Also, new dual-mode low noise amplifier (LNA) structure is proposed to generate the RF signal required for the LC calibrator. The characteristics of the implemented GPS RX front-end show the voltage gain of about 42.5 dB, noise figure of below 1.35 dB, the blocker input P1dB of -24 dBm in case of the worst blocker signal at 1710 MHz frequency, while it consumes 7 mA current at 1.2 V power supply voltage.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.1-6
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• 2011

In this paper, an 1.5Gbit/s wireless data transmission system using the carrier frequency of 300 GHz band was implemented. The RF front-end was composed of schottky diode sub-harmonic mixer, frequency tripler, and horn antennas for transmitter and receiver, respectively. The LO frequencies of sub-harmonic mixer are 150GHz for transmit chain and 156GHz for receive chain. The ASK(Amplitude Shift Keying) modulation was used in the transmitter and the envelope detection method was used in the heterodyne receiver. The conversion loss of sub-harmonic mixer and implementation system loss were measured to be 9.8dB and 1.2dB, respectively. The 1.5Gbit/s video signal with HD-SDI format was transmitted over wireless distance of 40cm without optical lens(4.2m with optical lens) and displayed on HDTV at the transmitted average output power of $20{\mu}W$.