• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1689-1692
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• 2002

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time- variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipaths within one chip are distinguished into each one and the strongest signal is selected. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.887-892
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• 2003

In this paper, we propose a simple scaling algorithm for CDMA mobile communications where a voice traffic signals are transmitted by individual one of several data rates at every frames. The traditional method is based on using look-up table called SMT(symbol metric table), but the proposed algorithm is real-time direct scaling method through simple bit manipulations without lookup table. The bit error rate performance is calculated by computer simulation over AWGN and Rayleigh fading channels. From the results, it is shown that the proposed algorithm outperforms the traditional SMT method on Rayleigh channel by 0.3∼0.8dB, while achieving the less H/W complexity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.128-136
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• 2006

In this paper, design and implement 50W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of ideal Doherty power amplifier is distinguishable; however bias control for implementation of Doherty(GDCHD) amplifier is difficult. To solve the problem, therefore, GDCHD(Gate and Drain Control Hybrid Doherty) power amplifier is embodied to drain bias adjustment circuit to Doherty power amplifier with gate bias adjustment circuit. Experiment result shows that $2.11{\sim}2.17\;GHz$, 3GPP operating frequency band, with 57.03 dB gain, PEP output is 50.30 dBm, W-CDMA average power is 47.01 dBm, and -40.45 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GDCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than Doherty power amplifier.

• Journal of information and communication convergence engineering
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• v.5 no.2
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• pp.177-180
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• 2007

We compared CS-ACELP with QCELP speech coder in CDMA cellular under channel error environment and experimented performance with its measured value under channel error environment. Also, we specified the effective coding scheme to overcome. CS-ACELP speech coder using a LSP vector quantizer shows transparent speech quality from the results that SD is 0.92dB and outlier frames over 2dB is 2.9% in the BER 0.10% condition. CS-ACELP speech coder which is utilizing MA predictor shows better results on SVR and SEGSNR than QCELP speech coder(IS-96) adopting DPCM type predictor when bit error occurs from BER 0.01% to 0.50%.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.393-398
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• 2014

A highly efficient dual-mode linear CMOS stacked-FET power amplifier (PA) is implemented for 3G UMTS and 4G LTE handset applications. High efficiency is achieved at a backed-off output power ($P_{out}$) below 12 dBm by employing an active-bypass amplifier, which consumes very low quiescent current and has high load-impedance. The output paths between high- and low-power modes of the PA are effectively isolated by using a bypass switch, thus no RF performance degradation occurs at high-power mode operation. The fabricated 900 MHz CMOS PA using a silicon-on-insulator (SOI) CMOS process operates with an idle current of 5.5 mA and shows power-added efficiency (PAE) of 20.5%/43.5% at $P_{out}$ = 12.4 / 28.2 dBm while maintaining an adjacent channel leakage ratio (ACLR) better than -39 dBc, using the 3GPP uplink W-CDMA signal. The PA also exhibits PAE of 35.1% and $ACLR_{E-UTRA}$ of -33 dBc at $P_{out}$ = 26.5 dBm, using the 20 MHz bandwidth 16-QAM LTE signal.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.89-94
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• 2007

For successful implementation of multi-standard transmitter, reconfigurable architecture and component design are essential. This paper presents a reconfigurable CMOS power amplifier designed CMOS 0.25 um process. Designed power amplifier can be operated at 0.9, 1.2, 1.75, and 1.85 GHz. Also, it can be used at 2.4 GHz by using bonding wire inductor. The interstage matching network is composed of two inductors and four switches, and operation frequency can be varied by controlling switches. Proposed power amplifier can be used as a power amplifier in low power applications such as ZigBee or Bluetooth application and used as a driver amplifier in high power application such as CDMA application. Designed power amplifier has 18.2 dB gain and 10.3 dBm output power at 0.9 GHz. Also, it represented 10.3 (18.1) dB gain and 5.2 (10) dBm output power at 1.75 (2.4) GHz.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.211-214
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• 2007

In this paper, we have designed microstrip antenna if 800[MHz] band It will be able to integrate TRS(Trunked Radio System), GSM(Global System for Mobile telecommunication) band including the CDMA(Code Division Multiple Access) band we designed repeater and a base station antenna which is possible at the ship and marine of safety. It is improves a narrow bandwidth problem of microstrip antenna. It had U-shaped feeding structure at a rectangular patch And ground or feeding structure used between dielectric constant(${\varepsilon}_T$ = 2.1), patch or feeding structure used between dielectric constant(${\varepsilon}_T$ =1). So it used a duplex resonance effect Designed frequency bandwith(V5WR 2:1) if the antenna showed good characteristic of $780[MHz]{\sim}1.83[GHz]$ to 2.61[GHz]. Also the E-plan and H-plan all profit 9.4[dBi] above, the 3[dB] beam width showed the characteristic over the E-plan and H-plan $60^{\circ}$ to be improved.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1027-1034
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• 2014

We present the Low Power Broadband Low noise amplifier(LNA) that can be applied a whole bandwidth from 3G to 4G LTE. This multi input LNA was designed to steadily amplify through a multi input method regardless the size of the input signal and operate on a wide range of frequency band from a standard 3G CDMA band 1.2GHz to LTE band 2.5GHz. The designed LNA consumes an average of 6mA on a 1.2V power supply and this was affirmed using computer simulation tests. The amplification which was corresponded to the lowest input signal is at a maximum of 20dB and was able to obtain the minimum value of the gain of -10dB. The Noise figure is less than 3dB at a High-gain mode and is less than 15dB at a Low-gain mode.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.1-8
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• 2005

In this paper, design and implement 60W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of Doherty power amplifier is distinguishable; however implementation of assistance amplifer is difficult, though. To solve the problem, therefore, GCHD (Gate Control Hybrid Doherty) power amplifier is embodied to gate bias adjusament circuit of assistance amplifier to General Doherty power amplifier. Experiment result shows that $2.11\~2.17GHz$, 3GPP operating frequency band, with 62.55 dB gain, PEP output is 50,76 dBm, W-CDMA average power is 47.81 dBm, and -40.05 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than general power amplifier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.947-955
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• 2002

In this paper, we derive an outage probability for the Erlang capacity and the link margin respectively, calculate them with the same parameters and outage probability, and then analyze a capacity and cell coverage in city, suburban, and open area. So, the Erlang capacity is more real than in a cell, and the cell coverage can be calculated with high reliability by the margin. When the $E_b/N_o$ decreases from 7 dB to 5 dB within the outage probability of 5 %, it is observed that the capacity is increased from 18 Erlang to 31 Erlang with the same margin of 2.8 dB, then the coverage is increased to 0.4 km, 1 km, and 2.5 km in city, suburban, and open area respectively. Also if the outage probability is decreased from 5 % to 2 % in case of $E_b/N_o$ of 5 dB, the result shows a very reliable link with additional increment of 0.88 dB in the margin and a high QoS (quality of service) within decrement of 0.15 km, 0.5 km, and 1.5 km for the same areas with decrement of 3 Erlang from 31 Erlang.