• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.48-58
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• 2012

New digital predistortion technique is proposed for power amplifier linearization in multi-band transmission systems. We consider a system where muli-band signals are combined and amplified by a single power amplifier (PA). In this system, the PA output is distorted by the nonlinear cross-products between different band signals as well as their own nonlinear self-products. To compensate these nonlinear effects, we propose a multiple PD structure. Each PD removes the nonlinear cross-products and self-products to mitigate the spectral regrowth for the corresponding band. Since the PD parameters for different bands are linked together, it is difficult to find the PD parameters separately. Thus, we propose an iterative method for finding the PD parameters jointly. For demonstration of the proposed method, multi-band characteristics of PA are extracted from a commercial power amplifier. Computer simulation was executed based on the PA parameters. The simulation results show that the proposed method can effectively linearize the PA and remove spectral regrowth at each signal band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.895-906
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• 1993

In this paper, MTSVQ(Multirate Tree-Structured Vector Quantization) is introduced for subband image coding. Original images are decomposed into a number of subband components, and multiresolution codebook is designed by MTSVQ algorithm. Optimal bit allocation among the subband components becomes the problem selecting the particular pruned subtree of MTSVQ which has the desired rate and distortion.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1053-1058
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• 2021

This paper presents the multi-band mixer which converts a X-, K- and Ka-band adaptively by adjusting the gate-bias voltage of an active device. The proposed mixer presented a conversion loss of -10 dB at -0.8 V gate-bias voltage for X-band, a conversion loss of -9 dB at -0.3 V gate-bias voltage for K-band and for Ka-band, a conversion loss of -7 dB at -0.2 V gate-bias voltage under the LO power of +6.0 dBm. The 1dB compression point (P1dB) is +0.5 dBm for all band.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.32-37
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• 2010

The algorithm of multiple channel signal processing requires the flexibility of variable frequency band, efficient allocation of transmission power, and flexible frequency band reallocation to satisfy various service types which requires different transmission rates and frequency band. There are three methods including per-channel approach, multiple tree approach, and block approach performing frequency band reallocation method by channelization and dechannelization in the multiple-channel signal. This paper proposes an improved per-channel approach for converting the frequency band of multiple carrier signals efficiently. The proposed algorithm performs decimation and interpolation using CIC(cascaded integrator comb filter), half-band filter, and FIR filter. In addition, it performs filtering of each sub-channel, and reallocates channel band through FIR low-pass filter in the multiple-channel signal. The computer simulation result shows that the perfect reconstruction of output signal and the flexible frequency band reallocation is performed efficiently by the proposed algorithm.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.583-586
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• 2001

본 논문에서는 다중 대역통과 표본화 이론에 기반하여 1.9GHz IS-95신호와 2.2GHz IMT-2000 신호를 하나의 ADC(analog to digital converter)를 사용하여 동시에 표본화하고 디지털 처리를 수행하는 방법을 제안하고 실험을 통하여 검증하였다. 일반적인 방법으로는 본 논문에서 고려하는 두 신호를 동시에 표본화하기 위해서는 표본화 주파수가 최소한 1GHz 이상의 고속의 ADC를 사용해야 한다. 그러나 현재 ADC의 기술은 광대역의 신호를 직접 더지털화하기에는 아직 미흡하다. 반면에 대역통과 표본화 이론은 기존의 상용 ADC와 기콘의 RF 시스템을 이용하여 다른 대역에 위치한 두 신호를 통합처리 할 수 있는 기반을 제공하고 있다. 본 논문에서는 이러한 대역통과 표본화 이론에 기반을 두고 상용 ADC를 사용하여 표본화 시스템을 구현하여 IS-95신호와 IMT-2000 신호를 표본화하고 이를 컴퓨터에서 디지털 필터를 이용하여 두 신호를 분리하는 실험을 통하여 다중 대역통과 표본화의 적용 가능성을 검증하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• fall
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• pp.78-79
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• 2021

본 논문에서는 시간 영역 오토인코더의 성능 개선을 위한 다중 대역 손실 함수를 제안한다. 기존의 시간 영역 오토인코더를 사용하는 압축 및 복원 모델은 저 대역 손실에 치중되어 고 대역 신호를 생성하지 못하고 다운 샘플링된 신호를 결과로 출력하는 문제점을 가진다. 이를 해결하기 위해 대역별로 손실을 분리하여 가중치를 조절할 수 있는 다중 대역 손실 함수를 제안한다. 제안하는 손실 함수가 적용된 오토인코더에 음성 신호를 입력하여 학습을 진행한 결과, 다운 샘플링이 발생하지 않으며 고 대역 신호가 복원되는 것을 스펙트로그램을 통해 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2615-2621
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• 2010

The multi-band six-port phase correlator using metamaterial was designed and fabricated in this paper. The lumped metamaterial structure that can process the dual-band receiving signal was analyzed. Based on the analyzed results, the small-sized metamatrial six-port phase correlator for multi-band direct conversion method was proposed and fabricated. Also, the resistive power divider and $90^{\circ}$ hybrid coupler that comprises the six-port phase correlator were implemented based on the scattering parameters of metamatrial six-port phase correlator. The measured results of the proposed six-port phase correlator show the good agreement with simulation results. The performance of the six-port phase correlator shows the reflection loss below -20 dB in the dual-band. Also, the proposed six-port phase correlator got a good transmission characteristic within 1 dB gain difference and ${\pm}4.1^{\circ}$ phase imbalance, respectively.

• Journal of Digital Contents Society
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• v.5 no.3
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• pp.187-191
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• 2004

Rapid time variations of the mobile communication channel have a dramatic effect on the performance of multi-carrier modulation. This paper analyzed the bit error rate (BER) performance for multi-carrier code division multiple access (MC-CDMA) network, and derived the equivalent signal-to-total noise plus interference(SNIR) of MC-CDMA system in the reverse link, the performance of MC-CDMA/BPSK signal is evaluated taking into account the fraction of partial-band interference and interference power. and the effect of partial-band interference is comprehensively studied in order to further improve the Qos of multi-carrier multimedia system.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.23-28
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• 2016

In this paper, a Multi-Band Ku-band down converter was designed for reception of multi-band digital satellite broadcasting. The Multi-band low-nose down converter was designed to form four local oscillator frequencies (9.75, 10, 10.75 and 11.3GHz) representing a low phase noise due to VCO-PLL with respect to input signals of 10.7 to 12.75GHz and 3-stage low noise amplifier circuit by broadband noise matching, and to select an one band of intermediate frequency (IF) channels by digital control. The developed low-noise downconverter exhibited the full conversion gain of 64dB, and the noise figure of low-noise amplifier was 0.7dB, the P1dB of output signal 15dBm, and the phase noise -73dBc@100Hz at the band 1 carrier frequency of 9.75GHz. The low noise block downconverter (LNB) for receiving four-band digital satellite broadcasting designed in this paper can be used for satellite broadcasting of vessels navigating international waters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1259-1268
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• 2010

In this paper, we presented a new LC prototype synthesis method for the multi-band filter. For synthesis a multi-band filter with the required frequency response, we proposed the diagram of poles and zeros, also, we proposed the optimization process for finding the combination of optimized poles and zeros. From the transfer and reflection functions calculated from poles and zeros, we performed the quasi-elliptic LC prototype synthesis of multi-band filter. Using the proposed LC prototype synthesis method of multi-band filter, dual-band filter operating at GSM(880~960 MHz) and ISM(2,400~2,500 MHz) and triple-band filter operating at GSM(880~960 MHz) and ISM(2,400~2,500, 5,725~5,850 MHz) were designed and fabricated.