Il-Kyoo Lee

Analysis and design of feedforward power amplifier

A linear power amplifier is particularly emphasized on the system using a linear modulation scheme, because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance, a phase imbalance and a delay mismatch, are fully analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for Korea PCS frequency band. The center frequency of the feedforward amplifier is 1.855 GHz with 30 MHz bandwidth. The cancellation performance of the first linearization loop is more than 40 dB and intermodulation cancellation performance of feedforward amplifier is more than 35 dB.

A Performance Comparison of Code Acquisition Techniques in DS-CDMA System

This paper compares parallel acquisition with hybrid acquisition in terms of mean acquisition time in code acquisition system of forward link and reverse link of direct sequence code division multiple access (DS-CDMA) system. The mean acquisition time of the hybrid and parallel acquisitions is derived from the distribution of the multiple correct code-phase offsets. Especially, the mean acquisition time of the hybrid acquisition scheme is derived by considering both case 1 (the correct code-phase offsets are included in one subset) and case 2 (the correct code-phase offsets exist at the boundary of two subsets), which are caused by the distribution of the correct code-phase offsets in the subset. Results are provided for the performance comparison between hybrid acquisition and parallel acquisition under the same hardware complexity in the forward and reverse links. In our performance evaluation of code acquisition in DS-CDMA system, the hybrid acquisition shows a better performance than the parallel acquisition in terms of mean acquisition time of the both links in the frequency-selective Rayleigh fading channel.

Chaotic-OOK UWB modem Using new unipolar ZCD codes for wireless PAN

In this paper, we propose a chaotic-OOK (on-off keying) UWB (ultra wideband) modem using new unipolar ZCD (zero correlation duration) spreading code having interference cancellation property for IEEE 802.15.4a WPAN (wireless personal area network).

Analysis of UE RF parameters for 3GPP specifications

The paper describes the key RF factors of UE (user equipment) for W-CDMA systems based on 3GPP specifications. The transmitter and receiver parameters are derived from the viewpoint of RF. In order for UE to retain high performance, the transceiver design requirements - such as ACLR (adjacent channel leakage power ratio), EVM (error vector magnitude), peak code domain error, spectrum emission mask for transmitter and reference sensitivity level, blocking characteristics, noise figure, ACS (adjacent channel selectivity), receiver AGC dynamic range - are considered. The UE transceiver is implemented and its performance requirements analysed through test scenarios.

The design and implementation of TV tuner for digital terrestrial broadcasting

The DTV tuner for 8-VSB modulation was developed with satisfying the requirements of the ATSC. The double frequency conversion and the active tracking filter in the front-end were used for the cancellation of the interferences between adjacent channels and multi-channels by suppressing IF beat and image band. However, it was impossible to get frequency mapping between the tracking filter and the first VCO in the existing DTV tuner structure differing from the NTSC tuner. This paper, therefore, suggests the available structure and a new method for automatic frequency selection by obtaining the mapping of frequency characteristic over the tracking voltage and the combined hardware which is composed of a microcontroller, EEPROM, D/A, op amp and switch driver.

Potential Interference of Electric Equipments on Radio Service below 30MHz

This paper analyzed a potential interference of electric equipments on radio service below 30MHz through an experiment with a PDP(Plasma Display Panel) TV and a RF(Radio Frequency) light bulb in an anechoic chamber. The radiation levels of the PDP TV and the RF light bulb are measured and a combined interference is calculated on the basis of the experimental value. As a result, the combined interference signal level is increased according to the number of interferer. The possibility of a potential interference from electric equipments on radio service below 30MHz is realized through comparison between the measured radiation value of electric equipments and the CISPR(International Special Committee on Radio Interference) 11 limit.

The Gain and Phase Mismatch Detection Method with Closed Form Solution for LINC System Implementation

This parer proposed the path mismatch detection and compensation algorithm with closed form for linear amplification with non-linear components(LINC) system implementation. The LINC system has a merit of using the high efficient amplifier by transferring the non-constant envelop signal which is high peak to average signal ratio into constant envelop signal. However, the performance degradation is very sensitive to the path mismatch such as an amplitude mismatch and a phase mismatch. In order to improve the path mismatch, the error detection and compensation method is introduced by the use of four test signals. Since the presented method has the closed form solution, the efficient and fast detection is available. The digital-IF structure of LINC system applied by the proposed error detection and compensation algorithm was implemented. The performance was evaluated with the IEEE 802.16 WiMAX baseband sinal which has 7 MHz channel bandwidth and 16-QAM. The Error Vector Magnitude(EVM) of -37.37 dB was obtained through performance test, which meets performance requirement of -24 dB EVM. As a result, the introduced error detection and compensation method was verified to improve the LINC system performance.

The implementation of a base station transceiver for WLL system based on wideband CDMA

The implementation of a BTS (base station transceiver) for a WLL system using a wideband CDMA (W-CDMA) method is presented. It consists of three boards; receiver, transmitter, and RF controller. Some RF parameters are considered and simulated by the RF simulation software using commercial and customized component specifications. The implemented transceiver of 5 MHz RF channel bandwidth satisfies the system requirements of a transceiver such as dynamic range, receiver sensitivity, and spurious emission suppression in the transmitter. At the receiver, the experimental measurement showed a noise figure (NF) of 2.86 dB and a dynamic range of above 60 dB in AGC locking. At the transmitter, the -49.34 dBc of spurious emission suppression is attained when the output power of the transmitter is 34.3 dBm. These results are good enough to meet standard performance specifications.

A Study on Co-existence between DTV Transmitter and LTE Base Station according to DTV Transition

This paper is about frequency allocation of LTE Base Station(BS) in the spare band which is generated by DTV transition. In the case of frequency allocation of LTE BS in adjacent band with DTV channel 51 among the spare band, the guard bands that requires for no interference between LTE and DTV system were calculated. As a result, 5.5 MHz of guard band for LTE BS and 2 MHz of guard band for DTV receiver were suggested based on interference analysis between LTE BS and DTV BS, respectively.

Analysis of the Protection Ratio of GPS System in the Presence of RF Interference Radiated by UWB System

This paper analyzes potential interference effects of Ultra Wide Band(UWB) on Global Positioning System(GPS) which is providing safety service. For the interference analysis, positioning error method is used to determine the minimum protection distance to meet positioning error of 2.5 m below and Minimum Coupling Loss(MCL) method is used to determine the required protection ratio(I/N) from the protection distance of UWB transmitter and GPS receiver to meet positioning error of 2.5 m below. In a result, the minimum protection distance to meet positioning error of 2.5 m below was about 10 m and the protection ratio to meet positioning error 2.5 m below was -20 dB. The protection ratio proposed in this paper is the same value of the protection ratio of safety service proposed by ITU-R. The obtained protection ratio can be used for the protection standard of domestic GPS system for the safe of life service.