So Ra Park

Equalization On-Channel Repeater for Terrestrial Digital Multimedia Broadcasting System

This paper presents technical requirements of on-channel repeaters (OCRs) to broadcast the terrestrial digital multimedia broadcasting (T-DMB) signals in single frequency network (SFN) environment. In order to meet such requirements, the configuration and implementation method of the equalization OCR are proposed. The proposed equalization OCR does not have only short processing delay, but also provides high quality transmitting signals with high power because of the rejection capability of a feedback signal introduced by incomplete antenna isolation and multipath signals existing between a main transmitter and the OCR. Computer simulations and laboratory tests results are provided to figure out performance of the proposed equalization OCR.

Development of T-DMB emergency broadcasting system and trial service with the legacy receivers

The emergency broadcasting system based on T-DMB network have been developed and installed in tunnel environment. This paper describes implementation and field test results of the T-DMB emergency broadcasting system in practical tunnel environment. The developed emergency broadcasting system can execute the on-channel repeating function in common environment. And the system provides emergency broadcasting service in accident or disaster environment to legacy T-DMB receivers. According to the field test results, the smooth operation is evaluated for both emergency broadcasting function and on-channel repeating function with legacy T-DMB receivers.

An efficient emergency broadcasting signal multiplexing method for supporting the legacy T-DMB receivers in break-in system

In this paper, design and implementation of T-DMB emergency broadcasting system (EBS) are introduced. Especially, to reduce the T-DMB EBS implementation cost, efficient encoding and multiplexing schemes are proposed and adopted to the system. Since proposed encoding and multiplexing technologies can reduce the number of encoders and multiplexers, the T-DMB EBS with proposed techniques are efficiently built. The performance of the T-DMB EBS has been evaluated by laboratory and field tests with various commercial receivers, satisfactory results have been drew1.

Laboratory Trials and Evaluations of In-Band Digital Radio Technologies: HD Radio and DRM+

Many countries are converting their analog communication and broadcasting services into digital services. However, digital radio broadcasting service is still an issue to be addressed. In order to provide digital radio broadcasting service, it is very important to choose the most appropriate digital radio method for their frequency environment and listeners. This paper depicts laboratory test results of in-band digital radio technologies, HD Radio and DRM+. To contribute to decision of digital radio standard and design of digital radio transmission network, various results of many test items are expressed.

Design and Performance Evaluation of Digital Radio Measurement Test Beds for Laboratory Test: DAB, DAB+, and T-DMB Audio

This paper depicts the digital radio test bed design and performance evaluation for digital audio broadcasting, DAB+, and terrestrial digital multimedia broadcasting audio systems that are representative digital radio broadcasting standards operating in band III (out-of-band). We consider a laboratory trial to measure the performance of each digital radio system. The existing broadcasting measurement systems have some limitations, such as the small number of available measurement items and broadcasting systems. However, the introduced test bed can cover above representative three digital radio systems and measure various performance parameters. This paper minutely describes not only the test bed designs but also various test results according to the measurement items. Therefore, this paper can help select an appropriate digital radio standard.

Electrostatic Focusing Lens Module With Large Focusing Capability in Carbon Nanotube Emitter-Based X-Ray Sources

We fabricated and analyzed an electrostatic focusing lens (FL) module comprising a micro-FL with many holes near the gate and a macro-FL of single aperture toward the anode for carbon nanotube (CNT) emitter-based X-ray sources. The micro-FL suppresses the divergence of the electron beams whereas the macro-FL governs the shape of the beam bundle. The FL module can be controlled over a wide range of gate and anode voltages while maintaining the focal spot. We achieved a small focal spot of 300 μm from CNT emitter dot arrays of 10 mm × 1.6 mm with line pairs of 3 lp/mm maintained for different anode voltages.

Field Trials and Evaluations of In-Band Digital Radio Technologies: HD Radio and DRM+

This paper depicts the field trials and results for in-band digital radio technologies in Korea. For the in-band methods, HD Radio and DRM+ are considered. In HD Radio, MP3 hybrid mode and MP5 all digital modes are selected, and 4-QAM and 16-QAM are selected for DRM+. To evaluate the practical performance of each technology, system parameters and received electric field strength are evaluated in various test routes and environments. In the field trial, listening tests are also executed by test staffs, and the results of listening tests are analyzed and compared with results of system parameters. Since the trials consider various practical reception environments, the test results can be used as references for decision of digital radio standard.

Compatibility analysis of in-band digital radio systems in interference channel environment

Many countries today face converting their analog radio broadcasting to digital service. Since the in-band digital radio systems are used in the existing analog FM frequency band, compatibility and robustness is very important characteristics of the digital radio systems. In this paper, we evaluate the performances of HD-Radio and DRM+ which are in-band digital radio broadcasting techniques in the various interference channel environment. These results are able to give basic information for the decision of digital radio standard in many countries.

A high-performance carbon nanotube-based field emission x-ray tube for commercial dental imaging

We developed a fully vacuum-sealed carbon nanotube (CNT)-based field emission x-ray tube with commercial-level performance for dental imaging application. The CNT x-ray tube was designed in a triode configuration with the focus-functional gate and had a compact size, much smaller than the conventional hot-cathode tubes. The small size of CNT x-ray tubes along with no cathode heating enables us to make a very compact portable dental imaging system. We have obtained a quite good x-ray image of a human tooth phantom by operating the CNT x-ray tube in an anode voltage of 65 kV, an emission current of 3 m A, and a pulse duration of 0.5 s, which is comparable to that of the conventional commercial hot-cathode tube.

Fast and Stable Operation of Carbon Nanotube Field-Emission X-Ray Tubes Achieved Using an Advanced Active-Current Control

The advanced active-current control (ACC) with a push-up voltage source is proposed for the fast operation of carbon nanotube (CNT) field-emission x-ray tubes while preserving the advantages of improved stability and reliability. The push-up voltage source, composed of a voltage supply and a resistor, was found to reduce markedly the response time of CNT x-ray tubes down to several tens nanoseconds. The very fast operation of CNT x-ray tube with the advanced ACC could provide an improved x-ray imaging technology, including high-speed scanning and blur-less imaging.