A high capacity fully digitalized modulator using parallel phase process techniques is developed for digital radio systems. Through the use of 1.2 p m BiCMOS technology, a modulator-LSI (MOD LSI) which guarantees 112 MHz operation is fabricated. Experimental results obtained for a 16 QAM MODEM with the MOD LSI show that this MODEM can be applied directly to a sub STM-l(51.84 Mbps) of an SDH system, to increase its cost-effectiveness, reliability and performance.
This paper describes a 256QAM 400 Mbls system and repeater configuration, using fading countermeasures with DSP technologies. A onechip transversal filter LSI is newly developed. This LSI is used for a fully digital transversal equalizer and a cross polarization interference canceller. It offers compactness, low power consumption and no tuning. An advanced control method called the shift bit select (SBS) and the MLE method are introduced to improve control response, a q u i s i t i o n a n d s t e a d y performance. The field test confirms good performance of the fading countermeasures with DSP technologies.
In digital radio communication employing multilevel modulation, the waveform equalizer is needed to eliminate the waveform distortion generated in the transmission channel or in other components. This paper aims at a highly accurate automatic equalizer which is applicable to the ultramultilevel modulation, such as 256 QAM, and discusses the fully digital realization of the equalizer which has been constructed by analog circuits.
First, the transversal equalizer to be used in 256 QAM is considered, and the relation between the number of taps and the equalizer performance is described theoretically. Then the construction of the fully digital waveform equalizer is proposed based on the digital signal processing techniques. The decision range expanded (DRE) method is proposed, aiming at the maximum utilization of the equalization performance of the waveform equalizer. Finally, the transversal automatic equalizer is implemented on LSI.
As a result of experiment with the clock rate of 12.5 Mbaud and 256 QAM signal, a satisfactory result agreeing with the theoretical investigation is obtained. Especially, it is demonstrated that the DRE method is very useful in constructing the digital waveform equalizer. Thus, a highperformance transversal automatic equalizer is realized, which is applicable to the ultramultilevel modulation system.
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