No.127 Sep 2011

Research Presentations

  • Millimeter -wave Radio on Fiber System for Digital Broadcasting Signals
    Tsuyoshi NAKATOGAWA, Mikio MAEDA and Kimiyuki OYAMADA
    ↓summary

    summary

    ABSTRACT

    RoF(Radio on Fiber)is an attractive delivery method for areas or homes where it is difficult to install optical fiber cables. We have proposed a transmission method that provides multi-channel digital broadcasting services to subscribers on FTTH(Fiber To The Home)and millimeter-wave RoF networks using self-heterodyne technology. This paper describes a method for single side band(SSB)modulation with a reduced carrier, which increases the optical modulation index (OMI)by tuning the applied bias voltages of an external optical modulator. This method can increase the OMI and improve the reception CNR(Carrier-to-Noise Ratio)of millimeter-waves by 14 dB. In addition, we propose a novel millimeter-wave receiver for subscribers using selfheterodyne detection. The receiver separates the carrier and the side band and eliminates thermal noise close to the carrier. It can improve sensitivity by 10 dB compared with a conventional self -heterodyne receiver. A wireless transmission experiment proved the practicality of the receiver and the RoF system.
  • 1024-QAM Demodulator Robust to Phase Noise of Cable STB Tuners
    Takuya KURAKAKE, Naoyoshi NAKAMURA and Kimiyuki OYAMADA
    ↓summary

    summary

    ABSTRACT

    A 1024-QAM receiver for cable television networks has been developed to improve digital transmission capability. The 1024-QAM demodulator we developed for cable television networks uses a modified symbol-decision region to reduce the effects of phase noise due to set-top-box tuners. The symbol-decision region is optimized by analyzing phase noise distribution. Simulation results show that good demodulation characteristics of a 1024-QAM signal are achieved under typical phase - noise conditions. The results are verified in a field trial with a prototype demodulator and an off-the-shelf tuner. Now, our 1024-QAM transmission method can transmit a digital BS broadcasting channel’s signal(approx. 52 Mbps)on a single cable TV channel.