120GHz帯20Gbit/s QPSK送信，受信モジュール

摘要

NTT laboratories are developing a120-GHz-band wireless link using quadrature-phase-shifl keying (QPSK). We have reported 10-Gbit/s QPSK modulator and demodulator circuits and evaluation of the bit error performance. This paper presents the 120-GHz-band QPSK transmitter and receiver with the capacity of 20-Gbit/s and larger output power. The transmitter circuits consist of a 20-Gbit/s QPSK modulator with direct modulation, differential amplifiers for data, a power amplifier, and an output-power monitor circuit. To achieve the high-speed QPSK modulation, the modulator circuit in the transmitter has gain-control terminals which provide optimum modulation accuracy. The receiver circuits consist of differentially coherent detector, voltage-controlled phase shifter, and low-noise amplifier. We fabricated QPSK transmitter and receiver circuits on microwave monolithic integrated circuits (MMICs) and mounted these MMICs in WR-8 waveguide modules. We evaluated the bit error rate (BER) for 22.2-Gbit/s real-time data transmission. The transmitter and receiver exhibit the BER of smaller than 10~(10) at a receiver power of -35 dBm.%NTTでは120 GHz帯無線リンクの周波数利用効率向上のため,QPSK変復調方式の研究を進めており，これまでに10 Gbit/sの変復調MMICを報告した.本報告では，より大きな伝送容量，送信出力を持つ20 Gbit/s QPSK 送信，受信MMICについて述べる.20Gbit/sの変調速度を実現するため，変調回路には変調精度を最適化する利得調整端子が備えられ，レイァゥト上で生じる非対称性を補僙している.試作したMMICをモジュールへ実装し，22.2Gbit/sのリアルタイム伝送試験を実施したところ，受信電力-35 dBmで10-1D以下のBERが得られ，良好な伝送が可能であることを確認した.