Akihiko Hirata

120-GHz-band millimeter-wave photonic wireless link for 10-Gb/s data transmission

A 120-GHz-band wireless link that uses millimeter-wave (MMW) photonic techniques was developed. The output power and noise characteristics of 120-GHz-band MMWs generated by converting a 125-GHz optical subcarrier signal were evaluated. It was then shown that the noise characteristics of the 125-GHz signal generated with these photonic technologies is sufficient for 10-Gb/s data transmission. We constructed a compact 120-GHz-band wireless link system, and evaluated its data transmission characteristics. This system achieved error-free transmission of OC-192 and 10-GbE signals over a distance of more than 200 m with a received power of below -30 dBm.

120-GHz wireless link using photonic techniques for generation, modulation, and emission of millimeter-wave signals

We present a wireless link system that uses millimeter-wave (MMW) photonic techniques. The photonic transmitter in the wireless link consists of an optical 120-GHz MMW generator, an optical modulator, and a high-power photonic MMW emitter. A uni-traveling carrier photodiode (UTC-PD) was used as the photonic emitter in order to eliminate electronic MMW amplifiers. We evaluated the dependence of UTC-PD output power on its transit-time limited bandwidth and its CR-time constant limited bandwidth, and employed a UTC-PD with the highest output power for the photonic emitter. As for the MMW generation, we developed a 120-GHz optical MMW generator that generates a pulse train and one that generates a sinusoidal signal. The UTC-PD output power generated by a narrow pulse train was higher than that generated by sinusoidal signals under the same average optical power condition, which contributes to reducing the photocurrent of the photonic emitter. We have experimentally demonstrated that the photonic transmitter can transmit data at up to 3.0 Gb/s. The wireless link using the photonic transmitter can be applied to optical gigabit Ethernet signals.

10-Gbit/s Wireless Link Using InP HEMT MMICs for Generating 120-GHz-Band Millimeter-Wave Signal

We have developed a 120-GHz-band wireless link whose maximum transmission data rate is 11.1 Gbit/s. The wireless link uses millimeter-wave monolithic integrated circuits (MMICs) for the generation of a 120-GHz-band millimeter-wave wireless signal. The MMICs were fabricated using 0.1-mum-gate InP-HEMTs and coplanar waveguides. The wireless link can handle four kinds of data rate for OC-192 and 10-Gbit Ethernet standards with and without forward error correction (FEC). We succeeded in the error-free transmission of a 10-Gbit/s signal over a distance of 800 m. The introduction of FEC into the 120-GHz-band wireless link decreased the minimum received power for error-free transmission, and improved the reliability of the link.

120-GHz-Band Wireless Link Technologies for Outdoor 10-Gbit/s Data Transmission

Our progress in 120-GHz-band wireless link technologies enables us to transmit 10-Gbit/s data transmission over a distance of more than 1 km. The 120-GHz-band wireless link uses high-speed uni-traveling carrier photodiodes (UTC-PD) and InP high-electron mobility transistor (HEMT) millimeter-wave (MMW) monolithic integrated circuits (MMICs) for the generation of MMW signals. We investigate the maximum output power of these devices and compare the phase noise of MMW signals generated by UTC-PDs and InP HEMT MMICs. We describe the antennas we used and their operation technologies. Finally, we investigate the dependence of transmission distance on availability using the statistical rain attenuation data. The calculation results show that the 120-GHz-band wireless link can transmit 10-Gbit/s data over a distance of 1 km with availability of 99.999%.

Transmission Characteristics of 120-GHz-Band Wireless Link Using Radio-on-Fiber Technologies

The transmission characteristics of a 120-GHz-band millimeter-wave wireless link are described. The wireless link uses photonic technologies for generation, modulation, and transmission of millimeter-wave signals. This configuration enables set up of the photonic millimeter-wave generator and transmitter core separately; therefore, the wireless link can be used as a kind of radio-over-fiber system. The effects of transmitting 120-GHz-band optical subcarrier signals through single-mode fibers were theoretically and experimentally investigated. It was confirmed that the time shift of the code edges, because of chromatic dispersion, limits the transmission distance. A data stream at 10-Gbit/s was successfully transmitted over the 120-GHz-band millimeter-wave wireless link, with a bit error rate (BER) below 10-12 over a distance of 250 m. The results also demonstrated the stability of the wireless link, which satisfied the 10-Gb Ethernet standard under clear weather conditions.

5.8-km 10-Gbps data transmission over a 120-GHz-band wireless link

We have developed 120-GHz-band wireless equipment that can transmit 10-Gbit/s data signal over a distance of more than 5 km. In order to increase the output power of the120-GHz-band wireless equipment, we used a millimeter-wave amplifier that integrates 0.08-µm-gate-length InGaAs/InP composite-channel high-electron-mobility transistors. The output power of the wireless equipment becomes 16 dBm. The wireless equipment can handle data rates of 1 Mbit/s to 11.1 Gbit/s and transmit 10-Gbit/s-class data signals with and without forward error correction (FEC). We conducted wireless data transmission experiments over a distance of 4.8 km and 5.8 km and succeeded in the error-free data transmission of 10-Gbit/s data with FEC.

High-directivity photonic emitter using photodiode module integrated with HEMT amplifier for 10-Gbit/s wireless link

We present a high-directivity photonic emitter with a high-gain antenna and waveguide-output photodiode module (WG-PM) for extending the transmission distance of a wireless link that uses a 120-GHz millimeter wave. The module employs a uni-traveling-carrier photodiode, broad-band high electron-mobility transistor (HEMT) amplifier, and planar-circuit-to-waveguide transition substrate. The maximum output power of the WG-PM is 8 dBm at a frequency of 120 GHz, and it has a 3-dB bandwidth of over 16 GHz. The wireless link with the high-directivity photonic emitter achieved 10-Gbit/s wireless data transmission, and using a high-gain Gaussian optic lens antenna and an HEMT amplifier reduced the input optical power necessary for error-free transmission. The transmission characteristics of the link showed that its transmission distance can be extended to over 100 m.

MM-wave long-range wireless systems

Emerging technologies for long-range broadband wireless link systems were introduced. The common problem presented is how to construct a 10-Gb/s modem block with better performance at low cost. A single-carrier system with a simple modulation technique has the advantages of low cost and fast deployment. However, the drawback is poor spectral efficiency. A system using multiple carriers enables higher-order modulation; nevertheless, the hardware is presently very expensive. We described the circuit design and performance of ICs and their waveguide modules for 120-GHz, 10-Gb/s broadband wireless link systems. The demonstration results indicate that the IC modules using InP HEMTs enable us to construct viable 120-GHz millimeter-wave wireless link systems.

A 120-GHz millimeter-wave MMIC chipset for future broadband wireless access applications

A flexible CPW-MMIC (coplaner-waveguide monolithic microwave integrated circuit) chipset has been fabricated for 120 GHz future broadband wireless systems. The power amplifier has small signal gain of 8.5 dB from 115 to 135 GHz. The 1 dB compression point is 3 dBm at 120 GHz. We employed a traveling wave switch configuration for the ASK modulator. The insertion loss of the switch is less than 1.5 dB and the on-off ratio is more than 13.5 dB at 120 GHz. For the ASK modulator-demodulator chipset, the measured BER is 1e/sup -10/ for 10 Gbit/s PRBS 2/sup 11/-1 data at -13 dBm input power and 120 GHz RF frequency. The frequency doubler has an output power of -11 dBm at 120 GHz with fundamental and harmonics rejection better than 30 dBc.

Broadband dielectric spectroscopy of glucose aqueous solution: Analysis of the hydration state and the hydrogen bond network.

Recent studies of saccharides peculiar anti-freezing and anti-dehydration properties point to a close association with their strong hydration capability and destructuring effect on the hydrogen bond (HB) network of bulk water. The underlying mechanisms are, however, not well understood. In this respect, examination of the complex dielectric constants of saccharide aqueous solutions, especially over a broadband frequency region, should provide interesting insights into these properties, since the dielectric responses reflect corresponding dynamics over the time scales measured. In order to do this, the complex dielectric constants of glucose solutions between 0.5 GHz and 12 THz (from the microwave to the far-infrared region) were measured. We then performed analysis procedures on this broadband spectrum by decomposing it into four Debye and two Lorentz functions, with particular attention being paid to the β relaxation (glucose tumbling), δ relaxation (rotational polarization of the hydrated water), slow relaxation (reorientation of the HB network water), fast relaxation (rotation of the non-HB water), and intermolecular stretching vibration (hindered translation of water). On the basis of this analysis, we revealed that the hydrated water surrounding the glucose molecules exhibits a mono-modal relaxational dispersion with 2-3 times slower relaxation times than unperturbed bulk water and with a hydration number of around 20. Furthermore, other species of water with distorted tetrahedral HB water structures, as well as increases in the relative proportion of non-HB water molecules which have a faster relaxation time and are not a part of the surrounding bulk water HB network, was found in the vicinity of the glucose molecules. These clearly point to the HB destructuring effect of saccharide solutes in aqueous solution. The results, as a whole, provide a detailed picture of glucose-water and water-water interactions in the vicinity of the glucose molecules at various time scales from sub-picosecond to hundreds of picoseconds.