Tadao Nagatsuma

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.

120-GHz Tx/Rx chipset for 10-Gbit/s wireless applications using 0.1 /spl mu/m-gate InP HEMTs

This paper describes the development of a InP-HEMT MMIC chipset for 120-GHz wireless applications. The transmitter chip includes a frequency doubler for carriers, an ASK modulator, an RF band-pass filter, and a power amplifier. The receiver chip includes a low-noise amplifier and an ASK demodulator. A back-to-back test of the chipset has shown it to be fully functional at 10-Gbit/s data rate with BER=e-12 at -45.7-dBm input power of the receiver chip. To our knowledge, this is the first report of the development of highly integrated MMIC chipset operating at 120 GHz for wireless data communication.

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.

Photodiode-integrated microstrip antenna array for subterahertz radiation

The radiation characteristics of subterahertz (sub-THz) electromagnetic waves emitted from an antenna array integrated with photodiodes are investigated. The element of the fabricated array antenna was a 300-GHz microstrip antenna integrating a uni-traveling carrier photodiode. It was observed that the beamwidth of a 3 /spl times/ 1 antenna array is about half that of the single microstrip antenna. We also confirmed that the radiation direction changed by 20/spl deg/ when 2/spl pi//5 of phase difference was added to the input optical signal for each antenna element. These results demonstrated that sub-THz waves emitted by each element of the array were coherently superimposed and the power combining of the sub-THz radiation occurred in the microstrip antenna array. The measured output power of each radiation element is about 120 /spl mu/W, and a total output power of 1 mW can be estimated for a fabricated 3 /spl times/ 3 array in an ideal radiation condition.

Millimeter-wave photonics for 10-Gbit/s wireless links

We presented a gigabit/s wireless link that uses 120-GHz MMW photonic techniques for the MMW generation, modulation and emission. We have succeeded in wireless data transmission at up to 10 Gbit/s. We also described a low-cost MMW wireless link that uses FP laser and PD bias modulation for MMW generation and modulation, respectively. This link transmitted data at up to 1.25 Gbit/s. We believe that gigabit/s wireless communication will become widespread using these MMW photonic techniques.

Gigabit impulse radio link using photonic signal-generation techniques

A gigabit wireless link system with an impulse radio scheme is presented. The link system employs a photonic-impulse signal-generation technique in the transmitter and a wideband down-conversion based on a square-law detection in the receiver. An impulse signal with a full-width-at-half-maximum of 22 ps was generated at a bit rate of 1.485 Gb/s. A data signal was regenerated from the impulse signal propagated in the free space. Error-free transmission with a word length of 2/sup 15/-1 was obtained at the received power of -36 dBm. High-definition television data transmission has also been successfully conducted.

Characterization of Micromachined Coplanar Waveguides on Silicon up to 300 GHz

We report the design, fabrication and characterization of a novel micromachined coplanar waveguide on high-resistivity silicon for millimeter-wave applications up to 300 GHz. Its high frequency characteristics are achieved using 10-¿m deep V-grooves and thick and abrupt sidewalls metallization of up to 10 ¿m. We present the loss and dispersion results up to 300 GHz measured using a time domain technique and compare them to those of coplanar waveguides on other important millimeter wave substrates.

Sub-Terahertz Wireless Communications Technologies

This paper presents a 10-Gb/s wireless link system that uses a 120-GHz-band sub-terahertz electro-magnetic waves. In the transmitter, photonic techniques are used for generation, modulation, and emission of the sub-THz signals, while the receiver is composed of all-electronic devices using InP-HEMTs

High-speed and high-output-power unitraveling-carrier photodiodes

The uni-traveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key to achieving excellent high-speed and high-output characteristics simultaneously. A record 3-dB bandwidth of 310 GHz and a millimeter-wave output power of over 20 mW at 100 GHz have already been achieved. The superior capability of the UTC-PD for generating very-large high-bit-rate electrical signals as well as a very-high output power in millimeter/sub-millimeter ranges can innovate various systems, such as broadband optical communications systems, wireless communications systems, and high-frequency measurement systems. Achievements include photoreceivers of up to 80 Gbit/s, DEMUX operations using an integrated optical gate of up to 320 Gbit/s, and a 10-Gbit/s millimeter-wave wireless link at 120 GHz. Also achieved has been high-power millimeter generation of 17 mW at 120 GHz with a waveguide-output UTC-PD module, considered for use in the photonic-local system of radio telescopes.

Generation of Low-phase Noise and Frequency-tunable Millimeter-/terahertz-waves Using Optical Heterodyning Techniques with Uni-traveling Carrier Photodiodes

This paper describes recent advances in the generation of millimeter- and terahertz-waves based on optical heterodyning techniques. Low-phase noise, wide frequency tunability, and high output power are most important issues in many applications. Basic component technologies such as an optical sideband generator, photonic light-wave circuits for signal processing, and antenna-integrated photodiode modules, and their applications to high-performance measurement and communications are presented