We experimentally evaluated transmission characteristics of 120-GHz-band close-proximity wireless link that employs a split-ring resonator (SRR) millimeter-wave (MMW) absorber integrated on planar slot antennas in 120-GHz-band close-proximity wireless links. We fabricated the SRR MMW absorber made of a 0.28-μm-thick TaN film on a quartz substrate, and integrated it on planar single slot antennas. When the TaN SRRs are not integrated on the planar slot antennas, multiple reflections between the two antennas occur, and a >10-dB fluctuation of S21 at 100-140GHz is observed. When the TaN SRRs are integrated on the planar antennas, the fluctuation of S21 is suppressed to be 3.5dB at 100-140GHz. However, the transmittance of the close-proximity wireless link decreases by integrating TaN SRRs on the planar slot antenna because of reflection at the quartz substrate surface. The integration of the radiator that is composed of single SRR with two capacitors just above the slot antenna increased S21 by 3.5dB at 125GHz. We conducted a data transmission experiment over a close-proximity wireless link that employs radiator-and-TaN-SRR-integrated slot antennas for Tx and Rx, and succeeded to transmit 10-Gbit/s data over the close-proximity wireless link for the first time.

This paper presents a 120-GHz-band split ring resonator (SRR) bandstop filter whose insertion loss can be controlled by coupling another lattice pattern substrate. The SRR bandstop filter and lattice pattern substrate is composed of 200-µm-thick quartz substrate and 5-µm-thick gold patterns. S21 of the SRR bandstop filter is -37.8 dB, and its -10-dB bandwidth is 115-130 GHz. S21 of the SRR bandstop filter changes to -4.1 dB at 125 GHz by arranging the lattice pattern substrate in close proximity to the SRR stopband filter, because coupling between the SRR and the lattice pattern occurs when the SRR and lattice pattern are opposed in close proximity. It was found that 10 Gbit/s data transmission can be achieved by setting the lattice pattern substrate just above the SRR bandstop filter with a spacer thickness of 50 µm, even though data transmission is impossible when only the SRR bandstop filter is inserted between the transmitter and the receiver.

This paper proposes the absorber integrated planar array antenna for a 120-GHz-band close proximity wireless system. It consists of split-ring resonators (SRRs) patterned on a quartz substrate and a plate-laminated-waveguide planar slot array antenna. Precise alignment and multiple reflection between Tx-Rx antenna become severe problem as the carrier frequency increases, such as >100GHz. The absorber integrated planar slot array antenna solves these problems. We designed a SRR unit cell that acts as a millimeter-wave (MMW) absorber, and the simulated S11 of the SRR absorber at 125GHz is -37dB. The use of the SRR absorber on the planar slot antenna suppresses the multiple reflection between Tx and Rx antennas, however the transmission loss between Tx and Rx antennas increases. We changed the conductivity and cell size of 2×3 element SRR unit cells directly above the waveguide slots in order to make them act as an SRR director, and the use of the SRR director improved the transmission loss by 2.7dB. We simulated the transmission characteristics of a close-proximity wireless system using the SRR absorber integrated planar slot antennas. The simulated fluctuation of S21 in the 120-130GHz band is below 2.6dB, and the delayed waves that come from the multiple reflection between Tx and Rx antennas were suppressed.

An NRD guide transmitter and a receiver were developed for a wireless multi-channel TV-signal distribution system at 60 GHz. The main emphasis was placed on a band-widening technique of the NRD guide beam-lead diode mount based on an electromagnetic field simulator, where each dimension of the beam lead diode mount was optimized. The agreement between the simulation and measurement is quite satisfactory. The up-converter fabricated by assembling a band-pass filter and a Schottky barrier diode mount has a good linearity as well as a flat output power of 2 dBm on the average over a bandwidth of at least 2 GHz. Moreover, the down-converter has a flat conversion loss performance of less than 7 dB in the same bandwidth. An NRD guide transmitter and a receiver characterized by small size and high performance were fabricated and successfully employed for the wireless distribution of TV signals for more than 100 channels.

Full-duplex transmission of 60.0 GHz and 59.6 GHz millimeter-wave (mm-wave) signals of 155.52-Mbit/s differential phase shift keying (DPSK) data, radio-on-fiber (ROF) signals over 25-km-long standard single-mode fibers (SMFs) is experimentally demonstrated for the first time using a single 2-RF-port electroabsorption transceiver (EAT). The simplification of base stations (BSs) is strongly required to realize cost-effective and high-reliability mm-wave wireless access. This single EAT detects a C-band ROF signal modulated by a mm-wave downlink signal and simultaneously modulates the L-band optical carrier by a mm-wave uplink signal. The BS mainly consists of the EAT, leading to a simple and low-cost BS. Optical pilot tones and optical bandpass filters are used for photonic downconversion and photonic upconversion, to convert frequencies between mm-wave signals and intermediate frequency (IF) signals in the optical domain. With the use of optical conversions, these signals have no significant fading problems. The simultaneous transmission of both up- and downlinks has been achieved with the BER of less than 10-9. Also the fading problems due to the fiber dispersion of photonic conversions are analyzed mathematically in this paper. The single-EAT BS will become a promising candidate for a ROF access system.

A simple configuration for millimeter-wave fiber-wireless transmission, with remote local-oscillator (LO) delivery from the central office, both for the uplink and for the downlink, and a simple, cost-effective, base-station solution is proposed. Under the assumption of using commercially available components and a conventional single-mode fiber (with dispersion of 17 ps/nm/km at 1.55 µm), our numerical results show that, with a laser linewidth of 150 MHz, a laser power of 0 dBm and an optical gain of only 6 dB, it is possible to transmit, without repeaters, data rates of 622 Mbit/s across about 18 km at a bit-error-rate of 10-9. By increasing the optical gain to 24 dB, the link length can be increased to approximately 67 km for a laser linewidth of 75 MHz and to 78 km for a laser linewidth 1 MHz.

Developments in new frequency bands for wireless communications make a broadband channel for new services possible. Great effort has been made researching and developing broadband wireless communication in the 60-GHz millimeter-wave band since the early 1990s. In this paper, we design an ATM (asynchronous transfer mode)-based indoor millimeter-wave wireless local area network (WLAN) that supports multimedia transmissions and focus on the wireless access topic for implementation of wireless ATM. We propose an integrated multimedia transmission protocol, based on the MAC (medium access control) protocol, called RS-ISMA (reservation-based slotted idle signal multiple access). It supports CBR (constant bit rate), VBR (variable bit rate), ABR (available bit rate) and UBR (unspecified bit rate) transmissions and provides QoS (quality of service)-dependent adaptive retransmissions. An RS-ISMA-based prototype full-duplex indoor high-speed WLAN in the 60-GHz band was developed.

The architecture design and test results of simulation facility named millimeter-wave Test Bed has been described. Contrast with a millimeter-wave sounder, the Test Bed proposed in this paper can characterize radio channels, received signals, target reflections and radio link performance at the millimeter-wave band of 60 GHz. For fixible simulation and analysis of the performances of newly designed millimeter-wave systems, major digital signal processing parts like a sophisticate waveform generator and an analyzer, a modulator, a demodulator, an encoder, a decoder, an equalizer in the Test Bed are implemented by a software using SPW. This software based Test Bed can be used as a "deign tool" for the simulation of the millimeter-wave communication systems very flexibly without hardware modification in different specifications. The Test Bed consists of a millimeter-wave transmitter, a receiver of 60 GHz, 1.95 GHz up/down converter as IF module and a digital signal processing module. The I/Q vector modulator and demodulator with a video bandwidth of 37.5 MHz in the Test Bed can simulate or test the application of high data rate communication systems of short distance.

For quasi millimeter-wave and millimeter-wave high-speed wireless communications over wireless LANs and wireless ATMs, narrow beam antennas have been shown to provide high transmission quality by suppressing the troublesome multipath effect. However, the diameter of sector antennas needed to create the narrow beams rapidly increases with the sector number. In addition, the cylindrical shape of typical sector antennas does not suit portable terminals. This paper shows a methodology for designing planar sector antennas that overcomes these problems. The proposed antenna uses two kinds of beams and the antenna gains are equalized in all sectors. The antenna is developed as a 4-beam subarray fed by a planar Butler matrix circuit. The design method of the subarray and an evaluation of its characteristics in the 20 GHz band are discussed.