This invited paper is dedicated to introduce recent activities of Japanese microwave industries. 7 topics are introduced from major microwave companies in Japan. All topics are from invited talks in 2014 Asia-Pacific microwave conference (APMC2014) held in Sendai, November, 2014.

Implementation of RFID reader/writer on software defined radio is studied in this paper. The target RFID is ISO18000-3 mode 2 which has 8 reply channels for simultaneous communication with 8 different RFID tags. In the software defined radio architecture, the 8 reply channels are sampled at a single A/D converter and separated by digital down converters, whereas conventional RFID architecture has redundant 8 parallel analog down converters. A novel multi-stage transmultiplexing digital down converter is proposed for efficient implementation of multi-channel digital down converter. Moreover the proposed architecture is implemented on a FPGA evaluation board, and validity of the system is confirmed on a real hardware. The proposed architecture can be applied to multi-channel receiver for dynamic spectrum system in the cognitive radio.

This paper describes our new technology for creating a highly productive 0. 1 µm gate InGaP/InGaAs HEMT with a GaAs substrate for a millimeter-wave MMIC. We applied a phase-shifting photo lithographic technique and sidewall deposition/etching process to fabricate a 0. 1 µm gate electrode. The fabricated HEMTs showed excellent high-frequency performance; An MSG exceeding 10 dB at 60 GHz. We also fabricated a 60 GHz band, four-stage low-noise amplifier MMIC and demonstrated its superior performance (Gain= 27 dB and NF= 3. 1 dB @61 GHz). These results strongly suggest that our InGaP/InGaAs HEMTs technologies are highly applicable for millimeter-wave applications.

We studied a 0.15-µm InGaP/InGaAs/GaAs pseudomorphic HEMT operating under a negative drain bias, using a parameter extraction technique based on an analytical parameter transformation. The bias-dependent data of smallsignal equivalent circuit elements was obtained from Sparameters measured at up to 62.5 GHz at various bias settings. We then described the intrinsic part of the device using a new empirical large-signal model in which charge conservation and dispersion effects were taken into consideration. As far as we know, this is the first report to clarify the behavior of a HEMT operating under negative drain bias. We included our largesignal model in a commercially-available harmonic-balance simulator as a user-defined model, and designed a 60 GHz MMIC oscillator. The fabricated oscillator's characteristics agreed well with the design calculations.

This paper presents the fabrication and evaluation of a 60 GHz fully integrated MMIC one-chip receiver based on pseudomorphic InGaP/InGaAs/GaAs HEMT technology. The receiver consists of two 2-stage low-noise amplifiers (LNAs), a single-balanced active-gate mixer, a local oscillator (LO), and a buffer amplifier for the LO. The receiver has a conversion gain of greater than 17 dB from 60.2 GHz to 62.3 GHz, and the maximum conversion gain is 20 dB at 62.2 GHz. The noise figure of receiver is less than 6 dB in the IF range between 100 MHz and 1 GHz for a 61.536 GHz LO frequency, and the minimum noise figure is 4.9 dB at 1 GHz IF.

This paper describes millimeter-wave HEMT oscillators developed to operate at 50 GHz and above. To determine the feasibility of using HEMTs for millimeter-wave oscillators, we measured and compared the low-frequency noise characteristics of both HEMT and GaAs MESFET devices and found them to have nearly identical characteristics. We also estimated the S parameters of a HEMT biased at Vds-3V and Ids5 mA for an equivalent circuit study. The oscillators consisted of a microstrip line resonator, a matching circuit, and a bias circuit. The output power and oscillation efficiency for the 60-GHz HEMT oscillator was 2.6dBm and 9.5%, and 2.8dBm and 6.4% for the 50-GHz oscillator. The efficiencies of these HEMT oscillators are higher than that of GaAs MESFET oscillators at millimeter-wave frequencies.

The dramatic growth in wireless data traffic has triggered the investigation of fifth generation (5G) wireless communication systems. Small cells will play a very important role in 5G to meet the 5G requirements in spectral efficiency, energy savings, etc. In this paper, we investigate low complexity millimeter-wave communication systems with uniform circular arrays (UCAs) in line-of-sight (LOS) multiple-input multiple-output (MIMO) channels, which are used in fixed wireless access such as small cell wireless backhaul for 5G. First, we demonstrate that the MIMO channel matrices for UCAs in LOS-MIMO channels are circulant matrices. Next, we provide a detailed derivation of the unified optimal antenna placement which makes MIMO channel matrices orthogonal for 3×3 and 4×4 UCAs in LOS channels. We also derive simple analytical expressions of eigenvalues and capacity as a function of array design (link range and array diameters) for the concerned systems. Finally, based on the properties of circulant matrices, we propose a high performance low complexity LOS-MIMO precoding system that combines forward error correction (FEC) codes and spatial interleaver with the fixed IDFT precoding matrix. The proposed precoding system for UCAs does not require the channel knowledge for estimating the precoding matrix at the transmitter under the LOS condition, since the channel matrices are circulant ones for UCAs. Simulation results show that the proposed low complexity system is robust to various link ranges and can attain excellent performance in strong LOS environments and channel estimation errors.