A new half-power beam width (HPBW) base station (BS) antenna is described for use in 26 GHz- and 38 GHz-band point-to-multipoint (P-MP) fixed wireless access (FWA) systems which is narrower than the conventional design, and which efficiently meets the prescribed carrier-to-thermal noise power ratio (C/N) quality requirements. This development results in a reduction in antenna volume and the installation costs of the system. The validity of the new design in terms of C/N, carrier-to-interference signal power ratio (C/I) performance and the visibility of the propagation path are estimated.

This paper demonstrates 300GHz terahertz wireless communication using CMOS transmitter (TX) and receiver (RX) modules targeting sixth-generation (6G). To extend communication distance, CMOS modules with WR-3.4 waveguide interface and a high-gain antenna of 40dBi Cassegrain antenna are designed, achieving 36Gbps throughput at a 1m communication distance. Besides, in order to support orthogonal frequency-division multiplexing (OFDM), a self-heterodyne architecture is introduced, which effectively cancels the phase noise in multi-carrier modulation. As a proof-of-concept (PoC), the paper successfully demonstrates real-time video transfer at a 10m communication distance using fifth-generation (5G) based OFDM at the 300GHz frequency band.

Cost down of millimeter wave components, especially antenna duplexer, is a key for spreading millimeter wave communication systems. An excellent cost-performance antenna duplexer is proposed. It consists of two E-plane filters and a wave-guide circulator. The performance fluctuations due to manufacturing accuracies are studied by simulations and experiments. These results are very useful for cost-down of the practical duplexer without performance degradation.

The MU radar of Japan is one of important candidates for providing accurate ground truth for the TRMM precipitation radar. It can provide the dropsize distribution data together with the background atmospheric wind data with high accuracy and high spatial resolution. Special observation scheme developed for TRMM validation using the MU radar is described, and preliminary results from its test experiment are shown. The high-resolution MU radar data are also used in numerical simulations to validate the rain retrieval algorithm for the TRMM PR data analysis. Among known sources of errors in the rain retrieval, the vertical variability of the dropsize distribution and the partial beam-filling effect are examined in terms of their significance with numerical simulations based on the MU radar data. It is shown that these factors may seriously affect the accuracy of the TRMM rain retrieval, and that it is necessary to establish statistical means for compensation. However, suggested means to improve the conventional α-adjustment method require careful treatment so that they do not introduce new sources of errors.

A slot pair array using a post-wall waveguide is a promising candidate for a Fixed Wireless Access (FWA) sector antenna to be used in a base station. This array is formed by a traveling wave antenna, and therefore its main beam direction varies with frequency. To overcome this difficulty, we propose a new structure that comprises of a cosecant array and an additional Talor array. This structure can fix the main beam in a constant direction whilst maintaining a cosecant radiation pattern. We conducted an investigation based on an array factor, and the validity of the method was confirmed by experiment.