This paper presents an ultra-wideband (UWB) bandpass filter using a combination of broadside-coupled structure and lumped-capacitor-loaded shunt stub resonator. The broadside-coupled microstrip-to-coplanar waveguide structure provides an ultra-wide bandpass filtering operation and keeps a good stopband at lower frequencies from DC at the same time. The lumped-capacitor-loaded shunt stub resonator creates two transmission zeros (attenuation poles which can be located at the outsides of the two bandedges of the UWB bandpass filter to improve the out-band performance by selecting a suitable combination of the length of the shunt stubs and the capacitance of the loaded chip capacitors. The filter was designed based on electromagnetic simulation for broadside-coupled structure, microwave circuit simulation and experiments for determining the transmission zeros. The filter was fabricated on a one-layer dielectric substrate. The measured results demonstrated that the developed UWB bandpass filter has good performance: low insertion loss about 0.46 dB and low group delay about 0.26 ns at the center of the passband and very flat over the whole passband, and less than -10 dB reflection over the passband. The implemented transmission zeros, particularly at the low frequency end, dramatically improved the out-band performance, leading the filter satisfy the FCC's spectrum mask not only for indoor but also for outdoor applications. These poles improved also the skirt performance at both bandedges of the filter. A lowpass filter has been also introduced and integrated with the proposed bandpass filter to have a further improvement of the out-band performance at the high frequency end. The filters integrated with lowpass section exhibit excellent filter performance: almost satisfying the FCC's spectrum mask from DC to 18 GHz. The developed UWB bandpass filter has a compact size of 4 cm1.5 cm, or 4.8 cm1.5 cm with lowpass section implemented.

This paper presents indoor and outdoor experiments that confirm 4-Gbps throughput based on 400-MHz bandwidth transmission when applying carrier aggregation (CA) with 4 component carriers (CCs) and 4-by-4 single-user multiple-in multiple-out multiplexing (MIMO) in the 15-GHz frequency band in the downlink of 5G cellular radio access. A new radio interface with time division duplexing (TDD) and radio access based on orthogonal frequency-division multiple access (OFDMA) is implemented in a 5G testbed to confirm ultra-high speed transmission with low latency. The indoor experiment in an entrance hall shows that the peak throughput is 4.3Gbps in front of the base station (BS) antenna where the reference signal received power (RSRP) is -40dBm although the channel correlation at user equipment (UE) antenna is 0.8. The outdoor experiment in an open-space parking area shows that the peak throughput is 2.8Gbps in front of a BS antenna with a high RSRP although rank 2 is selected due to the high channel correlation. The results also show that the average throughput of 2Gbps is achieved 120m from the BS antenna. In a courtyard enclosed by building walls, 3.6Gbps is achieved in an outdoor-to-outdoor environment with a high RSRP and in an outdoor-to-indoor environment where the RSRP is lower due to the penetration loss of glass windows, but the multipath rich environment contributes to realizing the low channel correlation.

In this paper, a notch-band implemented UWB bandpass filter was proposed. The filter was realized by integrating a full ultra-wideband bandpass filter using broadside coupling structure with a bandstop filter using in-line open stub. The in-line open stub was installed in the removed area in the broadside coupled microstrip conductors, which demonstrated a narrow notch-band performance. The proposed filters were designed based on the electromagnetic simulation and fabricated using a wet etching system. Parameter study of length dependence of the notch-band was carried out. The first resonant frequency of the in-line stub appears when the length is approximately equal to one quarter of the guided wavelength. Based on this fact, the notch-band can be adjusted to almost any specified band in the UWB passband. A three-section notch-band implemented filter demonstrated good characteristics: its full frequency bandwidth form 2.8 GHz to 10.2 GHz, good insertion loss of 0.6 dB and 1.0 dB at the centers of the first and second bands respectively, and flat and small group delay of less than 0.40 ns over main pass band, and a large attenuation stopband about 55 dB at 5.63 GHz. A lowpass filter was also introduced in order to improve the out-band performance, by which the measured results show an excellent attenuation better than 30 dB from 10.4 GHz to 17.8 GHz.

This paper describes the results of outdoor mobility measurements and high-speed vehicle tests that clarify the 4-by-8 multiple-input multiple-output (MIMO) throughput performance when applying distributed MIMO with narrow antenna-beam tracking in a 28-GHz frequency band in the downlink of a 5G cellular radio access system. To clarify suitable transmission point (TP) deployment for mobile stations (MS) moving at high speed, we examine two arrangements for 3TPs. The first sets all TPs in a line along the same side of the path traversed by the MS, and the other sets one TP on the other side of the path. The experiments in which the MS is installed on a moving wagon reveal that the latter deployment case enables a high peak data rate and high average throughput performance exhibiting the peak throughput of 15Gbps at the vehicle speed of 3km/h. Setting the MS in a vehicle travelling at 30km/h yielded the peak throughput of 13Gbps. The peak throughput of 11Gbps is achieved at the vehicle speed of 100km/h, and beam tracking and intra-baseband unit hand over operation are successfully demonstrated even at this high vehicle speed.

This paper presents outdoor field experimental results to clarify the 4-by-4 multiple-input multiple-output (MIMO) throughput performance when applying joint transmission (JT) and distributed MIMO to the 15-GHz frequency band in the downlink of a 5G cellular radio access system. Experimental results for JT in a 100m × 70m large-cell scenario show that throughput improvement of up to 10% is achieved in most of the area and the peak data rate is improved from 2.8Gbps to 3.7Gbps. Based on analysis of the reference signal received power (RSRP) and channel correlation, we find that the RSRP is improved in lower RSRP areas, and that the channel correlation is improved in higher RSRP areas. These improvements contribute to higher throughput performance. The advantage of distributed MIMO and JT are compared in a 20m × 20m small-cell scenario. The throughput improvement of 70% and throughput exceeding 5 Gbps were achieved when applying distributed MIMO due to the improvement in the channel correlation. When applying JT, the RSRP is improved; however the channel correlation is not. As a result, there is no improvement in the throughput performance in the area. Finally, the relationship between the transmission point (TP) allocation and the direction of user equipment (UE) antenna arrangement is investigated. Two TP positions at 90 and 180deg. from each other are shown to be advantageous in terms of the throughput performance with different direction of UE antenna arrangement. Thus, we conclude that JT and distributed MIMO are promising technologies for the 5G radio access system that can compensate for the propagation loss and channel correlation in high frequency bands.

This paper evaluates a variety of key 5G technologies such as base station (BS) massive multiple-input multiple-output (MIMO) antennas, beamforming and tracking, intra-baseband unit (BBU) hand over (HO), and coverage. This is done in different interesting 5G areas with a variety of radio conditions such as an indoor office building lobby, an outdoor parking area, and a realistic urban deployment of a 5G radio access system with BSs installed in buildings to deploy a 5G trial area in the Tokyo Odaiba waterfront area. Experimental results show that throughput exceeding 10Gbps is achieved in a 730MHz bandwidth using 8 component carriers, and distributed MIMO throughput gain is achieved in various transmission point deployments in the indoor office building lobby and outdoor parking area using two radio units (RUs). In particular, in the outdoor parking area, a distinct advantage from distributed MIMO is expected and the distributed MIMO gain in throughput of 60% is achieved. The experimental results also clarify the downlink performance in an urban deployment. The experimental results show that throughput exceeding 1.5Gbps is achieved in the area and approximately 200 Mbps is achieved at 500m away from the BS. We also confirm that the beam tracking and intra-BBU HO work well compensating for high path loss at 28-GHz, and achieve coverage 500m from the BS. On the other hand, line of sight (LoS) and non-line-of sight (N-LoS) conditions are critical to 5G performance in the 28-GHz band, and we observe that 5G connections are sometimes dropped behind trees, buildings, and under footbridges.