The use of the higher-order modulation format and narrower channel bandwidth can enhance the spectral efficiency of photonic networks. However, such spectrally efficient schemes cannot be utilized when the large margin is required to tolerate uncertainties in the performance of system components. Furthermore, the disaggregation of optical transmission system increases the required margin. In this paper, we propose highly spectrally efficient network architecture, where the required margin is minimized by transmission-quality-aware modulation-order/channel-bandwidth assignment based on optical performance monitoring. Up to 82% improvement in spectral efficiency for 400-Gbps DP-QPSK/DP-16QAM signals is confirmed through transmission experiments and network simulations.

This paper describes pulse waveform distortion by a high-power GaN amplifier and a method for reducing it in a solid-state radar that performs pulse compression. When a pulse signal is input to the amplifier, the output pulse waveform differs from the input form because of the influences of nonlinearity and transient response, which are remarkable at the time of rise and fall when the amplitude has a temporal slope. In the measurement results, the temporal slope and the pulse width increased by 79.6% and 1.5%, respectively, compared with the input waveform. On processing the received signal, these influences degraded the signal-to-noise ratio after pulse compression by about 5 dB. In the proposed method, these influences were reduced by adding a dummy signal before and after the desired signal. This method is advantageous in that it does not require the addition of a feedback circuit for distortion compensation and it is not easily influenced by changes in the signal settings and the ambient temperature.

This paper evaluates performance of digital coherent receivers that executes partial-response spectrum shaping and MLSE to mitigate the inline-spectrum-narrowing impairment caused by traversing multiple optical nodes in photonic networks. Extensive computer simulations confirm that the maximum transmission distances and hop counts of DP 4-QAM and 16-QAM signals in highly dense WDM networks are substantially extended.

Recently, radar absorbent materials (RAM) with various characteristics have been developed according to applications. Since it is difficult to satisfy the required performance when errors occur in them during fabrication, it is necessary to have robustness of the electrical material constant. This paper shows robust design of RAM with broadband characteristics. The change magnification of relative permittivity is set to 0.3 of the limit value and that of thickness is set to 0.05. As a result, even when the design variables take the worst values with respect to the objective function, it is possible to realize broadband characteristics of relative bandwidth of 164.3% with respect to wave-absorption amount (Wa) of 10 dB.

This paper presents a method to estimate the Angle of Arrival (AOA) for incident waves, using an RF-based interferometric monopulse technique. We used an AOA network to yield a weight function for the received signals, in which the phase of the received signals for each element is delayed in accordance with the coordinate of the elements using the differing lengths of microstrip transmission lines. Based on electromagnetic field analysis and experimental results, it is clarified that the proposed method achieves a high degree of accuracy for AOA estimation.

This paper discusses a list Viterbi equalizer (LVE) with liner channel interpolation (LCI), which can cope with time and frequency selective channels, i.e., doubly-selective channels of acoustic communications. Features of the proposed LVE are (1) to cope with delay spread over 127 bits with small computational complexity, (2) to cope with time selective channels by simple channel estimation and its LCI and (3) to cope with non-minimum phase condition by metric-criteria combining. Next, computer simulation results show that the proposed LVE has better performance on doubly-selective channels than a decision-feedback equalizer employing recursive least square (RLS) algorithm. Finally, field evaluation results confirm that the proposed LVE is suitable for acoustic communications environment.

Inductive coupled coil is an antenna structure that can easily realize multiple resonant frequencies with planar structure for MHz band wireless capsule endoscopic (WCE) communication. However, since one resonant frequency is generated by one coil, the antenna size is large when designing multi-band antennas. In this paper, the antenna matching circuit is modified to be a series circuit with an LC tank so that one coil can generate two resonant frequencies. For the receiving antenna, this improvement can reduce half the number of coils and achieve smaller antenna size. For the transmitting antenna that is difficult to use multiple coils due to the strict size constraints of the WCE, this improvement can achieve two resonant frequencies through one coil. In order to evaluate the feasibility and whether this improvement will reduce the antenna transmission performance, a single-coil dual-band antenna operating in the MHz band is designed and manufactured, and the simulated and measured reflection and transmission coefficients are evaluated by a biological tissue equivalent phantom. By comparing with the previously proposed antenna results, it can be known that the transmission performance is not deteriorated, indicating that the improvement is feasible for the WCE transmitting and receiving coil antennas.

This paper pursuits a possibility of fully polarimetric and three-dimensional (3-D) imaging by Holographic Synthetic Aperture Radar Tomography (HoloSAR). HoloSAR is 3-D extension of Circular Synthetic Aperture Radar (CSAR) along the vertical direction whose trajectory is a circle in a horizontal plane. By adding fully polarimetric capability to HoloSAR, it becomes a perfect 3-D imaging radar system which reveals scattering mechanisms from object through scattering power decomposition. This paper attempts to achieve such a prototype system in an anechoic chamber. The experimental result successfully yielded a 3-D image reconstruction of objects with exhibiting polarimetric scattering mechanism.