A new mobility model dependent upon electron concentration is presented for studying the screening effect on ionized impurity scattering. By coupling this model with the drift-diffusion and Hartree models, the effects of self-consistent and quasi-equilibrium screening on carrier transport in heavily doped systems are revealed for first time. The transport mechanism is found to be dominated by the electron-concentration-dependent mobility, and transconductance is shown to be determined by effective mobility and changes from degraded to enhanced characteristics with electron concentration modulation.

A unified model for frequency-dependent characteristics of transconductance and output resistance is presented that incorporates the dynamics of quasi-Fermi levels. Using this model, multiple-frequency dispersion and pulse-narrowing phenomena in GaAs MESFETs are demonstrated based on the drift-diffusion transport theory and a Schockley-Read-Hall-type deep trap model, where rate equations for multiple trapping processes are analyzed self-consistently. It is shown that the complex frequency dependence is due to both spatial and temporal effects of multiple traps.

In this paper, the influence of surface waves on the characteristics of on-glass antennas is clarified to enable appropriates design of C-band automotive on-glass antennas. Composite glasses are used in automotive windshields. These automotive composite glasses are composed of three layers. First, the surface wave properties of composite glass are investigated. Next, the effects of surface waves on the reflection coefficient characteristics of on-glass antennas are investigated. Finally, the antenna placement to reduce surface wave effect will be presented. Electromagnetic field analysis of a dipole antenna placed at the center of a 300mm × 300mm square flat composite glass showed that the electric field strength in the glass had ripples with the half wavelength period of the surface waves. Therefore, it was confirmed that standing waves are generated because of these surface waves. In addition, it is confirmed that ripples occur in the reflection coefficient at frequencies. Glass size is divisible by each of those guide wavelengths. Furthermore, it was clarified that the reflection coefficient fluctuates with respect to the distance between the antenna and a metal frame, which is attached to the end face in the direction perpendicular to the thickness of the glass because of the influence of standing waves caused by the surface waves; additionally, the reflection coefficient gets worse when the distance between the antenna and the metal frame is an integral multiple of one half wavelength. A similar tendency was observed in an electric field analysis using a model that was shaped like the actual windshield shape. Because radiation patterns also change as a result of the influence of surface waves and metal frames, the results imply that it is necessary to consider the actual device size and the metal frames when designing automotive on-glass antennas.

This paper proposes a transparent glass quartz antenna for 5G-millimeter-wave-connected vehicles and clarifies the characteristics of signal reception when the glass antennas are placed on the windows of a vehicle traveling in an urban environment. Synthetic fused quartz is a material particularly suited for millimeter-wave devices owing to its excellent low transmission loss. Realizing synthetic fused quartz devices requires accurate micromachining technology specialized for the material coupled with the material technology. This paper presents a transparent antenna comprising a thin mesh pattern on a quartz substrate for installation on a vehicle window. A comparison of distributed transparent antennas and an omnidirectional antenna shows that the relative received power of the distributed antenna system is higher than that of the omnidirectional antenna. In addition, results show that the power received is similar when using vertically and horizontally polarized antennas. The design is verified in a field test using transparent antennas on the windows of a real vehicle.