Masahiro Mimura

A direct conversion receiver utilizing a novel FSK demodulator and a low-power-consumption quadrature mixer

Two novel technologies of direct conversion are introduced. One is an FSK demodulator based on a new architecture, and the other is a quadrature mixer for direct conversion. The FSK demodulator is composed of relative 90 degrees phase shifters and frequency multipliers suitable for digital circuit implementation, and it has shown a wide allowance for offsets of the local frequency. In designing the quadrature mixer IC, structural and numerical optimization was carried out for low power consumption. The demodulator and the quadrature mixer, including the surrounding circuits, have been integrated. In order to realize smaller size and advanced performance, the authors adopt appropriate silicon processes for each of these two ICs. The FSK direct conversion radio data receiver with a bit rate of 1200 b/s developed utilizing the above ICs has achieved excellent performance, as expected.<<ETX>>

Improved method for evaluating antenna performance in mobile environment with consideration of polarization and phase

The paper presents an improved method for evaluating antenna performance in a multipath propagation environment. It demonstrates, theoretically and experimentally, that by using polarization and phase terms of the incident field and the antenna system in the evaluation of the antenna effective gain (AEG), the AEG can be evaluated more efficiently as compared with the conventional method. First, a theoretical expression of the received power is given by using the open-circuit voltage at the antenna terminals, in which both the polarization and the phase of the incident field and antenna gain patterns are explicitly used. Secondly, a newly developed system for the measurement of field parameters, such as polarization and phase as well as amplitude, is introduced. Thirdly, incident field parameters measured in urban and suburban areas of Tokyo are described. It was confirmed that major incident waves were counted in up to five or six directions at a mobile terminal and their polarizations and phases were different depending on the direction of incidence. Also, measurement of the antenna gain patterns of the latest personal digital cellular handset at a talk position finds the dependence of the AEG on polarization and phase, which were significantly varied by the body effect. Finally, the AEG is evaluated based on the method introduced here, and its usefulness is compared with that of the conventional method.