10-Gbit/s wireless data transmission using 120-GHz millimeter-wave (MMW) photonic technologies is presented. For such high-data-rate transmission, we have newly developed a planar broadband receiver that employs a > 200-GHz Schottky diode and a slot-ring antenna with a 10-dB bandwidth of 30 GHz. The receiver achieves a high video sensitivity of 190 mV/mW at 120 GHz due to its optimized data output circuit. The MMW wireless link using the receiver and photonic transmitter has data transmission bandwidth of 8.5 GHz, and succeeded in 10-Gbit/s data transmission, which is the fastest ever achieved through a MMW wireless link.

This paper describes a very accurate method of estimating the return-path-capacitance and validates the estimation based on low-error measurements for electric-field intrabody communication. The return-path capacitance, Cg, of a mobile transceiver is estimated in two ways. One uses the attenuation factor in transmission and capacitance, Cb, between a human body and the earth ground. The other uses the attenuation factor in reception. To avoid the influence of the lead wire in the estimation of Cb, Cb is estimated from the attenuation factor measured with an amplifier with a low input capacitance. The attenuation factor in reception is derived by using the applied-voltage dependence of the reception rate. This way avoids the influence of any additional instruments on the return-path capacitance and allows that capacitance to be estimated under the same condition as actual intrabody communication. The estimates obtained by the two methods agree well with each other, which means that the estimation of Cb is valid. The results demonstrate the usefulness of the methods.

A high Tc superconducting quantum interference device (SQUID) magnetometer system is developed for the application to biological immunoassay. In this application, magnetic nanoparticles are used as magnetic markers to perform immunoassay, i.e., to detect binding reaction between an antigen and its antibody. The antibody is labeled with γ-Fe2O3 nanoparticles, and the binding reaction can be magnetically detected by measuring the magnetic field from the nanoparticles. Design and set up of the system is described, and the sensitivity of the system is studied in terms of detectable number of the magnetic markers. At present, we can detect 4106 markers when the diameter of the marker is 50 nm. Total weight of the magnetic nanoparticles becomes 520 pg in this case. An experiment is also conducted to measure antigen-antibody reaction with the present system. It is shown that the sensitivity of the present system is 10 times better than that of the conventional method using an optical marker. A one order of magnitude improvement of sensitivity will be realized by the sophistication of the present system.

Recent progresses in high Tc superconducting quantum interference device (SQUID) magnetometers are discussed. First, intrinsic sensitivity of the SQUID at T=77 K is discussed. For this purpose, transport and noise properties of the bicrystal junction are clarified, and optimization of junction parameters is shown. We also discuss the quality of the SQUID from a comprehensive comparison between experiment and simulation of the SQUID characteristics. Next, we discuss issues to guarantee correct operation of the SQUID magnetometer in noisy environment, such as a method to avoid flux trapping due to earth magnetic field, high-bandwidth electronics and gradiometer. Finally, we briefly describe application fields of the high Tc magnetometer.