Michitaka Ameya

Time-domain three antenna method for biconical antenna

We apply our proposed method [1] for evaluating the free-space antenna factor of a Biconical antenna. The method is based on the techniques of a time domain analysis and a pulse compression technique. The method enables us to isolate the direct wave from the reflected waves on the ground plane in an open area test site, and to evaluate the free-space antenna factor of a Biconical antenna.

New Uncertainty Analysis for Permittivity Measurements Using the Transmission/Reflection Method

We have developed a new algorithm for the uncertainty analysis of permittivity calculations of high-loss materials using the transmission/reflection (T/R) method. In the T/R method, several calculation procedures are performed to derive the permittivity. In our method, the permittivity is derived from measured S-parameters by solving an equation in which S-parameters are included in the form (S21+ S12)+β(S11 + S22), where β is a weighted factor to be optimized to minimize the uncertainty. We confirmed its efficacy by doing numerical calculations, as well as using actual measurement data for several materials obtained with a waveguide fixture. We also considered the effect of the type of calibration method used on a vector network analyzer on the permittivity uncertainty, and quantitatively clarified that it is essential to develop a highly accurate S-parameter measurement system to perform permittivity measurements using the T/R method accurately.

Far field antenna factor estimation method for super broadband antenna using time-frequency analysis

We are developing a far field gain and antenna factor estimation method for broadband antenna standards. We have already proposed a method for estimating the free space antenna factor of broadband antennas using a time-domain analysis and a pulse compression technique. However to estimate the antenna factor and gain, we are using fixed antenna distance. In this paper, we propose a new estimation method for determining the antenna distance at each frequency that to estimate the far field antenna factor. Our proposed method is based on the techniques of a time domain analysis and a time-frequency analysis using a short time Fourier transform. In the case of a super broadband antenna, the difference between far-field antenna factor and the estimated antenna factor using our proposed method is less than 0.1 dB at 10 m antenna distance and less than 0.2 dB at 3m antenna distance in the frequency range from 30 MHz to 250 MHz.

Near-Field Antenna Measurements Using Photonic Sensor of Mach-Zehnder Interferometer

We have been developing a photonic sensor system to measure the electric near-field distribution at a distance shorter than one wavelength from the aperture of an antenna. The photonic sensor is a type of Mach-Zehnder interferometer and consists of an array antenna of 2.4 mm height and 2 mm width on a LiNbO3 substrate (0.5 mm thickness, 8 mm length, and 3 mm width) supported by a glass pipe. The photonic sensor can be considered to be a receiving infinitesimal dipole antenna that is a tiny metallic part printed on a small dielectric plate at microwave frequency. Those physical and electrical features make the photonic sensor attractive when used as a probe for near-field antenna measurements. We have demonstrated that the system can be applied to planar, spherical, and cylindrical near-field antenna measurements without any probe compensation approximately below 10 GHz. We show the theories and the measurements using the photonic sensor in the three near-field antenna measurement methods.

Uncertainty analysis of far field antenna factors using amplitude center modified equation

We have developed a far field antenna factor estimation method for broadband antennas. Our using method determined the far field antenna factor using amplitude center modified antenna factor estimation equation. The expanded uncertainty (k = 2) of log-periodic dipole array antennas was estimated to be from 0.07 dB to 0.27 dB over the frequency range from 300 MHz to 1200 MHz.

Precision antenna measurement using optical fiber link technologies

We are developing some antenna measurement systems using optical fiber link technologies. Optical fiber link system can replace the metal coaxial cables and suppress the reflection waves from the coaxial cable. In this paper, we show some antenna measurement system using optical fiber link systems and measurement results.

EMI Noise Source Discrimination using Cross Domain Analyzer and Analog RoF Link with Mobile Robot

In this paper, we propose a new method for electromagnetic interference (EMI) noise analysis using an analog radio-over-fiber (RoF) link, cross domain analyzer, and mobile robot. With this new method, both the phase distribution and amplitude distribution of an electric field radiated by an EMI noise source can be measured. From the measured and simulated results obtained using the method of moments technique, we show that we can differentiate between noise sources in different positions using the phase distribution measured on a measurement circle.

New uncertainty analysis and simplified verification method for permittivity measurements using the Transmission/Reflection method by utilizing a weighted factor

We have developed a new algorithm of uncertainty analyses for the permittivity calculation of high-loss materials using the Transmission/Reflection (T/R) method. In the T/R method, there are several calculation procedures to derive the permittivity. In our method, the permittivity is derived from measured S-parameters by solving an equation in which S-parameters are included by the form: (S21+S12)+β(S11+S22), where β is a weighted factor to be optimized in order to minimize the uncertainty. We compared uncertainties of the permittivity derived from different calculation procedures to confirm the efficacy of our method. We also proposed a simplified verification method for measurement results.

Antenna pattern measurement using nested Mach-Zehnder optical modulator and uni-traveling carrier photodiode in millimeter wave

An antenna pattern measurement system above 100 GHz using a nested LiNbO3 Mach-Zehnder (LNMZ) modulator and a uni-traveling carrier photodiode (UTC-PD) is proposed. This system can minimize the influence of waveguide components because an optical fiber is used as the mm-wave transmission line. Therefore, this system achieves precise antenna pattern measurements above 100 GHz.

A novel evaluation method for semi-anechoic chamber using zero biased optical devices and time-domain analysis

We propose a novel optical fiber link electromagnetic interference measurement system that consists of the transmitting and the receiving optical-fiber link system. In order to demonstrate the performance of the optical link system, we carry out the S21(ω) measurement and S21(t) calculation between a small biconical antenna with a comb generator box and broadband antennas. The results of S21s by our optical link system agree very well with those of the case of a comb generator with a small biconical antenna using spectrum analyzer. These results show possibility of evaluation for a semi anechoic camber by our optical link system.