Masanobu Hirose

Measurement and Uncertainty Analysis of Free-Space Antenna Factors of a Log-Periodic Antenna Using Time-Domain Techniques

We have proposed a method for evaluating the free-space antenna factor of a log-periodic dipole antenna (LPDA) with a time-domain technique. The proposed method is based on a time-domain analysis and a pulse-compression technique. The proposed method enables the direct wave to be isolated from reflected waves on the ground plane of an open-area test site (OATS) and evaluation of the free-space antenna factor. In a measurement, two LPDAs are held on masts at a height of 6 m above the ground and are separated by 10 m. The direct wave is separated using a Wiener filter obtained from frequency-domain data at 3 m antenna separation. The proposed method can completely separate the direct wave from other waves from the ground plane of an OATS. The expanded uncertainty (k = 2) of LPDAs was estimated to be from 0.38 to 0.45 dB over the frequency range from 300 to 1000 MHz.

Antenna Measurements by One-Path Two-Port Calibration Using Radio-on-Fiber Extended Port Without Power Supply

We have developed a prototype of a novel extended port for an RF vector network analyzer (VNA) below 2 GHz, employing a radio-on-fiber technique in order to overcome several problems in antenna measurements. Specifically, it excludes unwanted effects associated with the metallic cables connecting antennas to the VNA. Using our system, we can make antenna measurements in one-path two-port calibration without using the metallic cables. All components need neither power supply nor bias circuit. To demonstrate the capability of the proposed system below 2 GHz, we have measured the uarr-parameters between two biconical antennas. #n agrees well with that obtained using a conventional VNA system. The agreement is within 0.03 (0.013 on average). The dynamic range of S2i is found to be more than 45 dB (56 dB on average)

New integral equation formulation of the measured equation of invariance and the extension to analyze two-dimensional cylinders with impedance boundary conditions

We have derived a new form of the integral equation formulation of the measured equation of invariance (IE-MEI). The new formulation clarifies the existence of a relationship between scattered electric and magnetic fields at consecutive nodes in the IE-MEI and indicates that the relationship in a problem for a perfect electric conductor (PEC) holds for a problem with arbitrary materials. In a scattering problem of a two-dimensional cylinder with an impedance boundary condition (IBC), every matrix in the IE-MEI is a band-like sparse matrix. That is, the solution process in the IE-MEI with an IBC is the same as that for a PEC. Therefore the IE-MEI with an IBC has the same merits of the IE-MEI for a PEC: The more efficient computation can be achieved with the smaller memory than those of the method of moments (MOM). The IE-MEI with an IBC is validated by numerical examples for a circular cylinder and a square cylinder by comparison with a combined field MOM that satisfies exact boundary conditions. Numerical examples show that the IE-MEI with an IBC is applicable to the case where the generalized skin depth is less than half the width of a scatterer.

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.

Optical fiber link 1-pass 2-port antenna measurement system

We have proposed the optical fiber link antenna measurement system that can measure the calibrated S11 and S21 between two antennas under test (AUT) after OSLT calibration in one-pass two-port system. Our system consists of the transmitting and receiving optical-fiber link systems. The transmitting system consists of the electro-absorptive modulator, erbium doped fiber optical amplifier (EDFA), optical fiber, zero biased uni-traveling-carrier photodiode (UTC-PD), small type bi-directional coupler, and two optical reflection type Mach-Zehnder LiNbO3 optical intensity modulators (LN-modulators) with 50 ohm loads. The system can detect the reflection signal from the transmitting AUT and the reference signal toward the AUT. The receiving system consists of an optical reflection type LN-modulator and the optical field measurement system, to measure the transmission signal through the receiving AUT. Our system can measure the reference signal, the reflection signal, and the transmission signal in one-pass two-port model between the two AUTs. Then OSLT calibration can be adopted. In this paper, in order to demonstrate the validity of our optical fiber link system, we compare the calibrated S11 and S21 results of two UHALP9108A 1 Log-periodic antennas by our proposed optical-fiber link system with the ones by the conventional coaxial cable system in frequency-domain and time-domain measurements. The results clearly indicate that our proposed system can be used to evaluate the S11 and S21 of the AUT at the frequency range from 300 MHz to 1800 MHz without coaxial cables.

Compact spherical near-field measurement system for UWB antennas

We have developed a compact spherical near-field measurement system suitable for UWB antennas from 3 GHz to 10 GHz. The patterns measured by this system were compared with the ones by the conventional far-field method and they agreed within 1 dB in the main beams over this wide frequency range. Because this system uses only one photonic sensor as the probe over the frequency range, the system is suitable for the pattern measurements of UWB antennas. Moreover, because the photonic sensor is very small compared with the wavelengths and very lightweight, the system can be made in a compact and simple form. Therefore the system can be installed and used in a usual experimental room.

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.

A method of pattern measurement to cancel reflection waves in anechoic chamber

In the paper, we have shown that averaging the radiation patterns over several distances between two antennas is useful in order to reduce the influence of reflection waves, using simulation software FEKO. In the conditions with and without reflection waves we simulate the radiation patterns of the biconical antenna (the operation band is from 30 MHz to 300 MHz) in distance between antennas from 315 cm to 615 cm by 50 cm steps. Averaging the radiation patterns is useful for reducing the influence of the reflection waves in an anechoic chamber. We will apply the proposed method to various antennas, and determine the optimum averaging number, distance, and steps.

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.