Yutaka Imaizumi

Electric field distribution measurement of microstrip antennas and arrays using electro-optic sampling

This paper proposes an electric field distribution measurement method for microwave integrated circuit arrays that uses electro-optic sampling (EOS). The electric fields of a microstrip patch antenna are measured by EOS and compared with the theoretical results calculated by the spectral domain approach. Good agreement between measurement and theory is found. An array antenna composed of two microstrip patches is also assessed by the EOS method and the expected results are experimentally verified. The EOS proposed in this paper is promising to evaluate the electric field distribution of individual antenna elements in large scaled integrated array antennas. >

Phased array fed reflector antennas with interpolation network for next generation mobile satellite communication systems

We propose a modified DCMP method that considers the influence of the interpolation network. An onboard array-fed-reflector antenna with the interpolation network is designed using the modified DCMP method. We confirmed the validity of the method by calculating the resulting antenna patterns. The antenna patterns formed by the array feeder with the interpolation network satisfy the required antenna performance.

Novel planar antenna measurement techniques with electro-optic sampling (EOS)

This paper has proposed a new antenna assessment technique. Antenna radiation patterns are measured using electro-optic sampling (EOS). The electric field of a microstrip-fed patch antenna is measured by an EO probe tip and the radiation pattern is theoretically calculated. The calculation results are compared against the conventionally determined far-field pattern. The experimental results confirm the effectiveness of the proposed method. The method is suitable for planar antennas, very small MMIC antenna arrays, i.e., wafer scale integrated circuits (WSICs), and evaluating the mutual coupling of large scale phased arrays.<<ETX>>

A study on an onboard Ka-band phased-array-fed imaging reflector antenna

We proposed a new method for reducing the grating lobe level even when the number of radiating elements in the imaging reflector antenna is small. The most significant feature of this method is that the distance between the array plane and the center of subreflector is controlled so as to reduce the generated grating lobes. Using this method the magnification factor M can exceed the usually used value in order to decrease the number of radiating elements. This method is extremely low-cost because no additional components are added, and it does not decrease the reliability. An onboard phased-array-fed imaging reflector antenna was designed for the future Japanese Ka-band broadband satellite communication system by using the proposed method, and its performance met the system requirements.

BEAM FORMING FOR LARGE-SCALE PHASED ARRAY ANTENNAS

For high-data-rate satellite communication systems, the satellite must need high performance onboard equipment. To improve the onboard antenna performance in higher frequency band, the circuits scale of active phased array antennas take a tendency to become large. This paper presents a novel beam forming technique for onboard large-scale active phased array antennas. The proposed technique uses fewer phase control circuits than the conventional technique. The proposed technique is validated by antenna pattern simulations. The design of an onboard large-scale phased-array-fed reflector antenna based on the proposed technique is described for high-data-rate satellite communication systems.

An excitation weight determination method for onboard phased array antennas with weight interpolation network

In order to realize lightweight onboard satellite antennas, we proposed a technique that uses linear interpolation to reduce the number of control circuits. Compared to the conventional approach, the reduction is about 70%. To apply the technique to practical multi-beam systems with frequency reuse, it is necessary to meet the requirement in term of beam isolation. This paper presents a method for determining the excitation weights so as to meet the requirement of multi-beam systems with frequency reuse. We confirm the validity of the method by calculating the antenna patterns generated by the excitation weights output.

Field trials on hyper multi-point data gathering SATCOM system with highly efficient channel allocation scheme for sensor network

We have developed a prototype of the hyper multi-point data gathering satellite communications (SATCOM) system that can collect various sensor data with high frequency utilization efficiency from a large number of data-sensing stations scattered over wide areas and send it to one data-gathering station in a unified way. This paper presents its technical features, as well as field trial results to evaluate its feasibility using the Japanese Engineering Test Satellite VIII. The results show that the system is very useful for collecting various sensor data having different characteristics such as frequency and data size, and sending it to the data-sensing station simultaneously and efficiently.

Novel onboard satellite antenna pattern measurement method -Antenna pattern measurement results of Japanese engineering test satellite VIII-

We proposed a novel in-orbit antenna pattern measurement method. We measured ETS-VIIIpsilas onboard antenna pattern using the proposed method. We confirmed that the measured and calculated patterns were in good agreement. Our method offers high accuracy measurements as well as short measurement times.