This paper first presents an active integrated antenna configuration designed for broadband mobile wireless access systems using the 25-GHz band. This active integrated antenna comprises a microstrip antenna array and RF front-end circuits adopting spatial power combining schemes for reduced power consumption of the power amplifiers. Furthermore, the antenna and RF circuits are integrated into each side of a thick copper backing plate and both are connected through microstrip line /slot transitions. The developed active integrated antenna achieves the output power of 14.6 dBm and a noise figure of less than 5 dB. The wireless system using the developed active integrated antenna achieves a 6-dB improvement in the packet error rate compared to that using a passive antenna with the same array design as the active integrated antenna. Furthermore, we obtained the first license of the active integrated antenna for commercial use in high-speed wireless communication systems in Japan.

A power combining technique using a Fabry-Perot resonator with many more active devices is investigated. The Fabry-Perot power combiner consists of two mirrors with a circular groove mounted with the active devices. The power combiner has an axially symmetrical structure and operates at an axially symmetrical TEM01n mode so that uniform device-field coupling required for perfect power combining can be realized. By numerical calculation using the boundary element method, it was shown that high combining efficiency can be obtained when the active devices are mounted in the circular groove of larger radius on either of the two mirrors. In experiments at X-band, power combining efficiency over 90% was obtained for the case of twelve devices on either of the mirrors and the output powers of the twenty or twenty-four devices on both the mirrors were almost perfectly combined.

Design of circularly polarized active antennas of dual-fed square patch type is given, and spatial power combining and phased array operation of the antennas have been successfully achieved. In a phased array experiment of the arrays with two and three active antennas by the method of varying their free-running oscillation frequencies, we obtained the scan angles from -12 to +13 and those from -13 to +13, respectively, and good axial ratios together with high spatial power-combining efficiencies.

In coupled oscillator arrays, it is possible to control the inter-element phase shift up to 180 by free-running frequency distribution based on injection-locking phenomenon. In this paper, a new technique to control the inter-element phase shift electronically up to the maximum extent of 360 is reported. Oscillators are unilaterally coupled to the preceding oscillator through one of the two paths, which differ from each other 180 in electrical length and each includes an amplifier. Turning on the desired amplifier one can control the phase shift either -180 to 0 or 0 to 180. The technique was applied in a three-element oscillator array each coupled to a patch antenna via a round aperture. The radiation beam of the array could be scanned 47 in total.

An equivalent circuit for designing a coherent power combiner using a quasi-optical resonator has been developed. In the resonator, large numbers of devices (HEMT, HBT, etc. ) are arrayed two dimensionally and mounted on a surface of a metal grooved-mirror. A newly developed equivalent circuit for the resonator has been constructed using a transmission-line model. Experiments performed at Ku-band have shown that oscillation frequencies in a 33 HEMT array oscillator can be predicted with errors of less than 1% by using this equivalent circuit.

Several types of transmission-line coupling are analyzed to use in one- and two-dimensional active antenna arrays, and a method is developed to scan the beam of the arrays using the mutual locking theory. To compensate the undesired effect of strong radiative coupling of the nearest neighbor elements on the phased array performance, addition of resistive stubs to the end elements is proposed. In a 14 array it was observed that after the connection of resistive stubs, the scanning range of the array increased considerably. The effect of oscillator amplitudes on the phased array behavior is explored numerically. In the experiments main beam of 22 and 33 active antenna arrays were steered up to 25 and 15, respectively in the H-plane.

This paper describes a concept of the quasioptical spatial power combining technique and its demonstration of active integrated antenna arrays with strong coupling as an actual example of high efficient combiner in high frequencies. Some configurations of the arrays such as a 3-element linear array and a 33 array are designed with a circuit and electromagnetic simulator. In order to predict the operating frequencies, large signal FET model parameters are determined from measured small signal S-parameters.

In outdoor fields such as construction, mining and agriculture, there is an increasing demand for autonomous vehicles to reduce labor costs. Also, a positioning system is one key technology required for autonomous vehicle systems. For the purpose of expanding the potential of millimeter-wave applications, we have developed a positioning system in the 77-79 GHz frequency band, using the hyperbolic radio navigation method. This system operates in a restricted area with a radius of about a few hundred meters. A spread spectrum with a PN code is used as the ranging signals. We realized about 0.1 m in positioning accuracy.

This paper treats a new-type power combining system of four oscillators equally coupled to one another through an eight-port hybrid. This system is marked by easy analyzability and adjustability from its symmetrical construction. In addition, a combined power from the four oscillators is distinguishably delivered to an arbitrary port of four output ports, and hence can be switched in four ways. Experimental corroboration is presented also.

We propose an axially symmetrical Fabry-Perot multiple-device oscillator operating at an axially symmetrical TEM01n-mode, which has an excellent feature of uniform device-field coupling required for high efficiency power combining. By carrying out the boundary element analysis, it is shown that a plane-mirror output structure is remarkably advantageous compared with a concave-mirror output structure to obtain an adequate output coupling and to enable stable operation characteristic with respect to the axial mode number n. Experiments in X-band confirmed this excellent performance and achieved almost perfect power combining of efficiency as high as 106% and 99% for six- and eight-device case, respectively.