Abstract: A cell group is formed from three cells, each of which has a site equipped with antennas. The antennas differ from one another in terms of horizontal orientation and cover all horizontal directions. The cell groups are arranged in a repeating pattern such that a cell having a site assigned different frequency is interposed between cell groups assigned the same frequency, thereby constituting a minimum unit area to be repeated.

Abstract: A manhole cover is provided with an incorporated radio repeater and a repeater antenna attached onto its rear surface. Another repeater antenna is provided inside the sewer below the manhole. This repeater antenna is connected to a radio transmitter/receiver, an electric-optical/optical-electric signal converter, and an optical fiber cable. With this arrangement, the manhole cover and optical fiber cable are connected via radio communication.

Abstract: Herein is revealed a helical antenna apparatus wherein the direction of beam radiation hardly changes even if the frequency in use changes. Two helical antennas which are wound with two conductive wires spirally, respectively, at equal intervals with a specified pitch .alpha. in the form of a cylinder are disposed along the length of the helical antennas so that the axes thereof substantially coincide with each other. By determining the lengths of the feeders of the respective helical antennas appropriately in order to set the phase of supplied power, it is possible to form the beam of signals radiated into space in the shape of conical beam having a directivity oriented obliquely upward. Additionally, it is possible to obtain the conical beam in which the direction of beam radiation does not change even if the frequency in use is changed.

Abstract: An antenna apparatus comprises a dielectric substrate, an earth conductor mounted on one surface of the substrate and forming a microstrip transmission line, an upper conductor mounted on the other surface of the substrate and forming a microstrip transmission line, an antenna element formed integrally with the microstrip transmission lines, and a delayed wave opening situated in the earth conductor in confronting relationship with the upper conductor.

Abstract: The present invention relates to an array antenna for receiving a signal in a microwave band. The array antenna includes a plurality radiating element arranged in subarrays, each subarray having a first feeder connected to the radiating elements and a low noise amplifier (LNA) connected to receive the output of the first feeder, a frequency converter, and a second feeder for combining the outputs of the sub arrays from the LNAs. According to this structure, in the formula representing the noise temperature observed at the radiating elements, the gain the LNA appears in the denominator in the term representing the loss of the second feeder which combines the outputs of the sub arrays. Therefore, if the gain of the LNA is sufficiently large, it is possible to disregard the influence of the loss of the first and second feeders for combining the outputs of the sub arrays on the noise temperature.

Abstract: A radiowave receiving array antenna includes a lower grounding conductor, an upper grounding conductor, and supporting plates for supporting a feeder circuit board therebetween. Radiation elements and low noise amplifiers are mounted on the same plane of an insulating film of the feeder circuit board. The number of radiation elements is reduced, but the quality of the signal is not deteriorated.