Abstract: A radio LAN master station system which provides long distance communication and suffers from small interference by another system located inside and/or outside of a service area comprises a transceiver, and a plurality of directivity antennas each directed to respective section with some angular spacing, through a power distributor which couples said transceiver with said antennas. Polarization plane of any antenna is orthogonal to polarization plane of an adjacent antenna.

Abstract: In each of communication stations, among all of spread spectrum signal waves having the carrier frequencies separated from each other in units of an integer multiple of the frequency amount R, all the spread spectrum signal waves having the carrier frequencies separated from each other in units of an even-number multiple of the frequency amount R are converged into a first group; all the spread spectrum signal waves that are adjacent to the aforementioned spread spectrum signal waves and that have the carrier frequencies separated in units of an even-number multiple of the frequency amount R are converged into a second group; and the first and the second groups of spread spectrum signal waves are simultaneously transmitted according to orthogonal polarized waves to perform information transmission. In addition, the communication station performs the transmission of the signal waves according to a time division multiple access (TDMA).

Abstract: A method is disclosed for uniquely determining the position of a mobile earth station in a mobile satellite communication system which employs a non-geostationary satellite with a multi-spot beams. A given point of a preknown position on the earth surface is defined as the center coordinate of a three-dimensional coordinate axis, information on the measured distance and Doppler shift amount between a mobile earth station of an unknown position and a non-geostationary satellite is used to repeat the estimation of the position of the mobile earth station a plurality of times, thereby obtaining the position of the earth station with high accuracy.

Abstract: A timing recovery and tracking method and apparatus with respect to data signal in a digital communication system is provided. The method includes a step of setting a time window for making a decision based upon a predetermined threshold level, the time window having a time period corresponding to a transmission data rate in the digital communication system, a step of detecting a time duration positioned within the time window, a level of a received signal being higher than the predetermined threshold level during the time duration, a step of assuming a substantially middle point of the time duration as an optimum decision point of the received signal, and a step of updating the time window so that the updated time window has its center at a position of the assumed optimum decision point.

Abstract: A combined channel or a composite channel is to be transformed into a plurality of element channels. The composite channel may be either shared by a plurality of communication stations on time division multiplex basis, or used by a single communication station. In a transmit side, a serial data information which is called a composite channel is transformed to parallel form associated with a plurality of element channels, each of which is spread by using a single common PN code. Each spread element channels are frequency converted to radio frequency so that the center carrier frequency is offset from that of adjacent element channel by an integer multiple of information transmission rate of each element channel, and frequency band occupied by spread element channels overlap with one another. Each element channels thus spread and frequency converted are combined on frequency axis, and transmitted to a receive side.

Abstract: To provide a film for optical element made of liquid crystal polymer whose productivity and economical efficiency are improved; a laminated sheet formed by bonding this film to a polarizing plate; and an optical element which can be optically inspected, and used under an environment of high temperature and high moisutre, and whose surface hardness is so high that the surface is not easily damaged. A long laminated sheet for optical element comprising a liquid crystal polymer layer, and a polarizing film layer; and a long laminated sheet for optical element comprising at least a liquid crystal polymer film layer oriented in the direction oblique to the MD direction at a given angle, and a polarizing film layer.

Abstract: An air motor has a rotor rotatable in response to the pressure of pressurized air. A cylindrical rotary member is connected to the air motor for causing a rotation in synchronism with the rotation of the rotor. A rotary slider is slidable in the axial direction along the inner cylindrical wall of the rotary member. A rotational force transmitting mechanism is provided for transmitting the rotation of the rotary member to the rotary slider. A shaft has one end fixed to the rotary slider and the other end equipped with a piston and a driver bit holder. The rotational and axial motion of the rotary slider is transmitted to a driver bit held in the driver bit holder. And, a cylinder guides the axial slide movement of the piston responsive to the pressure of pressurized air applied on a pressure-receiving surface of the piston.

Abstract: A spread spectrum communications system includes at least one communication station for transmitting a plurality of digital information data sequences via a plurality of communication channels by using the same PN code sequence. The communication station spreads the respective digital information data sequences by the PN code sequence to provide spread spectrum signals, modulates the spread spectrum signals by respective carriers having different frequencies from each other to provide modulated signals, and then transmits the modulated signals via the communication channels respectively. A frequency interval of the carrier frequencies is determined to an even-numbered multiple of a symbol rate of the transmitted digital information data sequences.

Abstract: A method is disclosed for uniquely determining the position of a mobile earth station in a mobile satellite communication system which employs a non-geostationary satellite with a multi-spot beams. A given point of a preknown position on the earth surface is defined as the center coordinate of a three-dimensional coordinate axis, information on the measured distance and Doppler shift amount between a mobile earth station of an unknown position and a non-geostationary satellite is used to repeat the estimation of the position of the mobile earth station a plurality of times, thereby obtaining the position of the earth station with high accuracy.

Abstract: In a time division multiplex (TDM) signal in which a symbol is sent one by one periodically, a unique word in the TDM signal is recognized quickly in a receiving station. A receive station has essentially N number of correlators each having a specific unique word pattern. A unique word pattern in each correlator is obtained by shifting by predetermined symbols cyclically from a reference unique word pattern. Each correlator provides a correlation value between a received TDM signal which includes a unique word and a unique word pattern defined in the correlator. Among outputs of N number of correlation values, which exceed a predetermined threshold value, the correlator which provides the maximum correlation value is selected, and the receive timing of the unique word is determined by the correlator thus selected.

Abstract: In a radio communication system using time division multiple access system (TDMA) for access control method, modulation signal sent by a slave station is frequency-dispersed during a TDMA burst period by using a chirp signal which frequency changes continuously on time axis so that signal power density on communication link is decreased and interference signal affected by the slave station to another radio communication system is reduced. According to the present invention, modulation signal transmitted by each slave station is multiplied to a chirp signal which frequency changes continuously on time axis during a TDMA burst period so that carrier frequency which carries the modulation signal changes continuously on time axis to disperse on frequency axis to a predetermined bandwidth thereby decreasing signal power density of transmit signal from the slave station.

Abstract: A mobile communication system is disclosed which precludes the necessity for mobile station to perform processing for microcell zone switching even when it moves from one microcell zone to another and which permits high-speed microcell zone handover. The service area of mobile communication is split into a plurality of macrocells; the macrocells are each subdivided into a plurality of microcells; a microcell base station equipped with a transmitting and receiving antenna and a power amplifier is installed in each microcell; a different communication channel is assigned to individual mobile station in the macrocell; even when the mobile station moves from one microcell to another, no channel handover takes place; and only when the mobile station moves from one macrocell to another, a mobile network control center which supervises the macrocell base stations effects channel handover.

Abstract: In a satellite mobile communication system in which at least one mobile earth station communicates with a land earth station which is coupled with a network, through a satellite, the land earth station measures frequency offset in a request signal and/or a response signal in a received signal from the mobile earth station due to frequency offset by a transponder in the satellite and/or a local oscillator of said mobile earth station, and doppler shift due to movement of the satellite. The measured frequency offset is forwarded to the mobile earth station through a singalling channel or a communication channel through a satellite. The mobile earth station compensates frequency offset by adjusting oscillation frequency of a local oscillator in the mobile station based upon the measured frequency offset sent from the land earth station.

Abstract: A frequency offset compensation method has the steps of raising the detected signal to the M-th power to remove a modulation factor from the received signal, and accumulating the M-th power signals for N (N is an integer) symbols to derive a phase component of the accumulated M-th power signals. Then, the derived phase component is divided into M so as to obtain an estimation value with respect to phase shift due to frequency offset which represents frequency deviation from a true carrier frequency contained in the received signal, and the received signal is multiplied by the obtained estimation value in a form of conjugate complex number to remove the phase shift due to the frequency offset from the received signal.

Abstract: A grinder has a grinding member. The grinder includes a rotatable spindle having an engagement portion. A first flange engages the engagement portion of the spindle. The first flange and the engagement portion of the spindle define a given play therebetween in a direction of rotation. The grinding member is held between the first flange and a second flange. A lubricant solid material is provided between the first flange and the engagement portion of the spindle.

Abstract: An automatic drilling machine has an electric drilling unit on which a cylindrical cutter is rotatably mounted. The drilling machine includes a drill motor for rotating the cutter and a feed motor for linearly moving the cutter for the purpose of drilling into materials such as concrete. The current flowing through the drill motor before a drilling load is imposed thereon is detected for a microprocessor to determine the type of the cutter being used. The drill motor is driven at a rotation speed suitable for the cutter being used and the feed motor is driven at a speed such that the rotation speed of the drill motor thus set is maintained unchanged. Particularly, the drill motor is driven at a reduced rotation speed from the start of drilling until a predetermined drilling depth is reached to reduce chatter vibration which may otherwise be generated if the drill motor is driven at a regular constant speed from the beginning of drilling until the end.

Abstract: Through utilization of a transportable earth station capable of communicating with both of a mobile satellite communication system and a terrestrial based mobile communication system and a portable terminal which is capable of radio communication with the transportable earth station and used in the terrestrial based mobile communication system, it is possible to communicate with both of the terrestrial based mobile communication system and the mobile satellite communication system by only one portable terminal in a wide variety of communication environments.

Abstract: A selection diversity system using a decision feedback equalizer which has excellent tracking ability performance and equalization ability performance for frequency selective fading and a diversity effect against Rayleight fading. In a selection diversity system using a decision feedback equalizer, a decision data symbol of the equalizer output of a branch in which an average estimation error over a plurality of symbols is minimum is selected and combined, and the selected decision data symbol is used to recalculate the estimation error of every decision feedback equalizer and the tap gain coefficient of the decision feedback equalizer is updated using the recalculated estimation error, thereby overcoming the step out by the integration of the estimation error and the random selection error which is caused by the selective combined diversity system.

Abstract: Differential data signal transmission technique, providing a differential data signal transmission technique inclusive of the correcting factor that requires no transmitter/receiver other than the GPS receiver, comprises the use of a differential ranging system where spread spectrum signals (SS signal) are multiplied at the same frequency, transmission rate, and modulation method used by the GPS satellites, but with different codes from those used by the GPS satellites, the SS signals used to transmit correcting factor from an earth station on the ground to a mobile station on the ground carrying a GPS receiver via a geostationary orbit satellite or a low earth orbit satellite.

Abstract: A portable power tool such as a portable circular saw is provided with a sawdust collection system based on the generation of an air flow resulting from rotation of a rotary cutting blade, with this air flow being guided to transport sawdust resulting from cutting operations along a guide path through a first discharge aperture into a dust box in which the sawdust is precipitated, with a low-velocity air flow then passing out of the dust box through a second discharge aperture to be recirculated through the flow path. Extremely effective dust collection is attained with a simple configuration, while the dust box can be positioned such that the weight of accumulated sawdust therein does not significantly affect the balance or ease of operation of the portable power tool.