Abstract: A base station assigns a subcarrier for downlink communications under Orthogonal Frequency Division Multiple Access. Before downlink communications with a mobile station, based on carrier sensing by the mobile station, the base station detects information concerning an available subcarrier from downlink signals using a modulating unit. The information concerning the available subcarrier is stored in a downlink-information sharing unit and is shared among the base station and the adjacent base stations. A downlink subcarrier setting unit sets the available subcarrier for downlink communications.

Abstract: An array antenna directivity control apparatus includes: weighting coefficient updator which updates a weighting coefficient based on an error between antenna signals of multiple antennas and a known reference signal; and update amount corrector which corrects an amount of updating for each of the weighting coefficients, which updating is performed by said weighting coefficient updator, based on predict error information predicted on the basis of the error in past. As a result, it is possible to adjust a weighting coefficient with prediction of the next position of a target. Thus, it becomes possible to track a target which is being moving in high speed with a small amount of calculation.

Abstract: A demodulation circuit according to the present invention comprises an automatic equalizer for carrying out equalization processing of a signal, a carrier recovery circuit for carrying out carrier recovery processing based on an equalized signal by the automatic equalizer. A center tap for carrying out an amplitude control of the automatic equalizer is placed on an input side thereof, and a control signal to the center tap is transmitted from the automatic equalizer.

Abstract: A demodulation circuit can perform a capturing operation although afrequency error is large. A phase comparator out puts a predetermined value other than 0 as a determination result of a phase error when a phase error of a carrier wave is large and a signal point is located at a predetermined position. A loop filter outputs a negative minimum value to an integrator when an integrated value of a determination result reaches a positive maximum value of a limiter. Thus, when a phase error is large, a value changing from a negative minimum value to a positive maximum value is output from the loop filter, thereby realizing a broad synchronous capture range.

Abstract: An apparatus for estimating phase/amplitude characteristics of a propagation path. The apparatus removes, from a receive signal on a data channel on which known information is transmitted upon being time-multiplexed between items of unknown information, transmit information on this channel, which provides phase/amplitude information indicative of phase/amplitude characteristics that this data channel has suffered over the propagation path. The apparatus further removes from a receive signal on a data channel on which only unknown information is transmitted, transmit information on this channel, which provides phase/amplitude information indicative of phase/amplitude characteristics that this data channel has suffered over the propagation path. The apparatus includes an adder for adding the two phase/amplitude information and an estimation unit for estimating, from an adder output, a phase characteristic and an amplitude characteristic that each channel has suffered over the propagation path.

Abstract: In a mobile communication receiving apparatus in which signals received on a plurality of receiving paths (branches) are combined by a combiner, correlation between noise signals contained in the signals received on respective ones of the branches is detected by a noise correlation calculating unit, and control is exercised so as to maximize signal-to-noise power ratio of the combined signal based upon the correlation calculated in the noise correlation calculating unit. Signal-to-noise power ratio can be maximized even if noise components contained in respective ones of the branch signals are mutually correlated.

Abstract: An apparatus for communications includes, a front processor for outputting a digital formatted base band signal with quadrature demodulating a modulated signal; an interpolation processor for interpolating to adjust a phase error in accordance with sampling timing on the basis of the base band signal outputted from the front processor and for creating and outputting a base band signal synchronized with the sampling timing; and a back processor for wave-shaping the base band signal outputted from the interpolation processor and for outputting. And the apparatus changes tap coefficients which are supplied to an FIR filter in the interpolation processor on the basis of the modulated signal inputted therein, and can appropriately control the bandwidth characteristic of interpolators.

Abstract: A distortion compensating device provided in a receiver for compensating distortion which is added to a signal in a transmission path. The signal is generated in a multi-level modulator of a transmitter in which a digital signal is mapped to one of a plurality of specified signal points in a signal space diagram. The device includes a signal-point-position averaging circuit for producing an average signal point for each of a plurality of distributions of received signal points in the signal space diagram. A discrimination circuit in the device discriminates the average signal point closest to a received signal point from other average signal points in the signal space diagram.

Abstract: In an OFDM transmitter apparatus for transmitting transmit signals, which are output from first and second OFDM transmit circuits, utilizing two mutually orthogonal polarized waves, a single carrier wave generator is provided in common for the OFDM transmit circuits, and a frequency converter in each OFDM transmit circuit multiplies a baseband signal by a common carrier wave, which is output from the carrier wave generator, to convert the baseband signal to a radio signal.

Abstract: A CDMA receiving device is provided. The receiving device comprises a receiving unit for receiving a spread signal; a despreading unit for despreading the received signal; an equalizing unit for equalizing the despread signal; and a spreading unit for spreading amplitude information and error information of the despread; wherein the spread amplitude information and error information are used as controlling signals in the equalizing unit.

Abstract: A correlation energy detector detects a magnitude of a correlation between a first signal series (Ii, Qi) described by I-Q orthogonal components and a predetermined second signal series (HJ). The correlation energy detector includes a correlation computing section for computing correlation values (Iij, Qij) between the first signal series (Ii, Qi) and the predetermined second signal series (HJ), and a root computing section for computing {{square root over ( )}(Iij2+Qij2)} as a root value of a sum of squares of the correlation values (Iij, Qij) obtained from the correlation computing section.

Abstract: A reception apparatus for achieving demodulation in a radio communications system using M-sequence orthogonal modulation capable of achieving a good characteristic near the error rate characteristic obtained in the case of a synchronous detection system while suppressing an increase in the size of the hardware, including a signal reproducing circuit and a reflecting circuit having a reliability computing unit for computing a certainty of a value of a correlation energy as a reliability R for the correlation energy of every Walsh number, a correcting unit for obtaining a corrected correlation energy by introducing a corresponding reliability R with respect to the correlation energies, and a maximum energy selecting unit for selecting the maximum correlation energy from among obtained corrected correlation energies based on the same and demodulating a signal corresponding to a Walsh number corresponding to this maximum correlation energy as a received signal.

Abstract: A radio communication apparatus subjects each signal which is received via a multi-path and demodulated, to a Hadamard transform at each of fingers, by use of an M-ary quadrature coding scheme, obtains correlation values of codes, combines correlation values output from fingers which obtain valid correlation values, and demodulates a received signal based on a maximum correlation value of combined correlation values. The radio communication apparatus includes an operation unit which obtains a difference between a maximum value and a second largest value of the correlation values of a corresponding one of the fingers, and a lock controller which enables and locks the correlation values output from the corresponding one of the fingers when the difference obtained by the operation unit is greater than or equal to a predetermined value.

Abstract: An apparatus for estimating phase/amplitude characteristics of a propagation path. The apparatus removes, from a receive signal on a data channel on which known information is transmitted upon being time-multiplexed between items of unknown information, transmit information on this channel, which provides phase/amplitude information indicative of phase/amplitude characteristics that this data channel has suffered over the propagation path. The apparatus further removes from a receive signal on a data channel on which only unknown information is transmitted, transmit information on this channel, which provides phase/amplitude information indicative of phase/amplitude characteristics that this data channel has suffered over the propagation path. The apparatus includes an adder for adding the two phase/amplitude information and an estimation unit for estimating, from an adder output, a phase characteristic and an amplitude characteristic that each channel has suffered over the propagation path.

Abstract: In a mobile communication receiving apparatus in which signals received on a plurality of receiving paths (branches) are combined by a combiner, correlation between noise signals contained in the signals received on respective ones of the branches is detected by a noise correlation calculating unit, and control is exercised so as to maximize signal-to-noise power ratio of the combined signal based upon the correlation calculated in the noise correlation calculating unit. Signal-to-noise power ratio can be maximized even if noise components contained in respective ones of the branch signals are mutually correlated.

Abstract: A digital modulator and digital demodulator with quadrature amplitude modulation (QAM) schemes, which are designed to modulate or demodulate RZ-coded baseband signals. The digital modulator comprises first to fourth roll-off filters and a first and second inverters connected to the second and fourth roll-off filters. It also comprises a parallel-to-serial converter to successively selects the outputs of the first roll-off filter, third roll-off filter, first inverter, and second inverter. A D/A converter converts the selected digital signal stream into an analog signal. The roll-off filters and inverters operate at a predetermined clock frequency, while the parallel-to-serial converter and the D/A converter work at a frequency four times the predetermined clock frequency. The digital demodulator reverses the above modulation process to reproduce the baseband signals.

Abstract: Disclosed is a digital modulation apparatus which comprises a quadrature amplitude modulation unit for modulating first and second baseband digital signals orthogonal to each other by means of digital cosine/sine information obtained based on information regarding a carrier frequency which is n multiple of a local frequency and a phase rotation unit provided in the input side of the quadrature amplitude modulation unit for performing phase rotation for the first and second baseband digital signals by using a difference frequency equivalent to a difference between the local frequency and a a baseband frequency. A frequency is converted into a transmitted frequency without using an analog circuit for conversion into a second frequency, a limit value of this transmitted frequency is increased, and a circuit is fully digitized to simplify and miniaturize a circuit configuration. As a result, the turning of the circuit into LSI can be facilitated, and high accuracy and high cost effectiveness can be promoted.

Abstract: A distortion compensating device provided in a receiver for compensating distortion which is added to a signal in a transmission path. The signal is generated in a multi-level modulator of a transmitter in which a digital signal is mapped to one of a plurality of specified signal points in a signal space diagram. The device includes a signal-point-position averaging circuit for producing an average signal point for each of a plurality of distributions of received signal points in the signal space diagram. A discrimination circuit in the device discriminates the average signal point closest to a received signal point from other average signal points in the signal space diagram.

Abstract: An apparatus for achieving demodulation in a radio communications system using M-sequence orthogonal modulation capable of achieving a good characteristic near the error rate characteristic obtained in the case of a synchronous detection system while suppressing an increase in the size of the hardware, including a demodulation apparatus having a reliability computing unit for computing a certainty of a value of a correlation energy as a reliability R for the correlation energy of every Walsh number, a correcting unit for obtaining a corrected correlation energy by introducing a corresponding reliability R with respect to the correlation energies, and a maximum energy selecting unit for selecting the maximum correlation energy from among obtained corrected correlation energies based on the same and demodulating a signal corresponding to a Walsh number corresponding to this maximum correlation energy as a received signal.

Abstract: The present invention relates to a clock phase detecting circuit and a clock regenerating circuit each arranged in a receiving unit of multiplex radio equipment. The receiving unit of the multiplex radio equipment includes an identifying circuit for identifying a signal obtained by demodulating a multilevel orthogonal modulation signal; a clock regenerating circuit for regenerating a signal identification clock for the identifying circuit to supply the clock to the identifying circuit; an equalizing circuit for subjecting the signal obtained by demodulating a multilevel orthogonal modulation signal to an equalizing process. A clock phase detecting unit detects the phase component of the signal identification clock based on signals input to or output from the equalizing circuit and then supplies the phase component to the clock regenerating circuit.