摘要:
A multi-carrier signal received by an antenna is converted into a signal of an IF band by an RX, and converted into an I signal and a Q signal by an quadrature detector. The I signal and the Q signal as multi-carrier signals are converted into digital signals by an A/D converter, and input to complex filters. The complex filters extract a complex signal having a specified carrier. Then, complex filters shift the center frequency of the extracted complex signal into 0 Hz. The obtained base band signal is input to a finger, and despread and demodulated. The despread and demodulated signal is RAKE synthesized by a synthesis unit, and transmitted to a signal discrimination unit.
摘要:
The present invention relates to a demodulator which receives a signal transmitted via phase modulation or multivalue QAM modulation, and decides transmitted data based on the received signal. The present invention enhances a transmission-line estimate by using tentatively decided data symbols as pilot symbols and in estimating a transmission line without a decrease in accuracy of transmission-line estimate even when an error rate of the tentatively decided data symbols is increased. The demodulator includes a pilot-based transmission-line estimation unit for estimating transmission-line characteristics by using pilot symbols. A tentative-data-decision unit for tentatively deciding data symbols based on the pilot-based transmission-line estimate. A data-based transmission-line estimation unit for estimating the transmission-line characteristics by using the tentatively decided data. Weight-coefficient-multiplication units for multiplying pilot-based and data-based transmission-line estimates by respective weights having a ratio therebetween varying in accordance with reliability of the tentatively ascertained data. A pilot&data-based transmission-line estimation unit for obtaining a transmission-line estimate by averaging weighted transmission-line estimates.
摘要:
The present invention is directed to a path searching device and a CDMA receiver employing the same, having a reduced circuit scale and operating to carry out a smaller number of operations. For a direct spreading CDMA communication system, a CDMA receiver includes a reception demodulator including an antenna, a high-frequency amplifier a band-pass filter, demodulators, etc. The CDMA receiver also has despreading units, a determination unit, and a path search device. The path search device has a sampling unit for sampling an input signal by low-speed oversampling based on an integer multiple of a chip rate and by high-speed oversampling that is faster than the low-speed oversampling, a first circuit for finding a correlative value between a spreading code and a signal provided by the low-speed oversampling and finding timing corresponding to a maximum correlative value. A second circuit for finding despreading timing according to correlative values between a signal provided by the high-speed oversampling and a spreading code corresponding to the timing provided by the first circuit.
摘要:
A phase θI1, . . . , θQ1, . . . uniquely determined for each channel is assigned to a carrier for each channel used when data I1 . . . , Q1, . . . , to be distributed among different channels are modulated. By appropriately modifying the phase of a carrier for each channel, signal points can be located in a narrower region than in a conventional region, and thereby the difference in amplitude between a signal point with a minimum amplitude and a signal point with a maximum amplitude can be reduced. Thus, the amplitude range of a signal to be covered by an amplifier for transmitting a transmission signal is reduced, and thereby an amplifier with a linearity that is not high can be used for the amplifier. Accordingly, even if the number of signal points increase, there is no need to use a large high-power amplifier, and thereby the small power and small size of the apparatus can be realized.
摘要:
The present invention reduces the scale of circuitry and shortens the code phase detection time needed to achieve initial synchronization. In a correlator for calculating correlation between a received spreading code contained in a received spread-spectrum signal and a reference spreading code, a combined code generator is included. The combined code generator outputs a combined spreading code by weighting and combining a plurality of phase-shifted reference spreading codes A1–AM. Further, an arithmetic circuit calculates correlation between the received spreading code and the plurality of phase-shifted reference spreading codes simultaneously. A phase detection circuit detects the phase difference between the received spreading code and a reference spreading code, namely the phase of the received spreading code from the results of the arithmetic operation.
摘要:
A code multiplexing wireless apparatus for amplifying a code-multiplexed signal and then transmitting the amplified signal includes the following to reduce output back-off, improve the efficiency of a power amplifier and suppress broadening of the frequency spectrum: (1) a code-multiplexed signal generator for multiplying each item of transmission data by a spreading code sequence and combining spread-spectrum modulated signals to generate a code-multiplexed signal, (2) a signal-peak suppressing unit for holding the envelope of the code-multiplexed signal below a set level, and (3) a power amplifier for amplifying the code-multiplexed signal and transmitting the amplified code-multiplexed signal from an antenna.
摘要:
There are disclosed a radiocommunication apparatus and a radiocommunication system. There are provided a receiving section capable of receiving a plurality of types of signals which have been spread through use of different spread code information according to a CDMA scheme in a transmitting-side radiocommunication apparatuses; and a spread demodulation section which carries out despread processing for the common signal portions of the plurality of types of signals received by the receiving section through use of a composite spread code formed from a plurality of spread codes. Accordingly, it becomes possible to significantly improve the quality of received signals.
摘要:
A code multiplexing transmitting apparatus spread-spectrum modulates transmission data of a plurality of channels by spreading codes that differ from one another, combines the spread-spectrum signals of each of the channels and transmits the resultant spread-spectrum modulated signal. A spread-spectrum modulating unit for each channel includes a phase shifter for shifting, by a predetermined angle channel by channel, the phase of a position vector of the spread-spectrum modulated signal of each channel. As the result of such phase control, the phases of pilot signal portions of the spread-spectrum modulated signals of the respective channels are shifted relative to one another so that the peak values of the code-multiplexed signal can be suppressed.
摘要:
SIR measurement for measuring S/N ratio, which is the ratio of a desired signal power to noise power, or S/I ratio, which is the ratio of desired signal power to interference signal power, uses a signal-point position altering unit for taking absolute values of an I component (in-phase component) and Q component (quadrature component) of a received signal to convert the received signal to a signal in the first quadrant of an I-Q orthogonal coordinate system, and for squaring the average value of the converted signal to obtain first average power (desired power) S, a received-power arithmetic unit for calculating the average value of the square of the received signal to obtain second average power, and for subtracting the desired power S from the received power to obtain noise power or interference power I, and a SIR arithmetic unit for calculating S/N ratio or S/I ratio from the desired signal power S and noise power or interference signal power I, and for outputting the ratio calculated.
摘要:
The present invention reduces the scale of circuitry and shortens the code phase detection time needed to achieve initial synchronization. In a correlator for calculating correlation between a received spreading code contained in a received spread-spectrum signal and a reference spreading code, a combined code generator is included. The combined code generator outputs a combined spreading code by weighting and combining a plurality of phase-shifted reference spreading codes A1-AM. Further, an arithmetic circuit calculates correlation between the received spreading code and the plurality of phase-shifted reference spreading codes simultaneously. A phase detection circuit detects the phase difference between the received spreading code and a reference spreading code, namely the phase of the received spreading code from the results of the arithmetic operation.