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 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:
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:
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:
A distortion correction control apparatus is for compensating for a burst distortion of a transmission amplifier caused by a burst of an input signal of a transmission target. The apparatus includes a generation unit that generates a distortion correction coefficient having reverse characteristics to the foregoing burst distortion; a unit that multiplies the distortion correction coefficient output from the generation unit by the input signal or adds the distortion correction coefficient output from the generation unit to the input signal, upon reception of burst information notifying of switching between presence and absence of the input signal; and an update unit that updates, based on the input signal and a branch signal fed back as an output signal of the transmission amplifier, parameters of functions used for adaptively generating the distortion correction coefficient, and that inputs the updated parameters to the generation unit.
摘要:
A distortion compensating apparatus calculates a distortion compensation coefficient in such a manner that a difference signal between a reference signal, which is a transmit signal, and a feedback signal will be diminished, updates an old distortion compensation coefficient by the calculated distortion compensation coefficient and applies distortion compensation to the transmit signal based upon this distortion compensation coefficient. In this apparatus, a phase correcting interval, which is for correcting the phase difference between the reference signal and the feedback signal, and a distortion compensation coefficient updating interval are generated alternately, a correction is applied so as to null the phase difference in the phase correcting interval, and the distortion compensation coefficient is updated in the distortion compensation coefficient updating interval.
摘要:
The distortion compensator which compensates the nonlinearity of a power amplifier in a radio communication device stops the operation of updating the automatic phase adjustment, automatic delay adjustment, equalizer adjustment, and distortion compensation table when something wrong is detected in the input to a distortion compensation unit such as a reference signal, feedback signal, address of the distortion compensation table, and phase value so that the distortion compensation coefficients may not be improperly updated.
摘要:
In a distortion compensation device which uses distortion compensation coefficients to subject distortion compensation processing to an input signal and supply the result of the distortion compensation processing to a distorting device, calculates the distortion compensation coefficients based on the input signal before distortion compensation and the feedback signal fed back from the output side of the distorting device, and stores the calculated distortion compensation coefficients in association with the input signal, (1) the feedback signal is AD-converted; (2) the AD-converted output is subjected to fast Fourier transform (FFT) processing; (3) the FFT calculation result is used to calculate the value of either the signal-to-noise ratio SNR, or the adjacent channel leakage power ratio ACLR, or the noise level; (4) the delay time occurring in the distorting device and feedback loop is adjusted such that the difference between the above calculated value at the current time and the above calculated value at the immediately preceding time is either zero, or is equal to or less than a threshold value; and, (5) this adjustment processing is repeated to determine the accurate delay time, and based on this delay time the timing of each of the portions of the distortion compensation device is adjusted.
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 distortion compensation apparatus of the present invention is used in a transmitter that produces and outputs a second signal from a first signal. This apparatus comprises a delay unit for delaying a feedback signal obtained from by the second signal; and a delay control unit for determining a delay quantity of said delay means so that a timing difference between a reference signal obtained from the first signal and the feedback signal delayed by the delay unit is made small. The delay control unit limits the delay quantity within a predetermined limit value.