scispace - formally typeset
Search or ask a question
Author

Hiroyoshi Ishikawa

Bio: Hiroyoshi Ishikawa is an academic researcher from Fujitsu. The author has contributed to research in topics: Signal & Distortion. The author has an hindex of 16, co-authored 102 publications receiving 1102 citations.


Papers
More filters
Patent
22 Dec 2000
TL;DR: In this article, a delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals.
Abstract: A distortion compensating apparatus for compensating for a distortion of a transmission power amplifier. A delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals, and decides the total delay time caused in the transmission power amplifier and a feedback loop on the basis of the phase difference in which the correlation is the maximum. A delay unit delays the transmission signal before a distortion compensation processing by the total delay time, and inputs the delayed signal into a distortion compensating apparatus arithmetic unit, which calculates and stores a distortion compensation coefficient on the basis of the transmission signal and the feedback signal fed back from the output side of the transmission power amplifier. A pre-distortion unit applies a distortion compensation processing to the transmission signal by using the distortion compensation coefficient.

204 citations

Patent
16 Dec 2008
TL;DR: In this article, a power amplifying apparatus includes a high-speed low pass filter which inputs an envelope signal included in a transmission signal, a low speed low-pass filter that inputs the envelope signal and determines rising or falling of the signal, and a selecting unit which selects one of the high speed low pass filters and the low speed filter according to a determined result of the determination unit.
Abstract: A power amplifying apparatus includes a high-speed low pass filter which inputs an envelope signal included in a transmission signal therein, a low-speed low pass filter which inputs the envelope signal therein, a determination unit which inputs the envelope signal therein and determines rising or falling of the envelope signal, a selecting unit which selects one of the high-speed low pass filter and the low-speed low pass filter according to a determined result of the determination unit, and a voltage supply unit which generates a voltage based on a signal input according to a selection by the selecting unit and supplies the voltage to a power amplifier which inputs the transmission signal therein so as to amplify a power of the transmission signal.

65 citations

Patent
15 Oct 2003
TL;DR: In this article, the authors present 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 compensated processing to a distorting device, calculating the distortion compensation coefficient based on the input signal before distortion compensation and the feedback signal fed back from the output side of the distorting devices.
Abstract: 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.

44 citations

Patent
Hiroyoshi Ishikawa1, Kazuo Nagatani1, Hajime Hamada1, Nobukazu Fudaba1, Tokuro Kubo1 
24 Mar 2006
TL;DR: In this paper, a timing controller is described that includes an amplifier part, a detector part, and a delay corrector part, each of which is configured to correct the delay of a second input signal in accordance with the timing control signal.
Abstract: A timing controller is disclosed that includes: an amplifier part configured to amplify a first input signal in accordance with a control voltage, the first input signal being one of a transmission signal and a signal of a fixed value; a detector part configured to detect envelope information from the output signal of the amplifier part; a controller part configured to determine a delay difference from the transmission signal and the envelope information and transmit a timing control signal based on the delay difference; and a delay corrector part configured to correct the delay of a second input signal in accordance with the timing control signal, the second input signal being one of the transmission signal and a signal of a fixed value. One of the first and second input signals employs the corresponding signal of the fixed value in the case of correcting the delay.

43 citations

Patent
14 Mar 2001
TL;DR: In this article, a feedback loop for updating a distortion compensation coefficient is opened and closed, and then the distortion compensation table is generated and after the generation is completed, the operation shifts to the normal operation.
Abstract: First, a digital section constituting a linearizer is activated. Then, a feedback loop for updating a distortion compensation coefficient is opened. Then, the analog section on the antenna side is activated from an ADC, including a PA, etc., or a DAC. Then, both the ATT value of an ATT installed in a feedback route for updating the distortion compensation coefficient and the signal delay amount of a signal delay unit are adjusted to make a state such that the distortion compensation coefficient can be accurately updated. Then, the feedback loop is closed, a distortion compensation table having the distortion compensation coefficient as an entry is generated and after the generation is completed, the operation shifts to the normal operation.

43 citations


Cited by
More filters
Patent
22 Dec 2000
TL;DR: In this article, a delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals.
Abstract: A distortion compensating apparatus for compensating for a distortion of a transmission power amplifier. A delay time decision unit calculates the correlation between a transmission signal and a feedback signal fed back from the output side of the transmission power amplifier while varying phase difference between both signals, and decides the total delay time caused in the transmission power amplifier and a feedback loop on the basis of the phase difference in which the correlation is the maximum. A delay unit delays the transmission signal before a distortion compensation processing by the total delay time, and inputs the delayed signal into a distortion compensating apparatus arithmetic unit, which calculates and stores a distortion compensation coefficient on the basis of the transmission signal and the feedback signal fed back from the output side of the transmission power amplifier. A pre-distortion unit applies a distortion compensation processing to the transmission signal by using the distortion compensation coefficient.

204 citations

Patent
Fan Teng1, Chao Wei1, Gang Zeng1, Yufang Yin1, Xuegang Huang1 
03 Jun 2010
TL;DR: In this paper, a method for calibrating a base station comprising a plurality of antennas is provided, where first correction information is received from a system module, the correction information determined from first calibration of the base station Signals are received at a radio frequency module from at least one antenna of the BS.
Abstract: A method for calibrating a base station comprising a plurality of antennas is provided First correction information is received from a system module, the correction information determined from first calibration of the base station Signals are received at a radio frequency module from at least one antenna of the base station Second correction information is determined on the basis of the received signals and the first correction information.

137 citations

Patent
21 Dec 2010
TL;DR: In this article, the authors proposed a method of using duplexers and/or interference cancellation system technique to increase the isolation between the transmitter signal and receiver signal of the RRU.
Abstract: A remote radio head unit (RRU) system for multiple operating frequency bands, multi-channels, driven by a single or more wide band power amplifiers. More specifically, the present invention enables multiple-bands RRU to use fewer power amplifers in order to reduce size and cost of the multi-band RRU. The present invention is based on the method of using duplexers and/or interference cancellation system technique to increase the isolation between the transmitter signal and receiver signal of the RRU.

134 citations

Patent
06 Feb 2012
TL;DR: In this article, a method of calibrating an envelope tracker having an envelope shaping table generated at a desired gain compression of a power amplifier is provided. But the method is not suitable for the measurement of the output power of the power amplifier.
Abstract: Apparatus and methods for envelope tracking calibration are provided. In one embodiment, a method of calibrating an envelope tracker having an envelope shaping table generated at a desired gain compression of a power amplifier is provided. The method includes generating a supply voltage for the power amplifier using the envelope tracker, operating the supply voltage of the power amplifier at a first voltage level associated with substantially no gain compression of the power amplifier, and measuring an output power of the power amplifier at the first voltage level. The method further includes decreasing a voltage level of the supply voltage one or more times and measuring the output power at each voltage level, determining a second voltage level of the power amplifier associated with a gain compression equal to about that of the desired gain compression, and calibrating the envelope tracker based on the determination.

130 citations

Patent
Jason T. Young1, Dennis Mahoney1, Ricke W. Clark1, Nadim Khlat1, Adam Toner1 
23 Aug 2005
TL;DR: In this article, a method for calibrating the output power of a mobile terminal using at least a second order curve fit to describe a power amplifier gain (PAG) setting versus output power characteristic of the power amplifier in a transmitter of the mobile terminal is provided.
Abstract: A method for calibrating the output power of a mobile terminal using at least a second order curve fit to describe a power amplifier gain (PAG) setting versus output power characteristic of a power amplifier in a transmitter of the mobile terminal is provided. For each of an upper-band frequency, a mid-band frequency, and a lower-band frequency of a frequency band, multiple measurements of the output power of the mobile terminal are made corresponding to multiple values of the PAG setting, and a curve fit is performed, thereby calculating coefficients defining a polynomial describing the PAG setting versus output power characteristic. Using the polynomials describing the PAG setting versus output power characteristic of the power amplifier for each of the upper-band, mid-band, and lower-band frequencies, values of the PAG setting are determined for each desired output power level for each desired frequency within the frequency band.

122 citations