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Masahiko YAMAZOE,Kazuhisa HAEIWA,Shoji HIROSE,Masayoshi FUKUMOTO,Hideo SATO 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
We developed an evolutional wideband (3 to 26㎒) short-wave transmitter with an output of 1㎾ using PSM (Pulse Step Modulation) that digital (DRM: Digital Radio Mondiale) and analog AM modulation are possible. This equipment employs digital processed PSM method that high sound quality can be easily achieved in the modulation section and Class-E amplification for obtaining higher efficiency in the PA section composed of eight 125W PA. In addition, new output circuit for phase compensation of the load impedance. As a result, in the 125W PA, a drain efficiency of 95% at 3.925㎒ and 86% at 25.885㎒ was obtained. As analog AM characteristics, S/N of 54㏈ and above, distortion factor of 4% and under were obtained ranging from 3M to 26㎒. In digital modulation (DRM), S/N of about 24.5㏈ (at 25.885㎒ at 16QAM) that satisfies target performance sufficiently was obtained.
RF Energy Harvesting and Charging Circuits for Low Power Mobile Devices
Ahn, Chang-Jun,Kamio, Takeshi,Fujisaka, Hisato,Haeiwa, Kazuhisa The Institute of Electronics and Information Engin 2014 IEIE Transactions on Smart Processing & Computing Vol.3 No.4
Low power RF devices, such as RFID and Zigbee, are important for ubiquitous sensing. These devices, however, are powered by portable energy sources, such as batteries, which limits their use. To mitigate this problem, this study developed RF energy harvesting with W-CDMA for a low power RF device. Diodes are required with a low turn on voltage because the diode threshold is larger than the received peak voltage of the rectifying antenna (rectenna). Therefore, a Schottky diode HSMS-286 was used. A prototype of RF energy harvesting device showed the maximum gain of 5.8dBi for the W-CDMA signal. The 16 patch antennas were manufactured with a 10 dielectric constant PTFT board. In low power RF devices, the transmitter requires a step-up voltage of 2.5~5V with up to 35 mA. To meet this requirement, the Texas Instruments TPS61220 was used as a low input voltage step-up converter. From the evaluated result, the achievable incident power of the rectenna at 926mV to operate Zigbee can be obtained within a distance of 12m.
ISI and ICI Compensation for TFI-OFDM in Time-Variant Large Delay Spread Channel
Yuta Ida,Chang-Jun Ahn,Takeshi Kamio,Hisato Fujisaka,Kazuhisa Haeiwa 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In general, if the maximum delay spread is longer than guard interval (GI), the system performance is significantly degraded. The conventional time-frequency interferometry (TFI) for OFDM does not consider with timevariant large delay spread channel. In this paper, we propose a novel time domain inter-symbol-interference (ISI) cancellation scheme with replica signal based inter-carrierinterference (ICI) compensation for TFI-OFDM.
Performance Enhancement of TFI-OFDM with Path Selection based Channel Identification
Takeshi Yoshimura,Chang-Jun Ann,Takeshi Kamio,Hisato Fujisaka,Kazuhisa Haeiwa 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
Recently time-frequency interferometry (TFI)-OFDM has been proposed as a channel identification scheme. TFI-OFDM system can multiplex the same impulse response in twice on the time domain without overlapping to each other. In this case, the required pilot signal is only one. Moreover, by averaging of these impulse responses, the accurated channel impulse responses are obtained. However, if the total channel paths are reduced, the performance might be degraded. This is because the channel identification of TFI-OFDM is operated with averaging the selected spectrum signals from the time windows. For the case with reduced channel paths, the selected time spectrum signals include the noise terms. By applying the FFT operation, these noise terms are spread in the frequency domain. In this case, the channel identification is poorly operated due to the noise. To reduce this problem, in the paper, we propose the channel identification method with path selection for performance enhancement of TFI-OFDM.
Decision Direct and Linear Prediction based Fast Fading Compensation for TFI-OFDM
Masanori Yofune,Chang-Jun Ahn,Takeshi Kamio,Hisato Fujisaka,Kazuhisa Haeiwa 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
Recently, time-frequency interferometry (TFI)-OFDM has been proposed as a channel identification scheme. TFI-OFDM system can multiplex the same impulse response in twice on the time domain without overlapping to each other. Moreover, by averaging of these impulse responses, the accurated channel impulse responses are obtained. However, under the fast fading channel, the change of channel conditions is too fast to be followed by channel estimator in the receiver. Therefore, too many errors occur in data demodulation processing particularly in the last part of data symbols. To overcome this problem, in this paper, we propose the decision direct and linear prediction based fast fading compensation method for TFI-OFDM.