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Yayın Design and implementation of wideband microwave amplifiers based on Normalized Gain Function(Institute of Electrical and Electronics Engineers Inc., 2014) Köprü, Ramazan; Kılınç, Sedat; Aksen, Ahmet; Yarman, Bekir Sıddık BinboğaIn this work, we introduce the design and implementation of wideband microwave amplifiers based on "Normalized Gain Function (NGF)" method. Normalized Gain Function is defined as the ratio of desired shape or frequency response of the gain function of the amplifier to be designed and shape of the transistor forward gain function. Synthesis of input/output matching networks (IMN/OMN) of the amplifier require target gain curves as the functions of normalized gain function to be tracked in two sequential nonlinear optimization processes. A prototype low power amplifier circuit is produced and measured to show the usability of the design approach.Yayın Channel estimation for space-time block coded OFDM systems in the presence of multipath fading(IEEE, 2002) Panayırcı, Erdal; Çırpan, Hakan AliIn this paper, a computationally efficient, non-data-aided maximum a posterlori(MAP) channel estimation algorithm is proposed for orthogonal frequency division multiplexing (OFDM) systems with transmitter diversity using space-time block coding. The Alamouti's transmit diversity scheme with two transmit antennas is employed here and generalized for OFDM systems. The algorithm requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve orthogonal expansion and estimates the complex channel parameters of each subcarriers iteratively using the Expectation Maximization(EM) method, which converges to the true MAP estimation of the unknown channel. Ananalytical expression is derived for the Modified Cramer-Rao. lower bound of the proposed MAP channel estimator. The performance is presented in terms of the mean-square error for a system employing QPS signaling.Yayın Adaptive Kalman receiver for OFDM systems with transmit diversity in mobile wireless channels(Walter De Gruyter GMBH, 2004-12) Şen, Adnan; Çırpan, Hakan Ali; Panayırcı, ErdalA new joint channel tracking and symbol detection scheme is proposed in this paper for pilot symbol assisted transmit diversity OFDM systems by exploiting the correlation of the adjacent subchannels. Modelling the channel frequency response of every subcarrier corresponding to each transmit antenna as random processes, we employ Kalman filters for both channel tracking and subsequent decoding with diversity gain. Among different stochastic models, the AR model is adopted herein for channel dynamics. Since the proposed adaptive receiver uses two Kalman filters to track the variations of the channel and subsequently to detect the information symbols, they are combined in the coupled receiver structure. Finally the performance of the proposed method is studied through experimental results.Yayın IEEE 802.11BB reference channel models for light communications(IEEE, 2023-12-01) Miramirkhani, Farshad; Baykaş, Tunçer; Elamassie, Mohammed; Uysal, MuratIncreasing industrial attention to visible light communications (VLC) technology led the IEEE 802.11 to establish the task group 802.11bb 'Light Communications' (LC) for the development of a VLC standard. As a part of the standard development process, the development of realistic channel models according to possible use cases is of critical importance for physical layer system design. This article presents the reference channel models for the mandatory usage models adopted by IEEE 802.11bb for the evaluation of system proposals. The use cases include industrial, medical, enterprise, and residential scenarios. Channel impulse responses and corresponding frequency responses are obtained for each use case using a ray tracing approach based on realistic specifications for transmitters and receivers, and optical characterization of the environment.
