In order to meet future communication system requirements channel estimation over fast fading and frequency selective channels is crucial. In this paper Space Alternated Generalized Expectation Maximization Maximum a Posteriori (SAGE-MAP) based channel estimation algorithm is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems for Autoregressive (AR) modeled time-varying sparse channels. Also an initialization algorithm has been developed from the widely used sparse approximation ...

In this paper explicit amplitude and frequency expressions for a Cellular Neural Network with an Opposite-Sign Template (CNN-OST) under oscillation condition are derived and a novel inductorless oscillator circuit with negative feedbacks based on this simple structure is designed and implemented. The system is capable of generating quasi-sine signals with tuneable amplitude and frequency which can't be provided at the same time in the classical oscillator circuits.

A practical method is introduced to design single-stage broadband microwave amplifiers with mixed lumped and distributed elements via modeling the reflectance data obtained from lumped-element input and output matching network prototypes. The same transducer power gain level is obtained by using less number of lumped-elements in the mixed-element amplifier than that of the lumped-element amplifier prototype. A mixed-element amplifier design is presented to exhibit the utilization of the method. ...

A reflectance-based modeling method is presented to obtain the distributed-element counterpart of a lumped-element network which is described by measured or computed reflectance data at a set of frequencies. Numerical generation of the scattering parameters forms the basis of this modeling tool. It is not necessary to select a circuit topology for the distributed-element model which is the natural consequence of the modeling process. Our approach supplements the known interpolation methods by a ...

In this paper, calculation of parameters of low-pass ladder networks with mixed lumped and distributed elements by means of artificial neural networks is given. The results of ANN are compared with the values that are desired. It has been observed that the calculated and the desired values are extremely close to each other. So this algorith can be used to obtain the parameters that will be used to synthesize such circuits.

Generally at high frequencies, lumped-elements are not preferred because of their limited range of values. Therefore, in this work, a kind of phase shifter formed with ladder stubs is studied and a new approach to design phase shifter's low pass and high pass sections which are composed of series or shunt connected open-ended or short-ended stubs is proposed. In the approach, since the main focus is to form low pass and high pass two-port sections, switching process is not considered. First, the ...

It is always preferable to use commercially available software tools to design broadband matching networks for microwave communication systems. However for these tools the matching network topology and element values must be selected properly. Therefore in this paper a practical method is presented to generate matching networks with good initial element values. Eventually the performance of the designed matching network is optimized by employing the commercially available computer-aided design ...

It is a common practice to utilize commercially available software tools to design matching networks for wireless communication systems. Most of these tools require a properly selected matching network topology with good initial element values. Therefore in this paper a practical method is presented to generate matching networks with initial element values. In the implementation process of the proposed method first the driving point immitance data for the matching network is obtained in a straight ...

In literature, there exist some tables containing normalized element values, to design low-pass lumped-element prototype filters with several different responses like maximally flat or equal-ripple. In this work, an algorithm is presented, to form such tables for stepped impedance prototype filters. By using the proposed algorithm, a table for 0.5 dB equal-ripple stepped impedance prototype filter is formed. Then a design example is given, to show the utilization of the formed table.

Recent studies in cognitive radios consider the detection of multiple bands for a better utilization of the spectrum. If the cognitive radio (CR) is an ultra wideband (UWB) or a wideband system then the CR should ensure all the coexisting primary systems in these bands are detected before the CR can start data transmission. In this work we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may ...