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Maktoomi M.A.,Indian Institute of Technology Delhi | Maktoomi M.A.,University of Calgary | Akbarpour M.,IRadio Laboratory | Hashmi M.S.,Indian Institute of Technology Delhi | And 2 more authors.
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2016

In this paper, firstly, an interesting dual-frequency feature of multi-section commensurate transmission-line is reported. The property concerns with the impedance (or admittance) looking into such multi-section transmission-line terminated with a real impedance. Rigorous mathematical analysis is provided to prove the existence of the property. Secondly, as an application, novel multi-section dual-frequency impedance transformer for the real impedance is presented. The proposed transformer can be used to provide matching over much wider transformation-ratio that is otherwise impossible to realize using current state-of-the-art of dual-frequency transformers. The EM simulated and measured results exhibit good performance. © 2004-2012 IEEE.

Kwan A.K.,IRadio Laboratory | Bassam S.A.,IRadio Laboratory | Helaoui M.,IRadio Laboratory | Ghannouchi F.M.,IRadio Laboratory
PAWR 2013 - Proceedings: 2013 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications - 2013 IEEE Radio and Wireless Week, RWW 2013 | Year: 2013

A concurrent dual band predistorter implementation using look up tables is presented in this paper. The power amplifier introduces the main source of nonlinearity in a transmitter chain; and the distortion is further enhanced when sending signals in multiple carrier frequencies. Using a dual band predistorter based on a memory polynomial model allows for the compensation of these nonlinearities by taking into account both signals. Converting the coefficients to look up tables reduces the number of arithmetic operations needed in a signal processor. Results are presented with the conventional dual band predistorter and the look up table predistorter in operating bands 880 MHz and 2140 MHz, showing the linearization capability and accuracy with the proposed implementation agrees with the conventional predistorter. © 2013 IEEE.

Rawat M.,IRadio Laboratory | Rawat K.,IRadio Laboratory | Younes M.,IRadio Laboratory | Ghannouchi F.,IRadio Laboratory
Electronics Letters | Year: 2013

Reported, for the first time is a predistortion scheme for a concurrent dual-band transmitter with a dual-band concurrent Doherty power amplifier in the presence of modulator I/Q imbalance and DC offsets. Inverse PA modelling for predistortion is achieved using real valued time delayed neural networks. The model has been validated for a 10 W GaN based dual-band concurrent Doherty power amplifier for wideband code division multiple access signals at 1960 and 3500 MHz, respectively, and an adjacent channel power ratio improvement of 18 dB is reported. © The Institution of Engineering and Technology 2013.

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