Mohammad Mojtaba Ebrahimi

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This paper presents a development of a wideband deltasigma modulator for fully digital GHz transmitters. The fully digital RF transmitter is developed as a promising solution for software defined radio (SDR) terminals and applications. The fully digital transmitter consists of a delta-sigma modulator, a highspeed multiplexer and a switching-mode power(More)
In this paper the Coding Efficiency in multi-bit delta-sigma based transmitters has been improved significantly by only adjusting the quantizer’s threshold values. To achieve this, the transmitter’s linearity should be compromised. Usually the space between thresholds in a quantizer of a multibit delta-sigma modulator is uniform which not the optimum choice(More)
This paper introduces two new techniques to enhance both efficiency and signal bandwidth in delta-sigma-based transmitters. At first step, a technique called quantization noise reduction (QNR), is introduced to enhance the coding efficiency. By filtering out part of the quantization noise in the whole band of the signal, while the signal envelope is(More)
This paper proposes a complete transmitter prototype for wireless applications using envelope tracked pulsed gate modulated power amplifier (PA). The proposed transmitter architecture is developed using two high power 10 W gate modulated PAs combined in a fashion to operate as a switched voltage source for the range of duty cycles of pulses driving the(More)
This work proposes a method to enhance the efficiency of a WiMAX switching mode GaN power amplifier through the layout optimization of harmonic matching networks. In the first step, the optimal termination conditions for the inverse class F power amplifier are extracted through load-pull measurement. Afterward, the loss in the multiharmonic output matching(More)
In this paper a comparative study of 10 watt GaN polar transmitters for base-station application is carried out. Two main topologies are compared and studied. In the first topology, the drain of the transistor is modulated with the pulse format of the signal's envelope, and in the modified topology, the gate of the transistor is modulated with the pulse(More)
This paper proposes a harmonic matching network with minimum loss based on precise harmonic load pull measurement to enhance the efficiency and gain for harmonic matched power amplifiers. In this method, the number of stubs for harmonic matching network was reduced in order to minimize the loss and increase the efficiency. A power amplifier with a GaN(More)
This paper proposes a linear and efficient transmitter prototype based on pulsed load modulation (PLM) power amplifier (PA). The proposed transmitter setup utilizes the complex delta–sigma (DS) modulation as a signal processing technique instead of the envelope DS modulation for higher linearity performance. Using the complex DS modulation technique(More)
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