Nowadays, it is easy to find radio transceivers having small size, low cost and still offering numerous functionalities. High-integration of radio-frequency (RF) circuits is still the main trend in the development of wireless devices. A down-converter is an essential part of any RF receiver. It basically performs the frequency translation between an incoming RF signal into a lower frequency to ...

We study the performance of differential spacetime codes with linear constellation precoding (LCP) for orthogonal frequency division multiplexing (OFDM) cooperative networks over frequency selective channels. Through exploiting the unitary structure of the orthogonal STBCs, we design a low complexity differential STBC-LCP-OFDM receiver for cooperative networks. We assume the amplify-and-forward...

Nowadays, MIMO systems are playing an important role in wireless communications. In this paper, we propose a spatial-temporal adaptive MIMO beamforming scheme for single carrier transmission in frequency-selective fading channels with the assumption of perfect channel state information (CSI) at both the transmitter and receiver. The transmit and receive weight vectors for detecting the precedin...

This paper presents a novel spectrum-allocation technique designed for a high data-rate and spectrally-efficient multiple-user wireless system. The core of this system is a reconfigurable radio, implemented on a General-Purpose Processor (GPP) platform. A type of Dynamic Orthogonal Frequency Division Multiplexing Multiple Access (DOFDMA) is used to transmit a multiplex of several information so...

New generation wireless systems target to support much higher data rate which requires larger bandwidth than the existing systems. Lack of contiguous spectrum resources and the compatibility requirement with the legacy systems make the concept of carrier aggregation (CA) a practical means for supporting high data rate in next generation systems. One of the practical issues related to the CA is ...

Orthogonal frequency division multiplexing (OFDM) is, with substantial progress in digital signal processing, becoming an important part of the telecommunications arena. The most appealing feature of OFDM is the simplicity of the receiver design due to the efficiency with which OFDM can cope with the effects of frequency-selective multipath channels. Multicarrier systems such as OFDM are, howev...

We are going to implement and study a space frequency coded OFDM system which consists of two transmitters and a single receiver. Simple Alamouti spacetime code is used. An M-ary PSK modulation is used to modulate the symbols across an OFDM channel. We will also propose a variation of the scheme which tries to spread additional symbols across time-frequency attempting to increase the rate of tr...

Recent commercial developments in the optical fiber industry have raised the possibility of supplying the local oscillator signal for the MMA by generating two optical signals differing in frequency by the required local oscillator frequency. These two optical signals may then be transmitted over a single optical fiber to each antenna. Within the receiver dewar, the two optical signals are mixe...

The conventional approach to generating local oscillator (LO) power for millimeterand submillimeter-wave heterodyne mixers is to generate power at a lower frequency using a suitable phase-locked source, and to convert this power to the desired commensurate frequency using a nonlinear diode such as a varactor in a frequency multiplier circuit. Although useful for single-dish telescope receiver s...