This paper addresses hardware design issues of a mobile receiver for future generation direct sequence CDMA wireless communication systems. In the design of a mobile unit, xed-point hardware is an attractive alternative because of increased speed, reduced power consumption, and reduced hardware costs. In this paper, we focus on the xed-point implementation of `blind' detection and channel estim...

It has been recently shown that in a direct-sequence/code-division multiple-access (DS/CDMA) system employing binary phase-shift keying (BPSK) modulation the baseband equivalent of the CDMA multiplex is, under very mild assumptions, an improper complex random process, i.e., it has a nonzero pseudoautocorrelation function. In this correspondence, the problem of linear multiuser detection for asy...

In this paper, a 2.4GHz low power downconversion mixer with high linearity for direct-conversion receivers based on a standard 0.18um CMOS technology is proposed. In the circuit design, Gilbert cell architecture and Common-Gate configuration are used. A simple buffer is applied in the IF output. Simulation results show that the mixer can operate at 2.4GHz and obtain the conversion gain of 11.08...

This paper analyses two front-end receiver architectures intended for GSM900 use; (i) A direct-conversion receiver, and (ii) a low-IF receiver using a poly-phase filter. The aim is to determine the circuit performance required for GSM operation and to compare this to current state-of-the-art CMOS performance. The analysis shows that direct-conversion receivers fail to meet specifications when b...

Ultra low noise bolometers are required for space based astronomical observations. Extremely sensitive detectors are necessary for a deep full-sky survey of distant extragalactic sources in the submillimeter-wave region corresponding to the extraterrestrial background spectrum minimum. A deep full-sky survey is the main goal of the Submillimetron project of the cryogenically cooled telescope on...

MIMO array can obtain much more equivalent elements by using a small number of transmitters and receivers. However, according to traditional sampling theorem, a certain number of transmitters and receivers are still needed to obtain a dense equivalent array. Since the interesting targets of ground penetrating radar (GPR) are usually sparse, this paper presents a spare MIMO array GPR imaging sch...

In this paper we investigate the use of an approximate minimum bit error rate (MBER) approach to multiuser detection using recurrent neural networks (RNN). We examine a stochastic gradient adaptive algorithm for approximating the MBER from training data using RNN structures. A comparative analysis of linear and neural multiuser receivers (MUD), employing minimum mean squared error (MMSE) and ap...

The influence of timing jitter on quadrature charge sampling for a direct conversion receiver has been evaluated. In contrast to voltage sampling, the charge sampling mixer integrates the signal current instead of tracking the signal voltage. The charge sampling mixer has been applied to RF direct sampling in wireless receivers. The influence of timing jitter on charge sampling has been analyse...

Personal Communications Services (PCS) require low-power radio technologies. One such transceiver architecture employing frequency-hopped spread spectrum techniques is described. Low power and robustness are two keys to a wireless personal communications device. A frequency-hopped code-division multiple access (CDMA) scheme is chosen over other multiple access methods because it provides an inh...

This paper proposes the design of a global-scale free-space optics/quantum key distribution (FSO/QKD) network based on geosynchronous (GEO) satellite as secret source and low-Earth orbit (LEO) satellites relay nodes for multiple legitimate users ground. The continuous variable QKD (CV-QKD) protocol with dual-threshold/direct detection (DT/DD) receivers is employed. system performance analyzed b...