An intermediate frequency (IF) variable gain amplifier (VGA) with exponential gain control for a radio receiver is fabricated in 0.25-μm CMOS technology. The techniques to improve the bandwidth and to reduce temperature dependence of gain are described. The complete VGA is composed of two stages of linearized transconductance VGA and three stages of fixed gain amplifier (FGA). The complete VGA ...

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known whether this offline memory processing constitutes a basic feature of motor learning and generalizes to the implicit learning of a sequence of eye movements. To assess this hypothesis, we have creat...

In this paper we consider the problem of estimating the propagation delays of the transmitted signals in an asynchronous direct-sequence code division multiple access (DS-CDMA) system operating over a fading channel. Two estimators based on subspace techniques are compared and the Cram er-Rao Bound, a lower bound on the variance of any unbiased estimator, is derived. Special attention is paid t...

| Most receiver designs for asynchronous Direct-Sequence Code-Division Multiple-Access systems exploit timing information to simultaneously detect the desired signal and suppress the interference. In this paper, a previously proposed MUSIC delay estimation algorithm is considered which requires no initial information and no exhaustive search of the delays. Based on a Taylor series expansion, ap...

Two variable gain amplifiers (VGAs) that adopt new approximated exponential equations are proposed in this paper. The dB-linear range of the proposed VGAs is extended more than what the approximated exponential equations predict by a bias circuit technique that adopts negative feedback. The proposed VGAs feature wide gain variation, low-power, high linearity, wide control signal range, and smal...

| In this paper we present an adaptive blind receiver for asynchronous direct sequence code division multiple access (DS-CDMA) communication over multipath channels. The algorithm can handle both multiuser interference (MUI) and intersymbol interference (ISI) by the use of a twofold spreading together with some spatial over-sampling. It is based on a blind virtual channel identiication using th...

In this paper we consider the problem of estimating the propagation delays and relative amplitudes of the transmitted signals as well as detecting the data bits in an asynchronous direct-sequence code division multiple access (DS-CDMA) system operating over a fading channel. A subspace based estimator is proposed for estimating the propagation delays. The path gains and data bits are estimated ...