Digital Signal Processing 20 (2010) 496–501 Contents lists available at ScienceDirect Digital Signal Processing www.elsevier.com/locate/dsp Linearizer for pulse-shaping of received pulse in ultra-wideband radio systems Ajay K. Singh a , Pradeep Kumar b , G. Singh b,∗ , T. Chakravarty c a Department of Computer Science & Engineering and IT, Jaypee University of Information Technology, Solan 173215, India b Department of Electronics and Communication Engineering, Jaypee University of Information Technology, Solan 173215, India c Tata Consultancy Services, Abhilash Software Development Centre, Plot No. 96, EPIP Industrial Area, Whitefield, Bangalore 560066, India article info abstract Article history: Available online 5 August 2009 Keywords: Ultra-wideband Group delay Linearizer Pulse shaping Radio systems Radar This paper presents a novel concept of pulse-shaping in an ultra-wide band radio system. Instead of attempting to design an antenna with flat group delay, the emphasis has been shifted to the signal processing aspect of pulse shaping. The received pulse which has broadened due to non-linear phase response of the propagating channel is shaped back closer to the ideal pulse using a linearizer. The block schematic of the linearizer is presented along with simulated results. Though only a Rayleigh first order pulse has been used for simulation purpose, the method can easily be generalized to incorporate other pulse shapes.  2009 Elsevier Inc. All rights reserved. 1. Introduction After recognizing the potential advantages of the ultra-wideband (UWB) systems in 2002, the Federal Communications Commission (FCC) allotted the band of spectrum from 3.1 GHz to 10.6 GHz for unlicensed use for the communications and imaging technology. The UWB definition was created as a signal with a fractional bandwidth greater than twenty percent or which occupies more than 500 MHz of the spectrum. For the communication applications, high data rates are possible due to the large number of pulses that can be created in short time duration. The pulses are short in time duration and thus millions of pulses could be sent in a second so that a near perfect image of the target is obtained. The advantage of using UWB in this application is that due to its inherent time resolution property it reduces post detection signal processing as is required in narrowband radio systems to improve the detected image. Due to its low power spectral density, it can be used in military applications which require low probability of detection. The UWB underground penetrating radio systems such as radars can be used to find the live things in the rubble. These kinds of systems can be used in numerous other potential applications. The UWB technology is popular for its multipath immunity, high data throughput, better wall penetration, low power consumption, and low probability of interception and detection. Because of all these interesting features, it has been increasingly accepted for numerous applications in the civilian and military fields. Chen et al. [1] have presented two vital design considerations for pulse shaping in the UWB radio systems. First is the radiated power density spectrum shaping must comply with certain emission limit and controlled by selecting the source pulses. Another is the design of source pulses and transceiver antennas for optimal performance of overall systems are ex- plained nicely. In this paper [1], a frequency dependent transmission equation based on the Frii’s transmission formula is employed to describe the transceiver antenna systems. Then the selection of source pulses is performed with emission con- trol consideration. The received pulses are studied using both narrowband and wideband antenna system. Cramer et al. [2] * Corresponding author. E-mail address: drghanshyam.singh@yahoo.com (G. Singh). 1051-2004/$ – see front matter  2009 Elsevier Inc. All rights reserved. doi:10.1016/j.dsp.2009.08.001