A/D's Clipping Restrictions in Software Radios

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A/D's Clipping Restrictions in Software Radios. Vasilis Christofilakis α,b. , Giorgos Tatsis α. , Constantinos Votis α. , Vasilis Raptis α. ,. Panos Kostarakis α.
A/D’s Clipping Restrictions in Software Radios Vasilis Christofilakisα,b, Giorgos Tatsisα, Constantinos Votisα, Vasilis Raptisα, Panos Kostarakisα a

b

Physics Department, University of Ioannina, Panepistimioupolis, Ioannina, 45110, Greece Siemens Enterprise Communications, Enterprise Products Development, Athens, 14564, Greece

Abstract. Analog-to-Digital Converter (A/D) is a critical component of Software Radio (SWR). Various hardware restrictions and errors are limiting SWR’s performance. In this paper the performance of a SWR receiver is evaluated considering A/D’s clipping noise. Significant results are given, in terms of clipping noise, in combination with aperture jitter and quantization error. Keywords: Clipping, A/D, Software Radio, PACS: 84.40.Ua

INTRODUCTION It is well known that A/D constitutes an essential component in the implementation of an ideal SWR receiver. In this paper, we adopt the consideration that the A/D is a physically realizable system and its performance depends on various parameters [1]. Analysis and results of previous works was limited to parameters such as sampling frequency, quantization and aperture jitter error [2-5]. In the present analysis, clipping occurring whenever the input amplitude signal exceeds the maximum range of the quantizer are taken into account. Numerical simulations were carried out, considering that the carrier frequency of RF signal lies in IMT-2000 frequency band and the sampling rate was at least equal to the Nyquist rate. The paper is structured as follows. Performance of the ideal SWR receiver defined by the total Signal to Noise Radio (SNRt) at the A/D’s output is presented for negligible clipping error in section 2. The effect of the clipping to the system’s performance is given in section 3. Conclusions are drawn in Section 4.

NEGLIGIBLE AMPLITUDE DISTRIBUTION AND CLIPPING ERROR The SNRt is estimated at the A/D’s output considering only the effect of aperture jitter and quantization error. The bit resolution is assumed to be varying from 1-24 bits and aperture jitter values from 0.01 to 0.2 ps with 10 fs increment. The corresponding 3D diagram is shown in Figure 1 indicating that, for t aj