Effects of channel tap spacing on delay lock tracking

Roger A. Dana; Brian R. Milner; Robert L. Bogusch

doi:10.1117/12.228142

8 December 1995 Effects of channel tap spacing on delay-lock tracking

Roger A. Dana, Brian R. Milner, Robert L. Bogusch

Proceedings Volume 2601, Wireless Data Transmission; (1995) https://doi.org/10.1117/12.228142
Event: Photonics East '95, 1995, Philadelphia, PA, United States

Abstract

High fidelity simulations of communication links operating through frequency selective fading channels require both accurate channel models and faithful reproduction of the received signal. In modern radio receivers, processing beyond the analog-to-digital converter (A/D) is done digitally, so a high fidelity simulation is actually an emulation of this digital signal processing. The 'simulation' occurs in constructing the output of the A/D. One approach to constructing the A/D output is to convolve the channel impulse response function with the combined impulse response of the transmitted modulation and the A/D. For both link simulations and hardware channel simulators, the channel impulse response function is then generated with a finite number of samples per chip, and the convolution is implemented in a tapped delay line. In this paper we discuss the effects of the channel model tap spacing on the performance of delay locked loops (DLLs) in both direct sequence and frequency hopped spread spectrum systems. A frequency selective fading channel is considered, and the channel impulse response function is constructed with an integer number of taps per modulation symbol or chip. The tracking loop time delay is computed theoretically for this tapped delay line channel model and is compared to the results of high fidelity simulations of actual DLLs. A surprising result is obtained. The performance of the DLL depends strongly on the number of taps per chip. As this number increases the DLL delay approaches the theoretical limit.

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Roger A. Dana, Brian R. Milner, and Robert L. Bogusch "Effects of channel tap spacing on delay-lock tracking", Proc. SPIE 2601, Wireless Data Transmission, (8 December 1995); https://doi.org/10.1117/12.228142

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KEYWORDS

Receivers

Computer simulations

Modulation

Technetium

Signal processing

Electromagnetic simulation

Signal attenuation

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