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Antennas and Propagation Magazine, IEEE

Issue 4 • Date Aug. 1992

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Displaying Results 1 - 4 of 4
  • Channel characteristics for land cellular radio, and their systems implications

    Publication Year: 1992 , Page(s): 7 - 16
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    Characterization of the channel, in terms that are useful for system design and performance evaluation, is addressed. An attempt is made in the current effort to link physical features of the environment to some deterministic characteristics of the channel, and to a better characterization of the statistical behavior. The predictions are then validated by an extensive measurement campaign, with an impulse channel sounder, covering many major urban areas in the US. Previous results and analysis are then revisited, to further support the findings. The delay profile is found to consist mostly of distinct peaks, shifting in delay as the mobile unit travels, and resulting from reflections from large structures. These are relatively stable compared to the leading peak, which consists of the direct path and signals from a cluster of neighboring scatterers. Signal bandwidth effects and the effectiveness of different diversity means are discussed in terms of the channel characteristics.<> View full abstract»

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  • Some fun with Bessel functions

    Publication Year: 1992 , Page(s): 17 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB)  

    A theoretical investigation of generating functions is pursued using the theory of the Z-transform. Bessel functions are viewed as outputs from infinite impulse response (IIR) filters. It is shown that a single second-order linear ordinary differential equation with nonconstant coefficients defines a family of generating functions for all the Bessel functions of integral order. A numerical method that directly makes use of the three-term recurrence relation, as a tri-diagonal set of equations solved by Gaussian elimination, is proposed for their evaluation. What results is that both J/sub n/ and Y/sub n/, for each n, are derived at the cost of one floating-point division and four floating-point multiplications, after initial set up, using an algorithm that has possibilities for parallelization.<> View full abstract»

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  • Surface losses in transmission lines

    Publication Year: 1992 , Page(s): 22 - 26
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB)  

    Two derivations of the loss parameter R, entirely from wave considerations in the presence of a metallic interface, are presented. R, which represents surface losses, occurs in transmission line equations for propagation of the voltage across the plates and of the current in the plates. Explanation of the surface losses involves some radiation of the interior fields into the metallic surfaces that absorb electromagnetic energy, and that ultimately convert it into ohmic losses (heat). Although the approach may restrict the derivation to a planar interface, i.e., to a parallel-plate transmission line, that restriction is not so essential that it cannot be softened.<> View full abstract»

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  • Approximations for computing the weighting parameters for one-parameter Taylor and Hansen aperture distributions

    Publication Year: 1992 , Page(s): 34 - 35
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (151 KB)  

    Approximations are presented for determining the weighting parameters for one-parameter linear- and circular-aperture distributions, when the desired mainlobe-to-sidelobe ratio is known. These approximations may be more convenient to use than the iterative methods or lookup tables that have been suggested previously in the literature. Both approximations exhibit worst-case errors of less than +or-0.1 dB, for peak sidelobe ratios up to 82 dB.<> View full abstract»

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