Browsing by Author "Zain Ahmed, Khan"

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    Extraction of the Third-Order 3 ×3 MIMO Volterra Kernel Outputs Using Multitone Signals
    (Institute of Electrical and Electronics Engineers Inc., 2018) Zain Ahmed, Khan; Zenteno Bolaños, Efrain; Händel, Peter; Isaksson, Magnus
    This paper uses multitone signals to simplify the analysis of 3 × 3 multiple-input multiple-output (MIMO) Volterra systems by isolating the third-order kernel outputs from each other. Multitone signals fed to an MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the third-order kernel outputs are isolated in the frequency domain. The signals are designed by deriving the conditions for the offset and spacing of the input frequency grids. The proposed technique is then validated for the six possible configurations of a 3 × 3 RF MIMO transmitter impaired by crosstalk effects. The proposed multitone signal design is used to extract the third-order kernel outputs, and their relative contributions are analyzed to determine the dominant crosstalk effects for each configuration. © 1963-2012 IEEE.
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    Multitene design for third order MIMO volterra kernels
    (Institute of Electrical and Electronics Engineers Inc., 2017) Zain Ahmed, Khan; Zenteno Bolaños, Efrain; Händel, Peter; Isaksson, Magnus
    This paper proposes a technique for designing multitone signals that can separate the third order multiple input multiple output (MIMO) Volterra kernels. Multitone signals fed to a MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the output from the MIMO Volterra kernels does not overlap in the frequency domain, hence making it possible to separate these kernels from the output of the MIMO Volterra system. The proposed technique is applied to a 2×2 RF MIMO transmitter to determine its dominant hardware impairments. For input crosstalk, the proposed method reveals the dominant self and cross kernels whereas for output crosstalk, the proposed method reveals that only the self kernels are dominant. © 2017 IEEE.
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    Using Intrinsic Integer Periodicity to Decompose the Volterra Structure in Multi-Channel RF Transmitter
    (Institute of Electrical and Electronics Engineers Inc., 2016) Zenteno Bolaños, Efrain; Zain Ahmed, Khan; Isaksson, Magnus; Händel, Peter
    An instrumentation, measurement and post-processing technique is presented to characterize transmitters by multiple input multiple output (MIMO) Volterra series. The MIMO Volterra series is decomposed as the sum of nonlinear single-variable self-kernels and a multi-variable cross-kernel. These kernels are identified by sample averages of the outputs using inputs of different sample periodicity. This technique is used to study the HW effects in a RF MIMO transmitter composed by input and output coupling filters (cross-talk) sandwiching a non-linear amplification stage. The proposed technique has shown to be useful in identifying the dominant effects in the transmitter structure and it can be used to design behavioral models and compensation techniques. © 2015 IEEE.