Philipp Walk

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In this note we show that stable recovery of complex-valued signals x &#x03F5; C<sup>n</sup> up to a global sign can be achieved from the magnitudes of 4n - 1 Fourier measurements when a certain symmetrization and zero-padding is performed before measurement (4n - 3 is possible in certain cases). For real signals, symmetrization itself is linear and(More)
In this paper we show that convolutions of sufficiently sparse signals always admit a non-zero lower bound in energy if oversampling of its Fourier transform is employed. This bound is independent of the signals and the ambient dimension and is determined only be the sparsity of both input signals. This result has several implications for blind system and(More)
For several communication models, the dispersive part of a communication channel is described by a bilinear operation T between the possible sets of input signals and channel parameters. The received channel output has then to be identified from the image T(X, Y) of the input signal difference sets X and the channel state sets Y. The main goal in this(More)
In this contribution we present a novel method for constructing orthogonal pulses for UWB impulse radio transmission under the FCC spectral mask constraint. In contrast to previous work we combine a convex formulation of the spectral design with Lowdin's orthogonalization method [1], which delivers a shift--orthogonal basis optimally close &#40;in(More)
The success of the compressed sensing paradigm has shown that a substantial reduction in sampling and storage complexity can be achieved in certain linear and non–adaptive estimation problems. It is therefore an advisable strategy for noncoherent information retrieval in, for example, sporadic blind and semi–blind communication and sampling problems. But,(More)
In this paper we consider the design of spectrally efficient time-limited pulses for ultra-wideband (UWB) systems using an overlapping pulse position modulation scheme. For this we investigate an orthogonalization method, which was developed in 1950 by Löwdin [1, 2]. Our objective is to obtain a set of N orthogonal (Löwdin) pulses, which remain time-limited(More)