... In particular, the ik th component of H, hit (T), is the far-end response on channel i at tim... more ... In particular, the ik th component of H, hit (T), is the far-end response on channel i at time T to a unit pulse on channel k, and similarly, glt(T) is tile analogous near-end response, Note that hli(T) and gii(T) are, respectively, the self-impulse response and echo response for ...
We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior... more We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles (∼10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagneticlike behavior.
A decision feedback equalizer (DFE) containing a feedback filter with both poles and zeros is pro... more A decision feedback equalizer (DFE) containing a feedback filter with both poles and zeros is proposed for high-speed digital communications over the subscriber loop. The feedback filter is composed of two sections; a relatively short finite-impulse-response (FIR) filter that cancels the initial part of the channel impulse response, which may contain rapid variations due to bridge taps, and a pole-zero filter than cancels the smoothly decaying tail of the impulse response. It is shown that the feedback filter can be adapted using existing infinite-impulse-response (IIR) adaptation techniques. Numerical results using a simulated subscriber loop impulse response show that a feedback filter with two poles adapted via a simplified gradient algorithm can offer significant improvement in mean squared error (MSE) (i.e., 3 to 4 dB at a signal-to-noise ratio of 20 dB) relative to a conventional DFE of the same complexity
Full-duplex data communications are considered over a linear, time-invariant, multi-input/multi-o... more Full-duplex data communications are considered over a linear, time-invariant, multi-input/multi-output channel. For both the continuous- and discrete-time cases, optimal multi-input/multi-output transmitter and receiver filters are derived using the minimum mean-square error (MSE) criterion, with a power constraint on the transmitted signal, in the presence of both near- and far-end crosstalk. The discrete-time problem is solved for two different filter models: arbitrary linear (IIR) (infinite-complexity) and fixed-order (FIR) filters. In addition, the optimal transmitter and receiver filters are derived for the case in which the transmitted signal is a pulse-amplitude-modulated data signal. For a particular two-input/two output channel model in the FIR case, the behavior of the MSE as a function of the allocation of matrix taps between transmitter and receiver filters and of timing phase is studied. In this case, the jointly optimal transmitter and receiver filters are obtained numerically using an iterative technique. For the channel model considered, the MSE is a very sensitive function of timing phase but is nearly independent of how taps are allocated between the transmitter and receiver filters
An alternative code division multiple access (CDMA) scheme to spread spectrum (SS), called spread... more An alternative code division multiple access (CDMA) scheme to spread spectrum (SS), called spread-time (ST), is proposed for bandlimited multiple access channels. ST-CDMA can be considered the time-frequency dual of SS-CDMA. Implementations are described in which surface acoustic wave (SAW) devices are used to perform the matched filtering or Fourier transformation. A first-order comparison of signal-to-interference ratio and spectral efficiency is given for ST- and conventional asynchronous SS-CDMA, assuming an ideal bandlimited channel
... In particular, the ik th component of H, hit (T), is the far-end response on channel i at tim... more ... In particular, the ik th component of H, hit (T), is the far-end response on channel i at time T to a unit pulse on channel k, and similarly, glt(T) is tile analogous near-end response, Note that hli(T) and gii(T) are, respectively, the self-impulse response and echo response for ...
We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior... more We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles (∼10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagneticlike behavior.
A decision feedback equalizer (DFE) containing a feedback filter with both poles and zeros is pro... more A decision feedback equalizer (DFE) containing a feedback filter with both poles and zeros is proposed for high-speed digital communications over the subscriber loop. The feedback filter is composed of two sections; a relatively short finite-impulse-response (FIR) filter that cancels the initial part of the channel impulse response, which may contain rapid variations due to bridge taps, and a pole-zero filter than cancels the smoothly decaying tail of the impulse response. It is shown that the feedback filter can be adapted using existing infinite-impulse-response (IIR) adaptation techniques. Numerical results using a simulated subscriber loop impulse response show that a feedback filter with two poles adapted via a simplified gradient algorithm can offer significant improvement in mean squared error (MSE) (i.e., 3 to 4 dB at a signal-to-noise ratio of 20 dB) relative to a conventional DFE of the same complexity
Full-duplex data communications are considered over a linear, time-invariant, multi-input/multi-o... more Full-duplex data communications are considered over a linear, time-invariant, multi-input/multi-output channel. For both the continuous- and discrete-time cases, optimal multi-input/multi-output transmitter and receiver filters are derived using the minimum mean-square error (MSE) criterion, with a power constraint on the transmitted signal, in the presence of both near- and far-end crosstalk. The discrete-time problem is solved for two different filter models: arbitrary linear (IIR) (infinite-complexity) and fixed-order (FIR) filters. In addition, the optimal transmitter and receiver filters are derived for the case in which the transmitted signal is a pulse-amplitude-modulated data signal. For a particular two-input/two output channel model in the FIR case, the behavior of the MSE as a function of the allocation of matrix taps between transmitter and receiver filters and of timing phase is studied. In this case, the jointly optimal transmitter and receiver filters are obtained numerically using an iterative technique. For the channel model considered, the MSE is a very sensitive function of timing phase but is nearly independent of how taps are allocated between the transmitter and receiver filters
An alternative code division multiple access (CDMA) scheme to spread spectrum (SS), called spread... more An alternative code division multiple access (CDMA) scheme to spread spectrum (SS), called spread-time (ST), is proposed for bandlimited multiple access channels. ST-CDMA can be considered the time-frequency dual of SS-CDMA. Implementations are described in which surface acoustic wave (SAW) devices are used to perform the matched filtering or Fourier transformation. A first-order comparison of signal-to-interference ratio and spectral efficiency is given for ST- and conventional asynchronous SS-CDMA, assuming an ideal bandlimited channel
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Papers by Pedro Crespo