CIRCUIT - Grup de Recerca en Circuits i Sistemes de Comunicació
http://hdl.handle.net/2117/3801
Wed, 24 May 2017 13:51:48 GMT2017-05-24T13:51:48ZJoint symbol and chip synchronization for a burst-mode-communication superregenerative MSK receiver
http://hdl.handle.net/2117/104237
Joint symbol and chip synchronization for a burst-mode-communication superregenerative MSK receiver
López Riera, Alexis; Águila López, Francisco del; Palà Schönwälder, Pere; Bonet Dalmau, Jordi; Giralt Mas, Ma. Rosa; Moncunill Geniz, Francesc Xavier
In this paper we describe a superregenerative (SR)
MSK receiver able to operate in a burst-mode framework where
synchronization is required for each packet. The receiver is based
on an SR oscillator which provides samples of the incoming
instantaneous phase trajectories. We develop a simple yet effective
technique to achieve joint chip and symbol synchronization
within the time limits of a suitable preamble. We develop some
general results and focus on the case of the IEEE 802.15.4 MSK
physical layer. We provide details on a VHDL implementation on
an FPGA where the most complex digital processing block is an
accumulator. Simulation and experimental results are provided
to validate the described technique.
Tue, 09 May 2017 14:46:29 GMThttp://hdl.handle.net/2117/1042372017-05-09T14:46:29ZLópez Riera, AlexisÁguila López, Francisco delPalà Schönwälder, PereBonet Dalmau, JordiGiralt Mas, Ma. RosaMoncunill Geniz, Francesc XavierIn this paper we describe a superregenerative (SR)
MSK receiver able to operate in a burst-mode framework where
synchronization is required for each packet. The receiver is based
on an SR oscillator which provides samples of the incoming
instantaneous phase trajectories. We develop a simple yet effective
technique to achieve joint chip and symbol synchronization
within the time limits of a suitable preamble. We develop some
general results and focus on the case of the IEEE 802.15.4 MSK
physical layer. We provide details on a VHDL implementation on
an FPGA where the most complex digital processing block is an
accumulator. Simulation and experimental results are provided
to validate the described technique.A direct-sequence spread-spectrum super-regenerative receiver
http://hdl.handle.net/2117/104130
A direct-sequence spread-spectrum super-regenerative receiver
Moncunill Geniz, Francesc Xavier; Mas Casals, Orestes Miquel; Palà Schönwälder, Pere
Current applications of the super-regenerative receiver use narrowband modulations. In this paper a new architecture that allows incoherent detection of spread-spectrum signals is presented. A pseudorandom code generator has been added to the original circuit. It is clocked by the quench oscillator and takes advantage of the characteristic broad reception bandwidth. CDMA can be achieved via ASK and FSK modulated signals with high simplicity in the RF stage as well as low power consumption.
Fri, 05 May 2017 13:34:53 GMThttp://hdl.handle.net/2117/1041302017-05-05T13:34:53ZMoncunill Geniz, Francesc XavierMas Casals, Orestes MiquelPalà Schönwälder, PereCurrent applications of the super-regenerative receiver use narrowband modulations. In this paper a new architecture that allows incoherent detection of spread-spectrum signals is presented. A pseudorandom code generator has been added to the original circuit. It is clocked by the quench oscillator and takes advantage of the characteristic broad reception bandwidth. CDMA can be achieved via ASK and FSK modulated signals with high simplicity in the RF stage as well as low power consumption.Steady state analysis of class-E amplifier with non-linear capacitor by means of discrete-time techniques
http://hdl.handle.net/2117/103862
Steady state analysis of class-E amplifier with non-linear capacitor by means of discrete-time techniques
Águila López, Francisco del; Palà Schönwälder, Pere; Bonet Dalmau, Jordi; Giralt Mas, Ma. Rosa
A new method to determine the steady state response of switched nonlinear circuits is proposed. The method is based on a Gear discretization of the circuit equations. Additional samples of the waveform are used to describe the circuit when switching from one topology to another. Results are presented for a class-E resonant inverter.
Fri, 28 Apr 2017 16:48:48 GMThttp://hdl.handle.net/2117/1038622017-04-28T16:48:48ZÁguila López, Francisco delPalà Schönwälder, PereBonet Dalmau, JordiGiralt Mas, Ma. RosaA new method to determine the steady state response of switched nonlinear circuits is proposed. The method is based on a Gear discretization of the circuit equations. Additional samples of the waveform are used to describe the circuit when switching from one topology to another. Results are presented for a class-E resonant inverter.Steady state analysis of Chua's circuit with RLCG transmission line
http://hdl.handle.net/2117/103803
Steady state analysis of Chua's circuit with RLCG transmission line
Bonet Dalmau, Jordi; Palà Schönwälder, Pere; Águila López, Francisco del
In this paper we present a new technique to compute the steady state response of nonlinear autonomous circuits with RLCG transmission lines. Using multipoint Pade approximants, instead of the commonly used expansions around s=0 or s/spl rarr//spl infin/ accurate, low-order lumped equivalent circuits of the characteristic impedance and the exponential propagation function are obtained in an explicit way. Then, with the temporal discretization of the equations that describe the transformed circuit, we obtain a nonlinear algebraic formulation where the unknowns to be determined are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is obtained. Steady state solutions of the Chua's circuit with RLCG transmission line are computed for selected circuit parameters.
Thu, 27 Apr 2017 16:23:14 GMThttp://hdl.handle.net/2117/1038032017-04-27T16:23:14ZBonet Dalmau, JordiPalà Schönwälder, PereÁguila López, Francisco delIn this paper we present a new technique to compute the steady state response of nonlinear autonomous circuits with RLCG transmission lines. Using multipoint Pade approximants, instead of the commonly used expansions around s=0 or s/spl rarr//spl infin/ accurate, low-order lumped equivalent circuits of the characteristic impedance and the exponential propagation function are obtained in an explicit way. Then, with the temporal discretization of the equations that describe the transformed circuit, we obtain a nonlinear algebraic formulation where the unknowns to be determined are the samples of the variables directly in the steady state, along with the oscillation period, the main unknown in autonomous circuits. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknowns is obtained. Steady state solutions of the Chua's circuit with RLCG transmission line are computed for selected circuit parameters.Anharmonicity in multifrequency atomic force microscopy
http://hdl.handle.net/2117/102988
Anharmonicity in multifrequency atomic force microscopy
Santos Hernandez, Sergio; Barcons Xixons, Víctor
In multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.
Tue, 28 Mar 2017 15:50:13 GMThttp://hdl.handle.net/2117/1029882017-03-28T15:50:13ZSantos Hernandez, SergioBarcons Xixons, VíctorIn multifrequency atomic force microscopy higher eigenmodes are externally excited to enhance resolution and contrast while simultaneously increasing the number of experimental
observables with the use of gentle forces. Here, the implications of externally exciting multiple frequencies are discussed in terms of cantilever anharmonicity, fundamental period and the onset of subharmonic and superharmonic components. Cantilever anharmonicity is shown to affect and control both the observables, that is, the monitored amplitudes and phases, and the main expressions quantified via these observables, that is, the virial and energy transfer expressions which form the basis of the theory.Deconstructing the governing dissipative phenomena in the nanoscale
http://hdl.handle.net/2117/102982
Deconstructing the governing dissipative phenomena in the nanoscale
Santos Hernandez, Sergio; Amadei, Carlo Alberto; Tang, Tzu-Chieh; Barcons Xixons, Víctor; Chiesa, Matteo
An expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.
Tue, 28 Mar 2017 15:04:11 GMThttp://hdl.handle.net/2117/1029822017-03-28T15:04:11ZSantos Hernandez, SergioAmadei, Carlo AlbertoTang, Tzu-ChiehBarcons Xixons, VíctorChiesa, MatteoAn expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range
processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables.Wearing a single DNA molecule with an AFM tip
http://hdl.handle.net/2117/102976
Wearing a single DNA molecule with an AFM tip
Santos Hernandez, Sergio; Barcons Xixons, Víctor; Font Teixidó, Josep; Thomson, Neil H.
While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.
Tue, 28 Mar 2017 14:10:14 GMThttp://hdl.handle.net/2117/1029762017-03-28T14:10:14ZSantos Hernandez, SergioBarcons Xixons, VíctorFont Teixidó, JosepThomson, Neil H.While the fundamental limit on the resolution achieved in an atomic force microscope (AFM) is clearly related to the tip radius, the fact that the tip can creep and/or wear during an experiment is often ignored. This is mainly due to the difficulty in characterizing the tip, and in particular a lack of reliable methods that can achieve this in situ. Here, we provide an in situ method to characterize the tip radius and monitor tip creep and/or wear and biomolecular sample wear in ambient dynamic AFM. This is achieved by monitoring the dynamics of the cantilever and the critical free amplitude to observe a switch from the attractive to the repulsive regime. The method is exemplified on the mechanically heterogeneous sample of single DNA molecules bound to mica mineral surfaces. Simultaneous monitoring of apparent height and width of single DNA molecules while detecting variations in the tip radius R as small as one nanometer are demonstrated. The yield stress can be readily exceeded for sharp tips (R<10 nm) at typical operating amplitudes (A>10nm). The ability to know the AFM tip radius in situ and in real-time opens up the future for quantitative nanoscale materials properties determination at the highest possible spatial resolution.A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
http://hdl.handle.net/2117/101717
A discrete-time equivalent system approach to the periodic response of nonlinear autonomous circuits
Palà Schönwälder, Pere; Miró Sans, Joan Maria
The problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.
Tue, 28 Feb 2017 15:34:46 GMThttp://hdl.handle.net/2117/1017172017-02-28T15:34:46ZPalà Schönwälder, PereMiró Sans, Joan MariaThe problem of computing the steady state response of nonlinear autonomous circuits is solved making use of a discrete-time equivalent system approach. With the application of an s-plane to z-plane mapping, the circuit equations are discretized and written in vector form. Using this technique, it is not necessary to repeatedly compute transforms between the time and the frequency domain. An efficient scheme to build the Jacobian matrix with exact partial derivatives with respect to the oscillation period and with respect to the samples of the unknown variables is described. Application examples on two widely studied circuits are provided to validate the proposed technique.An explicit method for modeling lossy and dispersive transmission lines
http://hdl.handle.net/2117/100927
An explicit method for modeling lossy and dispersive transmission lines
Palà Schönwälder, Pere; Miró Sans, Joan Maria
In this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.
Mon, 13 Feb 2017 14:26:09 GMThttp://hdl.handle.net/2117/1009272017-02-13T14:26:09ZPalà Schönwälder, PereMiró Sans, Joan MariaIn this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Padé approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
http://hdl.handle.net/2117/98495
A discrete-time approach to the steady-state and stability analysis of distributed nonlinear autonomous circuits
Bonet Dalmau, Jordi; Palà Schönwälder, Pere
We present a direct method for the steady-state and stability
analysis of autonomous circuits with transmission lines and generic non-
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re-
spect to the samples of the unknowns is described. Without any modifica-
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.
Fri, 16 Dec 2016 16:30:04 GMThttp://hdl.handle.net/2117/984952016-12-16T16:30:04ZBonet Dalmau, JordiPalà Schönwälder, PereWe present a direct method for the steady-state and stability
analysis of autonomous circuits with transmission lines and generic non-
linear elements. With the discretization of the equations that describe the
circuit in the time domain, we obtain a nonlinear algebraic formulation
where the unknowns to determine are the samples of the variables directly
in the steady state, along with the oscillation period, the main unknown in
autonomous circuits.An efficient scheme to buildtheJacobian matrix with
exact partial derivatives with respect to the oscillation period and with re-
spect to the samples of the unknowns is described. Without any modifica-
tion in the analysis method, the stability of the solution can be computed a
posteriori constructing an implicit map, where the last sample is viewed as
a function of the previous samples. The application of this technique to the
time-delayed Chua's circuit (TDCC) allows us to investigate the stability of
the periodic solutions and to locate the period-doubling bifurcations.