Intermodulation Technique Research Articles

Neural Dielet: A 0.4mm 3 Battery-Less Crystal-Less Neural-Recording System on Die Achieving 1.6cm Backscatter Range with 2mm×2mm On-Chip Antenna.

Miniaturization is essential in the design of wireless neural-recording systems. In recent years, the battery in neural-recording systems can be eliminated by wireless power transfer (WPT), while antenna and crystal become two main bottlenecks to minimize a battery-less neural implant. In conventional battery-less designs, the miniaturization of antenna led to a short communication range, and a crystal-less clock suffered from noise issue or power-hungry circuits. In this work, we demonstrate a 0.4mm 3 neural dielet, which is a battery-less crystal-less neural-recording system on die (SoD) within a 2mm×2mm on-chip coil antenna. The communication range through the ultra-small antenna is extended by a proposed dither-based 3 rd-order intermodulation (IM3) technique, which prevents the backscatter communication from WPT blocker. Meanwhile, a dither-based 2 nd-order intermodulation (IM2) wireless-lock technique is proposed to remove the crystal. Measured results show that the SoD consumes 53.2 μ W power and achieves a wireless communication range of 1.6cm at a bit-error rate (BER) of 8 ×10-6, accompanied by simultaneous WPT for battery-less operation. In the animal experiment, the neural signal wirelessly recorded by our SoD in a battery-less way matches favorably with the wire-test results obtained by a commercial chip.

Characterization of the Passive Film Formed on Iron in Phosphoric Acid Solution: On the Use of a Double Modulation Technique

The interpretation of the response of an electrochemical system is usually based on the assumption that the current flowing through the electrode is the sum of two independent processes: the faradic current corresponding to the electrochemical processes and the capacitive current corresponding to the response of the interfacial capacitance. However, the separation of faradaic and capacitive currents is questionable in many different cases such as experiments performed in low-concentrated supporting electrolyte or the specific adsorption of diluted reactants. It was also shown that a charge injection to an ideal polarizable electrode results in two relaxations of the double layer corresponding to the charge neutralization on the electrode in the higher frequency domain and the charge rearrangement in the diffuse layer in a lower frequency range[1-3]. Passive layer and thin oxide films formed at a metal surface usually provide a natural protection of the metal resulting in an additional capacitive response in series with the electrical double layer. In the case of the contribution of such superficial phase, 2D- or 3D-film growth, the dielectric-like response of the interface can no longer be neglected. When these phases are kinetically involved in charge transfers, the decoupling can become particularly arbitrary. The modulation of the interfacial capacitance transfer function (MICTF) which was devised by Antaño-Lopez et al. for studying the influence of the ac and dc current on the interface capacitance [4] provides a unique way to overcome this difficulty. The MICTF provides the capacitive response of the interface at a frequency Ω when it is simultaneously scanned at a second frequency ω with the impedance spectrum. That is performed by a proper signal processing of the system response to a two- frequency, ω and Ω, composite measuring signal. It was used to study the double layer relaxation and specific adsorption of halide ions on mercury electrode [5] or to gather information on electron dynamics in TiO2 dye-sensitized solar-cells [6]. In this work, we report on the response of the oxide film formed on iron in phosphoric acid solution using this double modulation technique. A specific attention will be paid on the capacitive response of the electrode as a function of the potential so as to be able to provide a detailed analysis of both the EIS and the capacity responses with the MICTF technique compared with other data interpretation such as the Mott-Schottky theory. [1] F.C. Anson, R.F. Martin, C. Yarnitzky, Creation of nonequilibrium diffuse double layers and studies of their relaxation, J. Phys. Chem., 73 (1969) 1835-1842. [2] C. Yarnitzky, F.C. Anson, Mechanism of charging and discharging ionic double layers at electrodes, J. Phys. Chem., 74 (1970) 3123-3130. [3] S.W. Feldberg, Theory of relaxation of the diffuse double layer following coulostatic charge injection, J. Phys. Chem., 74 (1970) 87-90. [4] R. Antaño-Lopez, M. Keddam, H. Takenouti, A new experimental approach to the time-constants of electrochemical impedance: frequency response of the double layer capacitance, Electrochim. Acta, 46 (2001) 3611-3617. [5] E.R. Larios-Duran, R. Antaño-Lopez, M. Keddam, Y. Meas, H. Takenouti, V. Vivier, Dynamics of double-layer by AC Modulation of the Interfacial Capacitance and Associated Transfer Functions, Electrochim. Acta, 55 (2010) 6292-6298. [6] H. Cachet, M. Keddam, H. Takenouti, R. Antaño-Lopez, T. Stergiopoulos, P. Falaras, Capacitance probe of the electron displacement in a dye sensitized solar cell by an intermodulation technique: a quantitative model, Electrochim. Acta, 49 (2004) 2541-2549.

Reconstruction of tip-surface interactions with multimodal intermodulation atomic force microscopy

We propose a theoretical framework for reconstructing tip-surface interactions using the intermodulation technique when more than one eigenmode is required to describe the cantilever motion. Two particular cases of bimodal motion are studied numerically: one bending and one torsional mode, and two bending modes. We demonstrate the possibility of accurate reconstruction of a two-dimensional conservative force field for the former case, while dissipative forces are studied for the latter.

Rate coefficients measurement for the energy-pooling collisions Cs(5D) + Cs(5D) → Cs(6S) + Cs(nl = 9D, 11S, 7F)

We report experimental rate coefficients for the energy-pooling collisions Cs(5D)+Cs(5D)→Cs(6S)+Cs(nl=9D,11S,7F). In the experiment the Cs(5D) state was populated via photodissociation of Cs2 molecules using an argon-ion laser at wavelength 488.0nm. We also consider the competing process 6P1/2+7S→6S+(nl=9D,11S,7F) that might also populate 9D, 11S and 7F. An intermodulation technique was used to select the fluorescence contributions due only to the process 6P1/2+7S→6S+(nl=9D,11S,7F). The excited atom (nlJ) density and spatial distribution were mapped by monitoring the absorption of a counterpropagating probe laser beam tuned to various nlJ→n′lJ′′ transitions. The measured excited atom densities are combined with measured fluorescence ratios to yield rate coefficients for the energy-pooling collisions Cs(5D)+Cs(5D)→Cs(6S)+Cs(nl=9D,11S,7F). The rate coefficients for nl=9D, 11S, 7F are (4.1±2.0)×10−10cm3s−1, (1.6±0.8)×10−10cm3s−1 and (3.6±1.8)×10−10cm3s−1, respectively. The contributions to the rate coefficients from other energy transfer processes are also discussed.

Capacitance probe of the electron displacement in a dye sensitised solar cell by an intermodulation technique: a quantitative model

A new transfer function based on capacitance measurements via an intermodulation technique is introduced for characterizing dye-sensitized solar cells (DSSC). A two-frequency composite signal is applied for measuring the frequency dependence of the first derivative with respect to the potential of a capacitance relevant to the electrochemical system under test. In the case of DSSC, the probed capacitance corresponds to that of the SnO2–TiO2 rear contact. Using a general formalism initially developped for any electrochemical interface, explicit expressions of the transfer function have been derived for DSSC and quantitatively compared to experiments. Information on electron dynamics is similar to that provided by IMPS, but in addition the new transfer function allows the TiO2 nanostructure contact surface area to be readily determined.

Instantaneous Corrosion Rate Measurement with Small-Amplitude Potential Intermodulation Techniques

Abstract With the intermodulation technique, a potential distortion using two sine waves is applied to a corrosion system. The alternating current (AC) response consists of amplitudes measured at different frequencies. Simple relations are derived from the current-vs-potential relation for a corroding process under activation control, from which the corrosion rate and Tafel parameters can be calculated. These are valid when the amplitude of the applied potential distortion is sufficiently small. With the intermodulation technique, the corrosion rate and Tafel parameters can be obtained within one measurement, which makes this technique an ideal candidate for application as a corrosion monitoring tool. Results obtained with this technique were shown to be in agreement with other electrochemical methods for corrosion rate measurement, such as Tafel extrapolation, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS).

Simple electronic device for intermodulation techniques. Application to high-resolution laser spectroscopy in molecular beams

A simple experimental set-up useful for intermodulation techniques is described. Its experimental details and conditions as well as its application to high-resolution laser induced fluorescence in sodium beams are reported. The major advantages of the present technique include its simplicity (low cost) and enhanced signal-to-noise ratio resulting in significantly improved frequency resolution when using a non-stabilized laser system.

Heteronuclear energy pooling collisions: The Na(3P) + K(4P) reaction

An experiment has been performed in which two different atomic species - sodium and potassium - have been simultaneously excited in a cell by two resonant cw dye lasers and the fluorescence spectrum has been analysed by using an intermodulation technique to isolate the contributions due to the heteronuclear processes. The energy pooling collisions between Na(3P) and K(4P) have been observed for the first time and the relative collision cross sections have been measured.

Laser spectroscopy using beam-overlap modulation

A new Doppler-free laser spectroscopy method is demonstrated that employs modulation of the position of a laser beam rather than the commonly used intensity or polarization modulation. The technique is applicable in saturated absorption as well as fluorescence measurements, as is illustrated in experiments on sodium and iodine lines. A particular feature of the method is that Doppler- and background-free fluorescence spectra can be recorded without using intermodulation techniques.

Nonlinear interaction of an rf field with a bulk superconductor

Using a very sensitive intermodulation technique, we have measured the temperature ( T) and magnetic fielf ( H) dependence of the nonlinear rf interaction with pure bulk indium. A signal which varies extremely rapidly with both T and H is seen near T c.

Sub-Doppler optoacoustic spectroscopy

We report the observation of saturation Lamb-dips in the optoacoustic spectrum of CH 3OH and CO 2 excited by CO 2 laser. An intermodulation technique is used to get Doppler-free resolution of the lines. Because of the small sample size and the high sensitivity intermodulated optoacoustic spectroscopy compares favorably with other Doppler-free methods.

Determination of frequency-dependent magnetic recording losses

A technique to determine the frequency dependent record losses for contact as well as non-contact interfaces has been devised. Measurement of these losses in contact recording is normally accomplished by the use of two different interface speeds in order to factor out wavelength dependent effects; however, this method is undesirable in non-contact disc recording where flying height variations as a function of interface speed are normally encountered. To overcome this problem, the recording process is linearized by a.c. bias and intermodulation products between different frequencies are observed. The loss can be established from the amount by which the record current is increased as a function of frequency in order to maintain a constant level intermodulation product. Both two and three tone intermodulation techniques were investigated and the latter was found superior. Measurements obtained on a flying head/disc interface show, as expected, that the frequency dependent losses are essentially independent of radius and record level.

Variable-frequency automatic capacitance/conductance system for impurity profile and deep level determination

Development of new semiconductor technologies frequently requires impurity density analysis on material with high leakage currents or deep level contamination. Previously described impurity profilers provide minimal diagnostics for such cases. We have constructed a new variable-frequency capacitance/conductance analysis system applicable to impurity profile, Schottky barrier height, MOS interface state, and deep level analysis. The system, which consists almost entirely of commercial ’’building blocks,’’ uses phase-sensitive detection to provide better than 40-dB isolation between capacitance and conductance signals. For impurity profile measurements a two-frequency intermodulation technique avoids the stringent filtering requirements inherent in the Copeland plotter. In this mode the system can measure either capacitance, C, and dC/dV or conductance, G, and dG/dV over two decades in frequency. A small-scale analog computer integral with the unit allows presentation of the data as impurity profiles. A simple change of circuit parameters permits measurements of C or G with amplitude response flat within 1% over four decades of frequency. The computer may then be used to present the results in formats appropriate to Schottky barrier height or deep level determinations.

A polarographic study of mesityl oxide and its determination in diacetone alcohol by fast-scan, phase-sensitive, a.c. polarography

Fast-scan, phase-sensitive a.c. polarography has been shown to be an ideal method for the analysis of mesityl oxide in diacetone alcohol. It has a linear range of 10 −6 M -10 −3 M . Further extension of this range is possible with certain modifications such as using the fundamental harmonic, 2nd harmonic or intermodulation techniques and the optimisation of certain parameters mentioned in the text. The mechanism of the electrode reaction has been investigated and found to be reversible, pH dependent and complicated by the adsorption of the products of electrochemical reduction at the dropping mercury electrode.

A polarographic study of mesityl oxide and its determination in diacetone alcohol by fast-scan, phase-sensitive, A.C. polatography

Fast-scan, phase-sensitive a.c. polarography has been shown to be an ideal method for the analysis of mesityl oxide in diacetone alcohol. It has a linear range of 10−6 M-10−3 M. Further extension of this range is possible with certain modifications such as using the fundamental harmonic, 2nd harmonic or intermodulation techniques and the optimisation of certain parameters mentioned in the text. The mechanism of the electrode reaction has been investigated and found to be reversible, pH dependent and complicated by the adsorption of the products of electrochemical reduction at the dropping mercury electrode.