An accurate, non-invasive ex situ diagnostic technique for analyzing plasma generated harmonics in radio frequency (RF) discharges is presented utilizing a broadband Dual Directional Coupler (DDC) that measures accurately both forward and reflected voltage signals in a transmission line. For usual applications such as monitoring forward and reflected power, the DDC is placed between the RF generator and the matching network (MN). However, the MN reflects all plasma generated harmonics back toward the plasma. Hence, no harmonics reach the generator side of the MN. Thus, for monitoring the harmonics, it is necessary to place the DDC between the impedance matching unit and the plasma, which was used for the first time in an asymmetric, parallel plate RF discharge at 13.56 MHz, 10 W–50 W at 200 mTorr (argon). The analysis of DDC data yields voltage, harmonic power contents, complex load impedance, plasma reflection coefficient, Voltage Standing Wave Ratio (VSWR), etc., for the fundamental frequency. For instance, at 10 W net input power, the computed plasma impedance is ZL = Rp + jXp, with Rp = 16.8 Ω and Xp = −81.9 Ω, yielding VSWR ≈11. Additionally, for 50 W input power, the third harmonic (72.31 mW) is dominant, followed by the second (8.28 mW) and fourth harmonics. In contrast, the literature states that the second harmonic is usually dominant, possibly due to the invasive nature of the diagnostics. Because harmonics are an important signature of processes taking place within the plasma, the proposed diagnostic can be effectively used for calibration and verification of theoretical models/simulations for resolving relevant physics issues.

This work attempts to correlate the plasma density and RF harmonic profiles with respect to the pressure (at 13.56, 27.12 and 40.68 MHz) with the stochastic and ohmic power absorption mechanisms in a Capacitively Coupled Discharge (CCD), over a wide pressure range (0.6–1000 mTorr). Diagnostics include calibrated capacitive probe, compensated Langmuir Probe (LP) and uncompensated floating LP for measuring plasma parameters and RF signals. Pressure profiles of stochastic and ohmic powers, P Stoch and P Ohm (at 13.56 MHz) are obtained from their ratio (ξ) and the power absorbed by the electrons. Normalized profiles of an effective power (∼ P Stoch ρ × P Ohm 1 − ρ ; ρ : pressure dependent parameter) are tuned to reproduce closely the normalized plasma density profiles from which relative contributions of stochastic/ohmic mechanisms are determined. It is shown that up to ≈30 mTorr, plasma production is stochastic while beyond that both methods contribute jointly. The RF harmonic profiles can be analysed similarly. Higher harmonics produced by the intrinsic nonlinearity of the stochastic process should appear most clearly in the plasma at low pressures where the latter operates alone. On the other hand, the fundamental RF voltage that is always present in the plasma, can also produce higher harmonics at the probe tip by driving the nonlinear probe sheath. Thus, the harmonics produced directly by the stochastic nonlinearity are inextricably mixed up with those arising due to the probe sheath. Significantly, one may conclude therefore that it is not possible to investigate the stochastic mechanism of power absorption by a study of its harmonics when the latter are measured using invasive probes.

In the digital era of communication it is very common to sending some information from one point to another. In every field of engineering that is biomedical, astronomical, geological etc. Image is one of the commonly used multimedia. So for fast and efficient communication formulate, image compression is needed in each and every field. Intended for coding of transformed image, here is a comparison between various parameters of three of coding schemes EZW, SPIHT and EBCOT. After the transformation, those coding scheme basically code high energy components first and progressively transmits the coded bits to make an increasingly update and refined copy of the original image. In this paper reduced the execution time and provide the best reconstructed image with higher PSNR by using those coding schemes. The compared results of various parameters of image compression algorithms analyzed using MATLAB software and wavelet toolbox.EBCOT coder coverts the each bit plane into coded form into the three passes: i) significant propagation pass ii) magnitude refinement pass and iii) cleanup pass.

This paper reports an indigenously developed probe for the measurement of spatial profiles of the absorbed/generated RF power density Pabs (W/m3) in RF discharges. The technique utilizes a calibrated current (J) probe based on the Rogowski coil principle and an electric field (E) probe based on capacitive coupling, both integrated into a single probe called the J.E probe. Various aspects of the probe, such as its design, fabrication, calibration, and limitations, were resolved before it was used for obtaining axial profiles of RF power absorption/generation. Also presented are the first experimental results for the absorbed power density profiles at the fundamental (13.56 MHz) and harmonic (27.12 MHz) along the length of a capacitively coupled discharge. The axial scans between the powered and grounded electrode were taken at different argon gas pressures (10–800 mTorr) at a fixed RF power of 10 W. Detailed analysis of the results shows that even for systems with large electrode gaps, i.e., plasmas with long bulk plasma regions, practically all the fundamental power is absorbed in a narrow edge region near the powered electrode, irrespective of the pressure. Absorption is high near the RF electrode since the RF fields peak in this region. Another important conclusion is that stochastic absorption of the fundamental and harmonic generation proceeds fairly efficiently in the vicinity of the powered electrode even at high pressures. It may be mentioned that the probe technique introduced here is the first of its kind, and although there is considerable scope for miniaturization, it has, nonetheless, provided some key insights into the nature of RF power absorption in capacitive discharges.

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