Design Of Compensation Filter Research Articles

An adaptive filter–based temperature compensation technique for structural health monitoring

Temperature variations have significant effects on guide wave propagation and therefore increase the detection uncertainty of the guided wave–based structural health monitoring system. A novel temperature compensation technique combining an adaptive filter and optimal baseline selection is developed to enhance the robustness and effectiveness of guided wave–based damage detection. The adaptive filter is the finite length unit impulse response digital filter based on adaptive linear neuron network. This article focuses on three main issues for practically implementing the proposed method: (a) establishment of temperature compensation standard, (b) parameter design of compensation filter, and (c) determination of temperature gradient to reduce the number of selected baselines. Experiments are conducted on two stiffened composite plates to verify the proposed method for effective and robust temperature compensation under a large temperature range from −40°C to 80°C. Results show that temperature interval for baselines of low-frequency signals, such as 50 kHz, can be up to 20°C to provide good temperature compensation with the proposed method, while temperature interval for baselines of high-frequency signals, such as 450 kHz, can be up to 12°C.

Application of amplitude transformation for compensation of comb decimation filters

The design of compensation filters for comb decimators using amplitude transformation is introduced. It is shown that the transformation of cosine-squared filters provides good compensation characteristics. For a first-degree polynomial, the slope of the transformation line is explicitly set as the unique compensator's multiplierless coefficient. This coefficient changes proportionally with the increase of the comb passband droop. Thus, the proposed approach provides an intuitive and easy way of designing compensation filters.

A Self-Adaptive Frequency Response Compensation Method for a TIADC System

Time interleaving is one of the most efficient techniques employed in high-speed sampling systems. However, the frequency response mismatch among different channels will create distortion tones that degrade the system performance. In this paper, a self-adaptive frequency response mismatch compensation method is presented, where the design of compensation filter is optimized with a self-adapting strategy. This digital postprocessing technique realizes the compensation of frequency response effectively and also the increase of the digital bandwidth of the acquisition system. MATLAB-based simulation and an actual two-channel acquisition system test verify the effectiveness of the algorithm.

Polynomial based Design of CIC Compensation Filter used in Software Defined Radio for Multirate Signal Processing

oftware defined radio has find important place in modern communication systems where majority of signal processing is performed in the digital domain using programmable DSPs.Digital down conversion (DDC) is one of the core technologies in SDR, as well as an important component of digital intermediate frequency receiver system. DDC use CIC decimation filters for sample rate decimation. CIC decimation filters require less computation but large passband droop occurs in the frequency response. This paper presents a simple design of compensation FIR filter for CIC decimation filter which will correct the passband droop. Compensation filter design consists of polynomial based design of FIR filter which are used in cascade with CIC filter. As proposed filter depends on simple transformation less approach and computation is required. The resulting structure is multiplier less and exhibits small passband droop in comparison to CIC filter. It modifies the frequency response of CIC decimation filter while maintaining the linear phase.

Stabilization of feedback-type active control systems in finite ducts.

Use of feedback-type control architectures in active noise cancellation can be very difficult due to the extreme sensitivity of this approach to instability, but are sometimes advantageous because the need for the reference sensor is eliminated. Instability results when the feedback loop time delay causes an additional phase shift of 180° at some frequencies allowing high-gain positive feedback to occur. The classical approach to this problem is to design a compensation filter which reduces the feedback gain to less than unity at the frequency(s) where the loop delay causes instability. In a finite-length duct, the feedback instabilities are found to be related to the transducers and the distance between them as well as their positions within the duct. The potential for instability is present whether adaptive or fixed active noise control is done using a feedback-type controller. The compensation filter design is determined directly from the physical parameters of the finite waveguide and the transducers. However, the performance of the feedback controller is restricted by the compensation filter.

Compensation filter design using megavoltage radiography

The exit dose information that is available on a port film taken on a therapy treatment unit is used to determine the compensation required to produce a uniform dose distribution. The procedure is automated using a computer-controlled scanning densitometer; this saves considerable personnel time compared with conventional methods. The system also can copensate for body inhomogeneties.