A general scheme for the VLSI implementation of high-frequency continuous wavelet transform is developed using instantaneous companding technique to get an elegant solution to the problem of maintaining dynamic range and high frequency operation under low power supply voltages. An analogue BiCMOS high-frequency continuous wavelet transform circuit presented in this paper performs a time-frequency decomposition of a high-frequency input signal. The design and implementation of element circuits including voltage-controlled oscillator (VCO), phase-locked loop (PLL) using static and dynamic translinear circuits are also described in detail.

A new method for fault diagnosis of large-scale analogue circuits based on the class concept is developed in this paper. A large analogue circuit is decomposed into blocks/sub-circuits and the nodes between the blocks are classified into three classes. Only those sub-circuits related to the faulty class need to be, treated. Node classification reduces the scope of search for faults, thus reduced after-test time.' The proposed method is more suitable for real-time testing and can deal with both hard and soft faults. Tolerance effects are taken into account in the method. The class-based fault diagnosis principle and neural network based method are described in some details. Two non-trivial circuit examples are presented, showing that the proposed method is feasible.

A systematic method for fault diagnosis of analogue circuits based on the combination of neural networks and wavelet transforms is presented. Using wavelet decomposition as a tool for removing noise from the sampled signals, optimal feature information is extracted by wavelet noise removal, multi-resolution decomposition, PCA (principal component analysis) and data normalisation. The features are applied to the proposed wavelet neural network and the fault patterns are classified. Diagnosis principles and procedures are described. The reliability of the method and comparison with other methods are shown by two active filter examples.

The paper deals with fault isolation in nonlinear analogue circuits with tolerance under an insufficient number of independent voltage measurements. The L1-norm optimisation problem for different scenarios of nonlinear fault diagnosis is formulated with a new fast method being presented. How to solve the L1-norm optimisation problem is discussed and a new neural network-based approach for solving the nonlinear constrained L1-norm optimisation problem is proposed and utilised in locating the most likely faulty elements in nonlinear circuits. The validity of the proposed method is verified and simulation examples are presented.

A fully differential R-MOSFET-C fourth-order Bessel active low-pass filter employing passive resistors and current-steering MOS transistors as a variable resistor is proposed. The implementation relies on the tunability of the current-steering MOS transistors operating in the triode region which counteract the deviation of resistors in integrated circuit manufacturing technology in order that the group delay of the Bessel active filter can be realized accurately. A 0.75 us group delay 520kHz frequency fourth-order Bessel lowpass filter based on a passive doubly terminated RLC prototype was designed and fabricated using 3.3V power supply and 0.35um CMOS technology. Chip test results demonstrate better than -65dB THD with @ 100kHz, 1.65-Vpp signal, frequency tuning range of more than ten decades from 0.6kHz to 550kHz, chip area of 0.32mm2 and power consumption of 13.3mW.