Implementation Of Continuous Wavelet Transform By BiCMOS Log-domain Current Mode Circuit

The Wavelet Analysis is a kind of a self-adapted time-frequency localized method, which tune the time-frequency window automatically and has a strong flexibility. Its applications relate to a lot of fields, such as the communication signals processing, the radar images analysis. For adapting the real-time requirements of signal processing in project, the study of using hardware to realize wavelet transform are developed rapidly. At present, the VLSI implementations of Continuous Wavelet Transform can divide into in time-domain and in frequency-domain. In time-domain, the methods to realize the CWT have the advantages of fast speed, simple structure and integrate integratively. So it is suitable for the occasion of requiring of fast calculation. Otherwise, it is agiler to implement the CWT in frequency-domain than time-domain. There are more kinds of implementations in this way.One of prospective developing directions of VLSI implementation is low-voltage, low-power analog circuit. Instantaneous companding circuits offer the possibility of wide dynamic range and high frequency operation on a low power-supply voltage with low distortion. Log-domain filter is a typical instantaneous companding circuit. BiCMOS(Bipolar CMOS)is the technology that CMOS transistors and bipolar transistors are integrated on the same chip at the same time. BiCMOS log-domain systems can be advantageously implemented using the exponential characteristic of bipolar transistors to form translinear loop, and MOS transistors biased in weak inversion to realize the current mirrors and the voltage follower having high current gaining. For this reason, it is attractive to apply this technology in design of low-voltage, low-power integrated circuits.In this paper, a method of realizing continuous wavelet transform with BiCMOS log-domain circuit is proposed. Each required bandpass filter is reduced to two lowpass filters which are relatively simple in design by using complex demodulation. The decomposition and reconstruction architecture are introduced. The decomposition and reconstruction architecture are introduced. The design and implementation of element circuits including current-controling-oscilator (ICO), log-domain integrator and Gauss filter are also described in detail. Finally, the source of errors and the compensation methods are discussed. All of analysis, calculation results and simulations demonstrate that the methods presented in the paper are feasible, the algorithm is effective, the realization of circuit is simple, the procedures of the design are standard, and the system can be applied in low-voltage, low-power and at high speed.