Design of a wood tissue impedance emulator in monolithic form

Wood tissue impedance is known to possess fractional-order characteristics which can be emulated using appropriately configured RC networks. However, this is not an optimum solution from the design flexibility point of view, due to the absence of on-line tunability of the characteristics of the emulated impedance. To overcome this difficulty, active emulators have been introduced, where the active elements are Operational Transconductance Amplifiers (OTAs). This offers electronically tunable structures capable of capturing the characteristics of the emulated tissue under different conditions. In addition, it is capable for implementation in monolithic form. In this work, an integrated emulator of the fractional-order wood tissue model for application in monitoring moisture gradients in wood products is presented. The operation of the proposed emulator is verified using the Cadence software and MOS transistor models provided by the AMS 0.35 μm CMOS process and confirmed to operate within the desired specifications.