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The design of a high performance envelope detector which does not need the traditional compensation between keeping and tracking required in these circuits is presented. Simulation results are offered comparing both the conventional and the proposed envelope detector and the superior performance of this circuit is shown. Tracking is 12.8 times faster and ripple is a third of that corresponding to the conventional counterpart for the same integration capacitance.
Introduction: High performance envelope detectors are required to obtain the amplitude of the signal in a great variety of circuits, mainly for automatic gain control circuits and spectral energy estimation over a variety of applications, such as hearing aids, cochlear implants, speech recognition front-ends [1] and especially in wireless communication receivers [2]. The conventional diode-RC peak detector is too simple and inefficient for these applications [3]. Op amp and diode based envelope detectors suffer high distortion during the zero crossing of the input signal as the op amps have to recover during nonconduction/conduction transition with a finite slew rate. The envelope detector is thus limited to a frequency performance well below the gain bandwidth product of the amplifier. An improvement can be the use of current-mode rectifiers which can operate at higher frequencies than the diodes [4, 5]. Other envelope detectors are based on root mean square (rms) type circuits [6]. However, these schemes suffer from the same limitation: the trade-off between the keeping and the tracking of the signal that requires the envelope signal filtering to minimise ripple at the cost of higher settling times. In this Letter a novel envelope detector is proposed that overcomes the traditional trade-off required in these circuits, improving both the tracking and keeping of the signal.
Proposed envelope detector: Fig. 1 shows the conceptual scheme of the proposed envelope detector. Instead of a peak detector, a peak hold is employed to...