Mohsen Jalali

Ultra-low power current mode all- MOS ASK demodulator for radio frequency identification applications

An ultra-low power amplitude shift keying (ASK) demodulator for radio frequency identification (RFID) tags is presented. On the basis of a fast averaging stage, the proposed ASK-demodulator uses a current domain switching envelope amplifier which yields low-power operation. More importantly, it removes the need for a conventional voltage comparator. Designed and fabricated in a 0.18 µm complementary metal–oxide–semiconductor process on about 3000 µm2 silicon area, the proposed demodulator consumes only 7.5 µA from a magnetically coupled induced power. Operating with a 13.56 MHz carrier frequency, the circuit supports modulation indices from 7 up to 100%. The demodulator may as well be used in passive biomedical devices where power efficiency is crucial.

Noise Equivalent Circuit Model of Thin Avalanche Photodiodes

In this letter, a circuit model of noise is presented for thin avalanche photodiodes. By defining an effective electric field over the multiplication region and using position-dependent ionization coefficients, the model tries to include the effects of carriers dead space and previous ionization history. Then, using a predicted multiplication gain, the model obtains the photocurrent response and output noise spectrum. The excess noise factor and spectral signal-to-noise ratio obtained from the proposed model are compared with available experimental data for different widths of multiplication region. The model is suitable for sensitivity and gain-bandwidth analysis.

Waveform efficiency analysis of auditory nerve fiber stimulation for cochlear implants

Evaluation of the electrical stimulation efficiency of various stimulating waveforms is an important issue for efficient neural stimulator design. Concerning the implantable micro devices design, it is also necessary to consider the feasibility of hardware implementation of the desired waveforms. In this paper, the charge, power and energy efficiency of four waveforms (i.e. square, rising ramp, triangular and rising ramp-decaying exponential) in various durations have been simulated and evaluated based on the computational model of the auditory nerve fibers. Moreover, for a fair comparison of their feasibility, a fully integrated current generator circuit has been developed so that the desired stimulating waveforms can be generated. The simulation results show that stimulation with the square waveforms is a proper choice in short and intermediate durations while the rising ramp-decaying exponential or triangular waveforms can be employed for long durations.

A methodology for designing class-F−1/J(J−1) high efficiency concurrent dual-band power amplifier

Abstract This paper, presents a methodology for designing concurrent dual-band power amplifier (DB-PA) that operates in Class-F−1 at one band and Class-J or Class-J−1 at the other band. It is shown that the second harmonic engineering of Class-F−1 and Class-J or Class-J−1 makes these classes of operation compatible in terms of dual-band realization without introducing higher complexity in realizing the harmonic control network. The design methodology is well illustrated and is validated by implementing a Class F−1/J concurrent dual-band PA operating at 1842 and 2655 MHz bands. Experimental results exhibit output powers of 40 and 41 dBm and efficiencies of 76% and 70% at the lower and upper bands, respectively. The AM-AM, AM-PM and two-tone third-order inter-modulation distortion results imply a good linearity behaviour of the designed PA. Furthermore, the linearity of the designed DB-PA is also verified with a single carrier WCDMA signal, where the PA shows better than −20 dBc adjacent channel power ratio in saturation region at both of the operating bands.