Sharif Digital Repository

A single 1.5 V supply, second order band-pass gm-C filter based on a low-voltage transconductor architecture in standard 0.6 um CMOS process is presented. A dc level shifter circuit (DCLS) is utilized at the input of the proposed transconductor to increase the dc level of the input signal. This makes the input transistors operate in the desired region and hence input voltage swing enhances. DCLS uses a simple voltage doubler as its supply while other parts of the circuit use the main 1.5 V supply. Proposed transconductor shows a THD of -60 dB for 1.4 Vpp,diff input signal with 1 MHz frequency. Also a proper common-mode detector circuit is developed for this low-voltage application. The... 

The paper introduced a new design for two-frequency MTI radar is introduced. The suggested system can change its frequencies, in each pulse. Therefore, the system is very resistive to electronic war. The analytical results of our calculation show that the system has very high blind speed and in realistic situations, it increases signal to noise ratio, although it widens clutter bandwidth and detects some spurious targets  

A 1.5-V single supply, second order continuous-time bandpass filter, on a 0.6μm standard CMOS process is designed. The THD of the transconductor for a 0.7Vpp input, is -50dB at 10-MHz. In the proposed transconductor structure, the whole circuit, apart from a dc level-shifter based on a voltage doubler, is biased by a single 1.5-V supply. Due to this structure, a high current voltage doubler is not required and the whole filter draws less than 70μm current from this doubler making an on-chip voltage doubler feasible. Also, a new linear common-mode detector with high-frequency response is designed to stabilize the output common-mode voltage. © 2002 IEEE  

In this paper, we introduce a new bound for the peak of the continuous envelope of an OFDM signal based on the maximum of its corresponding oversampled sequence, that is considerably tighter than the recent results presented in [4]. The proposed bound is then used as the basis of our study in two parts. In the first part, we find an upper bound for the regrowth of the peak of the digitally clipped oversampled sequence after discrete to continuous conversion. We also show that for oversampling rates greater than π/√2, the peak regrowth percentage depends only on oversampling rate, regardless of the number of subcarriers. In the second part, we propose new and tight relative error bounds for... 

A novel cascode configuration previously presented as a high output resistance load (Fujimori and Sugimoto, 1998) has been investigated and utilized for amplification to achieve higher gain and bandwidth by the authors (Lofti and Atarodi, Proc. ICEE'00, vol.1, pp.83-8, 2000). A low-voltage single-stage opamp using this configuration is designed. Finally, based on this idea a 1.5-V offset- and gain-compensated 5th order switched-capacitor low pass filter with only 150 μA current consumption in a 0.8 μm process is designed. © 2000 IEEE  

An Erbium-doped silica CROW can be employed as a band pass and band stop amplifier in telecommunication systems. Also it can be proposed as wide band amplifier as well as narrow band amplifier. We investigate theoretically and simulate structure of Erbium-doped CROW (EDC) with different parameters to realize its performance and possible applications as an amplifier. In this paper we try to consider effect of different parameters on gain spectrum of systems. © 2009 SPIE  

A technique that expands dynamic range (DR) of frequency down-converters in the C band frequency is presented. Primary characteristics of down-converter are evaluated to confirm that it can be used in microwave receivers. The C band down-converter is carried out by the combination of RF mixers, band pass interdigital filter, and X band combline filter which are designed entirely for this project. Attainment of the perfect receiver is the final purpose of this paper, and a method that causes 72 dB dynamic range, high tangential signal sensitivity and fine gain flatness is used for achieving the mentioned purpose. These efforts improve the dynamic range about 19 dB and gain flatness about 3.07... 

A simple and efficient transmission line model is proposed here to study how the transmission characteristics of photonic crystal waveguides are tailored by introduction of stubs patterned in the photonic crystal lattice. It is shown that band-pass and band-stop optical filters can be easily designed and optimized when stubs of appropriate length are brought in. Since the lengths of the designed stubs are not necessarily integer multiples of the photonic crystal lattice constant, a geometric shift in a portion of the photonic crystal structure is shown to be essential. The proposed model is verified by using a rigorous numerical method. An excellent agreement is observed between the... 

The effect of clock skew and duty-cycle on the performance of high-Q N-phase band-pass filters (BPFs) have been examined in this paper. Following a mathematical approach and using the analytical derivations carried out, the effects of such non-idealities as clock skew and duty-cycle error are determined in an N-path filter. It is analytically proved that image signals from all integer multiples of the clock signal, rather than just those at (1 ± kN) multiples of the clock signal, land atop the wanted RF spectrum. In a real world clock generator, with non-idealities in effect, filtering property and proper behavior of the filter is adversely affected. Finally, system level simulation along... 

This paper introduces "switched-resistor" circuits as a new family of current-mode sampled-data circuits with improved accuracy and linearity. Advantages of the switched-resistor circuits for high-speed and low-voltage applications are demonstrated. A switched-resistor biquad band-pass filter with a quality factor of 10 and clock frequency of 100 MHz, fabricated in a 0.18 μ m CMOS process, is also presented. The filter consumes 9 mW from 1.8 V supply. © 2008 Elsevier GmbH. All rights reserved  

Thermal noise is one of the most important challenges in analogue integrated circuits design. This problem is more crucial in switched-capacitor (SC) filters due to the aliasing effect of wide-band thermal noise. In this article, a new simple method is proposed for estimating the power spectrum density of output thermal noise in SC filters, which have acceptable accuracy and short running time. In the proposed method, first using HSPICE simulator, accurate value of accumulated sampled noise on sampler capacitors in each clock state is achieved. Next, using difference equations of the SC filter, frequency response of the SC filter is shaped by time domain analysis. Based on the proposed... 

In this paper, an adaptive design methodology for synthesizing a harmonic free N-path filter with reduced frequency folding is presented. System level analysis of proposed architecture shows that by adding a few extra paths with proper weights to a conventional N-path filter, several characteristics such as harmonic rejection, power reduction, foldback elimination and spectrum shaping can be achieved. The designed filter is reconfigurable to be a band-pass filter (BPF) or a band-reject filter (notch), based on the requirements. By using the nth harmonic of Local Oscillator (LO) signal, instead of the fundamental harmonic, the required input clock frequency in N-phase clock generator is... 

The field enhancement in micro resonators causes the Raman amplification enhancement in them. Micro resonators can be connected to form sequence in variety of ways. The various structures such as single channel and double channel side coupled integrated space sequence of resonators (SClSSORs) can be used as Raman amplifier with different performances. In this paper, a silicon micro-ring coupled-resonator optical waveguide (CROW) is considered as a bandpass Raman amplifier. We introduce an iterative matrix method for analysis the CROW Raman amplifier. This method is applied to the single pump and single input for silicon CROW Raman amplifiers, and the effects of physical parameters of the...