High-performance RC bandpass filter is adapted to miniaturized construction

Miniaturized bandpass filter with RC networks is suitable for use in integrated circuits. The circuit consists of three stages of amplification with additional resistive and capacitive components to obtain the desired characteristics. The advantages of the active RC filter network are the reduction in size and weight and elimination of magnetic materials

Smanjenje šuma i osjetljivosti uporabom SC filtara

The discrete time switched capacitor (SC) based filters have number of advantages over the classical continuous time active RC based filters, the one most important being reduced circuit silicon area, allowing SC filters to be integrated to a single monolithic integrated circuit (IC). In this paper we have designed fifth order Chebyshev low pass SC filter, with a cut-off frequency f_x=3.4 kHz, and pass-band ripple a_ma x =-0.5 dB, and we have compared its time and frequency performance with a performance of the active RC based filter. The both SC and active RC filters are realized as a cascade of two second order sections and one first order section. All filter analysis has been performed using MATLAB and SPICE program packages where SC based filter has shown significant noise and sensitivity improvement, when compared with active RC based filter.Vremensko diskretni filtri s preklapanim kapacitetima imaju niz prednosti nad klasičnim vremensko kontinuiranim aktivnim RC filtrima. Jedna od važnijih prednosti jest smanjena površina silicija, omogućavajući integraciju filtra u integriranoj thenologiji (IC). U ovom radu dizajniran je Chebyshev nisko propusni filtar s preklapanim kapacitetima s graničnom frekvencijom f_c = 3.4 kHz i valovitosti alpha_max = -0.5 dB, te su mu vremenska i frekvencijska svojstva uspoređena sa svojstvima aktivnog RC filtra. Oba filtra realizirana su kao kaskada dviju sekcija drugog reda te jedne sekcije prvog reda. Analiza oba filtra izvršena je u MATLAB i SPICE programskim paketima, te je kod SC filtra pokazano znatno smanjenje šuma i osjetljivosti u usporedbi s aktivnim RC filtrom

Active rc filter permits easy trade-off of amplifier gain and sensitivity to gain

Passive RC network was designed with zeros of transmission in the right half of the complex frequency plane in the feedback loop of a simple negative-gain amplifier. The proper positioning provides any desired trade-off between amplifier gain and sensitivity to amplifier gain

2.5 V 35 dBm IIP3 75 MHz sixth-order active RC filter

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Current-Controlled Current-Mode Universal Biquad Employing Multi-Output Transconductors

This paper deals with RC active biquad working in the so-called current mode (CM). The design approach uses only three transconductors (OTA) with the minimum necessary number of outputs and with only three passive grounded elements. The proposed filter has simple circuit configuration providing all standard transfer functions such as high-pass (HP), band-pass (BP), low-pass (LP), band-reject (BR) and all-pass (AP). Electronic tuning and independent adjusting of the quality factor and bandwidth of BP filter is possible. The presented circuits are verified by PSpice simulations utilizing OTAs on transistor level of abstraction. The linear parasitic effects of the real active elements in each suggested circuit are briefly discussed. Experimental verification is also given. Designed networks can be used in many applications such as antialiasing filters, in high-speed data telecommunication systems, for signal processing in the cable modems, in regulation and measurement techniques etc

Synthesis of New Biquad Filters Using Two CFOAs

This paper deals with synthesis based on new autonomous circuit using two current feedback operational amplifiers. Four possible second-order structures are derived and several active RC filters are described. One new circuit of the band-pass filter is introduced in detail. Its parameters are studied symbolically, tested by simulations and confirmed by measurements

System-level optimization of baseband filters for communication applications

In this paper, a design approach for the high-level synthesis of programmable continuous-time baseband filters able to achieve optimum trade-off among dynamic range, distortion behavior, mismatch tolerance and power area consumptions is presented. The proposed approach relies on building programming circuit elements as arrays of switchable unit cells and defines the synthesis as a constrained optimization problem with both continuous and discrete variables, this last representing the number of enabled cells of the arrays at each configuration. The cost function under optimization is, then, defined as a weighted combination of performance indices which are estimated from macromodels of the circuit elements. The methodology has been implemented in MATLAB™ and C++, and covers all the classical approximation techniques for filters, most common circuit topologies (namely, ladder simulation and cascaded biquad realizations) and both transconductance-C (Gm-C) and active-RC implementation approaches. The proposed synthesis strategy is illustrated with a programmable equal-ripple ladder Gm-C filter for a multi-band power-line communication modem.P.R.O.F.I.T. FIT-070000-2001-84

Análise e simulações de um filtro banda adaptativo aplicado a um filtro activo série

Neste artigo apresenta-se o trabalho de projecto, simulação, análise e ajuste de parâmetros de um Filtro Banda Adaptativo (FBA), utilizado para, a partir das correntes medidas, gerar um sinal de referência que consiste na componente positiva à frequência fundamental das correntes do sistema trifásico. A necessidade deste sinal de referência deve-se à abordagem seguida no controlo de um Filtro Activo Série. Foram efectuadas várias simulações visando estudar o comportamento do FBA com cargas que originam elevados índices de distorção harmónica e desequilíbrio, nomeadamente rectificadores trifásicos e monofásicos com cargas do tipo RC e RL, sendo consideradas as impedâncias das linhas. As simulações foram efectuadas para diversos valores de ganho do filtro de forma a se observar as tendências de variação das saídas do mesmo.The objective of this paper is to explain the steps taken in the project, simulation, analysis and adjustment of the parameters of an Adaptive Band-Pass Filter used to generate a reference signal, consisting of the direct positive sequence of the fundamental currents of a three-phase system. This signal is required to the control approach of a Series Active Power Filter. Various simulations were performed in order to study the behavioural tendency of the Adaptive Filter. In order to obtain highly distorted current wave-shapes, three phase and single phase rectifiers with RC loads were used. To obtain unbalanced currents different types of loads were used in the single phase rectifiers. For both cases the line impedances were considered. Several simulations were run for different values of the Adaptive Filter gain in order to observe the variation of the Filter outputs.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ESE/41170/2001

Digital current sensing in modular multilevel converter for HVDC applications

For long-distance transmission, HVDC (High-Voltage, Direct-Current) is proven to be less expensive and have lower electrical losses as compared to HVAC (High-Voltage, Alternating-Current). Now a days, the advancement of power electronic switches such as IGBT's and MOSFET enables the use of converters for HVDC applications. Among the well-known converters used for HVDC are Voltage Source Converter (VSC) Line Commutated Converter (LCC) and Modular Multilevel Converter (MMC). The MMC is still new and a promising technology for HVDC application. The MMC has many advantages such as controlling high amount of active/reactive power and possess lower losses as compared to other converters. To control the active/reactive power in a MMC, control scheme such as free-running hysteresis uses the reference voltage and the inductor current to produce the required switching pulses. This study proposed a technique in which a voltage sensor is use to measure the inductor current. Conventionally, the inductor current is sensed either with a resistor or Current Transformer (CT). This method is associated with some disadvantages; requires additional circuitry which introduces some power loss and requires higher bandwidth in order to sense accurately. This study instead, measures the current indirectly by using the information of the phase inductor voltage. As the voltage sensor is placed in parallel to the inductor, this measuring technique is immune to I2R loss. The proposed technique will be investigated using MATLAB simulation to determine its current sensing capability in a MMC for HVDC applications. To design an improved current-less sensing method using a digital RC network. To extract the inductor current values from the phase inductor voltage an RC filter is required and placed in parallel across the inductor. In this way, all the high frequency harmonics will be filtered out and only the low frequency inductor current can be seen across the capacitor. The selection of RC values, however is dependent on the inductor value and inductor DC-Resistance (RDCR). The main concern with this technique is that selection of DCR RC values sometimes can be unavailable for hardware implementation. To further improve the implementation of RC network and eliminate the problems of selecting suitable RC values for hardware implementation. This paper proposed the used of digital filter based on the RC network concept. Instead of using the actual components for filtering the high frequency harmonics, this technique uses only the DSP for filtering to remove the high frequency harmonics. The proposed technique is able to convert the high frequency voltage VL1 measured from the phase inductor L1 into the phase inductor current iL1without any delay or difficulty. By 1 L1 comparing the signals of proposed method to the series sensing method and the conventional RC filter method the waveforms of both signals are almost identical. However, the proposed method eliminates the need for RC components as compared to the conventional RC filter method. This technique improves the efficiency of the system in terms of improve signal noise ratio and eliminates the need for passive component on the system