A 0.18μm CMOS low-noise elliptic low-pass continuous-time filter

This paper presents a seventh order low-pass continuous-time elliptic filter for use in a high-performance wireline communication receiver. As an additional attribute, the filter provides programmable boost in the pass-band to counteract high frequency components attenuation. The filter shows a nominal cutoff frequency of fc=34 MHz , less than 1dB ripple in the pass-band, and a maximum stop-band rejection of 65dB. The filter also exhibits low noise feature (peak root spectral noise density below 56nV√Hz) and high linearity (more than 64dB of MTPR for a DMT signal of 0.5Vpp amplitude). It has been designed in a 0.18μm CMOS technology and it is compliant with industrial operation conditions (-40 to 85° C temperature variation and ± 5% power supply deviation). Simulations show a typical power consumption of 450 mW @ 1.8V supply.Ministerio de Ciencia y Tecnología TIC2003-0235

Matrix Methods for the Dynamic Range Optimization of Continuous-TimeGm-CFilters

This paper presents a synthesis procedure for the optimization of the dynamic range of continuous-time fully differential G m - C filters. Such procedure builds up on a general extended state-space system representation which provides simple matrix algebra mechanisms to evaluate the noise and distortion performances of filters, as well as, the effect of amplitude and impedance scaling operations. Using these methods, an analytical technique for the dynamic range optimization of weakly nonlinear G m - C filters under power dissipation constraints is presented. The procedure is first explained for general filter structures and then illustrated with a simple biquadratic section

A 0.18 μm CMOS low noise, highly linear continuous-time seventh-order elliptic low-pass filter

This paper presents a fast procedure for the system-level evaluation of noise and distortion in continuous-time integrated filters. The presented approach is based on Volterra's series theory and matrix algebra manipulation. This procedure has been integrated in a constrained optimization routine to improve the dynamic range of the filter while keeping the area and power consumption at a minimum. The proposed approach is demonstrated with the design, from system- to physical-level, of a seventh-order low-pass continuous-time elliptic filter for a high-performance broadband power-line communication receiver. The filter shows a nominal cut-off frequency of fc = 34MHz, less than 1dB ripple in the pass-band, and a maximum stop-band rejection of 65dB. Additionally, the filter features 12dB programmable boost in the pass-band to counteract high frequency components attenuation. Taking into account its wideband transfer characteristic, the filter has been implemented using G m-C techniques. The basic building block of its structure, the transconductor, uses a source degeneration topology with local feedback for linearity improving and shows a worst-case intermodulation distortion of -70 dB for two tones close to the passband edge, separated by 1MHz, with 70mV of amplitude. The filter combines very low noise (peak root spectral noise density below 56nV/√Hz) and high linearity (more than 64dB of MTPR for a DMT signal of 0.5Vpp amplitude) properties. The filter has been designed in a 0.18μm CMOS technology and it is compliant with industrial operation conditions (-40 to 85°C temperature variation and ±5% power supply deviation). The filter occupies 13mm2 and exhibits a typical power consumption of 450 mW from a 1.8V voltage supply.Ministerio de Ciencia y Tecnología TIC2003-0235

Single-input Multiple-output Tunable Log-domain Current-mode Universal Filter

This paper describes the design of a current-mode single-input multiple-output (SIMO) universal filter based on the log-domain filtering concept. The circuit is a direct realization of a first-order differential equation for obtaining the lossy integrator circuit. Lossless integrators are realized by log-domain lossy integrators. The proposed filter comprises only two grounded capacitors and twenty-four transistors. This filter suits to operate in very high frequency (VHF) applications. The pole-frequency of the proposed filter can be controlled over five decade frequency range through bias currents. The pole-Q can be independently controlled with the pole-frequency. Non-ideal effects on the filter are studied in detail. A validated BJT model is used in the simulations operated by a single power supply, as low as 2.5 V. The simulation results using PSpice are included to confirm the good performances and are in agreement with the theory

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

A wide dynamic range high-q high-frequency bandpass filter with an automatic quality factor tuning scheme

An 80 MHz bandpass filter with a tunable quality factor of 16∼44 using an improved transconductor circuit is presented. A noise optimized biquad structure for high-Q, high- frequency bandpass filter is proposed. The quality factor of the filter is tuned using a new quality factor locked loop algorithm. It was shown that a second-order quality factor locked loop is necessary and sufficient to tune the quality factor of a bandpass filter with zero steady state error. The accuracy, mismatch, and sensitivty analysis of the new tuning scheme was performed and analyzed. Based on the proposed noise optimized filter structure and new quality factor tuning scheme, a biquad filter was designed and fabricated in 0.25 μm BiCMOS process. The measured results show that the biquad filter achieves a SNR of 45 dB at IMD of 40 dB. The P-1dB compression point and IIP3 of the filter are -10 dBm and -2.68 dBm, respectively. The proposed biquad filter and quality factor tuning scheme consumes 58mW and 13 mW of power at 3.3 V supply.Ph.D.Committee Chair: Allen Phillip; Committee Member: Hasler Paul; Committee Member: Keezer David; Committee Member: Kenny James; Committee Member: Pan Ronghu

Log-domain Universal Biquad Filter Design Using Lossy Integrators

In this paper, a new current mode low voltage log domain Class A universal biquad filter is proposed. The proposed circuit is derived from the block diagram based on Kerwin-Huelsman-Newcomb (KHN) circuit using lossy integrators. The circuit can provide second-order low pass,band pass and high pass filter characteristics. State space method and translinear principle is used for circuit synthesis.The natural frequency f0 and quality factor Q of the circuit is electronically tunable by varying amplitudes of the current sources. PSpice simulation results are given in order to verify the theoretical analysis. The simulations are performed with both ideal transistor models and AT&T CBIC-R type real transistor models

Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

ON DESIGN OF SELF-TUNING ACTIVE FILTERS

In this paper, we present one approach in design of self-tuning all-pass, band-pass, low-pass and notch filters based on phase control loops with voltage-controlled active components and analyze their stability as well. The main idea is to vary signal delay of the filter and in this way to achieve phase correction. The filter phase characteristics are tuned by varying the transconductance of the operational transconductance amplifier or capacitance of an MOS varicap element, which are the constituents of filters. This approach allows us to implement active filters with capacitance values of order of pF, making the complete filter circuit to be amenable for realization in CMOS technology. The phase control loops are characterized by good controllable delay over the full range of phase and frequency regulation, high stability, and short settling (locking) time. The proposed circuits are suitable for implementation as a basic building RF function block, used in phase and frequency regulation, frequency synthesis, clock generation recovery, filtering, selective amplifying etc

10-GHz fully differential Sallen–Key lowpass biquad filters in 55nm SiGe BICMOS technology

Multi-GHz lowpass filters are key components for many RF applications and are required for the implementation of integrated high-speed analog-to-digital and digital-to-analog converters and optical communication systems. In the last two decades, integrated filters in the Multi-GHz range have been implemented using III-V or SiGe technologies. In all cases in which the size of passive components is a concern, inductorless designs are preferred. Furthermore, due to the recent development of high-speed and high-resolution data converters, highly linear multi-GHz filters are required more and more. Classical open loop topologies are not able to achieve high linearity, and closed loop filters are preferred in all applications where linearity is a key requirement. In this work, we present a fully differential BiCMOS implementation of the classical Sallen Key filter, which is able to operate up to about 10 GHz by exploiting both the bipolar and MOS transistors of a commercial 55-nm BiCMOS technology. The layout of the biquad filter has been implemented, and the results of post-layout simulations are reported. The biquad stage exhibits excellent SFDR (64 dB) and dynamic range (about 50 dB) due to the closed loop operation, and good power efficiency (0.94 pW/Hz/pole) with respect to comparable active inductorless lowpass filters reported in the literature. Moreover, unlike other filters, it exploits the different active devices offered by commercial SiGe BiCMOS technologies. Parametric and Monte Carlo simulations are also included to assess the robustness of the proposed biquad filter against PVT and mismatch variations