Abstract
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.
Highlights
Integrated multi-GHz-band lowpass filters are required as antialiasing filters for very high-speed analog-to-digital (ADC) and digital-to-analog (DAC) converters [1] in applications such as wideband spectrum monitoring, high bit-rate optical communications [2,3] and wideband measurement systems [4,5]
With respect to comparable active inductorless lowpass filters reported in the literature
Inductorless GHz-band lowpass filters in the literature are often based on RLC reference structures, with the use of active inductance circuits to substitute the physical inductors
Summary
Integrated multi-GHz-band lowpass filters are required as antialiasing filters for very high-speed analog-to-digital (ADC) and digital-to-analog (DAC) converters [1] in applications such as wideband spectrum monitoring, high bit-rate optical communications [2,3] and wideband measurement systems [4,5]. 5th order 4.57-GHz lowpass filter in 180-nm CMOS, and [14] that describes a 10.5-GHz biquad in SiGe. On the other hand, the ever-increasing frequency performance of advanced bipolar technologies and deep submicron CMOS allows achieving huge gain-bandwidth products, making it possible to adopt a closed-loop approach for the design of multi-GHz filters. The ever-increasing frequency performance of advanced bipolar technologies and deep submicron CMOS allows achieving huge gain-bandwidth products, making it possible to adopt a closed-loop approach for the design of multi-GHz filters This allows using filter design techniques that are typically adopted at lower frequencies, both for the topology of the basic filter stage, the biquad, and for the system design of higher order filters under technology constraints (e.g., limits on the maximum quality factor that can be achieved) [15,16].
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