A 7-Bit Reverse-Saturated SiGe HBT Discrete Gain Step Attenuator

Abstract

In this study, the analysis, design and measured results of a fully integrated 7-Bit step attenuator implemented in a 0.25-µm Silicon-Germanium (SiGe) BiCMOS process technology, are described. The attenuator is designed based on delicately ordered and cascaded Π/T type attenuation blocks, which are comprised of series/shunt switches employing SiGe hetero-junction bipolar transistors (HBTs) with peak fT /fmax of 110/180 GHz. HBTs are employed as a series switch to decrease the insertion-loss of the attenuator. Moreover, to authors' best knowledge, this is the first study presenting the effect of employing reverse-saturated HBTs as a shunt switch for each attenuation blocks. Thanks to this advancement, the highest input-referred 1-dB compression point (IP 1dB ) is reported for Si-based similar studies. This method also decreases the insertion-loss of the proposed attenuator. The measurements result in the state-ofthe-art performance with 28.575 dB attenuation range by 0.225 dB gain steps while maintaining 7-bit amplitude resolution across 6.6 GHz to 12.8 GHz frequency band, where RMS phase error remains below 3.3 • and insertion loss (IL) is less than 12.4 dB. The measured IP 1dB of the attenuator is 13.5 dBm while drawing 8 mA from 3.3 V supply. The die occupies an area of 1.37 mm x 0.56 mm excluding pads.

GRNN-Based Scattering Parameter Modeling Investigation for HBT at Different Temperature

“…In 2019, HBT was used in the design of a low-noise amplifier (LNA) [2] that achieves a gain and noise figure with 14.2/14.2 dB and 8.2/8.2 dB at 120/140 GHz, respectively. In 2020, HBTs was adopted as series switches to reduce the insertion loss (insertion-loss) of the attenuator [3], and the RMS phase error of the proposed attenuator was within a small range. In 2020, GaAs HBTs were used by W. Y. Refai in the design of a high efficiency multimode multiband (MMMB) linear RF power amplifier for multi-chip modules in wireless handsets [4], which was capable of operating in multimode (saturated/linear) and covering multiple frequency bands.…”

A wideband high dynamic range triple‐stacked FET dual‐shunt distributed analogue voltage controlled attenuator

“…Conventional single transistor VCAs have very limited power handling capability, especially when being deployed in GaAs and CMOS processes [2,3,11]. Therefore, a stacked-FET topology is proposed to overcome such limitations.…”

“…On the other hand, while digital discrete-step attenuators can provide high resolution, the attenuators require complicated digital control circuits. Thus, they are more suitable for CMOS and SiGe processes [2,3]. Analogue voltage control attenuator using Gallium Arsenide (GaAs) processes have recently attracted more attention because of its simplicity, high power, and low insertion loss.…”

A 10–20 GHz 6-Bit High-Accuracy Digital Step Attenuator with Low Insertion Loss in 0.15 µm GaAs p-HEMT Technology

“…However, it affects the signals in the path and introduces resonance Furthermore, the characteristic of RF switches also constitutes majorly to the attenuator performance. These switches are achieved by utilizing CMOS [24,25], BJT/HBT [26,27], and HEMT [28,29] transistors. Among the numerous processes available, the GaAs pseudomorphic high-electron mobility transistor (p-HEMT) process is generally preferred due to its low switching loss and high isolation.…”