## 1 Introduction  
Attenuators serve as a crucial component in RF communication, radar, and measurement systems. Their primary function is to provide amplitude control, including linearity adjustment and damage protection [1, 2]. The phased array system, with its high precision beam pointing, fast beam synthesis, and scanning capability, is widely used in modern RF-integrated systems such as radar remote sensing and low orbit broadband satellite communications. In phased-array systems, attenuators are required for high accurate amplitude control to obtain lower side lobe levels, better null points, and higher beam sharpness. Digital step attenuators (DSAs) show superior switching speed, reduced power consumption, enhanced linearity, minimal current variation, precise amplitude control, and diminished amplitude/phase change characteristics when compared to variable gain amplifiers. Furthermore, digital attenuators demonstrate higher attenuation accuracy, an improved voltage standing wave ratio, and a broader attenuation dynamic range when compared to continuous variable attenuators [3, 4, 5, 6]. In passive DSAs, three primary topologies have been investigated in the literature: distributed, switched path, and switched T-/\(\pi\)-type attenuators [7; 8; 9; 10], where, TL is a \(\lambda\)/4 microstrip line, Ms is a series transistor, Mp is a parallel transistor, Rs is a series branch resistor, Rp is a parallel branch resistor, and Vc and \(\overline{\text{Vc}}\) are a pair of complementary voltages for controlling the on and off of the transistor. Switched path attenuators use single-pole-double-throw (SPDT) switches to steer the signal path between a thru line and a resistive network, as shown in Figure 1a. This topology provides low phase variation over attenuation states, but it shows high insertion losses at reference states due to the cumulative losses of all SPDT switches for a multi-bit design, and it occupies a large chip area [7; 8]. Distributed attenuators do not have series switches in the signal path and therefore have the advantage of low insertion loss, as shown in Figure 1b. However, they show lower maximum attenuation values and larger chip sizes [9; 10]. Switched T-/\(\pi\)-type attenuators show low IL, high maximum attenuation, and compact size, as shown in Figure 1c. However, they still show relatively large attenuation variation and phase variation at higher frequencies, which can limit fine amplitude control in broadband applications [11; 12; 13]. The primary source of errors in the amplitude and phase of switched T-/\(\pi\) attenuators is attributed to the parasitic capacitance (Coff) of switching transistors [14]. In order to minimize the Coff-induced errors and improve the accuracy of the attenuator amplitude and phase, several compensation structures have been proposed recently. References [15; 16] introduced a parallel capacitive compensation structure that transforms the attenuator into a two-pole, two-zero system, significantly reducing phase error. However, the insertion loss of this structure rapidly deteriorates with frequency increase. At 6 GHz, the insertion loss  
Figure 1: Topologies of DSAs. (**a**) Switched path attenuator. (**b**) Distributed attenuator. (**c**) Switched T/\(\pi\) attenuators. reaches 2.3 dB and 4 dB, respectively. Consequently, this structure is unsuitable for ultra-wideband attenuators. Adding a tail capacitor in the shunt branch was reported in [17], but this series capacitor limits the bandwidth, counteracting the benefits of the switched-type topology. The inductive compensation structure shows a lower insertion loss compared to the capacitive compensation structure. A parallel inductive compensation structure was introduced by reference [18]. However, the inductor is parallel to the resistance network, resulting in a smaller attenuation value. To address this issue, additional series resistance needs to be incorporated, thereby increasing circuit complexity.