# A g\({}_{m}\)/I\({}_{\rm D}\)-Based Low-Power LNA for Ka-Band Applications  
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Footnote 25:to obtain a circuit given a target specification. The main principle of the methodology is the use of a device-independent parameter (frequently, a figure of merit such as the inversion coefficient or the g\({}_{m}\)/I\({}_{D}\) ratio) as the main design parameter to explore the design space or determine the optimal operation region. Thanks to the generated LUTs, the need for iterative simulations is removed and near-first-time success can be achieved to cover the design requirements. Although the g\({}_{m}\)/I\({}_{D}\) methodology was born in the field of low-frequency analog integrated circuit design, significant efforts have been made to integrate this methodology with radiofrequency (RF) and microwave (MW) circuit design [14; 20; 21; 22; 23], demonstrating the implementation of very-low-power RFICs. However, these proposals are limited to operating frequencies of only 2.4 GHz, with no g\({}_{m}\)/I\({}_{D}\)-based LNA designs above an operating frequency of 5 GHz reported.  
In contrast to traditional bulk silicon (Si) complementary metal-oxide-semiconductor (CMOS) processes, silicon-on-insulator (SOI) technologies present multiple advantages, such as reduced parasitic capacitances, higher quality factor (Q, figure of merit related to passive components' narrow-band response and insertion loss), improvement of device performance and speed, downsizing to nanometer dimensions, reduction in device operating voltage, lower power consumption, and reduced leakage currents, among others [24]. Although III-V compounds such as gallium arsenide (GaAs) technologies are generally employed in very-high-frequency scenarios with demanding NF requirements such as mm-wave applications, 5G networks, or satellite communications (SATCOMs), SOI technologies provide a comparable performance while facilitating system integration with lower production costs. Both III-V and SOI technologies can find application in high-resolution radar, short-range military aircraft radios, and astronomical observations, which operate at Ka-band frequencies [25; 26; 27; 28; 29]. For instance, the 28 GHz frequency band is identified as a pioneer band to host 5G new radio (NR) networks worldwide. It provides a very high data rate and capacity, making it a convenient choice for hotspot coverage. In this sense, the European Union designated the n258 and n257 frequency bands, which extend from 24.25 to 27.5 GHz and 27.5 to 29.5 GHz, respectively, the US identified the 27.5-28.35 GHz band, and Japan and Korea considered the 27.5-29.5 GHz and 26.5-29.5 GHz bands, respectively, for the same purpose [30]. Therefore, the developments introduced in Ka-band LNAs greatly benefit 5G mm-wave systems and applications all over the world.  
In this work, we apply the g\({}_{m}\)/I\({}_{D}\) methodology, adapted to an RF/MW environment, to obtain a Ka-band very-low-power LNA with a remarkable performance thanks to the advantages introduced by exploiting the moderate inversion region of a MOSFET. The proposed LNA achieves a very low power consumption of only 1.98 mW and is the first time the g\({}_{m}\)/I\({}_{D}\) approach is applied at such a high frequency. The 28 GHz cascode LNA is implemented in GlobalFoundries 45 nm RFSOI and occupies an area of 1.23 mm\({}^{2}\) excluding pads. The circuit achieves a gain of 11.4 dB with an NF of 3.8 dB and input return loss (IRL) better than 12 dB when fed from a 0.9 V DC supply, drawing only 1.98 mW. The organization of this paper is the following. Section 2 presents the circuit design of the proposed g\({}_{m}\)/I\({}_{D}\)-enabled LNA. Section 3 shows the post-layout simulation results and Section 4 concludes this paper.