Ernesto Limiti

• Professor
• Microwave Engineering Center for Space Applications (MECSA) Head at University of Rome Tor Vergata

This manuscript provides insight into optimally noise-matched three-stage Low-Noise Amplifiers (LNAs) by proposing a novel chart that illustrates the relationship between the gain of a three-stage LNA and inter-stage mismatch levels. Under certain conditions, the chart also indicates the required feedback inductor values for all transistors. It is...

Millimeter-wave (mm-Wave) wireless communication systems play a central role in meeting the demands of next-generation wireless technologies such as 5G. This chapter presents the design and analysis of three advanced antenna arrays optimized for mm-Wave 5G wireless networks operating over K-band (18–27 GHz) and Ka-band (27–40 GHz). These structures...

A novel, analytical treatment of noise factor in ideal transmission lines subjected to thermal gradients is presented. Temperature dependence on the propagation direction is assumed linear, whereas line loss is initially considered constant. The latter restriction is then removed, in such a manner that, for the first time in the literature, linearl...

This work focuses on designing, fabricating, and testing a broadband low-noise amplifier (LNA) by exploiting dissipative reciprocal matching networks. With reference to a broadband power amplifier, the critical theoretical aspects of the proposed approach have already been presented in a previous publication from the same authors. Herein, the mathe...

This paper presents the design of four phase shifters (+45°, +90°, +135°, +180°) for matrix-based beamforming networks (MB-BFN) in mm-wave antenna arrays. Utilizing groove gap-waveguide (GGW) technology with unequal-width, equal-length transmission lines, the design incorporates metasurface principles to achieve perfect magnetic conductor (PMC) bou...

This study highlights the potential of employing terahertz metamaterial structures as dual-band biosensors for the early detection of cancerous biological tissue. The fundamental principle leveraged here is the alteration of the effective dielectric constant of biological tissue by cancerous cells. The change in the dielectric constant, in turn, in...

Some advancements are proposed to the theory of simultaneous conjugate match (SCM) of $N$ -ports. It is shown that, if a network qualifies for geometrical unconditional stability (g-), then it can be matched simultaneously at all ports. The proof serves as the basis for constructing an iterative algorithm (AlgG) which is guaranteed to converge to...

Phased array antenna (PAA) technology is essential for applications requiring high gain and wide bandwidth, such as sensors, medical, and 5G. Achieving such a design, however, is a challenging and intricate process that calls for precise calculations and a combination of findings to alter the phase and amplitude of each unit. Furthermore, coupling...

Phased array antennas with broadband and super-wideband (SWB) capabilities, featuring extensive scanning and end-fire radiations, are imperative to meet the evolving demands of future cellular systems. This paper explores the properties of a new design, incorporating low-profile and SWB resonators tailored for advanced fifth-generation (5G) communi...

In a recent paper, it has been shown that, if an N‐port network fulfills the condition of (geometrical) unconditional stability at a given frequency, then its scattering parameters will also necessarily satisfy N easily computable bounds, one per port. In order to complete that picture, this contribution investigates whether a tighter bound can be...

The availability of low-noise and low-voltage Gallium Nitride technologies enables new microwave receivers concepts for satellite payloads. In this note we present the potentials, benefits and drawbacks of a Low-Noise Amplifier at Ka-band operating at rather low drain voltages in a 100-nm gate length technology. Possible receiver improvements thank...

In this paper, a low-noise amplifier (LNA) having ultra-low voltage is presented, intended for active antenna SATCOM applications. The amplifier is composed of three common-source stages with inductive source degeneration and is realized in a 0.1 \(\upmu \)m GaAs process provided by United Monolithic Semiconductors (UMS). The proposed LNA can opera...

A fundamental step in the design of electronic circuits is the verification that they are stable at least on a given set of external terminations, in order to avoid that the solution found be not observable in practice. This is especially true at microwave and millimeter-wave circuits, which are typically analyzed in the frequency domain rather tha...

In this paper, a reconfigurable Multiple-Input Multiple-Output (MIMO) antenna array is presented for 5G portable devices. The proposed array consists of four radiating elements and an Electromagnetic Band Gap (EBG) structure. Planar monopole radiating elements are employed in the array with Coplanar Waveguide Ports (CWPs). Each CWP is grounded on o...

In this paper, we propose a novel MIMO antenna array configuration that incorporates metamaterial isolation surfaces to enhance overall performance. We demonstrate that the directivity of this antenna array can be precisely electronically reconfigured using PIN diode switches. Additionally, we show the feasibility of integrating solar panels with t...

The first issue that needs to be addressed when designing a high-frequency amplifier is whether the circuit performance specifications can be met with the selected technology. In case the termination on one of the ports of the active device is fixed, the problem is usually solved using the gain and mismatch limits available in the literature. Other...

Advanced interconnect technologies are enabling solutions to obtain adequate low-noise amplifier performance even when the circuit is packaged and connected inside a receiver module. In this letter, we present suitable technology and design solutions of a gallium arsenide low-noise amplifier operating in the telecom W-band (92–115 GHz) featuring 20...

This contribution presents the AM/AM and AM/PM characteristics of a 6-bit Phase and Amplitude Setting Circuit realized in Gallium Nitride technology and operating at the Ku band. A test bench, based on three vector receivers and an absolute power reference, has been purposely devised to capture the deviation with respect to the linear behavior (kno...

This paper presents a high‐performance multiple input and multiple output (MIMO) antenna comprising 2 × 2 configuration of radiating elements that is designed for sub‐6 GHz applications. The proposed MIMO antenna employs four identical radiating elements. High isolation between the radiating elements and therefore reduced mutual coupling is achieve...

In this work, a simple and efficient approach is presented to design a metamaterial based sensitive sensor for liquid characterization. The proposed sensor based on the Hilbert structure has a compacted size of 40×60×1.6mm3. The Hilbert curve is used to enhance the sensitivity of the sensor by increasing the interaction area with the sample tested....

Recently, within the framework of a project funded by the European Space Agency, two concept demonstrators in OMMIC’s industrial-grade GaN HEMT technology on a Silicon substrate have been developed. The first test vehicle is an ultra Low-Noise Amplifier (LNA), realized in OMMIC’s 60-nm GaN HEMT technology, demonstrating state-of-the-art 1.2 dB Nois...

Gallium Nitride is becoming an interesting solution for low-noise applications in the lower part of the millimetre-wave spectrum and is gaining increasing attention in the space community for microwave receiver functionalities. Lately, its maturity level has increased and its performance in terms of noise figure and operating frequency is reaching...

This paper proposes a transmitter system based on direct antenna amplitude-shift keying modulation for point-to-point microwave link. The proposed system is formed from a conventional microstrip antenna and a novel reconfigurable metasurface layer (RMSL). The proposed RMSL has two states: OFF (or Logic-0) and ON (or Logic-1) where each switching sc...

The design, realization, and test of a $Ka$ -band gallium nitride (GaN) monolithic microwave-integrated circuit (MMIC) single-chip front-end (SCFE) is presented. The MMIC, realized in OMMIC’s 100-and 60-nm gate length GaN on Silicon process, integrates high-power and low-noise amplification together with transmit or receive selection switches in...

Design and characterization of a 6-bit Phase and Amplitude Setting circuit realized in Gallium Nitride MMIC technology operating in Ku-band are reported in this brief. An analysis of transistor periphery selection is provided in order to fulfil linearity parameters concurrently targeting other design constraints such as switch isolation and size. I...

Multiple antennas at each user equipment (UE) and/or thousands of antennas at the base station (BS) comprise the extremely spectrum efficient large scale multi‐user multiple input multiple output system (BS). Due to space constraints, the closely spaced numerous antennas at each UE may cause inter antenna interference (IAI). Furthermore, when one U...

An innovative off-chip antenna (OCA) is presented that exhibits high gain and efficiency performance at the terahertz (THz) band and has a wide operational bandwidth. The proposed OCA is implemented on stacked silicon layers and consists of an open circuit meandering line. It is shown that by loading the antenna with an array of subwavelength circu...

This paper presents a technique to mitigate multiple access interference (MAI) in multicarrier code division multiple access (MC-CDMA) wireless communications systems. Although under normal circumstances the MC-CDMA system can achieve high spectral efficiency and resistance towards inter symbol interference (ISI) however when exposed to substantial...

The paper presents the results of a novel 3-D shared aperture 3×3 matrix antenna-array for 26 GHz band 5 G wireless networks. Radiation elements constituting the array are hexagonal-shaped patches that are elevated above the common dielectric substrate by 3.35 mm and excited through a metallic rod of 0.4 mm diameter. The rod protrudes through the s...

A new indicator of unconditional stability is proposed, which is well suited to $N$ -port networks called the stability radius . When compared to previous work on this subject, the new indicator is unique, irrespective of $N$ , and has a clear geometrical interpretation in terms of allowed reflectances in the termination planes. The latter as...

In this paper, we present an analytical study for the investigation of the effects of the magnetoelectric elements of a reciprocal and nonreciprocal bianisotropic grounded substrate on the input impedance, resonant length of a dipole antenna as well as on the mutual coupling between two element printed dipole array in three configuration geometries...

A novel technique is shown to improve the isolation between radiators in antenna arrays. The proposed technique suppresses the surface-wave propagation and reduces substrate loss thereby enhancing the overall performance of the array. This is achieved without affecting the antenna’s footprint. The proposed approach is demonstrated on a four-element...

A compact, frequency reconfigurable antenna is proposed in this paper for 5G applications. Initially, a conventional circular patch antenna was modified using two pairs of open ended horizontal and vertical stubs. Stubs cause the improvement in impedance matching along with increased effective area of the radiator. Afterwards, two PIN diodes were i...

This paper aims to design a compact broadband antenna for wireless local area network (WLAN) and worldwide interoperability for microwave access (WIMAX) applications. The suggested antenna consists of an octagonal radiator with Vicsek fractal slots and a partial ground plane, it is printed on FR-4 dielectric substrate, and its global dimension is 5...

In this paper, a low-profile, compact size, inexpensive, and easily integrable frequency reconfigurable antenna system is proposed. The proposed antenna consists of an inverted-F shape antenna, capacitors, and switching PIN diodes. The designed antenna element is fabricated on easy available and less expensive FR-4 substrate ( ε r = 4.4, tan δ = 0....

Antennas in wireless sensor networks (WSNs) are characterized by the enhanced capacity of the network, longer range of transmission, better spatial reuse, and lower interference. In this paper, we propose a planar patch antenna for mobile communication applications operating at 1.8, 3.5, and 5.4 GHz. A planar microstrip patch antenna (MPA) consists...

A Ka-band low-noise amplifier for low-consumption robust receivers is presented in this letter. The monolithic microwave integrated circuit (MMIC) is designed on a 100 nm GaN-on-Si technology provided by OMMIC foundry and decibel gain, average noise figure (NF) of 1.5 dB, with input-output return losses better than 15 dB in the whole 27-31 GHz desi...

Antennas on-chip are a particular type of radiating elements valued for their small footprint. They are most commonly integrated in circuit boards to electromagnetically interface free space, which is necessary for wireless communications. Antennas on-chip radiate and receive electromagnetic (EM) energy as any conventional antennas, but what distin...

Unconditionally stable 2-ports exhibit the peculiar property of mapping regions in the passive termination plane into smaller regions in the input plane. Such a ‘contractive’ behavior is observed also when the number of ports, $N$ , is larger than two, provided the notion of output region is appropriately adjusted. Based on this premise, it is sh...

The stability criteria based on the Rollett parameter ( $K$ ) plus one auxiliary condition is yet the most popular method used by designers to evaluate the stability of a two-port network although other criteria are available. In this paper, novel analytical proofs of the criteria utilizing $K$ and a new geometrical proof of the relationship bet...

In this article, we investigated the secrecy performance of a three-hop relay network system with Power Splitting (PS) and Energy Harvesting (EH). In the presence of one eavesdropper, a signal is transferred from source to destination with the help of a relay. The source signal transmits in full-duplex (FD) mood, jamming the relay transfer signals...

High Power Microwave (HPM) sources are widely used as signal sources in radar, jammer, and Counter Improvised Explosive Devices (CIED). Such devices usually are heavy and bulky, characteristics that are in conflict with the small weight and power (SWaP) approach so that it is practically impossible to mount such HPMs on several platforms with reduc...

An easy-to-manufacture and efficient four-port-printed Multiple Input Multiple Output (MIMO) antenna operating across an ultra-wideband (UWB) region (2.9–13.6 GHz) is proposed and investigated here. The phenomenon of the polarization diversity is used to improve the isolation between MIMO antenna elements by deploying four orthogonal antenna elemen...

In this paper, an automated impedance matching circuit is proposed to match the impedance of the transmit and receive resonators for optimum wireless power transfer (WPT). This is achieved using a 2D open-circuited spiral antenna with magnetic resonance coupling in the low-frequency ISM band at 13.56 MHz. The proposed WPT can be adopted for a wide...

In this work, a new prototype of the eight-element MIMO antenna system for 5G communications, internet of things, and networks has been proposed. This system is based on an H-shaped monopole antenna system that offers 200 MHz bandwidth ranges between 3.4–3.6 GHz, and the isolation between any two elements is well below −12 dB without using any deco...

In this paper, an umbrella-shaped patch antenna for future millimeter-wave applications is presented. The proposed antenna resonates at multiple frequency bands at 28 GHz, 38 GHz, and 55 GHz (V-band) that have been globally allocated for 5G communications systems. The proposed antenna is designed using Rogers RT/duroid 5870, with a thickness of 0.7...