In this paper a novel 1-bit phase shifter topology based on dual input Low Noise Amplifier (LNA) for Active Reflective Intelligent Surfaces (Active RIS) is presented. The proposed solution is advantageous when the LNA has to be switched between two different radio-frequency (RF) sources. In particular, the Active RIS receiving (RX) patch antenna has two opposite feed points in order to obtain a 0° and 180° phase shifted signals entering the dual input LNA. A 1-bit digital enable (EN) signal is used to select one of the two inputs at a time, making the LNA behaves as pseudo-switch. Experiments were carried out on a fabricated prototype. The reported results show good agreement with simulations, thus validating the LNA operation. The LNA is based on a 130 nm SiGe BiCMOS technology, operating between 20 and 30 GHz with a 13 dB gain and 3 dB noise figure.

Self-testing solution are very useful not only for make sure that devices are operating in the correct way, but also to realize system auto-calibration: auto-calibration is based on the experimentally extraction of proper parameters and it is usually realized by adopting radio frequency noise injection subsystems. In these cases, the systems use power acquisition devices, based on diode detectors, to perform the measurements; this solution denotes poor reconfigurability, unless a very complicated system architecture is adopted. In this paper we prove that the measurements needed for the over mentioned purpose, can be performed avoiding the application of complex architectures, by using software-defined radios with high level of potential reconfigurability and flexibility.

Solid-state noise sources are essential components in highly reliable mm-wave systems for life- or mission-critical applications such as self-driving car radars, airborne and satellite communication systems, space science instruments, and 6G to THz communications. Integrating a noise source, typically based on the avalanche effect of diode junctions, allows for testing of the architecture during production and operational lifetime. This paper presents a comparative study of three avalanche noise diodes integrated in different silicon technologies. The study is based on a solid experimental work that highlights the key points for a successful device design aimed at increasing the generated noise power, bandwidth, and operating frequency.

This paper presents a passive wireless harmonic transponder capable of transmitting information acquired by its vibration sensor. The system is equipped with a Schottky diode frequency doubler which converts the received signal from f ₀ to its second harmonic 2 f ₀. The sensed information is then encoded in the 2 f ₀ carrier phase using a varactor phase-shifter (acting as the phase modulator) biased through a piezoelectric transducer (which senses the mechanical vibrations). The transponder operation is demonstrated with particular focus on piezoelectric transducer vibrating resonance frequency. The side-band amplitude of the backscattered signal increases by about 10 dB for an increment of the acceleration of the mechanical system under test of 1.5 g 128 Hz.

This paper investigates, for the first time, the feasibility of harmonic tag sensors based on orthogonally polarized waves. The main tag building blocks (circular and dual polarization antennas, Schottky diode frequency doubler and phase shifter) are designed, implemented with standard PCBs technology and materials, and experimentally characterized. Finally a proof-of-concept of the whole system operating at 1.04/2.08 GHz is proposed and validated in laboratory. The system can recover the encoded phase regardless the interrogation distance.

Integrated noise sources are fundamental for precise gain and noise figure measurements in Built-In Test Equipments. In this paper a custom-developed, avalanche noise diode model is used in a commercial CAD software and applied to the input of a Ka-band Low Noise Amplifier for Built-In Self-Test purposes. Few noise diodes have been characterized in recent years, and among those whose models are available in the literature, the 20μm2 p-i-n diode developed with commercial 130-nm SiGe BiCMOS technology is considered. The diode is connected with an LNA realized in 130-nm SiGe BiCMOS IHP technology. Noise measurements are simulated to extract the noise figure and gain of the LNA. The extracted parameters are then compared with those autonomously simulated with the CAD. The obtained results show the importance of simulations in defining the theoretical limits of a noise BITE in ideal power measurements conditions. Moreover they present how the model can be successfully used to simulate a noise Built-In Test Equipment block for calibration purposes.

Avalanche noise diodes have recently been demonstrated in standard Si technologies such as CMOS and SiGe BiCMOS processes and used to design fully integrated noise sources. This letter investigates the reproducibility (die-to-die and run-to-run) and the stability over time of these devices. On-wafer noise sources are indeed relevant because of their extensive use in mm-wave noise measurements and for the calibration of high performance, single-chip receivers and radiometers. The results, obtained for the case study 30-GHz noise sources in 130-nm SiGe BiCMOS technology, show that a 0.3-dB reproducibility is achieved (ten dice fabricated in three different foundry runs) and that the generated noise has a stability of 0.07% in a period of 1000 min (Allan deviation of fractional temperature fluctuations). This will enable a new class of built-in test equipment (BITE) for terrestrial and space applications.

This contribution demonstrates, for the first time, on-chip Built-In Self Test (BIST) circuits based on avalanche noise diodes, a class of devices that are recently developed up to millimeter-waves in commercial Si technologies. The proposed BIST is constituted by a Low-Noise Amplifier (LNA) integrated with an avalanche p-i-n diode. The LNA has two equal channels that can be enabled independently. The first channel is connected to the input pads and, when active, the circuit operates as a standard LNA. The second channel, instead, is tied to the noise diode through a coupling capacitor and a 6-dB resistive attenuator. If the second channel is selected, the LNA works in self-test mode. As a consequence, the LNA gain and noise figure can be determined by switching on and off the integrated noise source and measuring the output noise power in these two conditions. The fabricated LNA (14.4-dB gain and 3.8-dB noise figure) is based on a 130-nm SiGe BiCMOS technology and operates between 20 and 30 GHz, i.e., in a frequency band compatible with 5G services. The integrated noise source (avalanche p-i-n diode with attenuator) has an Excess Noise Ratio (ENR) of about 17 dB at 30 GHz when biased with a 4 mA current. Experiments shows that measurements from the input pads (LNA mode) agree with those using the internal noise source (BIST mode) within 0.7 dB for gain and 1.3 dB for noise figure.

This paper presents a passive wireless vibration sensor capable to transmit the information related to both vibration frequency and amplitude. These information are encoded in the interrogation carrier phase using a varactor phase-shifter (acting as the phase modulator) directly connected to a piezoelectric transducer (which senses the mechanical vibrations). The phase shifter consists of a 90-degree hybrid junction in which the direct and coupled ports are closed on identical reactive impedances: a voltage-controlled variable capacitance (varactor diode) and a fixed inductor. The sensor is intended to be part of a passive wireless harmonic transponder able to retrieve the sensor information from the re-transmitted modulated signal. The sensor demonstrated to sense vibration up to 400 Hz with a 2 g peak acceleration. For the re-transmitted signal, the sidebands amplitude increases of about 10 dB as the acceleration of the mechanical system under test varies between 0.5-2.0 g at 100 Hz.

Hybrid couplers are important devices that combine or divide signals in various microwave applications. Wideband performance, low losses and small size are key features in most modern radar and communication systems. This paper presents a new geometry for single-ridge, air-filled waveguide quadrature hybrid couplers at the X/Ku band on a single layer using multiple pairs of slots cut on a common ridge coupling section. Bandwidth can be progressively extended by increasing the number of slot pairs. Two designs characterized by compact size and state-of-the-art performance are proposed, leading to a fractional bandwidth up to 46.88% and a maximum dimension of 1.18 wavelengths. A tolerance analysis is presented to highlight the design robustness and reliability.

The era of Internet-of-Things is leading to the widespread of sensors in medical and consumer applications, where electronics is aiming at being wireless, battery-less, lowcost and wearable. In this context, pressure sensors are of particular interest since they can be used to monitor parameters such as human posture, motion and interaction with the environment. This paper presents a novel zero-power pressure sensor with wireless communication and wireless powering feature, with a flexible sensing element. The key component of the sensor is a Schottky-diode harmonic transponder connected to a piezoresistive transducer. The piezoresistor is placed along the DC path of the rectifier circuit in order to control the rectifying behaviour of the diode and thereby encoding the information about pressure on the backscattered signal. This sensor is a proof of concept of a novel fully-passive and wireless pressure sensor with a flexible sensing element.

This paper proposes, for the first time, a completely stand alone avalanche diode model based on a C++ code. The code, implemented within the Advanced Design Systems (ADS) environment, describes the diode behavior in terms of impedance and noise, by means of equations for which no more look-up tables are required. This also contains a modification with respect to the original Gilden and Hines model. Although completely general, the model is presented and discussed using a 20 square microns p-i-n diode, previously published by the authors. In order to validate the model in complex systems, the aforementioned diode is placed within two circuits of practical interest that have been designed using a commercial 130-nm SiGe BiCMOS technology. In particular: (a) the diode is connected with a wide-band bias tee and an 6-dB attenuator, in order to create a Noise Source (NS) system block, and (b) the same NS structure is connected with an Low-Noise Amplifier (LNA). The two prototypes have been fabricated and experimentally characterized in terms of impedance and Excess Noise Ratio (ENR). Finally the experimental results have been compared with model simulations. In the frequency range from DC to 26.5 GHz the agreement between simulated ENR and experiments is within 1.4 dB for the prototype (a) and 1.9 dB for the prototype (b). The obtained results enable the adoption of avalanche noise diodes in Computer Aided Design (CAD) tools, for the prediction of integrated circuits performances, and confirms the reliability of the developed model.

This contribution describes the feasibility of a wireless sensor that uses Micro-Electro-Mechanical Systems (MEMS) on cellulose materials. In particular, the focus is on a paper-aluminum (paper-Al) bimorph cantilever formed by an Al foil glued on top of a paper layer. It is well known that paper relaxes its fibers in the presence of humidity. This means that the length of the paper layer increases (respect to the Al layer) when humidity is absorbed, thus determining the cantilever deflection. Such a mechanism is used to control a capacitor formed by the cantilever itself (Al layer) and by a metal plate printed on a PCB. The capacitor is then applied to a planar notch filter whose resonant frequency is hence determined by the humidity. The preliminary experiments show that the developed circuit features a 2.45 GHz center frequency and a sensitivity of about 3.7 MHz ner each nercent of relative humidity variation.

Integrated noise sources (or hot loads) are essential to enable precise gain and noise figure Built-In Test Equipment (BITE) measurements. The present paper describes a millimeter-wave, solid-state noise source implemented in a standard, 130-nm Silicon-Germanium (SiGe) Bipolar-Complementary Metal Oxide Semiconductor (BiCMOS) process. This device is based on a p-i-n (varactor) diode that has two states: a cold state, when it is off, and an hot state when the diode is driven into avalanche breakdown. Two noise diodes with 10 and 20 square microns area have been fabricated and experimentally characterized. The measurements highlight a breakdown voltage is close to 10.7 V, whereas Excess Noise Ratio (ENR) equal to 16 dB (10 square microns diode) and 19 dB (20 square microns diode) are observed at 40 GHz, for a current density of 0.1 mA per square micron. For the first time the ENR is studied as a function of the physical device temperature, showing a slight decrease of -0.008 dB/K as the temperature increases from 298 to 358 K. An accurate modeling of the noise source is finally provided through a small-signal equivalent circuit that can be easily implemented into Computer Aided Design (CAD) tools. This contains some modifications with respect to the original Gliden and Hines model. The obtained results enable the employment of p-i-n avalanche noise diodes for the automatic characterization of integrated circuits in the production environment, as well as for the calibration of millimeter-wave receivers and radiometers during their operational life.

This paper proposes a Ka-band receiver front-end for future CubeSats Low-Earth Orbit (LEO) to Geostationary (GEO) inter-satellite links. The receiver is able to support very high data rates (up to 100 Mbit/s) in Quadrature Phase-Shift Keying (QPSK) when in the line of sight of a GEO satellite that is equipped with a steerable 70-cm antenna and transmitting a 25-W signal. The originality of the proposed approach is twofold. First we will demonstrate the receiver feasibility based on a class of miniaturized and low-cost microwave integrated circuits, currently available on the market. In particular, our receiver is based on a novel combination of integrated Low-Noise Amplifiers (LNA) with an image rejection filter, the latter exploiting the Substrate Integrated Waveguide (SIW) technology. An optimization of the via placement proved to be able to reduce the need for shielding apparatuses, thus simplifying the mechanics and reducing mass, volume and hardware costs. Secondly, we will propose a noise injection circuit capable of measuring and calibrating the receiver gain, also during in-orbit operation. Self testing capabilities are particularly relevant for CubeSats because the usage of commercial components poses serious reliability issues.

In this work the feasibility of a low-cost microwave noise source compatible with commercial BiCMOS technologies is discussed. The proposed circuit exploits the avalanche noise generated by the base-emitter junction of a Bipolar Junction Transistor (BJT) in reverse breakdown. The collector terminal is not used and thus it is left open. The feasibility study is carried out exploiting the BFP640 device, a packaged BJT realized with a f _T= 70 GHz process. A breakdown current of about 3 mA is obtained by reverse biasing the base-emitter junction at 4.5 V. In these conditions the Excess Noise Ratio (ENR) of the source is greater than 20 dB from 0.5 to 4.5 GHz.

This letter deals with microwave noise diodes in avalanche regime. Starting from the model proposed by Hines and Gliden in 1966, the asymptotic excess noise ratio (ENR) expression is derived for ω → 0. The developed theory is then validated against ENR measurements of three noise diodes already published in the literature. The agreement between theory and measurements is good and the obtained formula also predicts the 1/I ₀ behavior of the ENR at low frequencies. This study is relevant because it simplifies the experimental determination of the average time between two ionizations (the Hines τ _x model parameter) by means of low-frequency noise measurements only.