This paper presents the design and test results of a multi-band multi-tone tunable millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a satellite beacon transmitter for radio wave propagation studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). In addition, the architecture for a compact beacon transmitter, which includes the multi-tone synthesizer, polarizer, horn antenna, and power/control electronics, has been investigated for a notional space-to-ground radio wave propagation experiment payload on a small satellite. The above studies would enable the design of robust high throughput multi-Gbps data rate future space-to-ground satellite communication links.

This paper describes a new fabrication method for flexible electronics made of microfluidic structures filled with liquid metal in a thermoplastic elastomer, styrene ethylene butylene styrene (SEBS). The devices can reversibly be bonded to a larger system with gecko inspired dry adhesives. These devices have an electric conductor of EGaIn injected to dry adhesive inspired microfluidic channels made of SEBS fabricated with a simple, reliable, repeatable, and potentially large-scale manufacturing method. The gecko-inspired dry adhesives will provide us with the opportunity to fabricate strongly but reversibly bonded devices that can be integrated into systems and detached and modified without damage to the original device. To demonstrate the feasibility of the method, a mechanically reconfigurable folded dipole has been fabricated and 55% frequency tuning with a 20% to 40% bandwidth for various frequencies has been achieved.

This paper demonstrates a phase noise improvement technique for array systems by using the phase noise suppressor (PNS) and the noise uncorrelated feature. The uncorrelated feature of PNS circuit noise and correlated feature of input signal and noise improves the phase noise performance for array systems by 10×log(N), where N is the element number of the array. Both simulation and 2-element array measurement results verify this theory. The 2-element PNS array is demonstrated with phase noise sensitivity of -118 dBc/Hz at 1 MHz offset for a 10 GHz clock, improved from single element’s sensitivity of -116.1/-115.4 dBc/Hz respectively. The improvement is 2-3 dB, which is very close to the theoretical value. The phase noise suppression level and bandwidth are similar to the single PNS. The demonstrated -118 dBc/Hz at 1 MHz offset for a 10 GHz clock is the best result in CMOS processes based on the authors’ best knowledge.

The applications of orbital angular momentum (OAM) carried beams are limited by its on-axis phase singularity and wide-angle directivity. In this paper, a new form of OAM wave termed as plane spiral OAM wave is proposed. Different from general OAM wave propagating along the axial direction, plane spiral OAM wave has the distinguishing characteristic of transverse propagation. Hence it has no singularity along the the propagation path and divergence problem no longer exists. A traveling-wave circular slot antenna excited by a hybrid coupler is used to generate plane spiral OAM waves. Due to the ring horn outside the antenna, energy is focused on the radial plane and the generated waves are propagating in the transverse direction. The potential applications of plane spiral OAM waves, e.g., plane spiral OAM based multiple-in-multiple-out (MIMO) system and plane spiral OAM based beam-forming method, are also detailedly discussed.

An orbital angular momentum (OAM) multiplexed radio data link with the novel partial arc sampling receiving (PASR) scheme is experimentally demonstrated. These four coaxially propagating OAM waves with modes of l = -6, -2, +2 and +6 are generated by a Cassegrain antenna based on the dual ring-slot radiators. Over 10 m free-space transmission, four identical horn antennas uniformly located at the π/2 arc with a fixed radius of 45 cm are used to capture the four overlapped OAM waves. The de-multiplexing is then performed by digital phase-shift (DPS) at digital baseband. Experiment results show that the bit-error rates (BER) can reach below the forward error correction limit of 3.8×10-3 for all the four OAM channels. Multi-OAM-mode communications with the PASR scheme is capable of providing the receiving end with desired properties of compact size as well as easy realization.

Designing linear transmitters became mandatory to cater with high data rates applications and this trend is increasing, especially with 5G. This leads to a huge amount of energy consumption and important environmental challenges. For RF design point of view, the issue is improving energy efficiency, especially in user mobile equipment. This work proposes an original linear green RF transmitter system based on efficiency enhancement technique at the transmitter and linearization at the receiver in an uplink radio cognitive context.

Novel fabrication techniques to manufacture various high performance devices, using both Si and III-V nanomembrane-form materials, that are essential for portable electronics on a biodegradable cellulose nanofibril (CNF) paper are presented. We have introduced a concept of natural biodegradation of the discarded electronic chips that could help reduce the accumulation of the massive amount of persistent electronic waste disposed of daily using CNF that is derived from wood, a natural sustainable resource. CNF paper offers properties as a flexible substrate for high performance electronics. Essential microwave electronic systems, such as Si-based transistor and GaAs-based transistor and diode, were fabricated to demonstrate the feasibility of our novel approach on the CNF substrate. A novel releasable device fabrication technology, along with deterministic assembly printing technique for these high-performance devices, that significantly decreased the amount of GaAs used compared to conventional chip based manufacturing are presented.

Multifunctional structures have become popular within the past decade as they allow for more efficient utilization of limited real-estate available on many civilian and military platforms. Taking structures and electromagnetics, one can marry these two fields to produce a weight optimized loadbearing microwave structure which may ideally be suited for unmanned aerial systems. This paper investigates the use of textile processes to develop loadbearing smart skins built into a class of structural conformal composite materials called pre-pregs (resin pre-impregnated fabrics). An example of an active UWB mini-circuits ERA-4SM+ (0-4 GHz) amplifier has been investigated within a 48 g.m-2 pre-preg structural glass material (HexPly914E). This amplifier has been embroidered and cured at 170˚C in an autoclave at 700 kPa pressure. Its performance before and after curing has been examined.

An electrically tunable bandpass filtering balun (BPF-Balun) on engineered substrate embedded with patterned Permalloy (Py) thin film is designed and implemented. Embedded with patterned Py thin film which has high and current-dependent permeability, the developed engineered substrate has electrically tunable equivalent permeability. Patterning of Py film is analyzed and utilized to increase its FMR up to GHz range. The proposed BPF-Balun is fabricated on Rogers 4350 substrate while the engineered substrate is developed separately with high resistivity silicon embedded with patterned Py thin film. Tunable BPF-Balun is implemented through bonding the Rogers 4350 on the top of engineered substrate. The measured results show that the center frequency of the BPF-Balun can be tuned continuously from 1.49GHz to 1.545GHz with DC current adjusted from 0mA to 500mA. The measured magnitude imbalance and phase difference of the two balanced outputs are within 0.5 dB and 180°± 5° for the whole frequency range.

This paper presents a miniature wide-band interferometry sensor for dielectric spectroscopy and detection of liquid chemicals based on utilizing two composite right/left-handed (CRLH) transmission lines (TLs) in a zero-IF mixing configuration. The equivalent series capacitance of the CRLH TLs, constructed by using interdigital capacitors, is loaded with microfluidic channels, and exposed to the material under test to act as the sensing element. Due to the nonlinear dispersion relation of the artificial TLs with respect to the sensing capacitor, higher sensitivity over a wide frequency band of 4-8GHz is achieved, compared to the previously-reported resonator- or capacitor-based sensors. The final fabricated system prototype is 4 cmx8 cm. Moreover, a calibration method is presented based on measurement results, which shows an rms error less than 1.5% for liquid-chemical permittivity detection. To the best of author's knowledge, this is the first disclosure of wide-band and highly-sensitive microwave interferometry sensor suitable for portable applications.

Efficient oil production and refining processes require the precise measurement of water content in oil (i.e., water-cut [WC]). Traditional offline WC measurements are precise but incapable of providing real-time information, while online WC measurements are either incapable of sensing the full WC range (0-100%), restricted to a limited selection of pipe sizes, bulky or extremely expensive. This work presents a novel planar microwave sensor for entirely non-intrusive in situ WC sensing over the full range of operation, i.e., 0-100%. A planar configuration has enabled the direct implementation of WC sensor on the pipe surface using low cost methods such as 3D and screen printing. The innovative use of dual ground planes makes this WC sensor usable for the wide range of pipe sizes present in the oil industry. The viability of this sensor has been confirmed through EM simulations as well as through a prototype characterization.

A cold-plasma-based technique for tuning an evanescent-mode cavity resonator is introduced and studied experimentally for the first time in this paper. The technique involves a plasma jet that constitutes a variable resistance integrated in the cavity. The electron density and consequently the electromagnetic properties of plasma, including its resistivity, are controlled by varying the magnitude of the sinusoidal excitation voltage. The transmission coefficient of the two-port fabricated resonator at 2.735 GHz exhibits 11 dB tunability when the magnitude of the 20-kHz plasma-excitation voltage increases from zero to 5.26 kV (peak-to-peak). The resonator’s quality factor varies in the acceptable range of 684-342 for these conditions. The measured and simulated results reveal that this approach may become a promising tuning technology particularly in demanding applications where conventional solid-state techniques are ineffective due to temperature, power, or linearity limitations.

This paper presents a compact small signal equivalent circuit model of graphene resonant channel transistors (G-RCTs) suitable for different bias conditions. The model combines a bias dependent model for a GFET with a continuum mechanics model for 2-D graphene membrane. The model has been validated by graphene resonators fabricated by mechanical exfoliation techniques and transfer techniques. The characterization of G-RCT at very wide gate bias range with Vgs from -20 to 20V is predicted for the first time by using equivalent circuit model, which proves the validation of the proposed model. With the proposed compact model, the RCTs can be useful for developing high sensitivity sensor, or in the perspective of high quality RF filters by using graphene nano-electromechanical systems (NEMS).

A fully printed varactor and a phase shifter using direct ink writing methodologies will be described. A novel ferroelectric ink was developed to print high dielectric constant, low loss, and electrostatically-tunable dielectrics on plastic substrates. The dielectric is based on multiphase barium strontium titanate (BST)/polymer composite made by suspending nano/submicron-sized particles of BST in a thermoplastic polymer, namely cyclic olefin copolymer (COC). After printing with the ink, a low temperature curing process was performed at temperatures below 200°C. RF measurements and characterizations showed that the sinter-less dielectric had a very high relative permittivity of εr = 40 and a very low dielectric loss of tanδ = 0.0005 at f = 10 GHz. As a result, all-printed, voltage-variable capacitors with up to 10% capacitance tunability at microwave frequencies were realized. Eventually, the tunable BST/COC composite was used in a left handed transmission line design to realize a printed tunable phase shifter.

This paper presents a stub-loaded resonator bandpass filter fabricated on a liquid crystal polymer by using a multilayer inkjet printing process. A layer-by-layer deposition mechanism was achieved in the inkjet printing process by using metallic nanoparticle-based and polymer-based inks. Two dielectric layer thicknesses were determined in appropriate areas for deriving capacitive loading that enabled reducing the chip area by 89% and achieving a two-layer source-load coupling in the wide stopband of the proposed bandpass filter. A miniaturized bandpass filter was created with a minimal S21 of −3.2 at 13.8 GHz. The results demonstrated that the multilayer inkjet printing process provides high design freedom, a small size, low cost, and feasibility for the emerging field of wireless electronics.

In this paper, an inkjet-printed substrate integrated waveguide (SIW) on commercially available cellulose paper is implemented for the first time. Unlike traditional inkjet-printed SIW, it does not require any etching process to form the conductive side walls and utilizes the porosity of the paper to get through substrate conduction. The frequency response of the waveguide along with its performance under bending is discussed in the paper. Such structure would be particularly suitable for Quality-of-Life and Internet of Things applications

Additive manufacturing technologies are increasingly being demonstrated to be useful for microwave circuits, showing improved performance in multiple cases. In this work, a meshed rectangular waveguide structure is presented as an option for high power, low loss, but also reduced weight applications. A set of meshed Ku band waveguides was fabricated using binder jetting 3D printing technology showing that the weight can be reduced by 22% with an increase in loss of only 5%, from 0.019 dB/cm for the solid part to 0.020 dB/cm average across the band with the meshed design. Further weight reduction is possible if higher loss is allowed. To demonstrate the concept, a comparison is made between non-meshed and meshed waveguide 4 pole Chebyshev filters.

CMOS based RF circuits have demonstrated efficient performance over the decades. However, one bottle neck with this technology is its lossy nature for passive components. Due to this drawback, passives are either implemented off chip or the designers work with the inefficient passives. This problem can be alleviated by using inkjet printing as a post process on CMOS chip. In this work, we demonstrate inkjet printing of a patterned polymer layer on a 24 GHz oscillator chip to isolate the lossy Si substrate from the passives which are inkjet printed on top of the polymer layer. As a proof of concept, an antenna is printed on top of polymer layer integrating it with the oscillator through the exposed RF pads to realize a transmitter. The proposed hybrid fabrication technique can be extended to multiple dielectric and conductive printed layers to demonstrate complete RF systems on small and efficient CMOS chip.

This work outlines the development, fabrication, and measurement of fully inkjet-printed 3D interconnects for wireless mm-wave packaging solutions. Conductive silver nanoparticle and dielectric polymer-based inks are utilized to fabricate die attach, dielectric ramp, and CPW transmission line interconnect structures in order to interface a silicon die with a packaging substrate. Insertion and return loss are measured and compared with simulations over the range of 0–40 GHz. An inkjet-printed mm-wave bow-tie slot antenna is integrated with the IC die in order to highlight the highly versatile nature of this 3D interconnect technology for integration with emerging SoP technology.

This paper presents a novel architecture of inkjet-printed passive UHF RFID based sensor tag for wireless gas (CO2) sensing. An RFID tag made with Silver (Ag) ink is loaded with carbon nanotube (CNT) ink for sensing purpose. A switch in its structure provides two modes of operation, sensor ON (SON) mode and sensor OFF (SOFF) mode. In SON mode, the sensor tag modifies its backscatter properties in the presence of gas. In SOFF mode, the realized gain of the sensor tag remains constant, which provides a reference measurement. The difference in threshold power between SON mode and SOFF mode is used as the sensing parameter. Fabricated sensor tags, when exposed to CO2, show a threshold power variation of up to 2dB, with a read range of about 4m at 915MHz.

The paper presents an antenna transducer prototype at 915MHz for a batteryless ultra high frequency (UHF) radio frequency identification (RFID) transponder (tag) sensor add-on. By using low cost and low maintenance batteryless RFID sensor tags in a home environment, a low cost internet of things (IoT) infrastructure can be provided. The batteryless or rather passive UHF RFID sensor tag is realized by using the tag antenna as the sensing device. The prototyped antenna transducer allows to detect three specific water filling levels in a can to sense for example the filling level of a coffee machine in a smart home environment. The transducer prototype provides a high efficiency of 92% and thus guarantees for the first time a reliable and stable power supply to the passive RFID tag chip at each sensing state.

Despite the abundance of localization applications, the tracking devices have never been truly realized in E-textiles. Unobtrusive and flexible integration of tracking devices with clothes is difficult to achieve with standard PCB-based devices. An attractive option would be direct printing of circuit layout on the textile itself, negating the use of hard PCB materials. In this paper, an interface layer is first printed on the textile to facilitate the printing of a complete localization circuit and antenna for the first time. The tracking device utilizes WiFi to determine the wearer’s position and can display this information on any internet-enabled device, such as smart phone. The device is small enough (55 mm x 45 mm) and lightweight (22g with 500 mAh battery) for people to comfortably wear it. The device operates at 2.4GHz with communication range of up to 55 meters, and localization accuracy of up to 8 meters

This paper presents a wearable RF energy harvesting device in the form factor of a necklace, suitable for powering smart jewelry. The design includes a U-shaped dipole antenna, matching network, RF-DC converter, and DC-DC converter. The system converts a 915 MHz RF signal into a constant 3.1 V DC output with an output power up to 106.5 uW at -6 dBm input power, sufficient to power a fitness monitor pendant in stand-by mode. An experimental comparison between multistage Cockcroft-Walton and Dickson RF-DC converters shows that the Dickson topology offers higher efficiency at high input power, whereas the Cockcroft-Walton converter performs better for low input power. The necklace can produce up to 23.2 uW at 10.4m from a commercial isotropic 3 W RF power transmitter.

Unmanned Aerial Vehicle (UAV) platforms are ideal for remote life sensing applications including military, humanitarian and post-disaster search and rescue operations. Doppler radar sensors can remotely detect human vital signs to assess triage but any sensor motion will corrupt the signal. The vital signs signal fidelity can be improved by using the Received Signal Strength Indicator (RSSI) and Radio Frequency Direction of Arrival (DOA) to compensate for the platform motion and drift via a closed loop control system that modulates the UAV Electronic Speed Controller (ESC). The measured average RF DOA error was 0.004 degrees. Motion compensation with an ultrasonic sensor was also successfully demonstrated.