Compact surface acoustic wave (SAW) resonator based multi-band bandpass filters (BPFs) with quasi-elliptic transfer functions are reported. They are based on multi-resonant acoustic wave lumped resonator (AWLR) stages that are shaped by multiple one-port type acoustic wave resonators (AWRs) and one lumped-element inductor. The concept can be scaled to transfer functions with: i) a high number of passbands by readily increasing the number of the AWRs in the multi-resonant stage and ii) a higher order by cascading AWLRs using impedance inverters. As such, for N in-series cascaded multi-resonant stages, each comprising K AWRs, K passbands with enhanced fractional bandwidth (FBW) can be created, and the overall transfer function will have $K\bullet(N)$-poles and $N\bullet(K+1)$-transmission zeros (TZs). The operating principles of the multi-band AWLR concept are provided through detailed design examples. For proof-of-concept demonstration purposes, two-stage dual-band (i.e. $N=K=2$) and triple-band ((i.e. $N=2$ and $K=3$) BPF prototypes were designed, manufactured and characterized. They exhibit i) two passbands with $f_{cen1,2}=1033.4$ and 1039.9MHz, FBWs $\gt0.78k_{t}{}^{2}$ and $Q_{\text{effS}}\gt6200$ ii) three passbands with $f_{cen1,2,3}=1029.8,1033.4$ and $1039.9\mathrm{MHz},\mathrm{FBWs}\gt0.48k_{t}^{2}$ and $Q_{effS}\gt5400.\ (k_{t}{}^{2}$ is the AWR’s electromechanical coupling coefficient)
In this paper, we present a hemispherical Fabry-Pérot open cavity resonator based measurement technique to estimate the relative permittivity of dielectric materials. The open cavity is realized by combining a spherical and a planar mirror, suitable for the characterization of both solid and fluid materials in the frequency range from 25 GHz to 42 GHz. The planar mirror is surrounded by a 0.5 mm high metal wall which allows the reflector to be filled with the liquid material to characterize. The measurement method is based on the Gaussian beam theory, which allows extracting the dielectric properties of the material by analyzing the resonant frequency shift of the fundamental mode from, in this case, the reflection coefficient only. This is made possible thanks to the optimized shape of the coupling aperture.
This paper presents a detailed RF design methodology for quasi-elliptic bandpass filter (BPF) with quasi-input reflectionless behaviour in both their passband and stopband regions. The proposed input reflectionless BPF consists of microstrip coupled lines and transmission lines, comprising three sections: a BPF, a transmission zero (TZ) and an input matching sections. A quasi-elliptic transfer function is achieved by generating TZs at lower and upper sides of passband without affecting the passband response or input reflectionless behaviour. The TZs can be located close to the passband for achieving sharper power absorption ratio profiles within the stopband-to-passband transitions. The theoretical foundation and design methodology of the proposed quasi-elliptic input reflectionless BPF are described. To validate the proof-of-concept, a prototype was manufactured and measured at center frequency of 3.5 GHz. The measured results are fair agreement with the EM simulations and theoretically predicated results.
This paper reports for the first time the use of 100VGaN on SiC HEMT devices in a distributed amplifier, and the highest power and efficiency yet achieved is reported. Over 0.5 – 1.5 GHz the power and efficiency are SOW and 50% minimum with typically 90W over most of the band.
This work proposes a small dual-band (2.4 GHz and 4.89 GHz bands) 3D beamforming Multiple-Input Multiple-Output (MIMO) antenna for emerging size-constrained Internet of Things (IoT) applications. The performance is realized via digital beamforming in a structure sized only 51.5 mm in diameter (smaller than half wavelength at 2.4 GHz). At the 2.4 GHz band, the antenna realizes an isolation >30 dB, and the Envelope Correlation Coefficient (ECC) is <0.0003), with a bi-directional beamforming capability in the azimuth plane, and unidirectional beamforming across the elevation plane. At the 4.89 GHz band, the isolation is >19 dB, and the ECC<0.0047, while unidirectional beamforming is achieved in both the azimuth and elevation planes.
This paper presents a dual-band Schiffman type phase shifter with large frequency ratio and wide bandwidths. The proposed phase shifter employs three cascaded Symmetric Stepped Impedance Transmission Lines (SSITLs), as the reference line, and one Symmetric Stepped Impedance Parallel Coupled Line (SSIPCL), as the phase adjusting line. Detailed design theory is presented and validated with practical design of a prototype 90° dual-band phase shifter, working at 2 GHz and 11 GHz. Simulation and measured results demonstrate that equal absolute bandwidths of 1.2 GHz are obtained at two design frequency bands, with phase error of ± 4.5° and insertion losses of less than 2 dB.
5G low-earth orbit (LEO) satellite communication plays a crucial role in enhancing the reliability and coverage of wireless connectivity for automated and connected driving. Compactness of user equipment antennas presents a key requirement for automotive mass-market applications offering non-terrestrial connectivity in addition to terrestrial mobile communications. Latest studies reveal the potential for moderate-gain antenna terminals for such applications. We present a circularly polarized 4$\times$ 4 patch antenna array operating at a center frequency of 2S GHz in the 5G new-radio band n257 suitable for LEO satellite communications. The antenna is feasible for integration into the rear spoiler of a car, roof-top shark-fin antenna, or other plastic-covered antenna mounting locations. The embedded array offers 12 dBi measured realized gain and 4 GHz of -10 dB impedance bandwidth. It offers a 3-dB axial-ratio bandwidth of 900 MHz, demonstrating its circular polarization purity along the broadside direction. Realistic link budget calculations predict an uplink data rate of 6 Mbit/s, promising for various automotive mobility applications.
Gallium nitride (GaN) is a promising semiconductor for RF and high-power applications. However, its large-scale industrialization is hindered by several challenges, primarily the lack of cost-effective, high-performance handle substrates. Sapphire and SiC present high performances, but their use in electronic applications is limited due to their high cost. GaN-on-Si substrates are more affordable but suffer from high substrate-induced RF losses. We introduce an innovative method to mitigate the substrate losses. Porous silicon is known for decades for its high RF performance, but its integration is challenging. We performed porosification of the handle silicon substrate after the fabrication of the RF devices, from the backside, preserving the high quality of the GaN layers and the low cost of GaN-on-Si, while boosting the RF performances. We achieved harmonics H2 =-140 dBm at Pout=15 dBm, RF losses under 0.1 dB/mm at 5 GHz, and an effective resistivity higher than 8 kΩ·cm at 5 GHz.
A phase variation sensor is designed in this paper for dielectric constant measurements of solid dielectrics. The sensor is designed using a coplanar waveguide (CPW) transmission line terminated with a semi-lumped LC resonator. The inductance (L) of the resonator is made of a thin meandered wire, whereas the capacitance is realized as the edge capacitance between a rectangular patch and ground metallization. By placing dielectric slabs with different permittivities on top of capacitive patch, phase of the reflection coefficient $(S_{11})$ is modified, from which the dielectric constant of the material-under-test (MUT) is identified. A circuit-based analytical design procedure is developed for the sensor to optimize the sensing performance for an arbitrary operation frequency and dielectric constant range of the material-under-test (MUT). The design procedure is validated through EM and circuit model simulation as well as the measurement of a fabricated sensor prototype.
In this paper, a preliminary study on the development of a monoband flexible rectenna, using bendable PDMS substrate, is proposed for energy harvesting purposes and WBAN applications. First demonstration of a lx3 highly directional artificial magnetic conductor (AMC) backed wearable dipole antenna is presented. A 200 MHz impedance bandwidth and a gain of over 5.01 dBi, are obtained. It maintains a compact electrical dimension and increases front-to-back ratio (FBR) to 18.67 dB whilst covering the required wifi band. The combination of the dipole antenna and its AMC network with a 4-stage RF-to-DC converter will then be studied.
In modern complementary metal-oxide semiconductor (CMOS) process, the quality of the transmission line is very crucial to the integrated circuit (IC) design. However, with the continuous scaling of the advanced CMOS node, the compact back-end-of-line (BEOL) drastically influence the performance of all passive circuits, which cannot be completely overcome due to the physical limit. After a comprehensive comparison with the various transmission lines from the state-of the-art, three optimum transmission lines (stripline, microstrip, and coplanar waveguides) based on GlobalFoundries (GF)22FDX ® are designed and measured. Then, these proposed transmission lines are benchmarked with silicon-filled waveguide to evaluate the potential of the later when moving to the sub-mmWave domain. It shows that the low loss (0.25, 0.46, and 0.6 dB/mm reduction at, respectively, W-band, D-band, and H-band compared with planar TLs) of silicon-filled waveguide opens a new window for the IC designers, especially above 300 GHz.
Due to the large Fraunhofer regions of typical vehicles, especially at higher frequencies for e.g. mobile communications, over-the-air (OTA) measurement of automobiles by using the well-known standard test methods for e.g. the mobile devices are facing critical challenges. Recently, an efficient OTA test method for automobiles has been introduced by 5GAA, where the OTA parameters, e.g. total radiated power (TRP) and total isotropic sensitivity (TIS) are derived from a passive antenna measurement and a limited number of samples of an OTA measurement. This contribution presents an experimental study of the aforementioned efficient OTA test method by comparing the results obtained with the proposed method and the direct far field measurement. In this paper the tests are performed with a vehicle-to-everything (V2X) antenna system on the component level to enable the direct comparison in a far field scenario. However, it should be noted that the efficient OTA method mentioned here is intended to be implemented on automotive tests and is not limited to a particular application. The comparison reveals an excellent agreement on TIS and TRP parameters between the two applied methods.
This paper describes a comparison of measurements to evaluate the effectiveness of different implementations of the Thru-Reflect-Line (TRL) calibration scheme specially developed for S-parameter measurements of terahertz waveguides. A WM-380 (500-750 GHz) vector network analyser (VNA) was calibrated using a 1/4-wave TRL technique utilising novel silicon micromachined standards, and this was benchmarked against a 3/4-wave TRL technique utilising conventionally manufactured standards. The calibrations were applied to measurements of a set of devices with a broad range of characteristics. The results from each scheme were then compared, both directly and against reference values of various kinds. The comparison results give a clear indication of the viability of each calibration scheme and each set of standards for providing accurate measurements at these frequencies.
With the increased interest in Terahertz applications and technologies there is a growing demand of new and improved transmitters. Spectrum analyzers are frequently used to characterise the spectral purity of transmitters. The Terahertz range state-of-the-art electronic spectrum analyzers are limited in terms of frequency coverage and are very expensive. In this article we present an alternative: photonic spectrum analysers based on the optical downconversion of continuous-wave lasers and photoconductive receivers. We compare the performance of two state-of-the-art photoconductive receivers in terms of their spectral roll-off and the displayed average noise level. We conclude with a comparison of the displayed average noise level of the photonic spectrum analyser to that of an electronic system employing extender modules.
This paper discusses an investigation of the local-oscillator (LO) offset in frequency and phase for a W-band communication link, affected by the Doppler effect. To evaluate the carrier frequency offset (CFO), the bit error rate (BER) and the error vector magnitude (EVM) are used as performance metrics. The impact of the CFO on the BER and EVM is analyzed by measuring the BER and EVM of the received signal. The results show that the LO frequency offset has a significant impact on the BER, while the LO phase offset has a negligible effect on system performance. However, both the LO frequency and phase offsets have a significant impact on the EVM. The results of this study can provide a better understanding of the impact of the LO offset on the performance of the W-band satellite communication systems and help improve the tracking and data synchronization methods. The purpose of the paper is to analyze and quantify the effect of the LO offset in homodyne and heterodyne systems and to find the maximum allowed LO offset for correct synchronization, without additional hardware.
This paper presents a novel multi-resonant rectangular waveguide junction suitable for the design of multi-band filters and multiplexers. The junction can have multiple posts to realize up to four resonant modes. The compact designs, enabled by the junction, are achieved by coupling the resonant modes to coaxial cavities, which are much smaller than regular waveguide cavities at the same frequency. To realize multi-band filters, identical junctions are used at the input and the output of the filter to split and recombine the separate frequency channels. In the multiplexer cases, each channel is coupled at its output to a modified junction that has a single resonant post tuned to the proper channel frequency. Three design examples are provided with an experimental proof of concept of a dual-band filter with a five pole filter in each band. The experimental results agree well with simulations verifying the design approach.
Absolute power measurements are crucial for the development of mm-wave sources and for their safe operation. In a French-German research project, we are developing a detector for absolute power measurements for frequencies between 220 and 330 GHz (WR-3 band). This detector is designed to measure the power of the radiation emitted from a suitable horn antenna. We are also developing a method for its calibration at the German National Metrology Institute (PTB). Our work will contribute to the worldwide efforts for the development of mm-wave sources for communication and radar applications.
This paper presents a substrate-integrated waveguide (SIW) on a commercial printed circuit board (PCB) process featuring solid side walls targeting applications in H-band (200 GHz to 330 GHz). The realized structures are evaluated for their manufacturability, dimensional accuracy, and manufacturing tolerances. A transition from 100 μm GSG probe tips to the SIW is designed and used to measure the SIW structures. Different through lengths are used to characterize the performance of the SIW. Due to severe manufacturing deviations and a slant to the side walls, modifications have to be made to the transition, which are investigated. Finally, a slotted waveguide antenna is realized and characterized.
This paper compares different over-the-air (OTA) test methodologies for determining the equivalent isotropically radiated power (EIRP) of vehicular RF systems, mainly focusing on the methods’ potential for dealing with the DUT’s large size compared to the wavelength as well as for accurately accounting for a possible mismatch between the transmitting onboard unit and the antenna. It will be demonstrated that methods relying on the antenna’s far-field pattern provide accurate EIRP patterns while direct OTA measurements carried out in the vehicle’s nearfield differ significantly from the baseline far-field results unless correctional post-processing is employed. Exemplary measurement performed on LTE uplink signals radiated from vehicle’s bumper antenna underline the aforementioned findings.
This communication deals with a technique to passively retrieve the couplings between several antennas. The mutual-impedance of coupled antennas are deduced from field correlations in a reverberation chamber (RC). It is experimentally shown that the impedance matrix between 2 slot antennas or 3 horn antennas are reconstructed with good accuracy whatever the antenna properties. The accuracy is quantified with respect to the distance between the antennas.
