The design of a 61.44 GHz integrated Phase-locked loop (PLL) on a 180 GHz BiCMOS technology is presented. The PLL was optimized for a very fast settling time of 4 µs as required by the system specifications. Because the receiver is using a carrier recovery circuit that can follow the slow changes of the carrier such as phase noise, the sensitivity of the bit error rate to phase noise at the receiver end is very low. As a result, to achieve the required dynamic behavior, the phase noise performance could be sacrificed and the loop bandwidth was increased until the needed settling time was achieved, while taking the suppression of the reference spurs into consideration. Capacitor multiplication was used to enable the integration of the loop filter (LF) on chip and the effect of the capacitor multiplier on the total PLL phase noise performance was quantified and evaluated. In addition, a very close matching between the measured and simulated phase noise of the system was achieved. The PLL consumes a power of 200 mW from 2 and 3 V supply voltages, while delivering a differential output power of −7 dBm, sufficient to drive the following I/Q modulator without additional amplification.

This paper reports on digital transmitter architecture for the 450 MHz band using an envelope delta-sigma modulator realized in CMOS and a voltage-mode class-S (VMCS) power amplifier (PA) based on GaN monolithic microwave integrated circuits (MMICs). The class-S PA is characterized for narrowband single-tone signals and a single- as well as a four-carrier downlink wideband code division multiple access (WCDMA) signal with a peak-to-average power ratio of 7.5 dB. Using single-tone excitation the PA shows a maximum drain efficiency of 86% and a peak output power of 4.4 W. At 6 and 10 dB back-off, 59 and 36% efficiency are achieved, respectively. With the single- and four-carrier WCDMA input signals maximum drain efficiencies of 64 and 53% are reached, respectively, and peak output power is 0.7 W. The adjacent channel leakage ratio shows values of about −34 dBc (5 MHz) and −38 dBc (10 MHz) for single-carrier WCDMA excitation. This is the first complete VMCS PA chain characterized with standard communication signals.

Millimeter-wave reconfigurable bandpass filters with the ability to operate between 60 GHz and the E-band, capable of providing good channel isolation, are presented. A fully integrated filter with all reconfigurable elements embedded for compactness and a switchable filter that uses radio frequency micro-electro-mechanical system (RF MEMS) single-pole double-throw switches are designed. A new method that increases fractional bandwidths is introduced. It uses inductively coupled inverters without requiring their tuning. New circuit models are offered for inverters, reconfigurable resonators, and reconfigurable bandstop stubs. Our compact bandpass filter achieved a footprint of only 4.75 mm × 3.75 mm. Measurements for our filters show good agreement with the results of simulations.

This paper reports on the potential of RF-MEMS technology based on aluminum nitride capacitive dielectric and nickel-suspended membranes to provide RF circuit functions in reconfigurable front-end radios. The RF performance of capacitive switches, distributed MEMS transmission lines (DMTLs) phase shifters for beam steering and tunable filters, including center frequency and bandwidth tuning of bandpass and band-stop filters are presented. Detailed characterization based on S-parameter data demonstrates very promising figures of merit of all fabricated demonstrators from 5 to 40 GHz.

We propose simple designs of compact patch antennas with bandwidth enhancement. Firstly, an inverted “L” strip is loaded onto the corner of one radiating patch edge to create an additional resonant mode which can be combined with that one of the conventional patch to enhance the operating bandwidth. Secondly, the “L” strip is replaced by inverted “T” strip to improve further the bandwidth by creating two adjustable resonant modes. The two proposed patch antennas have the particularity of enhancing the bandwidth significantly without increasing their profile and their overall sizes. Two antenna prototypes are fabricated and tested. Measurements reveal that the patch antenna loaded with “L” strip has stable radiation characteristics with 5.2 times enhancement in the relative bandwidth compared with a conventional patch antenna. The antenna loaded with inverted “T” strip has wider bandwidth (6.25 times wider than the conventional patch) and covers the operating band 5.07–5.89 GHz (15%) with measured peak gain and peak efficiency of 6.25 dBi and 78%, respectively. The proposed antennas are easy to fabricate, have a low-profile, and exhibit good performances which make them good candidates to use in real wireless applications.

This article presents a novel miniaturized (0.105λ0 × 0.105λ0) flexible complementary frequency selective surfaces (CFSS) structure with sharp band edge selectivity and very high angular stability. To explore two diverse applications as a passband and stopband filter, a novel complementary convoluted square loop (CCSL) type structure has been designed and investigated on ultrathin dielectric material of thickness 0.0023λ0. The second-order wide controllable passband with fractional bandwidth of 19.23% (−3 dB) and remarkably wide stopband of 64.7% (−10 dB) and 54.8% (−20 dB) respectively have been achieved by using a cascaded resonating structure which is composed of asymmetrical meandered CCSL array, arranged on two ultrathin dielectric layers with air foam separation. This particular format would lead to sharp band edge selectivity with steep roll-off (72.43 dB/GHz) and an excellent passband selectivity factor (0.731). An equivalent lumped LC circuit in conjunction with the transmission line model has also been adopted to comprehend the physical mechanism of the proposed single layer and double layer structures. Further, better passband and stopband angular stability at an oblique incident angle of 45° and the bending characteristics have also been investigated thoroughly for the proposed flexible CFSS to check their employability in different conformal structures with WiMAX passband and WLAN stopband application.

The development of a millimeter-wave transparent antenna integrated inside a headlamp for automotive radar application is presented. The antenna consists of two radiating elements: the primary and secondary ones. The primary antenna is the one that is fabricated on RF PCB material (e.g., patch, slot, sectoral horn) and connected directly to the transceiver chip, while the secondary antenna is made of optically transparent materials such as glass, but with a optical transparent electrically conductive coating, well known as transparent conductive oxide (TCO). This antenna is realized as a planar offset reflector to collimate and shape the incoming wave from the primary antenna. This reflector is designed based on the Fresnel theory and the reflectarray concept. The division of the primary and secondary antenna enables the placement of the radar module (that contains the primary antenna) at the base of the headlamp, and therefore it is concealed from the surroundings and hidden from the optical path of the light. The secondary antenna is inserted in the space between the headlamp cover and the light unit. The main challenge here is to provide a maximum on transparency in the visible range of the spectrum with a specially designed and laser-based generated microstructure for the resonant reflection of the radar wavelength. An antenna demonstrator has been fabricated, and together with the headlamp cover, the radiation pattern and realized gain are measured. We reported here the measurement results for several reflector designs and concluded that the headlamp cover gives minimal influence on the antenna performance.

Accurately and efficiently modeling the drain-lag effects is crucial in nonlinear large-signal modeling for Gallium Nitride high electron mobility transistors. In this paper, a simplified yet accurate drain-lag model based on an industry standard large-signal model, i.e., the Chalmers (Angelov) model, extracted by means of pulsed S-parameter measurements, is presented. Instead of a complex nonlinear drain-lag description, only four constant parameters of the proposed drain-lag model need to be determined to accurately describe the large impacts of the drain-lag effects, e.g., drain-source current slump, typical kink observed in pulsed IV curves, and degradation of the output power. The extraction procedure of the parameters is based on pulsed S-parameter measurements, which allow to freeze traps and isolate the trapping effects from self-heating. It is also shown that the model can very accurately predict the load pull performance over a wide range of drain bias voltages. Finally, the large-signal network analyzer measurements at low frequency are used to further verify the proposed drain-lag model in the prediction of the output current in time domain under large-signal condition.

Near sea surface radio frequency (RF) refraction is four dimensional (4D) and can significantly impact the performance of radar systems. The refractivity field is dictated by the vertical thermodynamic structure of the constantly evolving marine atmospheric boundary layer (MABL). Logistical and budgetary restraints on meteorological measurements over water to capture the spatio-temporal structure of refractivity fields influencing radar performance have limited the knowledge of how and why radar performance is azimuth, range, and time dependent. Rapidly increasing computer processing speeds and decreasing memory capacity costs have supported the horizontal and vertical resolution requirements for mesoscale numerical weather prediction (NWP) models to resolve the thermodynamic structure in the MABL. Once modeled, refractivity structure is easily calculated from the thermodynamic structure. Mesoscale NWP models coupled with modern parabolic equation radar performance models can support the prediction of 4D radar performance in challenging non-homogeneous, near surface refractivity fields at the time and location of the modeler's choice. The NWP modeling presented in this paper demonstrates how large-scale offshore flow of warm and dry air over colder seas produces strong near surface RF trapping. Large land-sea temperature differences can produce near shore sea breezes and surface-based ducts. This paper describes modeled radar performance in such a complex ducting structure over the Persian Gulf during large-scale northwest atmospheric flow. The refractivity field was resolved by the Coupled Ocean/ Atmosphere Mesoscale Prediction System (COAMPS® is a registered trademark of the Naval Research Laboratory) and the notional radar performance was modeled by the advanced refractive effects prediction system (AREPS). The results indicate strong spatial and wavelength-dependent enhancements and degradations in radar performance relative to a standard atmosphere.

In this paper, a method for design and optimization of folded reflect-array antennas is proposed based on particleswarm optimization (PSO). In addition to such a powerful optimization algorithm, two further requirements have to be fulfilled. The first one is a good and fast algorithm for the exact prognosis of the far-field radiation diagram, resulting from a specific element configuration on the reflector. Additionally, a good choice of the fitness function for the evaluation of the resulting radiation diagrams is necessary. In both, reflect-array-related aspects such as phase truncation, reflection losses, and cell discontinuities have to be considered. Antenna optimization based on this technique is presented in this paper at the example of two 77 GHz folded reflect-array antennas. The efficiency of this approach is demonstrated with these examples, and the results are verified by measurement, showing an excellent agreement with the specifications of the diagram masks. The implemented tool, including a realistic antenna diagram preview, allows the investigation of the design parameters’ influence on the antenna performance, such as illumination amplitude, high substrate losses, and phase truncation.

In this paper, a completely reconfigurable comb-line bandpass filter is presented. Due to the modularity, different standard coupling matrix topologies like the folded form, cascaded triplets, and the cul-de-sac form can be implemented and tested. Circuit-based coupling matrices like the extracted pole topology can easily be realized as well. Different types of input-/output- and cross-couplings can be examined before fabrication of a fixed filter set-up takes place. Furthermore, the proposed filter platform can be used to construct a diplexer. By using different heights of the inner and outer conductor of the coaxial resonators, arbitrary center frequencies in the range between 1 and 4 GHz can be realized. Various types of input couplings are available and proposed here to achieve bandwidths between 10 and 110 MHz. A variety of cross-coupling apertures able to realize transmission zeros are presented as well.

Antennas installed on aircraft are used for communications as well as for various radio navigation systems such as direction finders, distance measuring systems, and altimeters. Generally, these systems use blade antennas operating in the L frequency band. Recently, inverted-hat empty section monopole antennas have been found to be good candidates for such uses. In this study, we propose a new design of inverted-hat antenna based on optimized elliptical shapes and a filled cavity. The dielectric material added in the cavity helps to improve the monopole stability and to adjust the resonant frequency of the antenna. The proposed antenna meets the distance measuring equipment requirements, namely an omnidirectional radiation pattern in the H-plane, a vertical polarization, a frequency band from 960 MHz to 1.22 GHz, and a gain better than 1 dB. This antenna is entirely made of aluminum in order to obtain a homogeneity with the aluminum fuselage. In addition, the solution proposed brings a better protection against weather conditions. The antenna performance is analyzed on the basis of simulation and measurement results.

The Muscle Analyzer System (MAS) project wants to create a standalone microwave device that can assess the muscle quality, called the MAS device. To achieve that an algorithm that can derive the properties of skin, fat and muscle from the measurements is needed. This paper presents a machine learning algorithm that aims to do precisely that. The algorithm relies on first predicting the skin using the data from the MAS device, then predicting the fat again using the data from the MAS but also the predicted skin value and lastly the muscle is predicted using the microwave data together with the skin and fat predictions. Data have been collected in phantom experiments, materials that mimick the dielectric properties of human tissues. The algorithm is trained to predict the properties of said phantoms. The results show that the prediction for skin thickness works well, the fat thickness prediction is okay but the muscle prediction struggles. This is partly due to the error from the skin and fat layers are propagated to the muscle layer and partly because the muscle layer is farthest away from the sensor, which makes getting information from that layer harder.

Worldwide adoption of fourth-generation wireless (4G) long-term evolution (LTE) smartphones and the actual transition to fifth-generation wireless(5G) is the main driving engine for semiconductor industry. 5G is expected to reach high data rate speeds (1 Gbps) and low latency (<1 ms). 5G requires more RF bandwidth and therefore an increase in the number of components such as RF switches, acoustic filters, and power amplifiers integrated in few RF front-end modules. Also, there is an increase in the number of RF radio transmitters and receivers operating at the same time. This paper presents new architecture elements for 5G RF front-end modules. Circuit details and measurements are presented to reduce the RF noise, improve the efficiency, and help the coexistence of multiple radio transmitters. These circuits will help extend the 5G applications with radar-like sensing applications, remote medicine, and autonomous driving.

Sub-beam concept is very useful for size reduction of multiple beam phased array antenna (PAA) systems that are applied for high-throughput communication satellites. In this paper, the synthesis procedure for a PAA with multiple sub-beams in two dimensions of the coverage domain is proposed and analyzed. In the design procedure, the interleaved sub-arraying technique has been applied to eliminate the grating lobes. The extremely short angular distance between adjacent sub-beams is challenging. An innovative beam forming network is proposed, which can generate multiple orthogonal sub-beams while keeping the required angular distance between sub-beams. To demonstrate the effectiveness of the design technique, an example considering the requirements derived from conceptual design of a high-throughput communication payload is presented. The array is optimized using the genetic algorithm while taking into account the technical requirements of the antenna. The gain patterns exhibit a 0.4° angular distance between adjacent sub-beams. In addition, the number of sub-arrays and element spacing guarantee the orthogonality of the sub-beams. The calculated carrier to interference ratio in the synthesized array shows that it has acceptable values in each spot. The aperture size reduction in the synthesized array compared to a conventional multiple beam array is more than 36.7%.

To provide short-range super-resolution ultra-wideband (UWB) radar under multi-scattering conditions, a superior wavefront extraction algorithm is proposed in this paper. Conventional correlation-based pulse separation methods based on SAGE, CLEAN or the previously introduced superior dynamic correlation method (DCM) are revised, validated, and compared. In this paper, the DCM is improved significantly by applying the Pauli scattering matrix decomposition onto the radar data. This novel wavefront extraction algorithm is called polarimetric dynamic correlation method (PDCM) and is suitable to resolve several overlapping pulses, which consist of both strong echoes and weak echoes which are masked by the strong ones. The performance of the PDCM and the comparison with alternative algorithms is carried out by a subsequent feature extraction algorithm for visual verification. Experimental validations are performed with two complex test objects, a maximum length sequence radar device (4.5–13.5 GHz) and compact dual-polarized UWB antennas.

In this paper, two compact lumped-element band pass reconstruction filters for digital microwave power amplifiers applications in the 800 MHz band are presented. The filters, based on the trisection and quartet topologies, include cross-couplings which produce transmission zeros for maximum selectivity, and can be designed with practical element values. In contrast to common filter designs the input impedance characteristic is optimized broadband to values different from 50 Ω, as required for proper amplifier operation. Both filters achieve an insertion loss of around 0.8 dB and an equiripple bandwidth of 240 MHz (trisection) and 290 MHz (quartet), respectively, with improved out-of-band suppression. Results show that a considerable improvement in amplifier linearity and efficiency can be obtained with the new proposed filters, as compared with simpler filters traditionally used in power amplifier applications.

A Ka-band carrier generator using phase-locked loop (PLL) frequency synthesizer is presented in this paper. The design uses integer-N PLL chip PE83336 as the important hardware support. The key idea of generating Ka-band frequency signal with low-phase noise is to generate a high-quality X-band frequency signal using PLL frequency synthesizer and employ a frequency multiplier to deliver the high-frequency output at the desired frequency band. Experimental measurements of the frequency synthesizer demonstrate the excellent performance, which is achieved with the Ka-band output with a frequency resolution of 5.7 MHz and phase noise better than −70 dBc/Hz at 1 kHz.

The safe operating area (SOA) of InGaP/GaAs heterojunction bipolar transistors has been studied using two-dimensional Technology Computer-Aided Design (TCAD) tool. Comprehensive physical models, including hydrodynamic transport-based impact ionization and self-heating models were implemented. The simulations for two DC modes (constant Ib and Vb modes) captured all the SOA features observed in measurements and some failure mechanisms were revealed for the first time by TCAD simulations. The simulated results are also in agreement with analytical modeling. The simulation not only gives us insight to the detailed failure mechanisms, but also provides guidance for the design of devices with better ruggedness and improved SOA performances.

A novel radio frequency identification tag antenna is composed of a resonant open-slot exciter and a dipole-type ground radiator. For a conjugate match to the Alien Higgs-4 chip impedance of 8−j149 Ω at 925 MHz, a quarter wavelength open-slot resonator embedded at the center of the dipole-type ground plane (130 × 18 mm2) was investigated and fabricated. Simple size adjustments and various loaded inductor of the open-slot resonator allow for easy control of the tag antenna resistance and inductive reactance, from which the chip impedance requirement can be easily obtained. The read range of the prototype antenna attached on a foam in the free space can reach more than 9 m, which has been tested for a radio frequency identification reader with 4.0-W of effective isotropic radiated power. Measurement data are in good agreement with simulation results.