Modern radar sensors are gaining more and more relevance for several industrial measurement applications. To achieve the required range resolution and measurement accuracy, the use of higher frequencies beyond 100 GHz is beneficiary. A commonly used signal generation concept in fully integrated radar transceivers is to use a fundamental oscillator with subsequent frequency multiplication. Depending on the overall system concept, this type of signal generation suffers from a fundamental feed-through signal which generates false targets in frequency modulated continuous wave operation. Additionally, those unwanted signal components radiated by the sensors might be problematic for legal conformity or electromagnetic (EM) interference compliance. This paper presents a novel concept for frequency filtering dielectric lens antennas, to suppress unwanted signal components at harmonic frequencies based on interference filtering effects. Besides the EM simulations to theoretically prove this concept, multiple prototypes of filtering lens antennas were fabricated by conventional mechanical and additive manufacturing. Using a self-developed, ultra-compact radar sensor, measurements were taken to compare the lens antenna prototypes in terms of filtering performance and how the material characteristics affect the filtering performance. Within these measurements, the successful suppression of false targets caused by fundamental feed-through signals is demonstrated.

In this communication, a compact flower shaped printed antenna for ultra-wideband communication is proposed. The “flower-shaped” structure is capable of transmitting UWB-band signals. The designed antenna exhibits a return loss ranging from 2.3 to 11 GHz with an 8.7 GHz central frequency and has 130% relative bandwidth. The suggested design includes a patch in the shape of a flower with several slots fed by a microstrip line. Multiple slots have been designed for better resonances at lower modes. The antenna is constructed with an FR4 substrate, and a 50 Ω A-type connector feeds it. The optimum dimensions of the designed antenna are 12 × 16 × 1.6 cubic-millimeters and 0.092λ × .12λ × 0.012λ in lambda. The proposed structure also demonstrates stable radiation patterns across the operating bandwidth. The proposed radiator has a high gain of 2.67 dBi, and an efficiency of 85%. It is compact, lightweight, and easy to make. Therefore, it can be used for UWB applications.

Though compact polarimetric approaches have been developed and applied in space and geo researching systems they have not been taken into consideration in automotive applications, yet. A sensor system has been designed to conduct polarimetric measurements in the 77 GHz frequency band, which is permitted for automotive usage. This system is able to transceive linearly as well as circularly polarized electromagnetic continuous waves. Depending on the case of application, the frequency output can be set statically or modulated over time within adjustable parameters. Hence, a variety of compact polarimetric modes can be performed and compared with full polarimetric approaches. Two compact polarimetric modes, dual-circular polarimetric mode, and circular-transmit-linear-receive, will be introduced and applied in this contribution. Their operability in this frequency range will be investigated after the microstrip antennas as well as the beam focusing dielectrical lense are characterized. Finally, results of a realistical measurement set-up will confirm the practicability of compact polarimetric approaches for double bounce recognition.

Design and fabrication of a microstrip feedline-based Vivaldi antenna in the frequency range of 6.0–8.0 GHz have been presented. The Vivaldi antenna is a planar antenna, fabricated at the microstrip feedline by having an exponentially tapered slot profile on it. An optimized computer-aided design has been developed and simulated for the desired radiation parameters like voltage standing wave ratio, bandwidth, directionality, beam-width, etc. The optimized design has been fabricated and tested. Wherever the results are not found as desired; problem has been comprehensively investigated and analyzed. This is found associated with a discontinuity at feed line, fabrication tolerance constraints and parasitic capacitance at the edges or the bent of the microstrip feedline which introduce the parasitic reactance in antenna design. Here, the presented work explores a generalized theoretical procedure for the compensation of associated problem by incorporating the reactive patch on the feedline. The developed theory is applied in fabrication and tested for the desired results.

For a fast scan-phase satellite radio antenna diversity system a noise correction method is presented for a significant improvement of audio availability at low signal-to-noise ratio (SNR) conditions. An error analysis of the level and phase detection within the diversity system in the presence of noise leads to a correction method based on a priori knowledge of the system's noise floor. This method is described and applied in a hardware example of a satellite digital audio radio services antenna diversity circuit for fast fading conditions. Test drives, which have been performed in real fading scenarios, are described and results are analyzed statistically. Simulations of the scan-phase antenna diversity system show higher signal amplitudes and availabilities. Measurement results of dislocated antennas as well as of a diversity antenna set on a single mounting position are presented. A comparison of a diversity system with noise correction, the same system without noise correction, and a single antenna system with each other is performed. Using this new method in fast multipath fading driving scenarios underneath dense foliage with a low SNR of the antenna signals, a reduction in audio mute time by one order of magnitude compared with single antenna systems is achieved with the diversity system.

The Misell algorithm is one of the most widely used phase retrieval holography methods for large reflector antennas to measure surface deformation. However, it usually locks in a local minimum because it heads downhill from an initial estimation without any consideration whether it heads for a global minimum or not. The core problem of the Misell algorithm is to find an initial estimation near the global minimum to avoid local stagnation. To cope with the problem, we construct a hybrid Misell algorithm, named modified very fast simulated annealing (MVFSA)-Misell algorithm, to search for the global minimum with a high efficiency. The algorithm is based on the combination of the MVFSA algorithm and Misell algorithm. Firstly, the MVFSA is utilized to obtain a rough position near the global minimum in limited steps. Then, the Misell algorithm starts from the rough position to converge to the global minimum with high speed and accuracy. The convergence characteristic of the proposed algorithm was discussed in detail through digital simulation. Simulation results show that the algorithm can reach global minimum in a very short time. Unlike the traditional Misell algorithm, the hybrid algorithm is not influenced by initial phase estimation.

For a fully 360° detection around a vehicle, novel automotive radar system concepts consist of up to eight radar sensors. The existing sensor-mounting areas, such as front grill or bumper corners would no longer be sufficient. Therefore, additional mounting positions such as B-pillars and side skirts have to be considered, where the radar can observe the side area of the vehicle. However, these new mounting positions usually offer significantly less space, than the established mounting areas. The solution is, to build separate miniature radar frontends that can be placed all over the vehicle and are connected to one central signal processing and power supply unit. Investigations for a miniature radar frontend have been done, based on RF360 low loss non-shrinkage low-temperature cofired ceramic (LTCC) substrate. For the automotive radar band (76–81 GHz), an array antenna has been simulated, manufactured, and the radiation pattern has been measured. A first sensor with a miniature radar frontend based on an LTCC multilayer has been designed and manufactured.

In this paper, the first reported waterproof inkjet-printed dual-band monopole antenna on the flexible organic paper substrate is presented. The antenna, which operates at 900 MHz and 2.4 GHz, is inkjet-printed on commercially available photopaper using conductive silver nano-particle ink. To protect it from ambient humidity, a 1 µm thick Parylene-C layer was deposited on top of the antenna. To verify its waterproof capability, the Parylene-C coated antennas were submerged in distilled water for 48 days, and no significant performance degradation was observed in its performance.

This paper proposes, a high gain, Fabry Perot cavity antenna with coplanar waveguide (CPW) fed ultra wide band (UWB) radiating element. The proposed antenna has flat edge arrow shape-based radiating element, which act as a main radiating element and responsible for UWB radiation. This UWB microstrip antenna is parasitically coupled with an array of square parasitic patches (PPs), which act as partially reflective surface. The square patches are fabricated at the bottom of inexpensive FR4 substrate and suspended in the air with the help of dielectric rods at 1.5λ0 height. High gain is obtained by resonating PPs at near close frequencies of 3.8–8.8 GHz UWB, where partially reflective surface gives almost positive reflection phase gradients. Two laboratory prototypes of antenna, one with and another without partially reflective surface are fabricated and tested. Details of the proposed antenna design and role of partially reflective surface in gain enhancement of planar CPW fed UWB antenna are described, and typical experimental results are presented and discussed.

In this work, a simple and efficient approach to design a microstrip diplexer is proposed. It is based on the combination of two compact Square Open Loop Resonator band pass filters. These filters are designed for Radio Frequency Identification application at 2.45 GHz frequency. Using the Chebychev approximation, the two filters and diplexer are designed, simulated, fabricated, and measured. The results show that the diplexer presents a high selectivity, a good insertion loss and high isolation (>40 dB) with the compact size. The diplexer also shows a good performance when associated with the patch antenna operating at 2.45 GHz.

A dedicated hyperthermia (HT) system was designed for tumors in intact breast extending beyond the heating depth of our superficial 434 MHz antennas, consisting of a treatment bed fitted with a 50 cm × 40 cm × 16 cm temperature controlled open water bolus. The patient lies in prone position with the breast immersed in the water positioned in front of a 34 cm × 20 cm 70 MHz waveguide operating in the TE10 mode. E-field patterns were measured in a tissue-mimicking phantom. HT was applied once a week with the 70 MHz applicator for six patients treated with thermoradiotherapy for deep lesions of recurrent breast cancer or melanoma. Two 14-sensor thermocouple thermometry probes were placed in catheters to monitor the invasive temperature. Results: Phantom measurements showed sufficient penetration depth up to 10 cm depth. The combination of 300–900 W antenna power and a water temperature of 42°C was well tolerated for the entire session of 1 h and resulted in good tumor temperatures with T90 = 39.8°C, T50 = 41.1°C, and T10 = 42.2°C. No toxicity or complaints were associated with the heating. A water mattress and other measures were needed to assure a comfortable position throughout the treatment. Conclusion: the 70 MHz breast applicator system performed well and tumor temperatures were good.

In this paper, a vase-shaped monopole antenna is presented for dual band notch (WiMAX IEEE802.16 3.30–3.80 GHz with C-band 3.80–4.20 GHz and WLAN IEEE802.11a/h/j/n 5.15–5.35 GHz, 5.25–5.35 GHz, 5.47–5.725 GHz, 5.725–5.825 GHz) UWB and other wireless services (close range radar: 8–12 GHz in X-band & satellite communication: 12–18 GHz in Ku-band). Measured VSWR of proposed antenna shows a high band-rejection for WiMAX along with C-band with VSWR = 25.33 at 3.77 GHz and WLAN with VSWR = 6.0 at 5.64 GHz is achieved by cutting two C-shaped slots on the radiating patch. Designed antenna covers a wide usable fractional bandwidth 160% (2.58–20.39 GHz). Furthermore, the measured gain of antenna is relatively stable across the impedance bandwidth except band-notched. In addition, antenna offers omni-directional pattern, reasonably small 20 × 20 × 0.787 mm3 and easy to construct structure.

In this study, a dual-layered polarization and frequency reconfigurable microstrip antenna is proposed based on sequential mechanical axial rotation of the circular metal radiator. The antenna can be reconfigured among three different polarized modes, including the linear polarization (LP), left-handed circular polarization and right-handed circular polarization in the band from 4.68 to 4.80 GHz (2.53%). The resonance frequency of the proposed antenna with the same LP mode could also be tuned in the range from 4.70 to 5.03 GHz by mechanical rotation of the breach-truncated circular metal radiator as well as the circular substrate. Furthermore, the polarization characteristic and frequency can be reconfigured, respectively, as the circular radiator is taken an axial rotation with an angle of 360°. The presented antenna in the four different states has been numerically simulated and fabricated for the experimental measurement, the investigated characteristics includes the port reflection coefficient, axial ratio, radiation pattern, gain, and the radiation efficiency. The simulated and test results agreed well with each other. This antenna enriches the novel mechanical reconfigurable method except for the popular electrical approach.

Owing to dynamic nature of vehicular environments, it becomes essential to achieve effective communication via vehicle-to-vehicle and infrastructure-to-vehicle. This leads to the need for an antenna system that supports multiple frequency bands, high gain, broadside radiation pattern, and circular polarization. We propose single-arm penta-band-based spiral antenna with dimensions of 51 × 35 × 1.574 mm3 resonating at navigational wireless frequencies 1.2 GHz for IRNSS and 1.5 GHz for GPS; wireless communication frequencies 2.45 and 3.3 GHz and dedicated short range communication frequency 5.8 GHz. Linear taper feed has been introduced to achieve good impedance matching and the outer edge feed of the spiral on the same plane helps to achieve circular polarization. The measurement result proves the betterment in impedance of the spiral antenna that varies from 50 –55 Ω across the desired operating frequencies.

The development of compact radio frequency identification (RFID) tag is the key requirement for wireless tracking of precious small size goods/packages in transport. A design of compact meander line tag antenna having inductive coupling feed is presented for RFID system operating at ultra high frequency band of 865–867 MHz. The size of the proposed tag antenna is 43 mm × 10 mm, and is designed using Higgs 4 IC chip (made Alien Technology, USA) having impedance of 20.55 − j191.45 Ω at centre frequency 866 MHz. The antenna characteristics such as impedance, radiation pattern, bandwidth, and effect of ground on gain and tag size are analyzed and found to closely match with the simulated values. The observed value of reading range varies from 87.5 to 35 cms depending on mounting on non-metal and metal packages, respectively.

A novel antenna-harvester co-design paradigm is presented for wireless nodes operating in an Internet of Things context. The strategy leads to compact and highly-integrated units, which are able to set up a reliable and energy-efficient wireless communication link, and to simultaneously harvest energy from up to three different sources, including thermal body energy, solar, and artificial light. The core of the unit consists of a substrate-integrated-waveguide (SIW) antenna. Its surface serves as a platform for the flexible energy-harvesting hardware, which also comprises the power management system. To demonstrate the approach, two different SIW cavity-backed slot antennas and a novel compact dual linearly polarized SIW antenna are presented. These topologies facilitate the integration of additional hardware without degrading performance. In the meantime, they enable comfortable integration into garments or unobtrusive embedding into floors or walls. Measurements on prototypes validate the integration procedure by verifying that the integrated hardware has a negligible influence on the performance of all discussed SIW antennas. Finally, measurements in four well-chosen indoor scenarios demonstrate that a hybrid energy-harvesting approach is necessary to obtain a more continuous flow and a higher amount of scavenged energy, leading to a higher system autonomy and/or reduced battery size.

The purpose of this paper is twofold. It first describes how Microwaves were progressively organized by Professional Engineering Institutions in Europe in the years 1960–2000, essentially through individual efforts over many years. The first formal Microwave event organized in Europe was the European Microwave Conference in London, 1969, opening a series that continues as the European Microwave Week. It then shows that, over the same period of time, the Institute of Radio Engineers (IRE), USA, which merged in 1963 with the American Institute of Electrical Engineers, USA, to form the Institute of Electrical and Electronic Engineers (IEEE), also became stronger in Europe. European IRE members developed the structure of the IRE in Western Europe, with a first Regional meeting in Geneva, 1962. The paper illustrates the development of both Microwave Engineering and IRE-IEEE in Europe in the period of time considered, thanks to the commitment of European individuals, some of whom have been active on both counts.

In this paper, a gain-increased method of cavity-backed slot antennas based on excitation of high-order substrate-integrated waveguide cavity resonance has been proposed. To this end, the metallic posts are introduced in a main cavity to excite the cavity's TM220 mode. Then the properties of the modified cavity's TM220 mode are used to feed an array of 2 × 2 slot antenna. Moreover, to acquire insight of modified cavity's field distribution, a comprehensive modal study was performed on the modified cavity to fully understand the effects of the dividing walls on the cavity's field distribution. Also, compared with HFSS, the modal solution that is proposed in this paper provide a considerable time and storage saving. To validate the simulated results, two types of the proposed antenna forming two different polarizations (horizontal and vertical) are analyzed, simulated, and fabricated. The proposed antennas exhibit relatively gain of 8.2 dBi at resonant frequency and high front-to-back ratio. In addition, the gain-enhanced method proposed in the present paper can be extended for using even higher-order cavity resonances, such as TM440, TM660 etc., if higher gain is desirable. The proposed antennas are suitable for using in many wireless communication systems and some radar systems.

The design principles and radiation performances of Mikaelian lens antennas are presented. The ways to manufacture gradient index lenses are briefly reviewed. An innovative technique based on the variation of the foam density is described and applied to the Mikaelian lenses. This yields low cost and lightweight gradient index lenses. The focusing properties of Mikaelian lenses are compared numerically to Luneburg lenses. A foam-based planar Mikaelian lens antenna is manufactured and its radiation performances are characterized at 60 GHz. With its flat shape in contact to the primary source, the cylindrical Mikaelian lens turns out to be, for focusing purposes, an interesting alternative to the well-known Luneburg lens.