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.

In this paper, the basic quadratic form of the poly-harmonic distortion model is first presented and this is then extended to provide a new, modified quadratic poly-harmonic distortion model. Comparisons between the X-parameter model, the basic quadratic poly-harmonic distortion model, and the modified version are provided. Both simulation and experimental test results show that the new modified model provides significant improvements in accuracy, not only for the fundamental frequency, but also for DC. Work on the optimization of the model is also presented, providing further improvements in both the model extraction time and the file size.

This paper presents and discusses two possible real-time digital predistortion (DPD) architectures suitable for envelope tracking (ET) power amplifiers (PAs) oriented at a final computationally efficient implementation in a field programmable gate array (FPGA) device. In ET systems, by using a shaping function is possible to modulate the supply voltage according to different criteria. One possibility is to use slower versions of the original RF signal's envelope in order to relax the slew-rate (SR) and bandwidth (BW) requirements of the envelope amplifier (EA) or drain modulator. The nonlinear distortion that arises when performing ET with a supply voltage signal that follows both the original and the slow envelope will be presented, as well as the DPD function capable of compensating for these unwanted effects. Finally, two different approaches for efficiently implementing the DPD functions, a polynomial-based and a look-up table-based, will be discussed.

The design, simulations, and optimized results for a novel low specific absorption rate (SAR) monopole antenna on a single artificial magnetic conductor (AMC) cell are described in this paper. Simulated results show a reduction close to 70% in the 1 g ps SAR for the developed monopole antenna with the AMC in comparison to the monopole antenna without AMC. This allows higher radiation efficiency, battery drain reduction as well as mobile terminal user health risks reduction.

The paper presents a highly efficient GaN-based synchronous buck converter suitable for switching in the lower GHz range. The module includes a very compact 2-stage GaN half-bridge converter MMIC (monolithic microwave integrated circuit) for low parasitic inductances between switches and drivers and a hybrid output network with core-less inductors to avoid ferrite losses. At 1 GHz switching frequency the buck converter achieves with pulse-width modulated (PWM) input signals power loop conversion efficiencies up to 78% for 40 V operation and output voltages up to 33 V. For 100 MHz the power loop efficiencies peak at 87.5% for 14.5 W conversion to 25 V. By changing the output network to a 2nd order low-pass with 700 MHz cut-off frequency the module has been characterized for the use as a supply modulator in very broadband envelope tracking systems with modulation bandwidths of up to 500 MHz. For 1 GHz switching frequency the power-added efficiency peaks at 74% for a 90% duty-cycle PWM input signal. The novelty of this work is that for the first time a buck converter design proves highest flexibility supporting different applications from very compact DC converters to microwave power amplifier efficiency enhancement techniques as well as efficient high frequency switching up to 1 GHz.

In this paper, a rotated E-slot antenna with modified coplanar waveguide (CPW) feeding is presented to obtain broadband characteristics. The antenna comprises of a planar rectangular patch element embedded with E-slot rotated 90° anticlockwise on the radiating side. The CPW feed is modified by extending the ground plane throughout the substrate to surround the rectangular patch. This structure is capable of generating three separate resonant modes with good impedance matching. The antenna is designed on an FR4 substrate of 1.6 mm thickness, covering bands from 3.4 to 3.6 GHz for LTE and 3.4–3.694 GHz for worldwide interoperability for microwave access (WiMAX) systems. The proposed antenna provides good return loss S11 and impedance behavior.

Performance comparison is made between on-chip spiral inductor in flip-chip versus wirebond package technology. Full-wave electromagnetic simulation and on-strip measurement techniques were used to study the performance fluctuations of inductor within flip-chip environment. Results show that the performance of a flipped silicon-based spiral inductor is affected by the radio frequency (RF) current return path differences. The RF current return path for flip-chip is concentrated on the surface of silicon layer exclusively because back side ground under silicon is floating in flip-chip technology. In addition, the bump proximity effect is also considered. On-chip inductors in flip-chip environment must be optimized by reducing the eddy current in the silicon substrate and parasitic affects by adjusting design parameters. The equivalent circuit model of the flipped on-chip spiral inductor is verified with measured results over broadband frequencies. Also, the RF flip-chip characterization technique using on-strip measurement method is presented.

We present a method for detecting parking spaces in radar images based on convolutional neural networks (CNN). A multiple-input multiple-output radar is used to render a slant-range image of the parking scenario and a background estimation technique is applied to reduce the impact of dynamic interference from the surroundings by separating the static background from moving objects in the scene. A CNN architecture, that also incorporates mechanisms to generalize the model to new scenarios, is proposed to determine the occupancy of the parking spaces in the static radar images. The experimental results show very high accuracy even in scenarios where little or no training data is available, proving the viability of the proposed approach for its implementation at large scale with reduced deployment efforts.

This paper presents the design and characterization of an active push/pull toggle RF micro-electro-mechanical systems (MEMS) switch for satellite redundancy networks. The actively controlled pull-up mechanism allows for extended restoring capabilities of the switch in case of ON-state stiction. As a proof of concept an active push/pull MEMS capacitive switch was modeled, designed, and manufactured in shunt configuration on a 50 Ω coplanar transmission line. RF measurement results show a return loss better than 15 dB in the 0.1–40 GHz range and an insertion loss better than 0.5 dB over the same range. The restoring capability of the switch was experimentally proved up to 9 h, and a predictive model was proposed for the estimation of the switch time to failure.

This paper gives a summarized overview on the progress and achievements on AlGaN/GaN high electron mobility transistors (HEMT)-based power amplifiers (PAs) for mobile radio applications which have been achieved within two national funded German projects during a period of six years. Starting with a first 34 dBm (2.5 W, peak) amplifier in 2003 the impressive progress toward highly efficient S-band mobile radio PAs with up to >50 dBm (100 W) peak output power is described by means of some selected single- and multiband amplifier demonstrators. This progress has been mainly enabled by clear progress on GaN technology, device packaging, and PA design. Targeting at highly efficient single-band amplifier applications, a 2.7 GHz symmetrical Doherty amplifier with up to 45% drain efficiency at close to 45 dBm average output power under single-carrier W-CDMA (Wideband Code Division Multiple Access) operation using digital predistortion can be highlighted. In case of multiband capable amplifiers addressing software-defined radio applications, a class-AB-based demonstrator covering a frequency range from 1.8 to 2.7 GHz was realized. The amplifier showed >30% drain efficiency up to 2.5 GHz as well as up to 40 dBm average output power under single-carrier W-CDMA operation using proprietary digital predistortion. Finally, Alcatel-Lucent's activities on envelope tracking for future efficiency improved GaN-based amplifiers are described.

Bessel-beam launchers are promising and established technologies for focusing applications at microwaves. Their use in time-domain leads to the definition of a new class of devices, namely, the X-wave launchers. In this work, we discuss the focusing features of such devices with a specific interest at millimeter waves. The spatial resolutions of such systems are described under a rigorous mathematical framework to derive novel operating conditions for designing X-wave launchers. These criteria might be particularly appealing for specific millimeter-wave applications. In particular, it is shown that an electrically large aperture is not strictly required, as it seemed from previous works. However, the use of an electrically small aperture would demand a considerably wideband capability. The various discussions presented here provide useful information for the design of X-wave launchers. This aspect is finally shown with reference to the practical design of two different X-wave launchers.

This paper presents a low-power and low-noise amplifier (LNA) with resistive-feedback configuration. The design consists of two resistive-feedback amplifiers. In order to reduce the chip area, a resistive-feedback inverter is adopted for input matching. The output stage adopts basic topology of an RC feedback for output matching, and adds two inductors for inductive peaking at the high band. The implemented LNA has a peak gain of 10.5 dB, the input reflection coefficient S11 is lower than −8 dB and the output reflection S22 is lower than −10.8 dB, and noise figure of 4.2–5.2 dB is between 1 and 10 GHz while consuming 12.65 mW from a 1.5 V supply. The chip area is only 0.69 mm2 and the figure of merit is 6.64 including the area estimation. The circuit was fabricated in a TSMC 0.18 um CMOS process.

The surface impedance characteristics of a wire grid composed of infinitely long parallel conducting wires embedded in lossless and lossy frequency-dispersive chiral background media have been investigated. Using wavefield decomposition approach for a chiral background and with the application of impedance boundary conditions for a wire grid, an analytic expression for the surface impedance of a wire grid with a chiral background has been derived. It is shown that the surface impedance magnitude of a wire grid with chiral nihility background is close to zero and almost independent of incident polar angles. A strong chiral background significantly enhances the surface impedance magnitude of a wire grid for incident polar angles closer to right angle as compared to the free space background. The same electromagnetic appearance of a wire grid with frequency-dispersive chiral and free space background media at some critical frequency has also been discussed which may find applications in electromagnetic illusions. It is also shown that if the value of incident polar angles are closer to right angle then the impedance magnitude of a wire grid embedded in the realistic chiral background is smaller as compared to the same wire grid when placed in the free space background.

The novel acoustic transversal topology has demonstrated to be a potential candidate for the development of the next generation of communication filters. The major asset of this topology is its capacity to achieve any filter response without the detriment of limited electro-acoustic coupling. Additionally, this topology prompts for an easy connection of different filters to create multiband and multiplexing responses. This study recalls and further details on the design of multiplexers based on transversal topology using bulk acoustic wave (BAW) or surface acoustic wave (SAW) resonators. An important practical aspect of this topology is the need of a BALUN stage at one port of the filter.

The use of the transversal topology is then applied to another type of acoustic resonator configuration, coupled resonator filter (CRF). Such a resonator configuration offers control over the phase of each transversal path, allowing us to eliminate the BALUN stage. CRF resonators are modeled by means of a different circuit model than BAW or SAW, which calls for a new synthesis procedure. This paper describes the synthesis approach and circuit transformation for the development of multiplexers based on the transversal arrangement of the CRF resonators. An example of a fully simulated 9-plexer is provided to verify this procedure.

In this paper, a novel low-profile planar monopole internal antenna for GSM/DCS/PCS/ IMT/UMTS/WLAN/ISM/LTE operation in the mobile phones is designed and developed. The proposed antenna is composed of multi-branches, F-shaped slots in the system ground plane and tapered feeding line which can improve the impedance matching at the feeding point. The antenna occupying a small area of 18.5 × 46 mm2 is placed on the top no-ground portion of the system circuit board, which makes it suitable for practical mobile applications. A prototype of the proposed antenna is fabricated and tested. In addition, the planar monopole antenna can provide two wide lower and upper bands to respectively cover the frequency range of 848–1152 MHz, and 1736–3000 MHz, for the GSM850/GSM900/DCS1800/PCS1900/IMT2000/UMTS2100/WLAN2400/ISM2450/LTE2300/LTE2500 operation in the mobile phone. Good radiation patterns and antenna peak gain for frequencies over the operating bands have been observed. The antenna is simulated and designed by using Ansoft HFSS and CST Microwave Studio. Details of the antenna design, results on the reflection coefficient, radiation characteristics, directivity, antenna gain, realized gain, and efficiency of the antenna are given and discussed. Finally, the specific absorption rate (SAR) of the proposed antenna placed at the bottom of the mobile phone is also investigated. The obtained SAR values meet the limit of 1.6 W/kg for the 1 g head tissue and 2.0 W/kg for the 10 g head tissue.

This paper presents a novel compact dual-band printed antenna with an omnidirectional radiation pattern for 5G WLAN. The antenna element comprises a star-shaped patch with six disc-shaped elements at the top and a defected ground structure at the bottom, having a radius of 3.77 mm for both. The proper feeding point and alignment with its element parameters help to achieve good impedance matching. The proposed antenna has a single center feed, a low profile, and a straightforward compact structure without any feeding complexity. A high reception fidelity antenna with comparable bandwidth and moderate gain is presented. The prototype radiator was printed on a 4 mm radius and a 1.6 mm thick dielectric substrate (Rogers RT/Duroid 5880), with a dielectric constant of 2.2. The designed antenna is fabricated and measured to validate the simulation result. The measured impedance bandwidth of 1.3 GHz (27.5–28.8 GHz) and 2.2 GHz (32.45–34.65 GHz) with a respective measured gain of 1.1 and 3.2 dBi are achieved at 28 and 34 GHz. The simulated radiation efficiency of above 95% is achieved for both bands. A good agreement between simulated and measured results of the proposed work shows that the proposed antenna is suitable for 5G short-range WLAN communications.

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.

A compact coplanar waveguide (CPW)-fed wideband metamaterial-inspired antenna is designed and developed in this paper. The proposed structure is an asymmetric structure in which three rectangular stubs are employed between signal patch and CPW ground plane. It is demonstrated that these stubs provides lumped parameters of conventional epsilon-negative transmission line (ENG-TL). As an advantage of these stubs proposed antenna operates on 1.67–2.76 GHz with −10 dB impedance bandwidth of 49.2%. The proposed antenna having small electrical size of 0.17λ0 × 0.35λ0 × 0.01λ0 at fo = 2.21 GHz. The simulated average gain and radiation efficiency of the proposed antenna is 1.61 dB and 96.33% respectively throughout the bandwidth. Properties such as smaller electrical size, simpler design, consistent radiation characteristics, and ease of fabrication are making this antenna suitable for GSM, WLAN/Wi-Fi, Bluetooth, and WiMAX applications.

This paper presents a novel miniaturized substrate integrated waveguide filter by combining both half-mode resonators and capacitive loading on a conventional two-layer printed circuit board (PCB) process. The resulting synthesis is successfully demonstrated in an long-term evolution application by means of a third-order filter of <225 mm2 in size while featuring 2.3 dB insertion loss over a 5.5% fractional bandwidth at 3.7 GHz. Good first-iteration agreement between simulated and measured results, both in center frequency and bandwidth, are achieved.

A low-profile circularly polarized (CP) slot antenna to achieve a wide axial-ratio (AR) beamwidth is proposed in this paper. The radiating patch consists of two orthogonal pairs of parallel slots etched symmetrically onto a ground plane. Firstly, our theoretical study demonstrates that the CP radiation can be satisfactorily achieved at the broadside, when the vertical and horizontal paired-slots are excited in the same amplitude with 90° phase difference. Secondly, the principle of CP radiation of the proposed antenna on an infinite ground plane is described. Through analyzing the spacing between two parallel slots, the |Eθ| and |Eφ| radiation patterns can be made approximately identical with each other over a large angle range. As such, the slot antenna achieves a wide AR beamwidth. After that, the 3 dB AR beamwidth with respect to the size of a finite ground plane is investigated to constitute a practical CP antenna on a finite ground plane. In final, the proposed CP antenna with a 1–4 probe-to-microstrip feeding network is designed and fabricated on a finite ground plane of a dielectric substrate. Measured results are shown to be in good agreement with the simulated ones about the gain, reflection coefficient, AR bandwidth, and radiation patterns. Most importantly, a wide 3 dB AR beamwidth of 126° and low-profile property with the height of 0.036λ0 are achieved.