A selection of hybrid frequency- and time-domain approaches is evaluated with respect to their suitability for predicting the multi-tone behavior of a reference Ku-band helix traveling-wave tube. For this, a frequency-domain code is extended by a selection of frequency-dependent and frequency-independent envelope models and compared to a number of simulated and measured responses to two-tone signal excitation with varying frequency spacing. The selected envelope methods are investigated both in the hybrid approach and based on measured TWT characteristics. Output levels and classical multi-tone metrics, such as intermodulation products and phase transfer factors, are considered. By reducing a modulation scenario to a number of significant sequences, a comparison to full physics-based frequency-domain simulation is presented to show the potential of the proposed approach.

In this paper, a slow-wave transmission line implemented in coplanar waveguide technology, based on simultaneous inductive and capacitive loading, is presented for the first time. The shunt capacitors are achieved by periodically etching transverse strips in the back substrate side, connected to the central strip through metallic vias. The series inductors are implemented by etching rectangular slots in the ground plane. The effect of these reactive elements is an enhancement of the effective shunt capacitance and series inductance of the line, leading to a significant reduction of the phase velocity (slow-wave effect). Consequently, the guided wavelength is also reduced, and these lines can be applied to the miniaturization of microwave components. Moreover, due to periodicity, these artificial lines exhibit stop bands (Bragg effect) useful for spurious or harmonic suppression. A compact harmonic suppressed power splitter, based on a slow wave 35.35 Ω impedance inverter, has been designed and fabricated in order to demonstrate the potential of the proposed approach. The length of the inverter is 48% the length of the conventional counterpart, and measured power splitting at the first (3f0) and second (5f0) harmonic frequencies is rejected more than 49 and 23 dB, respectively.

Sentinel-1A is a space-borne synthetic aperture radar (SAR) system developed in the frame of the Copernicus Program. The German Aerospace Center supported the radiometric and polarimetric calibration of Sentinel-1A by the analysis of point target responses of several acquisitions considering different modes, beams, and polarization channels. An elevation dependent bias, which had not been properly predicted by the used antenna model, was found for all investigated modes. Offsets of up to 2 dB were determined during the SAR instrument calibration phase, in particular, for low and high elevation angles. Therefore, in order to correct these elevation biases, a radiometric refinement was carried out by European Space Agency in November 2015. After that, Sentinel-1A radiometric accuracy and long-term stability were analyzed over a period of 1.5 years. For this period, the absolute calibration factor and the channel imbalance were determined for the main imaging mode. Moreover, a slight drift of the derived calibration factor was observed starting from July 2016. At the same time an anomaly was detected in the front-end affecting several transmit and receive modules in one tile. The radiometric behavior of Sentinel-1A should therefore be monitored for a longer period of time, especially to detect potential degradation effects of the SAR instrument.

Karlsruhe Institute of Technology (KIT) is doing research and development in the field of megawatt-class radio frequency (RF) sources (gyrotrons) for the Electron Cyclotron Resonance Heating (ECRH) systems of the International Thermonuclear Experimental Reactor (ITER) and the DEMOnstration Fusion Power Plant that will follow ITER. In the focus is the development and verification of the European coaxial-cavity gyrotron technology which shall lead to gyrotrons operating at an RF output power significantly larger than 1 MW CW and at an operating frequency above 200 GHz. A major step into that direction is the final verification of the European 170 GHz 2 MW coaxial-cavity pre-prototype at longer pulses up to 1 s. It bases on the upgrade of an already existing highly modular short-pulse (ms-range) pre-prototype. That pre-prototype has shown a world record output power of 2.2 MW already. This paper summarizes briefly the already achieved experimental results using the short-pulse pre-prototype and discusses in detail the design and manufacturing process of the upgrade of the pre-prototype toward longer pulses up to 1 s.

This paper reports scanning microwave microscopy of CMOS interconnect aluminum lines both bare and buried under oxide. In both cases, a spatial resolution of 190 ± 70 nm was achieved, which was comparable or better than what had been reported in the literature. With the lines immersed in water to simulate high-k dielectric, the signal-to-noise ratio degraded significantly, but the image remained as sharp as before, especially after averaging across a few adjacent scans. These results imply that scanning microwave microscopy can be a promising technique for non-destructive nano-characterization of both CMOS interconnects buried under oxide and live biological samples immersed in water.

This work presents a fully differential wideband and low power 240 GHz multiplier-by-8 chain, manufactured in IHP's 130 nm SiGe:C BiCMOS technology with fT/fmax = 300/500 GHz. A single ended 30 GHz input signal is multiplied by 8 using Gilbert cell-based quadrupler and doubler, and then amplified with a wideband differential 3-stage cascode amplifier. To achieve wide bandwidth and optimize for power consumption, the power budget has been designed in order to operate the frequency multipliers and the output amplifier in saturation. With this architecture the presented circuit achieves a 3 dB bandwidth of 40 GHz, meaning a relative 3 dB bandwidth of 17%, and a peak saturated output power of 0 dBm. Harmonic rejections better than 25 dB were measured for the 5th, 6th, and 7th harmonics. It dissipates 255 mW from 3 V supply which results in drain efficiency of 0.4%, while occupying 1.2 mm2. With these characteristics the presented circuit suits very well as a frequency multiplier chain for driving balanced mixers in 240 GHz transceivers for radar, communication, and sensing applications.

Multipath propagation occurs in many situations of radar measurements in complex environments. The unwanted effects range from interference over the radar channels, which causes amplitude fading and a corrupted direction of arrival (DOA) estimation, to the detection of ghost targets in an angle of arrival of the multipath direction. Due to the different number of reflections, polarimetric radars are capable to separate certain multipaths from direct paths if the target is known in advance. Furthermore, it is possible to separate objects with different polarimetric features in DOA that are located in the same radial distance to the radar. In this paper, a new approach to DOA detection based on the coherent Pauli decomposition is presented. With this approach, important multipath and DOA effects are analyzed and measurement results at 77 GHz on canonical objects in an anechoic chamber are presented. The results prove the feasibility of the approach and demonstrate the occurring effects.

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.

This paper presents a fully-integrated direct-conversion fundamentally-operated mixer-first quadrature receiver module with a tunable LO in the 219–266 GHz band. It has been implemented in a 0.13-μm SiGe heterojunction bipolar transistor technology. It includes an on-chip LO path driven externally from the printed circuit board (PCB) connector level at 13.6–16.7 GHz. A hybrid coupler generates the quadrature LO signal, which drives a pair of double-balanced fundamentally-operated down-conversion mixers, whose RF ports are connected to a wideband lens-integrated on-chip ring antenna. The chip-on-lens assembly is placed in the recess of a high-speed PCB and wire-bonded. To compensate the inductive behavior of the wire-bond interconnection between the chip and the PCB at the high-speed IF outputs, an on-board 8-section step-impedance low-pass filter has been implemented. The module shows a 47 GHz 3-dB radio frequency/local oscillator operation bandwidth (BW), a peak conversion gain of 7.8 dB, a single-side-band noise figure of 11.3 dB, and a 3-dB IF BW of 13 GHz. The in-phase and quadrature amplitude imbalance stays below 1.58 dB for the 210–280 GHz band. The down-conversion and the baseband stages consume together 75.5 mW, while the LO path 378 mW. The maximum data-rate achieved with this receiver in combination with the transmitter presented in [1–3] is 60 Gbps for quadrature phase shift keying modulation.

This paper presents the design and characterization of a D-band (110–170 GHz) monolithic microwave integrated direct carrier quadrature modulator and demodulator circuits with on-chip quadrature local oscillator (LO) phase shifter and radio frequency (RF) balun fabricated in a 130 nm SiGe BiCMOS process with ft/fmax of 250 GHz/400 GHz. These circuits are suitable for low-power ultra-high-speed wireless communication and can be used in both homodyne and heterodyne architectures. In single-sideband operation, the modulator demonstrates a maximum conversion gain of 9.8 dB with 3-dB RF bandwidth of 33 GHz (from 119 GHz to 152 GHz). The measured image rejection ratio (IRR) and LO suppression are 19 dB and 31 dB, respectively. The output P1dB is −4 dBm at 140 GHz RF and 1 GHz intermediate frequency (IF) and the chip consumes 53 mW dc power. The demodulator, characterized as an image reject mixer, exhibits 10 dB conversion gain with 23-dB IRR. The measured 3-dB RF bandwidth is 36 GHz and the IF bandwidth is 18 GHz. The active area of both the chips is 620 µm × 480 µm including the RF and LO baluns. A 12-Gbit/s QPSK data transmission using 131-GHz carrier signal is demonstrated on modulator with measured modulator-to-receiver error vector magnitude of 21%.

Medical imaging is of great importance for patients affected by stroke. Since an early examination of the patient is necessary for successful recovery, there is room to improve the existing capabilities of analysis. Common systems like magnetic resonance imaging or computed tomography are precise, but stationary, and therefore, not ideally suited for the early analysis of stroke. The presented multiport vector network analyzer system uses electromagnetic tomography (EMT) as an alternative imaging technique. It consists of a network of distributed electronic sensor nodes which improve important parameters: the parallel measurement setup reduces the measurement time as low as 160 ms for a 200-port S-parameter matrix and it is capable of measuring signal levels down to − 150 dBm. The electronics allow a compact, movable packaging, leading the way for future portable devices. The detection of stroke models was examined by test measurements of a phantom. The data was analyzed by the help of an inverse reconstruction algorithm. The possibility of building portable setups which can be even applied to patients inside an ambulance, makes EMT a suitable alternative for early stroke detection. It can help in shortening the recovery of patients, by providing an early analysis of the brain.

This paper provides an overview of theory, design, simulation, and fabrication of novel spatial harmonic magnetrons (SHMs). An approximate analysis which provides the guidelines for the design and predicts the important characteristics of these devices will be presented. This analysis shows that the metamaterial loaded SHMs can start generating power with very small cathode current densities which is very important for designing THz sources based on SHMs. A design example with the operation frequency of 43 GHz together with the design procedure, PIC simulations, and measurement results will be examined.

This work addresses the piezoelectric induced reduction of quality factor in fully-printed metal-insulator-metal (MIM) barium strontium titanate (BST) thick film varactors designed for high power operation. An acoustically optimized varactor design is presented and compared to a non-optimized high-power varactor. The design is utilized to present a narrowband acoustic suppression technique based on defined weights. The acoustically optimized varactor consists of 162 varactor cells in a capacitive matrix. The cells in the matrix are interconnectable allowing for a variable unbiased capacitance and power rating. Due to this setup, surface acoustic waves are interrupted, and the reduced size of the cells allows for a reduced BST layer thickness, shifting the acoustic resonance away from the operational frequency. Therefore, an inverted behavior in comparison to the high-power varactor is observed with an increasing quality factor with biasing voltage. Compared to the high-power varactor, the acoustically optimized varactor design shows a 40% increased quality factor in biased state. By applying the narrowband acoustic suppression technique, an increase in quality factor of 145% is achieved compared to the unsuppressed design. In comparison to the high-power varactor, the acoustical suppressed design shows an increase in quality factor of 480% at the first acoustic resonance frequency.

This contribution deals with array elements for K/Ka-band satellite communication terminals. It proposes an end-fire design realized in substrate integrated waveguide technology and featuring dual-band functionality, and dual circular polarization. The latter is achieved by means of a dual-band orthomode transducer. An extended hemispherical dielectric lens ensures good matching and radiation properties. The feed structure is composed of a multilayer printed circuit board and tapered superstrates. The design procedure of the components is explained in detail and three different variants of the antenna are compared. The measured scattering and far-field parameters validate the concept.

This paper presents an active Q-enhanced LC dual-band band-pass filtering approach using parallel synthesis techniques at X- and Ku-bands in 0.13 µm SiGe BiCMOS technology. By employing two independently tunable parallel LC-tanks with either in-phase and out-of-phase addition, independently tunable dual-band filtering is achieved. For higher out-of-band (OOB) attenuation, subtraction of the two 2nd-order bandpass filter is implemented. The two bands are independently tunable in terms of Q and center frequency. The dual-band filter at 9.7 GHz and 13.9 GHz achieves a normalized dynamic range of 165–154.5 dB.Hz with an OOB attenuation of >50 dB below 3 GHz. In between the two bands, the attenuation is 22 dB when the two passbands have 200 MHz bandwidth each. The total group delay is 0.8 ns and 1.9 ns for Q of 20 and 50, respectively. The filter achieves better OOB rejection with wider band channels at X- and Ku-bands compared with state of the art integrated filters. The filter consumes 115–130 mW of DC power. The core die area is 0.53 × 0.7 mm2.

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.

We demonstrate a sub-terahertz (THz) and THz integration platform based on micromachined waveguides on silicon. The demonstrated components in the frequency range 225–325 GHz include waveguides, filters, waveguide vias, and low-loss transitions between the waveguide and the monolithic integrated circuits. The developed process relies on microelectromechanical systems manufacturing methods and silicon wafer substrates, promising a scalable and cost-efficient system integration method for future sub-THz and THz communication and sensing applications. Low-temperature Au/In thermo-compression and Au–Au laser bonding processes are parts of the integration platform enabling integration of millimeter-wave monolithic integrated circuits.

A next generation of active electronically scanned array (AESA) antennas will be challenged with the need for lower size, weight, power, and cost. This leads to enhanced demands especially with regard to the integration density of the radio frequency-part inside a T/R module. The semiconductor material GaN has proven its capacity for high-power amplifiers (HPA), robust receive components as well as switch components for separation of transmit and receive mode. This paper will describe the design and measurement results of a GaN-based single-chip T/R module frontend (HPA, low noise anplifier, and single-pole double-throw (SPDT)) using UMS GH25 technology and covering the frequency range from 8 GHz to 12 GHz. The key performance parameters of the frontend are 13 W minimum transmit (TX) output power over the whole frequency range with peak power up to 17 W. The frontend in receive (RX) mode has a noise figure below 3.2 dB over the whole frequency range, and can survive more than 5 W input power. The large signal insertion loss of the used SPDT is below 0.9 dB at 43 dBm input power level.

We present a novel bonding process for gallium nitride-based electronic devices on diamond heat spreaders. In the proposed technology, GaN devices are transferred from silicon (Si) onto single (SCD) and polycrystalline diamond (PCD) substrates by van der Waals bonding. Load-pull measurements on Si and SCD heat spreaders at 3 GHz and 50 V drain bias show comparable power-added-efficiency and output power (Pout) levels. A thermal analysis of the hybrids was performed by comparison of 2 × 1mm2 AlGaN/GaN Schottky diodes on Si, PCD, and SCD, which exhibit a homogeneous field in the channel in contrast to gated transistors. Significantly different currents are observed due to the temperature dependent mobility in the 2DEG channel. These measurements are supported by a 3D thermal finite element analysis, which suggests a large impact of our transfer technique on the thermal resistance of these devices. In summary, we show a promising new GaN-on-diamond technology for future high-power, microwave GaN device applications.