Two compact H-band (220–325 GHz) low-noise millimeter-wave monolithic integrated circuit (MMIC) amplifiers have been developed, based on a grounded coplanar waveguide (GCPW) technology utilizing 50 and 35 nm metamorphic high electron mobility transistors (mHEMTs). For low-loss packaging of the circuits, a set of waveguide-to-microstrip transitions has been realized on 50-μm-thick GaAs substrates demonstrating an insertion loss of <0.5 dB at 243 GHz. By applying the 50 nm gate-length process, a four-stage cascode amplifier module achieved a small-signal gain of 30.6 dB at 243 GHz and more than 28 dB in the bandwidth from 218 to 280 GHz. A second amplifier module, based on the 35-nm mHEMT technology, demonstrated a considerably improved gain of 34.6 dB at 243 GHz and more than 32 dB between 210 and 280 GHz. At the operating frequency, the two broadband low-noise amplifier modules achieved a room temperature noise figure of 5.6 dB (50 nm) and 5.0 dB (35 nm), respectively.

The paper presents millimeter-wave (mm-wave) signal sources using a hetero-integrated InP-on-BiCMOS semiconductor technology. Mm-wave signal sources feature fundamental frequency voltage-controlled oscillators (VCOs) in BiCMOS, which drive frequency multiplier–amplifier chains in transferred-substrate (TS) InP-DHBT technology, heterogeneously integrated on top of the BiCMOS wafer in a wafer-level bonding process. Both circuits are biased through a single set of bias pads and compact low-loss transitions from BiCMOS to InP circuits and vice versa have been developed, which allows seamless signal routing through both technologies exhibiting 0.5 dB insertion loss up to 200 GHz. One VCO operates at 82 GHz with a tuning range of 600 MHz and an output power of approximately 8 dBm. A frequency doubler combined with this VCO circuit delivers 0 dBm at 164 GHz and a frequency tripler with a similar VCO delivers −10 dBm at 246 GHz. Another hetero-integrated W-band doubler–amplifier circuit demonstrates 12.9 dBm saturated output power with 5.9 dB conversion gain at 96 GHz. A direct comparison of the TS InP-DHBT MMIC with either silicon or traditional AlN carrier substrates shows the favorable properties of the hetero-integrated process discussed here. The results demonstrate the feasibility of hetero-integrated circuits operating well above 100 GHz.

In this paper, a passive double-balanced mixer in SiGe HBT technology is presented. Owing to lack of suitable passive mixing elements in the technology, the mixing elements are formed by diode-connected HBTs. The mixer uses lumped element Marchand baluns on both the local oscillator (LO) and the radio frequency (RF) port. A break out of the Marchand balun is measured. This demonstrates good phase and magnitude match of 0.7° and 0.11 dB, respectively. The Marchand baluns are broadband with a measured 3 dB bandwidth of 6.4 GHz, while still having a magnitude imbalance better than 0.4 dB and a phase imbalance better than 5°. Unfortunately with a rather high loss of 2.5 dB, mainly due to the low Q-factor of the inductors used. The mixer is optimized for use in doppler radars and is highly linear with a 1 dB compression point above 12 dBm IIP2 of 66 dBm. The conversion gain at the center frequency of 8.5 GHz is −9.8 dB at an LO drive level of 15 dBm. The whole mixer is very broadband with 3 dB bandwidth from 7 to 12 GHz covering the entire X-band. The LO–IF, RF–IF, and RF–LO isolation is better than 46, 36, and 36 dB, respectively, in the entire band of operation.

In this paper, the small- and large-signal modeling of InP heterojunction bipolar transistors (HBTs) in transferred substrate (TS) technology is investigated. The small-signal equivalent circuit parameters for TS-HBTs in two-terminal and three-terminal configurations are determined by employing a direct parameter extraction methodology dedicated to III–V based HBTs. It is shown that the modeling of measured S-parameters can be improved in the millimeter-wave frequency range by augmenting the small-signal model with a description of AC current crowding. The extracted elements of the small-signal model structure are employed as a starting point for the extraction of a large-signal model. The developed large-signal model for the TS-HBTs accurately predicts the DC over temperature and small-signal performance over bias as well as the large-signal performance at millimeter-wave frequencies.

In this paper, the concept of load-modulated power amplifiers (PAs) is studied. Two GaN-HEMT power amplifiers (PAs), targeted for high efficiency at maximum and output back-off (OBO) power levels, are designed, implemented, and tested across 1.8–2.2 GHz. The load modulation in the first design is realized by tuning the shunt capacitors in the output matching network. A novel method is employed in the second design, where barium–stronrium–titante is used for the realization of load modulation. The large-signal measurement results across the desired band show 59–70% drain efficiency at 44–44.5 dBm output power for both designs. Using the available tunable technique, the drain efficiency of the PAs is enhanced by 4–20% at 6 dB OBO across the bandwidth.

This work presents radio-frequency-microelectromechanical-system (RF-MEMS)-based tunable matching networks for a multi-band gallium nitride (GaN) power amplifer (PA) application. In the frequency range from 3.5–8.5 GHz return losses of 5–10 dB were measured for the input network, matching impedances close to the border of the Smith chart. For the output matching network return losses of 10–20 dB and insertion losses of 1.3–2 dB were measured. The matching networks can tune the PA to four different operating frequencies, as well as changing the transistor's mode of operation from maximum delivered-output-power to maximum power-added-efficiency (PAE), while keeping the operating frequency constant. Furthermore, different single pole double throw (SPDT)-switches are designed and characterized, to be used in frequency-agile transmit/receive-modules (T/R modules).

In this paper, a uniplanar RF-MEMS second-order bandpass filter with reconfigurable center frequency is presented. It is based on quarter-wavelength slotline resonators and coplanar waveguide (CPW)-to-slotline multimodal immitance inverters (MIIs), which are reconfigured using RF-MEMS switchable CPW air-bridges (SABs). The filter can be adequately explained and designed using multimodal theory and circuit models. A surface micromachining process on high-resistivity silicon substrate was used to fabricate the filter. Experimental results show frequency reconfiguration from 12 to 13 GHz, maintaining the same relative bandwidth, and insertion losses of 4.6 and 4.7 dB, respectively.

Several types of multiplexers based on isolation circuits have been introduced and investigated. Combining method of two filtering circuits (CMTC) is one way to make multiplexers based on isolation circuits. This method fits well for designing contiguous channel triplexers. A triplexer based on CMTC consists of a conventional transmission line (TL) connected to a diplexer and a composite right/left-handed (CRLH) TL connected to a filter. The triplexer based on CMTC has two significant advantages. One is that it is not necessary to modify the design of a stand-alone filter and diplexer and there is freedom in the choice of filtering circuits. In addition, a designer does not need to perform three-dimensional full-wave optimization, because of a simple and straightforward design concept. In this paper, a triplexer prototype having 1, 1.125, and 1.25 GHz center frequencies, is designed and fabricated. The measured results show good agreement with the simulation results.

Combining a theory for reflection-free termination of coaxial lines together with a novel manufacturing method results in 1-mm coaxial matched loads with an excellent absorption behavior over the frequency range from 0 to 110 GHz. Three different electromagnetic (EM) simulation approaches verify the capability of these matched loads to achieve reflection coefficients smaller than −43 dB over the entire frequency range. Matched loads with a maximum reflection coefficient of only −32 dB have been produced. An excellent performance was achieved by exponentially tapering the outer conductor over the region of a coaxial ceramic substrate coated by a thin-film resistance and by compensation for EM wave propagation inside the resistive coating.

Two compact resonant near-field sensors are introduced for the characterization of aqueous solutions at 5 GHz. They are based on folded substrate-integrate circular half-mode resonators with a planar sensing tip. Owing to the planar design, the sensor is simple and cheap to manufacture, and a sample can be easily coupled to the resonator from the top. The operating principle of the sensor is explained and verified by both simulation and measurement. The radiation of the sensors is quantified by means of a quality factor analysis. Finally, a previously introduced calibration method based on the perturbation theory is applied to the sensors and its accuracy is improved by choosing more suitable reference materials.

The orthogonal LSM10 and TE10 modes that are supported by the image SINRD (iSINRD) guide and substrate integrated waveguide (SIW) is exploited to develop a planar millimeter-wave hybrid orthogonal-mode transducer (OMT) within the same dielectric substrate. The two output arms are iSINRD guide and an SIW. The proposed co-layered planar OMT belongs to a narrowband acute angle class. The design process is explained and measurements at 94 GHz are presented. No septa or step changes in thickness are required. Both modes are excited using WR10 transitions, where the transition of one mode is orthogonal to the other. Therefore, the OMT is fabricated as a back-to-back 4-port OMT; two inputs and two outputs for each mode respectively. The lateral dimensions of all guiding arms are 0.6 × 0.635 mm2. An insertion loss of around 1.2 dB is obtained for both LSM10 and TE10 modes, while isolation better than 17 dB is obtained for both modes (30 dB for the LSM10 mode).

In this work, a liquid crystal based tunable composite right/left-handed transmission line for future leaky wave antennas working at the Ka-band is presented. The tuning of the liquid crystal is achieved by means of magnetic and electric biasing. For this purpose, different prototypes are fabricated for each biasing technique and their dispersive characteristics compared. Electric tunability is achieved by implementing highly resistive bias lines in the unit cell layout. Both techniques yield similar tuning capabilities at the operation frequency of 27GHz whereas the electric one has the advantage of being easily integratable in the layout.

New wireless wearable monitoring systems integrated in professional garments require a high degree of reliability and autonomy. Active textile antenna systems may serve as platforms for body-centric sensing, localisation, and wireless communication systems, in the meanwhile being comfortable and invisible to the wearer. We present a new dedicated comprehensive design paradigm and combine this with adapted signal-processing techniques that greatly enhance the robustness and the autonomy of these systems. On the one hand, the large amount of real estate available in professional rescue worker garments may be exploited to deploy multiple textile antennas. On the other hand, the size of each radiator may be designed large enough to ensure high radiation efficiency when deployed on the body. This antenna area is then reused by placing active electronics directly underneath and energy harvesters directly on top of the antenna patch. We illustrate this design paradigm by means of recent textile antenna prototypes integrated in professional garments, providing sensing, positioning, and communication capabilities. In particular, a novel wearable active Galileo E1-band antenna is presented and fully characterized, including noise figure, and linearity performance.

Size and feed structure are some of the important constraints for using antenna-elements in multi-element two-dimensional arrays, where easy planar integration and appropriate matching with transceiver chips are essential. This applies especially when differential signaling and adaptable polarization are required. Based on a balanced-fed patch-excited cavity-backed horn antenna (hybrid antenna), feeding concepts, and approaches to reduce size are discussed and evaluated in this paper. The influence of the substrate-integrated cavity is analyzed and methods to overcome the restrictions are presented, together with simulated and measured results. The antenna elements are evaluated with regard to their use in multistatic and polarimetric sparse arrays, which will be briefly introduced. The optimized antennas achieve 10 dB return loss, a gain of more than 5 dBi as well as symmetric and homogeneous radiation patterns in amplitude and phase with low cross-polarization in the desired frequency-band of operation between 70 and 80 GHz.

A channel estimation method for chipless wireless sensors is presented. The method is developed to suppress interference signals in radio frequency backscatter systems. It uses two adjacent frequency bands to estimate and suppress the disturbing signal of a dynamic interferer. Afterwards a correction of the sensor tag's backscatter signal is achieved. The method has been tested in indoor measurements with a chipless strain sensor and a chipless temperature sensor. A metal block has been deployed as an interferer. In the given scenario, the method has enabled a determination of the sensors' resonance frequencies with relative errors of <2% in average. A general dependence of the estimation robustness on the peak bandwidth is observed.

This paper proposes a fully integrated 160-GHz transmitter and receiver in package for millimeter-wave applications. The monolithic integrated circuits were designed with a harmonic approach and were fabricated using a SiGe:C HBT production technology with an fT and fmax of 170 and 250 GHz, respectively. The manufactured 2006 × 1865 µm2 bare dies were integrated in 6 × 6 mm2 embedded wafer level ball grid array packages, where they were interconnected with highly directional antennas built on the redistribution layer of the packages. With a total frequency multiplication factor of 36 and an active balun at the first stage, the transmitter allows the use of a 4.5-GHz input signal driven from a single-ended signal source [1] and distributed on a standard low-cost printed circuit board. The receiver comprises a Gilbert-cell-based subharmonic mixer with a simulated 1-dB input compression point of −4 dBm, and a minimum double-sideband noise figure of 16.5 dB. The functionality of the proposed system was successfully demonstrated in a quasi-monostatic FMCW radar measurement with a 1-ms up-chirp frequency sweep from 157 to 160 GHz and in a forward-scatter imaging experiment with an 8-GHz frequency ramp from 157 to 165 GHz.

This paper discusses the operating range of frequency modulated (FM) radars in the presence of interference. For this purpose, radar- and path loss equations are used to draw the equipotential lines for a given signal-to-interference ratio as a function of the spatial distribution of targets and interferers in order to identify relevant scenario constellations. Further the factors influencing the gain of signal versus deterministic interference are discussed based on measurements and simulations. Finally, the influence of different kinds of interference on the spectrum of a frequency modulated continuous wave radar is shown.

We present a heterodyne frequency-modulated continuous-wave (FMCW) radar, applicable in short-range applications. Owing to a modulation of the transmit (TX) signal, the intermediate frequency (IF) signal can be shifted away from zero frequency to reduce the influence of dc-offsets and low-frequency disturbances like, e.g. flicker noise existing in components like mixers, amplifiers and analog-to-digital converters. The presented system is based on E-band transceivers realized in SiGe technology, which are fully integrated with antennas in a plastic package. A sinusoidal modulation of the TX signal is realized by a binary phase-shift keying modulator, which is controlled by a Delta–Sigma sequence. The choice of a sinusoidal modulation allows to reuse signal processing blocks which are typically available in FMCW radars. Measurements show that the achievable signal-to-noise ratio is comparable to a homodyne realization since the Delta–Sigma noise can be filtered in the IF stage. Experiments with a bandwidth of 8 GHz demonstrate measurements down to 12 cm with standard deviations of the measured ranges lower than 60 µm. Compared to a homodyne realization the blocking distance could be reduced by approximately 40 mm.

This paper clarifies what we benefit from single-input–multiple-output (SIMO) or multiple-input–multiple-output (MIMO) radar. We have developed an X-band sparse array imaging radar system capable of operating at both SIMO and MIMO modes. The hybrid radar modes are realized without any modification in hardware, but simply by switching the scheme of waveform generation and post-processing. A comparison has been made between the SIMO mode adopting a chirp pulse waveform and the MIMO mode based on the code-division multiple access method using the Gold-coded pulse waveform. Mutually complementary properties between the SIMO and MIMO modes in terms of the cost of computation, the ease of array calibration, and the detectability of targets are clarified through simulations and an experiment.