This paper presents a flexible SiGe monolithic microwave integrated circuit (MMIC) chipset for 120 GHz ultra-wideband frequency-modulated continuous wave radar systems. The highly integrated chipset is implemented with multiple-input and multiple-output radar in mind which leads to transmit and receive MMICs with four integrated channels in each chip. The transmitter achieves an output power of 12.9 dBm with a total power consumption of only 403 mW. The receiver chip incorporates a sub-harmonic approach for suppression of leakage radiation at 120 GHz through a receive channel. Both chips integrate active multiplier chains that are driven by a third reference dual band voltage-controlled oscillator (VCO) MMIC that can deliver an output at center frequencies of 15 or 30 GHz. The reference VCO MMIC demonstrates relative tuning ranges of 32%.

This manuscript presents a millimeter-wave GaN high-power amplifier (HPA) intended for next generation inter-satellite links (ISLs). The proposed architecture achieves a fractional bandwidth wider than 18% in the V-band spectrum, to deliver a 10 Gbit/s throughput compatible with multi-thousand-km ISLs. Core of the HPA is the monolithic microwave integrated circuits (MMIC ) power amplifier which covers the whole 59–71 GHz band with high efficiency through innovative topologies and a cutting-edge gallium nitride on silicon carbide (GaN-on-SiC) process. The MMIC is then parallelized by means of a 1-to-8 splitter/combiner to obtain a V-band 10 W GaN HPA. Measurement results show a peak small-signal gain of 25.6 dB, 6.5% peak power-added efficiency, and a maximum P1dB of 40.3 dBm.

Antenna arrays are a main driver of next generation millimeter-wave communication and radar systems as shrinking antenna sizes leverage larger arrays to compensate for reduced link budget. However, conventional phase controlled arrays exhibit a frequency dependent scan angle that appears as loss to a fixed counterpart. Bandwidth limitations introduced by the so-called beam squint effect hinder larger array sizes and data rates thereby generating a demand for timed arrays as a solution. This paper gives a quantified overview of the beam squint phenomenon, different hardware architectures as well as evaluation parameters and common shortcomings of true-time delay (TTD) elements. A broad variety of TTD realizations from literature are compared by their operational principles and performance. Finally, the delay interpolation principle, its non-idealities, and their impact on a hierarchically time delay controlled D-band antenna array are described. Extended content on a previously published, continuously tunable TTD implementation at a center frequency of 144 GHz with a bandwidth of 26 GHz and a delay range of 1.75 ps that requires only 0.53 × 0.3 mm2 of core chip area is presented. Measurement results have been obtained from a demonstrator manufactured in 130 nm BiCMOS technology.

This work describes the design process of a single-pole double-throw (SPDT) microwave switch operating at Ka-band. It is tailored to a tunable reflective termination design that can be used in tunable power amplifier configurations. A high electron mobility transistor and a resonating network are employed in shunt configuration to enhance the performance in the output port’s active and inactive conditions. The small and large signal measurements showcase a 2 GHz bandwidth with an insertion loss and isolation better than −1.8 dB and −25 dB, respectively, and handling power levels of up to 3 W at 30.5 GHz. The load-pull measurements across the entire Smith chart offer comprehensive insights into the behavior of the SPDT when operating with complex and reactive loads, fulfilling the purpose of tunable reactive termination.

Worldwide adoption of 5G mobile devices has been one of the main driving engines behind semiconductor industry. Since the initial release in 2020, 5G-enabled devices have surpassed the market penetration of 3G/4G smartphones. 5G brings higher data capacity, low latency, and new applications. These are possible due to lower feature nodes such as FinFET 3 nm/5 nm but also due to improvements of the 5G radio frequency (RF)front-end circuitry. This paper presents 5G RF front-end architectures with novel circuits and measurement details which will be part of future 5G advanced and 6G mobile devices and are easier to be controlled using digital circuitry. The paper presents an envelope-controlled power amplifier (PA) principle, along with a novel simplified calibration architecture designed for 5G/5G+ operating under 6 GHz, as well as for frequency range 2 millimeter-wave PAs. An earlier version of this paper was presented at the 2023 53rd European Microwave Conference and was published in the Proceedings [Balteanu F, Thoomu K, Pingale A, Venimadhavan S, Sarkar S, Choi Y, Modi H, Drogi S, Lee J and Agarwal B (2023) Enabling RF circuit techniques for 5G and beyond In 53rd European Microwave Conference (EuMC), Berlin, Germany, 22–25].

This paper presents the bit efficiency of 28 GHz digital beamforming in over-the-air (OTA) measurements and simulations for distributed massive multiple-input–multiple-output (D-MIMO) and collocated massive multiple-input–multiple-output (C-MIMO) systems, as well as simulations for a 3.75 GHz small-cell scenario. Under the condition that users are randomly located in the line of sight coverage indoor area and spatially selected from each other by the normalized zero-forcing method, the OTA measured D-MIMO system exhibits an average of 4–7 dB better signal-to-noise ratio compared to C-MIMO when the number of simultaneously connected users “K” approaches the number of transceivers “M.” This means that the D-MIMO system provides higher bit efficiency than the C-MIMO system when K/M is large. Furthermore, the D-MIMO 3.75 GHz simulation predicts a relatively approximate 30% higher maximum efficiency than C-MIMO due to the shorter average distances between user equipment and access points in the D-MIMO system. To the best of the author’s knowledge, an earlier version of this paper has been presented at the 53rd European Microwave Conference as a first report on the 28 GHz OTA measured bit efficiency between C-MIMO and D-MIMO, highlighting D-MIMO’s advantage.

In recent years, the significance of terahertz (THz) and (sub-)THz communications has grown substantially due to its promising trade-off between higher capacity compared to microwave-based communication and better resilience against weather dependent influences (e.g., fog and rain). While electronic and optoelectronic techniques have been extensively explored, each offering distinct advantages and limitations, they have predominantly been demonstrated and discussed as individual experiments, making performance comparison challenging. This paper addresses this gap by systematically benchmarking electronic and optoelectronic signal generation approaches under comparable conditions. Our experiments incorporate various receiver types, revealing that best performance is achieved by combining optoelectronic signal generation techniques at the transmitter in combination with an all-electric intradyne receiver. This results in a remarkable line rate of 200 Gbit/s over a distance of 52 m. To our knowledge, this represents the highest line rate achieved for technically relevant transmission distances for indoor access or outdoor small cell networks.

This paper provides the details of a novel systematic design methodology for two-way in-phase filtering Gysel splitter/combiner networks with high selectivity, which finds application in high power amplifier modules. It simultaneously realizes a filtering function and a two-way splitter/combiner function. The proposed five-port filtering device, based on the Gysel topology, is transformed into a ring of coupled resonators. A rigorous coupling matrix describing the network is used to synthesize the integrated filtering and combining functions. This general network can be implemented in any of the available filter technologies. In this paper, a few design examples are provided, and a six-pole prototype utilizing compact combline coaxial resonators is demonstrated. The proposed design provides an integrated dual function module, reducing component counts and system complexity. A design was fabricated and tested demonstrating good experimental results.

Millimeter wave antenna arrays are essential components of modern communication and radar systems. To produce these devices in large quantities, manufacturers require fast and reliable measurement equipment. The measurement equipment needs to ensure the quality, interoperability, and adherence to regulatory norms of the produced devices. In this work, we present an active probe array structure (PAS), which enables fast, compact, and reliable over-the-air (OTA) measurements of radiation characteristics. No relative movement between the antenna under test (AUT) and the active PAS is required, making the system very suitable for cost-effective large-scale characterization and commercial production test scenarios. We demonstrate and discuss how a near-field (NF) OTA measurement performed by this active PAS system can be used to reconstruct the far-field (FF) antenna radiation behavior of AUTs using an NF to FF correlation approach.

We report on the successful implementation of a photonic-based beam steering approach for point-to-multipoint terahertz (THz) communications. The frequency-agile radiation properties of a THz leaky-wave antenna connected to a photodiode are utilized in the remote transmitter for generating multiple individually steerable THz beams. The approach benefits from the ultra-wide frequency tunability of optical heterodyne systems for frequency-agile THz beam steering. Moreover, the approach allows to exploit high performance and mature optical modulation techniques for generating THz beams with a high data capacity. In the THz receiver, a carrier frequency insensitive envelope THz detector based upon a single Schottky-barrier diode is used. In detail, THz communications in the 300 GHz band (WR3.4) with a maximum steering angle up to 90° is reported. Experimentally, for single steerable THz beam operation, a record high data rate of 35 Gbit/s at a wireless distance of 30 cm is achieved using two-level pulse amplitude modulation. Also, longer wireless distances up to 110 cm with 5 Gbit/s are demonstrated. Furthermore, point-to-multipoint THz communications is reported using two individually steerable THz beams carrying 10 Gbit/s and 5 Gbit/s over 70 cm and 50 cm, respectively.

This article deals with multilayer substrate integrated waveguide (SIW) six-port junctions with embedded carbon resistive films. SIW six-ports usually employ reactive power dividers, which degrade the amplitude and phase balance when the six-port is terminated with mismatched power detectors. The associated impairments are studied and two SIW six-port junctions with improved isolation and output matching are designed for K-/Ka-band applications to overcome these limitations. The proposed designs differ with respect to the configuration of the output ports making the underlying six-port topology applicable for different layout requirements. Measurements of the fabricated components validate the concept. The six-ports are compact, fully shielded and can be integrated in multilayer printed circuit boards.

This paper proposes an innovative hybrid package integration strategy compatible with silicon-based technologies. It is evaluated beyond 200 GHz by the integration of a WR3 back-to-back waveguide-to-suspended stripline transition designed in BiCMOS technology, relying on metallic split-block package and organic laminate substrate. Simulated insertion loss below 3 dB is observed in the 220–320 GHz frequency band, competing with reported traditional solutions using III–V substrates. The achieved performances lead to promising perspectives for low-cost silicon packaging solutions beyond 200 GHz.

This paper presents the radio frequency (RF) design and experimental validation of a multifunctional bandpass filtering (BPF) concept with center frequency tunability and RF codesigned isolator and impedance matching functionality. The multifunctional bandpass filter/isolator (BPFI) concept combines frequency-tunable reciprocal resonators and nonreciprocal frequency-selective stages (NFSs) to realize center frequency tunability and fully directional transfer characteristics. The NFS, as the core component of the BPFI concept, exhibits frequency-selective transmission response in the forward direction and signal cancellation in the reverse direction. Its tunability is achieved by combining a transistor-based network with a tunable capacitively loaded coupled-line section. Furthermore, the NFS facilitates matching of different source loads allowing for the BPFIs to be used as reconfigurable matching networks. For experimental validation, an NFS and two BPFIs were designed, manufactured, and measured at L band. Their features include (i) NFS: center frequency tuning from 1.55 to 1.9 GHz with maximum directivity from 20 to 52 dB and gain from 0.3 to 1.3 dB. (ii) BPFI (topology A): center frequency tuning from 1.52 to 1.9 GHz with maximum directivity from 20 to 44 dB and gain from −1.5 to −0.5 dB. (iii) BPFI (topology C): ability to match complex loads with 26 + j18 Ω and 26 − j14 Ω.

Surface acoustic wave (SAW) resonator-based compact multi-band bandpass filters (BPFs) with quasi-elliptic transfer functions (TF) and reconfigurable reflective or quasi-reflectionless characteristics are reported. They utilize bandpass-type multi-resonant acoustic wave lumped resonator (AWLR) stages, shaped by multiple in-parallel cascaded distinct SAW resonators and one lumped-element (LE) inductor. By incorporating resistively-terminated bandstop-type AWLR stages at the Radio Frequency (RF) input/output, their power reflection response can be tailored to be quasi-reflectionless. The multi-band BPF can be expanded to TF with: i) a high number of passbands by increasing the number of the acoustic wave resonators (AWRs) in the AWLR stages, and ii) higher selectivity by cascading bandpass-type AWLRs stages using impedance inverters, and iii) symmetric quasi-reflectionless characteristics. For N in-series cascaded stages, each comprising K distinct AWRs, K passbands with enhanced fractional bandwidth (FBW) can be created, with overall TF having N•(K) poles and N•(K+1) transmission zeros (TZs). The operating principles of the multi-band BPF concept are provided through detailed design examples. The concept is demonstrated through detailed design examples, with three multi-band BPF prototypes manufactured and characterized, exhibiting dual-/triple-band centered between 1029.8 and 1039.9 MHz, FBWs> 0.4kt2, and effective Q-factors> 5,000. The quasi-reflectionless prototype showed a maximum reflection of -11.5 dB.

With the emerging developments in millimeter-wave/5G technologies, the potential for wireless Internet of things devices to achieve widespread sensing, precise localization, and high data-rate communication systems becomes increasingly viable. The surge in interest surrounding virtual reality (VR) and augmented reality (AR) technologies is attributed to the vast array of applications they enable, ranging from surgical training to motion capture and daily interactions in VR spaces. To further elevate the user experience, and real-time and accurate orientation detection of the user, the authors proposes the utilization of a frequency-modulated continuous-wave (FMCW) radar system coupled with an ultra-low-power, sticker-like millimeter-wave identification (mmID). The mmID features four backscattering elements, multiplexed in amplitude, frequency, and spatial domains. This design utilizes the training of a supervised learning classification convolutional neural network, enabling accurate real-time three-axis orientation detection of the user. The proposed orientation detection system exhibits exceptional performance, achieving a noteworthy accuracy of 90.58% over three axes at a distance of 8 m. This high accuracy underscores the precision of the orientation detection system, particularly tailored for medium-range VR/AR applications. The integration of the FMCW-based mmID system with machine learning proves to be a promising advancement, contributing to the seamless and immersive interaction within virtual and augmented environments.

Future communication and radar sensing systems will require synchronization methods which are more versatile in terms of the systems involved in the synchronization process. We present an over-the-air frequency synchronization algorithm based on the standard and the generalized Kuramoto model which uses continuous wave (CW) signals. In contrast to other approaches, all nodes of the network participate equally, and synchronization can even be achieved in presence of a non-cooperative node. By changing the parameters of the radar or by modifying the synchronization algorithm, synchronization accuracy can be adjusted as well. All claims are supported by measurements conducted with CW radars. It will be demonstrated that our algorithm enables synchronization accuracies down to 1.92 ppb and thus could provide sufficient accuracy for velocity measurements on pedestrians.

In this work, we develop a method for robust single-cycle measurement velocity vector estimation for automotive radar. Building upon our previous work, we introduce a methodology that leverages spatial diversity for accurate estimation of the velocity vector of targets in the medium to close ranges. We extend our initial conceptual framework, addressing limitations from our first approach and proposing necessary enhancements for real-world applicability. Our improved process excels in target separation, identification, and velocity vector estimation, proving effective across various scenarios and minimizing errors. The system, tested on pedestrians and metal targets, presents a promising avenue for exploring its performance with varying target sizes. Simultaneously, our in-depth study on Doppler-multiplex modulation reveals new relevant constraints, prompting a modulation change for improved response separation. Despite the necessity of increasing module numbers for enhanced performance, our structured approach to target itemization and classification positions our methodology as a valuable framework for future systems, offering a comprehensive solution to diverse challenges in target estimation and classification within the automotive landscape.