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This article presents the design and implementation of W-band transmitter (TX) and receiver (RX) phased-array antennas, which leverage CMOS and printed circuit board (PCB) technologies to integrate the phased-array antennas with eight-channel beamforming ICs. The beamforming IC applies the variable gain amplifier (VGA) with fractional bits and the vector-modulated variable gain phase shifter (VGPS) for wide range and high precision of gain and phase shifting, providing moderate power gain. The phased-array board consists of 384 TX and 384 RX antenna elements, along with 48 TX and 48 RX beamforming ICs. It also incorporates Wilkinson power dividers/combiners, a power management system, and a beamforming control module, all integrated into a cost-effective multi-layer PCB. Fabricated in 65-nm bulk CMOS, the IC achieves 3° RMS phase error for phase shifting and 0.5 dB RMS gain error for gain shifting, ensuring high precision of antenna pointing. The over-the-air (OTA) measurement of the proposed W-band phased-array antennas achieves a 64-QAM constellation with a symbol rate of 3.5 GS/s, resulting in raw data rates of 21 Gb/s. [ABSTRACT FROM AUTHOR]

Deep geothermal drilling is a necessary technological stage to produce renewable energy by "enhanced geothermal systems" everywhere. However, the high cost and complexity of deep drilling through hard rock formations is a major barrier to its commercialization. One approach to reach affordability and reduce the cost of deep drilling is to use millimeter-wave (mmw) gyrotron radiation to melt or vaporize rocks. In this paper, the results of an experimental study of mmw radiation absorption by hard rocks are presented. Electromagnetic attenuation and reflection were measured in W-band at frequencies from 75 to 110 GHz in eight rock samples from six different geological formations originated in Israel. The results show that the mmw radiation absorption in hard rocks ranges from 90 to 99% per centimeter. The absorption varies slightly with rock type and is relatively independent of frequency but has reached higher values at the upper W band for all samples. The study suggests that high-power mmw radiation is a promising technology for deep geothermal drilling. The results of this experiment, attenuation, and reflection of W-band radiation in hard rocks provide valuable information for the design and optimization of mmw-based drilling systems, and will support the design and optimization of gyrotron based hard rock drilling equipment for geothermal applications. [ABSTRACT FROM AUTHOR]

This paper proposes a W-band frequency-modulated continuous-wave (FMCW) radar system composed of a 1-channel transmitter and a 16-channel receiver in a thinned array configuration. The transmitter and receiver chips were custom-designed using a 28 nm CMOS process, and the antennas were implemented using a substrate-integrated waveguide (SIW) structure. The experimental results demonstrated that a target with a radar cross section (RCS) of 11.7 dBsm was detected at a distance of 18 m with a signal-to-noise ratio (SNR) of 37.5 dB. In addition, an azimuth angle resolution of 4.87° for a 7 dB null criteria was confirmed for two objects located 4 m away. [ABSTRACT FROM AUTHOR]

A vacuum window used for W-band traveling wave tube (TWT) featured with excellent thermal capacity, low insert loss, and wide operation band is investigated in this paper. The window sheet material is upgraded to single crystal diamond. The microwave characteristic simulation, thermal analysis, and the structure design are deeply and successively carried out before the fabrication. The microfabrication of the window frame, the produce and surface treatment of the diamond sheet, the metallization, and the vacuum brazing are demonstrated. According to the experimental test results with a vector network analyzer, the S21 parameters are larger than − 0.8 dB and S11 parameters are lower than − 18 dB in a 25 GHz with more than 25% relative bandwidth, which shows great advantages of the single crystal diamond vacuum window in millimeter wave and even terahertz spectrum. [ABSTRACT FROM AUTHOR]

A staggered vane-shaped slot-line slow-wave structure (SV-SL SWS) for application in W-band traveling wave tubes (TWTs) is proposed in this article. In contrast to the conventional slot-line SWSs with dielectric substrates, the proposed SWS consists only of a thin metal sheet inscribed with periodic grooves and two half-metal enclosures, which means it can be easily manufactured and assembled and has the potential for mass production. This SWS not only solves the problem of the dielectric loading effect but also improves the heat dissipation capability of such structures. Meanwhile, the SWS design presented here covers a −15 dB S11 frequency range from 87.5 to 95 GHz. The 3-D simulation for a TWT based on the suggested SWS is also investigated. Under dual-electron injection conditions with a total voltage of 17.2 kV and a total current of 0.3 A, the maximum output power at 90 GHz is 200 W, with a 3 dB bandwidth up to 4 GHz. With a good potential for fabrication using microfabrication techniques, this structure can be a good candidate for millimeter-wave TWT applications. [ABSTRACT FROM AUTHOR]

Summary: This article demonstrates a novel type of series‐fed planar antenna array for a W‐band (70 GHz) application. The proposed architecture is a 5‐element antenna array with 10 numbers of gap‐coupled parasitic patches in microstrip configuration over a thin, flexible and bio‐compatible substrate named LCP (liquid crystal polymer). A detailed design methodology with all fabrication constraints has been elaborated on here. Full wave analysis of the whole structure has been carried out in the FEM‐based 3D electromagnetic (EM) solver ANSYS HFSS Suite V.19.2. Parametric simulations were studied to achieve the optimized values of all design parameters. Further, an empirical electrical equivalent circuit model is proposed for the antenna array, and it was validated with the simulation results obtained from the FEM solver. Two prototypes have been fabricated, and measurements were carried out to fetch all the designed antenna parameters. The proto version of the antenna offers peak directive gain of about 19 dBi with better than 22 dB of return loss and 80% radiation efficiency for the frequency range of 67–85 GHz. Experimental and simulated results closely match each other. Small deviations are attributed to practical imperfections incurred by fabrication tolerances, measurement inaccuracies, testing, assembly‐related issues and so forth. Finally, the current research work is compared with the recently reported literature. [ABSTRACT FROM AUTHOR]

In this article, waveguide dual-band filter and diplexer working on W-band are synthesized through cascading mixed TE301- and TE102-mode cavities as well as TE101-mode resonators. Based on the discussion of top resonance modes in single cavity, the TE301&TE102 dual-mode resonator which features oversized dimension, technological insensitivity and high Q-factor is the strong candidate for designing high-frequency filters and diplexers. For dual-band filter, such dual-mode resonator can be shared by both bands as T-junction, and each band can be independently controlled. Besides, a W-band diplexer is proposed based on the analogous method. Two extra zeros have also been generated for each channel with adopting the singlet concept. Finally, the filter and diplexer prototypes are machined by CNC-milling. The filter has obtained 3-dB FBWs of 4% (86.7–90.2 GHz) and 6.3% (96.7–103 GHz), low insertion losses (ILs) of -0.9 dB and -0.5 dB, as well as less than -16 dB return loss, respectively. The diplexer has achieved 3-dB FBWs of 4.9% (86.3–90.6 GHz) and 6.5% (96.9–103.4 GHz), low ILs of -0.7 dB and -0.4 dB, high insolation with more than 40 dB, respectively. All the experimental results including transmission zeros on out-of-band are very close to the simulations in the full band. The performance of dual-band filter and diplexer is highlighted comparing with the reported ones too. [ABSTRACT FROM AUTHOR]

A wideband multi-polarized square-horn antenna based on an orthogonal mode transducer (OMT) is developed for working in the whole W-band in this paper. The designed antenna is capable of radiating multiple polarization modes as horizontal polarization (HP) and vertical polarization (VP) when as single-port excitation and left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) when as dual-port excitation, owing to the characteristic of the OMT with the transmitting of orthogonally polarized waves. A CNC-layered fabrication approach is proposed, which means that the antenna prototype integrating with a Boifot-type OMT, turning waveguide, twisting waveguide and phase shifter is divided into three layers along the vertical direction to be fabricated based on computerized numerical control (CNC) technology. In the design, the turning waveguide and twisting waveguide are employed to achieve plane consistency of the antenna branch ports. Furthermore, a phase shifter is designed to compensate the orthogonally polarized waves, which can keep the phase of the orthogonally polarized waves consistent in a wideband frequency range from 75 GHz to 110 GHz. A prototype is fabricated and measured to verify the performance of the proposed multi-polarization antenna, and the measured results agree well with the simulation ones. In the whole W-band, the value of return loss is better than 10 dB of all polarization modes, and the value of AR of the LHCP and RHCP is below 3.5 dB. The maximum gain of the antenna reaches up to 18.8 dBi at 110 GHz. In addition, regarding the layered structure, the possible layered assembly error analysis is discussed, which verifies the feasibility of the layered machining for this antenna. [ABSTRACT FROM AUTHOR]

This study entailed the development of a complementary metal–oxide–semiconductor (CMOS) ultra-wideband (UWB) pulse generator with an inherent binary phase-shift keying (BPSK) modulation technique. The BPSK modulation technique in a pulsed oscillator has been proposed by the author in previous studies on K-band application. In this study, a W-band CMOS UWB pulse generator was developed using this technique. The W-band UWB pulse generator was implemented on a 0.13-μm CMOS chip with an active area of 0.08 mm² . The output spectrum exhibited a −10 dB bandwidth of 2.8 GHz, ranging from 75.1 to 77.9 GHz. The energy consumption was 45 pJ per pulse with a peak output power of −2.6 dBm [ABSTRACT FROM AUTHOR]

The number of environment-detecting sensors inside cars continuously increases, to enable failsafe autonomous driving. With more sensors, the probability of performance degrading interferences increases. A promising solution to the interferences is orthogonal frequency division multiplex (OFDM) radar. Due to the complex modulation scheme, the analog front end, especially the power amplifier in the transmitter, has to deal with a high peak-to-average power ratio. Therefore, conventional amplifiers have to be operated in power back-off to maintain linear operation at the drawback of reduced power-added efficiency. To mitigate this problem, a Doherty power amplifier for an automotive radar transceiver is proposed. In this work, we present a design methodology for an integrated Doherty amplifier for automotive radar applications, focussing on the theory of operation by analyzing transistor-level simulations. Small- and large signal simulations analyze the concept of load modulation for a Doherty amplifier in the automotive frequency band from 76--81 GHz. Using a fully differential transmission-line-based approach, we showcase the superior performance of an automotive Doherty amplifier over an conventional state-of-the-art reference amplifier. In measurements, the proposed Doherty amplifier achieves a saturated output power of 17.2 dBm with a peak power-added efficiency of 11.6%. When operating in 6 dB back-off, the PAE still amounts to 6.1%. Thereby we propose to improve conventional automotive power amplifiers by incorporating them into a Doherty amplifier.

With increasing interest in the W-band, there is growing focus on parabolic reflector antennas that are known for efficiently inducing high-gain radiation characteristics. There is particular focus on parabolic antennas with diverse defocus-fed applications, including monopulse tracking, multi-beam formation using multiple feeds, and aperture-shared antennas for multi-band operation. Thus, a new simplified method is presented in this paper to analyze the radiation characteristics of defocus-fed parabolic antennas. The presented method is based on the discrete division of a parabolic reflector surface and considers only simplified wave propagation theory and the effect of the scalar function pattern from the feeder. Additionally, array theory is exclusively applied for the analysis of radiation characteristics. Therefore, the presented method uses a very simplified formula to calculate the radiation characteristics of a defocused parabolic reflector antenna. The performance of the presented method was evaluated by comparing the results with commercial EM tools. The results of the analysis confirm the applicability of the presented method for the analysis of defocus-fed parabolic antennas. [ABSTRACT FROM AUTHOR]

This letter proposes a W‐band multimode monopulse horn (MMH) feed to improve the total efficiency (TE) of the reflector antenna. The feed consists of a MMH and a single‐layer comparator. The MMH utilizes one pyramidal horn and four rectangular waveguides (RWGs) for feeding. The eight electric modes required in the MMH yield excellent sum and difference patterns. The impact of unwanted modes is suppressed using a 90° phase difference approach. The comparator contains four novel 3 dB couplers and E‐plane RWGs, providing low loss and high multiport transmission performance. The MMH feed has been fabricated, tested, and applied to a Cassegrain antenna. The measured maximal TE for the Cassegrain antenna between 90 and 97 GHz is 54.9%. The realized gain of the sum beam is 40.3 dBi at 93.5 GHz. The null depths of difference beams in the azimuth and elevation planes are about −37.7 and −29.1 dB, respectively. [ABSTRACT FROM AUTHOR]

This article presents a W‐band three‐layer reflectarray antenna that can be easily fabricated using printed circuit board (PCB) process. The proposed reflectarray element is composed of substrate integrated waveguide (SIW) structure and slot‐coupled patch. By controlling the length of SIW in each element, the compensation phases required for the reflectarray to generate focused beam at in‐band frequencies are realized. However, at the out‐of‐band frequencies, the elements fail to provide the required compensation phases as the incident electromagnetic wave cannot couple to the SIW. Thus, filtering performance is realized. A circular aperture prototype reflectarray comprising of 5024 elements are employed to yield a high‐gain narrow beam. The measured results show that the proposed reflectarray antenna attains a peak gain of 40.5 dB at 94 GHz with aperture efficiency of 41.3%, and out‐of‐band suppression higher than 22 dB. [ABSTRACT FROM AUTHOR]

The existing frequency bands, such as the C-band and L-band, are becoming increasingly crowded and cannot meet the growing demand for high-speed data rate services. To overcome spectrum congestion, meet future business needs, and overcome the bottlenecks of traditional electronic methods, we have modified an approach for generating W-band mm-wave signals with octupling frequency without the need for an optical filter. One integrated modulator consisting of two push-pull Mach-Zehnder modulators (MZM) in series is employed to achieve W-band signal generation. The octupling frequency signal generation depends on ±4th optical sidebands to beat frequency in the photodetector. For capturing ±4th optical sidebands, the bias point of the two push-pull MZMs needs work at the peak point, and the modulation index of the two MZMs should be simultaneously set to 2.4. We have conducted detailed mathematical derivation and computer simulation for the scheme, demonstrating its correctness. The results show that the optical sideband suppression ratio is not less than 45.73 dB, and the RF sideband suppression ratio can reach 37.64 dB. [ABSTRACT FROM AUTHOR]

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This letter presents an ×8 frequency multiplier for the W‐band wireless satellite communication in the 65 nm complementary metal‐oxide‐semiconductor process. To reduce the power consumption, the proposed frequency multiplier employs only one driven amplifier and three stages of doublers. All doublers adopt balanced structures to increase their robustness. The output buffer is introduced to ameliorate the impedance matching of output port so that the output power of the proposed ×8 frequency multiplier can achieve 4.63 dBm. Through the special design of the interstage impedance matching circuit, the relative 3‐dB bandwidth of the proposed frequency multiplier is over 25% (from 74.8 to 96.2 GHz). The chip also has a small size and low power consumption, which is 1.37 × 0.51 mm2 and 125 mW, respectively. [ABSTRACT FROM AUTHOR]

A W-band eight-way radial-waveguide power divider with low insertion loss and high power-combining efficiency has been proposed in this paper. The coaxial waveguide has been utilized in the eight-way radial-waveguide power divider as a transition from the rectangular waveguide to radial waveguide. The structure of the coaxial mode transition from the rectangular waveguide to radial waveguide is simple, and its electrical length is much shorter than others' mode transition, which results a low insertion loss and high power power-combining efficiency. The microwave signal was inputted from the rectangular waveguide (TE10 mode) and transmitted to the radial waveguide (cylindrical TEM mode) through the coaxial waveguide (TEM mode). Finally, the signal in radial waveguide is divided into eight ways with equal power and equal phase by the eight output standard rectangular waveguide. This all-metal waveguide multi-way power divider demonstrates the advantages of easy design and fabrication, large and arbitrary number of combination ports, and a simple and compact structure. To verify the presented power divider, a W-band eight-way power divider is fabricated and measured. The measured results show that, over the frequency range from 82 to 110 GHz, the measured input return loss is greater than 15 dB, the measured average insertion loss is about 9.4 ± 0.5 dB, the phase imbalance is about ± 5°, and the power-combining efficiency is about 91%. [ABSTRACT FROM AUTHOR]

This article reports a two-stage differential structure power amplifier based on a 130 nm SiGe process operating at 77 GHz. By introducing a tunable capacitor for amplitude and phase balance at the center tap of the secondary coil of the traditional Marchand balun, the balun achieves amplitude imbalance less than 0.5 dB and phase imbalance less than 1 degree within the operating frequency range of 70–85 GHz, which enables the power amplifier to exhibit comparable output power over a wide operating frequency band. The power amplifier, based on a designed 3-bit digital analog convertor (DAC)-controlled base bias current source, exhibits small signal gain fluctuation of less than 5 dB and saturation output power fluctuation of less than 2 dB near the 80 GHz frequency point when the ambient temperature varies in the range of −40 °C to 125 °C. Benefiting from the aforementioned design, the tested single-path differential power amplifier exhibits a small signal gain exceeding 16 dB, a saturation output power exceeding 18 dBm, and a peak saturation output power of 19.1 dBm in the frequency band of 70–85 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of an LO chain implemented using the CMOS 65 nm bulk process. The LO chain was fabricated for driving the short-range radar IQ mixer in the 77∼81 GHz band. The LO chain comprised a poly phase filter (PPF), driver amplifiers to compensate for PPF losses, and a 3-bit 7-dB attenuator to ensure the appropriate power conditions. Measurement results indicated that the maximum gain within the target band was 8 dB, and the gain and phase difference between the IQ outputs were 0.5 dB and 74°, respectively. The LO chain consumed 74 mW of power at 1 V, and the size of the fabricated chip was 1.027×0.45 mm², including RF and DC pads. [ABSTRACT FROM AUTHOR]

In this study, a dual-band low-noise amplifier (LNA) was implemented by applying a transformer-based neutralization technology to the W-band. Incorporating the neutralization technique was difficult owing to performance degradation in the W-band. However, circuit performance was enhanced thanks to the layout optimization of transformer-based neutralization networks, and the improved operation was confirmed in the W-band. The neutralization technique was implemented in four stages with a 0.1-μm gallium arsenide (GaAs) pseudomorphic high-electron-mobility-transistor monolithic microwave integrated circuit LNA. The LNA showed small signal gains of 20.3 dB and 21.7 dB and noise figures of 5.0 dB and 6.4 dB (at 84 GHz and 96 GHz, respectively) while consuming 46 mW from a 1-V supply.

A staggered vane-shaped slot-line slow-wave structure (SV-SL SWS) for application in W-band traveling wave tubes (TWTs) is proposed in this article. In contrast to the conventional slot-line SWSs with dielectric substrates, the proposed SWS consists only of a thin metal sheet inscribed with periodic grooves and two half-metal enclosures, which means it can be easily manufactured and assembled and has the potential for mass production. This SWS not only solves the problem of the dielectric loading effect but also improves the heat dissipation capability of such structures. Meanwhile, the SWS design presented here covers a −15 dB S11 frequency range from 87.5 to 95 GHz. The 3-D simulation for a TWT based on the suggested SWS is also investigated. Under dual-electron injection conditions with a total voltage of 17.2 kV and a total current of 0.3 A, the maximum output power at 90 GHz is 200 W, with a 3 dB bandwidth up to 4 GHz. With a good potential for fabrication using microfabrication techniques, this structure can be a good candidate for millimeter-wave TWT applications.

This paper discusses the design of a W-band down-conversion mixer, fabricated using a 65-nm bulk CMOS process. The mixer employs a passive double-balanced structure, resulting in no power consumption. It includes LC matching circuits for RF and LO input voltage amplification via resonance and RC filter circuits for precise IF signal separation. The manufactured mixer measured 0.614×0.25 mm², including RF and DC pads. Measurement results showed input return losses of more than 8 dB, a maximum conversion gain of －5.5 dB, and RF-IF isolation of 37.3 dB at 77–81 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the design of a driving amplifier intended for use in W-band RFICs. The amplifier adopts a differential two-stage common-source configuration to ensure robust output power. Furthermore, it has been enhanced through the incorporation of a neutralized capacitor to improve stability and maximize gain. The driving amplifier was fabricated using a 65-nm bulk CMOS process for validation. The measured performance of the amplifier demonstrated characteristics, including an input/output return loss exceeding 10 dB and a peak gain of 14.1 dB, achieved within the frequency range of 77∼88 GHz. The power consumption of the amplifier was only 34 mW at a voltage of 1 V, and it exhibited an OP1dB of 3.8 dBm. The size of the driving amplifier, excluding DC and RF pads, was 0.401×0.14 mm². [ABSTRACT FROM AUTHOR]

We propose a W-band circularly polarized reflectarray antenna in this article, which contains a single-layer reflectarray and a linearly polarized horn feed. To realize the proposed antenna, we designed a novel W-band multi-resonant element containing a Rogers RT5880 substrate with copper patches printed on its both surfaces. Then, a circular reflectarray with 12.25 λ0 (39.1 mm) aperture diameter was designed based on the proposed multi-resonant element, whose center frequency is 94 GHz. We further fabricated the proposed circular reflectarray and tested its performance. In the measured results, we can see that the obtained 1 dB gain bandwidth is 19.1% (91~109 GHz) and the obtained 2 dB gain bandwidth can reach as wide as 27.6% (89~115 GHz). Moreover, the 3 dB axial ratio bandwidth is 13.8% (89~102 GHz). The measured gain of our proposed reflectarray antenna at 94 GHz is 29.1 dBi and the corresponding aperture efficiency can reach as high as 52.0%. Those results show that our proposed antenna may be prospective in wireless communication applications due to its strengths in broadband and high aperture efficiency. [ABSTRACT FROM AUTHOR]

Radio telescopes are used by astronomers to observe the naturally occurring radio waves generated by planets, interstellar molecular clouds, galaxies, and other cosmic objects. These telescopes are equipped with radio receivers that cover a portion of the radio frequency (RF) and millimetre-wave spectra. The Sardinia Radio Telescope (SRT) is an Italian instrument designed to operate between 300 MHz and 116 GHz. Currently, the SRT maximum observational frequency is 26.5 GHz. A feasibility study and preliminary tests were performed with the goal of equipping the SRT with a W-band (84–116 GHz) mono-feed radio receiver, whose results are presented in this paper. In particular, we describe the adaptation to the SRT of an 84–116 GHz cryogenic receiver developed by the Institute de Radio Astronomie Millimétrique (IRAM) for the Plateau de Bure Interferometer (PdBI) antennas. The receiver was upgraded by INAF with a new electronic control system for the remote control from the SRT control room, with a new local oscillator (LO), and with a new refrigeration system. Our feasibility study includes the design of new receiver optics. The single side band (SSB) receiver noise temperature measured in the laboratory, Trec ≈ 66 K at 86 GHz, is considered sufficiently low to carry out the characterisation of the SRT active surface and metrology system in the 3 mm band. [ABSTRACT FROM AUTHOR]

This paper presents the design of W-band Wilkinson power divider using 65 nm bulk CMOS process. In this design, the quarter-wavelength (λ/4) transmission line was replaced with a lumped element, and a CRC structure was applied to the isolation network circuit. In addition, a metal wall was installed between the two output lines to enhance isolation. This power divider had a maximum insertion loss of 1.93 dB and a minimum isolation of 13.3 dB in the 75~110 GHz band. The return loss was more than 7.2 dB, and the size of the core was 0.2×0.12 mm². [ABSTRACT FROM AUTHOR]

A wideband multi-polarized square-horn antenna based on an orthogonal mode transducer (OMT) is developed for working in the whole W-band in this paper. The designed antenna is capable of radiating multiple polarization modes as horizontal polarization (HP) and vertical polarization (VP) when as single-port excitation and left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) when as dual-port excitation, owing to the characteristic of the OMT with the transmitting of orthogonally polarized waves. A CNC-layered fabrication approach is proposed, which means that the antenna prototype integrating with a Boifot-type OMT, turning waveguide, twisting waveguide and phase shifter is divided into three layers along the vertical direction to be fabricated based on computerized numerical control (CNC) technology. In the design, the turning waveguide and twisting waveguide are employed to achieve plane consistency of the antenna branch ports. Furthermore, a phase shifter is designed to compensate the orthogonally polarized waves, which can keep the phase of the orthogonally polarized waves consistent in a wideband frequency range from 75 GHz to 110 GHz. A prototype is fabricated and measured to verify the performance of the proposed multi-polarization antenna, and the measured results agree well with the simulation ones. In the whole W-band, the value of return loss is better than 10 dB of all polarization modes, and the value of AR of the LHCP and RHCP is below 3.5 dB. The maximum gain of the antenna reaches up to 18.8 dBi at 110 GHz. In addition, regarding the layered structure, the possible layered assembly error analysis is discussed, which verifies the feasibility of the layered machining for this antenna.

Small insect detection presents a significant challenge in various fields, including agriculture, entomology and environmental monitoring. Conventional radar systems often struggle to detect these tiny targets due to their low radar cross-sections and erratic flight patterns. This article explores the innovative approach of utilizing the shadow effect in W-band pulsed radar for enhanced small insect detection. We discuss the principles behind W-band radar, the shadow effect phenomenon and its application in insect detection. Additionally, we analyze the potential benefits, challenges and future prospects of this technique. Detecting small insects using radar technology is crucial for numerous applications, such as pest management in agriculture, ecological studies and surveillance of disease vectors. However, the conventional radar systems encounter limitations when it comes to effectively detecting these tiny targets due to their small size and unpredictable movement patterns. The utilization of W-band pulsed radar, coupled with the shadow effect phenomenon, offers a promising solution to this longstanding challenge. [ABSTRACT FROM AUTHOR]

Ground-based radar interferometry is capable of measuring target displacement to sub-mm accuracy. W-band ground-based radar has recently been investigated as a potential application for structural health monitoring. On the other hand, the application of W-band ground-based radar for natural slope monitoring is considered in this study due to its advantages in portability and recent cost-effective solutions. In radar interferometry, atmospheric phase screen (APS) is the most relevant phase disturbance that should be corrected for accurate displacement measurement. However, the APS effects in W-band radar interferometry have rarely been discussed. In this context, we study and evaluate the impacts of APS and its potential correction methods for 79 GHz ground-based radar interferometry using multiple-input and multiple-output (MIMO) radar. This paper presents an experimental investigation of a 79 GHz radar system using two types of field experiments conducted in an open flat field and a quarry site. In addition to the W-band radar system, a Ku-band (17 GHz) ground-based synthetic aperture radar (GB-SAR) system was jointly tested to compare different operating frequency bands. The result confirmed the accurate displacement estimation capability of the 79 GHz radar with an appropriate APS correction. [ABSTRACT FROM AUTHOR]

We have experimentally implemented a photonics-aided large-capacity fiber-mm-wave wireless communication system employing a simple dual-polarized single-input single-output (SISO) wireless based on polarization multiplexing at the W-band. To compare the performance of different algorithms, 18G-baud, and 35G-baud 16-level quadrature-amplitude-modulation (16QAM), probabilistically shaped 16QAM (PS-16QAM), 64QAM and PS-64QAM signal using different carrier phase recovery (CPR) algorithms are transmitted in the system. Moreover, we compare the Viterbi–Viterbi (VV), improved new algorithm based on VV (NVV), blind phase search (BPS), and two-stage BPS algorithms' computational complexity to better compare different algorithms. Using the experiment result, we can demonstrate that the BPS algorithm is about half a magnitude better than the NVV algorithm for PS-QAM signals, while the NVV algorithm has the lowest computational complexity. Additionally, we also achieve error-free wireless transmission at a net data rate of 324.1 Gb/s with the bit error ratio (BER) below the forward-error correction (FEC) threshold of 1 × 10−2 assuming soft-decision forward-error correction (SD-FEC) when using the BPS algorithm. [ABSTRACT FROM AUTHOR]

A 94 GHz pulse Doppler solid-state millimeter-wave cloud radar (MMCR), Tianjian-II (TJ-II), has been developed. It reduces the size and cost using a solid-state power amplifier (SSPA) and a single antenna. This paper describes the system design, including hardware and signal processing components. Pulse compression, segmented pulse, and dual pulse repetition frequency (PRF) technologies are employed to overcome the limitations imposed by the low power of the SSPA and the high frequency of 94 GHz. The TJ-II also features a dual-polarization, high-gain antenna for linear depolarization ratio detection and a time-division receive channel to improve channel consistency and save on costs. To achieve high flexibility and low interference in signal transmission and reception, the TJ-II uses software-defined radio technology, including direct digital synthesis, digital downconversion, and bandpass sampling. A series of Doppler power spectrum processing methods are proposed for detecting weak cloud signals and improving scene adaptability. [ABSTRACT FROM AUTHOR]

Large radio and mm–wave telescopes use very sensitive detectors requiring cryogenic cooling to reduce detector noise. Pulse Tubes (PT) cryocoolers are widely used to reach temperatures of a few K, defining the base temperature of further sub–K stages. This technology represents an effective solution for continuous operation, featuring high stability and reduced vibration levels on the detectors. However, the compressor used to operate the PT is a significant source of microphonics and electrical noise, making its use at the focus of large steerable telescopes not advisable. This calls for long flexible helium lines between the compressor, operated at the base of the radio telescope, and the cold–head, mounted in the receivers cabin with the receiver detectors. The distance between the receiver cabin and the base can be >100 m long for large radio telescopes. In the framework of our development of the MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements kids (MISTRAL), a W–band camera working at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope (SRT) with an array of Lumped Elements Kinetic Inductance Detectors (LEKID), we have developed a cryogenic system based on a PT refrigerator as the first cooling stage. Here we describe the MISTRAL cryogenic system and focus on the validation of the use of a commercial PT Cryocooler with 100 m helium lines running from the cold head to the compressor unit. The configuration allows us to operate the 0.9 W PT reaching below 4.2 K with 0.5 W dissipation. [ABSTRACT FROM AUTHOR]

This article presents a high-efficiency circularly polarized slotted waveguide leaky wave antenna for the W band frequency range. The wall thickness of the slotted waveguide leaky wave antenna containing the radiating slots is tuned to optimize the overall antenna performance. A thin dielectric layer with an array of metallic patches has been used as a linear-to-circular polarization converter. The fabrication challenges of the W band antenna have been overcome by CNC milling machines which provide a high degree of precision and accuracy. The gain of the prototype antenna is above 20 dBi in the intended operating band from 92 GHz to 98 GHz. Furthermore, the antenna provides an average half-power beamwidth (HPBW) of 3.2° in the elevation plane and a cross-polarization level below -18 dB in the main beam direction. The combination of its robust design, reliable fabrication, simple configuration, and superior performance makes the proposed antenna a strong candidate for various W band applications.

In this paper, a W-band single-layer reflectarray antenna is proposed with the advantages of broadband and high aperture efficiency. A novel dual rotation-symmetry windmill element is designed in the W-band, which consists two layers of copper patches printed on a Rogers RT5880 substrate. Based on the analysis of the proposed metasurface element, a square reflectarray with $13.85\lambda _{0}$ (44.2 mm) aperture diameter at 94 GHz center frequency was designed, fabricated and measured. The designed reflectarray antenna shows a 1-dB gain bandwidth of 25.5% (89-113 GHz) in the W-band. Moreover, the measured gain is 31.1 dBi at 94 GHz and the maximum aperture efficiency is 53.4%. The result shows that the proposed design has prospects in wireless communication applications.

In this study, a W-band GaN single-pole single-throw (SPST) switch was designed. To realize the pass and isolation modes of the SPST switch, we proposed the design technique of a unit branch consisting of one transistor and one transmission. The characteristic impedance and length of the transmission line were determined by the impedance and the angle at which the straight line connecting the impedances of the on and off states of the transistor meets the real axis of the Smith chart. Using the design technique, the matching networks for the pass and isolation modes of the switch are concurrently completed. In order to improve the insertion loss and isolation characteristics of the switch, the size of the transistor and the number of unit branches were investigated. To verify the feasibility of the proposed design technique, we designed the W-band SPST switch using a 100 nm GaN HEMT process. The measured insertion loss and isolation were below 2.9 dB and above 23.5 dB, respectively, in the frequency range from 91 GHz to 101 GHz. [ABSTRACT FROM AUTHOR]

A W-band, high-gain, hybrid slot antenna array based on bulk silicon MEMS technology is proposed in this paper. The high-order-mode cavity is explored to excite the 2 × 2-slot basic unit, so as to reach the low-profile requirement of the bulk silicon MEMS process. To avoid the fragile structure of the large-scale antenna arrays based on the bulk silicon MEMS process, the ridge gap waveguide is employed to build the feed network for a large-scale array. A vertical transition between a rectangular waveguide and a ridge gap waveguide is designed to support the low-loss and low-cost assembling method between the radiation units and the feed network. An 8 × 8-slot hybrid antenna array is simulated and fabricated. The measured results show a relative bandwidth (VSWR < 2) of 8.1% with the first side-lobe level less than −11 dB over the frequency band of 91–97 GHz. A maximum gain of 26.1 dBi with the radiation efficiency of 65.2% is achieved. With high gain and high fabrication efficiency, the proposed hybrid slot antenna array would be valuable for W-band radar applications. [ABSTRACT FROM AUTHOR]

In this study, a 1 W W-band solid-state power amplifier (SSPA) was developed for application in a W-band compact pulse Doppler radar. The SSPA up-converted the X-band signal to a W-band signal with a multiplier (×8) and then amplified the high output using an amplifier. To apply the W-band compact radar, which transmits and receives signals using a single antenna, the SSPA noise was reduced by controlling the drain voltage of the SSPA according to the pulse repetition frequencies. The average power obtained was in the range of 31.7∼31.8 dBm, and stable operation was possible for more than 50 s. [ABSTRACT FROM AUTHOR]

This paper details the motivation and the status of a new satellite mission, which targets the in-orbit verification of a wide band satellite communication link, operating in the high millimeter-wave regime at 71–76 GHz. Under ideal weather conditions, data rates over 15 Gb/s in complex modulation formats are expected to be demonstrated in-orbit, while data rates over 6 Gb/s are still expected under adverse atmospheric and weather conditions. The scientific payload, hosted by a 6U-CubeSat platform, comprises a high-performance W-band transmitter with GaN-based solid state power amplifiers, an InGaAs-based low-noise receiver and a modern FPGA-based digital processing unit, realizing arbitrary waveform generation functionality and 4k image/video storage. The ground terminal employs a highly directive Cassegrain antenna with coarse GNSS and fine multi-mode RF tracking and a low-noise receiver together with an integrated high-speed digital processing and storage unit. [Display omitted] • Motivation and status of the high throughput novel communication satellite • In-orbit verification and demonstration of data downlink at 71–76 GHz • State-of-the-Art analog frontend payload in InGaAs and GaN technology • Miniaturized computationally powerful FPGA-based payload computer • Evaluation of the wave propagation impairments and signal degradation • Challenges of the RF tracking through multi-mode tracking [ABSTRACT FROM AUTHOR]

Summary: In this paper, a broadband superheterodyne receiver (RX) front‐end for millimeter‐wave (mm‐Wave) imaging radar is presented. Realized in 28‐nm CMOS technology, the proposed RX incorporates a wideband low‐noise amplifier (LNA), double‐balanced passive mixers for the dual down‐conversion, a differential power divider, a differential intermediate frequency filters, a current‐mode‐logic divider‐by‐2, and a local oscillator buffers. Wideband technique and layout optimization are taken into consideration in the RX. A four‐stage LNA is devised to realize the high gain and low noise figure (NF) with a common‐gate input stage and three pseudodifferential common‐source stages. Optimized transistor layout and capacitor neutralization technique are developed to improve gain and noise performance. Transformer‐based matching networks with the peak‐staggered technique are adopted in the LNA to achieve a flatter gain response with a wider bandwidth (BW). The passive double‐balanced mixers are implemented with a highly symmetrical layout for broadband down‐conversion. Simulation results show that the mm‐Wave RX front‐end exhibits a BW ranging from 90 to 115 GHz. The simulated NF of our RX is 4.7 dB at 86 GHz. With a supply voltage of 1 V, the presented RX consumes 88.2‐mW power and occupies a chip size of 1.6 × 0.5 mm2 including all the testing pads. The proposed RX is suitable for W‐band imaging systems. [ABSTRACT FROM AUTHOR]

With increasing interest in the W-band, there is growing focus on parabolic reflector antennas that are known for efficiently inducing high-gain radiation characteristics. There is particular focus on parabolic antennas with diverse defocus-fed applications, including monopulse tracking, multi-beam formation using multiple feeds, and aperture-shared antennas for multi-band operation. Thus, a new simplified method is presented in this paper to analyze the radiation characteristics of defocus-fed parabolic antennas. The presented method is based on the discrete division of a parabolic reflector surface and considers only simplified wave propagation theory and the effect of the scalar function pattern from the feeder. Additionally, array theory is exclusively applied for the analysis of radiation characteristics. Therefore, the presented method uses a very simplified formula to calculate the radiation characteristics of a defocused parabolic reflector antenna. The performance of the presented method was evaluated by comparing the results with commercial EM tools. The results of the analysis confirm the applicability of the presented method for the analysis of defocus-fed parabolic antennas.

This article reports a two-stage differential structure power amplifier based on a 130 nm SiGe process operating at 77 GHz. By introducing a tunable capacitor for amplitude and phase balance at the center tap of the secondary coil of the traditional Marchand balun, the balun achieves amplitude imbalance less than 0.5 dB and phase imbalance less than 1 degree within the operating frequency range of 70–85 GHz, which enables the power amplifier to exhibit comparable output power over a wide operating frequency band. The power amplifier, based on a designed 3-bit digital analog convertor (DAC)-controlled base bias current source, exhibits small signal gain fluctuation of less than 5 dB and saturation output power fluctuation of less than 2 dB near the 80 GHz frequency point when the ambient temperature varies in the range of −40 °C to 125 °C. Benefiting from the aforementioned design, the tested single-path differential power amplifier exhibits a small signal gain exceeding 16 dB, a saturation output power exceeding 18 dBm, and a peak saturation output power of 19.1 dBm in the frequency band of 70–85 GHz.

Abstract The development of multi‐pixel receivers on the millimetre‐wave and terahertz bands demands on the integration of key waveguide devices. In this paper, two waveguide bandpass filters operating at the W‐band are developed based on the layered integration architecture. First, the traditional fourth‐order waveguide filter is perpendicularly folded to realise dual‐layered arrangement, meanwhile a cross‐coupling between layers is introduced to obtain the standard quasi‐elliptical response. Then, two layered approaches including 5‐layer and 3‐layer are proposed to fabricate filter prototypes integrating with 90° curved waveguides based on the computer numerical control (CNC) technology. Finally, the measurement exhibits that both filters have achieved the 3 dB fractional bandwidth of 14.8% from 85 to 98.5 GHz, low insertion loss of 0.6 dB (5‐layer) and 0.4 dB (3‐layer), the return loss with better than 20 dB, as well as two obvious transmission zeros in the out‐of‐band. Besides, the layering error analysis and performance comparison of both filters are discussed, which verify the feasibility of the layered integration for CNC‐machined W‐band waveguide filters.

In this paper, a W-band 3D-printed bandpass filter is proposed. The use of higher-order TE10n modes in groove gap waveguide (GGW) technology is evaluated in order to alleviate the manufacturing requirements. In addition to the use of higher-order modes, the coupling between them is analyzed in detail to improve the overall fabrication robustness of the component. This allows the implementation of narrow-band filters operating at millimeter-wave frequency bands (or above), which usually demand complex manufacturing techniques to provide the high accuracy required for this kind of devices. In order to show the applicability of the proposed method, a narrow-band 5th-order Chebyshev bandpass filter centered at 94 GHz, which can be easily fabricated by state-of-the-art stereolithographic (SLA) 3D-printing techniques followed by silver coating, is shown. Excellent measured performance has been obtained. [ABSTRACT FROM AUTHOR]

In this paper, a novel wideband transition from a laminated waveguide (LWG) to an air-filled rectangular waveguide (RWG) is proposed for millimeter-wave integration solutions based on multilayer low-temperature co-fired ceramic (LTCC) technology. The integrated transition cavity is divided into several resonators by introducing five grounded via holes. Due to the magnetic wall existing in the symmetry plane, the equivalent circuit of the proposed transition can be simplified as a three-pole filter model to explain the working mechanism with wideband performance. A W-band integrated LWG-to-RWG transition is designed as an example using LTCC technology. Two back-to-back prototypes with different lengths are fabricated and measured. A measured 25.7% bandwidth from 76 GHz to 101 GHz can be achieved for return loss better than 14 dB. The average insertion loss of a single transition is about 0.5 dB. The compact structure and wideband performance give it potential in high-density millimeter-wave and terahertz packaging. [ABSTRACT FROM AUTHOR]