This work presents a filtenna concept based on cascaded singlet filters, which inherits independent controllability of attenuation poles from the filter design and has high stopband performance. Two fourth-order filters with a center frequency of 270 GHz, a 14 GHz bandwidth, and in-band return losses of 15 dB and 18 dB, respectively, are manufactured and measured to verify the proposed concept. The filtennas with a single-slot and a double-slot configuration are fabricated by the silicon deep reactive ion etching technology and have the size of 3.65x2.6 mm2. Detailed explanations of the synthesis procedure, which was validated through EM simulation, and measurement results are provided. The measured single-slot and double-slot filtennas exhibit broadside radiation gains of approximately 4.5 dBi and 6.5 dBi at 270 GHz, respectively. Moreover, the challenges and details of silicon micromachining in fabricating the two filtering antennas are discussed.

This communication introduces a graded index (GRIN) Fresnel zone planar lens (FZPL) antenna operating with high gain in the 500–750-GHz frequency range. The main innovation involves achieving a gain of 35.9 dBi by incorporating a GRIN dielectric perforated disk. This perforated disk acts as a distributed spatial delay for beam focusing, ensuring gain improvement and circular polarization simultaneously without needing an extra polarizer. The antenna exhibits high efficiency, with an average radiation efficiency of −1.05 dB, achieved through the optimization of a modified FZPL for silicon-on-insulator (SOI) micromachining technology. The antenna maintains a return loss below −15 dB across the entire 500–750-GHz band, achieving a 40% fractional bandwidth, with circular polarization maintained and an axial ratio consistently below 2.8 dB. The fabricated chip, sized 12.18×12.18 mm with a thickness of 526 μ m, enhances practicality. The feeding arrangement involves a standard open waveguide, and direct mounting into a standard WM-380 waveguide flange is facilitated. This communication discusses the prototype’s design, fabrication, and measurement, emphasizing the excellent agreement between the antenna’s performance and simulated data.

This paper investigates sub-THz computational imaging using compact, wideband, cavity-backed frequency-diverse antennas fabricated through silicon micromachining techniques. This paper presents a forward model based on pseudo-random frequency-diverse patterns using a Mills-Cross transmitter and receiver pair, which provides high-resolution imaging capabilities in the 220-330 GHz frequency range. The model is coupled with advanced compressed sensing algorithms, specifically Compressive Sampling Matching Pursuit (CoSaMP) and Fast Iterative Shrinkage-Thresholding Algorithm (FISTA), to enhance imaging performance under limited data acquisition. Through emulated simulation and experimental data, it is demonstrated that the system's ability to achieve range resolutions down to 1.4 mm and angular resolutions of 0.35°, even in the presence of noise, and analyze the trade-off between computational complexity and imaging accuracy. Sparsity investigations in spatial antenna population and frequency samples are comprehensively explored in this paper. The results show that using only 6.7% of the data, the CoSaMP algorithm can reconstruct a discernable image of the “KTH” logo. Results show that CoSaMP provides lower reconstruction error for sparse target distributions, while FISTA achieves superior noise resilience. The study highlights the practical implications of using frequency-diverse antennas in security screening and industrial inspection, where high-resolution imaging at sub-THz frequencies is demanded.

This paper presents the first demonstration of a high-gain planar THz lens antenna with beam-steering capability by frequency-orthogonal spatial spreading, operating in the 610–685 GHz range. The antenna is based on integrating a Fresnel zone planar lens with a graded-index silicon interposer. The concept enables passive beamforming of four simultaneous beams from a single feeding port, covering a field of view from -30° to -14° for 20 GHz bandwidth with a 4° separation of the beam direction. The beams can be swept continuously over that field of view by mapping the signal to different frequencies. Furthermore, when using four feeds, 16 simultaneous beams can be created, of which two frequency-orthogonal beams are separated by 40 GHz in frequency can be mapped into the same spatial direction. Thus, it is demonstrated that high-gain multibeam beam steering can be achieved without the hardware complexity of conventional phased-array antenna systems requiring a large number of RF chains. An antenna prototype is implemented using silicon micromachining, resulting in a compact 15.8 mm × 15.8 mm device with a thickness of 526μm, which is directly mounted on a standard WM-380 waveguide feed. Measurement results include a realized gain of 32.1 dBi, only a 0.8 dB beam steering loss across the field of view, an effective side-lobe suppression better than -22 dB, and a high radiation efficiency of -1.25 dB. The measurements are in excellent agreement with simulations, and the worst-case deviation of the measured beam direction from the simulated one is only 0.1° out of 16 beams.

This paper presents, for the first time, a novel highgain beam-steering lens antenna operating in the 610 to 645 GHz range. The antenna, fabricated using silicon micromachining, is based on incorporating a Fresnel lens layer in combination with a frequency-dependent graded-index interposer that acts as a passive beamformer. Frequency-dependent narrow beams are generated using an open waveguide feed. The prototype implemented in this paper features the generation of 8 frequencydependent narrow beams with just two open waveguide feeds. These beams can be steered from -30° to 2° in the azimuth. The prototype achieves a measured realized gain of 32.1 dBi with low beam-steering losses of just 0.8 dB. The antenna also exhibits a high radiation efficiency of -1.25 dB. The lens antenna is very compact, measuring only 15.8 mm × 15.8 mm × 0.526 mm. This beam-steering antenna offers a promising solution for future high-gain, multi-beam THz communication systems.

This thesis investigates advanced silicon micromachined passive component design solutions for high-performance millimetre and sub-millimetre-wave systems, representing the state-of-the-art in modern microwave and RF systems. The proposed designs are fabricated through deep reactive ion etching (DRIE). Silicon micromachining using DRIE offers the ability to fabricate small feature sizes, making it ideal for millimetre and submillimeter-wave systems applications, with low surface roughness and manufacturing tolerances in a scalable process. The proposed design solutions utilize waveguide-based technologies with the goal of advancing future generations of satellite communications, radar, remote sensing, and biomedical instrumentation. 

The core of this work is to propose design solutions to overcome manufacturing limitations, reduce transmission losses, introduce new design methods to enhance component performance, and simplify overall design complexity. 

The first part of the thesis introduces new platforms for transferring electromagnetic waves within silicon micromachined chips. Two structures are presented: a silicon-micromachined E-plane waveguide bend for flange-to-chip connection and a broadband on-chip rectangular waveguide 90º twist both for 220-325 GHz. The E-plane bend is crucial for transferring waves from outside the chip to the inside and eliminating reliance on external fixtures. The on-chip silicon micromachined twist enables interconnection of H-plane and E-plane waveguide subsystems, that increases fabrication flexibility. 

The second part discusses several novel filter design solutions operating at different frequency ranges from 90 to 300 GHz, each exhibiting state-of-the-art performance. An ultra-narrowband 4thorder filter with a wide spurious-free rejection band is developed for183 GHz. This filter utilizes high-Q-factor TM330 mode resonators and exhibits a measured Q-factor of 1000, surpassing any previously reported values in this frequency range. Additionally, a new negative coupling structure suitable for rectangular waveguide filters is proposed, offering compatibility with various fabrication methods, such as CNC milling and silicon micromachining. Using this negative coupling, a 4th-order quasi-elliptic bandpass filter with a centre frequency of 270 GHz and a fractional bandwidth of 2.2%is developed. Furthermore, a frequency variant coupling structure designed for rectangular cavities is proposed, enabling in-line filters with N+1 transmission zeroes, which can be easily manufactured and integrated with other subsystems. Using the proposed coupling structure, two filters are developed at 270 GHz: one 4th-order with 3transmission zeroes (TZs) and one 2nd-order with 3 TZs. Moreover, an integrated eighth-degree lowpass waveguide filter having a cut-off frequency of 280 GHz is presented. The lowpass filter is also fabricated using DRIE, with the aid of the twist proposed in section one. Furthermore, a compact band-pass filter with triplet response using one triangular singlet and two iris resonators is developed. Finally, a filtenna is introduced, combining a 4th-order filter with two slot antennas. The utilized filter employs 4 rectangular singlets introducing 4 transmission zeroes. The measured gain of the structure is 7 dBi, considering the use of on-chip E-plane bend transition to enable a direct connection to the flange.

Denna avhandling undersöker avancerade designlösningar för passiva komponenter tillverkade av mikromaskinerat kisel för högpresterande millimeter och sub-millimeter vågsystem, vilket representerar den senaste teknologin inom moderna mikrovågs och RF system. De föreslagna konstruktionerna tillverkas genom djup reaktiv jonetsning (DRIE). Kisermikromaskinering med DRIE erbjuder möjligheten att tillverka små detaljstorlekar, vilket gör den idealisk för tillämpningar inom millimeter och sub-millimeter vågsystem, med låg ytjämnhet och tillverkningstoleranser i en skalbar process. De föreslagna designlösningarna använder vågledarbaserade teknologier med målet att främja framtida generationer av satellitkommunikation, radar, fjärranalys och biomedicinsk instrumentering.

Kärnan i detta arbete är att föreslå designlösningar för att övervinna tillverkningsbegränsningar, minska transmissionsförluster, introducera nya designmetoder för att förbättra komponentprestanda och förenkla den övergripande designkomplexiteten.

Den första delen av avhandlingen introducerar nya plattformar för att överföra elektromagnetiska vågor inom kisermikromaskinerade chip. Två strukturer presenteras: en kisermikromaskinerad Eplan vågledarböjning för fläns-till-chip-anslutning och en bredbandig på-chip rektangulär vågledare 90º vridning, båda för 220-325 GHz. E-planböjningen är avgörande för att överföra vågor från utsidan av chipet till insidan och eliminera beroendet av externa fästanordningar. Den på-chip kisermikromaskinerade vridningen möjliggör sammankoppling av H-plan och E-plan vågledarsystem, vilket ökar tillverkningsflexibiliteten. 

Den andra delen diskuterar flera nya filterdesignlösningar som arbetar vid olika frekvensområden från 90 till 300 GHz, var och en med toppmoderna prestanda. Ett ultrasmalt 4:e ordningens filter med ett brett störningsfritt avvisningsband utvecklas för 183 GHz. Detta filter använder hög-Q-faktor TM330-lägesresonatorer och uppvisar en uppmätt Q-faktor på 1000, vilket överträffar alla tidigare rapporterade värden inom detta frekvensområde. Dessutom föreslås en ny negativ kopplingsstruktur lämplig för rektangulära vågledarfilter, som erbjuder kompatibilitet med olika tillverkningsmetoder, såsom CNC-fräsning och kisermikromaskinering. Med denna negative koppling utvecklas ett 4:e ordningens kvasi-elliptiskt bandpassfilter med en mittfrekvens på 270 GHz och en fraktionell bandbredd på 2,2%. Vidare förklaras en dispersiv kopplingsstruktur designad för rektangulära kaviteter, som möjliggör in-line filter med N+1 överföringsnollor, vilka enkelt kan tillverkas och integreras med andra delsystem. Med den föreslagna kopplingsstrukturen utvecklas två filter vid 270 GHz: ett 4:e ordningens med 3 överföringsnollor och ett 2:a ordningens med 3 TZ. Dessutom presenteras ett integrerat åttonde gradens lågpassvågledarfilter med en avskärningsfrekvens på 280 GHz. Lågpassfiltret tillverkas också med DRIE, med hjälp av den föreslagna vridningen i avsnitt ett. Slutligen introduceras en filtreringsantenn, som kombinerar ett 4:e ordningens filter med två slitsantenner. Det använda filtret utnyttjar 4 rektangulära singletter som introducerar 4 överföringsnollor. Den uppmätta förstärkningen av strukturen är 7 dBi, med tanke på användningen av på-chip E-plan böjövergång för att möjliggöra en direkt anslutning till flänsen.

This article presents a novel design of a full-band E -plane waveguide bend for direct flange-to-chip connection. The proposed E -plane bend concept is validated with a reduced-height bend prototype designed for standard WR-3.4 waveguide flange-to-chip connection, fabricated by silicon micromachining, and characterized by de-embedding the S -parameters with a custom-made offset-short calibration kit. The measured insertion and return losses are 0.08–0.3 dB and better than 14.7 dB, respectively, for the whole waveguide band of 220–320 GHz, and better than 0.15 and 20 dB, respectively, for more than 80% of the waveguide band. The measured results are in excellent agreement with the simulation data. Besides, a two-port waveguide structure with WR-3.4 interfaces is fabricated and measured to confirm the functionality of the designed E -plane bend. Furthermore, sensitivity analysis shows the robustness of the proposed geometry against fabrication tolerances.

This paper introduces a silicon-micromachined lens antenna, fabricated for operation in the 500-750 GHz range, featuring an optimized Graded Index Fresnel Zone Planner Lens (FZPL) design. The antenna efficiently radiates a circularly polarized wavefront without the need for additional phase compensation components. Through fabrication, the antenna achieves a high gain of 36 dBi and maintains a -15 dB return loss across the entire waveguide band. Significantly, this all-dielectric lens antenna exhibits minimal loss, ensuring elevated efficiency in Terahertz (THz) communication applications. With its low profile and compact design, this antenna emerges as a promising solution for upcoming wideband THz communication applications. This work not only emphasizes the innovative design but also underscores the practical realization of high-performance antennas with a compact footprint, leveraging silicon micromachining in the THz frequency bands.

This paper introduces a silicon-micromachined lens antenna, fabricated for operation in the 500-750 GHz range, featuring an optimized Graded Index Fresnel Zone Planner Lens (FZPL) design. The antenna efficiently radiates a circularly polarized wavefront without the need for additional phase compensation components. Through fabrication, the antenna achieves a high gain of 36 dBi and maintains a -15 dB return loss across the entire waveguide band. Significantly, this all-dielectric lens antenna exhibits minimal loss, ensuring elevated efficiency in Terahertz (THz) communication applications. With its low profile and compact design, this antenna emerges as a promising solution for upcoming wideband THz communication applications. This work not only emphasizes the innovative design but also underscores the practical realization of high-performance antennas with a compact footprint, leveraging silicon micromachining in the THz frequency bands.

This paper introduces an innovative siliconmicromachined antenna operating in the 500-750 GHz range, based on an optimized elliptical Fresnel Zone Plate Lens (FZPL) design. The antenna radiates a circularly polarized wavefront without additional phase compensation components. With a gain of 25.7 dBi and a 15 dB return loss over the whole waveguide band, this low-profile, compact antenna presents a promising solution for upcoming wideband THz communication applications. This work highlights the potential of silicon micromachining in achieving high-performance antennas with a compact footprint in the THz bands.