Nazy Ranjkesh

Photonic-Crystal-Based Polarization Converter for Terahertz Integrated Circuit

In this paper, the fabrication and characterization of newly developed photonic crystal (PC) polarization-controlling devices on a silicon-on-insulator wafer for integrated terahertz applications are presented. The polarization converter is composed of periodic asymmetric loaded PC slab waveguide. Square- and circular-hole PC slab waveguides were studied using a 3-D finite-difference time-domain method. For a square-hole PC-based polarization rotator, polarization rotation efficiency higher than 90% was achieved within the normalized frequency band of a/ λ = 0.258-0.267 . In circular-hole PC polarization converter, the polarization conversion efficiency dropped to 70% for the aforementioned frequency band. Low polarization conversion efficiency of the circular-hole PC-based device is attributed to scattering loss at the top loaded layers. Thus, the square-hole PC structure is a better candidate for integrated terahertz polarization-controlling devices. Planar terahertz integrated circuit technology was developed to implement the proposed device. Characterization setup was designed using rigorous numerical methods to use the newly introduced Agilent Millimeter-wave PNA-X network analyzer (up to 500 GHz) as a source. Scattering parameter characterizations provide a good measure of polarization extinction ratio. For the devices designed for the central frequency of f = 200 GHz, it was observed that, within the frequency band of 198-208 GHz (α/λ = 0.26-0.272), the ratio of S21 to S11 was higher than 15 dB. The bandwidth is in good agreement with our preliminary design presented before.

Silicon-on-Glass Dielectric Waveguide—Part I: For Millimeter-Wave Integrated Circuits

A low-cost Silicon-on-Glass (SOG) integrated circuit technology is proposed for millimeter-wave (mmW) applications, for the first time. In the proposed technology, all mmW passive components are made of high-resistivity Silicon (Si) on a glass substrate. The proposed technique leads to a high-precision and low-cost fabrication process, which eliminates the need for costly assembly of the complex structures. This is achieved by photolithography and dry etching of the entire integrated passive circuit through the Si layer of the SOG wafer. Silicon-on-Glass dielectric waveguide, as the basic component of the SOG integrated circuit, is theoretically and experimentally investigated. A test setup is designed to measure propagation characteristics of the proposed SOG waveguide. Measured dispersion diagrams of the SOG dielectric waveguide show average attenuation constants of 0.63 dB/cm, 0.28 dB/cm, and 0.53 dB/cm over 55-65 GHz, 90-110 GHz, and 140-170 GHz, respectively.

Silicon-on-Glass Dielectric Waveguide—Part II: For THz Applications

A low-loss sub-millimeter-wave/THz integrated dielectric waveguide is presented. The proposed waveguide consists of a highly resistive Silicon (Si) guiding channel bonded to a glass substrate. To reduce the waveguide insertion loss due to the glass substrate, part of the substrate below the Si guiding channel is etched. A periodic configuration of supporting beams is used to hold the Si guiding channel over the glass substrate. A low-cost and high-precision fabrication process, which is fully compatible with current Si-based fabrication technologies, is developed for the proposed waveguide. Numerical simulations and experiments are conducted to investigate the performance of the proposed waveguide. Measured attenuation constant of the proposed waveguide is 0.0346 dB/ λo (average value) over the 440-500 GHz band.

Millimeter-Wave Silicon-on-Glass Integrated Tapered Antenna

This letter presents a millimeter-wave (mmW) high-efficiency tapered dielectric antenna, which is designed and fabricated on a new integrated technology platform called silicon-on-glass (SOG). The antenna is fabricated using photolithography and dry etching of the Si layer of the SOG wafer. The proposed antenna advantages include high efficiency, low-cost fabrication with high precision, and small size. Experimental results are presented to validate the new design concept, which is optimized for low sidelobe, high gain, and short length.

Millimeter-Wave Suspended Silicon-on-Glass Tapered Antenna With Dual-Mode Operation

A highly efficient millimeter-wave (mmW)/Terahertz (THz) dielectric antenna is proposed. The proposed suspended tapered antenna [made of high resistivity silicon (Si)] is fabricated in a new mmW/THz integrated technology platform called silicon-on-glass (SOG). The fabrication process makes the tapered antenna with deep reactive ion etching of the Si layer of the SOG platform, wherein a part of the glass substrate below the antenna tapered section is etched. The glass substrate below the antenna is etched in hydrofluoric acid (HF 49%) before bonding to the Si wafer. The antenna is designed to radiate both Ex-and Ey-polarizations over the frequency band of 110-130 GHz and features additional advantages including highly linear polarization, high-directivity, integrability, and low-cost fabrication. Numerical and experimental results are presented to validate the high-performance proposed antenna. Experiments show gains of 17.5 dBi at 115 GHz and 18.3 dBi at 128 GHz for Ex11 -and Ey11 , -modes excitations, respectively. These two polarizations show measured efficiencies of 94% and 99%, respectively.

Low Loss, Wideband, and Compact CPW-Based Phase Shifter for Millimeter-Wave Applications

This paper proposes a compact, low-loss, and low cost phase shifter for millimeter-wave phased array systems. The basic idea is to modify the propagation mode of a coplanar waveguide (CPW) by placing a high dielectric constant (40 <; εr <; 170) slab on top of it. The phase shift is varied by changing the air gap between the CPW line and the dielectric slab. A piezoelectric transducer has been used to control this air gap precisely. For fast but accurate modeling of the proposed phase shifter, two methods one based on spectral domain analysis and the other based on the conformal mapping have been developed and verified with full wave simulations and measurements. A prototype structure with the operational frequency range from 20 to 40 GHz is presented. The maximum phase shift obtained for the electrically controlled version at 40 GHz is 103 ° with loss variation of 0.2 dB. The total length is 2 mm.

Low insertion loss variable phase shifter for emerging millimeter-wave communication systems

This paper proposes a compact, low-loss, and low cost phase shifter for mmWave applications. The basic idea is perturbing the propagation constant of a CPW line by its loading with a high dielectric constant BLT ceramic. The phase shift is sensitive to the air gap between the CPW and the BLT sample. For a sample with a length of 3mm, a phase shift of 170° at 30GHz is obtained while the average insertion loss is less than 1.45dB with a variation of 1.1dB for the full range of phase shifts.

A low-loss CPW to dielectric waveguide transition for millimeter-wave hybrid integration

A transition from a coplanar waveguide (CPW) to a dielectric waveguide is investigated for the integration of active devices into dielectric waveguide structures. The transition consists of three parts: CPW to a slot line, the slot line to a dielectric waveguide, and a linear tapering part for matching the first and the last parts, respectively. The maximum of insertion loss is -1.7dB, and the return loss is less than -15dB over 7% bandwidth at 60GHz.

Low-cost sub-millimeter-wave/THz integrated system technologies

Three approaches will be presented for low-cost sub-millimeter/THz integrated circuits and systems. Multi-layer planar line monolithic integration, dielectric waveguide hybrid technology, and SOI-based photonic-crystal technique will be described and recent progresses and typical developed integrated devices will be discussed.

Silicon-On-Glass dual-tapered antenna

In this paper, a Silicon-On-Glass (SOG) tapered dielectric antenna is presented. The antenna is made from high-resistivity Si and supported on a glass substrate. To increase the antenna efficiency, the Pyrex substrate below the Si tapered sections is etched. To decrease the antenna size and the Side Lobe Level (SLL), the single tapered section is replaced by two shorter tapered sections coupled to each other. The antenna shows a directivity of 15.1 dB and a SLL of -27 dB at 126 GHz.