Takuro Tajima

300-GHz Step-Profiled Corrugated Horn Antennas Integrated in LTCC

This paper presents 300-GHz step-profiled corrugated horn antennas, aiming at their integration in low-temperature co-fired ceramic (LTCC) packages. Using substrate integrated waveguide technology, the cavity inside the multi-layer LTCC substrate and a surrounding via fence are used to form a feeding hollow waveguide and horn structure. Owing to the vertical configuration, we were able to design the corrugations and stepped profile of horn antennas to approximate smooth metallic surface. To verify the design experimentally, the LTCC waveguides and horn antennas were fabricated with an LTCC multi-layer process. The LTCC waveguide exhibits insertion loss of 0.6 dB/mm, and the LTCC horn antenna exhibits 18-dBi peak gain and 100-GHz bandwidth with more than 10-dB return loss. The size of the horn antenna is only 5×5×2.8 mm3, which makes it easy to integrate it in LTCC transceiver modules.

Compact THz LTCC Receiver Module for 300 GHz Wireless Communications

A compact, low-cost, fully-integrated package solution has been developed for 300 GHz short-range communication systems. Using low-temperature co-fired ceramic (LTCC) technology, an integrated reflector for the on-chip antenna and high-data-rate signal interconnections including a flip-chip and via transition are embedded in a package. A reduced-size silicon lens antenna is placed in a package cavity together with a flip-chip bonded receiver IC with an on-chip antenna. The overall size of the front-end receiver is only 10 × 10 × 4 mm3, including the 6 mm diameter silicon lens. This compact terahertz receiver, mounted on an evaluation board, demonstrated wireless links with data rates up to 27Gb/s.

Demonstration of 20-Gbps wireless data transmission at 300 GHz for KIOSK instant data downloading applications with InP MMICs

We present 20-Gbps wireless ASK data transmission at 300 GHz with an all-electronic transmitter and receiver for KIOSK instant data downloading applications. The transmitter and receiver MMICs are based on 70-nm indium-phosphide-based high electron mobility transistor technologies of which the cut-off frequency (fmax) is approximately 700 GHz. For an experiment, the transmitter and receiver were packaged in a split-block waveguide and dedicated metallic housing, respectively. With 30-dBi and 25-dBi horn antennas for the transmitter and receiver, error free data transmission (bit error rate <; 1 × 10-9) was achieved up to 80-cm link distance.

Characterization of the hydrogen-bond network of water around sucrose and trehalose: Microwave and terahertz spectroscopic study

Modification of the water hydrogen bond network imposed by disaccharides is known to serve as a bioprotective agent in living organisms, though its comprehensive understanding is still yet to be reached. In this study, aiming to characterize the dynamical slowing down and destructuring effect of disaccharides, we performed broadband dielectric spectroscopy, ranging from 0.5 GHz to 12 THz, of sucrose and trehalose aqueous solutions. The destructuring effect was examined in two ways (the hydrogen bond fragmentation and disordering) and our result showed that both sucrose and trehalose exhibit an obvious destructuring effect with a similar strength, by fragmenting hydrogen bonds and distorting the tetrahedral-like structure of water. This observation strongly supports a chaotropic (structure-breaking) aspect of disaccharides on the water structure. At the same time, hydration water was found to exhibit slower dynamics and a greater reorientational cooperativity than bulk water because of the strengthened hydrogen bonds. These results lead to the conclusion that strong disaccharide-water hydrogen bonds structurally incompatible with native water-water bonds lead to the rigid but destructured hydrogen bond network around disaccharides. Another important finding in this study is that the greater dynamical slowing down of trehalose was found compared with that of sucrose, at variance with the destructuring effect where no solute dependent difference was observed. This discovery suggests that the exceptionally greater bioprotective impact especially of trehalose among disaccharides is mainly associated with the dynamical slowing down (rather than the destructuring effect).

Selectivity-enhanced glucose measurement in multicomponent aqueous solution by broadband dielectric spectroscopy

We demonstrate the detection of physiological-range glucose in a multicomponent aqueous solution through multivariate analysis of broadband dielectric spectra from 500 MHz to 50 GHz. To enhance the selectivity to glucose, we applied spectral preprocessing on dielectric spectra to extract the feature values of glucose and bovine serum albumin (BSA). Using the regression models derived from different concentrations of glucose and BSA, the analysis was carried out on the solutions with the physiological range of both components. The prediction error of glucose concentration was estimated at less than 73 mg/dL even in various concentrations of BSA. This technique is easily implemented with a microwave blood glucose sensor or in other biomedical applications that essentially require multicomponent analysis.

Design and Analysis of LTCC-Integrated Planar Microstrip-to-Waveguide Transition at 300 GHz

A 300-GHz planar microstrip-to-waveguide transition in low-temperature co-fired ceramic (LTCC) is numerically and experimentally analyzed. A via fence and air holes are used to form a three-dimensional transition structure and a vertical hollow waveguide inside the multilayer LTCC substrate. The transition consists of a coplanar-waveguide-fed slot radiator backed by a short-wall of the waveguide and an open-circuited microstrip resonator. On the basis of the dual operation mechanism, the design guideline for the complex 3D structure is described using full wave analysis. The overall design is experimentally verified by a back-to-back transition which exhibits insertion loss of 4 dB at 300 GHz and 36-GHz bandwidth with better than 10-dB return loss. To evaluate the loss of a single transition, we carried out a loss component analysis by evaluating different lengths of microstrip line and hollow waveguide. The estimated loss for a single transition is 1 dB at 300 GHz. The planar transition without a metal back-short significantly reduces the size of terahertz packages and eliminates the need for additional components for hermetic sealing. The compact transition is easy to integrate in a low-cost LTCC package with an MMIC chip.

300-GHz microstrip-to-waveguide transition integrated in LTCC

A 300-GHz probe-type microstrip-to-waveguide transition in low-temperature co-fired ceramic (LTCC) is presented. A via fence and air holes are used to form a three-dimensional impedance-matching structure and a vertical hollow waveguide inside the multi-layer LTCC substrate. By incorporating the air-hole matching structure beside the microstrip probe, the bandwidth is enhanced. A prototype of the LTCC probe-type transition exhibits minimum insertion loss of 1.2 dB and 36-GHz bandwidth with less than 10-dB return loss. The compact transition makes it easy to integrate it in a low-cost LTCC package with an MMIC chip.

Multi-modality analysis of glucose aqueous solution using photoacoustic and dielectric spectroscopy for non-invasive glucose monitoring

Quantitative analysis of glucose using conventional optical spectroscopy suffers from a lack of repeatability due to high optical scattering in skin tissue. Here we present a multi-modality analysis of glucose aqueous solution using photoacoustic spectroscopy (PAS) and broadband dielectric spectroscopy (BDS). These techniques involve the direct detection of the acoustic and electromagnetic waves propagating through or reflecting from tissue without their being scattered. They therefore have potential for better tolerance to the variation of scattering. For PAS, to differentiate signals induced by water absorption, we select another laser wavelength (1.38 μm) that exhibits the same absorbance for water at 1.61 μm. Furthermore, one of the two photoacoustic signals is used to normalize the variations of acoustic properties in differential signal. Measured results for glucose solutions (0–2 g/dL) showed that the differential signal has a sensitivity of 1.61%/g·dL−1 and a detection limit of 120 mg/dL. We also tested glucose detection with BDS (500 MHz to 50 GHz) by detecting glucose hydration bonding at around 10-20 GHz. Using a partial least square analysis and first derivation on broadband spectra, we obtained an RMS error 19 mg/dL and a detection limit of 59 mg/dL. Using both the low-scattering ultrasonic and microwave detection techniques, we successfully captured the glucose footprint in the physiological range.

20-Gbit/s ASK wireless system in 300-GHz-band and front-ends with InP MMICs

We present a 20-Gbit/s ASK wireless system in the 300-GHz band for kiosk data downloading. The front-ends (transmitter and receiver) are manufactured by using InP-based monolithic microwave integrated circuits with high electron mobility transistors. We successfully demonstrate 20-Gbit/s data transmission using these front-ends at link distances from 50 cm to 1 m. The measured bit error rate is less than 10-6 up to the distance of 1 m.

Double-beam CW THz system with photonic phase modulator for sub-THz glucose hydration sensing

We present a double-beam dielectric spectroscopic system using an integrated photonic phase modulator for glucose hydration sensing from 0.25 to 1.0 THz. Compact phase modulators with a photonic circuit and a double-beam scheme using a broadband beam splitter enable us to improve signal stability in sub-THz generation and detection. Using the system, we carried out fast vector measurement on glucose solutions with effective signal stabilization. By incorporating a simple calibration procedure for the extraction of dielectric properties, the Fabry-Perot effect in liquid cell window was mitigated. The system demonstrated accurate detection of glucose dielectric spectra for hydration analysis of glucose-water interaction in sub-THz region.