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Microwave application technologies such as microwave heating, microwave assisted chemistry, etc. are of the innovative green technologies. In this paper, a chip-size microwave applicator with plural microchannels is designed at 24 GHz band. It consists of the post-wall waveguide and two or more micro channels arranged among the metallic posts. This applicator realizes microwave heating at different temperatures for the microchannels embedded in the separate places. The temperature-time profiles of the applicator are examined numerically. An experimental verification is performed with microwave power sources of about 0.7 W.

A new type of nonreciprocal composite right/left-handed transmission line is proposed, and its transmission characteristics are studied numerically and experimentally. Basic structure is similar to conventional left-handed ferrite waveguides operating in frequency range where the effective permeability of ferrite ( $\mu_{\mathrm{eff}}$ ) is negative, but it operates in lower range where $\mu_{\mathrm{eff}}$ is positive. Nonreciprocal dispersion diagram is derived by numerically. In the forward direction, always it has a so-called $\Gamma$ point of the CRLH-TL at which waves of infinite wavelength propagate at finite group velocity. $S$ parameters with nonreciprocal phase characteristics which correspond to the nonreciprocal dispersion characteristics are derived by numerical simulation. Measured $S$ parameters agree well calculated results. The applications such as a nonreciprocal phase shifter, a tunable $\Gamma \mathrm{point}$ , and a nonreciprocal leaky wave antenna may be expected.

Microwave application technologies such as microwave heating., microwave assisted chemistry., etc. are of the innovative green technologies. In this paper., a 5.8 GHz microwave applicator of medium size is proposed based on the post-wall waveguide structure. It is allowed to irradiate microwaves to solvent of several milliliters and to flow the heated solvent out continuously. The validity of the proposed applicator is examined numerically and experimentally with microwave power sources of about 5 W.

A new type of nonreciprocal CRLH-TL composed of gyrator and series capacitor is proposed, and a nonreciprocal dispersion diagram., showing that seamless transition from the LH to RH mode through not only an infinite-wavelength wave for forward direction but also a wave with wavelength of two unit cells for reverse direction with energy transmission., are confirmed theoretically and experimentally.

Background The measurement of transcutaneous bilirubin (TcB) is very important to screen for hyperbilirubinemia in newborns. Until now, however, there has been no hour-specific, percentile-based TcB nomogram during the early neonatal period in Japanese neonates. The aim of this study was to develop a TcB nomogram within 72 h of birth in Japanese neonates. Methods A total of 3152 TcB measurements for 181 healthy Japanese neonates (gestational age ≥36 weeks, birthweight ≥2300 g) were obtained within 72 h of birth. All measurements were performed with a Konica Minolta jaundice meter, the JM-103. A nomogram curve was plotted to show the trend of TcB level over time. Results The nomogram curves rose almost linearly for all percentiles until 72 h after birth. Conclusion An hour-specific, percentile-based TcB nomogram during the first 72 h after birth in Japanese neonates was successfully developed. Because Japanese neonates have higher and later peak bilirubin, an original hour-specific 97.5th percentile-based TcB nomogram may be needed to identify early-onset jaundice and manage neonatal hyperbilirubinemia.

The purpose of this study was to examine developmental changes in visuocognitive function, particularly face recognition, in early infancy. In this study, we measured eye movement in healthy infants with a preference gaze problem, particularly eye movement between two face stimulations. We used the eye tracker system (Tobii1750, Tobii Technologies, Sweden) to measure eye movement in infants. Subjects were 17 3-month-old infants and 16 4-month-old infants. The subjects looked two types of face stimulation (upright face/scrambled face) at the same time and we measured their visual behavior (preference/looking/eye movement). Our results showed that 4-month-old infants looked at an upright face longer than 3-month infants, and exploratory behavior while comparing two face stimulations significantly increased. In this study, 4-month-old infants showed a preference towards an upright face. The numbers of eye movements between two face stimuli significantly increased in 4-month-old infants. These results suggest that eye movements may be an important index in face cognitive function during early infancy.

Background: To evaluate the clinical effects of phototherapy for neonatal hyperbilirubinemia, it is necessary to measure the rate of cyclobilirubin production, which represents the main photochemical pathway of bilirubin metabolism. Since the Atom Phototherapy Analyzer can be used to calculate the theoretical relative light energy of irradiance as a means of assessing the cyclobilirubin production rate for each wavelength spectrum, the clinical effect of phototherapy can be evaluated regardless of the light source type. Using the Atom Phototherapy Analyzer, the correlation between the irradiance of various light sources with different peak wavelengths and the rate of cyclobilirubin production was investigated in vitro. We also investigated the utility of green LED in vitro. Methods: A bilirubin-albumin complex solution was prepared, poured into tubes, and irradiated using various light sources. All light sources used were bed-type phototherapy devices; that is, green and blue LED and green and blue fluorescence tubes. The concentrations of photoisomers were measured after irradiation and compared with the irradiance of the light sources. Results: The irradiance measured by the Atom Phototherapy Analyzer decreased in the following order: blue fluorescence tube > green LED > blue LED > green fluorescence tube. The cyclobilirubin production rates and irradiance values of the light sources were significantly positively correlated (R2= 0.93, P < 0.05). Conclusion: Our data indicate that the Atom Phototherapy Analyzer can be used to objectively evaluate the effects of phototherapy using various light sources. Further, the effects of green LED were similar to those of other light sources in vitro.

Left-handed characteristics of microstrip line on the longitudinally magnetized ferrite substrate are investigated with both theoretically and experimentally. Transmission characteristics of the line are estimated by using an equivalent circuit model, and the high frequency structure simulator (HFSS) based on the finite element method. Experiments are undertaken using polycrystalline yttrium iron garnet substrate having 30 times 15 mm in thickness of 1 mm. Expected left-handed response within negative permeability region is found and agrees well with theory. Phase shifter tuned by the magnetic field is proposed as an application of the left-handed ferrite line.

The aim of this study was to evaluate the hypothesis that cerebral hemoglobin (Hb) oxygenation is related to phosphorylation potential during primary and secondary cerebral energy failure in newborn infants who have experienced birth asphyxia. We subjected newborn piglets to severe transient cerebral hypoxic-ischemia followed by resuscitation and examined cerebral energy metabolism by 31P-magnetic resonance spectroscopy and evaluated changes in cerebral Hb oxygen saturation (ScO2) using full-spectrum near-infrared spectroscopy before, during, and up to 54 h after the hypoxic-ischemic insult. ScO2 was significantly decreased during the hypoxic-ischemic insult compared with baseline values. During secondary energy failure, piglets were separated based on the relationship between the ratio of phosphocreatine to inorganic phosphate and ScO2; those with a negative correlation were less injured than those with a positive correlation. These results indicate that changes in ScO2 as measured by near-infrared spectroscopy are related to phosphorylation potential during secondary energy failure in asphyxiated infants.

Using optical topography, changes in the cerebral oxygenation were compared in the parieto-temporal lobe of preterm and term infants of equal postconceptional age in response to verbal stimulation. Eight preterm infants of gestational age 23-34 weeks were studied at postconceptional term age (38-46 weeks). Ten term infants were studied at 2-11 days after birth. Twenty-four-channel near-infrared optical topography (NIOT) was used to measure changes in concentration of oxyhemoglobin ([oxyHb]), deoxyhemoglobin ([deoxyHb]) and total hemoglobin ([totalHb]) in the bilateral temporal cortices. Verbal stimulation was provided by a recording of a Japanese fairy tale. The latency in response to verbal stimulation was significantly shorter in the preterm infants than in the term infants. This time is thought to reflect brain development, particularly the development of the neuro-vascular coupling mechanisms in the cerebral cortex. The present results indicate that the number of days after birth is more closely related to development of auditory system and neuro-vascular coupling than is postconceptional age. Thus, this suggests that early extrauterine environment affects the cortical responses to verbal stimulation in preterm infants.

Background: The light-emitting diode is used as one of the new light sources for phototherapy. NeoBLUE (Atom Medical, Tokyo, Japan) incorporates blue light-emitting diodes for the treatment of neonatal hyperbilirubinemia. The authors compared the in vitro efficacy of neoBLUE with conventional phototherapy devices. Methods: The three light devices used included neoBLUE and two conventional phototherapy devices with six blue–white (BW) or six green (GR) fluorescent tubes. A bilirubin/human serum albumin solution (15 mg/dL) in 200 × 300 mm elliptical bag was irradiated with each three light device. The average light intensity of neoBLUE, BW and GR was 22.5, 10.2 and 2.6 μW/cm2 per nm, respectively, for the irradiated area. Bilirubin photoisomers and native bilirubin were measured by high-performance liquid chromatography. Results: In neoBLUE, BW and GR, the respective production rate of cyclobilirubin was 6.0, 3.7 and 3.9 × 10−2 mg/dL/min, and the respective (4Z, 15E)-bilirubin/(4Z, 15Z)-bilirubin ratio after irradiation was 0.44, 0.33 and 0.12; the (4Z, 15Z)-bilirubin reduction rate at 20 min after irradiation was 60, 68 and 82%, respectively. The reduction rate of (4Z, 15Z)-bilirubin correlated with the (4Z, 15E)-bilirubin/(4Z, 15Z)-bilirubin ratio. Conclusion: Phototherapy using the neoBLUE under high level may be clinically more effective than therapy using the conventional light source from the results of the production rate of cyclobilirubin.

Summary Background: Estimation of hemodynamics is important for critically ill infants. Pulse dye densitometry (PDD) using indocyanine green (ICG), which enables measurements of circulating blood volume at the bedside, has recently been developed for adults. Methods: We conducted a basic investigation to determine whether this method can be applied to infants and measured circulating blood volume in 25 infants whose gestational ages ranged from 24 to 40 weeks (median, 32 weeks). At first, to validate the accuracy of measurements, arterial ICG concentrations determined by blood sample measurements were compared using a spectrophotometer ([ICG blood]) and by noninvasive measurement using PDD ([ICG pdd]) in seven infants. Next, blood volumes in 25 infants were estimated by the PDD method. Results: There was a positive relationships between [ICG blood] and [ICG pdd] (r = 0.913, P

Background: The developmental changes of the umbilical cortisol levels in neonates at gestational age of 23–41 weeks were studied and the effect of antenatal steroid administration on the umbilical cortisol levels were examined. Methods: Cortisol levels in the umbilical vein (UV) and the umbilical artery (UA) were studied in 35 neonates at the gestational age (GA) of 23–41 weeks with or without antenatal administration of corticosteroids. Serum cortisol concentrations were measured by the high performance liquid chromatography method. Results: The correlation between cortisol levels in UV and birthweight (BW) was weak and negative in premature infants. UV cortisol levels in the neonates with antenatal corticosteroid were lower than those in the neonates without antenatal corticosteroid, but the relation was not significant. The developmental changes of UV cortisol levels were the same as those in Murphy's study (spontaneous-onset labor). The cortisol levels in UV and UA had a significantly positive correlation and both had almost equal concentrations. There were no correlations between cortisol levels in UV and placental weight, Apgar Score at 1 and 5 min. Conclusions: In the neonates whose birthweight was less than 2000 g without antenatal corticosteroid, there was a negative correlation between cortisol levels in UV and BW but there was no correlation between cortisol levels in UV and GA. That the neonates with antenatal corticosteroid would have a suppressed adrenocortical function after birth could not be proved.

Background: The clinical effect of phototherapy for neonatal hyperbilirubinemia is based on the production and elimination of cyclobilirubin. Generally, the clinical effect of light sources is estimated by the reduction in the total serum bilirubin level. One procedure with less invasiveness than blood collecting is urine collection. Whether the effectiveness of light sources used for phototherapy could be assessed using measurements of bilirubin photoisomers in urine was studied. Methods: This study was a retrospective analysis of 38 term infants with hyperbilirubinemia who underwent phototherapy. Bilirubin fractions in serum and urine before and 24 h after the phototherapy were measured by high-performance liquid chromatography. The light sources used for the phototherapy were blue-white light (n = 11), Biliblanket plus high output (n = 13) or green light (n = 14). The relationships between serum and urine bilirubin photoisomers after phototherapy and whether the levels of urine bilirubin photoisomer are affected by the light sources with different wavelength characteristic were analyzed. Results: There was no correlation between serum (ZE)-bilirubin and urine configurational isomers, but a weak positive correlation between serum (EZ)-cyclobilirubin and urine structural isomers after phototherapy. Although serum (ZE)-bilirubin levels depended on the wavelength characteristic of each light source during phototherapy, the urine configurational isomer levels did not depend on it. The increase in serum (EZ)-cyclobilirubin levels and the urine structural isomer levels were mostly in agreement. Conclusions: The urine bilirubin structural isomers may be used to estimate the serum (EZ)-cyclobilirubin levels and to evaluate the clinical effects of light sources.

During the developmental stage, the brain undergoes anatomic, functional, and metabolic changes necessary to support the complex adaptive behavior of a mature individual. Estimation of developmental changes occurring in different regions of the brain would provide a means of relating various behavioral phenomena to maturation‐specific brain structures, thereby providing useful information on structure‐function relationships in both normal and disease states. We used multichannel near‐infrared spectroscopy (MNIRS), a new noninvasive imaging technique for revealing the course of neural activity in selected brain regions, to monitor the activities of the visual cortex as mirrored by hemodynamic responses in infants subjected to photostimulation during natural sleep. In the infants, oxyhemoglobin and total hemoglobin decreased and deoxyhemoglobin increased in the visual cortex with photostimulation. This pattern of responses was different from the response pattern in adults reported previously. The different patterns of responses to photostimulation in the visual cortices of infants and adults might reflect developmental and behavioral differences. It may reflect a different functional organization of the visual cortex in infants or ongoing retinal development. Our results demonstrated that regional hemodynamic change could be detected in a small area around the visual cortex. MNIRS offers considerable potential for research and noninvasive clinical applications. Hum. Brain Mapping 22:124–134, 2004. © 2004 Wiley‐Liss, Inc.

Near-infrared spectroscopy (NIRS) has been used for measurement of changes in cerebral hemoglobin concentrations in neonates to study cerebral oxygenation and hemodynamics. In this study, measurements by time-resolved reflectance spectroscopy (TRS) were performed in a piglet model with various degrees of cerebral oxygenation to estimate the differential pathlength factor (DPF). A portable three-wavelength TRS system (TRS-10, Hamamatsu Photonics K.K.) with a probe attached to the head of a piglet was used. Eleven newborn piglets were anesthetized and respired by a ventilator to induce stepwise hypoxia loading. The DPF showed positive linear relationship with arterial hemoglobin (Hb) oxygen saturation and sagittal sinus venous Hb oxygen saturation at 761 and 795 nm. The DPF at 835 nm also showed very slight positive linear relationship with arterial hemoglobin oxygen saturation. The DPF values obtained in this study should contribute to a better understanding of noninvasive measurements by NIRS in neonates.

To investigate whether or not the mode of delivery produces differences in cerebral oxygenation, cerebral hemoglobin oxygen saturation was measured using full-spectrum near infrared spectroscopy in 26 healthy term newborn infants immediately after birth. Infants in group 1 ( n =20) were delivered vaginally, and those in group 2 ( n =6) by elective cesarean section. Arterial oxygen saturation in the right hand was also measured simultaneously using a pulse oximeter. Changes in arterial oxygen saturation showed no significant difference between the two groups. The mean±S.D. of cerebral hemoglobin oxygen saturation in group 1 increased rapidly after birth, from 29±17% at 2 min to 68±6% at 8.5 min, followed by an almost constant value (66±7% at 15 min). In comparison, cerebral hemoglobin oxygen saturation in group 2 also increased rapidly until 8.5 min, but after this time decreased significantly to 57±5% at 15 min after birth. This indicates that the mode of delivery has a marked influence on cerebral oxygenation immediately after birth.

The aim of this study was to quantify the relative concentrations of oxyhemoglobin and deoxyhemoglobin within the light path of the brain and to estimate cerebral hemoglobin (Hb) oxygen saturation using full-spectrum near-infrared spectroscopy (fsNIRS). For this purpose, we developed a novel exponential correction equation as well as a two-point spectroscopy method to estimate the relative concentrations of Hb and Hb oxygen saturation in biological tissues. The results of evaluation of measurements using an in vitro model indicated that our fsNIRS method enables accurate and non-invasive measurements of Hb content and saturation in a highly scattered medium such as the human brain. According to the results of analysis using a hypoxic piglet model, the mean cerebral Hb oxygen saturation (SbO(2)) of newborn piglets at an inspired oxygen gas concentration of 0.21 was estimated to be 63+/-4% (mean+/-S.D.). Umbilical arterial and left internal jugular venous Hb oxygen saturation were simultaneously estimated to be 96+/-2% and 52+/-11%, respectively. SbO(2) and arterial Hb oxygen saturation values had a linear relationship. The average oxygenation state of cerebral tissue is comparable with that of the cerebral vein. The results of this study showed that our method can be used to monitor Hb oxygen saturation in the neonatal brain at the bedside in an intensive care unit.

This is the first report on the use of near-infrared topography (NIRT) for functional imaging of the visual cortex of newborn infants during photic stimulation (PS) under the condition of natural sleep. Measurements were conducted in four healthy term neonates within 1 week after birth. NIRT was performed on the occipital region of the head using a device consisting of 16 optical fibers, 8 for transmission and 8 for detection, and 24-measuring points were determined. Baseline data were collected over a period of 10 s. PS was produced by flashing lights (laser-emitting diodes) at 8 Hz and lasting for 15 s, followed by a 45-s rest period. Data were collected every 0.1 s, averaged over 10 cycles, and smoothed. As control data, hemodynamic changes in all neonates without stimulation were measured by the same method. PS caused marked increases from the baseline values in oxyhemoglobin ([HbO2]) and total hemoglobin ([T-Hb]) and a decrease in deoxyhemoglobin ([Hb]) in the primary visual areas of all neonates. We conclude that our method is useful for imaging and evaluating the primary visual area function in response to PS even in newborn infants during natural sleep.

This is the report on the use of near-infrared topography (NIRT) with indocyanine green (lCG) to determine regional cerebral blood flow (rCBF) distribution in infants. We measured four infants without neural abnormalities and one infant with bilateral intraventricular and right cerebellar hemorrhage. A probe consisting of 16 optical fibers, 8 for transmission and 8 for detection, was set on the temporal regions of the head of the infant, and 24 measuring points were determined. Changes in regional cerebral ICG concentration were recorded using NIRT. Simultaneously, the arterial blood concentration of ICG was noninvasively measured by pulse dye densitometry using the general principles of pulse oximetry. rCBF was calculated from the modified Fick's equation. The rCBF of fronto-temporal, temporal and occipito-temporal regions ranged from 11.5 to 19.4, 9.8 to 16.9 and 9.7 to 16.6 ml/100 g/min, respectively. It was found that in the area of intracerebral involvement of the infant with hemorrhage, little or no cerebral blood flow was detected. We conclude that our method is useful for measuring rCBF distribution at the bedside in neonates with an illness in the acute phase.

We demonstrated spatiotemporal changes in hemoglobin concentrations in the sensorimotor cortex of a neonate during passive motor stimulation using multichannel near-infrared spectroscopy. This study was carried out on a healthy term neonate without neurological problems under the condition of sedative sleep. We employed a 24-channel near-infrared topography device with two wavelengths (780 and 830 nm), each with an interoptode distance of 2 cm, in this study. The probes were placed in the parietotemporal region over the sensorimotor cortex. An examiner flexed and extended the infant's leg and arm at the knee and elbow joints at a frequency of approximately 0.7 Hz. This passive motor stimulation consisted of 8–10 repetitions of the movement, each lasting for 15 s, followed by a 30-s rest period. Contralateral knee movement caused marked increases in oxyhemoglobin concentration ([HbO2]) and totalhemoglobin concentration ([T-Hb]) from the baseline values at almost all locations in the primary sensorimotor area and a decrease in local deoxyhemoglobin concentration ([Hb]). On the other hand, contralateral elbow movement caused marked increases in [HbO2] and [T-Hb] in more restricted regions than did knee movement. The results show that sensorimotor area function in response to passive motor stimulation can be imaged and evaluated even in newborn infants during sedative sleep.

Near-infrared topography with indocyanine green was used to measure regional cerebral blood flow (rCBF) in the temporal lobes of infants. The mean rCBF in infants without neural abnormality was 14.5 ± 3.1 ml/100 g/min, and the rCBFs in the fronto-temporal, temporal, and occipito-temporal regions were 15.1 ± 3.9, 15.4 ± 3.3, and 14.6 ± 3.3 ml/100 g/min, respectively. Moreover, in one asphyxiated infant with infarction and one infant with subdural and intracerebellar hemorrhage, it was demonstrated that the area of defective blood flow could be detected as well as it can by SPECT. This technique makes it possible to estimate rCBF distribution in infants at the bedside. Thus, in the future, evaluation of various neonatal illnesses should be feasible.

The measurement of transcutaneous bilirubin (TcB) is very important to screen for hyperbilirubinemia in newborns. Until now, however, there has been no hour-specific, percentile-based TcB nomogram during the early neonatal period in Japanese neonates. The aim of this study was to develop a TcB nomogram within 72 h of birth in Japanese neonates.A total of 3152 TcB measurements for 181 healthy Japanese neonates (gestational age ≥36 weeks, birthweight ≥2300 g) were obtained within 72 h of birth. All measurements were performed with a Konica Minolta jaundice meter, the JM-103. A nomogram curve was plotted to show the trend of TcB level over time.The nomogram curves rose almost linearly for all percentiles until 72 h after birth.An hour-specific, percentile-based TcB nomogram during the first 72 h after birth in Japanese neonates was successfully developed. Because Japanese neonates have higher and later peak bilirubin, an original hour-specific 97.5th percentile-based TcB nomogram may be needed to identify early-onset jaundice and manage neonatal hyperbilirubinemia.

This paper proposes a 0-dB forward coupler consisting of the half-mode groove waveguides for wireless power transmission. The half-mode groove waveguide is equivalent to the groove waveguide of LSM mode, where the electric wall is assumed on the symmetrical plane. Though this structure occupies only half of the groove waveguide, it has the same property as the groove waveguide. In this paper, the transverse resonance technique and the mode matching method are applied to derive the even- and odd-modes phase constants. Then, a 0-dB forward coupler including bend sections is designed at 24GHz and the S-parameters are calculated. In addition, a dielectric strip is inserted to increase the spacing between the two guides. The validity of the design results is confirmed using em-simulator (HFSS).

To evaluate the clinical effects of phototherapy for neonatal hyperbilirubinemia, it is necessary to measure the rate of cyclobilirubin production, which represents the main photochemical pathway of bilirubin metabolism. Since the Atom Phototherapy Analyzer can be used to calculate the theoretical relative light energy of irradiance as a means of assessing the cyclobilirubin production rate for each wavelength spectrum, the clinical effect of phototherapy can be evaluated regardless of the light source type. Using the Atom Phototherapy Analyzer, the correlation between the irradiance of various light sources with different peak wavelengths and the rate of cyclobilirubin production was investigated in vitro. We also investigated the utility of green LED in vitro.A bilirubin-albumin complex solution was prepared, poured into tubes, and irradiated using various light sources. All light sources used were bed-type phototherapy devices; that is, green and blue LED and green and blue fluorescence tubes. The concentrations of photoisomers were measured after irradiation and compared with the irradiance of the light sources.The irradiance measured by the Atom Phototherapy Analyzer decreased in the following order: blue fluorescence tubegreen LEDblue LEDgreen fluorescence tube. The cyclobilirubin production rates and irradiance values of the light sources were significantly positively correlated (R(2) = 0.93, P0.05).Our data indicate that the Atom Phototherapy Analyzer can be used to objectively evaluate the effects of phototherapy using various light sources. Further, the effects of green LED were similar to those of other light sources in vitro.

This paper describes a method to broaden the bandwidth of cruciform substrate-integrated waveguide couplers. The design and the analysis of the couplers are performed using the H-plane planar circuit approach, and the frequency characteristics of the couplers designed at 24 GHz are shown. As a result, fractional bandwidths of 30% for a 3dB coupler and 16% for a 1.7dB coupler can be realized. The design results are verified numerically and experimentally.

We have proposed a new type of the CRLH-TL consisting of two-layer planar substrates recently. It consists of a base waveguide of a substrate integrated waveguide (SIW), and series capacitances realized by slit apertures and metal patchs arranged on the upper conductor of the SIW. It is expected to become one of the basic CRLH-TL structures over 10 GHz or millimeter-wave. However radiation from the metal-patchs cannot neglect in this structure. Then we proposed a leaky-wave antenna using the SIW metal-patch type CRLH-TL. In this paper, beam scan characteristics as a function of driving frequency are confirmed theoretically and experimentally. A SIW metal-patch type CRLH-TL with transition frequency of 16 GHz is designed for a leaky-wave antenna and fabricated. Measured results agree well with theoretical and numerical results.

A compact H-plane waveguide cruciform coupler using metallic posts has recently been proposed. It consists of two rectangular waveguides crossing each other at right-angles, two metallic posts arranged on a diagonal line of the cross region for producing directional properties, and one metallic post inserted for matching at each waveguide port. Generally, it is known that any lossless reciprocal 4-port circuit with two-fold symmetry can constitute 90-degree directional coupler, if the four ports are completely matched. In this work, a design of the cruciform hybrid coupler using dielectric posts instead of metallic posts is attempted [3]. The analysis and the design are performed based on the H-plane planar circuit approach for short-circuited boundary segments with the use of the segmentation method. It is shown that good frequency characteristics with fractional bandwidths of about 10% can be realized for the X-band waveguides. The validity of the design results is confirmed by an EM-simulator (Ansoft HFSS) and an experiment.

A transducer type isolator is proposed using tangentially magnetized YIG single crystal. The single crystal is analyzed by the finite element method. Frequency response of scattering parameters and field distribution were calculated and optimized by using high frequency structure simulator. Experiments were undertaken using a single crystal of YIG slab, and measured results corresponded well to the numerical results. Isolation ratio of 48 dB with 6 dB insertion loss and 880 MHz bandwidth around 4.2 GHz was measured. Characteristics using composite right/left-handed transmission lines (CRLH-TL) transducers were also investigated and isolation ratio of 48 dB with 5.5 dB insertion loss and 2.0 GHz bandwidth (from 3.85 GHz to 5.85 GHz) was measured. Proposed isolator has potential for high dynamic isolation ratio and wideband operation. It may be developed more with careful design of capacitive and inductive loadings of the CRLH structure.

Characteristics of left-handed transducer for magnetostatic forward volume wave was analyzed with a help of Fourier integral, residues methods and numerical simulation by HFSS. Radiation characteristics were found with enhanced nonreciprocity which was compared with usually used fine wire transducer. To confirm theoretical results experiments were undertaken using single crystal slab and thin film of YIG ferrite. Additional radiating surface mode was observed with 40 dB isolation.

Transmission characteristics of the left handed (LH) ferrite microstrip line are significantly affected by the nonuniform bias magnetic field Hin, because strip conductors must be fabricated on the edge of the ferrite substrate. Three dimensional analysis is performed taking into account the non-uniform H in caused by the demagnetizing effect in the ferrite substrate. Analyzed result shows that, the nonuniform H in expands the frequency range and contributes to the improvement of the nonreciprocal characteristic of the LH ferrite microstrip line. Measured result more than 20 dB isolation with 3.2dB insertion loss and 1.52 GHz bandwidth are almost corresponding to the theoretical result.