This contribution introduces a novel, dielectric waveguide based, permittivity sensor. Next to the fundamental hybrid mode theory, which predicts exceptional wave propagation behavior, a design concept is presented that realizes a pseudo-transmission measurement approach for attenuating feed-side reflections. Furthermore, a transmission line length independent signal processing is introduced, which fosters the robustness and applicability of the sensor concept. Simulation and measurement results that prove the sensor concept and validate the high measurement accuracy, are presented and discussed in detail.

In this paper, we have investigated a new structure which combines dielectric cylinders with air-hole cylinders array, and analyzed the guiding problem for periodically dielectric waveguides by arbitrary shape of dielectric constants in the middle layer. In the numerical analysis, we examined an influence of the dielectric circular cylinder along a middle layer by using the energy distribution and complex propagation constants at the first stop band region compared with hollow dielectric cylinder. In addition, we also investigated the influence of dielectric structure with equivalence cross section compared with dielectric cylinders, and clarified an influence of dielectric structures in the middle layer by energy distribution analysis for TE0 mode.

In this paper, we have analyzed the guiding problem by dielectric waveguide with defects composed of dielectric circular cylinders array and deformed rhombic dielectric structure embedded in the middle layer and investigated the influence of energy flow for defect area by using the propagation constants at the guided area. From the numerical results, it is shown that we can obtain the confinement efficiency by rhombic dielectric structure compared with the deformed rhombic dielectric structure for both TE and TM modes.

For V-band applications, this paper presents a fully embedded multi-layer dielectric waveguide filter (DWGF) with very low insertion loss and small size, which does not need any more assemblies such as flip-chip bonding and bond wires. The top and bottom plane are grounded, and therefore, although we make a metal housing, there will be no resonance occurrences. Especially, the proposed structure is very suitable for MMICs interconnection because the in/output pads consist of conductor backed co-planar waveguide (CBCPW). The filter is formed incorporating metallized through holes in low temperature co-fired ceramic (LTCC) substrates with relative dielectric constant of 7.05. The total volume of the filter including transitions is 4.5 mm2.65 mm0.4 mm. A fabricated DWGF with four transitions shows an insertion loss and a return loss of 2.95 dB and less than 15 dB at the center frequency of 62.17 GHz, respectively. According to the authors' knowledge, the proposed filter shows the lowest insertion loss among the embedded multi-layer millimeter-wave filters ever reported for 60 GHz applications.

A technique to control the radiation pattern of an NRD-guide-compatible pyramidal horn antenna, which consists of a tapered dielectric rod inserted into the horn, was developed for multiple access LAN applications at 60 GHz. By using this simple technique, the half-power beamwidth can be controlled from 11to 40.

It is known that a high permittivity NRD guide suffers from irregular transmission phenomena. In this study, we clarified that this problem is caused by a mode coupling phenomenon between the operating and parasitic modes due to a small remaining asymmetrically air gap between the metal plates and high permittivity dielectric materials.

A flexible transmission line, consisting of a thin ceramic-compounding Teflon strip, was devised by using a high permittivity LSE-NRD guide. This transmission line has the advantage of changeable shape. Low-loss performance was confirmed by measuring the transmission loss of the 180 degree bend and the S-shaped curve in the 60 GHz frequency band.

A high permittivity LSE-NRD guide was applied to a planar antenna at 60 GHz. Emphasis was placed on compatibility between the high permittivity LSE-NRD guide and the conventionally used low permittivity LSM-NRD guide. Performance of the transition between two such types of NRD guides was optimized by using an electromagnetic simulator and the validity was experimentally demonstrated. A simple radiator, consisting of a tapered high permittivity LSE-NRD guide was fabricated and evaluated as to radiation characteristics. Since the radiator has a broad radiation pattern, it was employed in a primary radiator of a two-dimensional parabolic reflector to develop a new type of folded planar antenna at 60 GHz. This planar antenna has a double-layered structure. In the upper layer, a metalized dielectric substrate with a slotted array is excited by a rectangular-shaped oversized waveguide, and in the lower layer, an offset parabolic reflector is fed by the radiator. Measurement showed the half-power beam width of the fabricated antenna to be 2.5 degrees in the E and H planes, respectively, and the gain to be 35.3 dBi, thus indicating that a good pencil beam antenna was successfully developed in this manner.

A conventional waveguide filter is usually composed of a waveguide which is set with irises and posts inside. When dielectric material is not loaded inside the filter, the filter is too large to mount it on a planar circuit even if the frequency band is as high as the millimeter-wave band. In this paper, we propose a dielectric waveguide filter using LTCC (Low-Temperature Co-fired Ceramics) which can be mounted on a planar circuit. The dielectric waveguide filter using LTCC is composed of a dielectric-loaded waveguide including posts (via holes) and TEM-TE10 converters. The design method of the filter is shown and comparison of the simulated and the experimental results in the 6 GHz band is demonstrated. The simulated results agreed well with the experimental ones. To improve the attenuation characteristics, particularly at the above pass-band frequencies, an attenuation pole is added using a cross patch set inside the LTCC filter in the 25 GHz band. The effect of the cross patch is confirmed using the same simulation method as used for the 6 GHz band. As a result, it is confirmed that the cross patch is very useful for improving the attenuation characteristics at the above pass-band frequencies.

An NRD guide transmitter and a receiver were developed for a wireless multi-channel TV-signal distribution system at 60 GHz. The main emphasis was placed on a band-widening technique of the NRD guide beam-lead diode mount based on an electromagnetic field simulator, where each dimension of the beam lead diode mount was optimized. The agreement between the simulation and measurement is quite satisfactory. The up-converter fabricated by assembling a band-pass filter and a Schottky barrier diode mount has a good linearity as well as a flat output power of 2 dBm on the average over a bandwidth of at least 2 GHz. Moreover, the down-converter has a flat conversion loss performance of less than 7 dB in the same bandwidth. An NRD guide transmitter and a receiver characterized by small size and high performance were fabricated and successfully employed for the wireless distribution of TV signals for more than 100 channels.

A technique for the design of circular- and racetrack-shaped NRD guide ring resonators was developed based on the mode coupling theory. Besides the operating mode, a parasitic mode is generated at curved sections of the resonator as a result of the mode conversion. Resonance of the NRD guide ring resonator is derived by characteristic equations of the coupled modes and then employed in making the design diagrams, which are useful for determining the dimensions of the ring resonators. It is shown that the discrepancy between the experimental results and previous theory can be resolved by using the present theory. Low loss, small-sized ring resonators with curvature radii of less than 5.3 mm were fabricated at 60 GHz and a band rejection performance of more than 30 dB was observed. Moreover, a procedure for the design of the channel dropping filter was developed and a 2-pole filter, which has great advantages such as a low insertion loss of 1.2 dB and a compact size smaller than that of a golf ball, was successfully developed by using two racetrack-shaped ring resonators.

Transmission characteristics of a high permittivity NRD guide were investigated. A preferable operating mode of the high permittivity NRD guide was newly identified and the wide bandwidth and low loss nature of the millimeter-wave region were observed. Moreover, a technique for construction of a millimeter-wave antenna was developed based on the high permittivity NRD guide. The novelty of the present technique lies in the use of a simple radiator, which consists of a tapered dielectric strip of simple structure which has good compatibility with millimeter wave integrated circuits. Since this radiator has a broad radiation pattern, a new type of antenna compatible with millimeter-wave integrated circuits for marine radar use was fabricated by locating the radiator at the focal point of a cylindrical parabolic reflector. Suitable beam patterns with half-power beam widths of 4in the azimuth plane and 38in the elevation plane can be obtained at 35 GHz.

Two types of p-i-n diode devices, namely an amplitude shift keying switch and a phase shift keying switch, were developed by using an NRD guide at 77 GHz. In order to apply these devices to radar systems, an SPDT switch with a low insertion loss of less than 2.5 dB and a high isolation of more than 25 dB was fabricated by using the former switch. Moreover, a BPSK modulator, composed of the latter switch together with a circulator and a ceramic resonator loaded band-pass filter, was designed and evaluated for use in spread spectrum radar systems in this frequency range.

A multiport representation of the step junction of two circular dielectric waveguides of different size is given. Continuous spectral modes of the circular dielectric waveguide are discretized at a terminal plane by means of expressing their mode amplitudes in the form of infinite series of orthonormal Gaussian Laguerre function. Applying the mode matching technique, a multiport representation of the step junction is derived. Numerical examples are given where the results are tested for the conservation of power. Also the numerical results are compared with those from Marcuse's approximate methods.

Because 60 GHz frequency band has been allotted for the research and development purpose of millimeter wave systems in Japan, various circuit components and systems have been fabricated by using printed transmission lines. The NRD guide (nonradiative dielectric waveguide) is another candidate as a transmission medium for millimeter wave integrated circuit applications since its performance has been shown to be excellent in this frequency band. This paper is concerned with the development of a 60 GHz digital transceiver for millimeter wave LAN use based on NRD guide technologies. The trans-ceiver consists of frequency stabilized Gunn oscillator, circulator, PIN diode modulator, balanced mixer, directional coupler and transmitting and receiving pyramidal horn antennas. The notable advantages of the circuit components are the high reliability of the Gunn oscillator, the wide bandwidth of the circulator, and the high frequency operation of the PIN diode modulator beyond 100 Mbps. Interference between transmitted and received signals, which must be caused by coupling between transmitting and receiving antennas, is eliminated by simple techniques such as introducing filters in the base band and IF circuits. By using NRD guide digital transceivers, both-way data transmission between two computers can be achieved simultaneously and a 60 GHz wireless LAN system has been developed successfully.

The radiation and scattering characteristics of a metal-strip grating of finite extent printed on the surface of a dielectric waveguide are analyzed within a two-dimensional model. The diffraction properties are obtained from a solution to the problem of surface mode scattering by a finite number of metal strips, taking into account their mutual couplings. The analysis is based on the electromotive force technique which does not require a grating to be periodic. Obtained results concern the antenna applications of radiating gratings excited by the dominant TE or TM surface mode of the wavegude. The proposed approach can be applied not only to the design of radiators but also filters based on periodic strip gratings.

Considered is the theory of several dielectric waveguide phenomena for which the vector nature of the electromagnetic field is essential. These phenomena are the following rotation of the plane of polarization in chiral and twisted waveguides, Bragg's reflection in a twisted waveguide in a narrow frequency band, and excitation of a waveguide at a near-cutoff frequency.

The fundamental TE10 mode in a rectangular waveguide of a square cross section is degenerate with TE01 mode. A quarter wavelength resonator made of a dielectric square waveguide is, therefore, applied for a small-sized bandpass filter, just like dual mode filters for base stations in the mobile communication. In this paper, the methods to couple the two modes are first studied, including cutting a corner of the resonator and adding some metal electrodes on its end face. Both methods help to flow the rf current of the odd mode at the corner, resulting in decrease of the series inductance and thus increase of the resonant frequency. The coupling constant, that is proportional to the difference of the odd and even-mode's resonant frequency, can be controlled by the perturbations mentioned above. The coupling to the external circuit is adjusted by an electrode fabricated also on the end face. It is connected to a microstrip line and capacitively couples to the resonant modes. The coupling strength increases with the dimension of the electrode. The adjustment of the resonant frequency is carried out by the similar electrode on the end face and connected to the center of the side of the square cross section. The frequency decreases with the length of the electrode. The unloaded Q is measured to be of around 500 for 5510 mm resonator of εr=93. The optimum aspect ratio for the resonator is found in terms of the Q value. The simplest bandpass filter, i.e., a two-stage bandpass filter is designed and fabricated using 5510 mm resonator. It is mounted in a square hole made in a printed circuit board and excited by a microstrip line. The frequency characteristics are in good agreement with the expected values.

We describe a geometrical optics approach for the analysis of dielectric tapered waveguides. The method is based on the ray-optical treatment for wave-normal rays defined newly to waves of light in open structures. Geometrical optics fields are represented in terms of two kinds of wave-normal rays: leaky rays and guided rays. Since the behavior of these rays is different in the two regions separated at critical incidence, the geometrical optics fields have certain classes of discontinuity in a transition region between leaky and guided regions. Guided wave solutions are given as a superposition of guided rays that zigzag along the guides, all of which are totally reflected upon the interfaces. By including some leaky rays adjacent to the guided rays, we obtain more accurate guided wave solutions. Calculated results are in excellent agreement with wave optics solutions.

A modified beam propagation method based on the Galerkin's technique (FE-BPM) has been implemented and applied to the analysis of optical beam propagation in a tapered dielectric waveguide. It is based on a new calculation procedure using non-uniform sampling spacings along the transverse coordinate. Comparison with a conventional FE-BPM shows a definite improvement in saving computation time. The differences of a propagation field and a mean square power given by the proposed FE-BPM are discussed in comparison with the conventional FE-BPM.