This paper suggests a new type of 180-degree 3 dB hybrid, which consists of a cylindrical cavity and four E-plane rectangular waveguides radially coupled with it, and shows that good hybrid properties are realized by modifying the positions of the four input/output waveguides and the radius of the cylindrical cavity that are determined by the field distribution of the TE111 resonant mode. Moreover, a method of broadening the bandwidth with additional impedance steps is described. The present hybrid is marked by simple structure, and hence is useful for applications at millimeter wave frequencies and to high-power microwave systems. Experimental verification is additionally shown.

This paper presents a miniaturized reverse-phase hybrid ring by the use of shunt capacitors, and successfully designs a very miniature hybrid ring of a 0.28-wavelength circumference with a wide bandwidth comparable to the regular reverse-phase hybrid ring based on the equivalent admittance approach. Moreover, a method of broadening the bandwidth with adding a matching network consisting of a very short transmission line and two shunt capacitors at each port is also described. The validity of the proposed design is demonstrated by electromagnetic simulator (Sonnet em) for a uniplanar hybrid ring.

This letter presents formulae by means of which AM and PM noise in mutually synchronized oscillators with asymmetrical locking forces can be estimated directly from parameters of the oscillators system. In particular, coupling phase dependence of PM noise conservation rates is studied in detail.

In this paper, we consider a parallel ring-line rat-race circuit realized by replacing some parts of the ring-lines with composite right-/left-handed transmission lines (CRLH-TLs). For a conventional rat-race circuit, the minimum coupling factor is limited by the highest impedance of the ring-lines that can be manufactured by general printed circuit board (PCB) technologies. However, the coupling factor of the parallel ring-line type rat-race circuit proposed in this paper is determined by the difference between the admittances of the parallel ring-lines. As a result of designing parallel ring-line rat-race circuits having coupling factors of $-20$ and $-30$,dB for an operation frequency of 4,GHz, the proposed rat-race circuit realizes broadband characteristics of about 35.5% according to the numerical results for the $-20$,dB circuit. Furthermore, broadband characteristics including reflection, isolation, and couplings can be maintained for the fabricated $-20$,dB rat-race circuit up to an input power of 40,dBm.

This paper describes a novel Wilkinson power divider operating at two arbitrary different frequencies. The proposed divider consists of two-section transmission lines and a series RLC circuit connected between two output ports. The circuit parameters for a dual-band operation are derived by the even/odd mode analysis. Equal power split, complete matching, and good isolation between two output ports are numerically demonstrated. Dual-band and broadband Wilkinson power dividers can be successfully designed. Finally, verification of this design method is also shown by electromagnetic simulations and experiments.

Recently, a multi-way TE10 mode power divider based on the TE10-TEp0 mode transducers consisting of a linearly arranged single-mode waveguide (SMWG) and an over-moded waveguide (OMWG) has been reported. However, the multi-way power divider based on the present mode transducer results in poor isolation and output matching characteristics. In this paper, an improvement of the isolation and the output matching characteristics is attempted by inserting the resistive sheets in the OMWG. It is shown that the isolation characteristics of about 20 dB are achieved by adjusting the dimensions of the resistive sheets. The validity of the design results is confirmed by an experiment.

This paper treats a new-type power combining system of four oscillators equally coupled to one another through an eight-port hybrid. This system is marked by easy analyzability and adjustability from its symmetrical construction. In addition, a combined power from the four oscillators is distinguishably delivered to an arbitrary port of four output ports, and hence can be switched in four ways. Experimental corroboration is presented also.

This paper proposes a new type of compact waveguide directional coupler, which is constructed from two crossed E-plane rectangular waveguide with two metallic posts in the square junction and one metallic post at each port. The metallic posts in the square junction are set symmetrically along a diagonal line to obtain the directivity properties. The metallic post inserted at each input/output waveguide port can realize a matched state. Tight-coupling properties 0.79-6 dB are realized by optimizing the dimension of the junction and the positions/radii of the posts. The design results are verified by an em-simulator (Ansoft HFSS) and experiments.

This paper proposes a novel waveguide intersection separating two H-plane waveguide systems from each other. If a four-port network in a four-fold rotational symmetry is completely matched, it has necessarily intersection properties. The proposed waveguide intersection consists of a square H-plane waveguide planar circuit connected four input/output waveguide ports in a four-fold rotational symmetry, and several metallic posts inserted at the junction without destroying the symmetry to realize a perfect matching. By optimizing the circuit parameters, high isolation properties are obtained in a relatively wide frequency band of about 8.6% for return loss and isolation better than 20 and 30 dB, respectively, for a circuit designed at 10 GHz. The proposed waveguide intersection can be analyzed by H-plane planar circuit approach, and possess advantages of compactness, simplicity, and high-power handling capability. Furthermore, an SIW intersection is designed by applying H-plane planar circuit approach to a waveguide circuit filled with dielectric material, and high isolation properties similar to H-plane waveguide intersection can be realized. The validity of these design concepts is confirmed by em-simulations and experiments.

We attempt to design and fabricate of a 4×4 Butler matrix for short-millimeter-wave frequencies by using the microfabrication process for a polytetrafluoroethylene (PTFE) substrate-integrated waveguide (SIW) by the synchrotron radiation (SR) direct etching of PTFE and the addition of a metal film by sputter deposition. First, the dimensions of the PTFE SIW using rectangular through-holes for G-band (140-220 GHz) operation are determined, and a cruciform 90 ° hybrid coupler and an intersection circuit are connected by the PTFE SIW to design the Butler matrix. Then, a trial fabrication is performed. Finally, the validity of the design result and the fabrication process is verified by measuring the radiation pattern.

The microfabrication technique based on synchrotron radiation (SR) direct etching process has recently been applied to construct PTFE microstructures. This paper proposes a PTFE substrate integrated waveguide (PTFE SIW). It is expected that the PTFE SIW contributes to the improvement of the structural strength. A rectangular through-hole is introduced taking the advantage of the SR direct etching process. First, a PTFE SIW for the Q-band is designed. Then, a cruciform 3-dB directional coupler consisting of the PTFE SIW is designed and fabricated by the SR direct etching process. The validity of the PTFE SIW coupler is confirmed by measuring the frequency characteristics of the S-parameters. The mechanical strength of the PTFE SIW and the peeling strength of its Au film are also additionally investigated.

It has been reported that a left-handed waveguide can be constituted using cutoff TE10 mode of rectangular waveguide. Because the cutoff TE10 mode shows effectively negative permittivity, the left-handed mode propagates by adding series capacitance in the form of short- or open-stubs. This paper suggests a constitution method of left-handed waveguides using cutoff TM mode. In this case, the cutoff TM mode shows effectively negative permeability. Therefore, a left-handed waveguide can be constituted by adding parallel inductance. In this paper, two types of the left-handed waveguides are designed using circular TM01 mode and rectangular TM11 mode, and the dispersion characteristics are numerically investigated. The validity of the constituting principle is confirmed by an experiment.

The microfabrication technique based on SR (Synchrotron Radiation) direct etching process has recently been applied to construct PTFE microstructures. This paper attempts to fabricate an integrated PTFE-filled waveguide Butler matrix for short millimeter-wave by SR direct etching. First, a cruciform 3-dB directional coupler and an intersection circuit (0-dB coupler) are designed at 180 GHz. Then, a 4×4 Butler matrix with horn antennas is designed and fabricated. Finally, the measured radiation patterns of the Butler matrix are shown.

The present paper treats the analysis and design method of the (H)NRD guide and E-plane rectangular waveguide integrated structures on the basis of the transverse resonance technique. The analysis is made by assuming a resonant cavity short-circuited at appropriate reference planes and considering the cavity as a waveguide discontinuity problem in the transverse direction. The resonant lengths are determined from the transverse equivalent circuit, and the scattering parameters are calculated from the lengths. We analyze (H)NRD discontinuities and design two types of HNRD guide to E-plane waveguide transitions and a directional coupler composed of HNRD and E-plane waveguide. The theoretical results are in good agreement with results calculated by an EM-simulator.

This paper presents a design procedure of a directional coupler consisting of a twofold symmetric four-port circuit with four identical matching networks at each port. The intrinsic power-split ratio and the equivalent admittance of the directional coupler are formularized in terms of the eigenadmittances of the original four-port without the matching networks. These formulas are useful for judgment on the realizability of a directional coupler in a given circuit structure and for design of the matching networks. Actually, the present procedure is applied to designing various quadrature hybrids and directional couplers, and its practical usefulness as well as several new circuit structures are demonstrated.

A broadband cruciform substrate integrated waveguide coupler is designed based on the planar circuit approach. The broadband property is obtained by widening the crossed region in the same way as rectangular waveguide cruciform couplers. As a result, a 3 dB coupler with fractional bandwidth of 30% is realized at 24 GHz.

This paper presents a new quarter-wavelength microstrip coupler compensated with a periodic sequence of floating metallic strips in the slots on the inner edges. After describing the characteristics of the coupled-line, as an example, a 15-dB coupler is designed and a high directivity of 30 dB or more in theory is obtained over a full band of a single-section coupler. Next, couplers with various coupling factors are designed, and the usefulness for very loose coupling is demonstrated. Furthermore, a three-section coupler is designed to show the effectiveness in a wide frequency range. The validity of the design concept and procedure is confirmed by electromagnetic simulations and experiments.

This paper treats multi-way microstrip power dividers composed of multi-step, multi-furcation, and corners. Since the design procedure is founded on the planar circuit approach in combination with the segmentation method, optimization of the circuit configuration can be performed in a reasonable short computation time when applying the Powell's optimization algorithm. Actually, broadband 3- and 4-way power dividers with mitered bends are designed, and fractional bandwidths of about 90% and 100% are realized for the power-split imbalance less than 0.2 dB and the return loss better than -20 dB, respectively. The validity of the design results is confirmed by an EM-simulator (HFSS) and experiments.

A planar-circuit-type 3 dB hybrid consisting of a four-port disk-shaped resonator is reinvestigated. A great improvement in the characteristics is obtained by rearranging the four ports upon consideration of the higher order resonator modes without loss in simplicity of the structure.

The metallic waveguide is one of many effective media for millimeter- and submillimeter-waves because of the advantage of its low-loss nature. This paper describes the fabrication method of PTFE-filled waveguide components with the use of the SR (synchrotron radiation) direct etching process of PTFE, sputter deposition of metal, and electroplating. PTFE is known as a difficult material to process with high precision. However, it has been reported that PTFE microstructures can be fabricated by the direct exposure to SR. First, an iris-coupled waveguide BPF with 5-stage Chebyshev response is designed and fabricated for the Q-band. It is demonstrated that the present process is applicable for the fabrication of the practical components inclusive of narrow patterns. Then, a cruciform 3 dB coupler with air-filled posts is designed and fabricated for the Q-band. Directivity and matched state of the coupler can be realized by “holes” in the dielectric material. The measurement results are also shown.