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.

This paper presents a design method of multi-stage, multi-way microstrip power dividers with the aim of constructing a compact low-loss power divider with numbers of outputs. First, an integration design technique of power dividers composed of multi-step, multi-furcation and mitered bends is described. Since the analytical technique is founded on the planar circuit approach combined with the segmentation method, the optimization of the circuit patterns can be performed in a reasonable short computation time. Next, the present method is applied to the design of broadband Nn-way power dividers such as 32-way power divider consisting of 3-way dividers in two-stage structures, respectively. In addition, a 12-way power divider constructed from a series connection of a 3-way and three 4-way dividers is designed. The dividers equivalently contain a 3-section Chebyshev transformer to realize broadband properties. As a result, the fractional bandwidths of nearly 85% and 66.7% for the power-split imbalance less than 0.2 dB and the return loss better than -20 dB are obtained for the 9- and 12-way power dividers, respectively. The validity of these design results is confirmed by a commercial em-simulator (Ansoft HFSS) and experiments.

Directional couplers with flat coupling are designed by using an asymmetrical coupled-HNRD-guide consisting of two HNRD guides of different cross sections arranged closely. First, propagation characteristics of the asymmetrical coupled-HNRD-guide are analyzed by the transverse resonance technique. Next, the whole directional couplers including tapered sections are designed from the S-parameters of the coupled HNRD guides derived from a superposition of the even-like and odd-like modes. Finally, the validity of the design procedure is confirmed by an em-simulator (HFSS).

Full-wave FD-TD analysis has been carried out for coaxial probes inserted into waveguides. Both single and symmetrically placed paired coaxial probe structures have been discussed and we have revealed the relation between equivalent circuit parameters and structural parameters of the coaxial probes including cases for large diameter and extension length, which is useful for practical waveguide circuit design. The equivalent circuit parameters calculated from the scattering parameters agreed well with corresponding measured data. From the calculated field in a waveguide, field concentration at sharp edges of probe sole or base, which ought to be taken into account for high power application design has been also discussed. Besides, amplitudes of higher order modes in waveguides excited by coaxial probes or pairs of coaxial probes has been calculated so as to estimate the range beyond which higher order modes decay sufficiently. This estimation is necessary for simple and easy design of probe using circuit theory.

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.

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.