This paper presents an X-band power-combined pulsed high power amplifier (HPA) based on the low insertion loss waveguide combiner. Relationships between the return loss and isolation of the magic Tee (MT) have been analyzed and the accurate design technique is given. The combination network is validated by the measurement of a single MT and a four-way passive network, and the characterization of the combined HPA module is designed, fabricated and discussed. The HPA delivers 200W output power with an associated power-added efficiency close to 40% within the frequency range of 7.8 GHz to 12.3 GHz. The combination efficiency is higher than 93%.

Based on the substrate integrated waveguide (SIW) technology, a new type of varactor-tuned radial power divider has been developed with a single bias supply. The varactors are used as tuning elements and allow for a frequency agile behavior. In addition, bandwidth characteristics have been analysed with group-delay. It has been measured with a single bias supply ranging from 6 V to 12 V that the center frequency of the power divider can be adjusted from 6.6 GHz to 7.2 GHz (600 MHz, 11.5%) while maintaining a low insertion loss (< 1 dB) in the passband.

A low-loss ultra-wide band (UWB) filter is presented, which uses miniaturized parallel coupled line along with an standard printed circuit board (PCB) technology. By analyzing even- and odd-mode impedances (in comparison with conventional parallel coupled lines) of miniaturized parallel coupled line, this structure provides tight coupling, thus, relaxing the requirements on physical dimensions width and spacing when designing broadband filters. A bandpass filter for Mode 1 (the first 3 sub-bands) in the 3.1-5 GHz band for Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB is realized and compared with a conventional parallel coupled line filter. The experimental results show as much as 0.9 dB insertion loss improvement over the conventional counterpart.

The authors propose a single-layer hollow-waveguide 8-way Butler matrix. All components of the Butler matrix are in a single layer which contributes to low-cost fabrication. To reduce the length of the couplers, a step structure is installed in the coupled region. 50% length reduction is obtained in comparison with the conventional design using reflection-suppressing posts in the coupled region. The total size of the matrix is 17.1λg6.0λg. The full structure of the matrix is fabricated by hollow waveguides at 22 GHz band and the total measured loss is only 0.25 dB.

This paper presents a theoretical study on transmission properties of bent optical waveguides of uniaxial anisotropic material. The waveguiding structure consists of two parallel straight slab waveguides connecting by an oblique section. By arranging the direction of the optical axis in the oblique section so that the wave normal always points to the same direction throughout the waveguiding structure, low loss transmission can be realized. The analysis of wave propagation through the structure is based on the finite difference beam propagation method. Numerical results indicate that by optimally arranging the direction of the optical axis in the oblique section power coupling coefficients better than 95% can be obtained for any tilt angle of the oblique section when the tilt angle is smaller than 2 degrees. Some field distributions are also presented along the waveguiding structure.