Yukihiro Tahara

A Compact Forward Coupler Using Coupled Composite Right/Left-Handed Transmission Lines

A novel forward coupler using coupled composite right/left-handed (CRLH) transmission lines (TLs) is presented. Forward coupling is enhanced by the CRLH TLs, which have a considerable difference between the effective phase constants in the even and odd modes. A 10-dB forward coupler using the coupled CRLH TLs is simulated and experimentally demonstrated in the S-band. Its coupled-line length is reduced to half that of the conventional right-handed forward coupler with the same coupling.

A broadband three-way tapered-line power divider with several strip resistors

A novel three-way power divider using tapered lines is presented. It has several strip resistors which are formed like a ladder between the tapered-line conductors to achieve a good output isolation. The equivalent circuits are derived with the EE/OE/OO-mode analysis based on the fundamental propagation modes in three-conductor coupled lines. The fabricated three-way power divider shows a broadband performance in input return loss which is greater than 20 dB over a 3:1 bandwidth in the C-Ku bands.

A low-loss serial power combiner using novel suspended stripline couplers

This paper describes a serial power combiner which consists of novel suspended stripline couplers. The suspended stripline couplers have additional parallel capacitances to improve their directivities. The fabricated three-way power combiner has realized a good performance in insertion loss which is less than 0.23 dB over a bandwidth of 10% in the S-band.

A stripline power divider with insensitive to resistance variations using a parallel resistor pair

The characteristics of a Wilkinson power divider frequently degrade when an isolation resistor in the Wilkinson power divider is formed by a resistance film because the resistance changes caused by manufacturing errors. In this paper, we present a stripline power divider that is insensitive to resistance variations, using a parallel resistor pair. In the proposed divider, two parallel resistors connected through 1/4-wavelength lines are placed between two output ports. When the resistance of the two resistors is changed because of manufacturing errors, the characteristics of the proposed divider remain stable because the total resistance of the resistor pair hardly changes owing to the connection of the two resistors through the 1/4-wavelength lines, which function as impedance transformers. The proposed divider was simulated and experimentally demonstrated in the X-band. The return loss and isolation in the experiments were lower than -20 dB in a 30.2% bandwidth when the resistance was changed to +50%.

A Broadband Traveling-Wave Power Divider/Combiner using Asymmetric Tapered-Line Power Dividers

A compact and broadband traveling-wave power divider/combiner cascading 1:1:2 three-way and 1:1 two-way power dividers is presented. Both tapered-line power dividers have several strip resistors to obtain sufficient output isolations. Additional open stubs applied to the 1:1:2 three-way tapered-line power divider compensate phase velocity difference between asymmetrically coupled tapered lines. The fabricated four-way power divider/combiner shows broadband performances which are a 0.4-dB insertion loss and a 14-dB return loss at all ports over a 3:1 bandwidth in the C-Ku bands.