Ik-Soo Chang

Miniaturized 3-dB ring hybrid terminated by arbitrary impedances

In the UHF or VHF band, the new design method of a small-sized 3-dB 0/spl deg//180/spl deg/ ring hybrid terminated by arbitrary impedances using both lumped and distributed elements is presented. At the center frequency of 900 MHz, the small sized 3-dB 0/spl deg//180/spl deg/ hybrid terminated by arbitrary impedances is designed, analyzed and tested. Good agreement is obtained between measured and predicted results. Since both lumped and distributed elements are used, the proposed hybrid occupies about 30% of an all distributed-type hybrid. >

The design of band-pass filters made of both dielectric and coaxial resonators

Two different kinds of resonators can be used to construct a microwave band-pass filter that has a low spurious response. The band-pass filter made with coaxial resonators and disk dielectric resonators shows a good spurious response.

Arbitrary termination impedances, arbitrary power divisions and small-sized ring hybrids

If a ring hybrid is terminated by arbitrary impedances, design equations can not be derived with conventional methods because symmetry planes for even and/or odd symmetries are not available. Therefore, under these conditions new design equations for ring hybrids have been derived. They can be applied to both ring hybrids with arbitrary termination impedances and arbitrary power division ratios. Also, new design equations for small sized ring hybrids have been developed. They allow that arbitrary power divisions, arbitrary termination impedances and specially small sized ring hybrids can be designed. On the basis of these derived design equations, a simulation of ring hybrids with 4 arc lengths of 75/spl deg/, arbitrary termination impedances and a power split ratio of 4 dB was performed using ideal CPS crossover.

Feedforward Amplifier using Equal Group-Delay Signal Canceller

In this paper, a new signal canceller that can matches an out-of-phase and a group delay of two path signals simultaneously is proposed. The simultaneous matching of the out-of-phase and the group delay time between two paths can makes a broadband signal cancellation possible. A feedforward linearizing power amplifier that adopts the proposed signal cancellers is fabricated on IMT-2000 base-station transmitting band. The main signal cancellation (or the 1st) loop of the fabricated feedforward amplifier cancel input signal more than 26.3dB and the intermodulation distortion (IMD) signal cancellation (or the 2nd) loop cancel IMD signal more than 15.2dB for 200MHz bandwidth. With the two-tone signals amplification process, the C/I ratio of the amplifier is improved 20.8dB, where the two tones are 2115MHz and 2165MHz, respectively

A design of planar elliptic bandpass filter using SMD type partially metallized rectangular dielectric resonators

In this paper, thin planar bandpass filter structures with elliptic, Chebychev, or notch filter response, using 2-D arrays of metallized rectangular dielectric waveguide type resonators on PCB are presented. Electrode pads on open-end surfaces (OEFs) of the resonator are used as coupling ports to microstrip lines. Because the resonant frequency of rectangular waveguide type resonator is not sensitive to height of the resonator, the filters can be used as a planar or thin filter structure on PCB like other SMD chip devices. A 4-pole elliptic function filter is designed and constructed. The measured frequency responses of the filter agreed well with theoretical predictions.

A design of magnetically tunable E-plane type waveguide filter

This paper presents a new design method for magnetically tunable E-plane waveguide filters with arbitrary characteristic inverter impedance. It is shown that the unilateral finline E-plane waveguide filter as well as the bilateral finline E-plane waveguide filter achieve the magnetically tunable characteristic. The X-band experimental results agree well with the simulated data.