Tae-Soon Yun

Orientation effect on microwave dielectric properties of Si-integrated Ba0.6Sr0.4TiO3 thin films for frequency agile devices

The effect of texture with (100) and (110) preferred orientations on dielectric properties of Ba0.6Sr0.4TiO3 (BST) thin films grown on SrO (9nm) and CeO2 (70nm) buffered Si substrates, respectively, was investigated. The coplanar waveguide (CPW) phase shifter using (100) oriented BST films on SrO buffered Si exhibited a much-enhanced figure of merit of 24.7°∕dB, as compared to that (10.2°∕dB) of a CPW phase shifter using (110) oriented BST films on CeO2 buffered Si at 12GHz. This work demonstrates that the microwave properties of the Si-integrated BST thin films are highly correlated with crystal orientation.

Ku-band transition between microstrip and substrate integrated waveguide (SIW)

In this paper, a Ku-band planar transition between microstrip and substrate integrated waveguide at satellite communication band is discussed. The SIW is one of alternatives for packaging the microwave components on the same substrate. The transition structure suggested in this paper shows the insertion loss of 0.7 dB at 12 GHz including transmission line of full wavelength.

Iris waveguide bandpass filter using substrate integrated waveguide (SIW) for satellite communication

In this paper, an iris waveguide filter with substrate integrated waveguide (SIW) structure at satellite communication band is discussed. The SIW structure is realized by via-holes on the substrate and shows a possibility of integration with other circuits. The iris waveguide filter has the insertion loss of 3.36 dB, the return loss of about 20 dB, and bandwidth of 3 %. Also, the iris waveguide filter using SIW has a sharp skirt characteristic.

Coplanar ferroelectric phase shifter on silicon substrate with TiO/sub 2/ buffer layer

In this paper, a BST coplanar phase shifter with differential phase shift of 98/spl deg/ at 50 V and FoM of 46.7/spl deg//dB has been realized. The potential feasibility of integrating BST films into Si substrate as microwave phase shifter and/or coplanar waveguide tunable devices with TiO/sub 2/ thin film buffer layer has been successfully demonstrated. TiO/sub 2/ as buffer layer has been successfully grown onto Si substrate by ALD (atomic layer deposition).

Ferroelectric Thin-Film-Based Electrically Tunable Bandpass Filters

We report on gold/Ba 0 . 5 Sr 0 . 5 TiO 3 (BST) ferroelectric thin film C-band tunable bandpass filters (BPFs) designed and fabricated on magnesium oxide substrates using three different structures: microstrip, coplanar waveguide (CPW), and conductor backed coplanar waveguide (CBCPW). The two-pole filters were designed for a center frequency of 5.89, 5.88, or 5.69 GHz with bandwidths of 3, 9, or 7%, respectively. The BST-based CPW filter offers a higher sensitivity parameter as well as a lower loss parameter compared to the BST tunable two-pole microstrip filter and CBCPW filter. With an applied voltage of 40 V, the tuning range for the BPF with CPW structure was determined to be 170 MHz.

Design of Tunable Band-pass Filters and Phase Shifters Using BST Thin Film

In this paper, the band-pass filters (BPFs) and phase shifters using BST thin film are presented. Filters are consisted of Microstrip, Coplanar Waveguide (CPW), and conductor backed CPW (CBCPW) structures and phase shifters are consisted of CPW line and CPW with slit structures to improve phase shift effect. From the measurement results, the Microstrip, CPW, and CBCPW bandpass filters show the center frequencies of 6.61 GHz, 6.31 GHz, and 6.21 GHz with the insertion losses of 7.33 dB, 5.83 dB, and 6.83 dB, respectively at the bias voltage of 40 V. The tuning range for the bandpass filters is determined as 3%~8%. From the experiments, the CPW line and the CPW with slit phase shifters show the insertion losses of 1.9 dB and 2.4 dB at the bias voltage of 30 and the phase shifts of 9.8° and 10.6° at 16 ~ 18 GHz, respectively.

Millimeter Wave Compact Branch Line Coupler Using Metal–Air–Metal Capacitors

In this paper, a compact branch line coupler fabricated on a GaAs substrate using surface micromachining. It is composed of a dielectric-supported air-gapped microstrip line (DAML) structure, which is a low-loss transmission line with an air-post and is useful for integration with other micro electro-mechanical system (MEMS) and/or MMIC components. The size reduction of the branch line coupler is accomplished by the insertion of metal–air–metal (MAM) capacitors within the structure. The coupler shows an isolation characteristic of approximately 21 dB and differences in magnitude and phase of less than 0.3 dB and 2°, respectively.

Influence of narrow transverse slit in ferroelectric based voltage tunable phase shifter

We report on gold/Ba0.5Sr0.5TiO3 (BST) ferroelectric thin film Ku-band phase shifters designed and fabricated on MgO substrates using two different structures; the coplanar waveguide (CPW) meander line phase shifter and the new phase shifter with narrow transverse slits in the ground plane of the CPW structure. The ability of these devices to provide a variable phase shift is based on the change in dielectric constant of BST with an applied dc bias. The phase shifter with narrow transverse slits showed larger phase shift capability than that of the conventional meander line phase shifter. In the former phase shifter, the phase shift of about 10.6 as a maximum value for the frequency range from 16 GHz to 18 GHz was obtained. In the latter, the phase shift of 9.7 deg at 18 GHz and at an applied voltage of 30 V was measured.

New Tunable Microwave Ba0.6Sr0.4TiO3/MgO Phase Shifters Using Interdigital Capacitors and Slit-Inductors

In this paper, we report on the role of slit-inductors in notably improving phase shifting capabilities in Ba0.6Sr0.4TiO3 (BST) tunable phase shifters utilizing interdigital capacitor (IDC) structure. The IDC-based coplanar waveguide (CPW) phase shifter with slit-inductors fabricated on (100) oriented BST films deposited on MgO substrates exhibits a much enhanced phase difference of 35.52°, as compared to that (25.23°) of the IDC-based phase shifter at 12 GHz. The figure of merit (FoM) of the IDC-based phase shifters with slit-inductors shows larger value of 43.60°/dB as a result of improving phase shifting while retaining an appropriate insertion loss compared to that (35.67°/dB) of the IDC-based phase shifter without slit-inductor. This work demonstrates potential use of slit-inductors for producing high-performance CPW based BST tunable elements in microwave circuit.

Tunable stepped impedance resonator bandpass filter using ferroelectric materials

In this paper, a stepped impedance resonator (SIR) bandpass filter using BST thin film as a tunable device has been discussed. For the analysis of relative dielectric constant of BST thin films, the BST interdigital capacitor (IDC) is fabricated with fingers width and gap of 10 mum and 5 mum, respectively, and the capacitance of IDC is 0.951 pF and the relative dielectric constant of BST thin film is 1,097 at 6 GHz. The tunable SIR bandpass filter using BST thin films is designed with coupling section of 22deg and tapped feeding and has been successfully demonstrated with the thickness of BST thin films of 500 mn on the MgO substrate. The center frequency of the tunable SIR bandpass filter is moved from 6.15 GHz to 6.29 GHz at 50 V bias with about 3% bandwidth.