Chih-Chun Chang

Wideband LTCC 60-GHz Antenna Array With a Dual-Resonant Slot and Patch Structure

This paper presents a wideband 60-GHz antenna array with a dual-resonant slot-patch structure. A multilayered low-temperature co-fired ceramic substrate was used for antenna fabrication. A half-wavelength resonant slot was designed with a backed substrate-integrated waveguide (SIW) cavity to enhance the front radiation. The inverted microstrip center-fed structure was designed for easy signal excitation and superior impedance matching. A parasitic patch was also applied to enhance for bandwidth and gain enhancement. The effects of the SIW cavity-backed slot antenna with and without parasitic patches were empirically examined. The simulated results show that adding parasitic patches increased the resonance of the poles and improved antenna gain by 1.85 dB and bandwidth by 9%. A 2 × 2 dual-resonant slot-patch antenna array was designed to further enhance the gain and bandwidth. The equipment setup for on-chip measurements of gain and radiation patterns was established. The measured S11 showed a wide bandwidth of 23%. The measured gain for the four-element antenna array was 9 dBi with slight fluctuations over the 57-64-GHz frequency range.

LTCC Multilayered Substrate-Integrated Waveguide Filter With Enhanced Frequency Selectivity for System-in-Package Applications

This paper presents a cross-coupled bandpass filter with stacked substrate-integrated waveguide cavities on low-temperature cofired ceramic substrates. The proposed filter has a local multipoint distribution service band with a novel same-side-feed input/output structure. Conventionally, a cross-coupled structure generates only a single pair of transmission zeros. The proposed filter can generate two pairs of transmission zeros beside the passband, thereby providing an excellent cutoff rate in the stopband and improved frequency selectivity. The additional pair of transmission zeros is created by the same-side-feed structure, which constructs an additional source-load coupling path without increasing the circuit size. A multipath coupling diagram is used to illustrate the conformation of the second pair of transmission zeros and predict its behavior. The experimental filter exhibits responses centered at 27.95 GHz with an insertion loss of -2.8 dB, and a bandwidth of 9%. Two pairs of transmission zeros (at 26.3 and 29.6 GHz, and at 23.2 and 37 GHz) around the passband were obtained, achieving excellent selectivity and a wide stopband.

Differential-Fed Patch Antenna Arrays With Low Cross Polarization and Wide Bandwidths

In this letter, two differential-fed Ku-band 2 × 2 patch antenna arrays with low cross polarization and wide bandwidths were developed using multilayer printed circuit board (PCB) technology. The patch elements in Design I were fed differentially, whereas the patches in Design II were single-ended. However, Design II is differential if the array is considered as a whole. The experimental demonstration revealed that Design I achieved a 10-dB impedance bandwidth of 15.3%. The measured gain was 10.41 dBi at 12.62 GHz with low cross polarization of -17.5 dB in the E-plane and -20.2 dB in the H-plane. Design II exhibited a 10-dB impedance bandwidth of 12.8%. The measured gain was 12.32 dBi at 13 GHz with cross polarization of -17.7 and -17 dB in the E-plane and H-plane, respectively. Design II achieves performance levels similar to that of Design I, but comprises a simple and compact feed network.

Cross-coupled bandpass filters using QMSIW cavities and S-shaped slot coupling structures

This paper presents a novel cross-coupled bandpass filter using quarter-mode substrate integrated waveguide (QMSIW) cavities. QMSIWs with fictitious magnetic walls on two sides retain similar performances of the conventional SIW, but are almost one fourth the size. The dominant resonant mode of the proposed resonator is the TE101 mode. A special negative coupling scheme with symmetrical S-shaped slots on the top and bottom metal planes connected by metallic vias is developed. The proposed structure provides more design flexibility in arranging the pitch of vias owing to the extended slot length. The experimental filter has a measured fractional bandwidth of 7.44% at 5.57 GHz with a return loss better than −18.1 dB and an insertion loss less than −2 dB.

A Broadband Patch Antenna Array With Planar Differential L-Shaped Feeding Structures

This study involved developing a differential patch antenna array featuring a wide bandwidth and improved radiation patterns. The proposed patch array was fed by a planar, aperture-coupled, L-shaped feeding structure to achieve wideband operation. The differential feeding structure improved the current distribution of resonant modes, substantially improving the symmetry of radiation patterns. The array without differential excitation revealed an apparent deflected peak located at an observation angle of 10° at 13.7 GHz. However, using the proposed differential-fed structure, the location of this peak returned to 0°. The measured results indicated a wide impedance bandwidth of 21.5% and a stable gain varying from 10.3 to 11.52 dBi over the frequency range of 11.6-15 GHz.

V-band cross-coupled SIW band-pass filter with an antisymmetric U-slot negative coupling structure

This study presents an low-temperature cofired ceramic (LTCC) V-band cross-coupled band-pass filter using substrate-integrated waveguide cavities. Two antisymmetric U-shaped slots connected by via is proposed to construct the negative coupling structure, which is simple and especially useful for 60 GHz applications. Moreover, the U-slot structure possesses a wide range of realizable coupling coefficients from −0.008 to −0.075. An experimental LTCC fourth-order filter was fabricated for demonstration, achieving a bandwidth of 12% (7.2 GHz) at 59.6 GHz with superior frequency selectivity.

Substrate integrated waveguide quasi-elliptic bandpass filter with meander-slot coupling structures

This paper presents a novel cross-coupled bandpass filter using substrate integrated waveguide (SIW) cavity resonators. A special negative coupling scheme with symmetrical meander slots on the top and bottom metal planes is applied. The design strategies and performances are introduced and discussed in detail. The proposed fourth-order filter shows a fractional bandwidth of 8.2% at 15.24 GHz with a return loss of better than -17.25 dB, an insertion loss of less than -1.8 dB, and excellent frequency selectivity.

Dual-band quadrature coupler with high frequency ratio using cascaded coupled-line structures

This paper presents a dual-band quadrature coupler with a cascaded coupled-line structure. Conventionally, the parallel coupled lines with an electrical length of 90° only operate at a single frequency. The proposed design achieves dual-band operation by cascading three coupled-line sections with appropriate electrical lengths, which has the advantage of high frequency ratio. The design strategy was validated by designing an experimental dual-band quadrature coupler. The measured results show excellent dual-band performance of -10.6 and -10.8 dB coupling level at 0.84 and 5.17 GHz with bandwidths of 47.6% and 9.1%, respectively. The measured return loss and isolation were better than -18 and -22 dB, respectively, and a phase difference of 90.5° and -88.5° at the dual center frequencies between the two output ports.

Coupled-line coupler with controllable bandwidth

A new approach for designing a parallel coupled-line coupler with controllable bandwidth is presented. The proposed circuit consists of one coupled-line section and four open- or short-circuited stubs tapped at the ends of coupled lines. The adjustable range of fractional bandwidth is from 7% to 45% controlled by adjusting the impedance of stubs. An experiment coupler operating at 2.5 GHz was fabricated for demonstration with a bandwidth of 17.6%.