Siew Bee Yeap

Gain-Enhanced 60-GHz LTCC Antenna Array With Open Air Cavities

The gain of low temperature co-fired ceramic (LTCC) patch antenna arrays operating at 60 GHz is enhanced by introducing open air cavities around their radiating patches. The open air cavities reduce the losses caused by severe surface waves and dielectric substrate at millimeter-wave (mmW) bands. The arrays are excited through either a microstrip-line or stripline feed network with a grounded coplanar-waveguide (GCPW) transition. The GCPW transition is designed so that the antenna can be measured with the patch array facing free space therefore reducing the effect of the probe station on the measurement. The proposed antenna arrays with the open air cavities achieves gain enhancement of 1-2 dB compared to the conventional antenna array without any open air cavity across the impedance bandwidth of about 7 GHz for |S11| ≤ - 10 dB at 60-GHz band.

Microstrip Patch Antennas With Enhanced Gain by Partial Substrate Removal

A method to enhance gain of a microstrip patch antenna is investigated by partially removing the substrate surrounding the patch. The partial substrate removal reduces the losses due to surface waves and dielectric substrate. The effects of substrate removal in different configurations on the gain of the antenna are studied numerically and validated experimentally. Compared to a conventional patch antenna, the antennas with partial substrate removal can enhance gain, for example, up to 2.7 dB. Furthermore, it is observed that the enhancement of gain is more due to loss reduction of surface waves and dielectric substrate than increased patch size when the effective dielectric constant of substrate is lowered. Such a technique can be applied in designs operating at higher frequencies whereby surface wave and substrate losses are more significant though the 2.4-GHz design is exemplified here for ease of fabrication and measurement purposes.

77-GHz Dual-Layer Transmit-Array for Automotive Radar Applications

A 77-GHz transmit-array on dual-layer printed circuit board (PCB) is proposed for automotive radar applications. Coplanar patch unit-cells are etched on opposite sides of the PCB and connected by through-via. The unit-cells are arranged in concentric rings to form the transmit-array for 1-bit in-phase transmission. When combined with four-substrate-integrated waveguide (SIW) slot antennas as the primary feeds, the transmit-array is able to generate four beams with a specific coverage of ±15°. The simulated and measured results of the antenna prototype at 76.5 GHz agree well, with gain greater than 18.5 dBi. The coplanar structure significantly simplifies the transmit-array design and eases the fabrication, in particular, at millimeter-wave frequencies.

Metamaterial magneto inductive lens for magnetic resonance imaging

A metamaterial magneto inductive lens is presented for the coil design in magnetic resonance imaging (MRI) applications, which is expected to enhance the magnetic field intensity of surface coils for improvement of the signal to noise ratio (SNR) of the MRI systems. The split-ring based lens is constructed into a pair of parallel two-dimensional arrays, that is, a metamaterial magneto inductive lens, providing minimum loading to the coil. Measurements show that the magnetic field intensity of the coil with metamaterial magneto inductive lens is improved about 2 dB at 295 MHz over a conventional coil at a distance of 10 mm, which is promising for pre-clinical study in a 7T MRI system at 300 MHz band.

140-GHz 2×2 SIW horn array on LTCC

A 2×2 LTCC horn array is presented. The antenna is based on substrate integrated waveguide (SIW) technique whereby the flare of the horn is designed in vertical steps of the LTCC layer. The proposed 2×2 horn array is fed through horizontal as well as vertical power dividers. A LTCC slab is designed as a phase corrector in front of each horn. The measured impedance bandwidth for |S11|=-10dB is about 9 GHz and the simulated gain is around 13.3 dBi at 140 GHz. The antenna is compatible with system in package (SiP) as well as providing end-fire radiation.

Metamaterial lens for magnetic resonance imaging

A metamaterial lens is presented for magnetic resonance imaging (MRI) application, which is expected to enhance the magnetic field intensity of the surface coil and improve the signal to noise ratio (SNR) of the MRI system. The lens is based on a split-ring constructed into a three dimensional cuboid, providing permeability μ = -1. Measurements show that the improvement of a metamaterial lens-based coil over a conventional coil is 4.2 dBi at 282MHz, which is promising for pre-clinical study in a 7T MRI system at 300 MHz band.

MRI coils using metamaterials

Metamaterial based radio frequency (RF) surface coils are investigated for magnetic resonance imaging (MRI) applications. The utilization of the metamaterial is expected to enhance the magnetic field intensity of the surface coils and improve the signal to noise ratio (SNR) of the MRI system. Two types of metamaterials, namely the metamaterial structures with negative permeability (μr) or high permeability, are co-designed with the RF coils. The metamaterial based coils at ultra-high frequency (UHF) of 300 MHz for 7 Tesla MRI system exhibit enhanced magnetic field intensity compared to a conventional coil.

Substrate-integrated antennas at 60/77/140/270 GHz

The recent research and development of the planar substrate-integrated millimeter-wave/sub-millimeter-wave antenna technologies are reported. The selected planar antenna designs fabricated onto print circuit board (PCB) or low temperature co-fired ceramic (LTCC) substrate operating at 60/77/140/270-GHz bands are addressed.

Antenna technologies for 60 GHz applications

In this paper, the wafer transfer technology (WTT) and the low-temperature co-fired ceramic (LTCC) technology are employed for 60 GHz antenna designs. A coplanar waveguide (CPW) fed coplanar strip (CPS) dipole antenna using the WTT technology is presented. Meanwhile, two antenna arrays using the LTCC technology are reported.

Design and measurement of substrate-integrated planar millimeter wave antenna arrays at 60–325 GHz

Antenna development at mmW bands has many unique challenges from design, fabrication to measurement. The designs usually suffer from high losses and difficulty in integrating into circuits. The fabrication is often associated with critical tolerance as one of the toughest issues because of expensive testing setup, critic requirements for reliable connection between antenna under test and feeding system, customized calibration setup and procedures. Using substrate-integration technology, the antennas will be fabricated onto substrate to reduce cost, size, transmission loss, and enhance integration into circuits. This talk will brief the design challenges in mmW antenna design and substrate-integration technology first. After that, recently developed substrate-integrated high-gain antenna arrays for 60-270 GHz applications are exemplified with the introduction of the latest built measurement system up to 325 GHz. Last, the comments on the development of the substrate-integration technology in antenna design at mmW and submmW bands are provided.