Deepukumar Nair

Miniature 3D micro-machined solid state power amplifiers

In this work, a rectangular coaxial transmission line based power amplifier is discussed. This transmission line is created by sequential photolithography and plating processes, resulting in a very wide band, dispersion-less transmission medium which includes integrated passive components. This approach yields a number of advantages over conventional microstrip circuits. This 3D micro-machining technology, called PolystrataTM technology, in which the circuit is the package, and the package is the circuit, enables one other important and far reaching advantage.

A 10 MHz to 100 GHz LTCC CPW-to-stripline vertical transition

A broadband 50Ω coplanar waveguide (CPW)-to-stripline transition is presented which is capable of operation up to 100 GHz. This vertical transition is fabricated in low-temperature co-fired ceramic (LTCC), and it is appropriate for system in package (SiP) module packaging. It was designed for wafer probing an LTCC module containing an embedded stripline. This compact transition occupies only two layers of nominal 5 mil thick tape. Both simulated and measured s parameter results are shown for back-to-back transitions up to 110 GHz. Measured insertion loss for a single transition is less than 0.3 dB near 60 GHz and less than 1 dB up to 100 GHz.

Micro-coaxial lines for active hybrid-monolithic circuits

This paper discusses fundamental properties of rectangular micro-coaxial lines fabricated in the PolyStrata™ process for broadband applications from 2–20 GHz. The possible impedance ranges for coaxial lines implemented with both five and eleven Cu layers are discussed and compared with measured results for the lowest impedance (8Ω) line. Power handling and thermal properties of these miniature lines are analyzed and measured. A 50Ω line with outer conductor cross-section of 600µm by 400µm is experimentally shown to handle 53W at 2:5GHz with a 10% duty cycle. Integration with active components is investigated and a 1–10GHz measurement of a GaN 50 MMIC amplifier shows minimal performance degradation relative to on-wafer measurements.

60 GHz patch antenna in LTCC with an integrated EBG structure for antenna pattern improvements

We present a 60 GHz LTCC aperture-coupled patch antenna with an integrated Sievenpiper EBG structure used for suppression of TM mode surface waves. This is believed to be the first demonstration of a Sievenpiper EBG structure used inside a millimeterwave LTCC antenna. The merit of this EBG structure is to yield a predicted 6 dB improvement in broadside directivity. Without the EBG structure, edge diffraction of surface waves degrades the pattern into two main beams. The combination of a new LTCC material system (DuPont 9K7 GreenTape™) along with laser ablation processing for fine line and fine slot definition allowed the integration of a successful EBG structure with an aperture coupled patch antenna.

60-GHz

This letter presents a 60-GHz 2 × 2 low temperature co-fired ceramic (LTCC) aperture-coupled patch antenna array with an integrated Sievenpiper electromagnetic band-gap (EBG) structure used to suppress TM-mode surface waves. The merit of this EBG structure is to yield a predicted 4-dB enhancement in broadside directivity and gain, and an 8-dB improvement in sidelobe level. The novelty of this antenna lies in the combination of a relatively new LTCC material system (DuPont Greentape 9K7) along with laser ablation processing for fine line and fine slot definition (50-μm gaps with +/ - 6 μm tolerance) allowing the first successful integration of a Sievenpiper EBG structure with a millimeter-wave LTCC patch array. A measured broadside gain/directivity of 11.5/14 dBi at 60 GHz is achieved with an aperture footprint of only 350 × 410 mil2 (1.78λ × 2.08λ) including the EBG structure. This thin (27 mil) LTCC array is well suited for chip-scale package applications.

2 \times 2

This paper presents characterization of low temperature co-fired ceramic (LTCC) based electromagnetic bandgap (EBG) structures, and a test method to measure the TM mode cutoff frequency at millimeter wave frequencies. This test method differs from prior art in that the TM mode surface wave launchers are fabricated in the same LTCC module as the EBG structure under test to realize a compact and repeatable test vehicle. A pair of two port transmission measurements will experimentally yield the TM mode cutoff frequency. This frequency defines the lower bound for the surface wave bandgap. The TM mode cutoff frequency is a very important parameter where EBG structures are integrated into millimeterwave LTCC antennas because this cutoff frequency must be lower than the antennas operational frequency range. This proposed test method may be used with any open EBG structure which exhibits a TM mode cutoff frequency.

LTCC Patch Antenna Array With an Integrated EBG Structure for Gain Enhancement

This paper presents characterization of low temperature co-fired ceramic (LTCC) based electromagnetic bandgap (EBG) structures. We show a new test method to measure the TE mode cutoff frequency of an EBG structure. This test method is implemented at millimeter wave frequencies. Exponentially-shaped TE mode surface wave launchers are fabricated in the same LTCC substrate as the EBG structure under test to realize a compact and repeatable test vehicle. A pair of two port coupling measurements experimentally yields the TE mode cutoff frequency, below which a bound TE mode surface wave is suppressed. The TE mode cutoff frequency is important where EBG structures are integrated into millimeterwave LTCC antennas because this cutoff frequency must be greater than the antennas operational frequency range. This proposed test method differs from previous experimental techniques because it employs a calibration test vehicle, and this test method provides a clear indication of the TE mode cutoff frequency.

Millimeter wave measurement of the TM mode cutoff for EBG structures fabricated in LTCC for antenna applications

Presented here are the design, fabrication, and measurement results of a low temperature cofired ceramic (LTCC) chip-to-interposer transition utilizing a flip-chip ball grid array (BGA) interconnect that provides excellent electrical performance up to and including 80 GHz. A test board fabricated in LTCC is used as the interposer substrate and another smaller LTCC part is used as a surrogate chip for demonstration purposes. The BGA chip-to-interposer transition is designed as a back-to-back pair of transitions with an assembly consisting of an LTCC interposer, an LTCC test chip, and a BGA interconnect constructed with 260 μm diameter polymer core solder balls. The LTCC material employed is DuPont™ GreenTape™ 9K7. Full-wave simulation results predict excellent electrical performance from 10 MHz to 80 GHz, with the chip-to-interposer BGA transition having less than 0.5 dB insertion loss at 60 GHz and less than 1 dB insertion loss up to 80 GHz. In an assembled package (back-to-back BGA transitions), the inse...

Measurement method for the TE mode cutoff frequency in EBG structures fabricated in LTCC for antenna applications

Low Temperature Co-fired Ceramic (LTCC) technology provides an attractive packaging platform for microwave and millimeter wave circuits and systems due to its unique properties. Generally, thick film gold or silver conductors are used as metallizations on LTCC substrates along with occasional use of copper thick films. This paper reports methods and results of extensive process development experiments DuPont Microcircuit Materials has undertaken to establish a commercially viable plating process for the market leading DuPont™ GreenTape™ 9K7 LTCC system. Both Electroplating and Electroless plating processes are investigated in this work. These techniques provide certain advantages when used in isolation or in combination with standard thick film metallizations, helping to extend their applicability. Electroplating of copper on LTCC provides a means of using copper as the external conductor without having to use complicated firing processes in oxygen-free atmosphere as required for copper thick film. This a...