Nickolas Kingsley

Fractal-shaped microstrip coupled-line bandpass filters for suppression of second harmonic

In this paper, microstrip coupled-line bandpass filters using a Koch fractal shape are proposed for the first time. These filters are fabricated on a liquid crystal polymer (LCP) substrate for Ku-band. Conventional microstrip coupled-line filters are very popular for RF front ends because they can be fabricated easily. However, their large second harmonic causes the shape of the passband to be asymmetric in the upper band and it worsens the skirt properties. By proper design, the second harmonic of fractal filters can be significantly suppressed through the use of fractal shapes. In this paper, using LCP, the maximum harmonic suppression was almost 42 dB. This type of filter can be used to suppress the second harmonic without any additional devices and regardless of the substrate.

RF MEMS Sequentially Reconfigurable Sierpinski Antenna on a Flexible Organic Substrate With Novel DC-Biasing Technique

Devices and systems that use RF microelectromechanical systems (RF MEMS) switching elements typically use one switch topology. The switch is designed to meet all of the performance criteria. However, this can be limiting for highly dynamic applications that require a great deal of reconfigurability. In this paper, three sets of RF MEMS switches with different actuation voltages are used to sequentially activate and deactivate parts of a multiband Sierpinski fractal antenna. The implementation of such a concept allows for direct actuation of the electrostatic MEMS switches through the RF signal feed, therefore eliminating the need for individual switch dc bias lines. This reconfigurable antenna was fabricated on liquid crystal polymer substrate and operates at several different frequencies between 2.4 and 18 GHz while maintaining its radiation characteristics. It is the first integrated RF MEMS reconfigurable antenna on a flexible organic polymer substrate for multiband antenna applications. Simulation and measurement results are presented in this paper to validate the proposed concept.[2007-0013]

Reconfigurable RF MEMS Phased Array Antenna Integrated Within a Liquid Crystal Polymer (LCP) System-on-Package

For the first time, a fully integrated phased array antenna with radio frequency microelectromechanical systems (RF MEMS) switches on a flexible, organic substrate is demonstrated above 10 GHz. A low noise amplifier (LNA), MEMS phase shifter, and 2 times 2 patch antenna array are integrated into a system-on-package (SOP) on a liquid crystal polymer substrate. Two antenna arrays are compared; one implemented using a single-layer SOP and the second with a multilayer SOP. Both implementations are low-loss and capable of 12deg of beam steering. The design frequency is 14 GHz and the measured return loss is greater than 12 dB for both implementations. The use of an LNA allows for a much higher radiated power level. These antennas can be customized to meet almost any size, frequency, and performance needed. This research furthers the state-of-the-art for organic SOP devices.

Organic "Wafer-Scale" packaged miniature 4-bit RF MEMS phase shifter

This paper presents for the first time a 4-bit microelectromechanical systems (MEMS) phase shifter fabricated on, integrated, and packaged into an organic flexible low-permittivity material. A microstrip switched-line phase shifter has been optimized at 14 GHz for small size and excellent performance. In addition, the MEMS phase shifter was packaged in an all-organic flexible low-permittivity liquid-crystal polymer (LCP) package. The improved geometry of the reduced size phase shifter is 2.8 times smaller than a traditional switched-line phase shifter and is much less lossy. For the 4-bit phase shifter, the worst case return loss is greater than 19.7 dB and the average insertion loss is less than 0.96 dB (0.24 dB/bit or 280/spl deg//dB). The average phase error is only 3.96/spl deg/. It has been demonstrated that the addition of the LCP package has a negligible effect on the phase-shifter performance, but will enable the device to remain flexible and protected against various environmental conditions.

RF characteristics of thin film liquid crystal polymer (LCP) packages for RF MEMS and MMIC integration

A standard non-metallized liquid crystal polymer (LCP) 4 mil thick microwave substrate with depth-controlled laser-micromachined cavities was investigated as a system-level packaging layer for integrated packaging of monolithic microwave integrated circuits (MMICs) and radio frequency microelectromechanical systems (RF MEMS) switches. The RF characteristics of air/dielectric discontinuities at the cavity interfaces were first simulated and the results show that LCPs low dielectric constant enables cavity dimensions to be arbitrarily chosen without significantly affecting the RF performance. To test this packaging concept a 4 mil LCP sheet with twelve 1 mm /spl times/ 2.4 mm /spl times/ 2 mil deep cavities was fabricated. Air-bridge type RF MEMS switches were fabricated on a base LCP substrate and measured before and after introducing the laser-micromachined superstrate layer. The measurements show almost no difference in packaged and unpackaged form for frequencies up to 40 GHz. The concept of a system-level package on a flexible, low-cost, organic substrate has been demonstrated for the first time. The same technique could be used for integrating MMICs all in a near-hermetic low-cost LCP module.

Moisture Lifetime Testing of RF MEMS Switches Packaged in Liquid Crystal Polymer

This paper presents for the first time the effects of moisture on radio frequency microelectromechanical systems (MEMS) switches packaged entirely inside a flexible, organic polymer [namely, liquid crystal polymer (LCP)]. Moisture tests were administered at 100degC and 100% relative humidity to evaluate long-term exposures and at 85degC and 85% relative humidity to evaluate short-term exposures. The effect of the moisture was quantified by before and after S-parameter measurements, by a weight gain analysis, and by visual inspection. Both global and localized bonding techniques were investigated to compare the best-case scenario to a more practical case. The effects of an 18 mum thick copper layer on both sides of the package were studied as well as the size of the bonding contact area. It was found that many packages that passed the Military Standard 883 G, Method 1014.12 for seal quality were unable to provide adequate protection from moisture. This indicates that the requirements for MEMS devices is more rigorous than the Military Standard. This standard is commonly quoted in literature as a metric for qualifying polymer packaging techniques. This paper demonstrates the necessity for proper testing of MEMS devices in a moist environment. It has been determined that for the bonding methods presented in this paper, an LCP packaged MEMS switch could potentially survive 7-10 h in jungle conditions, 5-7 weeks in ambient conditions, or 1.4-1.8 years in desert conditions.

14 GHz MEMS 4-bit phase shifter on silicon

In this abstract we describe the work in progress on a 4-bit coplanar waveguide (CPW) MEMS phase shifter simulated, fabricated, and measured at 14 GHz on 400 /spl mu/m high-resistivity silicon (/spl epsiv//sub r/=11.7). Simulated results using a full wave simulator predict a return loss better than 19 dB and isolation better than -0.1 dB for a one bit phase shifter using perfectly conducting lines. Measurement results for single MEMS switches have shown -22 dB return loss and -0.095 dB isolation in the UP (not activated) state and -0.83 dB return loss and -14.5 dB isolation in the DOWN (activated) state. It has also been shown that the single bit phase shifters exhibit accurate phase shifts, but higher than expected loss.

14 GHz microstrip MEMS phase shifters on flexible, organic substrate

One and two bit microelectromechanical system (MEMS) microstrip phase shifters at 14 GHz have been realized on 100 /spl mu/m liquid crystal polymer (LCP) substrate. This paper presents for the first time a MEMS phase shifter on a flexible, organic substrate. LCP is a well-suited substrate for low-cost, low-loss, and near-hermetic applications. Multibit phase shifters have applications in almost all microwave devices, but are most commonly used in phased antenna arrays, which can be realized on a rollable substrate using this technology. The one-bit phase shifters have an average return loss of 19.0 dB and an average insertion loss of 0.59 dB at 14 GHz. The phase shifts are within 1.38/spl deg/ of the intended phase shift at this frequency. For the two-bit phase shifters, an average return loss of 22.5 dB and an average insertion loss of 0.98 dB were measured per bit. The average phase error for the two-bit phase shifter is only 1.26/spl deg/.

Fractal-shape 40 GHz microstrip bandpass filter on high-resistivity Si for suppression of the 2nd harmonic

In this paper, the Koch fractal shape is applied for the first time to microstrip bandpass filters integrated on a high-resistivity Si substrate. By using this method, the second harmonics of the filter can be suppressed to about -40 dB. Conventional microstrip coupled line filters are popular in RF front ends, because they can be easily fabricated and integrated with other RF components. However, they typically have large second harmonics that can cause unwanted interference. Without any additional filters, the proposed Koch shape filters have suppressed the 2nd harmonics by about -40 dB, so they can be used in systems with stringent harmonic suppression requirements.

Low Cost Method for Localized Packaging of Temperature Sensitive Capacitive RF MEMS Switches in Liquid Crystal Polymer

This work demonstrates a low cost localized heating packaging method on liquid crystal polymer (LCP) for temperature sensitive devices such as the capacitive RF MEMS switch. Simulations of the heating element structures are performed to examine the thermal characteristics of the bonded regions and switch. Heating lines are fabricated on LCP using the copper cladding, requiring only one photolithography and etch step. The MEMS cavity is formed with two 1 mil layers of low-temp LCP that are etched with a CO2 laser system. The layers are bonded with localized-heating by passing 7 A of DC current through the heating element while compressing the 4 layers together. The bonded switch is submerged in 60degC water for 24 hours to test seal quality. Before and after measurements are shown, providing evidence of a successful bond.