Sungwook Moon

High-

In this paper, the authors present a design technique that enables inter-resonator and external coupling control for high-quality-factor (Q) tunable bandpass filters. The design incorporates low-Q varactors as part of the inter-resonator and external coupling mechanisms without degrading the overall high Q of the original filter. Detailed design methodology and equations are presented to illustrate the concepts. A first-time demonstration of these concepts is presented for a widely tunable high-Q evanescent-mode cavity bandpass filter. The cavities are integrated in a low-loss substrate with commercially available piezoelectric actuators and solid-state varactors for frequency and bandwidth tuning. This technique allows for reduced bandwidth variation over large tuning ranges. As one example, a constant 25-MHz absolute-bandwidth filter in the 0.8-1.43-GHz tuning range with loss that is as low as 1.6 dB is presented as an example. The filter third-order intercept point is between 32.8 and 35.9 dBm over this tuning range. To further show the impact of the technique on high- Q filters, a filter Q that is as high as 750 is demonstrated in the range of 3-5.6 GHz, while using low-Q varactors (Q < 30 at 5 GHz for a 0.4-pF capacitance) to achieve more than 50% reduction in bandwidth variation over the tuning range.

Q

We report live animal studies that verify and quantify successful transocular transmission of data from a miniature low-power implant. To minimize damage, implantation within layers of the eye requires an ultrasmall device on a scale of just a few millimeters on each side and less than 500 mum in thickness. A high-frequency transmitter integrated circuit (IC) was designed, fabricated, and bonded onto a board containing an antenna, matching network components, and interconnects. The transmitter must achieve sufficient efficiency to draw minimal power from the limited onboard storage array while outputting a sufficiently large signal to overcome tissue-induced attenuation. Two different versions of the system were developed, one using a low-temperature co-fired ceramic material for the substrate and the other using silicon. Animal studies performed using live rabbits followed by empirical measurements verified the feasibility of a wireless telemetry scheme for a low-power miniature ocular implant.

Fully Reconfigurable Tunable Bandpass Filters

In this letter, the design and RF packaging of substrate integrated widely tunable filter is presented. The filter consists of two heavily loaded evanescent-mode cavities embedded into the substrate. The filter is actuated using two piezoelectric discs, which move thin, flexible membranes that form the top of the cavities. To demonstrate the wide tuning a filter is fabricated and measured to cover a very wide frequency range from 0.98 to 3.48 GHz (tuning ratio-3.55:1). The measured insertion loss is less than 3.57 dB for a 1.1% fractional bandwidth filter.

Implantable Wireless Telemetry Boards for In Vivo Transocular Transmission

A switchless bank of three tunable bandpass filters is demonstrated which can be used as a triplexer over a large tuning range. Three high Q narrow-band evanescent-mode cavity filters are integrated in a single substrate using an input feed-line network to achieve multi-band operation. Using shorted feed-lines for magnetic field coupling allows the out of band impedance to be dominated by the reactance of the feed-lines. The feed-lines are then designed to have high out of band impedance over the tuning range. A three-way switchless filter bank is presented in the 1.7 GHz–3.4 GHz range maintaining less than 4 dB loss for 14 MHz-31 MHz 3-dB bandwidth over most of the tuning range. The filter bank is fabricated in one low-loss Rogers TMM3 substrate using standard PCB processing, and commercially available 0.5mm thick piezoelectric actuators are used for the electrical tuning.

Substrate Integrated Evanescent-Mode Cavity Filter With a 3.5 to 1 Tuning Ratio

Upon the application of a magnetic field, ferromagnetic particles will self-align along the field lines of the applied field. Rods are thus formed that can grow until they are stopped by a substrate after application of a material and at the angle of the applied field. The dynamic growth of the columns is beneficial for implementing packages with complicated three-dimensional system integration. The growth of the rods, internal to the material, has the ability to adapt to the gap between pads or even an angle between the substrates. In this work, we demonstrate these advantages by showing multilayer interconnects as well as angled connections for three-dimensional vertical chip stacking concepts. Four layers of silicon on top of each other were integrated with multilayer interconnects and the RF performance is demonstrated. In addition, we implemented a novel three-dimensional packaging structure for a horizontal-to-vertical plane transition, with the performance evaluated for a variety of angles. Consequently, the Z-axis anisotropic conductive adhesive is shown to be a suitable solution to implement advanced three-dimensional integrated microwave applications.

Tunable high Q narrow-band triplexer

In the present work, the authors present a design technique to create widely-tunable high Q narrow-band filters with bandwidth control by utilizing low Q varactors, while maintaining the high Q of the original filter. Detailed design methodology and equations are presented to illustrate the concept and a widely tunable high Q evanescent-mode cavity bandpass filter with controllable bandwidth is demonstrated as an example of this design technique. The filter is designed and fabricated in low-loss Rogers TMM3 substrate. A thin copper membrane is laminated on top of the substrate to allow frequency tuning, achieved using commercially available 0.38 mm thick piezoelectric actuators. The feed-lines with the impedance matching and the varactor based bandwidth control section are incorporated in parallel with the coupling iris on the back-side of the filter. A constant absolute bandwidth filter is also presented, which is tuned from 0.89 GHz to 1.47 GHz with constant 25 MHz (± 0.2 MHz) 3-dB bandwidth and less than 3 dB insertion loss over the entire tuning range. The extracted filter Q is in the range of 250–350, even though low Q varactors (Q ≪ 30@1 GHz) with capacitance in the 0.5 pF to 4 pF range are utilized for the bandwidth control.

Magnetically Aligned Anisotropic Conductive Adhesive for Microwave Applications

In the present work, a method for tracking the center frequency of a widely tunable evanescent-mode cavity filter in-situ is introduced. The goal is to be able to monitor the performance of a filter without disturbing the fields or degrading the quality. The proposed method is to monitor the resonant frequency of each resonator of the filter independently by inducing higher order differential modes. This method enables a continuous feedback loop to lock in the filter center frequency and shape. An example filter is fabricated to demonstrate the concept and tuned from 1.4 to 3 GHz while monitoring the differential mode at 4 to 6.5 GHz. The ability to independently monitor and control the individual resonators in-situ without disturbing the main mode is demonstrated and is a crucial step towards a robust fielded widely tunable filter.

High Q narrow-band tunable filters with controllable bandwidth

High quality factor W band MEMS-tunable evanescent-mode bandstop resonators are presented for the first time. The precision, tolerances, and small feature capability of silicon microfabrication techniques enable these resonators to be the highest frequency tunable evanescent-mode cavities shown to date. Their MEMS tuning technology requires very low power to operate, and the entire resonator-tuner structure is made of silicon to enable compatibility with integrated circuit manufacturing processes. A measured tuning range of 75.8 GHz to 82.3 GHz with quality factors of 414 to 448 were observed with a tuning voltage of 70 Volts. Such resonators will be important for tunable W band filters as lower frequencies become saturated and W band applications become more common.

In-situ control of tunable evanescent-mode cavity filters using differential mode monitoring

Characteristics of z-axis interconnects using magnetically aligned anisotropic conductive adhesives (ACAs) are analyzed for their applicability for small pad sizes. In order to evaluate the performance of ACAs, a statistical estimation of the failure rate of interconnects was carried out using top-view images of assembled samples. Through a column mapping process, the failure rate is calculated as a function of pad size. The calculated and measured results indicate that the location of the formed columns is the predominant effect determining interconnect failure. The developed failure estimation approach is effective in demonstrating the effects of scaling to smaller particles in ACAs.

High-Q MEMS-tunable W-band bandstop resonators

In this work, we propose a novel packaging concept for highly-integrated RF systems using a magnetically aligned Z-axis anisotropic conductive adhesive. We demonstrate the ability to “grow” interconnects allowing for multilayer packages that are not sensitive to the height between pads. Using this effect we introduce two approaches to integrating multiple silicon wafers on top of each other, creating the possibility for an exceptionally dense integrated system-in-a-package. First, a reverse-pyramid package with all chips stacked facing down on a silicon substrate is demonstrated. Second, a “Matryoshka” package assembled with the alternation of chips face direction is also demonstrated. The simplified assembly process of the Z-axis ACA and the new packaging concepts can offer a compact and cost-effective solution to system-in-package based RF systems.