Nuvotronics-PolyStrata

What is the PolyStrata™ technology?
It is a wafer-level process for producing 3-dimensional micro-structures in metal and dielectric. It can make many useful components. Most work to date has been in the area of microwave components based on micro-coaxial and cavity structures.

What can it make?

Coax:
The PolyStrata process can produce tiny, high-density coaxial circuits for microwave and millimeter wave applications…think printed circuit boards of coax . See Figure 1 for a cross section view of a coax line made using the PolyStrata process, where each line is usually about 500 microns or less in cross section. Our coax has a center conductor that is fully isolated, with air as a dielectric. With our coax structures we can fabricate feed networks, various passive components (baluns, filters, splitters, combiners), and combined hybrid components with all the benefits of the PolyStrata structure. The coax has many unique properties such as size, precision, multiple layers, and having air as the dielectric.

Figure 1. PolyStrata Coaxial Lines

Metal MEMS:
Micro-Electro-Mechanical Systems or MEMS are microstructures, usually fabricated in silicon, that make transducers, sensors, or actuators widely used today in consumer and automotive electronics. The PolyStrata process can create microstructures in polymer and metal, where the thermal or mechanical properties of the metallic material can be an advantage compared to traditional MEMS. Metal MEMS structures, like antennas, can be monolithically fabricated in the same process as our coax circuits to provide microwave system solutions.

What are its advantages?
In microwave and millimeter-wave systems, networks of coax lines deliver high-speed signals to various passive and active components. Since there has not been a printed circuit board solution to this problem in the past, companies have invented ways to provide microwave circuits in LTCC and other materials but at a drastic cost to performance . No other company offers a pure coax solution with air dielectric, meaning that the PolyStrata technology has the lowest loss and highest Q of any microwave circuit material above 20GHz. The coax medium provides a confined, single TEM non-dispersive mode from HF to 100GHz that can be routed three dimensionally with excellent phase control.

Advantages in a nutshell:

1. Air dielectric decreases the loss and dispersion per unit distance
2. 20x smaller (than traditional coax) reduces unneeded weight and size
3. 85x smaller separation (than microstrip lines) for comparable line-to-line isolation (see Figure 2), allows for much higher circuit density for high-isolation applications compared to traditional microwave networks
4. 1000x higher isolation than microstrip lines at standard dimensions and spacing
5. Lithographically defined production ensures tight tolerances, excellent phase and amplitude control, and high-accuracy placement of bond pads—no tweaking, no tuning!
6. Low temperature process allows it to be made on various substrates (including wafers with devices already on them)
7. Multiple layers provides 3D circuits with isolated cross-overs and the ability to create embedded micro-mechanical features

Figure 2. PolyStrata coax provides for an 85X smaller separation or pitch between coax lines due to very high isolation.

Example programs and applications

Our first application for the PolyStrata technology was developed under the 3D-MERFS DARPA-funded research program designed to improve and reduce the cost of phased array data links. Key technology characteristics include low loss, high component density, and high isolation. Increased isolation enables realization of small-volume systems with improved sensitivity and decreased co-site interference. Low insertion loss enables higher performance systems with lower input power requirements. This new microfabrication process is a key enabler for next generation Millimeter Wave (MMW) radar and communications systems. This technology promises to enable a MMW “antenna on a wafer”, improving system performance while decreasing size and weight.

Power combiners for hybrid amplifiers are another active area of development. Under the DARPA DMT (Disruptive Manufacturing Technologies) program, the goal is to create a SSPA (Solid-State Power Amplifier) of 160 Watts over a wide-band width (4-20GHz). For this program GaN power devices are placed in a high performance PolyStrata backplane with all key passive components additionally created via the PolyStrata technology. Currently the program is demonstrating a 20W module in the Phase I. Some of the passives are: high efficiency broadband power combiners and low loss broadband 1:2 and 1:4 impedance transformers. The second phase will push the power levels from 20 Watts to 160 Watts CW over the same bandwidth.

Other applications for the technology in defense and commercial applications include monopulse radar circuits, cross-over networks, delay lines, filters, switch matrix networks, baluns, and any other passive components or their combinations in circuits. In addition, there are far-reaching applications in defense: munitions fuzes, safe and arm devices, terahertz imaging and screening—to name a few—as well as medical devices and advanced packaging applications.

How we work

We design, develop, and fabricate custom networks of circuits and passive components for complex microwave systems. We collaborate with our customers to ensure that the design of the integrated system will meet the end goals--using HFSS®, ANSYS®, SolidWorks®, and other tools during the design process. Our library components (see Figure 3 for a snapshot) of typical passives can give our customers an indication of what is possible with the PolyStrata technology. In addition, we have created design rules for microwave system engineers to aid in the design process (these design rules are being added to an Ansoft library to be released in 2009).

Figure 3. Representative PolyStrata passive components

Once the design stage is complete, we move to fabrication of prototypes and testing. Prototype fabrication is typically handled through our Multi-User Runs. The MUR is an excellent way to divide the cost of prototype fabrication between multiple customers. Each customer gets a portion of the mask set for the wafer fabrication, and each only pays a portion of the total fabrication cost. We typically run a MUR per quarter.

After successful prototyping and testing iterations prove that the system designs are ready for production, the PolyStrata development moves to a production phase, usually priced by the device. Since ours is a batch wafer-level process, we implement a manufacturing plan that involves only a small toolset: one that is replicatable, controllable, and does not rely on traditional manual machining, tweaking, or assembly.

In conclusion

Nuvotronics' PolyStrata technology provides a revolutionary way to think about passive microwave devices and architectures. Where active microwave device designers have had the MMIC, now they can turn to PolyStrata for the passive circuit solution .

Microwave system design and implementation can now become more like that of the semiconductor industry in design, process, and implementation. This leap forward in technology can provide thousands of new applications available through higher frequencies. Let's make your application happen. Contact Nuvotronics or our dedicated sales representatives to learn more!