Isolators – WR-12 / 71 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 3 Advanced MMW ferrite components. Isolators – WR-12 / 60-90 GHz Isolators – WR-10 / 75-110 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 4 Advanced MMW ferrite components. Isolators – WR-10 / 75-110 GHz / (Drop-In Version) Isolators – WR-8 / 90-140 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 5 Advanced MMW ferrite components. Isolators – WR-6.5 / 110-170 GHz Isolators – WR-5.1 / 160-220 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 6 Advanced MMW ferrite components. Isolators – WR-4.3 / 170-260 GHz Isolators – WR-3.4 / 220-325 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 7 Advanced MMW ferrite components. Circulators – WR-15 / 58-64 GHz Circulators – WR-12 / 71-76 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 8 Advanced MMW ferrite components. Circulators – WR-12 / 81-86 GHz Circulators – WR-10 / 90-95 GHz 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 9 Advanced MMW ferrite components. MMW Flange Identifier Tool This tool is designed to identify waveguide flanges from WR-15 to WR-0.65. It comprises a microscope with adjustable zoom (20-40 X), adjustable focus, LED illumination and a reticle. The reticle has features to identify the waveguide flange. A pair of waveguide flange alignment pin holes are located at the bottom of the microscope. Slide the alignment pins on the flange you wish to identify into the holes at the base of the microscope. The reticle is slightly recessed so that it will come into close proximity but not touch the flange. Take care not to damage the reticle by piercing it with waveguide pins or other small pointed objects. When the microscope is held to a lighted background (no waveguide flange attached), all of the features on the reticle are visible as shown in the left side of the graphic. Before attaching to a waveguide flange, adjust the focus and magnification. When the microscope is attached to a waveguide flange, the area on the interior of the waveguide will go dark since there is no reflecting surface. For example, the graphic on the right shows the illuminated reticle with the microscope attached to a WR-8 waveguide flange. Although the markings for the 15, 12, 10 and 6.5 are still visible, only the “8” marker spans the exact length of the broad-wall of the waveguide thus identifying the flange as WR-8. Cleaning – The reticle is made from BoPET (Mylar). Do not clean with ammonia, vinegar-based cleaners or solvents. Do not use paper towels which can scratch the surface. We recommend blowing gently with compressed air to remove dust particles 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 10 Advanced MMW ferrite components. Drop-in Isolators Micro Harmonics has developed a Faraday rotation isolator that can be integrated with other components in a single waveguide block. The drop-in isolator comprises a centerplate that houses the core assembly (ferrite, cones, absorber, magnets, armatures) and an E-plane split waveguide block that houses the centerplate and provides stepped waveguide twists on both the input and output ports. An exploded view diagram of the centerplate assembly is shown below. The graphic below shows how the centerplate assembly fits into the E-plane split waveguide block. On the righthand side is a photograph showing a centerplate assembly sitting in the base half of the E-plane split waveguide block. The features of the machined twist step are visible in the photo. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 11 Advanced MMW ferrite components. The graph below shows measured data from one of our WR-10 drop-in isolator prototypes. In the standard WR‑10 band from 75-110 GHz, the insertion loss is less than 1.3 dB, the isolation is greater than 25 dB and the input and output return loss is less than 17 dB. The insertion loss is less than 1.5 dB over the extended band 66-115 GHz and isolation is greater than 25 dB over the band 64-117 GHz. The drop-in isolator offers some unique advantages. First, it can be integrated into a larger waveguide block. Second, the waveguides on the flanges are perfectly aligned in the drop-in isolator whereas in our standard isolators the waveguides are canted at 11.25 degrees from normal. Although this difference is mostly cosmetic, it may be important to some users. Third, the drop-in topology makes it possible to access two of the waveguide flange screws on each flange from the block interior which can eliminate the need for interconnecting waveguides. Our drop-in isolators are sold and shipped with the centerplate assembly housed in the outer waveguide block. This provides protection of the centerplate assembly and allows the drop-in isolator to be tested and used as a standalone component. If the customer wishes to integrate the isolator into their system, they can remove the outer housing, return it to micro Harmonics and receive a reimbursement. Micro Harmonics will provide customers with detailed drawings for the stepped twists and other features necessary to incorporate the isolator into their system. All of the required machine features including the stepped twist transitions are produced using standard end mil cuts. Currently, the drop-in isolator is only available in W band (75-110 GHz). However, we are developing an E-band version (60-90 GHz) and depending on demand may extend the technology to higher frequency bands. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 12 Advanced MMW ferrite components. Diamond Heatsink Technology Our isolators employ a modern design yielding much lower insertion loss than most commercial products. They also work over much broader bandwidths in excess of standard waveguide bands. But there is another important difference that sets them apart from the competition. Our isolators employ a diamond support disc that channels heat from the resistive layer in the cone to the metal waveguide block and thus they can handle greater reverse power levels. To our knowledge no other commercial isolators offer this advantage. At the heart of a Faraday rotation isolator is a pair of alumina cones and a cylindrical ferrite core. The cones are used to couple EM fields from the waveguides to the ferrite. The cones are bisected by a resistive layer along their central axis. In most commercial Faraday rotation isolators, the ferrite and cones are suspended by a pair of washer shaped supports as shown in the sketch below. The cone/ferrite assembly is inserted through the inner holes in the supports and then attached with a non-conductive epoxy. The support material is typically BoPET, polyimide, Styrene, a resin or some other material with a low dielectric constant and low loss at millimeter wave frequencies (see Table at the bottom of this article). Materials with these characteristics are generally in the class of thermal insulators and thus the cones and ferrite are thermally isolated from the metal block. Power entering the output port of the isolator is absorbed in the resistive layer bisecting the input alumina cone. The absorbed power is converted to heat energy. Very little of this heat energy can be channeled away by thermal conduction through the supports, rather it must be dissipated through a radiative process or by means of convection through the surrounding air. The resistive layers are thus subject to high heat levels and even damage if too much reverse power is incident on the device. Historically this was not an issue as there was very little power available at these frequencies. But as higher power sources are becoming available there is a renewed interest in the power ratings of these devices. At Micro Harmonics we have replaced the input support washer with a uniform high-grade optical CVD diamond disc. Diamond is the ultimate thermal conductor approaching 2200 W/mK, more than five times higher than copper. The graphic below shows the isolator split in 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 13 Advanced MMW ferrite components. half to give a better view of the constituent parts. The diamond disc is sandwiched between the base of the input cone and the ferrite. The diamond disc is in intimate contact over the entire area of the cone base. This is the optimal location for the diamond disc since it is the region subject to the highest heat levels. The diamond disc is epoxied to the metal waveguide block over its entire periphery and thus provides an excellent conduit to channel heat away from the resistive layer. The red arrows indicate the path of heat flow. Even at low reverse power levels, our isolators should consistently run cooler with reduced thermal stress on the epoxy joints. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 14 Advanced MMW ferrite components. Isolators Designed for Low-Insertion Loss Commercial Faraday rotation isolators have been around since the 1970’s. Traditional builds have good isolation throughout the microwave and millimeter-wave bands (typically > 20 dB and in many cases > 30 dB across the band). The insertion loss is low in the microwave bands, but steadily increases with frequency. At mm-wave frequencies the insertion loss becomes problematic. In the WR-10 band (75- 110 GHz) the insertion loss can be in excess of 3 dB, precluding their use in many systems. In the WR-3.4 band (220-325 GHz) the insertion loss can be more than 6 dB. There are very few manufacturers in the bands above 50 GHz. Isolators in the WR-4.3 and WR-3.4 bands were manufactured many years ago but are now difficult to find. At these high frequencies the constituent parts are very small, and difficult to fabricate and align. And with > 6 dB insertion loss, there isn’t much demand. At Micro Harmonics we design isolators that are optimized for low-insertion loss. The typical insertion loss is about 1 dB for our WR-10 isolators and about 2 dB for our WR-3.4 isolators. These numbers are game changers and mm-wave and terahertz system developers are now reconsidering their use. So how do we do it? There are many factors to consider, but here we focus primarily on; 1) Minimizing Ferrite Loss 2) Minimizing Waveguide Loss 3) Precision Fabrication and Alignment 1) Minimizing Ferrite Loss – A good starting point is to consider the equation for EM field rotation in a Faraday rotation isolator.  4ϒ√ 2 Where, 4πMz is the axial magnetization ϒ is the gyromagnetic ratio (8.795×106 xg rad/s/Oe)  is the ferrite length c is the speed of light is the ferrite dielectric constant This equation shows that the field rotation is directly proportional to the ferrite length and the axial magnetization. Minimum insertion loss and maximum isolation occur when the EM field is rotated by 45° as it passes through the ferrite. Ferrites are lossy at millimeter-wave frequencies, so it is essential that the length be reduced as much as possible. The traditional method used to tune Faraday rotation isolators is to use ferrites that are substantially longer than the minimum required length and then tune the magnetic bias field to achieve optimal performance. At Micro Harmonics we use a saturating magnetic bias field and the minimum possible ferrite length to achieve 45° rotation. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 15 Advanced MMW ferrite components. We measure our magnetic bias fields to insure the ferrites are saturated. We use magnetic armatures to achieve a focused, uniform bias field in the ferrite. The graph below shows the measured magnetic bias field near the surface of the ferrite core. The peak measured value of 2000 Oe is substantially more than what is required. The measurements extend well outside of the area of the ferrite. 2) Minimizing Waveguide Loss – Since the EM field is rotated by 45° as it passes through the ferrite, it is necessary to realign the flanges. In the traditional builds this is accomplished by physically twisting extruded waveguide (see photo). The twist must be implemented over a sufficiently long distance to avoid damaging the extruded guide. The extruded sections also permit interior access to the waveguide flange screws. In the WR-10 through WR-3.4 bands the total length of extruded waveguide is about 2.3 inches in traditional builds, with some small variations from band-to-band and between manufacturers. At Micro Harmonics we use machined twist steps which are substantially shorter than the extruded waveguide twists. They yield good broadband performance and reduced waveguide loss. The total flange-to-flange length of a traditional WR-3.4 isolator is about 2.4 inches (assuming you can find one) whereas the total flange-to-flange length of a Micro Harmonics WR-3.4 isolator is 0.45 inch as shown in the drawing below. When calculating waveguide loss we will use an average waveguide length of 0.5 inches for all of the Micro Harmonics isolators. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 16 Advanced MMW ferrite components. The calculations are performed in the low end of each band where the conductor losses are highest. The results are shown in the Table below. The last column in the Table shows the loss reduction of the twist step (0.5 inch) as compared to the extruded twist (2.3 inch). At WR-10 there is only a 0.2 dB difference, but at WR-3.4 there is a substantial 0.9 dB improvement using the step twist. To our knowledge no one has ever manufactured a WR-2.8 Faraday rotation isolator (265-400 GHz), but it is included here since we are actively pursuing development in this band. Flange (EIA) F (GHz) Loss (dB/inch) Total Loss (2.3 in) (dB) Total Loss (0.5 in) (dB) Difference (dB) WR-10 75 0.10 0.24 0.05 0.19 WR-8 90 0.16 0.36 0.08 0.28 WR-6.5 110 0.22 0.50 0.11 0.39 WR-5.1 140 0.31 0.72 0.16 0.56 WR-4.3 170 0.38 0.88 0.19 0.69 WR-3.4 220 0.52 1.20 0.26 0.94 WR-2.8 260 0.74 1.70 0.37 1.33 3) Precision Fabrication and Alignment – There are substantial challenges in fabricating and assembling the isolators at the higher bands. The parts become increasingly smaller and some of the materials, in particular the ferrite and alumina cones, are very difficult to machine. There are very few vendors who will even attempt to fabricate these parts and even the most skilled craftsmen can fail in the end. We have expended a significant amount of time and money developing techniques to fabricate these parts. Unfortunately, we cannot elaborate more on this subject. Aside from the myriad fabrication complications there are considerable alignment difficulties that must be overcome. Even a small misalignment of the cones and ferrite by a few degrees can result in significant degradation of the isolator performance. The core area around the ferrite can support more than thirty modes. Misalignment can cause significant coupling to the higher order modes resulting in unwanted structure in the response, increased insertion loss and port reflections as well as decreased isolation. Misalignments can also change the orientation of the resistive layers in the cones such that a component of the E-field of the forward travelling wave is in the plane of the resistive layer. The result is increased insertion loss and decreased isolation. The assembly process is an art form. No two isolators have exactly the same performance. At Micro Harmonics we continually strive to improve our assembly techniques and the uniformity of assemblies. We also comprehensively RF test every isolator on a vector network analyzer to insure it meets our specifications. Many competitors spot check their components on less sophisticated systems which can lead to erroneous test data and missed signatures in the response. We also perform thermal stress testing to verify the mechanical reliability of our devices. 20 S Roanoke St, Ste 202 Phone: 540.473.9983 Fincastle, VA 24090 17 Advanced MMW ferrite components. Warranty New Product Warranty All Micro Harmonics (Seller) products are warranted to the original Buyer (Customer) for a period of one year from the date of shipment to be free from defects in material and workmanship and to meet the specifications agreed upon at the time order is accepted or any written modifications thereof. Seller’s entire warranty obligation is limited to making adjustments by repairing, replacing, or refunding the purchase price of any product which fails to meet this warranty and which is returned to Seller, as provided below, within one year from date of first shipment by Seller. Replacement, repairs, or adjustments under this warranty shall not reinstate the warranty. The warranty will expire not later than one year after such first shipment. The warranty does not cover products subjected to abuse, improper application or installation, alteration, accidental or negligent damage in use, storage, transportation or handling. The warranty is void if the Seller determines that the product identification labels have been removed or altered. Seller shall have the right of final determination as to the existence and cause of a defect, and whether to make adjustment by repair, replacement or refund. When adjustment is not allowed, a reasonable charge will be made to Buyer to cover Seller’s cost of inspection and handling. If the Seller determines that any product claimed to be defective is not subject to adjustment, Buyer will be notified that product is not subject to adjustment. Unless the Buyer furnishes disposition instructions for the product within thirty (30) days after such notification, Seller may return the product “as is” to Buyer, transportation collect. In returning products under this warranty, Buyer in all cases will obtain and comply with Seller’s packaging and shipping instructions. Buyer will pay for all packing and transportation costs for returned products. Credit for transportation charges within the United States will be issued by Seller if adjustment is allowed. Where adjustment is not allowed, products will be returned to Buyer, transportation collect. No warranties extend beyond the description on the face of the contract. Seller is not liable for consequential damages. No change in this warranty shall be binding upon Seller, unless it shall be in writing signed by a duly authorized representative of the Seller. Repair Warranty Micro Harmonics will provide repair for all products it sells. Products no longer under Micro Harmonics new product warranty which are repaired, modified, tuned, or calibrated at the Buyer’s expense will be covered by the repair warranty. The repair warranty applies only to products returned for repair at Seller’s facility. The warranty does not apply to any products returned to the Seller with obvious physical damage, or which have been modified by the Buyer in any relevant way or where there is evidence that the product identification label has been removed. Under all circumstances, the repair warranty will expire not later than one hundred twenty (120) days after shipment.