Microwave Journal

The Magic Behind "Black Hole" Filters

November 12, 2010

MWJ: KMW is a leading provider of RF and air interface products from Korea. Could you give us some background into the origins of the company, what its initial focus was and in what areas of technology the company has grown substantially?

DW: KMW Inc. was founded in 1991 by Duk Yong Kim, PhD, now serving as Chairman of the Board and continues to be the leading contributor to KMW’s advanced technology developments. In 2000, KMW Inc. was registered as a public company in KOSDAC - KOSDAQ (Korea Stock Exchange Market).

KMW’s original focus was on passive microwave components such as filters and switches. Since then KMW has become a world leader in advanced RF filters for wireless base stations. Also, we have substantially expanded our product portfolio to include antennas, TMAs, remote radio heads, amplifiers and RF combining products.

MWJ: What is the size of the company today? What markets is the company most focused on?

DW: Today, KMW has revenues of approximately $105 M per year, and 850 employees with factories in Korea and China. Our primary focus is selling our RF base station products (filters, amplifiers, radio heads) to Tier 1 network infrastructure providers and antenna and specialized filter products to wireless operators.

MWJ: Is KMW particularly strong in specific geographical regions or is your global presence evenly distributed?

DW: We are strong in Korea, the US, Japan and China, with plans to expand into Europe and Latin America.

MWJ: What are some of the most popular RF products in the KMW portfolio? What differentiates them from competitive offerings?

DW: In a word, filters! KMW is unique in that it is a completely vertically integrated filter company, with patents on our own ceramics and manufacturing process. This enables Tier 1 network infrastructure providers to rely on KMW to provide them with a rapid time to market with top quality filters and subsystems. The most exciting product development is our new “Black Hole Filter” technology, replicating superconductor performance with passive and small size filters.

MWJ: How does KMW decide which products to develop?

DW: We look at where we can best use our technical advantages to benefit the wireless community and capture new business. Of course, keeping a close eye on market directions and needs.

MWJ: What can you tell us about KMW’s investment in fundamental research as well as product development?

DW: KMW typically invests a significant share of its resources in filter, antenna and advanced PA research.

MWJ: How did the Black Hole ‘triple-mode’ filter technology come about?

DW: Black Hole Filter is our name for the world’s first commercialized triple mode filter. Triple mode filters have been discussed in text books and white papers for many years, but the complexity of construction has made consistent tuning in a manufacturing process all but impossible. Dr. Kim has been working on a method of simplifying the construction of a triple mode filters for over 10 years. Recently, he was able to create a revolutionary method of constructing and manufacturing a triple mode filter using our own ceramic formulas, unique shapes and customized manufacturing process to create three independent frequency responses in a single filter pocket.

MWJ: What are its main benefits? Is there anything else like it on the market?

DW: Black Hole Filter creates three frequency responses in a single “pocket,” which can be used to design filters to provide extremely high rejection characteristics and low insertion loss in a small and passive package. Nothing else is commercially available on the market today with these characteristics.

MWJ: Which applications does the Black Hole Filter address?

DW: Any advanced filtering needs typically requiring six or more conventional pockets can utilize Black Hole Filter to reduce the size by up to 50%. Or in other cases, extremely sharp rejection filters, such as our 700 MHz LTE or the 800 MHz air to ground filter that provides over 40 db of rejection in less than 500 kHz, and can be produced in a small and passive package as opposed to previous technologies using cryogenic filters for similar performance results. Other applications such as enabling TDD/FDD systems to co-exist are being explored.

MWJ: Do you see the types of applications expanding in the future, such as military?

DW: Absolutely. Lighter weight, high performance filtering can be exceptionally valuable for military applications.

MWJ: Does KMW develop custom components?

DW: We specialize and concentrate on custom applications, typically designing our products to specific customer requirements, rather than providing a large catalogue of components.

MWJ: Is all the design and engineering work done in Korea?

DW: No, we have engineering teams in the US, China and Korea.

MWJ: Korea is producing a lot of good RF engineers these days. Can you attribute this to certain factors? Does the government play a role?

DW: Yes, the level of education in Korea is very high compared to other places in the word, particularly in technical fields such as engineering. Yes, the government plays a strong role in promoting the importance of technical careers and the external promotion of its technology abroad.

MWJ: How closely does KMW work with its customers to implement new solutions?

DW: We are continually producing new solutions covering WiMAX, UMTS, GSM, LTE and CDMA based on our customers’ needs. We have several key relationships where we have cooperative roadmap planning so that we have the right technology at the right time.

MWJ: What should we expect from KMW in the future?

DW: We will introduce more integrated packages with Black Hole Filter technology, including our upcoming advanced PA, remote radio and antenna technology, enabling the next generation of wireless RF products to operate more efficiently, lowering the end users total cost of ownership. Also, I believe you will see our technology being used to unlock unused spectrum, called guard bands, enabling commercial, military and government spectrum to utilize more of their allocated frequencies, without sacrificing performance.