Filter specifiers are accustomed to combing through catalogs, in search of a component that will match their desired set of performance parameters. By combining the power of the Internet with its own extensive filter database and filter-design software, however, K & L Microwave has developed a specifying tool that is sure to send a great many filter catalogs to the trash. Called K & L Filter Wizard™, the online program is free for visitors to the K & L website at www.klmicrowave.com.

K & L's customers, of course, will recognize that Filter Wizard is actually an evolution of earlier filter-specifying tools developed by the company. Beginning with the firm's breakthrough Reflex program in the latter 1980s—one of the first software programs that allowed users to essentially design their own filter model—and continuing with the CD-ROM-based KeL-fil software tool that helped guide users in the selection of ceramic-based filters, the KeL-com version for lumped-element filters and, most recently, the Mini-Max selection program for users of surface-mount filters, the company has established a history of providing value-added tools to its customers free of charge. Such tools have not only simplified the specification process, but also doubled as educational resources to help train young engineers in various aspects of filter design and performance.

With Filter Wizard, the company has ambitiously hit a new high-water mark for filter-specifying tools. The on-line program, which is expected to launch during the upcoming Microwave Theory & Techniques Symposium (MTT-S) next month (Fort Worth, TX, June 8-10, 2004), is both powerful and easy to use. The first version covers all-pole and elliptical (pole-placed) bandpass filters; later this year, the software will be upgraded to include other filter responses, such as lowpass, highpass, and band-reject filters.

The opening screen of K & L's Filter Wizard (Fig. 1) indicates the four basic steps to using the tool: enter specifications, review results of the search based on those specifications, drill down to further details on a filter or filters of interest, and send an e-mail request for quote to K & L. A large response curve for a typical bandpass filter highlights this opening screen, with blank boxes left for operators to enter their desired specifications, such as center frequency and bandwidth (both in MHz), the passband definition (such as 0.5 dB, 1 dB, 3 dB, or equiripple), passband ripple, and rejection at specific frequencies on the lower and upper filter skirts. Once entered, the user can begin the search of K & L's extensive filter database for any and all filters meeting these specifications (as minimum requirements) by simply clicking on the "Find Matches" button. The resulting search spans products covering one of the broadest ranges of unloaded Q in the industry. A "Reset Entries" button is provided to allow the user to return to a set of default inputs.

The search results are presented in tabular form (Fig. 2), with the filter type, product identification number, insertion loss, and size listed for comparison. One particularly useful entry in this table is the listing for relative price, allowing users to not only compare the relative expense of each of the selected filters, but the costs of the various filter technologies, such as the KeL-fil, cavity, and cavity elliptic filters selected in Fig. 2. On this screen, operators have the option of displaying physical dimensions in SAE (inches) or metric (millimeters) units.

From this tabular view operators can click on the "Details" button for any one of the listed filters and shift to a screen with more complete product details (Fig. 3), including a spectral plot showing insertion loss, return loss, and group delay. Users can zoom in and out on this spectral display, for example, to take a closer look at passband ripple. The information listed in the "Details" screen includes a comparison of all requested specifications with the actual specifications for that filter. The example of Fig. 3 shows how the program matches the key specifications, meeting both the stopband attenuation requirements and the desired insertion loss. The "Details" screen repeats the dimensional information of the previous screen, but also includes a package outline drawing, complete with coaxial connectors in the case of this example, and a button for downloading S-parameters.

The final step in using K & L's Filter Wizard is the "Request for Quote" screen, which smartly includes not only the requested filter's identification number, but also key specifications, such as the center frequency, bandwidth, and stopband frequencies. This screen prompts a user for name, address, e-mail, and other contact information, and provides room for additional comments and requirements (using multiple screens), including screening and environmental requirements. By clicking on the "Process Request" button at the bottom of the screen, an e-mail with the quote information is sent to K & L where it will be processed within 24 hours. If further information is needed to process the quote, K & L staff will contact the customer.

In addition to selecting filters, Filter Wizard allows operators to design cavity filters for optimal physical dimensions given a set of specifications. Specifiers can actually develop a cavity filter solution for minimal size while still meeting their electrical performance requirements.

The initial version of Filter Wizard covers all-pole and pseudo-elliptic bandpass filters and provides solutions by means of four technologies: ceramic, lumped component, cavity, and waveguide. Highpass and lowpass filters will be added to the follow-up version (expected by the end of summer), followed by band-reject filters and diplexers in subsequent versions. K & L Microwave, Inc., 2250 Northwood Dr., Salisbury, MD 21801; (410) 749-2424, FAX: (410) 749-5725, e-mail: sales@klmicrowave.com, Internet: www.klmicrowave.com.