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BAND TUNABLE CERAMIC BLOCK FILTER

IP.com Disclosure Number: IPCOM000005701D
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2001-Oct-29
Document File: 1 page(s) / 63K

Publishing Venue

Motorola

Related People

Richard Kommrusch: AUTHOR

Abstract

In some filter applications a band tunable filter could be smaller than a broadband filter and still meet all the selectivity requirements. As an example consider a mobile Telephone with a 26 MHz bandwidth and 45MHz separation between TX and Rx. Figure 1 shows the present type of filter.

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MOTOROLA Technical Developments Volume a October 1966

BAND TUNABLE CERAMIC BLOCK FILTER

by Richard Kommrusch

   In some filter applications a band tunable filter could be smaller than a broadband filter and still meet all the selectivity requirements. As an example consider a mobile Telephone with a 26 MHz bandwidth and 45MHz separation between TX and Rx. Figure 1 shows the present type of filter.

de g/-yy m ~~~,~,.-~~ 2

800 820 840 860 880 900 820 840 860 880 900

MHZ MHZ

   Since only 1 TX and Rx pair of frequencies are used at a time protection at the low end of the 25 MHz band is not needed when frequencies at the high end of the band are used. A filter that can move between two or more positions is shown in figure 2. The new movable filter will require about half the Q or smaller and fewer sections to meet the insertion loss and isolation requirements. In the past the only way of making a movable filter was to mechanically or electronically tune each pole of the filter separately or in a ganged fashion with preset adjustments for each pole or zero. (a complex setup) A new method has been found through experiments on Motorola block filters which have their frequency controlled by artwork on the top of the block. Figure 3 shows the method of creating the frequency shift by using a simple piece of dielectric material. It is either placed on the artwork or spaced above the artwork.

dielectric

artwork

block filter

Closed Low Frequency

    The only thing missing to complete...