Application Notes/Frequency Tuning Address

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Introduction

Pole/Zero utilizes an eight-bit scheme for tune words to digitally control tuning of the center frequency across its standard product line of Bandpass filters.  This eight- bit scheme is shown in the following table.

Tune Word	Result
00000000 thru 11111010	Lowest tuned frequency (251 total tune codes) Highest tuned frequency
11111011 thru 11111110	RF In/Out Isolation Filter Blanked
11111111	Power saver mode; all PIN diodes turned off

There are 250 equally spaced tuning increments across each standard filter band, resulting in 251 tune words from 00000000 to 11111010.  The last 5 tune words are reserved for housekeeping functions:

Calculating a Tune Address:

The binary tuning word is determined by the following relationship:



Example: If you wish to tune to 322 MHz using a 225 to 400 MHz filter, the tune word is:

     (10001011 binary)

NOTE: Round off to the nearest decimal integer!