SPIRIT1 datasheet(46/94 Pages) STMICROELECTRONICS

46 / 94 page

Transmission and reception

SPIRIT1

46/94

Doc ID 022758 Rev 3

Equation 2

This allows the setting of up to 256 channels with a programmable raster. The raster

granularity is about 793 Hz at 26 MHz and becomes about 1587 Hz at 52 MHz.

The actual channel spacing is from 793 Hz to 202342 Hz in 793 Hz steps for the 26 MHz

configuration and from 1587 to 404685 Hz in 1587 Hz steps for the 52 MHz configuration.

The base carrier frequency, i.e. the carrier frequency of channel #0, is controlled by the

SYNT0, SYNT1, SYNT2, and SYNT3 registers according to the following formula:

Equation 3

where:

●

fXO is the frequency of the XTAL oscillator (typically 24 MHz, 26 MHz, 48 MHz, or 52

MHz)

●

SYNT is a programmable 26-bit integer.

Equation 4

Equation 5

The offset frequency is a correction term which can be set to compensate the crystal

inaccuracy after e.g. lab calibration.

Equation 6

where:

●

FC_OFFSET is a 12-bit integer (expressed as 2's complement number) set by the

FC_OFFSET[1:0] registers

Furthermore, the selection between VCOH (“high”) and VCOL (“low”) in the frequency

synthesizer according to the band selected and the VCO threshold is required.

If the center frequency is below the frequency threshold for that frequency band, the VCO_L

must be selected by setting the bit 2 VCO_L_SEL field in the SYNTH_CONFIG register.

CHNUM

CHSPACE

offset

base

⋅

⎟

⎠

⎞

⎜

⎝

⎛

⋅

base

SYNT

M, S

B5)

(

)

(

)

(

)

very

{{

1 if REFDIV 0 (internal reference divider is disabled)

2 if REFDIV 1 (internal reference divider is enabled)

⎩

⎨

⎧

OFFSET

offset

⋅

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