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Preliminary Technical Data

ADF7021

Rev. PrI | Page 17 of 44

SPECTRAL SHAPING

Gaussian or raised cosine filtering can be used to improve

transmit spectral efficiency. The ADF7021 supports Gaussian

filtering (BT = 0.5) on 2FSK modulation. Raised cosine filtering

(alpha = 0.5) can be used with 2FSK, 3FSK, or 4FSK

modulation.

Gaussian Frequency Shift Keying (GFSK)

Gaussian frequency shift keying reduces the bandwidth

occupied by the transmitted spectrum by digitally prefiltering

the transmit data. The bandwidth time (BT) product of the

Gaussian filter used is 0.5.

Gaussian filtering can just be used with 2FSK modulation. This

is selected by setting Bits R2_DB[4:6] to 001.

Raised Cosine Filtering

Raised cosine filtering provides digital prefiltering of the

transmit data using a rasied cosine filter with a roll-off factor

(alpha) of 0.5. Rasied cosine filtering can be used with 2FSK,

3FSK, and 4FSK.

Raised cosine filtering is enabled by setting Bits R2_DB[4:6] as

outlined in Table 7.

MODULATION AND FILTERING OPTIONS

The various modulation and data filtering options are described

in Table 7.

Table 7. Modulation and Filtering Options on the ADF7021

Modulation

Data Filtering

R2_DB[4:6]

2FSK

None

000

Gaussian

001

Raised cosine

101

3FSK

None

010

Raised cosine

110

4FSK

None

011

Raised cosine

111

Oversampled 2FSK

None

100

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