CC1110-RTR1 datasheet(160/203 Pages) TI

160 / 203 page

CC1110

CC1110 PRELIMINARY Datasheet (Rev. 1.01) SWRS033A

Page 160 of 202

15.6 Receiver Channel Filter Bandwidth

In order to meet different channel width

requirements, the receiver channel filter is

programmable. The MDMCFG4.CHANBW_E

and MDMCFG4.CHANBW_M configuration

registers control the receiver channel filter

bandwidth, which scales with the crystal

oscillator frequency. The following formula

gives the relation between the register

settings and the channel filter bandwidth:

CHANBW

XOSC

channel

CHANBW

)·

(

⋅

The

CC1110

supports

channel

filter

bandwidths shown in Table 44.

Table 44: Channel filter bandwidths [kHz] (26 MHz crystal)

Above 300kHz bandwidth, however, the

sensitivity and blocking performance may

be somewhat degraded.

For best performance, the channel filter

bandwidth should be selected so that the

signal bandwidth occupies at most 80% of

the channel filter bandwidth. The channel

centre tolerance due to crystal accuracy

should also be subtracted from the signal

bandwidth.

The

following

example

illustrates this:

With the channel filter bandwidth set to

500kHz, the signal should stay within 80%

of 500kHz, which is 400kHz. Assuming

915MHz frequency and ±20ppm frequency

uncertainty for both the transmitting device

and the receiving device, the total

frequency

uncertainty

±40ppm of

915MHz, which is ±37kHz. If the whole

transmitted signal bandwidth is to be

received within 400kHz, the transmitted

signal bandwidth should be maximum

400kHz–2·37kHz, which is 326kHz

15.7 Demodulator, Symbol Synchronizer and Data Decision

CC1110 contains an advanced and highly

configurable

demodulator.

Channel

filtering

and

frequency

offset

compensation is performed digitally. To

generate the RSSI level (see section

15.10.2 for more information) the signal

level in the channel is estimated. Data

filtering is also included for enhanced

performance.

15.7.1 Frequency Offset Compensation

When using FSK or MSK modulation, the

demodulator will compensate for the offset

between the transmitter and receiver

frequency,

within

certain

limits,

estimating the centre of the received data.

This value is available in the FREQEST

status register.

By issuing the SAFC command strobe, the

measured

offset,

MDMCFG4.

MDMCFG4.CHANBW_E

CHANBW_M

812

406

203

102

650

325

162

541

270

135

464

232

116

CC1110-RTR1 데이터시트(PDF) 160 Page - Texas Instruments

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