CC2420-RTR1 datasheet(55/92 Pages) TI

55 / 92 page

CC2420

SWRS041B

Page 55 of 89

Unit

dBm

RF Att

30 dB

1AVG

1SA

Ref Lvl

3 dBm

Ref Lvl

3 dBm

Center 2.45 GHz

Span 2 MHz

200 kHz/

RBW

10 kHz

VBW

10 kHz

SWT

50 ms

-90

-80

-70

-60

-50

-40

-30

-20

-10

-97

Date:

23.OCT.2003

21:38:33

Figure 31. Single carrier output

33.2

Modulated spectrum

The

CC2420 has a built-in test pattern

generator that can generate pseudo

random

sequence

using

the

CRC

generator. This is enabled by setting

MDMCTRL1.TX_MODE

to 3 and issues an

STXON

command strobe. The modulated

spectrum is then available on the RF pins.

The low byte of the CRC word is

transmitted and the CRC is updated with

0xFF for each new byte. The length of the

transmitted data sequence is 65535 bits.

The transmitted data-sequence is then:

[Synchronisation header] [0x00, 0x78,

0xb8, 0x4b, 0x99, 0xc3, 0xe9, …]

Since a synchronisation header (preamble

and SFD) is transmitted in all TX modes,

this test mode may also be used to

transmit a known pseudorandom bit

sequence for bit error testing. Please note

that

CC2420

requires

symbol

synchronisation,

not

only

bit

synchronisation, for correct reception.

Packet error rate is therefore a better

measurement

for

the

true

performance.

Another option to generate a modulated

spectrum is to fill the TXFIFO with pseudo-

random

data

and

set

MDMCTRL1.TX_MODE

to 2.

CC2420 will

then

transmit

data

from

the

FIFO

disregarding a TXFIFO underflow. The

length of the transmitted data sequence is

then 1024 bits (128 bytes).

A plot of the modulated spectrum from

CC2420 is shown in Figure 32. Note that to

find the output power from the modulated

spectrum, the RBW must be set to 3 MHz

or higher.

CC2420-RTR1 数据表(PDF) 55 Page - Texas Instruments

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