Rainbow-electronics ATmega128RFA1 Uživatelský manuál stáhnout pdf (Strana 76)

8266A-MCU Wireless-12/09

ATmega128RFA1

9.6.2 Transmitter (TX)

9.6.2.1 Overview

The transmitter consists of a digital base band processor (TX BBP) and an analog front

end as shown in the following figure.

Figure 9-21. Transmitter Block Diagram

PLL – TX M odulation PA

Ext. RF front-end and

Output Power Control

DIG3/4

RFP

RFN

TX D ata

Analog Dom ain

TX BBP

Control

Buf

Digital Dom ain

Fram e

Buffer

µC

I/F

Registers

I/O

Memory

Space

$01FF

$017F

$0180

$0140

The TX BBP reads the frame data from the Frame Buffer and performs the bit-to-

symbol and symbol-to-chip mapping as specified by IEEE 802.15.4 in section 6.5.2.

The O-QPSK modulation signal is generated and fed into the analog radio front end.

The fractional-N frequency synthesizer (PLL) converts the baseband transmit signal to

the RF signal which is amplified by the power amplifier (PA). The PA output is internally

connected to bidirectional differential antenna pins (RFP, RFN) so that no external

antenna switch is needed.

9.6.2.2 Frame Transmit Procedure

The frame transmit procedure including writing PSDU data in the Frame Buffer and

initiating a transmission is described in section "Frame Transmit Procedure" on page

84. The controller must ensure to provide valid frame data before starting the frame

transmission. For save operation, it is recommended to write the complete frame into

the Frame Buffer before starting the frame transmission.

9.6.2.3 Configuration

The maximum output power of the transmitter is typically +3.5 dBm. The output power

can be configured via the TX_PWR bits of register PHY_TX_PWR. The output power of

the transmitter can be controlled over a 20 dB range.

A transmission can be started from PLL_ON or TX_ARET_ON state by writing ‘1’ to bit

SLPTR of the TRXPR register or by writing TX_START command to the TRX_CMD bits

of register TRX_STATE.

9.6.2.4 TX Power Ramping

The PA buffer and PA are enabled sequentially to optimize the output power spectral

density (PSD). A timing example using default settings illustrates the sequence in the

next figure. In this example the transmission is initiated with the rising edge of the

SLPTR bit. The radio transceiver state changes from PLL_ON to BUSY_TX. The

modulation starts 16 µs after SLPTR.

1 2 ... 71 72 73 74 75 76 77 78 79 80 81 ... 523 524

Komentáře k této Příručce

Žádné komentáře

Rainbow-electronics ATmega128RFA1 Uživatelský manuál Strana 76

Komentáře k této Příručce

Související produkty a manuály pro Senzory Rainbow-electronics ATmega128RFA1