Rainbow-electronics AT86RF231 User Manual download pdf (Page 10)

8111A–AVR–05/08

AT86RF231

4. General Circuit Description

This single-chip radio transceiver provides a complete radio transceiver interface between an

antenna and a microcontroller. It comprises the analog radio, digital modulation and demodula-

tion including time and frequency synchronization and data buffering. The number of external

components is minimized such that only the antenna, the crystal and decoupling capacitors are

required. The bidirectional differential antenna pins (RFP, RFN) are used for transmission and

reception, thus no external antenna switch is needed.

The AT86RF231 block diagram is shown in Figure 4-1 on page 10.

Figure 4-1. AT86RF231 Block Diagram

The received RF signal at pins RFN and RFP is differentially fed through the low-noise amplifier

(LNA) to the RF filter (PPF) to generate a complex signal, driving the integrated channel filter

(BPF). The limiting amplifier provides sufficient gain to drive the succeeding analog-to-digital

converter (ADC) and generates a digital RSSI signal. The ADC output signal is sampled by the

digital base band receiver (RX BBP).

The transmit modulation scheme is offset-QPSK (O-QPSK) with half-sine pulse shaping and 32-

length block coding (spreading) according to [1] and [2]. The modulation signal is generated in

the digital transmitter (TX BBP) and applied to the fractional-N frequency synthesis (PLL), to

ensure the coherent phase modulation required for demodulation of O-QPSK signals. The fre-

quency-modulated signal is fed to the power amplifier (PA).

A differential pin pair DIG3/DIG4 can be enabled to control an external RF front-end.

Two on-chip low-dropout voltage regulators (A|DVREG) provide the analog and digital 1.8V

supply.

AVREG

LNA

PLL PA

PPF BPF Limiter ADC

AGC

ext. PA and Power

Control

Configuration Registers

SPI

(Slave)

RSSI

IRQ

CLKM

/RST

SLP_TR

/SEL

MISO

MOSI

SCLK

DIG3/4

RFP

RFN

TX Data

Control Logic

DIG2

Antenna Diversity

FTN, BATMON

XOSC

XTAL1

XTAL2

Analog Domain Digital Domain

AES

DIG1/2

DVREG

RX BBP

Frame

Buffer

TX BBP

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 179 180

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Rainbow-electronics AT86RF231 User Manual Page 10

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