SX1211I084TRT(2007) Просмотр технического описания (PDF) - Semtech Corporation

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SX1211I084TRT
(Rev.:2007)

Lowest Power Integrated UHF Transceiver Short Range Devices

Semtech Corporation 

ADVANCED COMMUNICATIONS & SENSING

3.4. Receiver Description

The SX1211 is set to receive mode when MCParam_Chip_mode = 011.

First down-

conversion

Second down-

conversion

RSSI

LNA

LO2 Rx

OOK

demod

Bit

synchronizer

FSK

demod

LO1 Rx

SX1211

Control logic

-Pattern recognition

-FIFO handler

-SPI interface

-Packet handler

RF

IF1

Baseband, IF2 in OOK

Figure 15: Receiver Architecture

3.4.1. Architecture

The SX1211 receiver employs a super-heterodyne architecture. Here, the first IF is 1/9th of the RF frequency

(approximately 100MHz). The second down-conversion mixes the I and Q signals to base band in the case of the

FSK receiver (Zero IF) and to a low-IF (IF2) for the OOK receiver.

LO2

Rx

Second

down-conversion

First

down-conversion

0

IF2=0

in FSK

mode

IF1

≈100MHz

Second

down-conversion

Figure 16: FSK Receiver Setting

Image

frequency

LO1 Rx

Channel

Frequencyl

First

down-conversion

0

IF2<0

in FSK

mode

equal to fo

IF1

≈100MHz

LO2 Rx

Figure 17: OOK Receiver Setting

Image

frequency

LO1 Rx

Channel

Frequency

After the second down-conversion stage, the received signal is channel-select filtered and amplified to a level

adequate for demodulation. Both FSK and OOK demodulation are available. Finally, an optional Bit Synchronizer

(BitSync) is provided, to be supply a synchronous clock and data stream to a companion uC in Continuous mode,

V3.0 – august 15th, 2007

Page 24 of 73

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