TXM-418-LR View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

TXM-418-LR

LR Series Receiver Module

Unspecified 

Module Description

The LR receiver is a low-cost, high-performance synthesized AM / OOK

receiver, capable of receiving serial data at up to 10,000bps. Its exceptional

sensitivity results in outstanding range performance. The LR’s compact

surface-mount package is friendly to automated or hand production. LR

Series modules are capable of meeting the regulatory requirements of

many domestic and international applications.

The receiver's outstanding typical sensitivity of –112dBm enables system

ranges of up to 1.5 miles (2,500m) when paired with an LR Series

transmitter operating at full power and good antennas. Legal regulations

in the various countries will require the transmitter output power to be

reduced which will reduce range. Following the legal output limit for

transmitters in the United States, systems based on the LR Series can

achieve ranges of up to 3,000 feet (1,000m).

50Ω RF IN

(Antenna)

Band Select

Filter

LNA

10.7MHz

0˚

IF Filter

-

∑

Limiter

+

Data Slicer

Data Out

90˚

RSSI/Analog

PLL

VCO

XTAL

Figure 11: LR Series Receiver Block Diagram

Theory of Operation

The LR Series receiver is designed

to recover data sent by an AM

or Carrier-Present Carrier-Absent

Data

(CPCA) transmitter, also referred to

as CW or On-Off Keying (OOK). This Carrier

type of modulation represents a logic

low '0’ by the absence of a carrier

and a logic high ‘1’ by the presence Figure 12: CPCA (AM) Modulation

of a carrier. This modulation method affords numerous benefits. The two

most important are: 1) cost-effectiveness due to design simplicity and 2)

higher allowable output power and thus greater range in countries (such as

the U.S.) that average output power measurements over time. Please refer

to Linx Application Note AN-00130 for a further discussion of modulation

techniques.

The LR receiver utilizes an advanced single-conversion superheterodyne

architecture. Transmitted signals enter the module through a 50Ω RF

port intended for single-ended connection to an external antenna. RF

signals entering the antenna are filtered and then amplified by an NMOS

cascode Low Noise Amplifier (LNA). The filtered, amplified signal is then

down-converted to a 10.7MHz Intermediate Frequency (IF) by mixing it

with a low-side Local Oscillator (LO). The LO frequency is generated by

a Voltage Controlled Oscillator (VCO) locked by a Phase-Locked Loop

(PLL) frequency synthesizer that utilizes a precision crystal reference. The

mixer stage incorporates a pair of double-balanced mixers and a unique

image rejection circuit. This circuit, along with the high IF frequency and

ceramic IF filters, reduces susceptibility to interference. The IF frequency is

further amplified, filtered, and demodulated to recover the baseband signal

originally transmitted. The baseband signal is squared by a data slicer and

output to the DATA pin. The architecture and quality of the components

utilized in the LR module enable it to outperform many far more expensive

receiver products.

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