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RXM-418-LC-S 参数 Datasheet PDF下载

RXM-418-LC-S图片预览
型号: RXM-418-LC-S
PDF下载: 下载PDF文件 查看货源
内容描述: LC系列接收器模块数据 [LC SERIES RECEIVER MODULE DATA]
分类和应用:
文件页数/大小: 9 页 / 381 K
品牌: ETC [ ETC ]
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MODULE DESCRIPTION  
POWER SUPPLY REQUIREMENTS  
The receiver module requires a clean, well-regulated  
power source. While it is preferable to power the unit from  
a battery, the unit can also be operated from a power  
supply as long as noise and ‘hash’ is less than 20 mV. A  
10 resistor in series with the supply followed by a 10µF  
tantalum capacitor from VCC to ground will help in cases  
where the quality of supply power is poor. Please note that  
operation from 4.7 to 5.2 volts requires the use of an  
The RXM-LC-S is a low-cost, high-performance Surface Acoustic Wave (SAW)  
based Carrier-Present Carrier-Absent (CPCA) receiver, capable of receiving  
serial data at up to 5,000 bits/second. Its exceptional sensitivity provides  
outstanding range at the maximum data rate. While oriented toward high-volume  
automated production, the LC-S’s compact surface-mount package is also  
friendly to prototype and hand production. When combined with a Linx LC series  
transmitter, a highly reliable RF link capable of transferring digital data over line-  
of-sight distances in excess of 300 feet (90m) is formed.  
external 200 resistor placed in series with VCC  
.
Figure 15: Supply Filter  
THE DATA OUTPUT  
50 Ω RF IN  
(Ant.)  
A CMOS-compatible data output is available on pin 8. This output is normally used to  
drive directly a digital decoder IC or a microprocessor that is performing the data  
decoding. The receiver’s output is internally qualified, meaning that it will only  
transition when valid data is present. In instances where no carrier is present the  
output will remain low. Since a UART utilizes high marking to indicate the absence of  
data, a designer using a UART may wish to insert a logic inverter between the data  
output of the RXM-LC-S and the UART.  
Gilbert Cell  
Mixer/Amp  
10.7 Mhz  
Bandpass Filter  
Band Select  
Filter  
DATA  
pre-  
amplifier  
10.7 Mhz  
Limiting Amp Ceramic Filter  
AM Detector  
Data Slicer  
SAW Local Oscillator  
It is important to realize that the data output of the receiver may be subject to some  
pulse stretching or shortening. This is caused by a combination of oscillator start-up  
time on the transmitter and ring-down time in the receiver’s ceramic filter. It is  
important to consider this effect when planning protocol. To learn more about protocol  
considerations for the LC series we suggest you read Linx applications note #00232.  
Figure 13: LC Series Receiver Block Diagram  
THEORY OF OPERATION  
The RXM-LC-S is designed to recover  
data sent by a CPCA transmitter. This  
type of AM modulation is often referred  
to by other designations including CW  
and OOK. As the CPCA designation  
suggests, this type of modulation  
represents a logic low ‘0’ by the  
absence of a carrier and a logic high ‘1’  
by the presence of a carrier. This  
modulation method affords numerous  
benefits. Two most important are: 1) Cost-effectiveness due to design simplicity  
and 2) Higher output power and thus greater range in countries (such as the US)  
which average output power measurements over time. Please refer to Linx  
application note #00130 for a further discussion of modulation techniques  
including CPCA.  
RECEIVING DATA  
Once a reliable RF link has been established, the challenge becomes how to  
effectively transfer data across it. While a properly designed RF link provides  
reliable data transfer under most conditions, there are still distinct differences from  
a wired link that must be addressed. Since the RXM-LC-S modules do not  
incorporate internal encoding/decoding, a user has tremendous flexibility in how data  
is handled.  
Daattaa  
Caarrrriieerr  
It is always important to separate what type of transmissions are technically  
possible from those that are legally allowable in the country of intended operation.  
You may wish to review application notes #00125 and #00140 along with Part 15  
Sec. 231 for further details on acceptable transmission content.  
Figure 14: CPCA (AM) Modulation  
Another area of consideration is that of data structure or protocol. If unfamiliar with  
the considerations for sending serial data in a wireless environment, you will want  
to review Linx application note #00232 (Considerations for sending data with the LC  
series). These issues should be clearly understood prior to commencing a  
significant design effort.  
The LC series utilizes an advanced single-conversion superhet design which  
incorporates a SAW device, high IF frequency and multi-layer ceramic filters.  
The SAW device has been in use for more than a decade but has only recently  
begun to receive the widespread acclaim its outstanding capabilities deserve. A  
SAW device provides a highly accurate frequency source with excellent  
immunity to frequency shift due to age or temperature. The use of SAW devices  
in both the LC transmitter and receiver modules allows the receiver’s pass  
opening to be quite narrow, thus increasing sensitivity and reducing  
susceptibility to near-band interference. The quality of components and overall  
architecture utilized in the LC series is unusual in a low-cost product and is one  
of the primary reasons the LC receivers are able to outperform even far more  
expensive products.  
If you want to transfer simple control or status signals such as button presses or  
switch closures, and your product does not have a microprocessor on board your  
product or you wish to avoid protocol development, consider using an encoder and  
decoder IC set. These chips are available from a wide range of manufacturers  
including: Microchip (Keeloq), Holtek (available directly from Linx), and Motorola.  
These chips take care of all encoding, error checking, and decoding functions and  
generally provide a number of data pins to which switches can be directly  
connected. In addition, address bits are usually provided for security and to allow  
the addressing of multiple receivers independently. These IC’s are an excellent way  
to bring basic Remote Control/Status products quickly and inexpensively to market.  
Additionally, it is a simple task to interface with inexpensive microprocessors such  
as the Microchip PIC or one of many IR, remote control, DTMF, and modem IC’s.  
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