Datasheet > FX919BD5

FX919BD5

更新时间： 2024-10-30 14:50:47

品牌	Logo	应用领域
CMLMICRO		光电二极管
页数	文件大小	规格书
4页	45K
描述
Modem-Support Circuit, CMOS, PDSO24,

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FX919BD5 技术参数

是否Rohs认证：	符合	生命周期：	Active
包装说明：	,	Reach Compliance Code：	compliant
HTS代码：	8542.39.00.01	风险等级：	5.68
Is Samacsys：	N	认证状态：	Not Qualified
Base Number Matches：	1

FX919BD5 数据手册

CML Semiconductor Products

AN/Data/9x9B/1 December 1997

FX919B and FX929B Fade Management

and ‘A’ Version Compatibility

Introduction

This application note is to be read in conjunction with the current FX919B and FX929B Data Sheets.

This document is issued to clarify points in currently published documents and to present new information

that will enable the user to easily understand and implement this 4-Level FSK product.

The FX919B and FX929B are CMOS integrated circuits that contain all of the baseband signal

processing and Medium Access Control (MAC) protocol functions required for a high performance 4-level

FSK Wireless Packet Data Modems. They are designed to interface with the modem host processor and the

radio modulation/demodulation circuits to deliver reliable two-way transfer of the application data over the

wireless link. The FX919B and FX929B are individually backwards compatible with the FX919A and FX929A

but offer better performance during radio-link fading and have selectable Tx symbol shapes.

This document describes issues and strategies relating to fading applications. It also describes pertinent

FX919B and FX929B features and controls which may be used in an FX919B or 929B based system.

Fade Management

Data Decoding and Receiver Training

In order to accurately decode a received data stream, a modem must properly recover its clock and

signal components which are then interpreted to reconstruct the transmitted data.

Because transmit and receive modems are independent circuits (having separate and different local

clock frequencies and signal levels) a receiving modem must be trained or synchronised, immediately prior

to each data transfer, to establish a common and co-ordinated sense of bit timing.

In addition, the receiver must also be trained to establish a sense of nominal signal amplitude and DC

offset, against which the received data signal is compared to properly interpret its data bit values. Training is

generally performed by transmitting a specific data stream, the preamble, which provides evident and

consistent timing (zero crossing) and amplitude (maximum peak-to-peak range) characteristics.

During the training period, a receiving modem adjusts its local clock and level circuits until the known

preamble data stream is accurately reconstructed. Once this adjustment is complete, the transmit and

receive modems are synchronised and user data can be reliably transferred. (Note that data transfer must

immediately follow the preamble or synchronisation could be lost due to relative clock and level drift between

transmit and receive modems.). However both the FX919 and FX929 have been designed to lock onto the

received signal without any preamble, as is required in an application such as RD-LAP (Please refer to

section 1.6.3 of the relevant data sheet).

The Fading Problem

In mobile wireless applications, dynamic changes in the radio channel alter the phase and amplitude of

received signals. In order to maintain its synchronisation through these changes, a receiving FX919B and

FX929B uses feedback techniques to dynamically revise its local clock and level circuits according to the

changing nature of the received signal. However the receive-level measurement circuits on wireless data

modems such as the FX919 and FX929 can also be disturbed by short, large-amplitude noise bursts, as can

occur at the discriminator output during deep fades.

12 3 4

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与FX919BD5相关器件

型号	品牌	获取价格	描述	数据表
FX919BP4	CMLMICRO	获取价格	Modem-Support Circuit, CMOS, PDIP24,
FX929A	CMLMICRO	获取价格	4-Level FSK Modem Data Pump
FX929AD2	CMLMICRO	获取价格	4-Level FSK Modem Data Pump
FX929AD5	CMLMICRO	获取价格	4-Level FSK Modem Data Pump
FX929AP4	CMLMICRO	获取价格	4-Level FSK Modem Data Pump
FX929B	CMLMICRO	获取价格	CML Semiconductor Products 4-Level FSK Modem Data Pump
FX929BD2	CMLMICRO	获取价格	Modem-Support Circuit, CMOS, PDSO24,
FX929BD5	CMLMICRO	获取价格	Modem-Support Circuit, CMOS, PDSO24,
FX949	CMLMICRO	获取价格	CDPD Wireless Modem Data Pump
FX949L4	CMLMICRO	获取价格	CDPD Wireless Modem Data Pump

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