ADI AD9957 1GSPS上变换器解决方案

ADI公司的AD9957是具有18位IQ数据通路和14位DAC的1GSPS正交数字上变换器.它在单片上集成了高速直接数字频率合成器(DDS),高性能高速14位数模转换器(DAC),时钟乘法器电路,数字滤波器以及其它DSP功能,能为有线或无线通信系统的数据传输提供基带上变换,广泛用于HFC数据,电话以及视频调制解调器,无线基站传输,宽带通信传输以及网络电话.本文介绍了AD9957的主要性能,方框图以及评估板的电路图和所用元器件清单(BOM).

1 GSPS Quadrature Digital Upconverter with 18-Bit IQ Data Path and 14-Bit DAC AD9957



The AD9957 functions as a universal I/Q modulator and agile upconverter for communications systems where cost, size, power consumption, and dynamic performance are critical. The AD9957 integrates a high speed, direct digital synthesizer (DDS), a high performance, high speed, 14-bit digital-to-analog converter (DAC), clock multiplier circuitry, digital filters, and other DSP functions onto a single chip. It provides for baseband upconversion for data transmission in a wired or wireless communications system.
The AD9957 is the third offering in a family of quadrature digital upconverters (QDUCs) that includes the AD9857 and AD9856. It offers performance gains in operating speed, power consumption, and spectral performance. Unlike its predecessors, it supports a 16-bit serial input mode for I/Q baseband data. The device can alternatively be programmed to operate either as a single tone, sinusoidal source or as an interpolating DAC.

The reference clock input circuitry includes a crystal oscillator, a high speed, divide-by-two input, and a low noise PLL for multiplication of the reference clock frequency.
The user interface to the control functions includes a serial port easily configured to interface to the SPORT of the Blackfin® DSP and profile pins to enable fast and easy shift keying of any signal parameter (phase, frequency, and amplitude).
主要特性:

1 GSPS internal clock speed (up to 400 MHz analog output) Integrated 1 GSPS 14-bit DAC
250 MHz I/Q data throughput rate
Phase noise ≤ −125 dBc/Hz (400 MHz carrier @ 1 kHz offset)
Excellent dynamic performance >80 dB narrow-band SFDR
8 programmable profiles for shift keying
SIN(x)/(x) correction (inverse sinc filter)
Reference clock multiplier
Internal oscillator for a single crystal operation
Software and hardware controlled power-down
Integrated RAM
Phase modulation capability
Multichip synchronization
Easy interface to Blackfin SPORT
Interpolation factors from 4× to 252×
Interpolation DAC mode
Gain control DAC
Internal divider allows references up to 2 GHz
1.8 V and 3.3 V power supplies
100-lead TQFP_EP package

主要应用:
HFC data, telephony, and video modems
Wireless base station transmission
Broadband communications transmissions
Internet telephony



详细请见数据表:
http://www.analog.com/UploadedFiles/Data_Sheets/AD9957.pdf



图2. AD9957 评估板电路图(1)



图3. AD9957 评估板电路图(2)

下表是评估板所用元器件清单(BOM):