AFE analog front-end.

Digital narrow-band receiver.

Input specifications.

Input voltage range

+5 dBm

 

Input type

Single-ended, AC coupled

 

Input impedance

50 ohms

 

Input frequency range (3dB)

30 MHz

 

Clock specifications.

F sampling

BW=200KHz

BW=12.5KHz

BW=25KHz

 

50MHz

       

66.66MHz

       

DDS AD9851

       

ADC performance.

AD6644, AD6645 specifications

resolution

14 bit

 

Max conversion rate

65 MSPS

 

Min conversion rate

24 MSPS

 

SNR

74 dB @2.2MHz input, typical

73 dB @15.5MHz input, typical

72 dB @30.5MHz input, typical

 

Two tone SFDR

100 dBFS, typical

 

Analog input bandwith

250 MHz typical full scale

 

Data format

14 bit 2’s complement

 

DDC performance.

AD6620

filter

decimation

   

Cic2

2..16

   

Rcf (max 256 taps)

     

Cic5

1..32

   

BW = 40KHz (FM)

BW = 16KHz(SSB, CW)

Dynamic range.

The dynamic range is determined by the following component contributions.

Clock 50MHz

AGC : AD8367

ADC : AD6645 (14 bit )

DDC : AD6620

 

BW 25KHz

BW 12.5KHz

 

AGC range

+45 dB

   

AGC NF

-7 dB

   

ADC

74 dB

   

DDC processing gain

30 dB

33 dB

 

total

145 dB

148 dB

 

Processing gain=10 log (Fsampling/2*BW)

Processing gain=10 log (50MHz/2*25KHz) = 30 dB

Clock 50MHz

AGC :

ADC : AD6600 (11 bit + 3 bit RSSI )

DDC : AD6620

 

BW 25KHz

BW 12.5KHz

 

AGC range

+30 dB

   

AGC NF

     

ADC

60 dB

   

DDC processing gain

33 dB

36 dB

 

total

145 dB

148 dB

 

Processing gain=10 log (50MHz/2*25KHz) = 33 dB

Input data port

Control data port:

via LPT (MODE =0)

signal

 

A[2..0]

address lines

 

D[7..0]

data lines

 

CS

chip select

 

RD

read strobe

 

WR

write strobe

 

Output data port.

Serial master mode

Serial slave mode


Blocchi fondamentali del ricevitore digitale.

  • AFE analog front-end: filtro passa-banda + AGC

  • ADC AD converter (AD6640, AD6645 o AD6600)

  • DDC DIGITAL DOWN CONVERTER (AD6620)

  • HOST interfaccia verso il PC :

    • hardware interfaccia tramite LPT , da considerare anche USB e PCI

    • software di controllo e di acquisizione su PC

  • funzionamento stand-alone con scheda dsp


Confronto

Transfer rate del segnale in uscita

Device Bits resolution transfer

rate

(MHz)

hh xx yy supply voltage

(V)

power package price

(x1000)

LPT (parallel)
PIC16F876 port 8 0.900 750 82 70 3.3 750 TQFP-64  
                   
                   
USB (serial)
FT232BM 14 0.115              
                   
                   
PCI (parallel)
PLX9656 64 66       3.3      
                   
DSP (stand-alone)
ADSP2191 24x2(serial) 70              
                   
                   

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