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AFE analog front-end.
Digital narrow-band
receiver.
Input specifications.
Input voltage range
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+5 dBm
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Input type
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Single-ended, AC coupled
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Input impedance
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50 ohms
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Input frequency range (3dB)
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30 MHz
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Clock
specifications.
F sampling
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BW=200KHz
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BW=12.5KHz
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BW=25KHz
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50MHz
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66.66MHz
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DDS AD9851
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ADC performance.
AD6644, AD6645
specifications
resolution
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14 bit
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Max conversion rate
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65 MSPS
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Min conversion rate
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24 MSPS
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SNR
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74 dB @2.2MHz input, typical
73 dB @15.5MHz
input, typical
72 dB @30.5MHz
input, typical
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Two tone SFDR
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100 dBFS, typical
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Analog input bandwith
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250 MHz typical full scale
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Data format
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14 bit 2s complement
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DDC performance.
AD6620
filter
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decimation
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Cic2
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2..16
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Rcf (max 256 taps)
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Cic5
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1..32
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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
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BW 25KHz
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BW 12.5KHz
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AGC range
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+45 dB
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AGC NF
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-7 dB
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ADC
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74 dB
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DDC processing gain
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30 dB
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33 dB
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total
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145 dB
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148 dB
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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
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BW 25KHz
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BW 12.5KHz
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AGC range
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+30 dB
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AGC NF
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ADC
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60 dB
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DDC processing gain
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33 dB
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36 dB
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total
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145 dB
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148 dB
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Processing gain=10 log
(50MHz/2*25KHz) = 33 dB
Input data port
Control data
port:
via LPT (MODE =0)
signal
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A[2..0]
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address lines
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D[7..0]
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data lines
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CS
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chip select
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RD
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read strobe
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WR
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write strobe
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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
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Device |
Bits resolution |
transfer rate
(MHz)
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hh |
xx |
yy |
supply voltage (V)
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power |
package |
price (x1000)
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LPT
(parallel) |
PIC16F876 port |
8 |
0.900 |
750 |
82 |
70 |
3.3 |
750 |
TQFP-64 |
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USB
(serial) |
FT232BM |
14 |
0.115 |
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PCI
(parallel) |
PLX9656 |
64 |
66 |
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3.3 |
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DSP
(stand-alone) |
ADSP2191 |
24x2(serial) |
70 |
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