ADF7021 datasheet(60/64 Pages) AD

60 / 64 page

ADF7021

Data Sheet

Rev. B | Page 60 of 64

TEST_DAC_GAIN

TEST DAC OFFSET

ADDRESS

BITS

PULSE EXTENSION

NO PULSE EXTENSION

EXTENDED BY 1

EXTENDED BY 2

EXTENDED BY 3

ED PEAK RESPONSE

FULL RESPONSE TO PEAK

0.5 RESPONSE TO PEAK

0.25 RESPONSE TO PEAK

0.125 RESPONSE TO PEAK

TEST DAC GAIN

...

NO GAIN

× 2^1

...

× 2^15

ED LEAK FACTOR

LEAKAGE =

2^–8

2^–9

2^–10

2^–11

2^–12

2^–13

2^–14

2^–15

Figure 76. Register 14—Test DAC Register Map

The demodulator tuning parameters, PULSE_EXTENSION,

ED_LEAK_FACTOR, and ED_PEAK_RESPONSE, can only be

enabled by setting R15_DB[4:7] to 0x9.

Using the Test DAC to Implement Analog FM DEMOD

and Measuring SNR

The test DAC allows the post demodulator filter out for both

linear and correlator demodulators to be viewed externally. The

test DAC also takes the 16-bit filter output and converts it to a

high frequency, single-bit output using a second-order, error

feedback Σ-Δ converter. The output can be viewed on the SWD

pin. This signal, when filtered appropriately, can then be used to

do the following:

•

Monitor the signals at the FSK post demodulator filter

output. This allows the demodulator output SNR to be

measured. Eye diagrams of the received bit stream can also

be constructed to measure the received signal quality.

•

Provide analog FM demodulation.

While the correlators and filters are clocked by DEMOD CLK,

CDR CLK clocks the test DAC. Note that although the test

DAC functions in regular user mode, the best performance is

achieved when the CDR_CLK is increased to or above the

frequency of DEMOD CLK. The CDR block does not function

when this condition exists.

Programming Register 14 enables the test DAC. Both the

linear and correlator/demodulator outputs can be multiplexed

into the DAC.

signal (to remove the IF component in the ddt case). It also has

a signal gain term to allow the usage of the maximum dynamic

range of the DAC.

ADF7021 датащи(PDF) 60 Page - Analog Devices

ADF7021 датащи(HTML) 60 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

датащи скачать

ссылки URL