参数资料
型号: AD9755-EB
厂商: Analog Devices Inc
文件页数: 13/28页
文件大小: 0K
描述: BOARD EVAL FOR AD9755
产品培训模块: DAC Architectures
标准包装: 1
系列: TxDAC+®
DAC 的数量: 1
位数: 14
采样率(每秒): 300M
数据接口: 并联
设置时间: 11ns
DAC 型: 电流
工作温度: -40°C ~ 85°C
已供物品:
已用 IC / 零件: AD9755
相关产品: AD9755ASTZRL-ND - IC DAC 14BIT 300MSPS 48-LQFP
AD9755ASTZ-ND - IC DAC 14BIT 300MSPS 48-LQFP
REV. B
AD9755
–20–
–30
CENTER 860MHz
–40
–50
–60
–70
–80
–90
–110
–120
11MHz/
SPAN 110MHz
FREQUENCY (MHz)
REFERENCE
LEVEL
(dBm)
COMMENT A: 25 MSYMBOL, 64 QAM, CARRIER = 825MHz
A
1 [T1]
CH PWR
ACP UP
ACP LOW
1 [T2]
2 [T2]
–100.55dBm
859.91983968MHz
–66.52dBm
–60.16dBm
–6.86dBm
33.62dBm
–49.91983968MHz
33.62dBm
–49.91983968MHz
2
CU1
CL1
C0
–100.55dBm
859.91983968MHz
VBW
10kHz
SWT
2.8s UNIT dBm
–20
CU1
–100
CL1
2mA
Figure 31. Signal of Figure 28 Mixed to Carrier
Frequency of 800 MHz
Effects of Noise and Distortion on Bit Error Rate (BER)
Textbook analysis of Bit Error Rate (BER) performance is gen-
erally stated in terms of E (energy in watts-per-symbol or
watts-per-bit) and NO (spectral noise density in watts/Hz). For
QAM signals, this performance is shown graphically in Figure 32.
M represents the number of levels in each quadrature PAM signal
(i.e., M = 8 for 64 QAM, M = 16 for 256 QAM). Figure 32
implies gray coding in the QAM constellation, as well as the use
of matched filters at the receiver, which is typical. The
horizontal axis of Figure 32 can be converted to units of energy/
symbol by adding to the horizontal axis 10 log of the number of
bits in the desired curve. For instance, to achieve a BER of 1e-6
with 64 QAM, an energy per bit of 20 dB is necessary. To
calculate energy per symbol, add 10 log(6) or 7.8 dB. Therefore
64 QAM with a BER of 1e-6 (assuming no source or channel
coding) can theoretically be achieved with an energy/symbol-
to-noise (E/NO) ratio of 27.8 dB. Due to the loss and interferers
inherent in the wireless path, this signal-to-noise ratio must be
realized at the receiver to achieve the given bit error rate.
Distortion effects on BER are much more difficult to determine
accurately. Most often in simulation, the energies of the strongest
distortion components are root-sum-squared with the noise, and
the result is treated as if it were all noise. That being said, if the
example above of 64 QAM with the BER of 1e-6, using the E/NO
ratio is much greater than the worst-case SFDR, the noise will
dominate the BER calculation.
The AD9755 has a worst-case in-band SFDR of 47 dB at the
upper end of its frequency spectrum (see TPCs 2, 3). When
used to synthesize high level QAM signals as described above,
noise, as opposed to distortion, will dominate its performance in
these applications.
SNR /BIT (dB)
1E0
1E–3
1E–6
20
5
0
SYMBOL
ERR
OR
PR
OB
ABILITY 1E–2
1E–5
1E–1
1E–4
10
15
16 QAM
64 QAM
4 QAM
Figure 32. Probability of a Symbol Error for QAM
DAC
LATCHES
DAC
INPUT
LATCHES
INPUT
LATCHES
PLL/DIVIDER
CLK+ CLK– PLLLOCK
DVDD AVDD
IOUTA
IOUTB
PORT 1
DATA
INPUT
PORT 2
DATA
INPUT
RSET2
1.9k
FSADJ
0.1 F
REFIO ACOM1 ACOM DCOM
AD9755
50
0.1 F
68
INPM
INPP
LOIM
LOIP
OUTP
OUTM
AD8343 ACTIVE MIXER
0.1 F
LOINPUT
M/A-COM ETC-1-1-13 WIDEBAND BALUN
Figure 30. QAM Transmitter Architecture Using AD9755 and AD8343 Active Mixer
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