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| 型号： | AD8349ARE-REEL7 |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 衰减器 |
| 英文描述： | 700 MHz to 2700 MHz Quadrature Modulator |
| 中文描述： | 700 MHz - 2700 MHz RF/MICROWAVE QPSK MODULATOR |
| 封装： | MO-153ABT, TSSOP-16 |
| 文件页数： | 18/28页 |
| 文件大小： | 969K |
| 代理商： | AD8349ARE-REEL7 |
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AD8349
BASEBAND DAC INTERFACE
The recommended baseband input swing and bias levels of the
AD8349’s differential baseband inputs allow for direct
connection to most baseband DACs without the need for any
external active components. Typically these DACs have a
differential full-scale output current from 0 mA to 20 mA on
each differential output. These currents can be easily converted
to voltages using ground-referenced shunt resistors. Most
baseband DACs for transmit chains are designed with two
DACs in a single package.
Rev. 0 | Page 18 of 28
AD9777 INTERFACE
The AD977x family of dual DACs is well suited to driving the
baseband inputs of the AD8349. The AD9777 is a dual 16-bit
DAC that can generate either a baseband output or a complex
IF using the device’s complex modulator.
The basic interface between the AD9777’s I
OUT
outputs and the
AD8349’s differential baseband inputs is shown in Figure 51.
The Resistors R1 and R2 set the dc bias level, and R3 sets the
amplitude of the baseband input voltage swing.
OPTIONAL
LOW-PASS
FILTER
0
R1Q
R2Q
R3Q
69
68
16
15
I
OUTB2
I
OUTA2
QBBN
QBBP
73
72
1
2
I
OUTB1
I
OUTA1
IBBN
IBBP
AD9777
AD8349
OPTIONAL
LOW-PASS
FILTER
R1I
R2I
R3I
Figure 51. Basic AD9777 to AD8349 Interface
0.15
0.30
0.45
0.60
0.75
0.90
1.05
1.20
1.35
1.50
D
R3 (
)
10
100
1.10
3
0
Figure 52. Relationship Between R3 in Figure 51 and Peak
Baseband Input Voltage.
BIASING AND FILTERING
A value of 40 on R1 and R2 in Figure 51 will generate the
required 400 mV dc bias. Note that this is independent of the
value of R3. Figure 52 shows the relationship between the value
of R3 and the peak baseband input voltage with the 40
resistors in place. From Figure 52, it can be seen that a value of
240 will provide a peak-to-peak swing of approximately
1.2
V
p-p differential into the AD8349’s baseband inputs.
The closest available resistor values are 40.2 and 240 , and
these values were used in the characterization of the AD8349
when the DAC was used as a signal source.
When using a DAC, low-pass image reject filters are typically
used to eliminate images that are produced by the DAC. They
provide the added benefit of eliminating broadband noise that
might feed into the modulator from the DAC.
Figure 53 shows a single sideband spectrum at 2140 MHz. The
baseband sine and cosine signals come from the digital output
of a Rohde & Schwarz AMIQ arbitrary waveform generator.
These signals drive the AD9777 dual DAC, which in turn drives
the AD8349’s baseband inputs. Note that the AD9777’s complex
modulator is not being used.
Due to offset voltages, internal device mismatch, and imperfect
quadrature over the AD8349’s operating range, the SSB
spectrum has a number of undesirable components such as LO
feedthrough and undesired sideband leakage. When the
AD8349 is driven by a modulated baseband signal, (e.g. 8-PSK,
GMSK, QPSK, or QAM), these nonidealities will manifest
themselves as degraded error vector magnitude (EVM), and
degraded spectral purity.
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
A
SSB = 1.7dBm
LO = –44.5dBm
USB = –52dBc
THIRD HARMONIC = –36.8dBc
0
CENTER 2.14GHz
SPAN 10MHz
Figure 53. AD8349 Single Sideband Spectrum at 2140 MHz
REDUCING UNDESIRED SIDEBAND LEAKAGE
Undesired sideband leakage is the result of phase and amplitude
imbalances between the I and Q channel baseband signals.
Therefore, to reduce the undesired sideband leakage, the
amplitude and phase of the baseband signals have to be
matched at the mixer cores. Because of mismatches in the
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8349AREZ | 功能描述:IC QUADRATURE MOD 700MHZ 16TSSOP RoHS:是 类别:RF/IF 和 RFID >> RF 调制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 功能:调制器 LO 频率:700MHz ~ 2.3GHz RF 频率:700MHz ~ 2.3GHz P1dB:1dBm 底噪:-148dBm/Hz 输出功率:-1dBm 电流 - 电源:46mA 电源电压:2.7 V ~ 3.6 V 测试频率:1.75GHz 封装/外壳:28-WFQFN 裸露焊盘 包装:带卷 (TR) |
| AD8349AREZ-RL7 | 功能描述:IC MOD QUAD 2.7GHZ 16TSSOP RoHS:是 类别:RF/IF 和 RFID >> RF 调制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 功能:调制器 LO 频率:700MHz ~ 2.3GHz RF 频率:700MHz ~ 2.3GHz P1dB:1dBm 底噪:-148dBm/Hz 输出功率:-1dBm 电流 - 电源:46mA 电源电压:2.7 V ~ 3.6 V 测试频率:1.75GHz 封装/外壳:28-WFQFN 裸露焊盘 包装:带卷 (TR) |
| AD8349EVAL | 制造商:Analog Devices 功能描述:IC ((NS)) |
| AD8349-EVAL | 制造商:Analog Devices 功能描述:AD8349 EVALUATION BOARD - Bulk |
| AD8349-EVALZ | 制造商:Analog Devices 功能描述:AD8349 EVALUATION BOARD - Bulk |
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