參數(shù)資料
型號(hào)： AD9853-45PCB
廠商： Analog Devices, Inc.
英文描述： Programmable Digital OPSK/16-QAM Modulator
中文描述： 可編程數(shù)字OPSK/16-QAM調(diào)制器
文件頁(yè)數(shù)： 27/31頁(yè)
文件大?。?/td> 335K
代理商： AD9853-45PCB
AD9853
–27–
REV. C
REFERENCE CLOCK MULTIPLIER
Due to the fact that the AD9853 is a DDS-based modulator, a
relatively high frequency system clock is required. For DDS
applications the carrier is typically limited to about 40% of
f
CLOCK
. For a 65 MHz carrier, the system clock required is
above 150 MHz. To avoid the cost associated with these high
frequency references, and the aggravating noise coupling issues
associated with operating a high frequency clock on a PC board,
the AD9853 provides an on-chip 6
×
clock multiplier. With the
6
×
on-chip multiplier, the input reference clock required for the
AD9853 can be kept in the 20 MHz to 30 MHz range, which
results in cost and system implementation savings. The 6
×
REFCLK multiplier maintains clock integrity as evidenced by
the AD9853’s system phase noise characteristics of –100 dBc/Hz
and virtually no clock related spurious in the output spectrum.
External loop filter components consisting of a series resistor
(1.3 k
) and capacitor (0.01
μ
F) provide the compensation
zero for the 6
×
REFCLK PLL loop. The overall loop perfor-
mance has been optimized for these component values.
Table VI. Derivation of Currently Transmitted Symbol
Quadrant
Current
Input
Bits
I Q
MSBs of
Previously
Transmitted
Symbol
MSBs for
Currently
Transmitted
Symbol
Quadrant
Phase
Change
0
°
0
°
0
°
0
°
90
°
90
°
90
°
90
°
180
°
180
°
180
°
180
°
270
°
270
°
270
°
270
°
00
00
00
00
01
01
01
01
11
11
11
11
10
10
10
10
11
01
00
10
11
01
00
10
11
01
00
10
11
01
00
10
11
01
00
10
01
00
10
11
00
10
11
01
10
11
01
00
Note: This table applies to both DQPSK and D16-QAM formats.
In DQPSK a symbol is comprised of two bits that are denoted
as “ I(1) Q(1).” In this case, I(1) and Q(1) are the MSBs and
the table can be interpreted directly. In D16-QAM a symbol is
defined as comprised of four bits denoted as “I(1) Q(1) I(0) Q(0).”
I(1), Q(1) are the MSBs and I(0), Q(0) are the LSBs. As indi-
cated in the table, only the MSBs I(1) and Q(1) are altered as a
function of the differential coding; I(0) and Q(0) are not altered.
DEVICE THERMAL CONSIDERATIONS
The AD9853 is specified to operate at an ambient temperature
of up to +85
°
C. The maximum junction temperature (T
J
) is
specified at +150
°
C, which provides a worst case junction-to-air
differential of +65
°
C. Thus, with the specified
θ
JA
of +36
°
C/W,
a maximum device dissipation of 1.8 W is achievable under the
worst case conditions. It is important to understand that a sig-
nificant portion of the heat generated by the device is trans-
ferred to the environment via the package leads. The specified
θ
JA
value assumes that the device is soldered to a multilayer
printed circuit board (PCB) with the device power and ground
pins connected directly to power and ground planes of the PCB.
The amount of power internally generated by the device is pri-
marily dependent on four factors:
Power Supply Voltage
System Clock Rate
Input Data Rate
T
X
ENABLE Duty Cycle (assuming the device is operated in
the burst data mode)
The power generated by the device increases with an increase in
any one of the four factors. It turns out that the contribution of
generated power due to the system clock rate, input data rate
and T
X
ENABLE duty cycle may be ignored at power supply
voltages of less than 4 V (as the total power generated by the
device will not exceed 1.8 W). However, for supply voltages
greater than 4 V, operation at +85
°
C ambient temperature will
require a tradeoff among the other three factors; i.e., a reduced
system clock rate, a reduced data rate, a reduced T
X
ENABLE
duty cycle, or some combination of the three. It should be men-
tioned, that operation at a power supply voltage of 4 V yields the
same level of performance as specified at 5 V operation. For
example, the user may still take advantage of the 165 MHz
maximum system clock rate specified for 5 V operation.
V
DD
I
OUT
I
OUTB
DIGITAL
OUT
V
DD
(b)
V
DD
DIGITAL
IN
(a)
(c)
Figure 38. Equivalent I/O Circuits
AD9853-xxPCB EVALUATION BOARD
Two versions of evaluation boards are available for the AD9853
digital QPSK/16-QAM modulator: the AD9853-45PCB and
the AD9853-65PCB. The –45 contains a 45 MHz low-pass
filter to support a 5 MHz–42 MHz output bandwidth and the
–65 has a 65 MHz low-pass filter to support a 5 MHz–65 MHz
output bandwidth.
Both versions of the evaluation board contain the AD9853
device, a REFCLOCK oscillator, a seventh order elliptic low-
pass filter of the designated frequency, an AD8320 program-
mable cable driver amplifier, operating software for Windows
3.1 or Windows 95, and a booklet of complete operating in-
structions and performance graphs. The evaluation board pro-
vides an optimal environment for menu-driven programming of
the devices and analysis of output spectral performance.
Part Number
On-Board Low-Pass Filter
AD9853-45PCB
AD9853-65PCB
45 MHz
65 MHz
Windows is a registered trademark of Microsoft, Corporation.
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AD9853-65PCB 制造商:AD 制造商全稱:Analog Devices 功能描述:Programmable Digital OPSK/16-QAM Modulator
AD9853AS 制造商:Analog Devices 功能描述: 制造商:Rochester Electronics LLC 功能描述:- Bulk
AD9854 制造商:AD 制造商全稱:Analog Devices 功能描述:CMOS 300 MHz Quadrature Complete-DDS
AD9854/PCB 制造商:Analog Devices 功能描述:Evaluation Board For IC Digital Synthesizer Single 制造商:Analog Devices 功能描述:Direct Digital Synthesizer IC (DDS)
AD9854/PCBZ 功能描述:BOARD EVAL FOR AD9854 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評(píng)估演示板和套件 系列:AgileRF™ 標(biāo)準(zhǔn)包裝:1 系列:PCI Express® (PCIe) 主要目的:接口，收發(fā)器，PCI Express 嵌入式:- 已用 IC / 零件:DS80PCI800 主要屬性:- 次要屬性:- 已供物品:板
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