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参数资料
| 型号： | MAX2740ECM |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 通信及网络 |
| 英文描述： | Integrated GPS Receiver and Synthesizer |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PQFP48 |
| 封装： | 7 X 7 MM, 1 MM HEIGHT, EXPOSED PAD, TQFP-48 |
| 文件页数： | 6/8页 |
| 文件大小： | 189K |
| 代理商： | MAX2740ECM |
M
Applications Information
Figure 1 shows a typical application diagram in which
the MAX2740 should be used. The RF front end con-
sists of the antenna interface, MAX2740, two control
loops (one for the AGC, the other for the synthesizer),
and appropriate external components, including filters
for image rejection and channel selectivity, operational
amplifiers for the control loops, and resonator and tun-
ing network for the VCO.
Only the antenna input, an external 20MHz frequency
reference, and an AGC input from the accompanying
DSP are required. A differential output is provided from
the MAX2740, which can be applied either to the exter-
nal analog-to-digital conversion circuitry or directly to
the companion DSP.
Low-Noise Amplifier
This subcircuit requires input and output matching. The
input match is typically a series capacitor, and the out-
put is typically a shunt inductor to V
CC
and a series
capacitor.
RF Mixer
The RF input is matched externally. The match consists
of a series inductor and shunt capacitor. The source
impedance for this circuit is the single-ended, 50
RF
SAW used as an image reject filter. A second RF input
is brought out to a separate pin for AC grounding. This
ensures low ground impedance over a wide band and
minimizes amplification of any noise at the IF frequency
generated within the mixer structure.
The IF output is delivered through low-output-imped-
ance emitter followers and is suitable for directly driving
a 135MHz IF SAW with a typical impedance of 400
.
The deliberate mismatch keeps the group delay distor-
tion of the SAW within an acceptable level.
IF Mixer
The IF downconverter receives the differential 1st IF of
135.42MHz from the SAW and delivers a differential
2nd IF signal at 15.42MHz. The circuit has been opti-
mized to deliver a high level of conversion gain with
adequate IIP3 and noise figure. The circuit is terminat-
ed on the input with a differential 100
to establish the
correct embedding impedance for the IF SAW. The
emitter follower outputs drive directly into a high-imped-
ance, differential, three-pole lowpass discrete lumped
element filter.
Variable-Gain Amplifier
This circuit compensates for receiver gain variation and
unknown antenna cable losses. Under these condi-
tions, the receiver will exhibit minimum implementation
loss. The circuit has a useful gain control range of
greater than 50dB, with a maximum gain level of 16dB.
Fixed-Gain Amplifier
This circuit has been designed to deliver 40dB of differ-
ential gain at the 2nd IF frequency of 15.42MHz. The
differential inputs are received from the VGA outputs
through a balanced lowpass filter circuit. The circuit
’
s
differential output is designed to drive a digitizer with a
typical load impedance of 4k
differential.
Voltage-Controlled Oscillator
The core of the L-band VCO is based on a common-
collector Colpitts topology. This circuit has been opti-
mized for low thermal noise and high signal swing with-
out asymmetrical clipping. The circuit is designed for
use with a lumped inductor for low-cost applications.
The self-resonance should be above 1440MHz so that
parallel varactor tuning and the VCO internal capaci-
tance produces resonance at 1440MHz.
Synthesizer
The digital prescaler accepts the output from the oscil-
lator
’
s differential digital buffer and divides the frequen-
cy from 1.44GHz to 120MHz for the 2nd LO, 20MHz for
the phase-frequency detector, and 90MHz for the
GLONASS reference output. Divider blocks are
arranged to ensure that the 2nd LO drive has minimum
duty cycle distortion. A simple output buffer is used to
deliver the GLONASS reference signal to a typical
external load impedance of 500
.
The phase-frequency detector is a classical dual flip-
flop with ANDed feedback to a reset function. UP and
DOWN outputs are provided through emitter follower
buffers. These outputs deliver pulse-width-modulated
signals that in phase-acquisition mode give a phase
detector range of ±2
π
. With the PLL not in lock, either
the UP or DOWN output will be active and drive the
VCO frequency toward the reference frequency. The
phase detector outputs feed directly into an active,
lead-lag differential loop filter.
Integrated GPS Receiver and Synthesizer
6
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX2740ECM-T | 制造商:Maxim Integrated Products 功能描述:INTEGRATED GPS RECEIVER AND SYNTHESIZER 48 PINS TQFP PKG - Tape and Reel |
| MAX2741AETI+ | 功能描述:射频接收器 Integrated L1-Band GPS Receiver RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel |
| MAX2741AETI+T | 功能描述:射频接收器 Integrated L1-Band GPS Receiver RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel |
| MAX2741AEVKIT | 功能描述:GPS开发工具 MAX2741A Eval Kit RoHS:否 制造商:STMicroelectronics 产品:Evaluation Boards 工具用于评估:IT600, STM32F20x 频率:1.575 GHz 工作电源电压:1.8 V 接口类型:Wireless |
| MAX2741ETI | 功能描述:射频接收器 RoHS:否 制造商:Skyworks Solutions, Inc. 类型:GPS Receiver 封装 / 箱体:QFN-24 工作频率:4.092 MHz 工作电源电压:3.3 V 封装:Reel |
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