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參數(shù)資料
| 型號： | MAX2450CEP |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 衰減器 |
| 英文描述： | 3V, Ultra-Low-Power Quadrature Modulator/Demodulator |
| 中文描述： | 70 MHz - 160 MHz RF/MICROWAVE QUADRAPHASE MODEM |
| 文件頁數(shù)： | 7/8頁 |
| 文件大?。?/td> | 107K |
| 代理商： | MAX2450CEP |
_______________Detailed Desc ription
The following sections describe each of the functional
blocks shown in the Functional Diagram They also refer
to the Typical Application Block Diagram (Figure 1).
Demodulator
The demodulator contains a single-ended-to-differential
converter, two Gilbert-cell multipliers, and two fixed gain
stages. The IF signal should be AC coupled into IF_IN.
Internally, IF_IN is terminated with a 400
resistor to
GND and provides a gain of 14dB. This amplified IF sig-
nal is fed into the I and Q mixers for demodulation. The
multipliers mix the IF signal with the quadrature LO sig-
nals, resulting in baseband I and Q signals. The conver-
sion gain of the multipliers is 15dB. These signals are
further amplified by 21dB by the baseband amplifiers.
The baseband I and Q amplifier chains are DC coupled.
Loc al Osc illator
The local-oscillator section is formed by an emitter-cou-
pled differential pair. Figure 2 shows the equivalent
local-oscillator circuit schematic. An external LC reso-
nant tank determines the oscillation frequency, and the
Q of this resonant tank affects the oscillator phase
noise. The oscillation frequency is twice the IF frequen-
cy, so that the quadrature phase generator can use two
latches to generate precise quadrature signals.
The oscillator may be overdriven by an external source.
The source should be AC coupled into TANK/
TANK
,
and should provide 200mVp-p levels. A choke (typically
2.2μH) is required between TANK and
TANK
. Differ-
ential input impedance at TANK/
TANK
is 10k
. For sin-
gle-ended drive, connect an AC bypass capacitor
(1000pF) from
TANK
to GND, and AC couple TANK to
the source.
Quadrature Phase Generator
The quadrature phase generator uses two latches to
divide the local-oscillator frequency by two, and gener-
ates two precise quadrature signals. Internal limiting
amplifiers shape the signals to approximate square
waves to drive the Gilbert-cell mixers. The inphase sig-
nal (at half the local-oscillator frequency) is further
divided by four for the prescaler output.
Presc aler
The prescaler output, PRE_OUT, is buffered and swings
typically 0.35V
p-p
with a 10k
and 6pF load. It can be
AC-coupled to the input of a frequency synthesizer.
Modulator
The modulator accepts I and Q differential baseband
signals up to 1.35V
p-p
with frequencies up to 15MHz,
and upconverts them to the IF frequency. Since these
inputs are biased internally at around 1.5V, I and Q sig-
nals should be capacitively coupled into these high-
impedance ports (the differential input impedance is
approximately 44k
). The self-bias design yields very
low on-chip offset, resulting in excellent carrier sup-
M
3V, Ultra-Low-Power Quadrature
Modulator/Demodulator
_______________________________________________________________________________________
7
Figure 2. Local-Oscillator Equivalent Circuit
R
L
5k
R
L
5k
Q1
Q3
Q4
TO
QUADRATURE
GENERATOR AND
PRESCALER
Q2
TANK
TANK
LO_V
CC
Figure 3. Modulator Output Level vs. Load Resistance
35
40
45
50
55
60
65
70
75
M
LOAD RESISTANCE (
)
O
200
1k
10k
100k
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX2450CEP+ | 功能描述:調(diào)節(jié)器/解調(diào)器 RoHS:否 制造商:Texas Instruments 封裝 / 箱體:PVQFN-N24 封裝:Reel |
| MAX2450CEP+T | 功能描述:調(diào)節(jié)器/解調(diào)器 RoHS:否 制造商:Texas Instruments 封裝 / 箱體:PVQFN-N24 封裝:Reel |
| MAX2450CEP-T | 功能描述:調(diào)節(jié)器/解調(diào)器 RoHS:否 制造商:Texas Instruments 封裝 / 箱體:PVQFN-N24 封裝:Reel |
| MAX2450CEP-W | 功能描述:調(diào)節(jié)器/解調(diào)器 RoHS:否 制造商:Texas Instruments 封裝 / 箱體:PVQFN-N24 封裝:Reel |
| MAX2450CWP | 功能描述:調(diào)節(jié)器/解調(diào)器 RoHS:否 制造商:Texas Instruments 封裝 / 箱體:PVQFN-N24 封裝:Reel |
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