AD6140ARSRL AD [Analog Devices], AD6140ARSRL Datasheet - Page 6

• Manufacturer Part Number: AD6140ARSRL
• Description: Bandpass IF Subsystem
• Manufacturer: AD [Analog Devices]

AD6140
A
(1 bit in this case) in order to “shape” the spectrum of quantiza-
tion noise. Using this technique, we can shape noise away from
an arbitrary passband, within which we can place a modulated
signal. A
zation noise, which can be digitally removed with a filter, known
as a decimation filter. Applying this technique to bandpass
signals results in an analog-to-digital converter suitable for
converting the IF signals in a digital radio.
The output of the AD6140’s
9. As can be seen, the noise is shaped away from a narrow band-
width, within which we place a signal (a sine wave in this case)
resulting in a narrowband, high dynamic range digital represen-
tation of the analog input.
Figure 7. Supply Current vs. Power Supply Voltage
MODULATION
modulator uses feedback around a low noise quantizer
5.2
4.8
4.4
5.0
4.6
modulator reproduces the input, but adds quanti-
2.5
T
A
= +25 C
AGC_TC_SELECT
AGC_CAPACITOR
POWER SUPPLY VOLTAGE – Volts
LNA_FORCE
LNA_SENSE
2.6
0.1 F
IF_INPUT
modulator is shown in Figure
2.7
AMPLIFIER
LNA BIAS
PREAMPLIFIER
2.8
AVDD AGND DGND DVDD POWER_DOWN
LO_IN+
Figure 8. Functional Block Diagram
MIXER
2.9
DETECTOR
CIRCUIT
LO_IN–
AGC
MIXER POST
AMPLIFIER
–6–
BIAS SYSTEM
PRODUCT OVERVIEW
The AD6140 is a bandpass
IC for dual conversion receivers requiring a high dynamic range
and multiple filter bandwidths. It consists of a variable gain, low
noise preamplifier, mixer, automatic gain control (AGC) detec-
tor, bandpass
and an auxiliary amplifier for use in biasing a discrete LNA.
The low noise preamplifier accepts a first IF input at 49.6 MHz
from 16.4 V p-p to 63.2 mV p-p. It provides a variable gain
from 12 dB to 25 dB.
The mixer accepts an LO frequency of 49.792 MHz or
49.408 MHz, resulting in an IF frequency of 192 kHz. The LO
level should be 200 mV p-p differential. It is ac-coupled to the
AD6140. The mixer operates in the linear region, hence the
gain of the mixer is a function of the LO level. As a result, spe-
cial care must be taken to ensure that the LO level is 200 mV p-p,
MODULATOR
R
–100
–150
–50
INT
AD6140
0
LEVEL-SHIFTER
0
Figure 9. Output Spectrum of AD6140
ECL-TO-CMOS
BIAS_RESISTOR
39k
500
modulator, an ECL to CMOS level translator
1000
BUFFER_VDD
CLK_IN+
CLK_IN–
BUFFER_GND
VOLTAGE_REFERENCE_IN
FREQUENCY – kHz
_DATA_OUT
_CLOCK_OUT
RESPONSE FROM 0kHz TO (f
1500
analog-to-digital converter IF
2000
2500
3000
S
/2)kHz
3500
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