DC1120A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1120A
40MHZ TO 3.8GHZ RF POWER DETECTOR WITH 75dB DYNAMIC RANGE
LT5538
DESCRIPTION
Demonstration circuit 1120A is a wide dynamic
range RF power detector featuring the LT®5538.
The LT5538 is a 40MHz to 3.8GHz monolithic
logarithmic RF power detector capable of
measuring RF signals from –75dBm to 10dBm.
The RF signal in a decibel scale is precisely
converted into DC voltage on a linear scale.
The wide input dynamic range is achieved using cascaded RF detectors and RF limiters.
Their outputs are summed to generate an accurate linear DC voltage proportional to the input
RF signal in dBm. The output is buffered with a
low impedance driver. The LT5538 delivers superior temperature stabile output (within ±1dB
over full temperature rage) from 40MHz to
3.8GHz.
Demonstration circuit 1120A features broadband input impedance matching optimized for
evaluating the LT5538 at frequencies between
40MHz and 2.7GHz. It can be easily reconfigured for higher operating frequencies up to
3.8GHz or optimized to specific frequencies for
narrow band applications. Refer to the “Application Note” section and the LT5538 data sheet for
details.
Design files for this circuit board are available. Call the LTC factory.
, LT, LTC, and LTM are registered trademarks of Linear Technology
Corp. All other trademarks are the property of their respective owners.
Table 1. Typical Demo Circuit Performance Summary (Vcc = 5V, EN = 5V, TA = 25°C, source impedance = 50 ,
unless otherwise noted. Test circuit shown in Figure 2.)
PARAMETER
RF Input Frequency Range
CONDITION
Standard Demonstration Circuit 1120A, >10dB Return Loss
(Can be re-matched up to 3.8GHz, refer to the “Application Note”
VALUE
40MHz to 2.7GHz
Supply Voltage
3V to 5.25V
Supply Current
29mA
Shutdown Current
EN = Low
1uA
EN = High (On)
> 1V
EN = Low (Off)
< 0.3V
Turn On Time
300ns
Turn Off Time
1us
Output DC voltage
No RF Input Signal Present
350mV
Output Impedance
150
Output Source Current
10mA
Output Sink Current
200uA
Rise Time
0.5V to 1.6V, 10% to 90%, fRF = 880MHz
100ns
Fall Time
1.6V to 0.5V, 10% to 90%, fRF = 880MHz
180ns
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1120A
40MHZ TO 3.8GHZ RF POWER DETECTOR WITH 75dB DYNAMIC RANGE
Table 2. Typical Demo Circuit Performance Summary, continued (VCC = 5V, EN = 5V, TA = 25°C, source impedance = 50, unless otherwise noted. Test circuit shown in Figure 2.)
PARAMETER
CONDITION
VALUE
±1dB Linearity Error
76dB
fRF = 40MHz
RF Input Power Range
Linear Dynamic Range
-75dBm to 10dBm
Output Slope
19.9mV/dB
Logarithmic Intercept
-87.5dBm
Sensitivity
-72dBm
fRF = 450MHz
RF Input Power Range
Linear Dynamic Range
-75dBm to 10dBm
±1dB Linearity Error
75dB
Output Slope
19.6mV/dB
Logarithmic Intercept
-87.3dBm
Sensitivity
-71.5dBm
fRF = 880MHz
RF Input Power Range
Linear Dynamic Range
-75dBm to 10dBm
±1dB Linearity Error
75dB
Output Slope
19.0mV/dB
Logarithmic Intercept
-88.8dBm
Sensitivity
-71.5dBm
fRF = 2140MHz
RF Input Power Range
Linear Dynamic Range
-72dBm to 10dBm
±1dB Linearity Error
70dB
Output Slope
17.7mV/dB
Logarithmic Intercept
-89.0dBm
Sensitivity
-69.0dBm
fRF = 2700MHz
RF Input Power Range
Linear Dynamic Range
-72dBm to 10dBm
±1dB Linearity Error
65dB
Output Slope
17.6mV/dB
Logarithmic Intercept
-87.5dBm
Sensitivity
-69.5dBm
fRF = 3600MHz
RF Input Power Range
Linear Dynamic Range
-65dBm to 10dBm
±1dB Linearity Error
57dB
Output Slope
18mV/dB
Logarithmic Intercept
-81.4dBm
Sensitivity
-63dBm
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1120A
40MHZ TO 3.8GHZ RF POWER DETECTOR WITH 75dB DYNAMIC RANGE
NOTE:
1. Depending on the operating frequency, C8
ABSOLUTE MAXIMUM RATINGS
Power Supply Voltage ................................5.5V
Enable Voltage ...................... -0.3V, VCC + 0.3V
RF Input Power ...................................... 15dBm
Operating Ambient Temperature-40°C to +85°C
Storage Temperature Range .. -65°C to +125°C
Maximum Junction Temperature ............. 150°C
RF INPUT INTERFACE
The standard demonstration circuit 1120A is
configured for broadband RF input to ease evaluations at various frequencies. However, it can
be easily reconfigured for narrowband operations, which offers slightly improved sensitivity
and some frequency selectivity. Examples of
some common RF input frequency matching are
presented in Table 3. Please refer to circuit
schematic in Figure 4. Their return loss plots
are shown in Figure 1 and Figure 2.
can be either a capacitor or an inductor. Similarly, L1 can also be a capacitor, an inductor,
or a zero-ohm jumper.
2. The LT5538 IC’s IN- pin (Pin 3) is coupled to
ground via an internal 20pF capacitor. At
low input frequencies, a large value external
ac-decoupling capacitor (C5) should be
used. At high frequencies, the internal capacitor is sufficient, and C5 can be left
open.
0
2
-5
-10
INPUT RETURN LOSS (dB)
APPLICATION NOTE
1
-15
-20
-25
-30
-35
Table 3. RF Input Matching Component Values
C8
(*1)
L1
(*1)
402700
1pF
401300
-
600
27nH
-40
C4
C5
(*2)
10dB RL
Range
(MHz)
Trac
e
No.
1.5n
H
1nF
1nF
0.3-2700
1
0
1nF
1nF
0.3-1300
2
27pF
100p
F
100p
F
300-1300
100p
F
600-1450
4
3
900
12nH
12pF
1900
2.7n
H
3.3p
F
22pF
-
17002100
5
2140
2.2n
H
2.7p
F
22pF
-
19002300
6
2600
1.5n
H
1.5p
F
22pF
-
25002800
7
0.7p
F
3.3p
F
22pF
33003900
8
-
500
1000
1500 2000 2500
FREQUENCY (MHz)
3000
3500
4000
Figure 1. RF Input Return Loss for Wideband Matching
0
-5
-10
100p
F
3600
0
INPUT RETURN LOSS (dB)
RF
Input
(MHz)
-15
7
-20
-25
6
-30
-35
3
-40
0
500
4
1000
5
1500 2000 2500
FREQUENCY (MHz)
8
3000
3500
4000
Figure 2. RF Input Return Loss for Narrowband Matching
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1120A
40MHZ TO 3.8GHZ RF POWER DETECTOR WITH 75dB DYNAMIC RANGE
QUICK START PROCEDURE
Demonstration circuit 1120A is easy to set up to
evaluate the performance of the LT5538. Refer
to Figure 3 for proper measurement equipment
setup and follow the procedure below:
5. Connect RF signal generator output to demo
NOTE: Care should be taken to never exceed
VCC pin to EN pin. Now the detector is enabled (on) and is ready for measurement.
absolute maximum input ratings. Never apply
DC power to EN pin before VCC pin.
1. Connect DC power supply negative (-) output
to demo board GND pin.
6. Using a jumper cable, connect demo board
7. Apply an RF input signal and measure output
DC voltage.
8. The linearity dynamic range is defined as the
2. Connect DC power supply positive (+) output
(3V to 5.25V) to demo board VCC pin.
3. Connect voltmeter negative (-) lead to demo
board GND pin.
4. Connect voltmeter positive (+) lead to the
demo board OUT pin.
board RFin port (SMA connector J1) via coaxial cable.
range over which the linearity error is within
±1dB. The linearity error is calculated by the
difference between the incremental slope of
the output and the average output slope from
-50dBm to -20dBm.
9. Sensitivity is defined as the minimum input
power required for the linearity error to be
within 3dB of the ideal log-linear transfer
curve.
Figure 3. Proper Measurement Equipment Setup
Figure 4. Demonstration Circuit Schematic
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1120A
40MHZ TO 3.8GHZ RF POWER DETECTOR WITH 75dB DYNAMIC RANGE
5
Similar pages