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PDF EVB71112 Data sheet ( Hoja de datos )
| Número de pieza | EVB71112 | |
| Descripción | 868/915MHz Receiver Evaluation Board Description | |
| Fabricantes | Melexis Microelectronic Systems | |
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EVB71112
868/915MHz Receiver
Evaluation Board Description
Features
! Double-conversion superhet architecture for low high degree of image rejection
! FSK for digital data and FM reception for analog signal transmission
! FSK/FM demodulation with phase-coincidence demodulator
! Low current consumption in active mode and very low standby current
! Switchable LNA gain for improved dynamic range
! RSSI allows signal strength indication and ASK detection
www.DataSheet4U.com
Ordering Information
Part No.
EVB71112-868-FSK-C
EVB71112-868-ASK-C
EVB71112-915-FSK-C
EVB71112-915-ASK-C
Application Examples
! Tire Pressure Monitoring Systems (TPMS)
! Remote Keyless Entry (RKE)
! Wireless access control
! Alarm and security systems
! Garage door openers
! Remote Controls
" Home and building automation
! Low-power telemetry systems
Evaluation Board
General Description
The TH71112 FSK/FM/ASK double-conversion superheterodyne receiver IC is designed for applications in
the European 868 MHz industrial-scientific-medical (ISM) band, according to the EN 300 220
telecommunications standard. It can also be used for any other system with carrier frequencies ranging from
750 MHz to 990 MHz (e.g. for applications to FCC part 15).
39012 71112 01
Rev. 011
Page 1 of 14
EVB Description
June/07
1 page  
EVB71112
868/915MHz Receiver
Evaluation Board Description
By configuring the TH71112 for double conversion and using its internal PLL synthesizer with fixed feedback
divider ratios of N1 = 16 (DIV_16) and N2 = 2 (DIV_2), four types of down-conversion are possible: low-side
injection of LO1 and LO2 (low-low), LO1 low-side and LO2 high-side (low-high), LO1 high-side and LO2
low-side (high-low) or LO1 and LO2 high-side (high-high). The following table summarizes some equations
that are useful to calculate the crystal reference frequency (REF), the first IF (IF1) and the VCO1 or first LO
frequency (LO1), respectively, for a given RF and second IF (IF2).
Injection type
REF
www.DataSheet4U.com LO1
IF1
LO2
IF2
high-high
(RF – IF2)/30
32•REF
LO1 – RF
2•REF
LO2 – IF1
low-low
(RF – IF2)/34
32•REF
RF – LO1
2•REF
IF1 – LO2
high-low
(RF + IF2)/30
32•REF
LO1 – RF
2•REF
IF1 – LO2
low-high
(RF + IF2)/34
32•REF
RF – LO1
2•REF
LO2 – IF1
1.6.1 Selected Frequency Plans
The following table depicts crystal, LO and image signals considering the examples of 868.3 MHz and
915 MHz RF reception at IF2 = 10.7 MHz. The columns in bold depict the selected frequency plans to
receive at 868.3 MHz and 915 MHz, respectively.
Signal type
RF =
868.3
MHz
RF =
868.3
MHz
Injection type high-high low-low
REF / MHz 28.58667 25.22353
LO1 / MHz 914.77333 807.15294
IF1 / MHz 46.47333 61.14706
LO2 / MHz 57.17333 50.44706
RF image/MHz 961.24667 746.00588
IF1 image/MHz 67.87333 39.74706
RF =
868.3
MHz
high-low
29.3
937.6
69.3
58.6
1006.9
47.9
RF =
868.3
MHz
RF =
915
MHz
RF =
915
MHz
RF =
915
MHz
RF =
915
MHz
low-high high-high low-low high-low low-high
25.85294 30.14333 26.59706 30.85667 27.22647
827.29412 964.58667 851.10588 987.41333 871.24706
41.00588 49.58667 63.89412 72.41333 43.75294
51.70588 60.28667 53.19412 61.71333 54.45294
786.28824 1014.17 787.21176 1059.83 827.49412
62.40588 70.98667 42.49412 51.01333 65.15294
1.6.2 Maximum Frequency Coverage
Parameter
Injection type
RF / MHz
REF / MHz
LO1 / MHz
IF1 / MHz
LO2 / MHz
IF2/ MHz
fmin
high-low
739.3
25.0
800
60.7
50.0
10.7
fmax
low-low
998.825
29.0625
930
68.825
58.125
10.7
The selection of the reference crystal
frequency is based on some assumptions. As
for example: the first IF and the image
frequencies should not be in a radio band
where strong interfering signals might occur
(because they could represent parasitic
receiving signals), the LO1 signal should be in
the range of 800 MHz to 930 MHz (because
this is the optimum frequency range of the
VCO1). Furthermore the first IF should be as
high as possible to achieve highest RF image
rejection.
39012 71112 01
Rev. 011
Page 5 of 14
EVB Description
June/07
5 Page 
EVB71112
868/915MHz Receiver
Evaluation Board Description
2.2.3 Component Arrangement Top Side for ASK Reception
www.DataSheet4U.com
Board size is 42.7mm x 37.5mm
Melexis
11
C16
RF_input
XTAL
C17
R1
L1
IN_LNA
EVB711XX_4
0Ω
CB3
24 17
25 16
CB2
TH71112
L2
32
1
89
CB1
CB5
C7
L3 C8
CB8
C10
VCC
39012 71112 01
Rev. 011
Page 11 of 14
EVB Description
June/07
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet EVB71112.PDF ] | |
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