EVB71112 Melexis Company, EVB71112 Datasheet - Page 4

• Manufacturer Part Number: EVB71112
• Description: Evaluation Board For Th71112
• Manufacturer: Melexis Company

1.3 Block Diagram
1.4 Mode Configurations
Note: ENRX are pulled down internally
1.5 LNA GAIN Control
Note: hysteresis between gain modes to ensure stability
1.6 Frequency Planning
Frequency planning is straightforward for single-conversion applications because there is only one IF that
can be chosen, and then the only possible choice is low-side or high-side injection of the LO signal (which is
now the one and only LO signal in the receiver).
The receiver’s double-conversion architecture requires careful frequency planning. Besides the desired RF
input signal, there are a number of spurious signals that may cause an undesired response at the output.
Among them are the image of the RF signal (that must be suppressed by the RF front-end filter), spurious
signals injected to the first IF (IF1) and their images which could be mixed down to the same second IF (IF2)
as the desired RF signal (they must be suppressed by the LC filter at IF1 and/or by low-crosstalk design).
39012 71112 01
Rev. 012
V
< 0.8 V
> 1.4 V
IN_LNA
31
ENRX
GAIN_LNA
32
1
0
1
LNA
30
2
3
4
VCO1
DIV16
MIX1
5
LO1
HIGH GAIN
RX standby
LOW GAIN
RX active
29
6
Mode
Mode
LF
DIV2
IF1
Fig. 1:
7
CP
MIX2
8
PFD
LO2
TH71112 block diagram
9
Page 4 of 14
IF2
10
26
RO
RO
11
12
25
13
27
Evaluation Board Description
IFA
21
28
LNA set to high gain
LNA set to low gain
BIAS
14
Description
Description
RX disabled
RX enable
15
868/915MHz Receiver
22
MIX3
16
EVB71112
17
EVB Description
OA
OUT_OA
OUTN
OUTP
OAN
OAP
23
24
20
19
18
April/08