EVB71111
868/915MHz Receiver
Evaluation Board Description
1.3 Block Diagram
1
2
3
4
5
6
7
8
9
10
11 12
13
21
14
15
16
MIX1
OUTP
23
OUTN
MIX3
IN_LNA
31
IF
IF
LNA
MIX2
IFA
24
LO
OAP
20
OAN
19
OA
PFD
DIV_32
OUT_OA
RO
18
BIAS
VCO1
CP
32
30
29 LF
26 RO
25
28
27
22
17
Fig. 1: TH71111 block diagram
1.4 Mode Configurations
ENRX
Mode
Description
RX disabled
RX enable
0
1
RX standby
RX active
Note: ENRX are pulled down internally
1.5 LNA GAIN Control
VGAIN_LNA
< 0.8 V
> 1.4 V
Mode
Description
HIGH GAIN
LOW GAIN
LNA set to high gain
LNA set to low gain
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 single-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 is the image of the RF signal that must be suppressed by the RF front-end filter.
39012 71111 01
Rev. 011
Page 4 of 14
EVB Description
June/07
MELEXIS [ Melexis Microelectronic Systems ]
