CMX994 Datasheet, PDF (48/61 Pages) CML Microcircuits – Local Oscillator

Direct Conversion Receivers
0
-1
-2
-3
-4
-5
-6
-40
-20
0
20
40
Temperature / deg C
CMX994/CMX994A/CMX994E
0 dBm
-20 dBm
60
80
Figure 29 Typical Tx Output Level (No Divider) vs. Temperature for Varying LO Input Level
8.4 Modem Solutions
The CMX994 supports a wide range of modulations. By way of example, the device can be operated with CML
baseband / modem devices as shown in Table 20. This table is not exhaustive and other combinations are
also possible.
Modulation
4-FSK
4-FSK
4-FSK, 8-FSK, 16-FSK
GMSK/GFSK
4-QAM, 16-QAM,
64-QAM
Pi/4-DQPSK
C4FM / H-CPM
Analogue FM
Standard
dPMR
TS 102 490
TS 102 658
DMR
TS 102 361
General Purpose
General Purpose
General Purpose
TETRA
EN 300 392-2
APCO P25
TIA-603, EN 300 296
EN 300 086
CML Modem IC
CMX7341 (FI-1)
CMX7141 (FI-7)
CMX7341 (FI-2)
CMX7161
CMX7164 (FI-2)
CMX7164 (FI-1)
CMX7163
CMX7164 (FI-4)
CMX7341 (FI-1)
CML Baseband
Interface IC
CMX983
CMX981, CMX983
CMX981, CMX7861,
CMX983
Table 20 Modulation/Modem Combinations
8.5 Zero IF, near-zero IF and low IF I/Q architectures
The CMX994/CMX994A/CMX994E provides a complete receiver signal path including LNA, RF down mixer
stage and baseband amplifiers with filters to down convert the wanted RF signal to I/Q baseband while
supporting high performance in a small total size. This single conversion approach provides many benefits,
e.g. it requires only one LO source, which reduces circuitry and eliminates a source of many spurious
responses and relative to multi-stage architectures such as dual superhet, it eliminates one or more bulky
image rejection filters. The I/Q output format supports a host of modulations, including phase coherent
constant envelope (e.g. CP-FSK) and linear (QAM) ones.
Mixing the wanted signal down to 0Hz (zero IF) by setting mixer LO and wanted RF signal frequencies to be
the same provides a unique benefit, which is that it avoids placing the image of adjacent channel and other
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