CMX994 Datasheet, PDF (36/61 Pages) CML Microcircuits – Local Oscillator

Direct Conversion Receivers
CMX994/CMX994A/CMX994E
8
8.1
8.1.1
Application Notes
Typical Receiver Performance
System Performance
This information is intended as a general guide of what can be expected from a CMX994/CMX994A/CMX994E
receiver design using the on-chip LNA and I/Q down-conversion stages. The measurement circuit uses the
component values given in section 5.2 The results are based on measurements from evaluation of the
CMX994/CMX994A/CMX994E operating at 450MHz (CMX994E in normal mode, not enhanced mode). Results
are also given for Low Power (LP) mode operation, i.e. General Control Register ($11) b4 = ‘1’; see section
7.2.1.
Gain
Noise Figure:
Input Third Order Intercept Point:
Input Second Order Intercept Point:
63dB (62.5dB in LP mode)
4.5dB (also 4.5 dB in LP mode)
-3dBm (-9dBm in LP mode)
62dBm (60dBm in LP mode)
Notes:
Common settings: max gain, max filter bandwidth, freq control bits = 300 to 700MHz, LNA output impedance
= 100, LO at x2 (900MHz, level -10dBm), IM Control Register = 0x3F
Gain is measured from RF input (assumed to be 50 Ohm source /load) to differential voltage measured at
output of I or Q channels.
Second Order Intercept Point is the average of values measured from differential signals on I and Q;
measured at 1MHz offset.
Using the CMX994/CMX994A/CMX994E operating at 448MHz combined with the CMX7164FI-2 modem IC
gives the following typical system performance using 19.2kbps 4-FSK modulation, alpha =0.2, deviation =3kHz
(based on a 25kHz RF channel).
Sensitivity for 1% BER
Blocking
Adjacent channel rejection
Intermodulation
-116dBm (see Figure 17)
>90dB
73dB
65dB
(Measurement methods based on EN 300 113-1).
1.E-01
1.E-02
1.E-03
1.E-04
1.E-05
1.E-06
1.E-07
-117
-116
-115
-114
-113
-112
RF Input Level (dBm)
-111
-110
-109
Figure 17 CMX994 and CMX7164 with FI-2 – Typical 4-FSK Sensitivity (19.2kbps)
 2015 CML Microsystems Plc
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