CMX994 vs ADF7021 and RDA1846
CMX994 comparison against ADF7021 and RDA1846
1 CMX994
PERFORMANCE
The CMX994 is designed to meet the requirements of professional radio systems such as TETRA, APCO P25 and DMR. These radio systems have specifications applicable to the receiver performance which may not be mandated for spectrum licensing but are demanded by customers.
Today many business radio products are adopting levels of receiver performance that would previously have been considered consumer grade. Such solutions are generally lower current consumption and command a lower price.
The key receiver performance parameters are:
?Sensitivity
?Intermodultion
?Blocking
?Spurious Response Rejection
?Adjacent channel rejection
Of these parameters intermodulation is the one that has the most variation between different performance tiers and has the biggest impact on cost / current consumption.
The CMX994 design meets the requirements of professional PMR designs providing performance in excess of ‘single chip’ radio solutions like ADF7021 and RDA1846. Comparisons are summarised in
Table 1.
Parameter CMX994
(Measured)
ADF7021 RDA1846
Current consumption 66 / 56 mA
(Note 1)
22 mA 55 mA
LNA Noise Figure 2 dB LNA IIP3 4 dBm Mixer NF 14.5 dB Mixer IIP3 11 dBm These figures are not specified separately for ADF7021 / RDA1846, see system
performance figures.
Mixer IIP2 79 dB N/A Not specified System IIP3 -2.5 dBm -24 dBm -6 dBm (Datasheet)
-23 dBm (note 2) System NF 4 dB 3 dB (note 3) Blocking at 1 MHz > 90 dB 77 dB 83 dB
Spurious response rejection
>75 dB
No image in direct
conversion.
29 / 50 dB
(note 4)
Sensitivity (RC4-
FSK), 4800 bit/s
(0.1% BER)
-119 dBm -109 dBm
Notes:
1.56 mA in ‘Low Power’ Mode.
2.Measured on Arex AT-500 radio which includes an external LNA.
3.RDA1846 quotes a 12 dB SINAD sensitivity of -124 dBm, which is achieved on the
Aex AT-500 however that device uses an external LNA.
4.29 dB uncalibrated, 50 dB calibrated
Table 1 – Comparative performance
Key points to note:
?CMX994 is designed for professional performance offering intermodulation performance compatible with TETRA, APCO P25, DMR, TIA-603 etc, This is not possible with current single chip solutions like ADF7021 and RDA1846.
?CMX994 is a RF only solution and it can be used with the most appropriate baseband solution for a particular application. (e.g. support a wide range of modulation from analogue FM or AM to QAM, multi-carrier etc.)
?CMX994 + CMX7164 (CML high speed wireless data baseband processor) data performance is significantly better then ADF7021.
?CMX994 was primarily designed for data transmission but operation with analogue FM has also been successfully demonstrated.
?ADF7021 would fail professional spurious response rejection tests due to poor image response (CMX994 has inherently very few spurious response due to direct conversion architecture).
Advantages of CMX994 over ADF7021 and RDA1846
?Better intermodulation performance
?Better spurious response rejection
?Better blocking performance;
?More flexibility in choice of modulations
?Supports external PLL/VCO operation where optimum phase noise is required
?Similar or better receiver sensitivity
?Allows use of external LNA for optimum sensitivity while maintaining reasonable intermodulation
?Supports configurable signal bandwidths 6.25 kHz (or less) upto 2 MHz;
?Has similar (very low) external component count;
?Allows flexible digital interfacing levels;
?Meets ‘professional’ radio performance requirements for systems like TETRA, APCO P25, DMR etc.
To achieve these benefits the CMX994 consumes a little more power than ADF7021 and RDA1846 solutions and is not constrained by a built-in baseband solution.