Totally I can't understand meanings of your questions.
aaron_do wrote on Apr 2nd, 2009, 9:22pm:My question is does the channel-select filter usually have to double as a matched-filter, or do we normally design an additional matched filter after limiting amplification? My thinking is that having an additional matched filter would give better SNR since the limiting amplifier introduces broadband noise. On the other hand, i've seen some designs which do not seem to have the additional matched filter...
It is almost impossible to realize matched filter as analog filter.
aaron_do wrote on Apr 11th, 2009, 1:03am:I guess you pointed me to your other post to illustrate that OQPSK and MSK have similar constellations, right?
No.
They have completely same constellations.
MSK signal also can be generated as OQPSK with Halfsine pulse shaping.
http://www.designers-guide.org/Forum/YaBB.pl?num=1195226387aaron_do wrote on Apr 11th, 2009, 1:03am:My question is, "is this threshold effect SNR determined by the noise bandwidth?".
Right.
aaron_do wrote on Apr 11th, 2009, 1:03am:If so, is it beneficial to filter off the noise in between the mark and space with an additional filter prior to quadrature detection...
I can't understand what you mean.
aaron_do wrote on Apr 11th, 2009, 1:03am:Second question is, "would a DSP based design be more power hungry?"
i.e. after downconversion, have an anti-alising filter followed by ADC and then DSP...
I don't think so.
Again, it is almost impossible to realize practical matched filter as analog filter.
See paper on ZigBee Transceiver which is zero-IF architecture by ADI in ISSCC-2009.
[24.4] "A Highly Integrated Low-Power 2.4GHz Transceiver Using a Direct-Conversion Diversity Receiver in 0.18um CMOS for IEEE802.15.4 WPAN"
G.Retz
1, H.Shanan
1, K.Mulvaney
1, S.O'Mahony
1, M.Chanca
2, P.Crowley
3, C.Billon
1, K.Khan
1, P.Quinlan
11Analog Devices, Cork, Ireland;
2Analog Devices, Valencia, Spain;
3Analog Devices, Limerick, Ireland
"A 0.18um CMOS RF sensor-network transceiver based on the 802.15.4-2.4GHz WPAN standard integrates a radio controller,
a direct-conversion diversity receiver and a transmitter based on direct VCO modulation.
The 5.85mm
2 IC draws 16.8mA from 1.8V in receive mode and 18mA at 3dBm output power.
The receiver achieves 9.5dB NF, -96dBm sensitivity and -18dBm IIP3, with 54dB of IR at +/-5MHz offset."