UHF RFID demodulated frequecy

[tsy85]

Hi everyone,

May I know anyone knows what is the demodulated frequency for UHF Rfid? (which is typically 900Mhz)

Is it few kHz to few MHz? Anyone knows the more accurate answers?

Thanks for your helps!!!

Regards

 

[GVVIN]

Hi tsy85 ,

demodulated frequency for UHF Rfid? (which is typically 900Mhz)

Demodulated frequency means baseband ???

Baseband frequency or bandwidth depends on datarate, modulation and filters.
for example

The LT®5575 is an 800MHz to 2.7GHz direct conversion
quadrature demodulator optimized for high linearity
receiver applications. It is suitable for communications
receivers where an RF signal is directly converted into I
and Q baseband signals with bandwidth up to 490MHz.

Baseband frequency usually we say the highest frequency component. So in the above example 0 to 490 Mhz of frequency.

Regards
GV

 

[tsy85]

Hi GVVIN, thanks for your reply.

Ya what i mean is the message/baseband frequency.

Let say I desire to used a low cost envelope detector to detect the UHF signal, where the detector generally consists of a Schottky diode,and a shunt resistor and capacitor.

So in this case, how am I going to choose the proper value for the R and C?Anyone knows it?

Thanks.

 

[FvM]

The modulation or baseband bandwidth may be different according to the used standard. ISO/IEC 18000-6 (860-960 MHz) specifies bitrates of 10 to 40 kbps.

Basically, the usable bandwidth is constrained by ISM regulations, thus a considerably higher bandwidth is effectively impossible.

 

[GVVIN]

Hi FvM,

Yes I agree with you.

I have a query,

I think the RF bandwidth will be the same as baseband bandwidth bcos after baseband filtering there is no inband filter. only upconversion.
In standards the Transmit mask is specified , so precisely can we tell the BB bandwdth by measuring RF bandwidth???
for RFID 200Khz or 500KHz, as per local regulation.

Regards
GV

 

[FvM]

Yes, sounds plausible. I expect, that a bandwidth shaping would be carried out at the baseband if not already achieved by the properties of the modulating signal.