spectrum due to modulation

[hypear]

could anyone tell me something about spectrum due to modulation in detail?especially about gsm
and what can cause it failure?
thanks

 

[vfone]

Check this topic

 

[hypear]

sdm spetrum due to modulation

thanks for you reply
but there are some difference between mine and xinxin's.
we use zero IF,and use RFMD3100
when pcl=0,low channel and high channel fail at +/-400kHz,but middle channel pass.
i don't know why
need help
thanks

 

[vfone]

spectrum+3 modulator

I think somewhere is a misunderstanding. RF3100 is a CDMA PA.
In CDMA, modulation spectrum is part of the ACPR test, and is measured at +/-885kHz in 800MHz band and at +/-1.25MHz in PCS band.
Give me more details about your configuration.

 

[hypear]

modulation spectrum gsm

i am so sorry.
the pa is rfmd 3110,it's gsm.
we use infineon's 6255 transceiver.
thanks so much

 

[Gemini1706]

gsm spectrum due to modulation

gsm in phase only modulation (GMSK), so PA nonlinearity should not affect the spectrum.. Did you measure spectrum before the PA also? is it clean?

Unless you are biasing the PA into VERY VERY DEEP class C, it should not affect you spectrum. Most likely it is your modulator or baseband processor..

 

[vfone]

spectrum due to modultion, gsm

If you are using RF3110 check the voltage on pin 5 (VREG) to be 2.8V +/-100mV. Also try to put locally a decoupling cap on this pin (0.1uF).
I remember that 6255 has some modulation problems that were fixed by the new 6270. Check with Infineon for this issue

 

[Wilson_yu_chen]

orfs due to modulation

Peroformance degradation could be many reasons for ORFS modulation
1. ORFS within loop bandwidth: Noise within TX Pll, like PFD...
2. ORFS out loop bandwidth: VCO noise
3. Modulator impact, like sideband suppression...
4. Noise coming from Vcc going into TX loop.
5. PA deep saturation or compression region, but failure occurs as wideband(1.8MHz or less)

 

[xinxin]

spectrum due to modulation pa

I think you first check the signals before PA , perhaps it already fail on ORFS , you can tune the capacitors between I & Q signals. it would improve a little on ORFS . wish you good luck.

 

[Wilson_yu_chen]

orfs modulation

xinxin,

What's the background sense of tweak ORFS Modulation by capacitor between
differential Q or I? Would it be different showing on suppression spectrum when
sending all '1' data to RFIC with the change of capacitors value?
Thanks!

 

[eecly]

gsm modulation spectrum

check the modulator like VCO input ot I/Q modulator

 

[lincoln123]

modulation really influences spectrum width