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Re: Ideal low pass Filter
Almost yes, but it's a bit of a cheat. Go to the 'Filters-Bandpass' palette and select
a SAW filter. This is of the high-loss linear phase type.. but ADS lets you set the
loss to whatever you like. Set the passband such that the lower edge of the filter
is at 0Hz or...
high division
You'd be surprised.. best phase noise and spurious is often achieved using phase
detector outputs into a low noise op-amp (eg. OP37, THS4031, AD829, AD797 etc).
This can be for a few reasons, but amongst them are avoiding things like CP
mismatch (this can be a big contributor...
rf pcb trace to rf pin
Not easily because loss in FR4 microstrip depends upon :
- dielectric loss (tan delta)
- conductivity loss (loss due to conductivity of copper)
- radiation losses
- skin depth
Since the conductivity loss is significant and depends on the width of the line
which...
suppressing fractional n spurs
Yes, using a fractional PLL you can easily get 125kHz steps from 8.75MHz. In fact the higher the Fcomp the better as fractional spurious can be a potential problem at output frequencies that are close to multiples of Fcomp (and can be a problem elsewhere too ...
90degree coupler
You could try the following US patent : 3514722
US Patent search : https://patft.uspto.gov/netahtml/PTO/srchnum.htm
US Patent to PDF : https://www.pat2pdf.org/
Describes a transformer based wideband quadrature coupler. Note I haven't tried building this circuit myself.. Good...
Xinxin,
400kHz spec :
At power levels below about +30dBm , the spec limit to use is -36dBm
(the CMU200 knows this and adjusts the limit automatically, I am not
sure the Agilent does this)
600kHz spec :
the spec limit is 60dBc
Measurement Setup (from spec) :
"zero frequency scan, filter...
pcl gsm dcs
Check the DCS modulation spectrum spec carefully, at low power levels the 'dBc' spec may no longer be necessary : only the 'dBm' specification is applicable.
If performance is still outside specification then one possibility could be power control loop gain at low power levels. If...
Re: PLL for WCDMA
Yes it is. I have designed integer-n PLLs for GSM handsets with
25kHz loop bandwidth with a 400khz reference. This was sufficient
to meet class 6/10 GPRS settling time requirements. Typical settling
time was <200us. Fractional-N is not necessary for GSM.
Re: PLL for WCDMA
Yes. For example Nokia WCDMA phones on the market use 2 integer-N
PLLs. One for RX and one for TX frequencies.
Siemens and Nokia (perhaps others) run the GSM PLL at twice the wanted
frequency. This allows easy generation of quadrature signals for the
IQ modulators...
My preference is @DS because it can do so much IF you have
deep enough pockets to pay for the licences !
- System level simulations can be done
- All sorts of time/frequency RF sims can be done
- DSP/digital simulations can be linked to RF simulations (can the others do this ?) if you have...
One possible way to measure a signal spectrum is as follows :
i) Set analyser RBW to required value (100kHz)
ii) Trigger analyser from Vcc line as you suggested
iii) Set analyser to zero-span (time on the x-axis)
iv) Set analyser frequency at desired PSD offset : in specification
mentioned this...
So an Infineon RFIC and an RFMD PA..
Ok, a few other possibilities :
i) Output of the IQ modulator may not 'like' the input
inpedence of the PA : try an attenuator and/or buffer
between them to see what happens..
ii) Check layout for RF tracks close to supplies/control
lines/reference clock...
Re: Film capacitor
Good response to current transients (during rapid charge/discharge
cycles when PLL is locking). Compare PLL settling times if a
X7R capacitor is used in a loop filter : slower settling than with
film..
Capacitance vs. Temperature change is small like C0G.
Piezo-electric...
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