<P>It looks like you might have an old version of the datasheet. The newest, revision 1.2, is from june 2004, and can be downloaded from our web-page.</P><P>The impedance at the antenna is 100 + j 175 ohms.</P><P>ANT1 and ANT2 are bidirectional. The nRF24E1 is both transmitter and receiver.</P><P>The matching network is a balun which converts the RF-signal from differential to single ended. The new matching network is a bit different from the one I think you are using, and it has a better suppression of harmonic spurs. The shunt capacitor is no longer used.</P><P>If you are going to use a 50 ohm antenna (most antennas are 50 ohms), you just use the matching network we provide.</P><P>
I hope this answers your questions.</P>[br]<p align=right><font color=red>+5 RD币</font></p>
<P>
> I have downloaded the newest datasheet from Nordic web site.
>
>
>
> The matching network is different between the schematic in datasheet
> and hand free demo.(see attachment, fig.1 and fig.2)
>
>
>
> My questions are:
>
>
>
> 1. Why the two schematics are different? Datasheet is a 50ohm antenna
> while hand free is not?</P><P>The schematic in figure 1 is older than the one in figure 2. The reason for the extra components are to supress spurious from the VCO on RX mode. In some cases the spurious will be too high when the fig.1 version is used. The performance other than this should be equal.</P><P>
> 2. Would you please tell me the usage of the C11 and L4 in the
datasheet?
> Band stop filter?</P><P>Yes. To supress VCO spurious.</P><P>> 3. L1 is a shunt inductor, while the C9 and C10 are shunt capacitors. L
and
> C are parallel. The effect of L and C are opposite. Why place them together?
> Band pass filter?</P><P>No. L1 feed both inputs with power to the PA. C9 and C10 will supress 2nd and 3rd harmomics.</P><P>
> 4. I use Smith chart tool to simulate the impedance transformation, as
> Fig.3. L1 from point 1 to point 2, C10 from point 2 to point 3, L3
> from point
3
> to 4, C12 from 4 to 5. It is incredible! For the point 5 lay on the
> circle
not
> the center! Can you explain how you design the whole matching network? </P><P>If you want to simulate this, you should also allow for strai capasitance in the layout, complete models for all components and so. We use a quite complicated ADS model to simulate the performance of the network. This allows for board thiknes, distance to ground plane etc. So since you use only component values, you will get completely wrong results. The stray capasitances are in the pF areas, the same values as some of the caps. So the impact is great.</P><P>> 5. Like Fig.4, just one series capacitor can transform (50+j87.5) to 50!
> And just two series capacitors with same value can transform (100+175)
> to
100.
> Why do you use so many components? </P><P>All components are needed to satisfy regulations with regards to spurious and harmonic rejection.</P><P>> 6. Do you have the original design file for the match network?</P><P>No, I'm sorry. It's a higly complicated Agilent ADS system we are using.</P><P>I suggest you just use the values and components we are recommending to avoid too many problems in the design.
</P>
IP卡
狗仔卡
发表于 2005-12-14 20:44:00
提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
显身卡