Interfacing CC1120 with SKY65366 at 434MHz

Hi,

For the discrete values around the CC1120, please follow the recommended values used in the ref design:

The decoupling and filtering around the Skyworks part looks like there are a few components missing as well:

Regards,

   Richard

I got the reply from Richards and I have changed some resistors values. Now I have updated the schematic above. But Richards may guide me more specifically. Like which of the below schematic should I follow? I mean Fig. 20 or Fig. 21?

Secondly, do I need to use VDD2 or only VDD1 will work to power the SKY65366?

Thirdly, I am using proteus for designing the schematic and layout. Can anyone suggest a software tool where I can simulate the 50 Ohm impedance or I don't need to worry about it too much as long as the L and C values are proper?

Hi,

I would follow figure 22 since this reflects the actual values used on their eval board.

Only one VDD supply will be needed for both the transceiver and the PA. We have a similiar design at 915MHz: www.ti.com/.../swrr110

If you are targeting maximum output power from the Skyworks PA, then the VDD supply to the PA might need to be increased from the nominal 3.3V.

For impedance line calculations, the best freeware is from AWR/ National Instruments:

www.awrcorp.com/.../tx-line-transmission-line-calculator

Regards, Richard

Reference to Richard comments above, I am a bit confused. Does it mean R171 = 22 Milliohm?

Secondly, regarding the 50 Ohm impedance line, what if I use the following values on FR-4 substrate? My understanding is that the length of the line does not affect the 50 ohm line impedance. 

You mentioned, "In the schematic: C31 should be 1.8nF, L173: 22nH, R11: 22nH"

I was just confused about R11: 22nH maybe R171 = 22 Ohm or L11: 22nH.

Sorry about writing milliohm instead of ohm in my previous post.

Is it a good idea to fabricate on FR-4 or I must fabricate on Alumina sheet? I have contacted few local PCB fabricator and they say they only fabricate on FR4 only.

Because for FR-4 the track width of 1.5mm is too much as these tracks would end on 0.5mm pitch IC. Also, the 0.794mm substrate thickness is too small and the developed design will not be very rigid and could break.

I just need a quick reply.

I am using Microwave office for RF simulation for the interface between CC1120 and SKY65366.
The datasheet of CC1120 mentions that RF optimum load impedance for PA pin (pin 17) is 55+25j.
For transmission from CC1120 side, do I need to put port impedance of the PA pin of CC1120 as 55-25j in MW Office?