Other Parts Discussed in Thread: CC1125, CC1120,
Hi,
I made a circuit based on CC1120+CC1190 combo Rev.1.0.1, just using CC1125 instead. The layout is more or less the same as on the reference board - at least for the RF-segment. If everything left as-is, I cannot get more than around 21 dBm output
- The SAW seems OK, I get around 2.5-3dB lower signal level on the filtered side than I set for CC1125 as output.
- Changing supply voltage 3.0 - 3.3 - 3.6V gives an increase on the output of just around 0.4 and 0.2dB. Voltage on the unloaded side of the L21 is around 0.1V lower than Vcc.
- Removing L22 from the shunt filter just increases 2nd harmonics as one would presume. Removing C23 increases 3rd harmonic. The C25 capacitor well out of the 5.6-7.5pF range noticeably reduces output power.
Case A - all parts placed:
for 0 dBm after the SAW, I get 19.2 dBm out, 200mA total consumption
for 3 dBm in, 19.8 dBm out, 220mA
for 6 dBm in, 20.8 dBm out, 250mA
for 9 dBm in, 20.9 dBm out - just a slight increase, but a whooping 400mA consumption
- Removing the filter L23-C24 and replacing it with a 100pF short, consumption jumps and output rises to more promising levels, but second and third harmonics increase just above the regulatory -30dBm.
Case B - filter L23-C24 removed:
for 0 dBm input, 19 dBm out, 300mA
for 3dBm in, 20.5 dBm out, 350mA
for 6dBm in, 22.5 dBm out, 410mA
for 9dBm in, 24.5 dBm out, 530mA
for 12dBm in (I know it is above max. safe value), 25.5 dBm out, 620mA
Tried and replaced L23 and C24 with slightly different value components doesn't seem to have much effect, I get values similar to case A.
Any advice what I am possibly doing wrong? With regard to the case A, I have a hunch there are several amplifiers chained together and one of them might be saturated. Should I try replacing parts around VDD_PA1 and VDD_PA2?
I can send you gerbers in private if needed.
Kind Regards,
Akos
