CC1201: Matching impedance of RF ports to separate 50 ohm PA and LNA at 270-320 MHz.

Hi Bruno,

I'm not able to see your schematics. Can you upload a .pdf-file using the insert attachment functionality?

Thanks,
Simon

6036.894-06-01_sch.pdfHi Simon.

Hope you can see the attached pdf.

Thanks.

Bruno B.

Ok.
I have uploaded the file 894-06-01_sch.pdf.

Thanks again.
Bruno B.

Just a few comments:

With reference to www.ti.com/.../swra398a.pdf there are some component values that should be changed.
C174 = 39 pF
C176 = 1.0 pF
C175 = 3.0 pF
C173 = 56 pF

Not sure about the PI capacitor network you have connected towards the UFL's. Use series dc blocking capacitor towards both UFL's.

Hi Simon.

Thanks for your responce.

I will try you suggestions.

BTW I missed to tell you that I have already produced the prototypes and the performances of the TX path are ok for me.

I have some issues in the RX PATH. Sensitivity is not good.

About C62 and C181: they are not PI cap network. They are a single cap that can be mounted in 3 different positions.

In this way I can measure different paths in the circuit.

Attached you can find the PA section and the LNA section I have designed.

Thanks again.

Bruno B.

Have you verified that the LNA part of the RF path gives the wanted performance?

Hi Simon.

I have measured the sensititvity of the transceiver and it seems to be right: I have about -93/-95 dBm sensitivity @ 500 kbps.
The LNA section (antenna filter, TX/RX filter, attenuators, LNA and SAW filters) have a GAIN of 25 dB and it is ok.
The combination of the two does not have the wanted performance. I guess that is a Noise issue; I mean: the NF of the RX path seems to be very poor.
I will investigate more this issue.

Thanks and Best Regards.
Bruno B.

What is the sensitivity you see for the full system and what do you expect?

Hi TER.

I measure a sensitivity of about -80 dBm for the full system.

With reference to the attached pdf I have made the following considerations:

RX_PATH.pdf

RX PATH (excluding CC1201) Noise Factor Calculation

	IL dB	NF dB	F	Att	G	G dB
ANT BPF	1	1	1,2589254118	1,2589254118	0,7943282347	-1
TX/RX SWITCH	0,3	0,3	1,0715193052	1,0715193052	0,9332543008	-0,3
ATTEN	1,5	1,5	1,4125375446	1,4125375446	0,7079457844	-1,5
LNA	-30	1	1,2589254118	0,001	1000	30
SAW + SWITCH	3,2	3,2	2,0892961309	2,0892961309	0,4786300923	-3,2
TOT						24
F1	1,2589254118		G1	0,7943282347
F2	1,0715193052		G2	0,9332543008
F3	1,4125375446		G3	0,7079457844
F4	1,2589254118		G4	1000
F5	2,0892961309		G5	0,4786300923
			Gtot	251,188643151
RX PATH Noise Factor F (Friis Formula)				2,40090853
RX PATH Noise Figure NF				3,8037561459
Noise Floor Calculation for CC1201 without RX PATH
k Boltzmann	T Kelvin	BW Hertz	P(dBW)	Noise Floor dBm		Sensitivity dBm
1,38E-023	290	1	-203,977229157	-173,977229157		-95
1,38E-023	318	833333	-144,3687521338	-114,3687521338		CNR dB
						7
Noise Figure of CC1201
Using Equation  Sensitivity (dBm) = Noise Floor + CNR = -174 + 10 log B + NF + CNR where CNR = Carrier-to-Noise Ratio and assuming a desired CNR = 7dB (verified by Spectrum Analyzer readings), a Noise Floor of -114 dBm @ 45 °C (318 K) and a CC1201 Sensitivity of -95 dBm (as stated by data-sheet for 833 kHz RBW and verified by real measurement), we have:
Sensitivity (dBm) = Noise Floor + NF + CNR
NF = Sensitivity (dBm) - Noise Floor – CNR =				12,3687521338
F = 10^(NF/10) =				17,253420751
Noise Floor Calculation for RX PATH
k Boltzmann	T Kelvin	BW Hertz	P(dBW)	Noise Floor dBm
1,38E-023	290	1	-203,977229157	-173,977229157
1,38E-023	318	833333	-143,5769379361	-113,5769379361
NOISE FIGURE of Complete RX PATH (including CC1201)
Ftot = F_rxpath + (F_CC1201 -1)/G_Rxpath
			=	2,4656145635
NFTOT = 10log10(F)			=	3,919251866
Sensitivity of Complete RX PATH
Sensitivity (dBm) = Noise Floor + NF + CNR =				-102,6576860701

So I expect a sensitivity about -100 dBm.

Maybe something is wrong?

Thanks again.

Bruno B.

Hi Sverre.

Thanks for your comments.

What's about L193? Is it better to mount a 0 Ohm.

Thanks.

Bruno B.