Rx sensitivity of CC1101

Do you use the settings from SmartRF Studio? If no, please post your settings.

I use two CC1101DK433(TI supply ), one is TX, the other is RX; SmartRF Studio settings, Base freq 402.15MHz, channel spacing 300KHz, Carrier freq403.35MHz, Xtal freq 26MHz, data rate76.767KBaud, RX filter BW 232.14KHz, Modulation GFSK, deviation31.738KHz, TX power -10dBm.
Between TX and RX path, I use a 1dB/step adjustable attenuator.
Thanks for your support!

Not clear from the post if you measure PER (I assume you measure number of packets lost (PER), and not bit error rate (BER)) with input power level adjusted in steps of 1 dB. Please check the PER in the range -85 dBm to -55 dBm in 1 dB steps. I have come across cases in the past where there was ESD damage to the chip. This results in an area (in terms of input power level) above the sensitivity limit where the radio has high PER.

Thank you help me clarify PER and BER , my experimental data is (1000- Receive OK)/1000. This is PER ?

I do not approve there was ESD damage to the chip, because CC1101DK433(TI supply ) and every product of my company are the same bug.
Please TI RF engineer double check my experiment, thank you.

When we characterized CC1101 more than 10 years ago we also measured at 76.8 kbps and found the settings you get from the list of "typical settings" in SmartRF Studio to give optimum performance. If I understand correctly you are using the 76.8 kbps setting from this list as-is (i.e without any modifications). One important setting is AGCCTRL2.MAGN_TARGET. For 232 kHz RX filter BW this should be 7. (This is what you get if you select the 76.8 kbps setting from this list, but I am including this information to be 100% certain you don't modify this).

In order to move this case forward I still suggest you do the measurement outlined in previous post. I am not saying it is ESD damage, but we cannot know for sure before you have done the measurement. You can also test some of the other "typical settings" to see if you get the same behavior (i.e. increased PER for certain input power levels). The idea here is to check if this is a HW or register setting issue.

Thank you for your reply, The issue is" AGCCTRL2.MAGN_TARGET. For 232 kHz RX filter BW this should be 7" .

In addition, Can you help me estimate and optimize my settings to get the best Sensitivity ?
At present, Sensitivity=-96dBm, @PER=6%,Packet data size=41;
Base freq 402.15MHz, channel spacing 300KHz, Carrier freq403.35MHz, Xtal freq 26MHz, data rate76.767KBaud, RX filter BW 232.14KHz, Modulation GFSK, deviation31.738KHz

According to my test, the ACS ( Adjacent Channel Selectivity) of CC1101 is worse,
If only one set CC1101 work, The RX Sensitivty is -95 dBm,
But, another set of CC1101 work at another channel , the RX Sensitivity will be destroyed to -89dBm,
Can you help me optimize my settings to this issue?? for example,RX BW reduce to 100KHz ? ?

You have two posts on the same subject (one on CC130 and this one on CC1101). You can improve sensitivity and selectivity by using 162.5 kHz RX filter BW.

Use the 76.8 kbps settings from Studio (optimized for sensitivity) and simply change the RX filter BW from 232 kHz to 162.5 kHz.

AGCCTRL2.MAGN_TARGET. For 232 kHz RX filter BW this should be 7.
For 162.5 kHz , AGCCTRL2.MAGN_TARGET should be ??

In addition,The RSSI is OK, but  the LQI of CC1101 is fixed, why?

MAGN_TARGET sets the signal power level into the demodulator. If this is set too low the demodulator will have too small SNR to demodulate correctly. If you set it much higher than required for demodulation, the gain in the frontend will be higher than required (for strong signals) and hence blockers will also be amplified more than necessary impacting the selectivity/blocking. Ideally you should measure PER (packet error rate) vs input power level to find the optimum MAGN_TARGET, but for 162.5 kHz RX filter BW I think 5 or 6 is ok.

Don't understand the question about LQI, but some general inputs on LQI and RSSI below:

LQI (Link Quality Indicator) is a metric of the current quality of the received signal. The LQI gives an estimate of how easily a received signal can be demodulated by accumulating the magnitude of the error between ideal constellations and the received signal over the 64 symbols immediately following the sync word. LQI is best used as a relative measurement of the link quality (a low value indicates a better link than what a high value does), since the value is dependent on the modulation format.

To simplify: If the received modulation is FSK or GFSK, the receiver will measure the frequency of each "bit" and compare it with the expected frequency based on the channel frequency and the deviation and the measured frequency offset. If other modulations are used, the error of the modulated parameter (frequency for FSK/GFSK, phase for MSK, amplitude for ASK etc) will be measured against the expected ideal value

RSSI is a signal strength indication. It does not care about the "quality" or "correctness" of the signal. LQI does not care about the actual signal strength, but the signal quality often is linked to signal strength. This is because a strong signal is likely to be less affected by noise and thus will be seen as "cleaner" or more "correct" by the receiver.

1. A weak signal in the presence of noise may give low RSSI and high LQI.
2. A weak signal in "total" absence of noise may give low RSSI and low LQI.
3. Strong noise (usually coming from an interferer) may give high RSSI and high LQI.
4. A strong signal without much noise may give high RSSI and low LQI.
5. A very strong signal that causes the receiver to saturate may give high RSSI and high LQI.

Note that both RSSI and LQI are best used as relative measurements since the values are dependent on the modulation format.

Now our FHSS mechanism is based on RSSI to select better channel，But I think we should get LQI to select channel . unfortunately，the LQI is unvariable.

Now, I test the VSWR of Balun is worse at 403MHz, because we use the L C value according to the Recommended circuit of 433MHz.z
So, This will destroy the RX Sensitivity at 403MHz ?
do you have idears for this issue by replace the LC balun circuite?