I wish to develop a PCB with an RF front end that can reach the maximum allowed ISM band TX power with closed loop power control to limit RF output power over temperature, spectrum and voltage variations. Most of the modules on the market output only 23dBm and run with the PA output power in an open loop configuration. I would also like to add an antenna diversity switch and LNA with bypass switch. These upgrades should get at least another 5 or 6 dB in link margin. Other features might include power per rate which can be realized with closed loop power control to take advantage of the relaxed EVM requirements for the lower QAM and QPSK modulations, while backing off for the higher order modulation rates.
Where do I find information about how to use the TSSI pin on the SoC and where do I find information about RSSI in order to use the LNA and antenna diversity switch? Also, how to acquire the bare SoC chips from MorseMicro to place on my PCBs?
TSSI and Transmit Power Control
Our SoC includes a TSSI input pin, labeled as GPAIO/TSSI in the SoC pin layout. Closed-loop transmit power control is currently under development and not yet available. The purpose of TSSI is to compensate for TX power drift over time and address board-to-board power variations, if any. To achieve your objective of setting transmit power per MCS rate, we provide an open-loop power control mechanism. This allows you to configure the desired transmit power per MCS and bandwidth via a Board Configuration File (BCF).
LNA Control
Our chip supports the use of an external LNA with a bypass option, which is already implemented in our MM6108 reference design. The system automatically controls the functionality of the LNA based on incoming RSSI as part of the AGC process.
Antenna Diversity
Antenna diversity is an essential feature on our roadmap, and we’re happy to share that the initial version of this feature is scheduled for release in the near future.
Thank you for the update. I would like to participate in advancing calibrated closed loop TX power control as it offers many advantages over open loop control. How do I become an ODM partner with Morse Micro? Is there a way to set up a direct phone call or Zoom meeting with you?
Hi spoatech,
All of the items mentioned are on our roadmap, and due to the nature of the chip architecture, there is not much an external party can do to get these features working.
We work with a lot of ODM’s however are always interested in bringing additional value to our product offerings.
Please send through some details to me and we can organise a call.
Thanks
Chad
VP of Applications
Morse Micro
Hi Chad,
Thank you for the response. I would indeed like to pursue an opportunity to work with MorseMicro to develop products based on the MM6108 and the upcoming MM8108 SoCs. If you would be so kind as to let me know a convenient time for a call, I will be happy to share more information about these project goals. I am available between 7:00am and 11:00pm CST. Please find my contact info in my MM account profile.
Thanks.
Hi Chad, I’m designing this high power board using an external digital attenuator with enough range to reduce the power for the PA input and with the PA gain, allow the power at the antenna to reach 30dBm. I am placing a directional coupler just before the LPF and TxRx switch with coupled power feeding a log amp. The log amp output will go to an ADC pin on the STM32 micro, triggered by the SoC TX signaling. This will allow the STM32 to adjust the digital attenuator to keep the desired power up to 30dBm. I will calibrate the board using a power meter in gated mode and capture enough data to curve fit an equation that closely approximates the average power, based on the log amp. The circuit will also have an LNA and antenna switch. This approach will probably not be as reactive as the same function performed by the SoC, but should keep an average power pretty close to the target power.
Does the MM6108 SoC provide PER statistics? Or do I need to use something like IPERF UDP?
This board breaks ranks with low cost low current modules, but my goal is high performance with best range.
Wow. This sound like a beast of a system you are building. We typically are driven for ultra low cost which rules out these sort of implementations.
Have a look at the morsectrl stats. There should be enough info in there to indicate the successful and failed RX packets.