 Hello, this is the introductory video of a series about a practical example of RF matching of STM32WL. This video series shows a practical example how to measure and fine tune the STM32WL transmitter and receiver circuits. There are many ways how to do it. The presented example is only one of many. This example is based on measurements of the STM32WL board. No RF simulations are used. Variant with RF switch is used. Other variants, like IPD or DirectI, are not covered. The goal of this video series is to show a step-by-step practical example how this task can be handled. Another piece of information which this series shows is the difference between a purely analytical description and real measurements. This is mainly due to the fact that some parameters, such as the effect of specific PCBs, are usually not known in the analytical description. There are two types of STM32WL boards from ST. The first one is STM32WL nuclear board. It's a general-purpose board for prototyping. There are many features implemented on the board. For this reason, many compromises were made in the design, for example in the PCB layout. The next type of boards are STM32WL reference boards. There are several types of reference boards, which differ, for example, in STM32WL package, number of PCB layers, if RF switch is used, etc. The reference boards use a recommended layout to get the best parameters. This is recommended source for new designs with STM32WL. The design files of the reference boards can be downloaded from st.com. The STM32WL nuclear board is used in this video series. Revision C of the nuclear board is used. Other revisions may be different. This board was used because it's widely spread in the field and is easily available. The nuclear board contains STM32WL55 in BJ73 package. Both transmitter branches, low power and high power are implemented on the board. For this reason, DC switches are needed in the design. The board has embedded ST-Link v3 and power regulators. More details about this board can be found in this user manual. Number goals for the transmitter are frequency band from 863 to 870 MHz, maximum power 14 dBm at the low power pin. Only this low power output is used, high power output is unused. All harmonics and spurious components of the output signal must be below minus 30 dBm to fulfill European regulatory limits. Unmodulated power consumption is about 25 mA which is typical value for 14 dBm output power in unmodulated carrier mode. Concerning the receiver, our goals are the same frequency band as the transmitter. Good matching, the standing wave ratio should be below 2 at the SMA port. The receiver sensitivity for the selected modulation should be according to the datasheet. Here is the schematic of the RF path which we will focus on. All original components in the transmitter path were removed. The high power output path is not used in our example. All components along this path are not fitted on the board. We will do matching, filtering and optimization of the low power path. The last RF path is the receiver path. The position of RF circuits on the PCB is as follows. High power matching and filtering circuit. As it was mentioned, it is not used in this example. Here we have low power matching and filtering circuit. Receiver matching and vanu-light circuit is next to it. RF switch is between low and high power circuits. Antenna matching network is here. And finally, the SMA connector. We use Lora1 80-slave firmware in the example. For simplicity, I will use only name 80-slave in the next part of this video. It's available in the STM32QWL package. The version 110 was used in this particular case. Other versions may behave differently. Description of all 80 commands can be found in the application node AN5481. These are the useful commands that we will use in this series, as follows. We use the following measuring instruments. Spectrum analyzer and arm meter, which are important mainly for the transmitter measurements. Vector network analyzer can be used for measurement of filters or antenna matching. Vector signal generator is useful for sensitivity measurement of the receiver. What we use needed for this task are soldering station, microscope or magnifier glass. It is not mandatory, but very useful. If there is no RF connector on the board, we need to connect to the board somehow in order to take measurements. To do this, we can use semi-rigid SMA cable or pigtail. A PCB layout has a significant impact on impedance matching and the measurement. It may contain a lot of parasitic components which may affect calculated values of components. The parasitic components may depend on, for example, size of pads, discontinuities, thermal bridges and stops. Here is an example of a stop. If one end of the trace is not fitted, then the open end impedance can be transformed to another impedance at the opposite end, which can affect the original parameters of the circuit. In case of thermal bridges, they add additional parasitic inductance. To measure the matching network or filters, we need to connect a measuring instrument. If there is no dedicated RF connector, we have to use an artificial connection, for example semi-rigid cable, also known as the pigtail. The measurement itself has also impact to the measured values. We must take it into account when evaluating the results, for example. The pigtail is not ideal connection. There is discontinuity. Ground connection has also big impact. It is recommended to be as close as possible to the connection point. The pigtail loads the measured device by parasitic impedance which can affect the measured values. When measuring only one particular part of the board, some components may be removed. In this case, stops may have impact. The pigtail and measurement cables have some insertion loss. It is usually small below 0.5 dB. In our measurement example, this loss of the cable is not compensated. As mentioned earlier, we use STNR32WL nuclear board, revision C in our example. The original transmitter metric network and filters were removed. There are several main blocks. In the example, we measure and tune each block separately. Finally, overall measurement and fine tuning is made. The matching network and filters optimization is usually an iterative process. It may take some time to get the expected result. The video series is divided into four parts. The first one is this introductory video. The second part is about transmitter matching network and the nut filter. Next part is about low pass filter, RF switch and the antenna matching network. The last part covers the receiver matching and the button like circuit. Thank you for your attention.