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      • PCB number of layers vs Output power

        dasimon | 08/229/2017 | 07:33 AM

        Using a 2-layer PCB in the application hardware is usually preferred by customers due to cost saving purposes. Still, based on the RF output power level, unwanted radiation of top or bottom layer traces (mostly VDD or digital) can occur, which causes that the application can violate the harmonic limits of the related standards. In order to minimize the possibility of unwanted trace radiations, Silicon Labs recommends to use multilayer PCBs in the following cases:

         

        • >=16dBm output power at sub-GHz frequencies
        • >=10dBm output power at 2.4GHz

        Note that the actual recommendation depends on which standard (ETSI, FCC, ARIB, etc.) the application has to be compliant with.

         

        One can notice that not all Silicon Labs reference design follows the above listed recommendations. EZRadioPRO reference design boards are made on 2 or 4 PCB layers based on the output power, while all EZR32 and EFR32 reference design boards are using 4 or 6 PCB layers due to the complexity of the design. In the latter case, the layout routing could not be realised on a 2-layer PCB if all digital traces were intended to be used. Of course, on a custom design where the complexity of the design is much less, 2-layer PCBs can be used for EZR32 or EFR32 applications as well considering the above listed recommendations.

      • RF Range Calculator

        dasimon | 05/122/2017 | 10:19 AM

        Silicon Labs provides RF range calculators for customers to help estimating the actual range of their wireless applications. Simple RF Range Calculator is available to download from the following link below.

        http://www.silabs.com/documents/public/software/RF-Range-Calculator.zip

         

        RF range depends on the following parameters:

        • Conducted TX output power: the power driven to the antenna input [dBm]
        • TX antenna gain [dBi]
        • Conducted receiver sensitivity [dBm]
        • RX antenna gain [dBi]
        • Frequency [MHz]
        • Propagation factor (depends on the environment)

        Simple RF Range Calculator

        Simple RF Range Calculator is for those customers who don’t want to deal with difficult RF questions, just simply would like to get fast and reasonable results for both outdoor and indoor environments.

         

        Key features:

        • Fast and simple while accurate
        • Built in propagation factors, based on field measurements
        • Antenna height fixed to 1 to 1.2 meters
        • Supports all the unlicensed bands and custom frequency channels as well

        Usage

        Simple RF Range Calculator provides fast and accurate result as the customer selected the frequency band and set TX and RX parameters.

         

        Simple_Range_Calc_Fig1.png

         

        Frequency bands and custom frequency channels can also be selected.

         

        Simple_Range_Calc_Fig2.png

         

        TX Output Power and RX Sensitivity need to set up based on the radio device’s actual link parameters based on the data sheet.

        If the exact antenna parameters are unknown notes at the right side can help to determine the closest values.

         

        Simple_Range_Calc_Fig3.png

        The achievable RF range depends on many other factors as well. See the following KBA article for further details on RF range factors:

        https://www.silabs.com/community/wireless/proprietary/knowledge-base.entry.html/2017/12/07/rf_range_factors-fnT1

      • Si4x6x / EZR32 unused pins

        dasimon | 04/115/2017 | 03:22 AM

        Question

        How should I connect the pins which are not intended to be used on Si4x6x / EZR32?

        Answer

        • TX: Not connected
        • RXP, RXN: Not connected
        • GPIO pins: Not connected
      • EFR32 unused pins

        dasimon | 03/68/2017 | 05:21 AM

        Question

        How should I connect the pins which are not intended to be used on EFR32?

        Answer

        • SUBGRF_OP, SUBGRF_ON, SUBGRF_IP, SUBGRF_IN: Not connected
        • 2G4RF_IOP: Not connected
        • 2G4RF_ION: Connected to ground
        • VREGSW: Not connected
        • PAVDD: Connected to VDD
        • GPIO pins: Not connected
      • Recommended distance between antennas in an antenna diversity application

        dasimon | 11/330/2016 | 06:20 AM

        Question

        What is the recommended distance between antennas in an antenna diversity application?

        Answer

        Antennas in a product that implements antenna diversity have their antennas mounted at a distance of at least ¼ wavelength apart. This amount of spatial separation improves the probability that at least one antenna is NOT in a deeply faded signal condition. Another typical recommendation is ½ wavelength antenna distance, however, it can result quite large board sizes at low frequencies (e.g. for 434 MHz frequency ½ wavelength is 34,5 cm).

      • EZRadioPRO vs EZR32 PA matching network

        dasimon | 11/321/2016 | 10:30 AM

        Question

        Can I use the same matching network for EZRadioPRO and an EZR32 wireless MCU that is based on the same radio? 

        Answer

        The answer depends on the actual PCB layer stack-up as the distance between the top and the first inner (ground) layer determines the PCB parasitic capacitances, which plays part in the matching network.

         

        If the same PCB layer stack-up is used (or at least the distance between the top and the first inner layer is similar), in that case the same matching network component values should result very similar TX and RX performance for an EZRadioPRO radio and an EZR32 wireless MCU. If the PCB layer stack-up deviates significantly, it is not recommended to use the same matching network as the detuning can cause lower output power, higher harmonics, higher current consumption and sensitivity loss. 

      • EFR32 PA DC feed

        dasimon | 11/308/2016 | 06:17 AM

        Question

        At which pins should I apply DC feed for the sub-GHz and 2.4GHz PA of EFR32?

        Answer

        For the 2.4GHz PA, the DC feed should be applied on PAVDD pin.

         

        On the sub-GHz side, the PA DC feed is required through the TX output pins: SUBGRF_OP, SUBGRF_ON.

         

        For more details, refer to the EFR32 radio board reference designs.

      • EFR32 DC-DC to PAVDD

        dasimon | 11/308/2016 | 06:07 AM

        Question

        In which cases should I apply DC-DC to PAVDD when creating an EFR32 design?

        Answer

        Using the 1.8V output of the internal DC-DC converter of EFR32 for DC supply of the PA provides better efficiency (i.e. lower PA current for the same output power) compared to the case when the PA is running from the main 3.3V. The recommendation for applying the DC-DC output to PAVDD:

        • <= 13dBm for 2.4GHz
        • <= 14dBm for sub-GHz

        Above these power levels, using the main 3.3V supply for DC supply of the PA results better efficiency.

      • Difference between connecting the GND pin of TCXO to Pin 18 (GNDX) of Si446x or the common GND

        dasimon | 09/272/2015 | 09:19 AM

        Question

        What difference can be observed in RF performance when connecting the GND pin of TCXO to Pin 18 (GNDX) of Si446x or connecting it to the common GND?

         

        Answer

        In case of using TCXO, a few dB lower (2-3 dB) reference spurs (fxtal away on both sides of the carrier) can be observed when connecting the GND pin of TCXO to Pin 18 (GNDX). Connecting to either GNDX or to the common GND has no effect on any other RF parameters.

         

        For the proper connection of GNDX pin, please refer to the following Knowledge Base Article:

        http://community.silabs.com/t5/Wireless-Knowledge-Base/Si446x-pin-18-GNDX-connection/ta-p/132796

      • Range improvement calculation for a given extra link budget

        dasimon | 08/220/2015 | 05:30 AM

        Question

        How can I calculate the expected range improvement for a given extra link budget?

        Answer

        The range improvement can be calculated based on the following formula:

         

        Range improvement.png

         

        where

        - ΔR is the desired value of range improvement (ratio between the new and original range)

        - n is the propagation factor (the typical outdoor value is between 2.8 and 4)

        - ΔLB is the link budget improvement

         

        The ΔLB link budget improvement can be achieved with higher conducted output power, better conducted sensitivity, or with higher antenna gain either on TX or RX side.

         

        Let’s see an example:

         

        Assuming a ΔLB = 3 dB additional link budget improvement (e.g. the TX power is increased or RX sensitivity is improved by 3 dB) and outdoor line of sight between the transmitter and the receiver (which results ~n = 3 propagation factor), the range improvement will be the following:

         

        Range improvement-example.png

         

        Thus, for example assuming 400m original range, 3 dB higher transmitter power or 3 dB better sensitivity would result ~500m range.