4 Replies Latest reply on May 14, 2018 7:44 AM by e.pratt_1639216

    Ble Scan RX power db Question

    hbkim

      Hi

       

      My project is based on the links below.

        (Link : PSoC-4-BLE/100_Projects_in_100_Days/Day010_Observer at master · cypresssemiconductorco/PSoC-4-BLE · GitHub)

       

      The main purpose is to scan surrounding beacons.

       

      However, I would like to reduce the rx power of the observer, because the beacon, which is far from the observer, is also scanned.

       

      I know that the LNA_GAIN value in the BLE_BLERD_CFG1 register adjusts the rx power.

       

      I can see the VHG, HG, IGH, MH, LG, and VLG settings in the BLE_Register_TRM document.

      (reference link : PSoC 4100-BL/4200-BL Family: PSoC® 4 BLE Registers Technical Reference Manual (TRM) )

       

      I have one questions here.

       

      Do you actually know how many dBs the above settings are?

      I want to know the db value of rx that I get through the above settings.

       

       

      Thansk

        • 1. Re: Ble Scan RX power db Question
          e.pratt_1639216

          Atm the TRM isn't letting me download it from the Cypress site, but I'll try again later. At a guess, it would be somewhere on the order of 1.5 dB, 3 dB, or 6 dB (3 dB is double).

          • 2. Re: Ble Scan RX power db Question
            e.pratt_1639216

            Looking in the TRM, page 347 refers to the LNA gain setting of 101 being 66 dB, and the potential to boost the sensitivity by 2-3 dB at the expense of increased current at that setting level (sounds like it will boost it at other levels with little-to-no effect.)

            With the highest being 66 dB, and the lowest being 0 dB, I would see the steps as 13.2 dB

            • 3. Re: Ble Scan RX power db Question
              hbkim

              I saw the component document at the link below.

              (http://www.cypress.com/documentation/component-datasheets/psoc-creator-component-datasheet-bluetooth-low-energy-ble )

               

               

               

               

              In p84, I saw the function "CyBle_SetRxGainMode"

              In the function description, the "CYBLE_BLESS_HIGH_GAIN_MODE" setting is called -91dB.

              What is the difference between minus db and plus db?

              And how does the LNA Gain and CyBle_SetRxGainMode settings match?

              • 4. Re: Ble Scan RX power db Question
                e.pratt_1639216

                Positive dB is a stronger signal; Negative dB is the same proportional change in signal strength, but it is decreased signal strength instead.

                The Normal vs High Gain modes differ by the 2dB difference, which is a roughly 1.6~ times increase in signal reception sensitivity.

                The radio lists -89 dB as the default RX sensitivity as that is the fractional power of a signal from a unity-gain transmitter that can be correctly received. For example, a radio transmitting at 1 W/m^3 would be receivable by the receiver at a -89 dB drop in signal strength before reaching the receiver, this dB value corresponds to 0.0000000126 W/m^3 of signal strength needed to function. (This is a rough calculation, but it demonstrates the math and concept pretty well.)

                No idea how the LNA Gain matches to the CyBle_SetRxGainMode() function, but it could be a difference between the TRM and the cypress function that sets the settings found in the TRM to specific configurations for each setting/mode.