4 Replies Latest reply on May 14, 2018 7:44 AM by epr_1639216

    Ble Scan RX power db Question

    haki_2218686

      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

          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

            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
              haki_2218686

              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

                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.