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PGA460-Q1: Noise in echo signal

Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460,

The echo signal that I  am receiving has lot of noise please tell me how to remove that noise.

  • Chethan,

    To help debug this, can you provide:
    •The transducer part number and driver mode.
    •The device settings, especially the time varying gain and digital gain values.
    •The supply voltage value and source type.
    •Target distance, and target type.

    Here is a note from the PGA460 FAQ / troubleshooting guide (www.ti.com/.../slaa733.pdf) which may help:

    5.7 The noise floor increases significantly at long distances.
    If the noise floor exceeds about 30% of the maximum value of 255 on the echo data dump, then too much
    gain is being applied. The TI factory gain ramps the TVG up to 90dB, which is not recommended for initial
    out-of-box evaluation; therefore, use the GUI defined Long or Short TVG presets, or shift the gain range to
    the next lower level. Try keeping the gain at a value to maintain a noise floor below a value of 80 out of
    255 to enable the 3:1 SNR scaling and proper threshold mapping. The best SNR scaling profile is when
    the noise floor can be minimized to a value of 1 out of 255, while the echo peak return is nearly saturated
    at 254 out of 255.

    Is there a difference in the noise floor when issuing a burst+listen command versus a listen-only command?

    Here are more noise related FAQs:
    6.1 There appears to be a continuous noise source present.
    If you are using the listen-only command, and are recording a large noise floor on the echo data dump, an
    ultrasonic aggressor may be present in the immediate area. Common aggressors include ultrasonic based
    room occupancy sensors, AC power supplies for laptops or bench equipment, and harmonic noise from
    other user components on custom hardware (such as motor switching noise). Try isolating the transducer
    by shielding its field of view, running the EVM using only the laptop in USB-boost power mode (LP-USB
    populated on Alt Pwr Mode jumper block), and/or going to an electronically-quiet room or outdoors.
    Figure 27. Murata MA40H1S-R Noise Floor Saturated Based on Listen-Only Command in a Room With 40-
    kHz Occupancy Sensor

    7.1 The laptop’s AC power supply raises the noise floor.
    When using the USB boost circuit to power the PGA460-Q1 EVM, the AC power adapter of the laptop
    may raise the noise floor of the PGA460. This ultimately depends on how stable the AC power adapter is.
    To prevent the AC power adapter from possibly influencing the noise floor, isolate and power the laptop
    from battery only.