The analog audio measurement can measure Audio Level (V), SINAD (dB), Distortion (%), and Audio Frequency. Measurements are made through the test set's front panel AUDIO IN connectors. When measuring a mobile's audio output, the audio signal may come from either an acoustic coupler or from a test interface connection to the mobile's audio circuitry.
SINAD is one of four measurements available from the Analog Audio measurement. However, SINAD measurements are not typically made when testing GSM mobiles but are more common when testing AMPS or analog mobiles.
The AUDIO IN connectors feed the inputs to a floating-input differential amplifier, with each input having an impedance of about 100,000 ohms to chassis ground. For best noise immunity, connect the audio signal and its ground reference to the two input ports through shielded coaxial cables, or input the signal to the AUDIO IN HI connector and ground the AUDIO IN LO connector's center contact.
Select On or Off to enable or disable the SINAD and Distortion measurements. This can be done remotely using the SETup:AAUDio:SDIStortion:STATe . When On, these measurement results are displayed on the screen below the Audio Level measurement. The SINAD/Distortion Fundamental Frequency must be entered to specify the audio frequency for the measurement (range: 100 Hz to 10 kHz).
Select either Peak or RMS (default) for making and displaying an analog audio level measurement (does not affect other measurements). The type of detector selected is displayed next to the Audio Level measurement results. A 1-volt rms sinewave input signal would measure 1.414 V Peak when the Peak detector is used. A 1-volt peak input signal would measure 0.707 V RMS when the RMS detector is used.
The Expected Peak Voltage sets the analog audio clipping level and must be set. This voltage is always the absolute peak audio input signal voltage expected at the AUDIO IN connectors, and must be in the range of 7.07 mV peak (5 mVrms) to 20 V peak . Remember, measuring a 1-volt rms sinewave input signal would require a 1.414 V peak expected voltage value to avoid clipping (over-driving) the input.
Statistical Measurement Results (Multi-measurements)