Common Settings (Channel Quality)
The specify the result computation mode as well as spacing and number of tones in the multitone stimulus signal.
selects the method of computing the response results.
Statistical computation mode (and all of the controls that support this mode) is currently a BETA feature.
Multitone: Uses the original method, orthogonality of tones in a multitone stimulus.
Statistical (BETA): Uses a more generalized, statistical method. Uses Analysis > Frequency Smoothing to reduce the variance of the estimate. In addition, the response can be computed relative to a measured stimulus in this mode. The Statistical mode requires that you choose either Constant Amplitude/Random Phase, or the Random I/Q mode for generating the stimulus.
(only applicable when Computation Mode = Statistical) selects the reference for computing channel response trace results.
Ideal Stimulus: Channel response traces are computed relative to the ideal stimulus.
Measured Stimulus: Channel response traces are computed relative to the Reference Channel. The assumption here is that the stimulus into the DUT Device under Test: An acronym used to describe some type of electrical apparatus connected to test instrumentation. The apparatus can range from a single component to a complex subsystem such as a mobile phone, base station or MSC. is being measured so that the computed responses will not include the channel response of the stimulus source RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz). chain.
The Compensation tab parameters control tracking of both the Reference Channel and the other channels, but the estimation of the tracking is only done using the Reference Channel and then applied to all the other channels.
(only applicable when Computation Mode = Statistical) selects the measurement channel to use as a reference when computing DUT results such as channel response and time offset.
selects the tone spacing (in Hz) for the current multitone signal definition. Stimulus signal bandwidth is determined by Tone Spacing x (Number Of Tones - 1). An additional tone-spacing is required for analysis bandwidth (VSA Span).
Tone Spacing determines the length of the stimulus waveform.
Specifies the number of tones in the multitone signal definition. A read-only annotation next to the Number of Tones field provides feedback on the stimulus signal bandwidth (in Hz), which is determined by Tone Spacing x Number Of Tones.
Changing this value will reset the definition to default gain and phase values for all tones.
Entering an odd number of tones may place the center tone on DC. This may result in the LO feedthrough at DC affecting the results of the channel quality measurement.
Tone Spacing is limited by PC memory (PC that is running the 89600 VSA software) and the bandwidth/capture limitations of the hardware.
(only available when Computation Mode = Multitone) determines whether to compute the unbalanced channel response (in addition to the balanced channel response, which is always computed). This mode requires a special stimulus signal generated by the 89600 VSA software (see Save to File…).
The Statistical Computation Mode always computes the Balanced/Unbalanced/I/Q responses.
Several new metrics and trace results are available for measuring unbalanced (and balanced) channel response:
Summary trace - IQ impairment metrics (only available when Support Balanced/Unbalanced/IQ Responses is enabled):
Balanced and Unbalanced Channel Frequency Responses - the balanced response is the part due to reflections/multipath. The unbalanced response is the part due to IQ impairments.
I and Q Channel Frequency Responses - computed from the Balanced and Unbalanced responses, expressing the response separately for the In Phase and Quadrature Phase components of the channel.
Inverse versions of Balanced, Unbalanced, I and Q Channel Frequency Responses - you can use these to predistort the I/Q samples before sending through an I/Q modulator. Or you can correct I/Q samples received from an I/Q demodulator.
Impulse Responses - corresponding to the frequency responses.
See Making an Unbalanced Channel Response Measurement for more information.
stabilizes the phase between the balanced and unbalanced ch freq response. Triggerless Mode is especially useful when a device under test cannot provide a Trigger Out signal. Triggerless Mode is available when Support Balanced/Unbalanced/IQ Responses is selected.
Enabled - (Default) No trigger is required.
The stimulus waveform will be doubled in length when this parameter is enabled.
Disabled - A waveform trigger is required to trigger the acquisition at the start of the stimulus waveform.
Triggerless Mode affects the stimulus waveform, so you will need to re-export the stimulus to your signal generator after changing this setting.
See Also
