ni5660 Configure for Spectrum

This VI configures the RF Signal Analyzer hardware to acquire a frequency-domain spectrum with spectral settings you specify. Center frequency, span, and resolution bandwidth parameter settings define the spectrum. You can also specify window type, number of spectral lines, and resolution bandwidth (RBW) definition.

This VI configures the reference level and attenuation settings used by the RF downconverter module, and the horizontal settings and acquisition type used by the IF digitizer module. It returns a correction factor array. Wire this output to the correction factor input parameter of the ni5660 Read Averaged Power Spectrum VI or ni5660 Read FFT Spectrum VI.

receiver info in is the instrument handle that you obtain from the ni5660 Initialize VI. The handle identifies a particular RF Signal Analyzer session.

advanced settings parameters specify additional spectrum characteristics. These optional inputs are necessary only if you want to use a specific window, define the exact number of spectral lines, or change the RBW definition. window specifies the time-domain window the VI uses. The VI handles the scaling effects of the window. You can select one of the following values for window: 0: Uniform (no window) 1: Hanning 2: Hamming 3: Blackman-Harris 4: Exact Blackman 5: Blackman 6: Flat Top 7: 4-term Blackman-Harris 8: 7-term Blackman-Harris 9: Low side lobe Default Value: 7-term Blackman-Harris spectral lines specifies the number of data points in the returned spectrum. You can set the control to any positive number. Typical values include 400 and 800. This VI gives precedence to the spectral lines parameter over the resolution bandwidth parameter when calculating the acquisition size. The spectral lines control takes precedence over other control settings in the advanced settings cluster. If you set this value to –1, the VI calculates the number of data points consistent with the specified resolution bandwidth and the actual sample rate. Default Value: –1 RBW definition specifies the definition of the resolution bandwidth parameter. You can select one of the following values: 3 dB Defines the RBW in terms of the 3 dB bandwidth of the window specified in the window parameter of the advanced settings cluster. 6 dB Defines the RBW in terms of the 6 dB bandwidth of the window specified in the window parameter of the advanced settings cluster. ENBW Defines the RBW in terms of the Equivalent Noise Bandwidth (ENBW) of the window specified in the window parameter of the advanced settings cluster. bin width Defines the RBW in terms of the display resolution, which is the ratio of the sampling frequency to the number of samples that you acquire. Default Value: 3 dB

	center frequency (Hz) specifies the center frequency of the computed spectrum. If you specify a center frequency of 1 GHz and span of 100 MHz, the spectrum ranges from 950 MHz to 1050 MHz after zoom processing. The actual center frequency can differ slightly from the value you specify. Default Value: 100 MHz
	span (Hz) specifies the frequency range of the computed spectrum. If you specify a center frequency of 1 GHz and span of 100 MHz, the spectrum ranges from 950 MHz to 1050 MHz after zoom processing. This value may be coerced based on hardware settings and downconversion specifications. Default Value: 20 MHz
	resolution bandwidth (Hz) specifies the resolution along the X axis of the spectrum. The VI uses the resolution bandwidth value to determine the acquisition size. If a spectral lines value is specified in the advanced settings cluster, that value takes precedence over this control. If this control and the spectral lines control are both set to –1, the spectrum uses a default of 400 spectral lines. The actual resolution bandwidth can differ slightly from the value you specify. Query the value of the actual resolution bandwidth parameter to see the adjusted resolution bandwidth. By default, this VI defines the resolution bandwidth in terms of the 3 dB bandwidth of the window specified in the window parameter of the advanced settings cluster. You can change the RBW definition by using the RBW definition parameter in the advanced settings cluster. Default Value: 100 kHz

error in accepts error information wired from previously called VIs. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. status boolean is either TRUE (X) for an error, or FALSE (checkmark) for no error or a warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. code input identifies the error or warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. source string describes the origin of the error or warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.

reference level (dBm) specifies the expected total integrated power of the RF input signal in dBm. Refer to Signal Levels for more information. Default Value: 0 dBm

auto attenuation specifies whether the attenuation setting is automatically determined or user-specified. Set this parameter to DISABLE to specify a downconverter module attenuation setting using the attenuation parameter. When auto attenuation is set to ENABLE (default), NI-RFSA automatically chooses an attenuation setting that optimizes noise and distortion levels for the specified reference level. When this parameter is set to ENABLE, the attenuation parameter is ignored. Default Value: ENABLE

attenuation (dB) specifies the downconverter module attenuation setting in dB. This VI uses the reference level and attenuation parameters to calculate the desired signal level at the first input mixer. Mixer level values influence noise and distortion factors as follows: Mixer Level Noise and Distortion Effects –20 dBm Moderate distortion, low noise –30 dBm Best compromise between noise and distortion –40 dBm Low distortion, high noise Calculate the attenuation setting using desired reference level and mixer level settings, according to the formula: attenuation = reference level – mixer level For example, when using a reference level of 0 dBm (default) with moderate distortion and low noise, specify an attenuation value of 20 dB: attenuation = (0 dB reference level) – (–20 dB mixer level) Default Value: 20 dB

receiver info out passes a reference to your instrument session to the next VI. receiver info was obtained from the ni5660 Initialize VI. Note  Do not modify the contents of this wire manually.

actual resolution bandwidth returns the adjusted resolution bandwidth used by the VI. This VI adjusts the resolution bandwidth based on the value of the span and spectral lines parameters.

correction factor returns an array of correction factors. Apply the correction array to the acquired spectrum by connecting this output to the correction factor input parameter of the ni5660 Read Averaged Power Spectrum VI or the ni5660 Read FFT Spectrum VI. Do not modify the values.

error out passes error or warning information out of a VI to be used by other VIs. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. status is TRUE (X) if an error occurred, or FALSE (checkmark) for no error or a warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. code identifies the error or warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed. source describes the origin of the error or warning. The pop-up option Explain Error (or Explain Warning) gives more information about the error displayed.