Agilent Technologies E4406A manual

Making Measurements

Making the Spectrum (Frequency Domain) Measurement

❏Auto Peak - Select this to set the ADC range automatically to the peak signal level. Auto peak is a compromise that works well for both CW and burst signals.

❏AutoPeakLock - Select this to hold the ADC range automatically at the peak signal level. Auto peak lock is more stable than auto peak for CW signals, but should not be used for “bursty” signals.

❏Manual - Allows you to access the selection menu: −6 dB, 0 dB, +6 dB, +12 dB, +18 dB, +24 dB, to set the ADC range level. Also note that manual ranging is best for CW signals.

—Data Packing - Allows you to select Auto (the default) or the Short (16 bit), Medium (24 bit) and Long (32 bit) methods of data packing. The short, medium, and long methods are not compatible with all settings and should not be used unless you are familiar with data packing methods. Auto is the preferred choice.

❏Auto - The data packing value most appropriate for current instrument settings is selected automatically.

❏Short (16 bit) - Select this to pack data every 16 bits.

❏Medium (24 bit) - Select this to pack data every 24 bits.

❏Long (32 bit) - Select this to pack data every 32 bits.

—ADC Dither - Allows you to toggle the ADC dither function between Auto, On, and Off. When set to Auto (the default), the ADC dither function will be activated when a narrow bandwidth is being measured, and deactivated when a wide bandwidth is being measured. “ADC dither” refers to the introduction of noise to the digitized steps of the analog-to-digital converter; the result is an improvement in amplitude accuracy. Use of the ADC dither, however, reduces dynamic range by approximately 3 dB.

—Decimation - Allows you to toggle the decimation function between Auto and Man, and to set the decimation value. Auto is the preferred setting, and the only setting that guarantees alias-free FFT spectrum measurements. If you are familiar with the decimation feature, you can change the decimation value by setting to Man, but be aware that aliasing can result in higher values. Decimation numbers 1 to 4 describe the factor by which the number of points are reduced. The default setting is 1, which results in no data point reduction.

—IF Flatness - Allows you to toggle the IF flatness function between On and Off. If set to On (the default), the IF flatness feature causes background amplitude corrections to be performed on the FFT spectrum. The Off setting is used for adjustment and troubleshooting of the test instrument.

102 Chapter 4