The DSA815 spectrum analyzer incorporates an all-digital intermediate-frequency (IF) section for accurate, high-resolution measurements from 9 kHz to 1.5 GHz. A spectrum analyzer provides a display of signal amplitude versus frequency, allowing an operator to select from a series of IF filters to reduce the displayed bandwidth and isolate a signal of interest from the noise floor. By designing the DSA815 spectrum analyzer with a digital IF section, the variations in amplitude over time and frequency associated with analog filtering can be minimized. With the stable filters afforded by digital signal processing, the DSA815's digital IF section allows an operator to use an IF filter just wide enough to pass a signal of interest. In the process, it limits the amount of noise received by the analyzer’s receiver and shown on the display, thus lowering the instrument’s displayed average noise level (DANL).
The use of a digital IF helps minimize errors due to filter switching and reference level uncertainties; it can even limit errors produced when switching between logarithmic and linear displays of amplitude, which occur when using a spectrum analyzer with a traditional analog IF section. The DSA815 provides 3-dB resolution-bandwidth (RBW) filters that can be set from 100Hz to 1MHz in a 1-3-10 sequence with nominal RBW uncertainty of less than 5%. It also offers video-bandwidth (VBW) filters from 1Hz to 3MHz in a 1-3-10 sequence. Operators can set frequency spans from 100 Hz wide to the full bandwidth (1.5 GHz) of the instrument.
The DSA815 derives its frequency stability and accuracy from an internal 10-MHz reference oscillator with aging rate of better than 2 ppm/yr and temperature stability of better than 2 ppm from +20 to +30°C. It can also work with an external 10-MHz reference source (via a BNC input connector) at a level of 0 to +10 dBm. The DSA815 exhibits phase noise of typically −80 dBc/Hz offset 10 kHz from any carrier.