Tektronix RSA2200A, User Manual

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Setting Frequency and Span
3- 68
RSA2203A & RSA2208A User Manual
Vector Span
The input signals are scanned in frame units (one frame = 1024 points). There
are two frames: a physical frame to store scanned data and a logical frame to
store display data, as illustrated in Figure 3--53.
In the baseband, one logical frame is acquired at one scan regardless of the span
setting. You can acquire one logical frame with one scan of a span setting below
10 MHz in the RF band. In larger spans, one logical frame is built up by
acquiring data with multiple physical frames. For example, when the span is
20 MHz, one logical frame is composed from two (20 MHz/10 MHz) scans.
When the span is below 10 MHz in the baseband and RF band, one physical
frame corresponds to one logical frame; this is referred to as Vector mode, and
the span in vector mode is called the Vector span. In the other cases, one logical
frame is composed of multiple physical frames, and this is called Scalar mode.
Span
≤
10 MHz: Vector mode
Physical frame (Scan data) Logical frame (Display data)
Frame 0
Frame 1
Frame 2
... ...
Frame N
Frame 0
Frame 1
Frame 2
Frame N
Span>10 MHz: Scalar mode
Frame 0
Frame 1
Frame 2
Frame N
Frame 0
Frame 1
Frame 2
Frame N
...
...
... ...
Physical frame (Scan data)
Frame 0
Frame 1
Logical frame (Display data)
Figure 3- 53: Vector mode and scalar mode