Keysight E8663D, Руководство пользователя

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228 Keysight E8357D/67D & E8663D PSG User’s Guide
Custom Real Time I/Q Baseband
Working with Phase Polarity
Working with Phase Polarity
To Set Phase Polarity to Normal or Inverted
1. Press Mode > Custom > Real Time I/Q Baseband > More (1 of 3) > Phase
Polarity Normal Invert .
Phase Polarity Normal Invert enables you to either leave the selection as
Normal (so that the phase relationship between the I and Q signals is not
altered by the phase polarity function), or set to Invert and invert the
internal Q signal, reversing the rotation direction of the phase modulation
vector.
When you choose Invert, the in–phase component lags the
quadrature–phase component by 90° in the resulting modulation. Inverted
phase polarity is required by some radio standards and it is useful for
lower sideband mixing applications. The inverted selection also applies to
the I, I–bar, Q, and Q–bar output signals.
Working with Differential Data Encoding
The Differential Data Encode Off On menu enables you to toggle the
operational state of the signal generator’s differential data encoding.
— When set to Off, data bits are not encoded prior to modulation.
— When set to On, data bits are encoded prior to modulation. Differential
encoding uses an exclusive–OR function to generate a modulated bit.
Modulated bits will have a value of 1 if a data bit is different from the
previous bit or they will have a value of 0 if a data bit is the same as the
previous bit.
This section provides information about the following:
— Understanding Differential Encoding
—
“Using Differential Encoding” on page 232
Understanding Differential Encoding
Differential encoding is a digital–encoding technique whereby a binary value is
denoted by a signal change rather than a particular signal state. Using
differential encoding, binary data in any user–defined I/Q or FSK modulation
can be encoded during the modulation process via symbol table offsets
defined in the Differential State Map.
For example, consider the signal generator’s default 4QAM I/Q modulation.
With a user–defined modulation based on the default 4QAM template, the
I/Q
Values
editor contains data that represent four symbols (00, 01, 10, and 11)
mapped into the I/Q plane using two distinct values, 1.000000 and –1.000000.