Typical applications for user defined filters include:
l
Custom filters other than those provided. In this case both measured and
reference filters are user defined.
l
Modified filters which are based on the raised cosine filter but add channel
equalization. In this case the measure filter is a user defined filter and the
reference filter is standard.
See “Creating User Defined Signals” earlier in this book for an example of how to
create, view, and apply a user defined filter.
The documentation for the Standard Data Format Utilities which accompanies this
analyzer also includes a section (Mathcad Examples) describing how to create
waveforms and filters for use with this analyzer.
Special consideration for MSK
Matched filtering of a demodulated signal is not available with the MSK
demodulators. The measured filter is normally off. A user defined filter can be
selected. Its primary use is for additional band-limiting and channel equalization.
IS-95 Filters
The analyzer includes two filters that conform to US CDMA digital cellular standard
IS-95:
l
IS-95 base-phase EQ filter.
l
IS-95 Chebyshev filter.
These filters let you measure base stations or mobile phones that conform to US
CDMA digital cellular standard IS-95. The IS-95 base-phase EQ filter is the inverse
of the forward all-pass phase-compensation filter that is specified for IS-95
base-station transmission. The IS-95 Chebyshev filter is the filter specified in IS-95
that provides overall channel filtering for both base-to-mobile and mobile-to-base
links.
The IS-95 base-phase EQ filter is applied to the I/Q measured signal. The
IS-95 Chebyshev filter is applied to the I/Q reference signal. For additional details,
see online help (press [Help], [1] to display the online help index, then scroll through
the index and select IS-95 base phase EQ Softkey or IS-95 Chebyshev Softkey).
Hint Select [CDMA BASE] or [CDMA MOBILE] to automatically configure the analyzer for
base-station or mobile measurements. Both softkeys are located under
[Instrument Mode], [demodulation setup], [demod format], [standard setups].
Digital Demodulation Concepts (Opt. AYA)
22 - 19
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