Agilent 89410A Operation; Hp/Agilent 71910A Operation - Agilent Technologies 89410A Operator's Manual

Extending Analysis to 26.5 GHz with 20 MHz Information Bandwidth

Agilent 89410A Operation

The 89410A has two input channels (with option AY7), each with a bandwidth
of 10 MHz. Normally, this would represent the maximum bandwidth of the
signal to be analyzed. However, the 89410A is capable of treating the signals on
each channel as two parts of the same signal. That is, the signal going into
channel one represents the real part of a complex signal, and the signal going
into channel two represents the imaginary part. These two signals are usually
referred to as the in-phase and quadrature-phase components, or simply
I and Q.
The 89410A digitizes the I and Q signals which are, by themselves, real signals
and then combines them internally into a single complex signal of the form
I+jQ or CH1+jCH2, where j represents the square root of negative one. This
new complex signal, which exists only in digital form, has a maximum
bandwidth of 20 MHz, or twice the input bandwidth of the vector signal
analyzer.

HP/Agilent 71910A Operation

The 71910A wideband receiver (also called the MMS system) consists (at a
minimum) of an LO/controller module, an RF front-end module, a wideband IF
module, and a precision frequency-reference module. For optimum
performance of the entire system, the signal level should exist within a certain
range as it propagates through the system.
Although it is a simplification, the MMS system components can be viewed as
consisting of just a few blocks. They are an RF section with an attenuator and
conversion stage, an IF section with adjustable gain, and an IQ demodulator, as
shown in the previous block diagram.
The RF attenuator must be set to ensure the signal level reaching the
conversion stage doesn't cause damage or distortion. This attenuator has a
step size of 5 dB.
The IF section has a bandwidth of 100 MHz which ensures a relatively flat
frequency response over the center 20 MHz used in this system. A flat IF is
important in vector signal analysis. An IF with a significant amount of
amplitude unflatness or group delay distortion would produce significant
errors. This is especially true for modulation analysis where the IF
characteristics would introduce distortion in the time domain characteristics of
the signal. For example, group delay distortion in the IF would result in
increased inter-symbol interference in a digitally-modulated signal.
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