Atec Agilent-8510C - Manual (Page 19)

19
Bandpass impulse: The bandpass impulse simulates a
pulsed RF signal (with an impulse envelope) and is used
to measure the time domain response of band-limited
devices. The start and stop frequencies are selectable by
the user to any values within the limits of the source and
test set used. The bandpass time domain response shows
changes in the parameter values versus time. Bandpass
time domain responses are useful for both reflection and
transmission measurements.
Response resolution
1 : In bandpass impulse mode,
response resolution is defined by the 50% impulse width
of the time stimulus. This depends on both the frequency
span and the window used (see Windows):
Time domain range
The time domain range, the range over which the display
is free of response repetition, depends on the frequency
span and the number of points as shown in the following
graph
2 :
Range resolution: Range-resolution is the ability to
locate a single response in time. It is a function of the
time span selected and the number of data points. Range-
resolution = time span/(number of points –1). Range-
resolution better than 1 mm (3 ps) can typically be
achieved. This is determined by source stability.
Windows: The windowing function can be used to modify
(filter) the frequency domain data to reduce overshoot
and ringing in the Time Domain response. Three types
of windows are available-minimum, normal, maximum.
Typical effective impulse width and sidelobe response
to each type of window are shown in the table below:
Kaiser
Window bessel Impulse Sidelobes
type parameter width (relative to peak)
Minimum 0 Minimum –15 dB
Normal 6 1.5x Minimum –50 dB
Maximum 13 2.5x Minimum –90 dB
Gating: The gating function can be used to isolate
individual Time Domain responses. In converting back to
the frequency domain the effects of the responses outside
the gate are removed. The location and span of the gate
can be controlled by setting either the gate center
position and time span or by setting the gate start and
stop times.
Measurement throughput summary
The following table shows typical measurement times for
an 8510C system with full two-port error correction.
Number of points
51
101 201 401 801
Measurement 3
Ramp sweep 4 270 ms 340 ms 470 ms 740 ms 1.3 s
Stepped sweep
Avg factor = 1 1.25 s 2.5 s 5 s 10 s 20 s
Avg factor = 128 6.25 s 12.8 s 24 s 49 s 106 s
Time domain conversion 5 50 ms 100 ms 200 ms 400 ms 800 ms
GPIB data transfer to computer 6
Internal format 20 ms 30 ms 50 ms 100 ms 200 ms
ASCII format 240 ms 460 ms 900 ms 1.8 s 3.6 s
IEEE 754 floating point format
32 bit 20 ms 40 ms 80 ms 160 ms 320 ms
64 bit 40 ms 80 ms 150 ms 300 ms 590 ms
Remote programming
Interface: GPIB interface operates according to IEEE
488-1978 and IEC 625 standards and IEEE 728-1982
recommended practices.
System interface: The 8510C system bus is a GPIB port
used exclusively by the 8510C to control and extract
information from the other instruments in the system
such as the RF source, test set, and the
digital plotter.
Addressing: The GPIB addresses of the 8510C and all
instruments connected to the 8510 system interface can
be verified or set from the 8510C front panel via the
LOCAL menu. Addresses can range from 0 to 30 decimal.
1. Response resolution is the ability to resolve two closely spaced responses of equal magnitude. For example, in time impulse response, two equal
responses that are separated in time by less than one impulse width cannot be resolved as two separate responses.
2. In low pass mode (step or impulse), range is limited by the minimum spacing between frequency domain data points (45 MHz, or 22.5 MHz with 801
points). This limit is labeled on the graph as “low pass limit”.
3. Includes system retrace time, but does not include source bandswitch times (typically 50 msec each). Time domain gating is assumed off.
4. If averaging is used, multiply the above ramp sweep measurement times by the averaging factor to get the total time.
5. Option 010 only, gating off.
6. Measured with an HP 9000 Series 300 computer. Single point data transfers can be accomplished in approximately 1 msec per point using the fast
CW mode.