1
The RTSA7500 supports a 12-bit or 14-bit WB ADC as a manufacturing population variant. The
least significant bits of the 14-bit data representations are zeroed when the RTSA 7500 is
populated with the 12-bit WB ADC, hence, the subscript of 14 for IQ or I.
2
The 40MHz SH is only available in RTSA 7500 product version 1.3 (hardware revision 3) and
higher. Revision 2 hardware value varies between 30 or 35MHz, contact BNC's Support for further
details. See
*IDN?
to find out your hardware/product version (or the Administrative web-console to
the box).
3
SHN mode is only available in RTSA 7500 product version 1.3 (hardware revision 3) and higher
See
*IDN?
to find out your hardware/product version (or the Administrative web-console to the
box).
4
For SH and SHN modes, when the decimation is used, a frequency shift of 35MHz for non-WBIQ
models and 55MHz for WBIQ models will be applied automatically to bring the RTSA7500's center
frequency back to the zero IF. Thus, the data output will be I and Q.
5
IQIN mode is not available in RTSA 7500 product version 2.2 and higher. See
*IDN?
to find out
your product version (or the Administrative web-console to the box).
6
In DD and IQIN modes, there is no frequency tuning except for performing frequency shift. When
decimation is applied, the decimation will be around the zero frequency.
7
The HIF mode is only available for RTSA 7500-XXX-HIF product model and is indicated by the
:SYSTem:OPTions?
command's response code 002.
RTSA 7500 complies to VRT protocol for sending digitized IF data packets and their
associated context information depending on the capture mode. It is very important to
follow the VRT's IF Data Packet Class section (page
36
) for the exact VRT data output
formats as well as packing method.
RF Receiver Front-End
The upper portion of
Figure 2
shows a block diagram of the RFE within the RTSA 7500.
The architecture consists of a super-heterodyne (SH) front-end with a back-end that
utilizes an I/Q mixer similar to that in a direct-conversion (or zero-IF) receiver.
Depending on the frequency of the signals being analyzed, one of the three receiver
signal processing paths is selected. Signals in the frequency range 100kHz to 50MHz
are directly digitized, while all other signals are translated to the frequencies of the first IF
block via one of the other two signal processing paths. The IF block consists of a bank of
multiple SAW filters. SAW filter selection depends on the frequency of the input signal.
The output of the SAW filter feeds the I/Q mixer.
The three signal processing paths are further classified into different modes of operation
for the capture engine as shown in
Table 2
. The radio modes ZIF, SH, SHN and HDR
support tuning the center frequency from 50MHz to the maximum frequency supported by
the particular product model (ex. 8GHz, 18GHz, 20GHz, and 27GHz for RTSA7500-08,
RTSA7500
-18,
RTSA7500
-20, and
RTSA7500
-27, respectively).
The ZIF, SH and SHN radio modes support a tuning resolution of 10Hz. Digital frequency
shifting can then be used to enhance the tuning resolution to the nearest 1Hz (±0.23Hz)
The frequency shifting technology used is an embedded Numerically Controlled Oscillator
(NCO) (a Direct Digital Synthesizer or DDS) as described in the Digital Down Converter
subsection (page
20
).
The HDR radio mode supports a tuning resolution of 10Hz. No further fine tuning is
available.
The remaining two radio modes, DD and IQIN, support 50MHz IBW direct digitization of
the baseband from the external RF IN or I and Q IN ports, respectively. Hence, neither
