If Input Section - SIGNALCORE SC5312A User Manual

There is an auxiliary RF input to the device. This input is almost identical to the main RF input with the
exception of having an extra switch path. The intended use of this port is to allow the user a calibration
path without having to detach the device under test (DUT) already cabled to the main RF input port. The
user must perform in-situ equalization to remove IQ errors such as phase imbalance and quadrature gain
offsets that are inherent to the device. Providing this auxiliary path makes the task of characterizing the
system with and without a DUT much easier.
There are nine low pass filters in the RF filter bank. These filters are automatically selected when the user
enters the operating frequency. These filters can also be selected manually should the user choose to do
so. As with all filters there is generally an amplitude roll-off as the frequency nears its 3 dB cutoff point so
it is important to understand that frequencies near to the cutoff point may experience a slightly faster
roll-off of its IF bandwidth. A typical 1 dB IF bandwidth (IQ) is about 160 MHz. The user may want to
choose a higher frequency filter if this becomes a problem. See the programming section in this manual
for more details. The filters in both the RF and LO filter banks are identical and are listed below.

IF Input Section

The SC5312A and SC5313A require an external RF signal as their "Local Oscillator" (LO) for the frequency
conversion process. The external RF signal must be connected to the "LO in" port. The typical required
input level is -3 dBm to 3 dBm. These levels are required to sufficiently drive the IQ demodulator for good
linearity performance and conversion loss. The LO signal is conditioned through a bank of low-pass filters
to reduce the signal harmonics. Reducing the harmonics produces a "purer" signal tone, improving the
duty cycle of the LO as it drives the mixers of the demodulator. Additionally, the LO signal can be passes
out of the device via the "LO out" port. This output can be used as the input LO source for another
demodulator, for example. Driving multiple demodulators with the same derived LO signal optimizes
phase coherency between them. When this port is not in use, it is highly recommended to terminate it
into a 50  load.
©2013
Filter
1 dB Cutoff Frequency
Number
0 400 MHz
1 500 MHz
2 650 MHz
3 1000 MHz
4 1400 MHz
5 2000 MHz
6 2825 MHz
7 3800 MHz
8 6000 MHz
Functional Description 13
Rev 2.1