Overview
The 3G Large Depth Vector Signal Capture instrument by EnTegra Ltd,
enables UMTS Engineers to capture 3G baseband signals to disk. The
Vector Signal Capture samples I and Q at 16x chip rate (61.44MSPS),
then filters and decimates using root raised cosine filters down to
chip rate, and writes the 16 bit chip rate samples to file. The
recorded waveform can be as long as the disk system will support,
easily in excess of 3 hour’s of data. Applications include:
- Verification of receiver and transmitter designs against very
large datasets
- Conformance / Acceptance Testing
PC Based Instrument
The Vector Signal Capture Instrument (VSC) is built around a
standard Personal Computer and a bespoke DSP PCI card. The DSP card
and daughter module samples I and Q at 16x chip rate (61.44MSPS) using
14 bit analogue to converters, then filters and decimates using root
raised cosine filters down to chip rate, and writes the 16 bit chip
rate samples to file. The instrument provides an automatic method of
synchronising to the maximum effect point, and synchronising to the
start of frame. Once the required number of frames have been saved to
disk, the user may view any of the frames as either I&Q v time or I v
Q on a graph.
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The samples are stored as binary
files of 16 bit signed integers, and may be post processed by
EnTegra’s 3G Design Suite and SystemVue™ (sold separately). The PC
runs the MicroSoft Windows 2000 Operating System and the VSG is driven
via a windows application. The Instrument is available in either a
Mini Tower case or 19 inch rack mount 4U case.
Analogue or Digital Inputs
The input can either be analogue signals at -3dBm or serial OC48
via a front panel connector.
DC Offset Control
The digital samples each have DC offset correction applied which is
set under user control.
Frequency Shifted Inputs
The IQ input may be shifted in frequency by ±20MHz using a
numerically controlled oscillator, with a resolution of 0.02Hz.
10MHz Reference
The VSC can be clocked using either it’s own temperature controlled
10MHz reference or an external 10MHz reference clock. |
