Tektronix WCA200A, Руководство пользователя

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Product Overview
WCA230A & WCA280A User Manual
1- 7
Converts the RF signal, input through the front-panel INPUT connector, into a
20 MHz IF signal. This converter processes signals up to 3 GHz for WCA230A
and 8 GHz for WCA280A by IF conversions in three stages. A 10 MHz
oscillator provides a high-accuracy reference for all stages of IF conversion. The
converter also adjusts signals for A/D conversion using a low-noise amplifier,
fine-tuning attenuator, and anti-alias filter. The output signal from the down
converter is sent to the IF sampling A/D converter described below.
The IF analog output from the down converter enters the A/D converter through
the fine-tuning attenuator, low-noise amplifier, and anti-alias filter, to be
converted into a digital signal. The sampling rate of the A/D converter is
51.2 MHz with a resolution of 14 bits.
The digital down converter splits the real signal from the A/D converter into
complex (I and Q) components and limits the frequency span of the resulting
signal.
With Option 03, you can enter I and Q signals at this point in the block diagram.
The down converter performs span and center frequency fine-tuning. This
converter consists of two primary stages. In the baseband, the first stage converts
a 0 to 15 MHz real signal into a complex signal of
±
7.5 MHz. The second stage
converts frequency to set any center frequency.
A decimating filter between stages changes the span by effectively reducing the
sampling rate. A 503 tap FIR filter and four stage comb filter allows extremely
accurate filtering with minimal spurious emissions.
The data streams from the digital down converter are then divided into frames
and saved in data memory.
Option 02 provides a real-time digital trigger function that monitors the
frequency spectrum for the occurrence of specific events. A trigger mask is used
to set conditions for trigger.
The FFT processor performs high-speed calculations to create extended trigger
signals. The FFT processor performs 1024-point complex FFT at high speed to
create extended trigger signals. The FFT processor consists of an input buffer,
FFT calculation DSP, output buffer, and timing control circuit. Performing a
1024-point complex FFT at 12,500 times per second allows the trigger to operate
in real time in spans up to 15 MHz.
Because the trigger comparator is continuously operating at the maximum rate,
no events will be missed. The pre-trigger and post-trigger positions can be set as
needed; events before and after the trigger event can be measured.
3 GHz / 8 GHz
Down Converter
IF Sampling A/D Converter
Digital Down Converter
FFT/Extended Trigger
(Optional)