• Conventional fixed– frequency CW pulse
The CWPulse can be used as a pulsed Doppler waveform in all the same way that a
Klystron or Magnetron system with a traditional pulse forming network would be used.
• Linear and non–linear FM chirp
The linear and non–linear FM waveforms, however, are compressed pulses that are
intended to be transmitted by a wide– bandwidth Klystron/TWT/SolidState amplifier.
Tx Waveform – 0 :CWPulse, 1:LinFM, 2:NLFM : 2
The RVP900 internal APIs permit developers to create arbitrary waveforms for
transmission. The types listed above are the out–of–the–box selections that are standard
on RVP900 processors.
The next questions select the bandwidth and pulse length of the Tx waveform. The
bandwidth value represents the true spectrum width of the complete waveform, that is,
including all the
eects of the frequency modulation and amplitude modulation used by the
waveform. A spectrum analyzer (or the RVP900 Ps plot) shows an overall spectrum width
equal to this desired value.
Similarly, the pulse length value represents the entire time duration of the waveform,
including whatever amplitude modulations may be included at the tails.
Waveforms are synthesized by the RVP900 using a 16-bit TxDAC followed by an analog
bandpass filter centered at the midpoint of the IF interval. The analog filter is necessary
removes out-of-band components from the TxDAC, but has a side
eect of introducing a
bandwidth limitation within the IF passband. The result is that the shape of very short pulses
(on the order of 100 nanoseconds) is dominated by the impulse response of the analog filter
rather than by the exact digital synthesis.
In practice the Tx pulse width should be longer than 300 nanoseconds for that the
final
analog signal to be a faithful reproduction of the intended waveform.
The Tx waveform is normally synthesized with its center lined up with range 0. If the radar's
high–power amplifier had zero delay, this would serve to define the middle of the transmit
pulse as range zero, which is the usual RVP900 convention. This oset question is provided
so that the Tx output waveform can be shifted in time to compensate for whatever delays
are present in the radar's IF/RF electronics.
Bandwidth of transmit pulse: 3.25 MHz Pulselength of transmit pulse: 15.00
usec
Zero offset of transmit pulse: 0.00 usec
Chapter 5 – TTY Non-volatile Setups
123
To Next Page
Loading...