Instrument Function > Modulation > Chirp Modulation > Chirp Modulation Settings
Chirp Modulation Settings

Access:

 

Select "Modulation > config... > Chirp Modulation".

 

The "Chirp Modulation" dialog contains the parameters for configuring the modulation and trigger settings.

State - Chirp Modulation

Activates/deactivates chirp modulation

Note: Any active modulation is automatically switched off when chirp modulation is activated.

The pulse generator signal is provided at the PULSE VIDEO output, the sync signal at the PULSE SYNC output.

These outputs are automatically switched on/off according to the chirp modulation state. The FM modulation signal can be output at the LF connector.

Note: Automatic Level Control is deactivated with chirp modulation.

When pulse modulation is activated, the R&S SMA deactivates ALC automatically ("ALC OFF", i.e. switches to "Sample & Hold" state).

The "Sample&Hold" state opens the ALC loop, and disables the automatic control of the output level. The level modulator is set directly.

However, to correct the output level, the R&S SMA executes a "Sample & Hold" measurement after each change of frequency or level settings.

The nominal level is ON for typically 3 ms to 5 ms after level or frequency setting, if:
  • No attenuator is fitted (frequency option R&S SMA-B103L/B106L)
  • "High Power" mode is enabled
  • "Auto" mode is enabled, and if the level is in the range of the high power, i.e. the mechanical relay bypass is switched.

The level is decreased by 30 dB during "Sample & Hold" measurement.

Remote command: 
 
Direction - Chirp Modulation

Selects the direction of the chirp modulation.

"Up"

The chirp starts with the lower frequency.

"Down"

The chirp starts with the higher frequency.

Remote command: 
 
Bandwidth - Chirp Modulation

Sets the modulation bandwidth in Hz.

The bandwidth denotes the difference between the maximum and minimum frequency. E.g. a bandwidth of 10 MHz at a center frequency of 1 GHz leads to a frequency modulation between 995 MHz and 1005 MHz.

The maximum bandwidth depends on the current RF frequency (see data sheet) . If the bandwidth is too high for the RF frequency, or the frequency is out of the bandwidth range, the R&S SMA sets the maximum bandwidth and generates an error message

Remote command: 
 
Pulse Period - Chirp Modulation

Sets the period of the generated chirp. Option R&S SMA-K23 provides a resolution of 20 ns.

Remote command: 
 
Pulse Width - Chirp Modulation

Sets the width of the generated chirp. The pulse width must be at least 1 us less than the set pulse period. Option R&S SMA-K23 provides a resolution of 20 ns.

Remote command: 
 
Compression Ratio - Chirp Modulation

Indicates the pulse compression ratio, i.e. the product of the pulse width in (s) and the bandwidth (Hz). Pulse compression increases the range resolution as well as the signal to noise ratio of pulsed signals.

Remote command: 
 
Trigger Mode - Chirp Modulation

Selects the trigger mode for chirp modulation signals.

Note: An external trigger signal is supplied via the PULSE EXT connector.

"Auto"

The chirp modulation signals are generated continuously.

"Ext Triggered"

The chirp modulation signals are triggered by an external trigger event.

"Ext Gated"

The chirp modulation signals are gated by an external gate signal.

Remote command: 
 
External Trigger Input Slope - Chirp Modulation

("Ext. Triggered" only)

Sets the polarity of the active slope of an applied trigger signal.

Note: An external trigger signal is supplied via the PULSE EXT connector.

"Positive"

The chirp modulation signals are triggered on the positive slope of the external trigger signal.

"Negative"

The chirp modulation signals are triggered on the negative slope of the external trigger signal.

Remote command: 
 
Gate Input Polarity - Chirp Modulation

(External Gate only).

Selects the polarity of the Gate signal.

Note: An external gate signal is supplied via the PULSE EXT connector.

"Normal"

The chirp modulation signals are generated while the gate signal is high.

"Inverse"

The chirp modulation signals are generated while the gate signal is low.

Remote command: 
 
External Impedance - Chirp Modulation

(External trigger or gate only)

Selects the input impedance for the external trigger and gate signal input (10 kOhm or 50 Ohms).

Remote command: 
 

 


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