Instrument Function > Modulation > Phase Modulation (PhiM) > Phase Modulation Dialog
Phase Modulation Dialog

To open the "Phase Modulation" dialog, select "Modulation > Configure > Phase Modulation" or use the MENU key under "Modulation".

In the upper section of the dialog, the modulation source is selected and the modulation switched on. The modulation source can be selected independently for the different modulation types and the LF output.

The configuration of the selected external and/or internal modulation source is performed in the lower section of the dialog (internal source only).

These settings affect all modulations which use the same modulation sources.

For a fully equipped instrument, two LF generators and a noise generator are available as internal sources.

State

Activates ɸM modulation.

Activation of ɸM deactivates frequency modulation.

Remote command: 
 
ɸM Source

Selects the source for the ɸM signal.

The source can be selected independently for the different modulation types and the LF output. The configuration of the selected external and/or internal modulation source is performed in the lower section of the menu or in the "Mod Gen" block (internal source only).

For a fully equipped instrument, two LF generators and a noise generator are available as internal sources.

"Internal"

Uses the internal LF generator as the modulation signal source for ɸM.

"External"

Uses an externally applied modulation signal.

The external signal is input via the FM/PM EXT connector.

"Internal + External"

Uses both, the internal and externally applied modulation signal.

"Ext digital"

Uses an externally applied digital modulation signal. The external signal is input via the AUX I/O connector.

Remote command: 
 
ɸM Mode

Selects the mode for the phase modulation.

"High Bandwidth"

The maximum range for modulation bandwidth is available. However, phase noise is increased for low modulation frequencies. The range for ɸM deviation is limited.

This mode is recommended for high modulation frequencies.

"High Deviation"

The maximum range for ɸM deviation is available. Phase noise is improved for low frequencies compared to the default mode. The range of modulation frequency is limited (see data sheet).

This mode is recommended for low modulation frequencies and/or high ɸM deviation.

"Low Noise"

(with option R&S SMA-B22 only)

Phase modulation with phase noise and spurious characteristics close to CW mode. The range for modulation bandwidth and PM deviation is limited (see data sheet).

If your instrument is equipped with the SynEx Assembly (part number 1413.1800.02), you can reduce the phase noise even more by setting the PLL bandwidth to "Narrow". See "Main Pll Bandwidth" and "The Configurable Main PLL Bandwidth" for details.

Remote command: 
 
ɸM Deviation

Sets the modulation deviation in RAD.

The maximum deviation depends on the set RF frequency and the selected modulation mode (see data sheet).

If the entered deviation is too high for the set RF frequency, the instrument provides the maximum value and displays an error message. The same applies, if the RF frequency is set to a value, at which the deviation cannot be determined.

The deviation of the internal source must not exceed the deviation of the external source in case of modulation source "Int+Ext".

Remote command: 
 
Internal Source

Selects the internal signal source to be used for phase modulation. The available LF generators provided in the list depend on the installed options.

"None"

Deactivates all internal modulation sources.

"LFGen1 / LFGen2"

Uses a signal generated by one of the internal LF generators as modulation signal.

"LFGen1+2"

Uses the signals of both internal LF generators for phase modulation.

You can set the LF frequency and modulation deviation separately for each generator. The sum of the deviations of the two modulation generators must not exceed the total value set with"ɸM Deviation".

"Noise"

Uses the noise signal for phase modulation, that is white noise either with Gaussian distribution or equal distribution.

This setting affects all analog modulations which use the noise generator as the internal modulation source.

See also "Noise Settings".

"LFGen1+Noise / LFGen2+Noise"

Uses a signal generated by an internal LF generator and overlaid with white noise for phase modulation.

Remote command: 
 
Deviation 1/Deviation 2

Source Internal, LFGen1+2 only

Selects the deviation for the two frequency modulation signals. The sum of the two values must not exceed the overall modulation deviation set in the upper part of the menu.

Remote command: 
 
LF Gen 1/2 Freq

Source Internal, LFGen1+2 only

Sets the frequency of the two LF generators.

Remote command: 
 
LF Gen 2 Shape

Source Internal, LFGen2 only

Selects the shape of the second LF generator signal. In case of selection Trapeze, additional settings concerning the duration of the single trapeze elements can be made (see "LF Output Dialog").

Remote command: 
 
ɸM Sensitivity

Displays the input sensitivity of the externally applied modulation signal at the FM/PM EXT input in RAD/V.

The modulation deviation entered with "ɸM Deviation""ɸM Deviation" is achieved with 1 Volt (=Upeak) of the input signal.

Note: The input voltage must not exceed 1.1 Vp otherwise modulation distortions occur.

Remote command: 
 
PhiM Ext Coupling

Selects the coupling mode ("AC" or "DC") for the external modulation signal.

Note: Coupling for external feed via input FM/PM EXT can be set independently for all modulations using the external modulation signal.

"AC"

Disconnects the DC voltage component and uses only the AC component of the modulation signal.

"DC"

Uses the modulation signal with both components, AC and DC.

Remote command: 
 
Ext. Impedance

(Source External only)

Sets the impedance for an externally applied modulation signal. Use the AM EXT connector for amplitude modulation signals, and the FM/PM EXT frequency of phase modulation signals.

You can select 50 Ohm or high (>100 kOhm).

This setting affects all analog modulations which use the external modulation signal.

Remote command: 
 
Ext ɸM Binary Format

Source External only

Selects the binary format for external digital frequency modulation (see Table "Binary data formats"). The data is input via the AUX I/O interface.

NOTICE! Risk of instrument damage. The maximum input voltage is 3.3 V dc.

Binary data formats

Scale

Example for set phase deviation = 120 DEG

Offset Binary

Two's Complement

+ full scale

120 DEG

1111….1111

0111….1111

+0.75 full scale

90 DEG

1110….0000

0110….0000

+0.5 full scale

60 DEG

1100….0000

0100….0000

+0.25 full scale

30 DEG

1010….0000

0010….0000

+ 0

0 DEG

1000….0000

0000….0000

-0.25 full scale

-30 DEG

0110….0000

1110….0000

-0.5 full scale

- 60 DEG

0100….0000

1100….0000

- 0.75full scale

- 90 DEG

0010….0000

1010….0000

- full scale + 1LSB

 

0000….0001

1000….0001

- full scale

- 120 DEG

0000….0000

1000….0000

Pin connection for input of digital PM data via AUX I/O connector

Connection

Parallel data input with 16-bit word width for digital PM modulation data.

11 - FM_DAT

FM_DATA 15 (MSB)

12 - FM_DAT

FM_DATA 14

13 - FM_DAT

FM_DATA 13

14 - FM_DAT

FM_DATA 12

15 - FM_DAT

FM_DATA 11

16 - FM_DAT

FM_DATA 10

17 - FM_DAT

FM_DATA 9

18 - FM_DAT

FM_DATA 8

19 - FM_DAT

FM_DATA 7

20 - FM_DAT

FM_DATA 6

21 - FM_DAT

FM_DATA 5

22 - FM_DAT

FM_DATA 4

23 - FM_DAT

FM_DATA 3

24 - FM_DAT

FM_DATA 2

25 - FM_DAT

FM_DATA 1

26 - FM_DAT

FM_DATA 0 (LSB)

 


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