Center Frequency

Sets the frequency that corresponds to the horizontal center of the graticule (when frequency Scale Type is set to linear). While adjusting Center Frequency, Span is held constant, which means that both Start Freq and Stop Freq will change.

Pressing Center Frequency sets the frequency entry mode to Center/Span. In Center/Span mode, the center frequency and span values are displayed below the graticule, and the default active function in the Frequency menu is Center Frequency. In the Start/Stop annotation mode, Start Freq and Stop Freq are displayed below the graticule instead of Center Frequency and Span.

Pressing Center Frequency also sets the frequency entry mode to Center/Span. In Center/Span mode, the center frequency and span values are displayed below the graticule, and the default active function in the Frequency menu is Center Frequency.

When Display Scale Type is set to LOG, pressing Center Frequency sets the frequency that corresponds to the arithmetic mean of the start frequency and stop frequency, which is not at the horizontal center of the graticule.

The center frequency setting is the same for all measurements within a Mode, that is, it is Meas Global. Some Modes are also able to share a Mode Global center frequency value. If this is the case, the Mode has a Global tab in its Meas Setup menu.

Center Frequency sets (and queries) the center frequency for the currently selected input. If your instrument has multiple inputs, and you select another input, Center Frequency changes to the value for that input. SCPI commands are available to directly set Center Frequency for a specific input (see RF Center Frequency and Ext Mix Center Freq).

Center Frequency is remembered as you go from input to input. Thus, you can set a Center Frequency of 10 GHz with the RF Input selected, change to BBIQ and set a Center Frequency of 20 MHz, then switch to External Mixing and set a Center Frequency of 60 GHz. When you return to the RF Input, Center Frequency reverts to 10 GHz; back to BBIQ and it is 20 MHz; back to External Mixing and it is 60 GHz.

Remote Command

[:SENSe]:FREQuency:CENTer <freq>

[:SENSe]:FREQuency:CENTer?

Example

Set Center Frequency to 50 MHz:

:FREQ:CENT 50 MHz

Increment Center Frequency by the value of CF Step:

:FREQ:CENT UP

Return the current value of Center Frequency:

:FREQ:CENT?

Notes

Sets the RF, External Mixing or I/Q Center Frequency depending on the selected input:

  • For RF input it is equivalent to :FREQ:RF:CENT

  • For I/Q input it is equivalent to :FREQ:IQ:CENT

  • For External Mixer it is equivalent to :FREQ:EMIX:CENT

Preset and Max values depend on Hardware Options

If no terminator (for example, MHz) is sent, the terminator Hz is used. If a terminator with unit other than frequency is used, an invalid suffix error message is generated

Dependencies

Center Frequency can be limited by Start Freq or Stop Freq limits, if Span is so large that start or stop reach their limits

Couplings

When operating in “swept span”, any value of Center Frequency or Span that is within the frequency range of the instrument is allowed, if the value is being set through the front panel numeric key pad or the SCPI command. The other parameter is forced to a different value if needed, to keep Start and Stop Frequencies within the instrument’s frequency range

Coupling between center frequency and span: numeric (keypad) entries are treated differently than changing the value using the step keys (Up/Down Arrows) or the knob. Similarly, for remote operation, sending a numeric frequency value is treated differently than the UP|DOWN keywords:

  • Numeric entries (keypad or remote): Any value of Center Frequency or Span (within the frequency range of the instrument) is allowed. The other parameter is changed, as necessary, to keep the Start Freq and Stop Freq within the instrument frequency range

  • Knob or Step keys (up/down arrows) or UP|DOWN keywords: The value of the parameter being changed (Center Frequency or Span) is limited so the other parameter is not forced to a new value. Thus, if only the step keys and knob are used, you can return to the initial Center Frequency and Span by changing only the current parameter

Note that, since out-of-range Start Freq and Stop Freq are never allowed, markers and trace math work correctly without requiring any special handling for out-of-range conditions

Preset

Depends on instrument maximum frequency, mode, measurement, and selected input

See Center Frequency Presets and Ext Mix Center Freq

State Saved

Saved in instrument state

Min/Max

Depends on instrument maximum frequency, mode, measurement, and selected input

See Center Frequency Presets and Ext Mix Center Freq

Annotation

Center <value> appears in the lower left corner of the display

Status Bits/OPC dependencies

Non-overlapped

The following table provides the Center Frequency Presets for the Spectrum Analyzer mode, and the Max Freq, for the various frequency options:

Freq Option

CF after Mode Preset

Stop Freq after Mode Preset

Max Freq

(can't tune above)

503 (all but CXA)

1.805 GHz

3.6 GHz

3.7 GHz

503 (CXA)

1.505 GHz

3.0 GHz

3.08 GHz

507 (all but CXA)

3.505 GHz

7.0 GHz

7.1 GHz

507 (CXA)

3.755 GHz

7.5 GHz

7.58 GHz

508 (all but MXE)

1.805 GHz

3.6 GHz

8.5 GHz

508 (MXE)

4.205 GHz

8.4 GHz

8.5 GHz

513

6.805 GHz

13.6 GHz

13.8 GHz

526 (except CXA and MXE)

13.255 GHz

26.5 GHz

27.0 GHz*

526 (CXA)

13.255 GHz

26.5 GHz

26.55 GHz

526 (MXE)

1.805 GHz

3.6 GHz

27.0 GHz

532

16.005 GHz

32.0 GHz

32.5 GHz

540

20.005 GHz

40.0 GHz

40.5 GHz

543

21.505 GHz

43.0 GHz

43.0 GHz

544

22.005 GHz

44.0 GHz

45.0 GHz

550

25.005 GHz

50.0 GHz

52 GHz

F03 (CXA-m)

1.505 GHz

3.0 GHz

3.08 GHz

F07 (CXA-m)

3.755 GHz

7.5 GHz

7.575 GHz

F13 (CXA-m)

6.805 GHz

13.6 GHz

13.8 GHz

F26 (CXA-m)

13.255 GHz

26.5 GHz

26.55 GHz

504 (M9421A, M8920A)

2.145 GHz

3.88GHz

3.88 GHz

506 (M9421A, M8920A)

3.245 GHz

6.08GHz

6.08 GHz

F06 (M9410A/11A)

1.0 GHz

 6.08 GHz 6.08 GHz

F06 (M9415A)

 1 GHz 1.08 GHz

6.6 GHz

F08 (M9415A)

 1 GHz 1.08 GHz

8.6 GHz

F12 (M9415A)

 1 GHz 1.08 GHz

12.9 GHz

*For option 526, the Max CF in RTSA is 26.999999995 GHz.

N9041B Center Freq Presets

Input

CF after Mode Preset

Stop Freq after Mode Preset

Max Freq

(can't tune above)

Input 1, all models

25.005 GHz

50.0 GHz

52 GHz

Input 2, opt 585

42.505 GHz

85.0 GHz

86 GHz

Input 2, opt 590

45.005 GHz

90.0 GHz

92 GHz

Input 2, opt 5CX

55.005 GHz

110.0 GHz

110 GHz

Input 2, CXA and MXE

Model

CF after Mode Preset

Stop Freq after Mode Preset

Max Freq

(can't tune above)

CXA opt C75

0.7505 GHz

1.5 GHz

1.58 GHz

MXE

505 MHz

1 GHz

1.000025 GHz

Tracking Generator Frequency Limits (CXA only)

Tracking Generator Option

Min Freq

(clips to this freq when turn TG on and can’t tune below while TG on)

If above this Freq, Stop Freq clipped to this Freq when TG turned on

Max Freq

(can't tune above) while TG on

T03

9 kHz

3.0 GHz

3.08 GHz

T06

9 kHz

6.0 GHz

6.05 GHz

Tracking Generator Frequency Limits(CXA-m only)

Tracking Generator Option

Min Freq

(clips to this freq when turn TG on and can’t tune below while TG on)

If above this Freq, Stop Freq clipped to this Freq when TG turned on

Max Freq

(can't tune above) while TG on

T03

2 MHz

3.08 GHz

3.08 GHz

T07

2 MHz

7.575 GHz

7.575 GHz

T13

2 MHz

13.8 GHz

13.8 GHz

T26

2 MHz

26.55 GHz

26.55 GHz

VXT Models with Radio Heads/CIU Frequency Range

The following table shows the Center Frequency Presets and Range for VXT modes with Radio Heads/CIU.

Products with Radio Heads/CIU

Preset

Start frequency

Stop frequency

M9421A + CIU

6 GHz

5.9 GHz

12 GHz

M9410A + CIU

6 GHz

5.9 GHz

12 GHz

M9410A + CIU + RRH

25 GHz

24.25 GHz

43.5 GHz

Specifies the RF Center Frequency. Sets the center frequency to use when the RF input is selected, even if the RF input is not the input that is selected at the time the command is sent. Note that Center Frequency in the Frequency menu on the front panel always applies to the currently selected input.

Remote Command

[:SENSe]:FREQuency:RF:CENTer <freq>

[:SENSe]:FREQuency:RF:CENTer?

Example

:FREQ:RF:CENT 30 MHz

:FREQ:RF:CENT?

Notes

This command is the same in all Modes, but the parameter is Measurement Global. So, the value is independent in each Mode and common across all the measurements in the Mode

Dependencies

If the electronic/soft attenuator is enabled, any attempt to set Center Frequency such that the Stop Frequency would be >3.6 GHz fails and results in an advisory message. If the equivalent SCPI command is sent, this same message is generated as part of a “-221, Settings conflict” warning

If Source Mode is set to Tracking, and the Max or Min Center Frequency is therefore limited by the limits of the source, a warning message is generated, “Data out of range; clipped to source max/min” if these limits are exceeded. Note that for an external source, these limits can be affected by the settings of Source Numerator, Source Denominator, and Power Sweep

Preset

See Center Frequency Presets

State Saved

Saved in instrument state

Min

Instrument Types

Value

VXT model M9421A

55.000005 MHz

VXT models M9410A/11A/15A/16A

330.000005 MHz

6.505 kHz with Option LFE

VXT model M941xE (VXT model M941xA associated with M9471A)

RF port on S9110E

330.000005 MHz

750.005 kHz with Option LFE

RRH Port on S9110E

22.700000005 GHz

M8920A

80.005 kHz

All other instruments

Unless Source Mode is set to Tracking, in which case it is limited by the minimum frequency of the Source

–79.999995 MHz

 

Max

See table above. Basically, instrument maximum frequency – 5 Hz. Note that, if the Source Mode is set to Tracking, the effective instrument maximum frequency may be limited by the source maximum frequency

If the knob or step keys are being used, also depends on the value of the other three interdependent parameters: Span, Start Frequency and Stop Frequency

Specifies the External Mixer Center Frequency. Sets the center frequency to use when the External Mixer is selected, even if the External Mixer input is not the input which is selected at the time the command is sent. Note that the Center Frequency function in the Frequency menu on the front panel always applies to the currently selected input.

Remote Command

[:SENSe]:FREQuency:EMIXer:CENTer <freq>

[:SENSe]:FREQuency:EMIXer:CENTer?

Example

:FREQ:EMIX:CENT 60 GHz

:FREQ:EMIX:CENT?

Notes

This command is the same in all Modes, but the parameter is Measurement Global. So, the value is independent in each Mode and common across all the measurements in the Mode

Couplings

When you return to External Mixing after using one of the other inputs (for example, RF), you return to the settings that you had when you left External Mixing. So, you return to the band you were in with the Center Frequency that you had. However, Span is not an input-dependent parameter, so it does not change. Therefore, the instrument comes back with the Span from the previous input, limited as necessary by the current mixer setup

Preset

When Mode Preset is performed while in External Mixing, the start frequency of the current Mode is set to the nominal Min frequency of the lowest harmonic range in the Harmonic Table for the current mixer setup. Similarly, the stop frequency of the current Mode is set to the nominal Max frequency of the highest harmonic range in the Harmonic Table. Center Frequency thus presets to the point arithmetically equidistant from these two frequencies

Note that, if the current measurement has a limited Span available to it, and cannot achieve the span shown in the table (Span = Stop Freq – Start Freq), the instrument uses the maximum span that the measurement allows, and still sets Center Frequency to the midpoint of the Start Freq and Stop Freq values in the Harmonic Table

When Restore Input/Output Defaults is performed, the mixer presets to the 11970A, whose Start and Stop frequencies are 26.5 and 40 GHz respectively. The center of these two frequencies is 33.25 GHz

Therefore, after Restore Input/Output Defaults, if you switch to External Mixing and do a Mode Preset while in the Spectrum Analyzer Mode, the resulting Center Frequency is 33.25 GHz

State Saved

Yes

Min

The minimum frequency in the currently selected mixer band + 5 Hz

Max

The maximum frequency in the currently selected mixer band – 5 Hz

If the knob or step keys are being used, also depends on the value of the other three interdependent parameters Span, Start Freq and Stop Freq