Signal Generator Settings

Clicking Project in the tree view displays the Signal Generator Settings table in the parameter view of the main window.

Basic

Basic Arb

Marker Setting

IQ Adjustment Setting

Trigger Setting

AWGN Setting

These parameters are sent to the signal generator when you click Download. They affect how the signal generator outputs the waveform, but have no affect on waveform generation. You can also change these settings either from the instrument's front panel or using SCPI commands. For more detailed information on setting these parameters, see ESG, PSG, or MXG product information.

If you are using an N5162A MXG ATE or N5182A MXG signal generator, please note the following differences in signal generator settings. For specific details, refer to the parameter definitions below.

BBG Reference, Ext BBG Ref Frequency, IQ Mod Filter, and IQ Output Filter do not apply although they are not grayed out in the software.
The range allowed in the software for IQ Gain Balance Source 1 and IQ Offset is wider than allowed in the MXG/MXG ATE and thus may generate clipping errors if the allowed value is exceeded.
The range allowed in the software for IQ Timing Skew, IQ Delay, and C/N ratio is smaller than the range allowed in the MXG/MXG ATE. The values may be extended using the front panel keys on the MXG (or MXG ATE web interface) or by sending SCPI commands from software to control the MXG/MXG ATE.

1. Basic

Frequency

Use this cell to set the frequency (Hz) at which the signal generator plays the waveform. This frequency value also appears in the status bar at the bottom of the main window. The range varies from 10 MHz to 44 GHz depending on the signal generator being used.

Amplitude

Use this cell to set the power level (dBm) at which the signal generator plays the waveform. It refers to either the average power level of the bursts (excluding the preamble) or to the preamble power level, as indicated by the Amplitude Reference. The range is from –135.00 to 25.00, (step size 0.02) dBm. The default is –10 dBm.

Amplitude Reference

Use this cell to select the portion of the frame, either FCH/Burst or Preamble, that the power level (dBm) is referencing. By default, the signal generator amplitude setting refers to the average power level of the FCH/Burst. However, the preamble power level will always be 3 dB higher than the level of the rest of the burst as defined in the IEEE 802.16-2004 standard. If you create a waveform that only has a preamble, select Preamble as the Amplitude Reference.

The Amplitude Reference also determines the portion of the waveform that is used by the signal generator for ALC leveling. Since the RCE (EVM) of the signal can vary based on the data in the waveform, choosing Preamble as the Amplitude Reference may give better results in some cases.

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2. Basic Arb

Sampling Clock

The sampling clock frequency of the signal generator is automatically calculated as [Sampling Clock] = floor(n * Bandwidth / 8000) * 8000 * OSR. Values range from 1.44 MHz to 32 MHz.

Runtime Scaling (%)

Use this parameter to reduce the overshoot associated with the digital-to-analog convertor (DAC) interpolation filter. At 100 percent, some overshoot may occur; therefore the default setting is 85 percent. Further scaling may help to decrease DAC over-range occurrences.

I/Q Mod Filter

Use this cell to set the I/Q modulation reconstruction filter bandwidth on the signal generator. The bandwidth of the baseband signal (1/2 the RF bandwidth) should dictate the minimum reconstruction filter bandwidth you choose. Depending on the oversampling ratio and where the image frequencies appear, you may want to select a wider bandwidth.

AUTO	automatically chooses a filter based on the active digital modulation settings.
2.1 MHz	selects a 2.1 MHz filter.
40 MHz	selects a 40 MHz filter.
Through (50 MHz)	selects a 50 MHz filter.

This parameter does not apply to the N5162A MXG ATE or N5182A MXG signal generator although it is not grayed out in the software. Any settings will be ignored.

I/Q Output Filter

Use this cell to set the I/Q modulation reconstruction filter bandwidth on the signal generator for the analog I and Q signals routed to the rear panel BNC output ports and does not affect the modulated RF signal. The bandwidth of the baseband signal (1/2 the RF bandwidth) should dictate the minimum reconstruction filter bandwidth you choose. Depending on the oversampling ratio and where the image frequencies appear, you may want to select a wider bandwidth.

AUTO	automatically chooses a filter based on the active digital modulation settings.
40 MHz	selects a 40 MHz filter
Through (50 MHz)	selects a 50 MHz filter

This parameter does not apply to the N5162A MXG ATE or N5182A MXG signal generator although it is not grayed out in the software. Any settings will be ignored.

Modulation Atten Mode

Use this cell to set the modulation attenuator mode for the I/Q modulator to either automatic or manual.

AUTO	uses an attenuation value pre-selected for optimum performance.
Manual	applies the value set for Modulation Atten.

Modulation Atten

Use this parameter to reduce the signal level driving the I/Q modulation block. Adjusting the attenuation may reduce signal distortion and improve the overall dynamic range. The default setting is 6 dB attenuation. The range is 1 to 40 dB (step size 0.01 ).

High Crest Mode

Use this parameter to reduce the automatic leveling control (ALC) vernier level by 7.5 dB, allowing the signal generator to process these signals with less distortion and improved EVM. For crest factors higher than 4 dB, I/Q drive levels should be reduced by 1 dB for each dB above that level. In high crest mode, the maximum output level is reduced and power level accuracy is degraded.

On	sets high crest mode on for waveforms with high crest factors.
Off	sets high crest mode off.

BBG Reference

Use this cell to set the time base reference for the signal generator's baseband generator.

This parameter does not apply to the N5162A MXG ATE or N5182A MXG signal generator although it is not grayed out in the software. Any settings will be ignored.

Internal	baseband generator uses an internal reference clock (10 MHz) as its time base.
External	uses an external reference clock as the time base. If an external reference is used, it should be connected to the signal generator prior to downloading waveform and instrument settings.

Ext BBG Ref Frequency

Use this cell to set the time base reference frequency for the signal generator's baseband generator. The default value is 10 MHz. The range is 250 kHz to 100 MHz.

This parameter does not apply to the N5162A MXG ATE or N5182A MXG signal generator although it is not grayed out in the software. Any settings will be ignored.

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3. Marker Setting

RF Blanking

RF blanking turns off the RF output signal during specific conditions determined by markers. This parameter assigns a specific marker to activate RF blanking. The automatic leveling control (ALC) hold is automatically enabled during output blanking. Selecting NONE disconnects all markers from RF blanking. Selecting UNSPecified allows current signal generator settings sent to the signal generator for this parameter to remain valid.

When RF blanking is enabled, the marker polarity must be set to positive or the wanted RF signal will be blanked, resulting in no RF output from the signal generator.

The software uses Marker3 to control the RF blanking and Marker4 for ALC settings. These settings should NOT be changed unless you are knowledgeable of how the changes will affect the waveform playback. See also Marker1-4 in Project Property.

ALC Active

This cell assigns a specific marker to activate the ALC function. When enabled, the ALC constantly monitors and controls the RF output power of the signal generator. Selecting NONE disconnects all markers from ALC. Selecting UNSPecified allows current signal generator settings for this parameter to remain valid.

The ALC circuit cannot properly handle some modulation conditions, leading to output power level errors. In these conditions, turning the ALC off and using the signal generator power search function can achieve better power level accuracy.

Marker1-4 Polarity

This cell sets the active polarity of Marker1-4. You can select either positive or negative. The default value is positive.

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4. IQ Adjustment Setting

IQ Adjustment

This cell toggles the operating state of the I/Q adjustments. When this is on, the values entered for the I/Q gain balance, quadrature angle adjustment, I offset, and Q offset are applied to the I and Q signals.

IQ Gain Balance Source 1

This cell changes the I to Q balance for the Source 1 selection. For example, if you enter a value of 1 dB, the I signal will have 1 dB more amplitude than the Q signal. Use the gain balance to remove imperfections in I and Q or introduce calibrated impairments. The range is –4 dB to 4 dB.

When using an MXG/MXG ATE, the value allowed by the software (± 4dB) is greater than the range allowed in the MXG/MXG ATE (limited to ± 1dB). Using a wider range than allowed will display a clipping error message (data out of range).

I Offset

For standard I/Q, this sets an origin offset for standard in-phase signals. An offset of 100% is equivalent to 500 mV DC at the front panel I input connector. The offset is used to remove imperfections in the in-phase signal or to introduce calibrated impairments.

When using this setting to minimize the LO feedthrough signal, optimum performance is achieved when the adjustment is made after any other I/Q path adjustments. If other adjustments are made after minimization is performed, the LO feedthrough signal may increase. The range is –50% to 50%.

When using an MXG/MXG ATE, the value allowed by the software (± 50%) is greater than the range allowed in the MXG/MXG ATE (limited to ± 20%). Using a wider range than allowed will display a clipping error message (data out of range).

Q Offset

This cell adjusts the amplitude level of the quadrature-phase signals. The setting appears as a percentage of full scale for standard I/Q and as an offset voltage for wideband I/Q.

Quadrature Angle Adjustment

This cell adjusts the phase angle between the I and Q vectors. When the quadrature angle is zero, the phase angle is 90 degrees. Positive angle adjustment increases the angle from 90 degrees while negative adjustment decreases the angle from 90 degrees, The range is –10 to 10 degrees, minimum increment of 0.01 degree.

IQ Timing Skew

This cell inputs skew changes to the I and Q paths. A positive value delays the I signal relative to the Q signal, and a negative value delays the Q signal relative to the I signal. The range depends on the sampling clock.

When using an MXG/MXG ATE, the range may be extended using the front panel keys on the MXG (or MXG ATE web interface) or by sending SCPI commands to the MXG/MXG ATE depending on the sample clock rate.

IQ Delay

This cell sets the IQ delay from triggers and markers in nanoseconds. The range depends on the sampling clock.

When using an MXG, the range may be extended using the front panel keys on the MXG (or MXG ATE web interface) or by sending SCPI commands to the MXG/MXG ATE depending on the sample clock rate.

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5. Trigger Setting

Trigger Type

This cell selects the triggering mode.

Continuous	selects the continuous triggering mode, which enables the signal generator to repeat the modulating signal indefinitely until you turn off the modulation format, change triggers or select another waveform.
Single	sets up a waveform to play once after receiving a trigger. See Retrigger Mode to configure the waveform's response to triggers.
Gated	sets the signal generator to the gated trigger mode, which causes the waveform (modulating signal) to repeatedly start and stop in response to an externally applied trigger signal. To use the gated trigger mode, you must also select External.
Segment Advance	controls the way the signal generator plays segments within a sequence. This includes determining whether a segment plays once or continuously, and when the sequence advances to the next segment. See also Segment Advance Mode.

Trigger Source

This cell adjusts the trigger source applied to the PATT TRIG IN or AUX I/O connectors.

Trigger Key	selects the front panel hardkey as the trigger source. After making this selection, press the Trigger hardkey to trigger a waveform.
Bus	enables the sending of a command through the GPIB, LAN or AUXILIARY IO (RS-232) input connector to trigger a waveform.
External	causes a waveform to trigger from an externally supplied trigger signal.

External Source

This cell selects the rear-panel input for the external trigger signal. External must be selected as the trigger source.

Patt Trig in 1	selects the PATTERN TRIG IN rear-panel BNC connector
Patt Trig in 2	selects the AUXILIARY I/O rear panel connector

External Trigger Polarity

This toggles the polarity of the TTL signal at the rear panel TRIGGER OUT connector.

Pos	The trigger out signal is asserted high (+ 5.0 V) at the start of the swept-sine modulation sweep and low (0 V) when the sweep ends.
Neg	Neg reverses the polarity, so that the trigger out signal is low (0.0 V) at the start of the swept-sine modulation sweep and high (+ 5.0 V) when the sweep ends.

External Delay

This cell turns the external trigger delay off or on. The selection is active only after selecting External as the trigger source.

External Delay Time

This cell sets the amount of time to delay the signal generator's response to an external trigger. The delay is a path (time) delay between when the signal generator receives the trigger and when it responds to the trigger.

Continuous Mode

This cell selects the waveform's response to triggers when Continuous is the trigger mode (continuous waveform transmission.)

Free Run	immediately triggers when you turn the format on
Trigger & Run	waits for and starts on the first trigger; ignores subsequent triggers.
Reset & Run	waits for and starts on the first trigger; resets and plays on a subsequent trigger.

Retrigger Mode

This cell configures the waveform's response to triggers while using the single trigger mode. The response selections determine whether the waveform accepts a trigger during playback, and if it does, how it responds to that trigger.

Off	causes the waveform to ignore the triggers during playback.
On	causes a waveform to accept a trigger during payback and to restart after the current play finishes.
Immediate	causes a waveform to accept a trigger during playback and to restart immediately after receiving a trigger.

Segment Advance Mode

This cell configures how play moves from segment to segment within a waveform sequence.

Single	causes a segment to play once and wait for a trigger before the sequence advances to the next segment.
Continuous	causes a segment to play continuously until receiving another trigger. Upon receiving the trigger, the sequence advances to the next segment, which then plays continuously.

Trigger Gate Active

This cell sets the trigger active state for the gated trigger mode.

Gate Active	Trigger Signal State	Description
High	High	Waveform file stops playing.
High	Low	Waveform file plays.
Low	High	Waveform file plays.
Low	Low	Waveform file stops playing.

6. AWGN Setting (requires Option 403)

AWGN State

This cell enables or disables adding real-time, non-repeating additive white gaussian noise (AWGN) to the carrier being modulated by the waveform being played. When the AWGN State is enabled, the software automatically sets the following default parameters: RF Blanking: NONE, Oversample Ratio: 2, and Noise Bandwidth Factor: 1.

C/N Ratio (dB)

This cell selects the noise power to be applied to a waveform. The carrier power is defined as the total modulated signal power before noise power is added. The noise power is the in-channel noise power. A positive value makes C larger than N. The range is –30.00 to 30.00 dB.

When using an MXG/MXG ATE, the range may be extended to ± 100 dB, if needed, using the front panel keys on the MXG (or MXG ATE web interface) or by sending SCPI commands to the MXG/MXG ATE.

Noise Bandwidth Factor

This cell enables you to set the flat noise bandwidth for the applied real-time noise. When AWGN State is enabled, the software sets the following default parameters: RF Blanking: NONE, Oversample Ratio: 2, and Noise Bandwidth Factor: 1. The noise bandwidth is at least 0.8* Fs* OSR* NBWF. Using a noise bandwidth factor of 2 is not recommended due to loss of signal performance.

Flat Noise BW

This cell displays the noise bandwidth (MHz) that has flat power level.

Carrier Power

This cell displays the carrier amplitude in dBm. When FCH/Burst is selected in the Amplitude Reference, the burst power will be (C/N) dB higher and the preamble power (3 + C/N) dB higher than the in-channel noise power. If AWGN State is off, the carrier power is the same as the amplitude.

In-Channel Noise Power

This cell displays the in-channel noise amplitude [dBm]. In-channel noise power is the entire noise power inside the bandwidth (MHz).

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Related Websites

ESG product information

PSG product information
MXG product information

IEEE 802.16-2004 standard