IF Phase Linearity Adjustment

The associated IF Phase Linearity Check is located under the Utilities Menu. It is recommended that the IF Phase Linearity Check Utility be performed after the IF Phase Linearity Adjustment is performed.

This adjustment applies to the following models and options:

With options:

This adjustment should only be performed on instruments that are equipped with Option B2X (255 MHz IF Bandwidth) or B5X (510 MHz IF Bandwidth) or Option H1G (1GHz IF Bandwidth).

If Option MPB (Preselector Bypass) is installed, the adjustment will be performed on band 1 through 6. Option FBP (Full Bypass Path) is the combination of both MPB and Option LNP (Low Noise Path). If Option FBP is installed, the adjustment will be repeated and corrections will be generated and stored. This adjustment is very limited if Option MPB/FBP is not installed in the instrument.

The goal of this adjustment is to generate corrections for the IF Phase Error across the IF Bandwidth. Option MPB is necessary is because the YTF is a tunable bandpass filter with a nominal bandwidth of 30 MHz to 50 MHz. The bandwidth of the YTF will band limit the IF Frequency Response.

To summarize the Option MPB dependency:

Option MPB installed:

Option B2X: Adjust for Bands 0, 1, 2, 3, 4, 5, 6

Option B5X: Adjust for Bands 0, 1, 2, 3, 4, 5, 6

Option MPB NOT installed:

Option B2X: Adjust for band 0 only

Option B5X: Adjust for band 0 only

 

A comb generator outputs a series of comb teeth that start at 9.765625 MHz (or whatever the source frequency is chosen) and step in 9.765625 MHz increments to 50 GHz. The comb teeth are assumed to be phase coherent across the IF bandwidth of interest. The comb generator will output a burst of comb teeth, and the DUT will be triggered to perform a spectrum measurement. The trace will contain a series of bursts spaced in 0.1024 us (or 1/9.765625 MHz) steps. The phase angle of each individual comb tooth will be read from the DUT with the CALC:SPEC:MARK1:PHAS? command.

Band

IF Path

Span (MHz)

Tone Space (MHz)

Tone Count

0 to 6

B2X

253.90625

9.765625

27

0 to 4

B5X

507.8125

9.765625

53

5, 6

B5X

507.8125

19.53125

27

0 to 4

H1G

996.09373

9.765625

103

5, 6

H1G

996.09373

19.53125

52

 

This will result in an array that is phase angle (in radians) vs offset frequency. The phase angle will be wrapped such that an angle greater than Pi (radians) will be a negative angle. The negative phase angles will be converted to positive values, for instance –(Pi/2) will be converted to (3Pi)/2. The phase angles will be unwrapped by adding 2*Pi each time the angle crosses zero radians.

Once the phase angle has been unwrapped, a regression line will be calculated through the data. The phase for each comb tooth will be normalized to the regression line to generate the comb phase error. The Phase Response can be described by an Nth order Fourier series.

The an term is the real component, and the bn term is the imaginary component.

Where FS is the sampling frequency (300 MHz for B2X, or 600 MHz for B5X). Fn is the comb offset frequency. A matrix will be created with n = 10.

  • B2X Note: If B5X is installed, the 255 MHz IF Path does not appear as an IF Path choice. Only the 510 IF Path will show as the path choice. The instrument firmware automatically selects the 255 MHz path if the span is set to 255 MHz or less.

  • B1G Note: If H1G is installed then B5X cannot be installed. The reason is that Option B5X is actually two parallel 255 MHz IF boards. The two 255 MHz IF boards work together to create a 510 MHz IF bandwidth. Option B1G requires one of the option slots, so the second 255 MHz IF is removed to make room for the H1G board. So, if H1G is installed, then B2X will be optioned as well.

Click here for troubleshooting.

Required Test Equipment

Test Equipment

Recommended Model Number

RF Signal Generator

PSG Models
(see equipment list)

Comb Generator

U9391G Option FFM

DC Power Supply

U8001A

Attenuator, 6 dB fixed

8490D Option 006

Cable, 2.4 mm (m) to 2.4 mm (f)

8120-6164

Cable, BNC (m) to BNC (m)

  • 3 required

8120-1840

Cable assembly for connecting power supply to comb generator

U9391-20013

Adapter, 2.4 mm (f) to 3.5 mm (m)

11901D

Adapter, 2.4 mm (f) to 3.5 mm (f)

  • For Option C35

11901B

Adapter, Type-N (m) to 2.4 mm (f)

  • For options ≤ 526

11903D

Adapter, 2.4 mm (f) to 2.4 mm (f)

  • For options > 526

11900B

Adapter, SMA (m) to BNC (f)

1250-1200

Connection Setups

  • It is recommended to place a support (i.e. foam pad) under the comb generator to provide a level connection to the RF Input of the DUT and avoid putting stress on the connector.

  • The USB cable from the comb generator must be connected to the USB of the PC where the comb generator's SFP (Soft Front Panel) software is installed. The software will control the on/off function of the comb generator.

  • When the power supply is first powered up, you should notice the signal on the DUT jump slightly, and then change again when the comb generator is turned on via the SFP.

  • Option H1G requires a different rear-panel setup as shown in the illustration below.

Setup for N9030B and N9021B

Setup for N9040B