How to Select a PNA IFBW with Performance Comparable to an 8510

How to select a PNA IFBW with performance comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

Purpose of IFBW and Averaging Improve signal-to-noise Noise reduction reducing IFBW increasing averaging Corrupting signals are reduced too Spurs, TOI, ...

IFBW and averaging achieve the same result Averaging factor reduces 8510 noise level Defined by Averaging factor Each measured data point receives the same weight Trace Averaging function Equal weighting in 8510 Measured data points - n averages Each point on an 8510 receives the same weight in the averaging function. By comparison, IFBW on a PNA reduces noise in the same way.

IFBW and averaging achieve the same result IFBW reduction lowers PNA noise level IFBW defined by number of taps (averages) & shape factor or measured data point weighting Trace DSP IFBW function (averaging) shape factor (weighting) Measured data points - n taps (averages) Taps and averaging are the same thing. There is also a shape factor or weighting applied to the point. You can see a difference in the weighting function for the PNA. The weighting on the PNA is fairly minor. The x-axis on the weighting function is time. It is NOT frequency. You are looking at one frequency point on the trace. You take 1024 points at that one frequency. The first three and last three points are weighted differently. The purpose of weighting is to influence the reject band of the filter. A fairly minor effect at narrow bandwidths. It is significant at 10 kHz or wider IFBWs. The IFBW setting dictates number of points measured at each frequency point, and it dictates the shape factor.

8510 & PNA IF filter plots When you sweep the IF filter on the 8510 with 32 averages, you get the first plot.If you don’t have averaging On on the 8510, you get closer to a rectangular filter. Once you turn averaging on, you get the sinc function. On the PNA, looking at an equivalent filter, the sweep of the IF filter is shown. The first two points are pulled down by the weighting. The conclusion of this slide is that averaging on an 8510 is similar to IFBW filtering of the PNA, both are like a DSP filter. You CANNOT conclude from this slide that 32 averages on 8510 are equivalent to 150 Hz IFBW on the PNA, due to the difference in performance of the instruments. IFBW is similar to point averaging. On the 8510, you can have either point or sweep averaging.

Noise Reduction In general (equal weighting): noise reduction = 10*Log(averaging/IFBW) Relative to a reference IFBWReference: noise reduction =10*Log(averaging*IFBWReference/IFBW) For an 8510, IFBWReference=10KHz: noise reduction =10*Log(averaging*10,000/IFBW) Given a constant noise reduction: averaging = IFBWReference/IFBW or IFBW= IFBWReference/averaging

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

Example 8510 1024 averages 10 KHz IF BW What PNA IFBW produces an equivalent amount of noise reduction? IFBW = IFBWReference/averaging = 10,000/1024 = 10 Hz 10 dB of noise reduction for every tenfold of bandwidth.

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

Noise Reduction Comparison 8510 Maximum reduction 10Log(4096*10KHz/10KHz) = 36 dB Averaging: point & trace Multiples of 2: 1, 2, 4, 8, 16, … 4096 Maximum (3 dB noise reduction steps) System determines if point or trace PNA Maximum reduction 10Log(1024*10KHz/1Hz) = 70 dB  2500 times the 8510! Averaging: point (IFBW) & trace Trace, increments of 1: 1, 2, 3, … 1024 Maximum Point determined by IFBW: 40 KHz Maximum ... 10, 7, 5, 3, 2, 1.5, 1 Hz User determines point and trace separately Whether 8510 uses point or trace averageing is dependent on many factors, including the hardware and software setup. On the 8510, it is based on the application. On the PNA, you always want to use point avergaing (IFBW reduction), versus trace averaging, because it is faster.

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

PNA Performance Superior to the 8510 Difficult to easily see PNA IFBW and 8510 averaging are the same Confusion of averaging, taps, & shape factor PNA with superior noise & dynamic range 8510 dynamic range performance rolls off quicker 8510 and PNA define specs differently Look at total signal-to-noise Easiest just to measure & adjust Noise floor on 8510 is specified as peak noise; on PNA it is RMS noise floor. The difference is 10.4 dB. So you have to improve the 8510 noise floor by 10.4 dB to compare it to PNA values.

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging Why do you have both IFBW and averaging, if they do the same thing?

Two Steps to Determine Equivalent PNA IF BW 1. Measure 8510 noise level 2. Determine Equivalent PNA IFBW (Adjust PNA IFBW to match 8510 noise level)

1. Measure 8510 Noise Level a. Set 8510 up for desired measurement b. Turn calibration off c. Place marker at desired point d. Select log mag e. Set center frequency = marker f. Set span to 0 Hz g. Set 801 points h. Smoothing off i. Place reference in center of screen j. Set reference value = marker k. Select single sweep. Continue when sweep is complete l. Adjust reference value until noise envelope is centered on screen m. Adjust scale until noise spreads across 6 grid lines Three noise spikes should pass through either grid 2 or 8 Scale (roughly) equals rms trace noise: TN = scale:____;____;____;____;____ ; Average TN = ____ Repeat from step k. at least three times. Average result above. Step m, basically, quantifies the rms noise floor to make an accurate comparison with the PNA.

2. Determine Equivalent PNA IFBW a. Set PNA up for desired measurement b. Turn calibration off c. Place marker at desired point d. Select log mag e. Set center frequency = marker f. Set span to 0 Hz g. Set 801 points h. Turn trace statistics on i. Read rms noise (Std. Dev.) from marker data j. Adjust PNA IFBW until Std. Dev. = Average TN (from step 1)

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

Determine Equivalent PNA IF BW: Example 8510 S21 for 30 dB pad 201 Points; 128 averages Calibration on Determine PNA Equivalent IFBW at 10 GHz

Determine Equivalent PNA IF BW: Example Trace noise =.0045 dB On 8510, zero span and center frequency of 10GHz. The three point being measured are highlighted. (see step m on slide 16)

Determine Equivalent PNA IF BW: Example PNA S21 for same 30 dB pad 201 points, 35 KHz Calibration on Too much noise

Determine Equivalent PNA IF BW: Example Zoom in on 10 GHz Trace noise = .022 dB

Determine Equivalent PNA IF BW:Example Decrease IFBW to 1.5 KHz Trace noise = .0039 dB  Closest PNA filter producing trace noise less than .0045 dB  1.5 KHz is the answer

Determine Equivalent PNA IF BW:Example Check Good at 10 GHz Great at 50 GHz; Note 8510 signal-to-noise roll off

How to Select a PNA IFBW with Performance Comparable to an 8510 IFBW and averaging Example Noise reduction comparison PNA superiority Determining PNA IFBW Point & trace averaging

Point (IFBW) and trace averaging Point averaging (IFBW) Data at each point is collected and averaged before moving to the next point For n-averages (n-taps): AD = (MD1 + MD2 + … + MDn)/n AD = Averaged Data MD = Measured Data Trace Averaging function Equal weighting in 8510 Measured data points - n averages

Trace Averaging for n-Traces(n-averages): Each measured trace is given equal weight AT1 = MT1 AT2 = (1/2)AT1 + (1/2)MT2 AT3 = (2/3)AT2 + (1/3)MT3 = (2/3)(1/2)MT1 + (2/3)(1/2)MT2 + (1/3)MT3 = (1/3)MT1 + (1/3)MT2 + (1/3)MT3 . . . . ATn = (n-1/n)ATn-1 +(1/n)MTn = (n-1/n)(n-2/n-1)...(1/2)MT1 + . . . + (1/n)MTn = (1/n)MT1 + . . . + (1/n)MTn Trace residual after completing n-averages ATn+1 = (n-1/n)ATn+1 + (1/n)MTn+1 = (n-1/n)(n-1/n)(n-2/n-1)…(1/2 . . . + (1/n)MTn+1 = ((n-1)/n2)MT1 + . . . + (1/n)MTn+1 AT = Averaged Trace MT= Measured Trace