PICO PicoVNA 106 User manual

User's Guide
pv106ug r1
Vector Network Analyzer
PicoVNA™ 106
DistributionintheUK&Ireland
LambdaPhotometricsLimited
LambdaHouseBatfordMill
HarpendenHertsAL55BZ
UnitedKingdom
E:[email protected]
W:www.lambdaphoto.co.uk
T:[phone]
F:[phone]
Distribution in the UK & Ireland
Lambda Photometrics Limited
Lambda House Batford Mill
Harpenden Herts AL5 5BZ
United Kingdom
E: [email protected]
W: www.lambdaphoto.co.uk
T: [phone]
F: [phone]

Contents
I
© 2017 Pico Technologypv106ug r1
Contents
1 Safety ................................................................................................................................... 1
1 Symbols .................................................................................................................................................. 1
2 Maximum input/output ranges .............................................................................................................. 1
3 Grounding ............................................................................................................................................... 2
4 External connections .............................................................................................................................. 3
5 Environment ............................................................................................................................................ 3
6 Care of the product ................................................................................................................................ 4
2 Quick start guide ................................................................................................................. 5
1 Installing the software ........................................................................................................................... 5
2 Loading the calibration kit(s) ................................................................................................................. 5
3 Setting up calibration parameters ......................................................................................................... 6
4 Setting up display parameters ............................................................................................................... 6
5 Calibration tips ....................................................................................................................................... 7
6 Running in demo mode .......................................................................................................................... 7
3 Description .......................................................................................................................... 8
4 Vector network analyzer basics ...................................................................................... 10
1 Introduction .......................................................................................................................................... 10
2 Structure of the VNA ............................................................................................................................ 10
3 Measurement ....................................................................................................................................... 11
4 S-parameters ........................................................................................................................................ 11
5 Displaying measurements ................................................................................................................... 14
6 Calibration and error correction .......................................................................................................... 14
7 Other measurements ........................................................................................................................... 15
1 Reflection parameters ............................................................................................................. 15
2 Transmission parameters ....................................................................................................... 15
3 Phase ........................................................................................................................................ 16
4 Group delay .............................................................................................................................. 16
5 Gain compression .................................................................................................................... 17
6 AM to PM conversion .............................................................................................................. 17
7 Time domain reflectometry (TDR) .......................................................................................... 17
5 Getting started .................................................................................................................. 22
1 Minimum requirements ....................................................................................................................... 22
2 Software installation ............................................................................................................................ 22
1 Typical error messages ........................................................................................................... 22
3 Switching on the VNA .......................................................................................................................... 23
4 Calibration kit parameters ................................................................................................................... 23
1 Insertable DUT ......................................................................................................................... 24
2 Non-insertable DUT .................................................................................................................. 24
3 Open circuit model ................................................................................................................... 24
4 Short circuit model ................................................................................................................... 24

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5 Short and open without models .............................................................................................. 24
6 Calibration kit editor ................................................................................................................ 24
7 Using a matched termination with poor return loss or unmodeled short and open ............ 25
6 Operation ........................................................................................................................... 27
1 The PicoVNA 2 main window .............................................................................................................. 27
1 Display setup ............................................................................................................................ 27
2 Data markers ............................................................................................................................ 29
3 Measurement enhancement ................................................................................................... 31
4 Memory facility ........................................................................................................................ 34
5 Limit lines facility ..................................................................................................................... 35
6 Status panel ............................................................................................................................. 36
7 Triggered sweep ...................................................................................................................... 37
8 Sweep trigger output ............................................................................................................... 37
9 Measurement start / stop ....................................................................................................... 37
10 PC data link interruption ........................................................................................................ 37
2 Calibration ............................................................................................................................................ 38
1 Changing the frequency sweep settings without recalibrating ............................................. 40
2 Calibration steps for S11 measurements ............................................................................... 41
3 Calibration steps for S21 measurements ............................................................................... 41
4 Calibration steps for S11 and S21 measurements ................................................................ 41
5 Calibration steps for all S-parameters measurements (insertable DUT) ............................. 42
6 Calibration steps for all S-parameters measurements (non-insertable DUT) ...................... 42
7 Calibration for best dynamic range – minimizing the effect of crosstalk ............................ 43
3 Measurements ..................................................................................................................................... 44
1 Return loss ............................................................................................................................... 44
2 Insertion loss / gain ................................................................................................................. 45
3 Complete 2-port measurement ............................................................................................... 45
4 Group delay .............................................................................................................................. 46
5 Time domain measurements .................................................................................................. 46
6 Reverse measurements on two port devices ......................................................................... 50
7 Powering active devices using the built-in bias-Ts ................................................................ 51
4 Reference plane extension and de-embedding .................................................................................. 51
5 Saving data ........................................................................................................................................... 54
6 Loading data ......................................................................................................................................... 54
7 Plotting graphics .................................................................................................................................. 55
8 Saving graphics .................................................................................................................................... 55
9 Signal generator utility ......................................................................................................................... 56
10 Output power at the 1 dB gain compression point utility ................................................................ 56
11 AM to PM conversion utility .............................................................................................................. 58
12 Compare data utility ........................................................................................................................... 59
13 Closing down the software ................................................................................................................ 61
7 Performance verification and maintenance ................................................................... 62
1 Measurement uncertainty .................................................................................................................... 62

Contents
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© 2017 Pico Technologypv106ug r1
2 Routine maintenance ........................................................................................................................... 63
8 Performance specification .............................................................................................. 64
9 Troubleshooting guide ..................................................................................................... 68
10 Warranty .......................................................................................................................... 70
Index ..................................................................................................................................... 71

PicoVNA 106 6 GHz Vector Network Analyzer 1
© 2017 Pico Technology pv106ug r1
1Safety
To prevent possible electrical shock, fire, personal injury, or damage to the product, carefully read this safety
information before attempting to install or use the product. In addition, follow all generally accepted safety
practices and procedures for working with and near electricity.
This instrument has been designed to meet the requirements of EN61010-1 (Safety Requirements for
Electrical Equipment for Measurement, Control and Laboratory Use) and is intended only for indoor use in a
Pollution Degree 1 environment (no pollution, or only dry non-conductive pollution) in the temperature range
15 °C to 35 °C, 20 % to 80 % relative humidity (non-condensing).
The following safety descriptions are found throughout this guide:
A WARNING identifies conditions or practices that could result in injury or death.
A CAUTION identifies conditions or practices that could result in damage to the product or equipment to
which it is connected.
WARNING
To prevent injury or death use the product only as instructed and use only the power supply
provided. Protection provided by the product may be impaired if used in a manner not specified
by the manufacturer.
1.1 Symbols
These safety and electrical symbols may appear on the product or in this guide.
Symbol Description
Earth (ground) terminal
This terminal can be used to make a measurement ground
connection. It is not a safety or protective earth.
Chassis terminal
Possibility of electric shock
CAUTION
Appearance on the product indicates a need to read these
safety instructions.
Do not dispose of this product as unsorted municipal waste.
1.2 Maximum input/output ranges
WARNING
To prevent electric shock, do not attempt to measure or apply signal levels outside the
specified maxima below.

Safety2
© 2017 Pico Technologypv106ug r1
The table below indicates the maximum voltage of the outputs and the overvoltage protection range for
each input on the VNA. The overvoltage protection ranges are the maximum voltages that can be applied
without damaging the instrument.
Connector Maximum operating voltage
(output or input)
Overvoltage or overcurrent
protection
Ports 1 and 2 +10 dBm (about 710 mV RMS) +20 dBm (about 2.2 V RMS)
Bias tees 1 and 2 ±15 V DC 250 mA
Trigger and reference in ±6 V pk
Trigger and reference out 0 V to +5 V Do not apply a voltage
WARNING
Signals exceeding the voltage limits in the table below are defined as "hazardous live" by EN
61010.
Signal voltage limits of EN61010
± 70 V DC 33 V AC RMS ± 46.7 V pk max.
WARNING
To avoid equipment damage and possible injury, do not operate the instrument outside its rated
supply voltages or environmental range.
CAUTION
Exceeding the overvoltage protection range on any connector can cause permanent damage to
the instrument and other connected equipment.
CAUTION
To prevent permanent damage, do not apply an input voltage to the trigger or reference output
of the VNA.
1.3 Grounding
WARNING
The instrument's ground connection through the USB cable is for functional purposes only. The
instrument does not have a protective safety ground.
WARNING
To prevent injury or death, never connect the ground of an input or output (chassis) to any
electrical power source. To prevent personal injury or death, use a voltmeter to check that there
is no significant AC or DC voltage between the instrument's ground and the point to which you
intend to connect it.
CAUTION
Applying a voltage to the ground input is likely to cause permanent damage to the instrument,
the attached computer, and other equipment.
CAUTION
To prevent measurement degradation caused by poor grounding, always use the high-quality
USB cable supplied with the instrument.

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1.4 External connections
WARNING
To prevent injury or death, only use the adaptor supplied with the product. This is approved for
the voltage and plug configuration in your country.
Power supply options and ratings
Model name USB connection
Ext DC power supply
Voltage Current Total power
PicoVNA 106
USB 2.0.
Compatible with
USB3.0.
12 to 15 V DC 1.85 A pk 22 W
WARNING
Containment of radio frequencies
The instrument contains a swept or CW radio frequency signal source (300 kHz to 6.02 GHz at
+6 dBm max.) The instrument and supplied accessories are designed to contain and not radiate
(or be susceptible to) radio frequencies that could interfere with the operation of other
equipment or radio control and communications. To prevent injury or death, connect only to
appropriately specified connectors, cables, accessories and test devices, and do not connect to
an antenna except within approved test facilities or under otherwise controlled conditions.
1.5 Environment
WARNING
To prevent injury or death, do not use the VNA in wet or damp conditions, or near explosive gas
or vapor.
CAUTION
To prevent damage, always use and store your VNA in appropriate environments.
Storage Operating
Temperature –20 °C to +50 °C +15 °C to +35 °C
Humidity Up to 80% RH (non-condensing) Up to 80% RH (non-condensing)
Altitude 2000 m
Pollution degree 2
CAUTION
Do not block the air vents at the back or underside of the instrument as overheating will
damage.
Do not insert any objects through the air vents as internal interference will cause damage.

Safety4
© 2017 Pico Technologypv106ug r1
1.6 Care of the product
The product and accessories contain no user-serviceable parts. Repair, servicing and calibration require
specialized test equipment and must only be performed by Pico Technology or an approved service provider.
There may be a charge for these services unless covered by the Pico warranty.
WARNING
To prevent injury or death, do not use the product if it appears to be damaged in any way, and
stop use immediately if you are concerned by any abnormal behavior.
CAUTION
To prevent damage to the device or connected equipment, do not tamper with or disassemble
the instrument, case parts, connectors, or accessories.
When cleaning the product, use a soft cloth dampened with a solution of mild soap or detergent
in water. Do not allow liquids to enter the instrument's casing.
WARNING
To avoid equipment damage, do not block the ventilation ports on the instrument.
CAUTION
Take care to avoid mechanical stress or tight bend radii for all connected leads, including all
coaxial leads and connectors. Mishandling will cause deformation of sidewalls, and will
degrade performance. In particular, note that test port leads should not be formed to tighter
than 5 cm (2") bend radius.
To prevent measurement errors and extend the useful life of test leads and accessory
connectors, ensure that liquid and particulate contaminants cannot enter. Always fit the dust
caps provided and use the correct torque when tightening. Pico recommends: 1 Nm (8.85 inch
lb) for supplied and all stainless steel connectors, or 0.452 Nm (4.0 inch-lb) when a brass or
gold-plated connector is interfaced.

PicoVNA 106 6 GHz Vector Network Analyzer 5
© 2017 Pico Technology pv106ug r1
2Quick start guide
2.1 Installing the software
Obtain the PicoVNA 2 software installer from the disk supplied or from www.picotech.com/downloads.
Run the installer (right-click and Run as administrator) and ensure that the installation was successful.
Connect the PicoVNA 106 unit to the computer and wait while Windows automatically installs the driver.
In case of difficulties, refer to Software installation for more details.
2.2 Loading the calibration kit(s)
If the device to be tested is ‘insertable’ (one female and one male connector), two kits are required.
Otherwise a single kit is required. See diagrams below:
Run the PicoVNA 2 software
In the main menu, select Tools > Calibration kit
Click Load P1 kit, select the data for your Port 1 kit and then click Apply
Click Load P2 kit, select the data for your Port 2 kit and then click Apply
Select the calibration kit(s) required depending on the device to be tested.
Note: if testing a non-insertable DUT with, for example, female connectors, use a single female kit for ports 1
and 2.

Quick start guide6
© 2017 Pico Technologypv106ug r1
2.3 Setting up calibration parameters
Click Calibration to open the Calibration window:
2.4 Setting up display parameters
Click Display in the main window to open the Display Set Up window:
When finished, click Start in the main window to begin measurements

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2.5 Calibration tips
The bandwidth setting used during calibration largely determines the available dynamic range during the
measurement. The table below shows suggested bandwidth and power settings to use during calibration for
different types of measurement.
Measurement Calibration
bandwidth
Calibration
averaging
Calibration
power
Comments
Fastest speed 10 kHz None +0 dBm Set bandwidth to 140 kHz during measurement
Best accuracy and
~100dB dynamic range
100 Hz None –3 dBm Set bandwidth to 100 Hz during measurement
General use, fast speed,
~90dB dynamic range
1 kHz None +0 dBm Set bandwidth to 1 kHz during measurement
Best dynamic range 10 Hz None +6 dBm Leave bandwidth unchanged during measurement.
Refer to “Calibration for best dynamic range –
minimizing the effect of crosstalk”.
2.6 Running in demo mode
Demo mode allows you to explore the user interface software without the need to have an instrument
running.
To enter demo mode, run the PicoVNA 2 software with no instrument connected.
Click Go to demo in the dialog that appears.
PicoVNA 2 will then offer you a selection of demonstration measurements.

Description8
© 2017 Pico Technologypv106ug r1
3Description
The PicoVNA 106 is a PC-driven vector network analyzer capable of operation over the range of 300 kHz to 6
GHz. It can perform direct measurements of forward and reverse parameters with up to 118 dB of dynamic
range. The test frequency can be set with a resolution of 10 Hz or less. A simplified block diagram of the
instrument is shown below:
Sim
p
lified block dia
g
ram of the PicoVNA 106
The architecture is based on a four-receiver ("Quad RX") arrangement using a bandwidth of up to 140 kHz.
Couplers 1 and 2 are wideband RF bridge components which provide the necessary directivity in both
directions. Signal detection is by means of analog-to-digital converters used to sample the IF signal. The
sample data is processed by the embedded controller to yield the I and Q components. The detection
system operates with an IF of 1.3 MHz and employs a patented circuit technique to yield fast speeds with
very low trace noise.
The instrument's software runs on a personal computer and communication with the instrument is through
the USB interface. The software carries out the mathematical processing and allows the display of
measured parameters in many forms, including:
frequency domain
time domain
de-embedding utility
measuring output power at the 1 dB gain compression point
measuring AM to PM conversion

PicoVNA 106 6 GHz Vector Network Analyzer 9
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Front
p
anel of the PicoVNA 106
Back
p
anel of the PicoVNA 106

Vector network analyzer basics10
© 2017 Pico Technologypv106ug r1
4Vector network analyzer basics
4.1 Introduction
A vector network analyzer is used to measure the performance of circuits or networks such as amplifiers,
filters, attenuators, cables and antennas. It does this by applying a test signal to the network to be tested,
measuring the reflected and transmitted signals and comparing them to the test signal. The vector network
analyzer measures both the magnitude and phase of these signals.
4.2 Structure of the VNA
The VNA consists of a tunable RF source, the output of which is split into two paths. The signal feeds to the
couplers are each measured by their respective reference receivers through power dividers. In the forward
mode, the test signal is passed through a directional coupler or directional bridge before being applied to the
DUT. The directional output of the coupler, which selects only signals reflected from the input of the DUT, is
connected to the Port1 receiver where the signal’s magnitude and phase are measured. The rest of the
signal, the portion that is not reflected from the input, passes through the DUT to the Port2 receiver where its
magnitude and phase are measured. The measurements at the Port1 and Port2 receivers are referenced to
the measurements made by the Ref1 and Ref2 receivers so that any variations due to the source are
removed. The Ref1 and Ref2 receivers also provide a reference for the measurement of phase.
Sim
p
lified vector network anal
y
zer block dia
g
ram
In reverse mode, the test signal is applied to the output of the DUT, and the Port2 receiver is used to
measure the reflection from the output port of the DUT while the Port1 receiver measures the reverse
transmission through the DUT.

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4.3 Measurement
Vector network analyzers have the capability to measure phase as well as magnitude. This is important for
fully characterizing a device or network either for verifying performance or for generating models for design
and simulation. Knowledge of the phase of the reflection coefficient is particularly important for matching
systems for maximum power transfer. For complex impedances the maximum power is transferred when
the load impedance is the complex conjugate of the source impedance (see figure).
Matchin
g
a load for maximum
p
ower transfer
Measurement of phase in resonators and other components is important in designing oscillators. In
feedback oscillators, oscillation occurs when the phase shift round the loop is a multiple of 360° and the
gain is unity. It is important that these loop conditions are met as close as possible to the center frequency
of the resonant element to ensure stable oscillation and good phase noise performance.
The ability to measure phase is also important for determining phase distortion in a network. Phase
distortion can be important in both analog and digital systems. In digital transmission systems, where the
constellation depends on both amplitude and phase, any distortion of phase can have serious effects on the
errors detected.
4.4 S-parameters
The basic measurements made by the vector network analyzer are S (scattering) parameters. Other
parameters such as H, Y and Z parameters may all be deduced from the S-parameters if required. The
reason for measuring S-parameters is that they are made under conditions that are easy to produce at RF.
Other parameters require the measurement of currents and voltages, which is difficult at high frequencies.
They may also require open circuits or short circuits that can be difficult to achieve at high frequencies, and
may also be damaging to the device under test or may cause oscillation.
Forward S-parameters are determined by measuring the magnitude and phase of the incident, reflected and
transmitted signals with the output terminated with a load that is equal to the characteristic impedance of
the test system (see figure below).

Vector network analyzer basics12
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S-
p
arameters definition
The measured parameters are presented in a file similar to the one below. The format is as follows:
Header lines: these start with a !symbol and give general information such as time and date.
Format line: this starts with a #symbol and gives information about the format of the data.
oFirst field gives the frequency units, in this case MHz
oSecond field indicates the parameters measured, in this case S-parameters
oThird field indicates the format of the measurement, in this case MA meaning magnitude and angle.
Others formats are RI, meaning real and imaginary, and DB, meaning log magnitude and angle.
Data lines. The number of columns of data depends on the parameters that have been measured.
oA 1-port measurement measures the reflected signal from the device under test and usually produces
three columns. If the format is MA (magnitude and angle), the first column is the measurement
frequency, the second is the magnitude of S11 and the third is the angle of S11. If the format is RI, the
second column is the real part of S11 and the third column is the imaginary part of S11.
oWhen a reflection and transmission measurement is made there are five columns of data. Column 1
is the measurement frequency, columns 2 and 3 contain S11 magnitude and angle or real and
imaginary data, and columns 4 and 5 contain S21 magnitude and angle or real and imaginary data.
oIf a full 2-port measurement is made, there will be nine columns of data. Column 1 contains frequency
information, columns 2 and 3 S11 data, 4 and 5 S21 data, 6 and 7 S12 data, and 8 and 9 S22 data.

PicoVNA 106 6 GHz Vector Network Analyzer 13
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The PicoVNA 106 can generate full set of 2-port parameters but you can choose to export either 1-port .s1p
or full 2-port .s2p S-parameter files to suit most RF and microwave circuit simulators.
Part of a typical 2-port S-parameter file is shown below. The header shows that the frequency units are MHz,
the data format is Magnitude and Angle and the system impedance is 50 Ω. Column 1 shows frequency, 2
and 3 S11, 4 and 5 S21, 6 and 7 S12, and 8 and 9 S22.
! 06/09/2005 15:47:34
! Ref Plane: 0.000 mm
# MHZ S MA R 50
!
3 0.00776 16.96 0.99337 -3.56 0.99324 -3.53 0.00768 12.97
17.985 0.01447 19.99 0.9892 -20.80 0.98985 -20.72 0.01519 15.23
32.97 0.01595 20.45 0.98614 -37.96 0.98657 -37.95 0.01704 6.40
47.955 0.01955 28.95 0.98309 -55.15 0.98337 -55.10 0.018 1.75
62.94 0.02775 24.98 0.98058 -72.29 0.98096 -72.29 0.0199 -6.07
77.925 0.03666 11.76 0.97874 -89.46 0.9803 -89.45 0.02169 -23.06
92.91 0.04159 -6.32 0.97748 -106.62 0.9786 -106.62 0.01981 -48.43
107.895 0.0426 -24.79 0.97492 -123.77 0.97579 -123.89 0.01424 -87.79
122.88 0.0396 -41.35 0.97265 -141.25 0.97269 -141.30 0.00997 -166.81
137.865 0.03451 -52.96 0.96988 -158.65 0.96994 -158.76 0.01877 113.15
152.85 0.03134 -56.07 0.96825 -176.27 0.96858 -176.28 0.03353 69.81
167.835 0.03451 -57.72 0.96686 166.10 0.96612 165.99 0.04901 34.83
182.82 0.04435 -67.59 0.9639 148.18 0.96361 148.21 0.06131 1.42
197.805 0.05636 -86.28 0.96186 130.15 0.96153 130.06 0.07102 -33.33
212.79 0.06878 -110.45 0.95978 111.82 0.95996 111.90 0.07736 -69.57
227.775 0.08035 -136.14 0.9557 93.50 0.9568 93.41 0.08303 -107.21
242.76 0.09099 -161.24 0.95229 74.84 0.95274 74.89 0.08943 -144.34
257.745 0.10183 175.34 0.94707 56.03 0.94755 55.95 0.09906 -179.63

Vector network analyzer basics14
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4.5 Displaying measurements
Input and output parameters, S11 and S22, are often displayed on a polar plot or a Smith chart. The polar plot
shows the result in terms of the complex reflection coefficient, but impedance cannot be directly read off
the chart. The Smith chart maps the complex impedance plane onto a polar plot. All values of reactance and
all positive values of resistance, from 0 to ∞, fall within the outer circle. This has the advantage that
impedance values can be read directly from the chart.
The Smith chart
4.6 Calibration and error correction
Before accurate measurements can be made, the network analyzer needs to be calibrated. In the calibration
process, well-defined standards are measured and the results of these measurements are used to correct
for imperfections in the hardware. The most common calibration method, SOLT (short, open, load, through),
uses four known standards: a short circuit, an open circuit, a load matched to the system impedance, and a
through line. These standards are usually contained in a calibration kit and their characteristics are stored
on the controlling PC in a Cal Kit definition file. Analyzers such as the PicoVNA 106 that have a full S-
parameter test set can measure and correct all 12 systematic error terms.

PicoVNA 106 6 GHz Vector Network Analyzer 15
© 2017 Pico Technology pv106ug r1
Six key sources of errors in forward measurement.
Another six sources exist in the reverse measurement
(
not shown
)
.
4.7 Other measurements
S-parameters are the fundamental measurement performed by the network analyzer, but many other
parameters may be derived from these including H, Y and Z parameters.
4.7.1 Reflection parameters
The input reflection coefficient Γ can be obtained directly from S11:
ρis the magnitude of the reflection coefficient i.e. the magnitude of S11:
ρ= |S11|
Sometimes ρ is expressed in logarithmic terms as return loss:
return loss = –20 log(ρ)
VSWR can also be derived:
VSWR definition
4.7.2 Transmission parameters
Transmission coefficient Tis defined as the transmitted voltage divided by the incident voltage. This is the
same as S21.

Vector network analyzer basics16
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If T is less than 1, there is loss in the DUT, which is usually referred to as insertion loss and expressed in
decibels. A negative sign is included in the equation so that the insertion loss is quoted as a positive value:
If T is greater than 1, the DUT has gain, which is also normally expressed in decibels:
4.7.3 Phase
The phase behavior of networks can be very important, especially in digital transmission systems. The raw
phase measurement is not always easy to interpret as it has a linear phase increment superimposed on it
due to the electrical length of the DUT. Using the reference plane function the electrical length of the DUT
can be removed leaving the residual phase characteristics of the device.
Operation on phase data to yield underlying characteristics
4.7.4 Group delay
Another useful measurement of phase is group delay. Group delay is a measure of the time it takes a signal
to pass through a network versus frequency. It is calculated by differentiating the phase response of the
device with respect to frequency, i.e. the rate of change of phase with frequency:
The linear portion of phase is converted to a constant value typically, though not always, representing the
average time for a signal to transit the device. Differences from the constant value represent deviations from
linear phase. Variations in group delay will cause phase distortion as a signal passes through the circuit.
When measuring group delay the aperture must be specified. Aperture is the frequency step size used in the
differentiation. A small aperture will give more resolution but the displayed trace will be noisy. A larger
aperture effectively averages the noise but reduces the resolution.