HAM RADIO 2012

Evolution of the DG8SAQ

Vector Network Analyzer:

New VNWA3 Features & Applications

PROF. DR. THOMAS BAIER E-mail: baier@hs-ulm.de

DG8SAQ Hochschule Ulm

Prittwitzstrasse 10

89075 Ulm

English version by

Jan Verduyn G0BBL and Kurt Poulsen OZ7OU

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mailto:baier@hs-ulm.demailto:baier@hs-ulm.demailto:baier@hs-ulm.de

VNWA Presentation - Contents

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• What are S-parameters?

• How does the VNWA function

and how was it born?

• New features

• Some novel measurement examples

Dank an:

- Eric Hecker - Fred Schneider

- Giuseppe Gristina - Mario Armando Natali

It is all about scattering of Waves

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Incident

Reflected

Transmitted

Lens

DUT

DUT : DEVICE UNDER TEST

Optic

Electrical

a1

b1

b2

S-Parameter = Scattering Parameter Sik

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• Complex S-parameters: Sik = bi / ak

• Sik are complex numbers consisting of

Magnitude and Phase!

b1

a1

b2

a2

ZL

Tor 1 Tor 2

S21 S12

S11 S22

Zweitor

ZL

Two Port

Port 1 Port 2

S-Parameter S11

| S11 | = Input Return Loss

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DUT

a1 b2

b1

111

1

bS

a 11

11

1

1

SVSWR

S

S-Parameter S21

| S21 | = Transmission Loss

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DUT

a1 b2

b1

221

1

bS

a

The VNWA can measure these S-Parameters!

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DUT

DUT : DEVICE UNDER TEST

PTEE 2011 7

11S 21S

Evolution and Principle of Operation (1)

VNWA Basics

• Tunable

Signal Source

• 3 Coherent

Receivers

• Device Control

• Data Processing

and Graphics

RECEIVER / DETECTOR

PROCESSOR / DISPLAY

REFLECTED

(A)

TRANSMITTED

(B)

INCIDENT

(R)

SIGNAL

SEPARATION

Source

Incident

Reflected

Transmitted

DUT

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Evolution and Principle of Operation (2)

Functional Diagram

• Tuneable

Signal Source

• 3 Coherent

Receivers

• Device Control

• Dataprocessing

and Graphics

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Direct Digital Synthesizer (DDS)

3 Gilbert-Cell Mixers + DDS

+ PC Sound Card (IF)

Evolution and Principle of Operation (3)

Functional Block Diagram

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Evolution and Principle of Operation (4)

Problem: DDS Alias Frequencies

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RF DDS

LO DDS

All Alias-Frequencies mix down

to the same Intermediate Frequency

→ either use Low Pass filter, or…

Nyq

uis

tgre

nze

Evolution and Principle of Operation (5)

… use LO DDS with Clock Frequency Offset

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all Alias-Frequencies can now be used to

extend the VNWA Frequency Range

RF DDS

LO DDS

FC2

Evolution and Principle of Operation (6)

Result: VNWA1

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Evolution and Principle of Operation (7)

VNWA1 First Practical Use

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Evolution and Principle of Operation (8)

Updated Development Targets

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Main Target: A Tool for Education

• Frequency Range > 500 MHz

• Continous Frequency Range – no Gaps

• Constructed on PCB / reproducible Design

• Lowest possible Cost

Evolution and Principle of Operation (9)

Continous Frequency Range

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Gaps in the frequency range

at multiples of the clock frequency

Solution: variable clock frequencies by changing

PLL-clock multipliers (integrated in DDS)

Evolution and Principle of Operation (10)

Result: VNWA2

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• Frequency Range:

1 kHz…>1,3 GHz

• Dynamic Range:

>90 dB (f ≤ 500 MHz)

>60dB (f > 500 MHz)

S11, S21 Measurements

• Control via Parallel Port

• Signal processing via

external (PC) Sound Card

Layout: Dan Andersson M0DFI

Evolution and Principle of Operation (10)

Milestone 2009: VNWA from SDR-Kits

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SDRKits

=

Jan Verduyn G0BBL

• Ex Merchant Navy Radio Officer

• Ex Motorola Engineer

• Retired and started SDR-Kits

• Radio Amateur

Halle A1 Stand E812

Evolution and Principle of Operation (11)

Market impact on VNWA2 Developements

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Fewer Computers with

Parallel Port Interface

Fewer Computers with

Stereo-Line-In

Evolution and Principle of Operation (12)

VNWA2-USB

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• USB Interface

• Controller

• USB Audio Codec

• Powered from USB Only a USB cable

connection to the PC

Evolution and Principle of Operation (13)

VNWA3: Ready Assembled in Factory

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• TCXO

• Additional

Clock-PLL!!

Evolution and Principle of Operation (14)

Less Interference with flexible Clock-PLL

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VNWA2

VNWA3

Open, 8000 Points, 0,34ms/Point

VNWA3 further

optimized via Software

Evolution and Principle of Operation (15)

VNWA3 Options

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• New expansion PCB with

2nd Audio-Codec to

measure S11 and S21 simultaneously

• External Clock Input

• Possible to extend VNWA3

to a fully automatic 2 port

Analyzer with an external

Transfer Relay

VNWA3E

Applications:

Impedance Measurements (1)

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Impedance Measurements (2)

Variant 1: Return Loss Measurement

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11

11

150

1x

SZ

S

Highest

accuracy for

Zx close to 50 Ω

Cal: SOL

Impedance Measurements (3)

Variant 2: I-Messung

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RX measures current through Zx

Highest for

large values of Zx

Cal: Thru

Impedance Measurements (4)

Variant 3: V-Measurement

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RX measures

Voltage across Zx

Highest for

low values of Zx

Cal: SOL

Impedance Measurements (5)

Variante 4: RF-IV Measurement

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Zx

Combination of

V & I-Measurement

x

VZ

I

Excellent for

ALL values of Zx

RF-IV Test Head: http://www.makarov.ca/

Cal: SOL

Impedance Measurements (6)

Measurement Deviation-Variants 1 - 4

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Impact of 10% increase of Zx value

on measurement result:

RF-IV shows best overall sensitivity!

Zx S11 I V V / I

0,1 Ω -0,04% 0,01% -9,96% 9,97% 51 Ω 480,68% 3,27% -3,08% 6,56%

100 kΩ 0,01% 9,08% 0,00% 9,99%

Impedance of a 100 pF SMD Capacitor:

Effect of 2 nH in Load Standard

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Rs

Cs

Abt. 50% Rs-Error

Practically no Cs-Error

Load-Model critical for Q measurements!

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New: Low Loss Capacitor (LLC)

as an additional Calibration Standard…

Error! Still Correct!

… Fixes Load Model-

Error!!!

If you have a clock you always know what

time it is …

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With TWO Clock you are never quite

shure which time is right !

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• My two

Rubidium

Frequency

standards:

• How accurately

do they run in

sync?

1 2

Application: Frequency Comparison (1)

VNWA3 as Phase Comparator

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• Precise Phase

Measurement

with VNWA3

• Frequency

deviation

calculated from

Phase

VNWA3E

Frequency Comparison (2)

Measurement Accuracy

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• TCXO

compared

to itself

• 1s

Measurement

• abt ±10 µHz

variation!!!

3 Sweeps with 10 Points and 0,1s / Point

Frequency Comparison (3)

Rubidium 1 vs. Rubidium 2 over 260s

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Deviation = -0,0025 Hz ± 0,0003 Hz at 10 MHz

≡ 2,5∙10-10

Frequency Comparison (4)

Allan Deviation from VNWA-Measurement

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-1 510

0 510

1 510

2 510

3 510

4

Time [sec]

10-11

2

5

10-10

2

5

10-9

2

5

10-8

2

5

10-7

All

and

evia

tio

n/F

req

uen

cy[r

ad]

Rubidium Standard 1

measured against

Rubidium Standard 2

aus http://tf.nist.gov/general/glossary.htm

1 2

Frequency Comparison (5)

Rubidium Standard vs. VNWA3 TCXO

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Deviation = -3 Hz ± 1 Hz at 10 MHz ≡ -0,3 ppm

Application:

Time Domain Analysis (1)

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Cable

75

Ω

open Cable 25 Ω

Ca

ble

50

Ω

Frequency Domain

Time Step Response

Time Domain Analysis (2)

Locate the faulty Christmas Tree Light Bulb !!

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http://www.pa4tim.nl/?p=345

Application Example: Cavity Resonance (1)

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Lowest Resonance mode:

Cavity Resonance (2)

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8

001

3 10 m/s2,405

2 6,28 9,5cm

1209MHz

cf J

r

Cavity Resonance (3)

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Lowest Resonance mode:

Cavity Resonance (4)

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Empty

vs.

Filled

Cavity Resonance (5)

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Cavity Resonance (6)

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Rocket Tank – real VNWA3 measurements !!

Summary

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• The VNWA3 is a versatile Test

Instrument

• Suitable for many - even -

professional Applications!

• VNWAs are used on 5 Continents

The VNWA3 is in use all over the World.

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The VNWA3 is in use all over the World.

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The VNWA3 is in use all over the World..

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The VNWA3 is in use all over the World.

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The VNWA3 is in use all over the World.

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Finally, … a Warning:

VNWA´s are Addictive!

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