a.S.L.I.M. DeviceAutomated Slotted Line Impedance Measuring Device

Faculty Adviser: Dr. Peter Pachowicz

Team Members:

Andrew Huttner Charles Pritchard

Isaac Bettendorf Peter Handjinicolaou

Valentina Morrison Ian Kanyamanza

Keysight Fieldfox Network Analyzer

$19644

Creation of Voltage Standing Wave (VSW)

2

Measuring Impedance Using PSW

1) Establish a Reference Point: Mark the

minima of the shorted PSW.

Solve for the magnitude of the

reflection coefficient (|Г|):

2) Find the Magnitude of the Reflection

Coefficient (|Г|):

The phase of the reflection

coefficient can be found

using the equation:

3) Solve for the normalized load

impedance using the equation: Reflection Coefficient:

3

Requirements

5

● A signal generator that will supply a frequency range of 500 MHz to 3 GHz

● The device shall measure and display antenna impedance, both real part and

imaginary

● The device should be able to import and export data using a File

Management System

● The device should be operated through a custom GUI and a mouse pointer

Functional Decomposition

6

System Architecture

7

GUI

8

Signal Generator

9

ADF4351

Synthesizer

Block

Diagram

Filters

CST Studio

simulations

PCB design and

testing of

individual filtersFilter Bank design

and testing

Goal: Filter signal from the signal

generator to the slotted-line

10

Filters Open-Circuited Stub Design

Stepped Impedance Design

Source: J.S. Hong, Microstrip Filters for

RF/Microwave Applications, 2nd Ed. (2011) 10

1) The slotted line is a coaxial cable

with a Polyethylene dielectric.

2) The standing wave is formed

within the slotted line and the power

detector is placed within a slot along

the slotted line.

3) The envelope of the standing wave

is measured.

Slotted Line and Power Detector

Frequency Sweep and ADC

4) With multiple frequencies, the signal

generator will generate a frequency sweep.

5) The power detector will continuously

move along the line while the the signal

generator repeatedly goes through a sweep.

6) Encoder and standing wave data are sent

to the MCU (PIC24FJ32GA004)

PIC24 Microcontroller● Motor Driver circuit is

also on PIC PCB.

MCU (PIC24FJ32GA002)

Responsibilities During Scan:

1) Use 10-bit ADC to collect

amplitude of power

standing wave envelope

from power detector

1) Control the direction and

speed of power detector

motor.

1) Send position and

amplitude data (via SPI) to

BeagleBone Black.

1) Control signal generator

sweep and filter bank

13

Approach to testing

15

● Proper testing requires verifying the operability of each individual

component

● Each component individually tested so that change in operating

characteristics would be recorded

● Integration of components presents new obstacles

Test Results

17

Encoder positions

correspond to the

minimum and maximum

encoder span of 33 cm.

Vmin = 0.18V

Vmax = 1.27V

Test Results

18

- Dipole antenna as a load to the slotted-line

- Series of tests from 700 MHz to 1.3GHz

- Noise affects our results

- Slotted-line requires shielding

Funds Spent, Time Delegated, and Responsibilities

Team Members Hours (Including

ECE 492)

Responsibilities

I. Bettendorf 360 Project Manager and MCU Design

P. Handjinicolaou 340 Software Development: GUI and

Communications

A. Huttner 210 Software Development: DUT Characteristics

I. Kanyamanza 350 MCU Design

V. Morrison 401 Filter Design

C. Pritchard 390 Signal Generator Design / Hardware Technician

Total 2,051 Total Hardware Cost: $617

Total

Hardware

Cost: $617

17

Lessons Learned

20

1) Strong criteria for testing individual components

2) Not all features in datasheet are true. Verify everything in

datasheet.

3) Compartmentalization was a negative for us

4) More structured code and files. Was difficult reading and

editing other teammates’ code.

5) Double your time estimate for integration. You WILL run into

problems!

Acknowledgements

Filters

Standing Wave (SW) of Different Loads

When Load is a short (Load is zero Ohms) When Load is open (Load is infinite Ohms)

Sampling Slotted Line and Speed of Power Detector

ADF4351 Synthesizer

• Programmable frequencies of 35Mhz to

4400Mhz

• Supply voltage 3-3.6v

• 3 wire serial data transfer via 32 bit shift

register pins 1-3

• Six 32 bit data registers control device

functionality, write to register 0 sets device

25

ADF4351 Synthesizer

26

VCO frequency vs feedback voltage

Phase Lock Loop

ADF4351 Synthesizer

Phase detector and charge pump27

Signal Generator Design Schematic

28

Signal Generator PCB Design 1 and 2

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Signal Generator testing design 1

30

Design failed due to ground loop created by encirclement of

10Mhz oscillator seen in the spectrum on the right. Lesson

learned: use jumper wires to prevent loops

Signal Generator testing design 2

31

Use of jumper wires underneath the board eliminated problem of ground loops removing the

unwanted frequencies in the output. The output is off by 10Mhz and down 3dB with first harmonic

down almost 30dB.

32

Frequency Sweep Flow Diagram

33

LT5534 Power Detector

• 50Mhz to 3Ghz RF power detector

• Capable of measuring RF signals over a

60 dB range

• RF signals on a decibel scale are

precisely converted into a DC voltage

on a linear scale

• The output responds in less than 40ns

to input signal

LT5534 Power Detector Schematic