An Oscillator Design For Superheterodyne Receiver Application Computer Science Essay

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This thesis presents an oscillator design for Superheterodyne receicver application at frequency 2.4GHz. Advanced Design System (ADS) software is used to design and simulate the oscillator circuit design. Once the power up, oscillators will produce an output periodic electrical signal without an external input signal required, that is why to call it as circuits within one terminal.

For proving the a deep understanding on oscillator and frequency synthesizers, the topology have been selected for the components for each in the circuit designed, circuit fabricated, circuit tested and even the calculation according to the equation of oscillator design are included.

First of all, before to begin the oscillator design, there is important to understand what is oscillator? It will be explained at the coming thesis. [6]

Oscillator is classified into two types:

Harmonic Oscillators which producing the stable sinusoidal waveform with low phase nose at the output.

Relaxation oscillators (also called astable multivibrator), is two unstable states of circuits. Where the circuit will switches back-and-forth between these states. Therefore, output is generally square waves.

Colpitts oscillator is a kind of the Harmonic Oscillators and has been selected as project design. An accurate modelling of package parasitic is important during selection for obtained the accurate result after simulation. As the reason the NPN 9GHz wideband transistor for BFG 520 into a SOT 143 package chose and carries out the simulation.

During the final stage, after all of the predefined design specifications are achieved then fabricated the schematic layout is generated on a PCB, thus the circuit design can be tested by using the spectrum analyzer.

Fortunately, at this oscillator design has achieved the predefined design specification. According to the simulated results, conclusion can be made for this oscillator design has met its technical objectives within the particular result, thus it is ideal for Superheterodyne receiver application design.

Table of Contents

Acknowledgement i

DECLARATION OF INDEPENDENT WORK ii

Abstract iii

List of Figures vi

List of Tables viii

Chapter 1 Introduction 1

1.1 Background 1

1.2 Basic Oscillator Theory 1

1.3 Project Aim and Scopes 2

1.4 Application Examples 2

1.5 Technical Objective 2

1.6 Radio Frequency Overview 3

Chapter 2 Literature Review 4

Chapter 3 Methodology 7

3.1 Software Design 7

3.1.1 Advance Design System Overview 7

3.1.2 DesignGuide for Expert Help 8

3.2 Impedance Matching for Transistor at 2.4GHz 8

3.3 Oscillation Frequency 16

3.4 Final Design and Simulation Circuit 17

3.5 Full Circuit Design of Colpitts Oscillator 18

Chapter 4 PCB Fabrication and Testing 19

4.1 Converting Schematic Design To Microstrip Layout 19

4.2 Eagle 5.4.0 Light and Printed Circuit Board 20

4.3 PCB Fabrication Procedure 21

4.4 Hardware Testing 24

4.5 Measurement and Testing 25

Chapter 5 Conclusion 27

Chapter 6 Future Enhancement 28

References 29

Appendices 30

A1 Comparison of the Subcircuit Components 30

A2 Mini 'C Circuits Understanding VCO Concepts 31

A3 Philips BFG 520 Data Sheet 38

List of Figures

Figure 2.1 Block Diagram for a concept of Harmonic Oscillator [7] 4

Figure 2.2 Simple Common Base Colpitts Oscillator (with simplified biasing) 5

Figure 2.3 Simple Common Collector Colpitts Oscillator (with simplified biasing) 6

Figure 3.1 Start Up Page for ADS 7

Figure 3.2 Stimulate the S 'C Parameters of BFG 520 Transistor 8

Figure 3.3 Input Reflection Coefficient before Input Matching 9

Figure 3.4 Edit Marker Properties 10

Figure 3.5 Configuration of Frequency and Characteristic Impedance 10

Figure 3.6 Input Matching Design for a Series Capacitor by Using Smith Chart Utility 11

Figure 3.7 Input Matching Design for a Shunt Inductor by Using Smith Chart Utility 11

Figure 3.8 Input Matching Designed 12

Figure 3.9 Input Reflection Coefficient After Input Matching 12

Figure 3.10 Output Reflection Coefficient before Output Matching 13

Figure 3.11 Value of S22* is Zs* While ZL is Impedance 50 ohm 13

Figure 3.12 A 4.2nH Series Inductor Chosen To Move From ZL To Zs* 14

Figure 3.13 Output Matching Designed 14

Figure 3.14 Output Reflection Coefficient after Output Matching 15

Figure 3.15 Schematic for a Colpitts Oscillator 17

Figure 3.16 Increasing Value of Frequencies Due To the Harmonic Index 17

Figure 3.17 Schematic for A Colpitts Oscillator With Frequency Tuning Using Varactor 18

Figure 3.18 2.4 GHz Frequency Oscillator Stimulated Result. 18

Figure 4.1 Selection for a Converted Circuit Design Into Microstrip Layout 19

Figure 4.2 Components Will Be Highlighted For Those Unplaced On Schematic Layout 19

Figure 4.3 Complete Connection Of The Components In Schematic Layout 20

Figure 4.4 Eagle Layout Editor for a Circuit Design 20

Figure 4.5 Microstrip Layout 21

Figure 4.6 Epoxy Double Sided FR 'C 4 Board 21

Figure 4.7 PCB Board for Oscillator 22

Figure 4.8 Grounding for a Oscillator PCB Board 22

Figure 4.9 Connection for a Centre Contact Termination 23

Figure 4.10 Grounding for a Contact Plating 23

Figure 4.11 Complete Circuitry With Soldered for an Oscillator 23

Figure 4.12 Spectrum Analyzer Use for Oscillator Testing 24

Figure 4.13 Output Signal 2.402 GHz with Amplitude -9.84dBm 25

Figure 4.14 Output Signal Is 2.4 GHz +/- 0.2% with Amplitude -9.70 dBm 26

List of Tables

Table 1.1 Example of Oscillator Function in Various Applications 2

Table 1.2 Table of Technical Objectives 2

Table 1.3 Frequency Bands and Applications 3

Table 3.1 Stablity Factor Simulation Result for Frequency 2.4GHz 9

Table 3.2 Both S11 and S22 is < -10db 15

Table 3.3 Forward Gain, S21 shown that equal > 3dB 15

Table 5.1 Technical Objectives for a Status and Explanation 27

Table A1.1 Comparison of the Subcircuit Components 30

Chapter 1: Introduction

Background

An oscillator was a key building block for integrated transceivers. Either in wired or wireless terminal of communication, the receiver front 'C end selects amplifies and converts the desired high 'C frequency signal to baseband. At baseband the signal can then be converts into the digital domain for further data processing and demodulation. The transmitter front 'C end converts an analog baseband signal to a suitable high 'C frequency signal that can be transmitted over the wired or wireless channel. Given the wide range of application of wired and wireless transceivers, oscillator specifications differ greatly for each transceiver. [1]

Oscillators are an essential part of all wireless systems. To present an easy-to-understand, unified view of the subject, this thesis will covers the practical design of high-frequency oscillators with lumped component. [2]

Basic Oscillator Theory: [3]

Oscillators are a natural and expected part of the electronic scene. It may occur in many types of applications and make possible circuits and subsystems that perform very useful functions. Oscillators occur sometimes even when we don't want them -- amplifiers can oscillate if stray feedback paths are present.

In most oscillator circuits, oscillation builds up from zero when power is first applied, under linear circuit operation. However amplifier saturation and other non-linear effects end up keeping the oscillator's amplitude from building up indefinitely. Thus, oscillators are not the simplest devices in the world to accurately design simulate or model.

Frequency stability is important because it to enable the narrow 'C band communication systems to be accurately fixed with a frequency band. An unstable frequency oscillator also behaves like an unstable FM modulator and produces unwanted modulation FM noise. However, an amplitude unstable oscillator bahaves like an amplitude modulated modulator because it produce unwanted AM modulation noise. Although, the oscillation frequency and amplitude can be held precisely, it is inevitable that noise will be produced in an osillator because of transistor noisewhich included ''flicker noise'', ''shot noise''and ''1/frequency'' noise. In other words, ocsillator noise is inevitable but it should be kept as low as possible. Low power consumption and small size are specially important in protable equitment. [4]

Project Aim and Scopes

The aim of this project is to design and construction a 2.4GHz oscillator. The oscillator are used to produce the radio frequency signal without an external input signal. Since there is microwave circuit design involved, consequently ADS software from Agilent and also Eagle Layout Editor 5.4.0 will be used along with this project design. ADS can be use for circuit design, and show the simulation results. On the other hand, an Eagle Layout Editor was use for circuit layout improvement. Summary of processes are schematic design, generate the schematic layout for PCB fabrication, SMT components soldering, and lastly to do the hardware testing.

Application Examples

Application Oscillator Function

DECT Low 'C IF receiver Tunable frequency, down 'C conversion

FM radio front 'C end Tunable frequency, down 'C conversion

Satellite tuner Tunable frequency, down 'C conversion

Bluetooth transmission Tunable frequency, up 'C conversion

Baseband digital processing Clock generation

FM radio demodulator Demodulation

Optical transmitter Clock conversion and generation

Optical receiver Carrier regeneration

Table1.1: Example of Oscillator Function in Various Applications [1]

Technical Objective

Objectives

To design a stable 2.4GHz amplifier which can give gain greater than 6dB.

To destabilize the 2.4GHz amplifier (using feedback) so as to create 2.4GHz oscillator.

To implement design using microstrip instead of lump component.

To fabricate the design in PCB.

To test the fabricated design using spectrum analyzer and to tuned the feedback component to get 2.4GHz output.

Table 1.2: Table of Technical Objectives?

Radio Frequency Overview

Table1.3 indicated the 13 different levels of frequency bands such as band name, abbreviation, frequency and wavelength in air also include the example of applications.

Band Name Abbreviation Frequency and Wavelength in Air Example Applications

SubHertz subHz <3 Hz

>100,000km Natural and man-made electromagnectic waves (milihertz, microhertz, nanohertz) from earth, ionosphere, sun, planets

Extremely low frequency ELF 3-30 Hz

100,000km 'C 10,000km Submarines communication

Super low frequency SLF 30 'C 300 Hz

10,000km 'C 1000km Submarines communication

Ultra low frequency ULF 300 'C 3000 Hz

1000km 'C 100km Communication within mines

Very low frequency VLF 3 'C 30 Hz

100km 'C 10km Submarines communication, avalanche beacons, wireless heart rate monitors, geophysics

Low frequency LF 30 'C 300kHz

10km 'C 1km Navigation, time signals AM long wave broadcasting, RFID

Medium frequency MF 300 'C 3000kHz

1km 'C 100m AM (medium 'C wave) broadcasts

High frequency HF 3 'C 30

100m 'C 10m Shortwave broadcasts, amateur radio and over 'C the 'C horizon aviation communications, RFID

Very high frequency VHF 30 'C 300 MHz

10m 'C 1m FM, television broadcasts and aircraft 'C to 'C aircraft communications. Land Mobile and Maritime Mobile communications

Ultra high frequency UHF 300 'C 3000MHz

1m 'C 100mm Television broadcasts, microwave ovens, mobile phones, wireless LAN, Bluetooth, GPS and two 'C way radios such as Land Mobil, FRS and GMRS radios

Super high frequency SHF 3 'C 30 GHz

100mm 'C 10mm Microwave devices, wireless LAN, most modern radars

Extremely high frequency EHF 30 'C 300GHz

10mm 'C 1mm Radio astronomy, high- frequency microwave radio relay

Terahertz THz 300 'C 3,000GHz

1mm 'C 100um Terahertz imaging'Ca potential replacement for X-rays in some medical applications, ultra fast molecular dynamics, condensed'Cmatter physics, terahertz time'Cdomain spectroscopy, terahertz computing/ communications

Table 1.3: Frequency Bands and Applications

Chapter 2: Literature Review

Oscillators can be classified into two types: (A) Relaxation and (B) Harmonic oscillators. [6]

? Relaxation oscillators (also called astable multivibrator), is a class of circuits with two unstable states. The circuit switches back-and-forth between these states. The output is generally square waves.

? Harmonic Oscillators are capable of producing near sinusoidal output, and are based on positive feedback approach. This oscillator for RF systems is used as these classes of circuits are capable of producing stable sinusoidal waveform with low phase nose.

Harmonic oscillator [7]

Harmonic oscillator is mean that the output Vo from an amplifier will fed back into its input Vf through a filter, ''(j'') which as shown as Figure 2.1

Figure 2.1: Block Diagram for a Concept of Harmonic Oscillator [7]

The basic form of this oscillator is in terms of an electronic amplifier connected in a feedback loop the output through an electronic filter fed back into its input. Amplifier''s output consists only of noise signal after the power turn ON. Subsequently the noise travels around the loop, being filtered and re-amplified until it achieved the desired signal. Signal in the loop will becomes a sine wave at a single frequency at the shorted time.

In LC oscillators or know as inductive-capacitive, which is connecting together of an inductor and capacitor inside the filter or called as tuned circuit. The charge will flow back and forth between the capacitor's plates through the inductor, so that name as resonant frequency due to the tuned circuit can be store electrical energy oscillating. The feedback from the amplifier creates a negative resistance that compensates for the internal resistance of the LC circuit, sustaining the oscillations.

Transistor biasing [4]

Basically, for every amplifier circuit design, transistor biasing are needed, following are the objectives of transistor biasing:

To select a suitable operating point for the transistor;

To maintain the chosen operating point with changes in transistor current gain with temperature;

To maintain the chosen operating point with changes in temperature;

To maintain the chosen operating point to minimize changes in the a.c. parameters of the operating transistor;

To prevent thermal runaway, where an increase in collector current with temperature causes overheating, burning and self 'C destruction;

To try to maintain the chosen operating point with changes in supply voltage 'C this is particular true of battery operated equipment where the supply voltage changes considerably as the battery discharges;

To maintain the chosen operating point with changes in '' when a transistor of one type is replaced by another of the same type 'C it is common to find that '' varies from 50% to 300% of its nominal value for the same type of transistor.

The frequency is generally determined by the inductor and the two capacitors as the drawing below.

Figure 2.2: Simple Common Base Colpitts Oscillator (with simplified biasing)

Figure 2.3: Simple Common Collector Colpitts Oscillator (with simplified biasing)

Implementation [8]

A Colpitts oscillator is the electrical dual of a Hartley oscillator. The basic Colpitts circuit as Figure 2.2 shown above, where two capacitors and one inductor will determine the frequency of oscillation. The feedback needed for oscillation is taken from a voltage divider made of two capacitors. However, the feedback is taken from a voltage divider made of two inductors (or a single, tapped inductor) in the Hartley oscillator designed.

For obtain the stable operation, the amplification of the active component should be marginally larger than the attenuation of the capacitive voltage divider no matter with any oscillator. Therefore, a Colpitts oscillator will perform better if used as a variable frequency oscillator (VFO) when a variable inductance is used for tuning, as opposed to tuning one of the two capacitors. Whereas if tuning by variable capacitor is needed, it should be done via a third capacitor in shunt connection to the inductor (or in series as in the Clapp oscillator).

Figure 2.3 shows an amplifier provides current, not voltage, amplification where the inductor is also grounded (with purpose to makes circuit layout easier for higher frequencies). As figure shown, the feedback energy is fed into the connection between the two capacitors.

Chapter 3: Methodology

Software Design

Advanced Design System Overview

There are various types of CAD software to be used by designer or engineer. ADS are one of the CAD software created from Agilent Technologies, Cadence IC Design System, and High frequency Structure Simulator (HFSS).

Figure 3.1: Start Up Page for ADS

[9] ADS is known as the pioneer of industry in high-frequency design. It can be supports all types of RF designs to convenience the RF design engineers for design developing, no matter the applications from simple to the most complex and even from RF/microwave modules to integrated MMICs for communications and aerospace/defense. ADS made for designers fully characterize and optimize their designs. This is within complete set of simulation technologies ranging from frequency and time-domain circuit simulation to electromagnetic field simulation. In addition, an integrated design environment are fully provides system and circuit simulators, along with verification capability 'C eliminating the stops and starts associated with changing design tools mid-cycle, layout, schematic capture and etc. ?

DesignGuides for Expert Help

DesignGuides it makes us do the job of circuit design become easier, faster, and more consistent with wizards, pre-configured set-ups and displays, and step-by-step instructions. These is because of Agilent EEsof EDA has lot of industry experts according to their experience and best practices to came out of these DesignGuides. Complete design applications is easy access to the power of ADS for both expert and novice users without taking longer time to learn from scratch. Included in DesignGuides are oscillator, amplifiers, RF systems, mixers, microstrip circuits, filters, Bluetooth, and ultra wideband designs.

Impedance Matching for Transistor at 2.4GHz

First download the S2P parameter required from transistor manufacturer website [10][11]. Then stimulate the analysis with the S-Parameters setting.

Figure 3.2: Stimulate the S 'C Parameters of BFG 520 Transistor

?

Table3.1: shown the StabFact (Stability Factor) are greater than one for frequency 2.4 GHz.

Table 3.1: Stablity Factor Simulation Result for Frequency 2.4GHz

Smith Chart utility are one of the categories in Advance Design System (ADS), designers will easier to do the impedance matching by used of lumped components.

According to the rule of thumb in industrial, ideally S11 and S22 should be less than -10dB, essentially the need of circuit to match with 50 ohm, Figure 3.3 shown that the Input reflection coefficience, (S11) with impedance value 15.3 + j9.8, obviously the simulation result is not match to the normalise of 50 ohm.

Figure 3.3: Input Reflection Coefficient before Input Matching

If want to get the actual impedance, at edit marker properties change the Zo to 50 at format tab as Figure 3.4 shown.

Figure 3.4: Edit Marker Properties

Frequency and characteristic impedance (Zo) for the circuit is determined as 2.4 GHz and 50 ohm respectively. The unchecked the normalization box as the input reflection coefficient, S11 is not in normalize value.

Figure 3.5: Configuration of Frequency and Characteristic Impedance

From the Smith Chart utility, the source impedance default Zs* = 50 + j0 (where * stand for conjugate for imaginary value) and key in load impedance ZL= 15.3 + j9.8. The series capacitor palette on the left side will be chosen and move the cursor point down until value of Y: is 0.02 (correspond to admittance circle passing through smith chart origin).

Now, the value of series capacitor is required 2.0pF, as show as Figure 3.6.

Figure 3.6: Input Matching Design for a Series Capacitor by Using Smith Chart Utility

Then choose for the parallel (shunt) inductor palette on the left side and move to point up with Zs= 50 + j0 (correspond to smith chart origin). The inductor value is 2.2nH obtained as Figure 3.7

Figure 3.7: Input Matching Design for a Shunt Inductor by Using Smith Chart Utility

Figure 3.8: Input Matching Designed

Input matching network was finished by adding with shunt inductor and series capacitor respectively, the input reflection coefficient, S11 had been matched to 50 ohm within value of 51.09 + j0.532. Figure 3.9 below shown the simulation result of input reflection coefficient, S11.

Figure 3.9: Input Reflection Coefficient After Input Matching

With the similar procedure, the output reflection coefficient, S22 the default Zs* = 48.5 + j63 (* stand for conjugate for imaginary value in this case S22 value of 48.5 - j63).

Figure 3.10: Output Reflection Coefficient before Output Matching

For output matching, value of S22* is the Zs* while line impedance 50 ohm is ZL as shown as Figure 3.11.

Figure 3.11: Value of S22* is Zs* While ZL is Impedance 50 ohm

So, a series inductor chosen to move from ZL to Zs* where the series inductor value is 4.2nH as Figure 3.12 below.

Figure 3.12: A 4.2nH Series Inductor Chosen To Move From ZL To Zs*

Figure 3.13: Output Matching Designed

After output matching network was finished by adding with series inductor, the output reflection coefficient, S22 had been matched to 50 ohm within value of 48.5 + j0.3. Figure 3.14 shown the simulation result of output reflection coefficient, S22.

Figure 3.14: Output Reflection Coefficient after Output Matching

Table 3.2 shows that the both S11 and S22 are less than -10db consider as best value for most application. In case needs of further optimization function, there have to enable the Optim/Stat/Yield/DOE Palette at the components respectively.

Table 3.2: Both S11 and S22 is < -10db

On the other hand, value of forward gain, S21are greater than 3dB as red rectangular as shows Figure 3.15 below.

Table 3.3: Forward Gain, S21 Shown That Equal > 3db

Oscillation Frequency

Following is the parameter for transistor BFG520 SPICE MODEL used:

RB = 1.00000E+001

RE = 7.75349E-001

RC = 2.21E+000

RT= RB+RE + RC = 13 ohm (series resistance of resonant)

Gm=1/RT = 0.077 Siemens

[12] In can be proven (refer appendix MINI-CIRCUIT- Understanding VCO Concepts) that

Zin = (V in)/(I in)= 1/j''C1+ 1/j''C2- Gm/''C1C2'Ø¡'^2

For oscillation to occur Gm/''C1C2'Ø¡'^2 must be greater than RT so that we have negative impedance.

Rule of thumb, let Gm/''C1C2'Ø¡'^2 = 2 RT = 2(13) = 26 ohm

Then C1C2 = Gm/''26'Ø¡'^2 = 1.30 x 10-23

Let C1 = C2 = (1.30 x 10-23)0.5 = 3.61pF = 3.9pF (closest standard value).

When C1 = C2 = 3.9pF

Since Ceff = (C1 .C2)/(C1+C2) = 1.95pF

Colpitts oscillator

''(Oscillation frequency f =&1/(2'С'(L . (C1 .C2)/(C1+C2))))

''(LC_eff=&1/(2''f)^2 )|''(@LC_eff= 1/((''2'С'2.4G)''^2 )@@=''4.4''10''^(-21)@@Required inductor L=4.4'a'10''^(-21)/ 1.95pF@@=2.2nH)

?

Final Designed and Simulation Circuit

A Generic Oscillator created base on LC oscillator. It is because an inductance (L) combined with a capacitor (C) for the frequency determination.[7] For Colpitts oscillator, the feedback signal is from a voltage divider which is connection of two series capacitors. Figure 3.15 shows the schematics.

Figure 3.15: Schematic for a Colpitts Oscillator

Result obtained as Figure 3.16 indicated that the frequency will increase for every harmonic index. The values of frequency are multiply of basic index frequency fo=2.414 GHz.

Figure 3.16: Increasing Value of Frequencies Due To the Harmonic Index

Full Circuit Design of Colpitts Oscillator

Figure 3.17: Schematic for A Colpitts Oscillator With Frequency Tuning Using Varactor.

Figure 3.18: 2.4 GHz Frequency Oscillator Stimulated Result.

?

Chapter 4: PCB Fabrication and Testing

Converting Schematic Design To Microstrip Layout

After the oscillator design is completed, the next step is converted the circuit design into microstrip layout. Function of the ''Place the Components from Schem to Layout'' in ADS software is selected as following:

Figure 4.1: Selection for a Converted Circuit Design Into Microstrip Layout

Schematic layout will generated after the function selected, automatically which components are unplaced will be showed and highlighted as Figure 4.2 below:

Figure 4.2: Components Will Be Highlighted For Those Unplaced On Schematic Layout

Figure 4.3: Complete Connection Of The Components In Schematic Layout

However the Schematic layout generated by ADS is non-satisfactory with very poor grounding and error in component size and spacing. Design to make Schematic layout manually using Eagle.

Eagle 5.4.0 Light and Printed Circuit Board

Eagle software is another method for circuit design especially for those novice users although it cannot be run for compilation and even simulation. Consequently, those novice users can overcome the problems for height, width and distance between the padding.

Figure 4.4: Eagle Layout Editor for a Circuit Design ?

PCB Fabrication Procedure[12]

The microstrip circuitry of the layout is printed on a piece of blank paper. Then cut the paper according to the size as Figure 4.5 below.

Figure 4.5: Microstrip Layout

Double sided FR-4 board is used for the fabrication. Top side of the board will be used for the microstrip layout and soldered with the components. The bottom side of the board are used as ground to the top side by via (connection between top and bottom through drilled holes).

PCB of GD series from Kinsten manufacturer will be to use for this project and the information of this board are as below:

Material 'C GD: Glass 'C Epoxy Double Sided FR 'C 4

Thickness 'C 1.6mm

Copper Foil 'C 1oz

Width 'C 100mm

Length 'C 150mm

Figure 4.6: Epoxy Double Sided FR 'C 4 Board

Placed the microstrip layout into the Ultra Violet (UV) exposure unit then placed the PCB board carefully onto the layout after peeled off the photo resist layer. Next, switch on the exposure unit by setting exposing for 500seconds.

After 500seconds, the PCB board was dipping and keeps stirred into the developer name as Sodium Hydroxide which is PCB board chemical solution until the design approach appeared.

Next, placed that PCB board into the etching tank infused with chemical of Ferric Chloride (FeCl3) for remove the copper foil which is not in used at the circuitry.

Consequently, wash the PCB board with detergent solution to neutralize the Ferric Chloride (FeCl3).

There is important to make sure that overall components are connected as designed and the unneeded copper areas are fully removed. Then begin to drill for the grounding path (for via) as show as Figure 4.7.

Figure 4.7: PCB Board for Oscillator

Grounding has been soldered from top side to bottom as Figure 4.8

Figure 4.8: Grounding for a Oscillator PCB Board

An important thing is, the centre contact termination is connected to the output as Figure 4.9, and the contact plating are connected to ground as show Figure 4.10.

Figure 4.9: Connection for a Centre Contact Termination

Figure 4.10: Grounding for a Contact Plating

Surface Mount Devices (SMD) and the SubMiniature version A (SMA) connector are soldered on the microstrip line. Figure 4.11 as below shown the complete circuitry with soldered.

Figure 4.11: Complete Circuitry With Soldered for an Oscillator ?

Hardware Testing

Need of apparatus and parameters for this output signal analysis is:

1 unit of power supply set to 5 Volt and 0.05 Ampere

1 unit of Agilent CSA N1996A 100 kHz 'C 6 GHz Spectrum Analyzer

1 unit of digital multimeter set to DC voltage mode.

When finished with measurement set up, connect the SMA probe from oscillator output to spectrum analyzer input. Then connect the wires power supply to the oscillator terminal and turn ON the power as Figure 4.12.

Figure 4.12: Spectrum Analyzer Use for Oscillator Testing

Set Agilent CSA N1996A start frequency 1GHz and stop frequency 6GHz.

Tune the frequency by adjusting the voltage across the varactor using a potential meter.

Press the peak search button to find the peak oscillation frequency. Save the data once the signal is stable.

?

Measurement and Discussion

Figure 4.13 shown the output signal 2.402 GHz with amplitude -9.84dBm

Figure 4.13: Output Signal 2.402 GHz with Amplitude -9.84dBm.

Figure 4.14: Output Signal Is 2.4 GHz +/- 0.2% with Amplitude -9.70 dBm

Both of the figure above shown that the output frequency 2.4 GHz +/- 0.2% is achievable. The actual 2.4GHz signal amplitude is smaller than simulation probably because stimulation is using ideal components (without parasites and losses) and also ignore the losses at the copper track.

Chapter 5: Conclusion

As a conclusion, a 2.4GHz oscillator was done with design approach and hardware fabricated. Furthermore, the design and simulation technique for oscillator has been illustrated through the thesis.

Objectives Status and Explanation

To design a stable 2.4GHz amplifier this can give gain greater than 6db.

Stimulation result with impedance matching give S21 equal > 3dB, so will have power gain > 6dB.

To destabilize the 2.4GHz amplifier (using feedback) so as to create 2.4GHz oscillator. Simulation result show on Figure 3.18 value of 2.4GHz obtained.

To implement design using microstrip instead of lump component.

Found that design can be implemented more effectively using lump component. Therefore implement design using lump component instead of microstrip/distributed component.

To fabricate the design in PCB. Achieved. Double sided PCB of FR-4 type is used for this project, which is particular for microwave circuit design.

To test the fabricated design using spectrum analyzer and to tuned the feedback component to get 2.4GHz output. Achieved. Measurement signal 2.4GHz ''0.2%.

Table 5.1: Technical Objectives for a Status and Explanation ?

Chapter 6: Future Enhancement

Reducing the number of components

Obviously, the more components used, both power consumption and cost of production will be increase. Furthermore heat and noise might be produced for each component.

Therefore have to optimize the design further to reduce the number of component used.

Reducing sizes of the design.

Circuitry design can become smaller in order to reduce cost and physical size of PCB board.

More accurate simulation and design

Should take into consideration the actual performance of all the components by using measured S-parameter of all components used. Model the microstrip parasitic losses in order to predict the amplitude of oscillation signal more accurately.

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