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Circuits Hyperfrequences - Semestre 3

Annee: 2021-2022 | Semestre: 3 | Type: Technique

PART A - Presentation Generale du Cours

Contexte et objectifs

Ce cours de S3 specialisation ENOC introduit la conception de circuits fonctionnant aux frequences RF et micro-ondes (100 MHz - 10+ GHz). Il combine theorie electromagnetique, simulation EM 3D et realisation pratique sur PCB, avec caracterisation par analyseur de reseau vectoriel.

Objectifs principaux :

  • Maitriser les technologies de circuits RF planaires (microstrip, stripline, CPW)
  • Concevoir filtres, adaptations d'impedance, diviseurs de puissance
  • Simuler avec outils EM professionnels (ADS Momentum, HFSS, CST)
  • Fabriquer sur PCB et mesurer avec VNA
  • Comprendre phenomenes HF : effet de peau, pertes dielectriques, couplages

Prerequis

  • Propagation et Hyperfrequences S3 (lignes de transmission, Smith chart, parametres S)
  • Electronique analogique (composants passifs, filtrage)
  • Conception PCB (ER S1-S2)

PART B: EXPERIENCE, CONTEXTE ET FONCTION

Module 1 : Technologies RF sur PCB

Substrats RF :

  • FR-4 : er~4.3-4.7, tan d~0.02, economique, limite <3 GHz
  • Rogers RO4003/RO4350 : er stable (3.38/3.48), faibles pertes, 0-10+ GHz
  • PTFE/Teflon : er~2.1, tres faibles pertes, difficile a usiner

Lignes microstrip :

  • Calcul largeur pour Z0=50 Ohm : W~3mm (FR-4 1.6mm), er_eff~3.2
  • Pertes : conducteur (cuivre) + dielectrique (tan d)
  • Applications : alimentations, adaptations

Composants passifs RF :

  • Resistances 50 Ohm (charges, attenuateurs)
  • Condensateurs RF CMS (resonance serie SRF critique)
  • Inductances (bobines air, CMS, facteur Q)
  • Vias de masse (stitching lambda/10)

Module 2 : Circuits d'adaptation et filtres

Reseaux d'adaptation localises (L, pi, T) :

  • Transformation impedance avec L/C CMS
  • Calcul par Smith chart
  • Bande etroite

Adaptation distribuee :

  • Stub simple (serie/parallele) : position et longueur
  • Ligne lambda/4 : Z_lambda/4 = sqrt(Z1 * Z2)
  • Double stub : positions fixes 3lambda/8

Filtres microstrip :

  • Passe-bas/haut/bande a elements localises
  • Filtres a stubs (bande-stop)
  • Filtres a lignes couplees (passe-bande)
  • Synthese : Butterworth, Chebyshev

Coupleurs et diviseurs :

  • Diviseur Wilkinson : division egale, isolation, resistance 100 Ohm
  • Coupleur directionnel : couplage -3/-10/-20 dB
  • Rat-race : 180 deg hybrid, 3lambda/2 circonference

Module 3 : Simulation EM

Logiciels professionnels :

  • ADS Momentum : 2.5D planar, rapide
  • HFSS : 3D FEM, precis
  • CST : 3D temps/frequence
  • Sonnet : 2.5D, gratuit version limitee

Workflow simulation :

  1. Schematique circuit (calcul initial)
  2. Layout PCB (dessin geometrie)
  3. Simulation EM 3D (champs, courants)
  4. Optimisation parametres
  5. Validation specs (S-parameters)

Parametres analyses :

  • S11 (adaptation), S21 (transmission)
  • Champs E et H
  • Courants de surface
  • Pertes (conducteur, dielectrique, rayonnement)

PART C: ASPECTS TECHNIQUES

Projets pratiques

Projet 1 : Filtre passe-bande 2.4 GHz

  • Specs : f0=2.4 GHz, BW=200 MHz, IL<3 dB
  • Topologie : lignes couplees ou stubs
  • Simulation ADS → Layout → Fabrication PCB → Mesure VNA

Projet 2 : Diviseur Wilkinson

  • Division 50 Ohm → 2x50 Ohm
  • Lignes lambda/4 a 70.7 Ohm
  • Isolation >20 dB

Projet 3 : Adaptation stub

  • Charge complexe ZL → 50 Ohm
  • Calcul Smith chart
  • Stub court-circuit ou ouvert

Caracterisation VNA

Calibration :

  • SOLT : Short, Open, Load, Thru
  • TRL pour substrats specifiques
  • Kit de calibration precis

Mesures :

  • Parametres S (magnitude, phase)
  • Smith chart impedance
  • TDR (Time Domain Reflectometry)
  • Comparaison simulation vs mesure

Fabrication PCB RF

Fichiers Gerber :

  • Couches cuivre (Top, Bottom)
  • Plans de masse continus
  • Drill (vias)
  • Soldermask, Silkscreen

Fabricants :

  • PCBWay, JLCPCB (economique)
  • Eurocircuits (professionnel EU)
  • Specifier : substrat, epaisseur, er, finition (ENIG recommande RF)

PART D: ANALYSE ET REFLEXION

Evaluation

  • Projets simulation + realisation (60%)
  • Mesures et rapports (25%)
  • Examen theorique (15%)

Competences acquises

  • Simulation EM 3D professionnelle
  • Conception circuits RF planaires
  • Utilisation VNA
  • Optimisation performances RF
  • Design for Manufacturing RF

Applications industrielles

  • Telecommunications (WiFi, 4G/5G, satellite)
  • IoT (LoRa, Sigfox, Bluetooth)
  • Radar automobile
  • Instrumentation RF

Technologies de circuits RF

Substrats RF

FR-4 :

  • er ~ 4.3-4.7 (variable)
  • tan d ~ 0.02 (pertes elevees)
  • Economique
  • Limite a quelques GHz

Rogers (RO4003, RO4350) :

  • er stable (3.38, 3.48)
  • tan d faible (0.0027)
  • Bon jusqu'a 10+ GHz
  • Plus cher

PTFE/Teflon :

  • er ~ 2.1-2.5
  • tan d tres faible
  • Hautes performances
  • Difficile a usiner

Lignes de transmission sur PCB

Microstrip :

  • Ligne sur face superieure
  • Plan de masse en dessous
  • Facile a fabriquer
  • Emissions rayonnees

Stripline :

  • Ligne entre deux plans de masse
  • Bien blindee
  • PCB multicouche requis

Coplanar waveguide (CPW) :

  • Plans de masse sur meme face
  • Bon pour composants CMS
  • Bonne isolation

Composants passifs RF

Resistances

  • Charges 50 Ohm
  • Attenuateurs
  • Terminaisons
  • Modeles hautes frequences

Condensateurs

  • Capacites de decouplage
  • Resonance serie (SRF)
  • ESL et ESR
  • Condensateurs RF (ATC, AVX)

Inductances

  • Bobines air
  • Inductances CMS
  • Facteur de qualite Q
  • Auto-resonance

Vias

  • Via de masse (stitching)
  • Via thermique
  • Inductance parasite
  • Espacement recommande

Circuits d'adaptation

Reseaux L, pi, T

  • Composants localises
  • Calcul analytique
  • Simulation (Smith chart)
  • Realisation CMS

Adaptation distribuee

  • Stubs microstrip
  • Lignes lambda/4
  • Multi-sections
  • Large bande

Filtres RF

Filtres a elements localises

  • Passe-bas, passe-haut, passe-bande
  • Butterworth, Chebyshev
  • Transformation LC
  • Realisation CMS

Filtres distribues

  • Filtres a stubs
  • Filtres a lignes couplees
  • Filtres interdigites
  • Resonateurs

Coupleurs et diviseurs

Coupleur directionnel

  • Couplage -3dB, -10dB, -20dB
  • Isolation
  • Directivite
  • Applications (mesure, feedback)

Diviseur de Wilkinson

  • Division de puissance egale
  • Isolation entre sorties
  • Impedances 50 Ohm
  • Resistance d'isolation

Rat-race (anneau hybride)

  • Combineur/diviseur 180 deg
  • 4 ports
  • lambda_g x 3/2 circonference

Oscillateurs RF

Oscillateurs a quartz

  • Frequence fixe precise
  • Stabilite
  • TCXO, OCXO

VCO (Voltage Controlled Oscillator)

  • Frequence variable
  • PLL (Phase-Locked Loop)
  • Plage d'accord
  • Bruit de phase

Amplificateurs RF

Classes d'amplification

  • Classe A (lineaire)
  • Classe B, AB (push-pull)
  • Classe C (RF, non lineaire)
  • Classe E, F (commutation)

Caracteristiques

  • Gain (dB)
  • P1dB (point de compression a 1dB)
  • IP3 (point d'interception d'ordre 3)
  • Facteur de bruit (NF)
  • Stabilite (K-factor, mu)

Travaux pratiques

Conception de composants RF

Projet 1 : Filtre passe-bande

  • Specifications (f0, BW, IL)
  • Calcul et simulation
  • Layout PCB
  • Caracterisation

Projet 2 : Diviseur de puissance

  • Wilkinson 50 Ohm
  • Simulation EM
  • Fabrication
  • Mesure parametres S

Projet 3 : Ligne d'adaptation

  • Stub ou lambda/4
  • Dimensionnement
  • Optimisation
  • Tests sur VNA

Simulation et conception

Etapes

  1. Calcul theorique : Formules, Smith chart
  2. Simulation circuit : Schematique
  3. Simulation EM : Layout 3D
  4. Optimisation : Tuning parametres
  5. Generation Gerber : Fabrication

Fabrication

Methodes

  • Gravure chimique : Proto rapide
  • Fraiseuse CNC : Precision
  • Fabrication professionnelle : Production

Fichiers necessaires

  • Gerber (couches cuivre)
  • Drill (percages)
  • Soldermask (vernis)
  • Silkscreen (serigraphie)

Caracterisation

Mesures avec VNA

  • Calibration (SOLT, TRL)
  • Parametres S (S11, S21)
  • Smith chart
  • Comparaison simulation/mesure

Parametres mesures

  • Pertes d'insertion (IL)
  • Pertes de retour (RL)
  • Isolation
  • Bande passante
  • Impedance

Outils utilises

Simulation RF

  • ADS (Advanced Design System) : Keysight
  • AWR Microwave Office : Cadence
  • Qucs : Open source
  • LTspice : Circuits RF

Simulation EM

  • Momentum : Integre ADS (2.5D)
  • HFSS : Ansys (3D)
  • CST Microwave Studio : 3D
  • Sonnet : 2.5D planar

CAO PCB

  • Altium Designer
  • KiCad : Open source
  • Eagle
  • PADS

Mesure

  • Analyseur de reseau vectoriel (VNA)
  • Analyseur de spectre
  • Generateur RF
  • Oscilloscope haute frequence

Exemples de dimensionnement

Ligne microstrip 50 Ohm (FR-4, h=1.6mm)

  • Largeur W ~ 3 mm
  • er = 4.3
  • er_eff ~ 3.2
  • Z0 = 50 Ohm

Stub lambda/4 a 2.4 GHz

  • lambda_0 = 125 mm
  • lambda_g = lambda_0/sqrt(er_eff) ~ 70 mm
  • Longueur stub ~ 17.5 mm

Diviseur Wilkinson 2.4 GHz

  • Lignes lambda/4 a 70.7 Ohm
  • Resistance isolation 100 Ohm
  • Impedance entree/sorties 50 Ohm

Regles de conception RF

Layout PCB

  • Plans de masse : Continus, via stitching
  • Largeur de piste : Controlee (50 Ohm)
  • Courbures : Rayon > 3x largeur
  • Espacement : Eviter couplages parasites
  • Vias : Minimiser sur lignes RF

Decouplage

  • Condensateurs proches des composants
  • Multiple valeurs (nF, uF)
  • Via court vers masse
  • Plans de masse separes (analogique/numerique)

Blindage

  • Boitier metallique si necessaire
  • Cloisons entre sections
  • Absorption RF (ferrites, mousses)

Competences developpees

  • Simulation EM 3D
  • Conception de circuits RF sur PCB
  • Utilisation d'analyseur de reseau
  • Optimisation de performances RF
  • Fabrication de circuits micro-ondes
  • Analyse de resultats de mesure

Phenomenes hautes frequences

Effet de peau

  • Profondeur de penetration delta
  • Resistance AC > DC
  • Depend de la frequence
  • Cuivre argente pour ameliorer

Pertes dielectriques

  • tan d du substrat
  • Augmentent avec frequence
  • Chauffage du PCB
  • Choix substrat crucial

Couplages

  • Couplage capacitif (E-field)
  • Couplage inductif (H-field)
  • Couplage par substrat
  • Espacement et blindage

Modes parasites

  • Modes de cavite
  • Resonances indesirables
  • Rayonnement
  • Via fencing pour mitiger

Erreurs a eviter

Conception

  • Plans de masse discontinus
  • Lignes d'impedance non controlee
  • Transitions brusques (stubs, angles droits)
  • Sous-estimation des pertes

Fabrication

  • Epaisseur cuivre non uniforme
  • Gravure excessive ou insuffisante
  • Desalignement des couches
  • Qualite soudures CMS RF

Mesure

  • Calibration inadequate
  • Connecteurs mal serres
  • Cables endommages
  • Gamme de frequence incorrecte

Processus de conception typique

Phase 1 : Specifications

  • Frequence de travail
  • Impedance (50 Ohm typique)
  • Performances requises
  • Contraintes (taille, cout)

Phase 2 : Conception theorique

  • Calculs analytiques
  • Choix de topologie
  • Simulation schematique
  • Validation concept

Phase 3 : Layout et EM

  • Dessin PCB
  • Simulation EM 3D
  • Optimisation dimensions
  • Verification DRC

Phase 4 : Fabrication

  • Generation fichiers Gerber
  • Choix fabricant
  • Reception et inspection
  • Assemblage CMS

Phase 5 : Test

  • Calibration VNA
  • Mesures parametres S
  • Comparaison avec simulation
  • Ajustements (tuning)

Ressources

  • Application notes fabricants (Mini-Circuits, Analog Devices)
  • "Microwave Engineering" - Pozar
  • "RF Circuit Design" - Bowick
  • Tutoriels ADS/AWR
  • Calculateurs en ligne (impedance, attenuation)

Microwave Circuits - Semester 3

Year: 2021-2022 | Semester: 3 | Type: Technical

PART A - General Course Overview

Context and objectives

This S3 ENOC specialization course introduces the design of circuits operating at RF and microwave frequencies (100 MHz - 10+ GHz). It combines electromagnetic theory, 3D EM simulation and practical PCB fabrication, with characterization using a vector network analyzer.

Main objectives:

  • Master planar RF circuit technologies (microstrip, stripline, CPW)
  • Design filters, impedance matching networks, power dividers
  • Simulate with professional EM tools (ADS Momentum, HFSS, CST)
  • Fabricate on PCB and measure with VNA
  • Understand HF phenomena: skin effect, dielectric losses, coupling

Prerequisites

  • Propagation and Microwaves S3 (transmission lines, Smith chart, S-parameters)
  • Analog electronics (passive components, filtering)
  • PCB design (ER S1-S2)

PART B: EXPERIENCE, CONTEXT AND FUNCTION

Module 1: RF technologies on PCB

RF substrates:

  • FR-4: er~4.3-4.7, tan d~0.02, economical, limited <3 GHz
  • Rogers RO4003/RO4350: stable er (3.38/3.48), low losses, 0-10+ GHz
  • PTFE/Teflon: er~2.1, very low losses, difficult to machine

Microstrip lines:

  • Width calculation for Z0=50 Ohm: W~3mm (FR-4 1.6mm), er_eff~3.2
  • Losses: conductor (copper) + dielectric (tan d)
  • Applications: feeds, matching

RF passive components:

  • 50 Ohm resistors (loads, attenuators)
  • RF SMD capacitors (series resonance SRF critical)
  • Inductors (air coils, SMD, Q factor)
  • Ground vias (stitching lambda/10)

Module 2: Matching circuits and filters

Lumped matching networks (L, pi, T):

  • Impedance transformation with SMD L/C
  • Smith chart calculation
  • Narrowband

Distributed matching:

  • Single stub (series/parallel): position and length
  • Lambda/4 line: Z_lambda/4 = sqrt(Z1 * Z2)
  • Double stub: fixed positions 3lambda/8

Microstrip filters:

  • Low-pass/high-pass/bandpass with lumped elements
  • Stub filters (band-stop)
  • Coupled-line filters (bandpass)
  • Synthesis: Butterworth, Chebyshev

Couplers and dividers:

  • Wilkinson divider: equal division, isolation, 100 Ohm resistor
  • Directional coupler: -3/-10/-20 dB coupling
  • Rat-race: 180 deg hybrid, 3lambda/2 circumference

Module 3: EM simulation

Professional software:

  • ADS Momentum: 2.5D planar, fast
  • HFSS: 3D FEM, accurate
  • CST: 3D time/frequency
  • Sonnet: 2.5D, free limited version

Simulation workflow:

  1. Circuit schematic (initial calculation)
  2. PCB layout (geometry drawing)
  3. 3D EM simulation (fields, currents)
  4. Parameter optimization
  5. Spec validation (S-parameters)

Analyzed parameters:

  • S11 (matching), S21 (transmission)
  • E and H fields
  • Surface currents
  • Losses (conductor, dielectric, radiation)

PART C: TECHNICAL ASPECTS

Practical projects

Project 1: 2.4 GHz bandpass filter

  • Specs: f0=2.4 GHz, BW=200 MHz, IL<3 dB
  • Topology: coupled lines or stubs
  • ADS simulation → Layout → PCB fabrication → VNA measurement

Project 2: Wilkinson divider

  • 50 Ohm division → 2x50 Ohm
  • Lambda/4 lines at 70.7 Ohm
  • Isolation >20 dB

Project 3: Stub matching

  • Complex load ZL → 50 Ohm
  • Smith chart calculation
  • Short-circuit or open stub

VNA characterization

Calibration:

  • SOLT: Short, Open, Load, Thru
  • TRL for specific substrates
  • Precision calibration kit

Measurements:

  • S-parameters (magnitude, phase)
  • Smith chart impedance
  • TDR (Time Domain Reflectometry)
  • Simulation vs measurement comparison

RF PCB fabrication

Gerber files:

  • Copper layers (Top, Bottom)
  • Continuous ground planes
  • Drill (vias)
  • Soldermask, Silkscreen

Manufacturers:

  • PCBWay, JLCPCB (economical)
  • Eurocircuits (professional EU)
  • Specify: substrate, thickness, er, finish (ENIG recommended for RF)

PART D: ANALYSIS AND REFLECTION

Assessment

  • Simulation + fabrication projects (60%)
  • Measurements and reports (25%)
  • Theoretical exam (15%)

Skills acquired

  • Professional 3D EM simulation
  • Planar RF circuit design
  • VNA usage
  • RF performance optimization
  • RF Design for Manufacturing

Industrial applications

  • Telecommunications (WiFi, 4G/5G, satellite)
  • IoT (LoRa, Sigfox, Bluetooth)
  • Automotive radar
  • RF instrumentation

RF circuit technologies

RF substrates

FR-4:

  • er ~ 4.3-4.7 (variable)
  • tan d ~ 0.02 (high losses)
  • Economical
  • Limited to a few GHz

Rogers (RO4003, RO4350):

  • Stable er (3.38, 3.48)
  • Low tan d (0.0027)
  • Good up to 10+ GHz
  • More expensive

PTFE/Teflon:

  • er ~ 2.1-2.5
  • Very low tan d
  • High performance
  • Difficult to machine

Transmission lines on PCB

Microstrip:

  • Line on top face
  • Ground plane below
  • Easy to fabricate
  • Radiated emissions

Stripline:

  • Line between two ground planes
  • Well shielded
  • Multilayer PCB required

Coplanar waveguide (CPW):

  • Ground planes on same face
  • Good for SMD components
  • Good isolation

RF passive components

Resistors

  • 50 Ohm loads
  • Attenuators
  • Terminations
  • High frequency models

Capacitors

  • Decoupling capacitors
  • Series resonance (SRF)
  • ESL and ESR
  • RF capacitors (ATC, AVX)

Inductors

  • Air coils
  • SMD inductors
  • Quality factor Q
  • Self-resonance

Vias

  • Ground via (stitching)
  • Thermal via
  • Parasitic inductance
  • Recommended spacing

Matching circuits

L, pi, T networks

  • Lumped components
  • Analytical calculation
  • Simulation (Smith chart)
  • SMD implementation

Distributed matching

  • Microstrip stubs
  • Lambda/4 lines
  • Multi-section
  • Wideband

RF filters

Lumped element filters

  • Low-pass, high-pass, bandpass
  • Butterworth, Chebyshev
  • LC transformation
  • SMD implementation

Distributed filters

  • Stub filters
  • Coupled-line filters
  • Interdigital filters
  • Resonators

Couplers and dividers

Directional coupler

  • Coupling -3dB, -10dB, -20dB
  • Isolation
  • Directivity
  • Applications (measurement, feedback)

Wilkinson divider

  • Equal power division
  • Output isolation
  • 50 Ohm impedances
  • Isolation resistor

Rat-race (hybrid ring)

  • 180 deg combiner/divider
  • 4 ports
  • lambda_g x 3/2 circumference

RF oscillators

Crystal oscillators

  • Precise fixed frequency
  • Stability
  • TCXO, OCXO

VCO (Voltage Controlled Oscillator)

  • Variable frequency
  • PLL (Phase-Locked Loop)
  • Tuning range
  • Phase noise

RF amplifiers

Amplification classes

  • Class A (linear)
  • Class B, AB (push-pull)
  • Class C (RF, nonlinear)
  • Class E, F (switching)

Characteristics

  • Gain (dB)
  • P1dB (1dB compression point)
  • IP3 (third-order intercept point)
  • Noise figure (NF)
  • Stability (K-factor, mu)

Practical work

RF component design

Project 1: Bandpass filter

  • Specifications (f0, BW, IL)
  • Calculation and simulation
  • PCB layout
  • Characterization

Project 2: Power divider

  • 50 Ohm Wilkinson
  • EM simulation
  • Fabrication
  • S-parameter measurement

Project 3: Matching line

  • Stub or lambda/4
  • Sizing
  • Optimization
  • VNA testing

Simulation and design

Steps

  1. Theoretical calculation: Formulas, Smith chart
  2. Circuit simulation: Schematic
  3. EM simulation: 3D layout
  4. Optimization: Parameter tuning
  5. Gerber generation: Fabrication

Fabrication

Methods

  • Chemical etching: Rapid prototyping
  • CNC milling: Precision
  • Professional fabrication: Production

Required files

  • Gerber (copper layers)
  • Drill (drilling)
  • Soldermask (varnish)
  • Silkscreen (marking)

Characterization

VNA measurements

  • Calibration (SOLT, TRL)
  • S-parameters (S11, S21)
  • Smith chart
  • Simulation/measurement comparison

Measured parameters

  • Insertion loss (IL)
  • Return loss (RL)
  • Isolation
  • Bandwidth
  • Impedance

Tools used

RF simulation

  • ADS (Advanced Design System): Keysight
  • AWR Microwave Office: Cadence
  • Qucs: Open source
  • LTspice: RF circuits

EM simulation

  • Momentum: Integrated in ADS (2.5D)
  • HFSS: Ansys (3D)
  • CST Microwave Studio: 3D
  • Sonnet: 2.5D planar

PCB CAD

  • Altium Designer
  • KiCad: Open source
  • Eagle
  • PADS

Measurement

  • Vector Network Analyzer (VNA)
  • Spectrum analyzer
  • RF generator
  • High frequency oscilloscope

Sizing examples

50 Ohm microstrip line (FR-4, h=1.6mm)

  • Width W ~ 3 mm
  • er = 4.3
  • er_eff ~ 3.2
  • Z0 = 50 Ohm

Lambda/4 stub at 2.4 GHz

  • lambda_0 = 125 mm
  • lambda_g = lambda_0/sqrt(er_eff) ~ 70 mm
  • Stub length ~ 17.5 mm

Wilkinson divider 2.4 GHz

  • Lambda/4 lines at 70.7 Ohm
  • 100 Ohm isolation resistor
  • 50 Ohm input/output impedance

RF design rules

PCB layout

  • Ground planes: Continuous, via stitching
  • Track width: Controlled (50 Ohm)
  • Bends: Radius > 3x width
  • Spacing: Avoid parasitic coupling
  • Vias: Minimize on RF lines

Decoupling

  • Capacitors close to components
  • Multiple values (nF, uF)
  • Short via to ground
  • Separate ground planes (analog/digital)

Shielding

  • Metal enclosure if necessary
  • Partitions between sections
  • RF absorption (ferrites, foams)

Skills developed

  • 3D EM simulation
  • RF circuit design on PCB
  • Network analyzer usage
  • RF performance optimization
  • Microwave circuit fabrication
  • Measurement result analysis

High frequency phenomena

Skin effect

  • Penetration depth delta
  • AC resistance > DC
  • Frequency dependent
  • Silver-plated copper for improvement

Dielectric losses

  • Substrate tan d
  • Increase with frequency
  • PCB heating
  • Substrate choice crucial

Coupling

  • Capacitive coupling (E-field)
  • Inductive coupling (H-field)
  • Substrate coupling
  • Spacing and shielding

Parasitic modes

  • Cavity modes
  • Unwanted resonances
  • Radiation
  • Via fencing to mitigate

Mistakes to avoid

Design

  • Discontinuous ground planes
  • Uncontrolled impedance lines
  • Abrupt transitions (stubs, right angles)
  • Underestimating losses

Fabrication

  • Non-uniform copper thickness
  • Excessive or insufficient etching
  • Layer misalignment
  • RF SMD solder quality

Measurement

  • Inadequate calibration
  • Loose connectors
  • Damaged cables
  • Incorrect frequency range

Typical design process

Phase 1: Specifications

  • Operating frequency
  • Impedance (50 Ohm typical)
  • Required performance
  • Constraints (size, cost)

Phase 2: Theoretical design

  • Analytical calculations
  • Topology choice
  • Schematic simulation
  • Concept validation

Phase 3: Layout and EM

  • PCB drawing
  • 3D EM simulation
  • Dimension optimization
  • DRC verification

Phase 4: Fabrication

  • Gerber file generation
  • Manufacturer selection
  • Reception and inspection
  • SMD assembly

Phase 5: Test

  • VNA calibration
  • S-parameter measurements
  • Comparison with simulation
  • Adjustments (tuning)

Resources

  • Manufacturer application notes (Mini-Circuits, Analog Devices)
  • "Microwave Engineering" - Pozar
  • "RF Circuit Design" - Bowick
  • ADS/AWR tutorials
  • Online calculators (impedance, attenuation)

Circuits et Fonctions Hyperfrequences

Microwave Circuits and Functions

Support de cours complet sur les circuits hyperfrequences : lignes de transmission, adaptation d'impedance, filtres HF et composants passifs distribues.

Complete course material on microwave circuits: transmission lines, impedance matching, HF filters and distributed passive components.

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