Introduction Passive and Active Microwave … Physics and Quasioptics: Passive and Active...

Microwave Physicsand Quasioptics:

Passive and ActiveRF-Components

Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

1

Microwave Physics and Quasioptics:

Passive and Active Microwave Components

Axel Murk

Institute of Applied PhysicsUniversity of Bern

13.10.2009



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

2

Objective

I Basic overview of the microwave hardware that is usedat our institute (and in all modern communication andnavigation equipment).

I Practical introduction to fundamental test equipment,with an invitation to a hands on experience for thosewho are interested.

I Discussion of problems and possible error sources inmicrowave remote sensing instruments.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

3

Example of a 22 GHz Receiver

IAP Radiometer Praktikum

Target

Black BodyCalibration

Atte

nuat

or

Noise Diode

Mixer Filter AmplifierAmplifierCouplerAntenna Detector

+/− 0.5 GHzRF = 22.2

H2OAtmosphere

DCIF =0 to 0.5 GHz

Local Oscillator

LO =22 GHz

Frequency

Pow

er

LO

IF = |RF +/− LO|

LSB

US

B



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

4

Outline

Introduction

Passive Microwave ComponentsTerminationAttenuatorFilterCouplerFerrite Devices

Active ComponentsDetectorMultiplierMixerAmplifierOscillator



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

5

Background Knowledge

I Electromagnetic waves and their complex representation

E = E0ejω(t± x

c )

I Decibel scale for power ratios: 10 · log10 (P1/P2) [dB]

I Transmission lines: waveguides, cables, micro-strip lines⇒ theory later in this lecture

I Impedance, matching and standing waves

4

"

>

"#

:,



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

6

Scattering Parameters

4 % (

%

" % ((

"

4

!

! (

(% (

:,

7 7(

I Relation between incident (a) and reflected ortransmitted waves (b) of a Device Under Test (DUT)b1 = S11 a1 + S12 a2

b2 = S21 a1 + S22 a2

I Matrix notation:

[b1

b2

]=

[S11 S12

S21 S22

] [a1

a2

]I Easily measured with a Vector Network Analyzer

I Expandable to devices with N ports



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

7

Cascaded S-Parameters

aA1 aB2

A1B2

A

NetworkPort 1 Port 2

B

Network

Total Network T

I Cascading two 2-port devices A and B: ST 6= SASB

Multiplying the S-parameter matrices does not work!

I Definition of transmission parameters (T-Matrix)[b1

a1

]=

[T11 T12

T21 T22

] [a2

b2

]I TT = TATB

I Conversion between S and T

T = 1S21

[− det(S) S11

−S22 1

]S = 1

T22

[T12 det(T )1 −T21

]determinat: det(S)

.= S11S22 − S12SS21



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

8

Passive Microwave Components

Definitions

I Linear transfer characteristic– S-parameters do not depend on the power– A continuous wave signal does not get distorted

I Most passive components are reciprocal Sij = Sji

Ferrite isolators and circulators are an exception

I For lossless two-port devices:– Reflections at both ports are identical S11 = S22

– Energy conservation |S11|2 + |S21|2 = 1

Design depends on the frequency range, the requiredperformance and other aspects (e.g. costs, size, mass, powerhandling).



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

9

Lumped Element Devices

I Discrete network of individual components, e.g. coils,capacitors, resistors.

I Dimensions < λ, phase differences from the assemblycan be neglected.

I Usable up to ∼3GHz (and above), but parasitic effectsand radiation losses increase with frequency.

Example for a lumped element 100MHz bandpass filter of aradio amateur receiver.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

10

Distributed Devices

I All components are connected by transmission lineswith dimensions in the order of λ.

I The connections are an integral part of the circuit, e.g.for tuning or impedance matching.

I Usable up to ∼100 GHz (and above).

I Dielectric and ohmic losses increase with frequency, andmanufacturing becomes very demanding.

Example of an integrated 24 GHz receiver module.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

11

Quasi-Optics

I At Millimeter and submillimeter wavelengths free spacepropagation provides lowest losses.

I Quasi-optical components with dimensions > λ are usedto guide, split or combine the beams.

Local Oscillatorto Antenna

Image BBHto Cold Sky

Signal BBH

300

mm

FSP Sideband Filterto Cryostat

Quasi-optical module characterized at IAP for the 660 GHzreceiver SMILES, a Japanese remote sensing instrument forthe International Space Station.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

12

Termination

I Terminates a transmission line (ideally S11= −∞ dB ).

I Tapered absorbing dielectrics in waveguides (a),resistive films in planar or coaxial devices (b).

I Standard coaxial 0-18 GHz terminations specified withreturn loss < -26dB (VSWR<1.1), expensive matchedtermination for VNA calibration have ≥ -36 dB.

I Free space terminations for anechoic chambers orradiometric calibration targets. Often made of lossyfoams with a pyramidal surface to improve thematching.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

13

Attenuator

I Lossy two-port device to reduce the signal level by -xxdB

I Ideally well matched and frequency independent.

I Resistive networks in coaxial (a) and planar devices,absorbing vane in waveguides.

I Often used to reduce standing waves caused bycomponents with a bad matching.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

14

Filter

I Used to reject certain frequency bands

I Realized as low-, high or bandpass filter (and alsoband-reject)

1.32 1.34 1.36 1.38 1.4 1.42 1.44 1.46 1.48 1.5−80

−70

−60

−50

−40

−30

−20

−10

0

10

FWHM

Frequency GHz

Am

plitu

de [d

B]

Bandpass Filter for a L−Band Radiometer

S11S12S21S22

Insertion Loss −0.39 dB

Out−of−bandRejection

CenterFrequency

Measurement example of a cavity filter with four sections.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

15

Cavity Filter Example

7.8 GHz high pass filter made out a series of iris coupledwaveguide resonators. Mesh of the finite element model andsimulation results.

Simulated E-fields in the rejection and transmission band.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

16

Software for Cavity Filter Design at IAP

I Finite Elements: COMSOL Multphysics, Agilent EMDS

I Mode Matching: S&P (written by P. Fuholz)MICIAN ”Microwave Wizard”



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

17

Planar Filter

Steps to get from a lumped element lowpass filter (a) to anequivalent microstrip design (d).

Inductors and capacitors are replaced by microstrip ”stubs”.Easy to integrate in a circuit, but degraded out of bandperformance.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

18

Power Splitter

Used to distribute an input signal at port 1 equally and inphase between the two output ports 2 and 3. An example isa simple waveguide or microstrip T-junction.

It can be shown, however, that it is not possible to match allports of a symmetric, reciprocal and lossless device, i.e. theSii parameters cannot be zero.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

19

Resistive Power Splitter

I A simple resistive power splitter is matched at all portsand has a wide bandwidth, but it has additional -3dBloss and ports 2 and 3 are not isolated.

I The Wilkinson power divider has a limited bandwidth,but it is lossless for S21 and S31, and ports 2 and 3 are

isolated. For an ideal device [S ] = −j√2

0 1 11 0 01 0 0



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

20

Directional Coupler

I 4-port device, input port 1 is isolated from port 4.

I Splits the power coming from port 1 equally or with adifferent coupling ratio between ports 2 and 3.

I Most important characteristics:Directivity, bandwidth, phase and amplitude balance

I Very usefull to measure the return loss of a device.

Reflectometer setup with a directional coupler to measurethe return loss ρL of a device. which corresponds to thepower ration P4/P3.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

21

Hybrid Coupler

I Input power is split equally between port 2 and 3.

I For a matched and lossless device the phase differencehas to be either 90 or 180 degrees.

180 degree ”rat-race” coupler 90 degree ”quadrature” coupler

[S ] = 1√2

0 1 1 01 0 0 −11 0 0 10 −1 1 0

[S ] = 1√2

0 1 j 01 0 0 jj 0 0 10 j 1 0



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

22

Multihole Waveguide Coupler

I Coupling holes connect two parallel waveguides.

I Bandwidth increases with number of holes.

3 4

1 2

Submm devices tested at IAP:micromachined 350 GHz hybridand etched 600 GHz hybrid



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

23

Ferrites

I Ferromagnetic ceramic (Fe2O3+impurities) withhigh resistivity, µr > 1000, εr < 10.

I Can be magnetized permanently by an externalmagnetic field.

I Electromagnetic waves interact with the magneticdipoles.

I Propagation parallel to−→H results

in different effective permeabilityµ+

r and µ−r for left- and right-handed circular polarization, andthus in different propagation con-stants (Faraday rotation):

µ± = µ0

(1 + γµ0MS

ω0±ω

)Larmor frequency ω0 = γB0



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

24

Faraday Isolator

I Non-reciprocal two-port device to reduce standingwaves (ideally S21 = 1 and S12 = 0)

I Resistive vanes at both ports of a circular waveguide areoriented at an angle of 45 to each other and absorbenergy when they are parallel to the E field.

I Ferrite rod in the center rotates the polarization by±45, depending on the propagation direction.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

25

Circulator

I Non-reciprocal three-port device with a ferrite post atthe junction.

I Allows to use the same antenna for transmission andreception (radar, communications).

Circulator example simulated with COMSOL Multiphysics



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

26

Isolator Example

I Measured performance of a high quality 1.4 GHzisolator, which will be used in an L-band radiometer forSMOS validation

I Good performance only over a very narrow bandwidth

I Isolation, loss and matching degrade outside of thespecified frequency band

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3−60

−50

−40

−30

−20

−10

0 −0.07 dB

Frequency GHz

Am

plitu

de [d

B]

Measurement of a 1.4 GHz narrow−band isolator

S11S12S21S22



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

27

Other Ferrite Devices

I Waveguide switch by reversing the magnetic fieldof a circulator.

I Variable phase shifters for electronic beam steering:Fast change of the pointing of a phased-array antennawithout any moving parts

I Absorbers for low frequencies.

I Electrically tunable filters and oscillators



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

28

Common Symbols for Passive Devices



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

29

Active Components

I Nonlinear transfer characteristic leads to signaldistortions and frequency conversion (b), which is notthe case on a linear curve (a).

I Nonlinear devices can still have an almost linearbehavior for small scale signals (c)



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

30

Power Measurements

I Different ways to measure electric power,depending on the frequency range:

DC −→ voltmeter + amperemeterAC to ∼ GHz −→ oscilloscopeAC to ∼ 0.1 THz −→ diode detectorAC to > THz −→ bolometer

I Other selection criteria:I Power range (nW or kW?)I Accuracy (absolute or relative?)I Linearity (required dynamic range?)I Time constant (continuous wave or modulated?)



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

31

Bolometric Detection

I Microwave energy is absorbed and heats the device, thetemperature change ∆T = R · P is measured with athermometer.

Thermometer

Thermal conductance RRadiation

PAbsorber T(P)

Heat sinkT = const

0

I Advantages: good power handling, no fundamentalfrequency limit, possibility for absolute calibration.

I Disadvantages (which can be overcome):relative slow, not very sensitive, thermal drift.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

32

Cryogenic BolometersMost sensitive detectors used in radio astronomy:

I Cooled below 0.5 K

I ”Spiderweb” geometry to minimize mass, heat capacityand thermal conductivity

I Used in many cosmic background experiments

Complete bolometer array and close-up

views of the spiderweb bolometers.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

33

Diode Detector

I Junction betwee semiconductors with different doping(p-n diode) or metal-semiconductor (Schottky diode).

I Non-linear I/V curve rectifies the RF signal.For small signals it can be approximated by a quadraticcurve, and the DC output signal is linear with the inputpower.

n

p_ _ _+ + +

For

war

d di

rect

ion

brea

kdow

n vo

ltage reverse current I

0

V

I reverse bias forward bias

I = I0 [exp(V/V

0)−1]

⟨ I(t)⟩ > 0

V(t)



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

34

Characteristics of Diode Detectors

I Advantages:

I Very fast (rise times < ns), relative sensitive

I Disadvantages:

I Easily destroyed by ESD (electrostatic discharge)I Moderate linearity and temperature stabilityI Upper frequency cut-off given by the parasitic capacity

of the junction

Response of a typical diode de-tector. Only in the square-lawregion the output signal is pro-portional to the input power.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

35

Diode Layout

To use diodes at THz frequen-cies the junction area needsto be as small as possible,which is achieved by point-likewhisker contacts or very smallplanar devices.

F i g . 1 . S c a n n i n g e l e c t r o n m i c r o g r a p h o f a p l a n a r S c h o t t k yb a r r i e r d i o d e . C h i p d i m e n s i o n s a p p r o x i m a t e l y 1 8 0 x 8 0 x 4 0 m .



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

36

Frequency Multiplication

A nonlinear device generates harmonics of an input signalwith the fundamental frequency f0.

Time

V(t

)

Time

|V(t

)|

−40

−30

−20

−10

0

Frequency

Am

plitu

de [d

B] f

0

−40

−30

−20

−10

0

Frequency

Am

plitu

de [d

B] 0

2f0

4f0

6f0 8f

0



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

37

Examples of Frequency Multipliers



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

38

Heterodyne Principle

I Superposition of a strong local oscillator (LO) signalwith a weaker radio frequency (RF ) signal on nonlineardevice generates an intermediate frequencyIF = |LO ± RF |

I Normal double sideband mixers (DSB) convert bothsidebands, single sideband conversion (SSB) requires aRF filter or a special mixer.

LO

MixerRF IF

US

B

IF

LSB

2 LO

RF + LOLO

up−conversiondown−conversion

Pow

er

Frequency

LO−RF

RF−LO



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

39

Mixers Designs

I Single ended mixer (a): Common for mm wavelengths.No isolation between RF and LO.

I Balanced mixer (b): Two mixing elements, 3dB hybridcombines LO and RF. Good LO to RF isolation, LOnoise and spurious harmonics are rejected.

I Double balanced mixer (c): Also IF port is isolated,dynamic range is improved.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

40

Subharmonic Mixer

I Antiparallel diode pair down-converts with the secondLO harmonic IF = |RF − 2LO|

I Advantages:Lower LO frequency and good LO/RF isolation.

I Disadvantages:Higher conversion loss and LO power requirement.

RF

LO

IF

RF filter

diode pair

IF Filter



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

41

SIS Mixer

Superconductor-Isolator-Superconductor tunnel junction:

I Two Niobium layers at 4K (ρΩ = 0),separated a 2 nm thick Al2O3 barrier

I Cooper-pairs (2e−) tunnel through the barrier,resulting in a sharp bend in the I/V curve

0 2 4 60

100

200

300

400

bia

s c

urr

ent I 0

[µA

]

bias voltage U0 [mV]

V0

superconductor

insulator

superconductor

I0

a) b)

V0



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

42

SIS Mixer

Band structure and photoassisted tunneling in a SIS junction.

superconductor"bandgap"

SS

I

energy

2ephoton

unfilled energy states

filled energy states



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

43

SIS Mixer Characteristics

I Very low noise, close to the quantum limit hν/kB

I Upper frequency limit from the bandgap voltageNiobium: 1.4 THz

65 µm

NbTiN

ground

plane

SiO2

dielectric

Nb top-wiring

(1)

(2)

(3)

48 µm

junction

1µm2

feed point

Example of an SIS mixer forthe HIFI instrument. Thejunction has an area of only1µm2, most parts in the im-age are tuning elements forthe impedance matching.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

44

HEB MixerI Hot Electron Bolometers (HEB) are extremely fast

bolometers, which can be used as mixing element.I Superconducting microbridge (d <10 nm) close to the

transition temperature.I No fundamental RF frequency limit (>2THz)I Limited IF bandwidth (∼ 5 GHz) given by cooling rate

of the electrons.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

45

Amplifier

I Increase signal amplitude

I Made with bipolar or FETtransistors

I Tradeoff between low noiseand high power

bias out

in

CB

E

n AlGaAs

undoped GaAs

n+

HEMT−FET transistorbipolar transistor

source gate drainbaseemitter

collectorGaAs

n p

quantum−well with 2DEG

Schematic of a bipolar npn transistor and a High ElectronMobility (HEMT) field effect transistor, which works with a2D electron gas in a quantum well.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

46

Amplifier Specifications

I Gain (amplification in dB)

I Frequency range and gain flatness

I Noise figure (how much noise is added)

I Maximum output power and 1dB compression point

Examples:

Power amplifierG=45dB (±2dB), NF=8dBf=0.8-2 GHz, 1dB Gc = +36dBmVSWR = 1.7dB Bias supply 24V, 2A

Lownoise amplifierG=15dB (±1dB), NF=0.4dBf=1-1.4 GHz, 1dB Gc = +12.5dBmVSWR = 1.7dBBias supply 12V, 40mA



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

47

Oscillator

Active element (1) with a resonant feedback (2)

(1) Transistor, electrons in a vacuum tube (for high power),Gunn diode (semiconductor with negative resistance), ...

(2) LC-circuit, microstrip and dielectric resonator,waveguide cavity, quartz crystal, ...

L C

Schematic of a LC oscillator with ω0 = 1√LC

and

example of a dielectric oscillator in stripline technology.



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

48

Magnetron

I Microwave generator for high output power (>1MW)with good efficiency (>80%)

I A high electric field accelerates electrons in a circularcavity, a magnetic field forces them on a spiral pathwhich excites microwave resonances.

I Standard for microwave ovens and radar systems



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

49

Oscillator Specifications

I Frequency accuracy and stability

I Phase noise (specified in dB below carrier [dBc])

I Harmonic and spurious signals

I Phase noise and short term accuracy depends on thequality of the resonator (Q-factor).

Phase Noise

Residual FM

Spurious

non-harmonic spur

~65dBc

harmonic spur

~30dBc

CW output

Residual FM is the integrated

phase noise over 300 Hz - 3

kHz BW phase

noise

0.5 f0 f0 2f0

sub-harmonics



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

50

Oscillator Types

I Atomic clocks (Cs or Rb) for absolute time standardswith ∆f /f < 10−15 (e.g. at METAS, UniNE, NIST)

I Quartz oscillators as reference signals up to 100 MHzreach ∆f /f = 10−6 to 10−9, depending on temperaturecompensation or temperature stabilization.

I All higher frequencies are usually synchronized to aquartz crystal with a phase-locked loop (PLL).

free running phase lockedExample of a 6 GHz cavity oscillator



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

51

Modulation Analog

I Amplitude modulation (AM): VAM = A(t) sin(f0 · t)Volta

ge

Time

Carrier

Modulation

I Frequency modulation (FM): VFM = A0 sin(f (t) · t)Phase Modulation (PM): VPM = A0 sin(f0 · t + φ(t))

Volta

ge

Time



Introduction

Passive

Termination

Attenuator

Filter

Coupler

Ferrites

Active

Detector

Multiplier

Mixer

Amplifier

Oscillator

52

Modulation Digital

Amplitude

Frequency

Phase

Quadrature phase-shift keying (QPSK):Digital ModulationPolar Display: Magnitude & Phase Represented Together

Magnitude is an absolute value

Phase is relative to a reference signal

Phase

Mag

0 deg

QPSK IQ Diagram

I

Q

0001

1011

Introduction Passive and Active Microwave … Physics and Quasioptics: Passive and Active...

Documents

Transcript of Introduction Passive and Active Microwave … Physics and Quasioptics: Passive and Active...