Historical Overview of basic RF Concepts
High Performance Integrated Circuits Design Group
http://pmos.upc.es/blues/
RF Communications System-on-Chip
International Master Course 2006-2007
E.T.S.E.T.B. – D.E.E. Electronics Engineering Master Course 2006-2007
Departament d’Enginyeria Electrònica
Universitat Politècnica de Catalunya
Historical Overview of Basic RF Concepts
Contents:
1.
Transmitters
2.
Wave detectors (receivers)
3.
Who invented the radio?
4.
Valves, audions
5.
Heterodyne receivers
6.
Other coherent receivers
7.
The invention of the semiconductor transistor
8.
The Integrated Circuit
Bibliography:
1.
“The Design of CMOS Radio-Frequency Integrated Circuits”, Thomas. H. Lee.
2.
“The Design and Implementation of Low-Power CMOS Radio Receivers”, Derek K.
Shaeffer, Thomas H. Lee
3.
“Famous Electrochemists” web page, maintained by Eugenii Katz (now removed from
online access) http://chem.ch.huji.ac.il/~eugeniik/history/electrochemists.htm
4.
Wikipedia, the free encyclopedia: http://en.wikipedia.org
Historical Overview of Basic RF Concepts
1
RADIOWHAT ????
• ∼1890: Radiotelegraphy – coded information (wave - no wave : digital
transmission)
• ∼1906: Radio communication – audio transmission (analog modulation of a
carrier wave)
• ∼1959: First Integrated circuit – beginning of the microelectronics era
• ∼1990: RF-IC: Advanced modulation techniques – improvement of silicon
technology
Historical Overview of Basic RF Concepts
TRANSMITTER
• Typical transmitter in RF-IC:
0
Tx
Up
Conversion
Band
Filter
Power
Amplifier
Mixer
Modulator
?
ω
0
Information encoded
and modulated in a
waveform
Amplification
Single tone, occupies
an specific part of the
spectrum
Historical Overview of Basic RF Concepts
2
Spark transmitter:
• Hertz “invented” the first transmitter (emitter) when
trying to demonstrate Maxwell’s theory about the
existence of electromagnetic waves.
Hertz,
~1888
• A capacitor is charged to a high voltage by an induction
coil.
• When the potential across it is sufficiently high to break
down the insulation of air in the gap, a spark occurs.
Symplified scheme
• Emitted wave rich in harmonics (broadband).
• Since the spark has a low resistance (an ohm or two), the spark
discharge is equivalent to the closing of an L-C-R circuit. The condenser
then discharges through the conducting spark, and the discharge takes
the form of a damped oscillation, at a frequency determined by the
resonant frequency of the spark transmitter.
Historical Overview of Basic RF Concepts
Spark transmitter:
Hertz,
frequency transmitted was determined by the self resonant frequency ~1888
• Antenna: an end-loaded dipole was first used (the
of the antenna system: hundreds of MHz, due to antenna size)
• Sphere capacitors were used
C=
Q
= 4πε o ⋅ radi
V
• Another spark gap was used as receiver (detector)
(reception was indicated by a visible spark: only useful in small
ranges – otherwise huge powers would be needed and sparks would
rise everywhere, a public health problem….)
Scheme of the first spark transmitter
Historical Overview of Basic RF Concepts
3
Spark transmitter:
• Hertz did not imagine his invention useful: “It's of no
use whatsoever"
Hertz,
~1888
www.sparkmuseum.com
Historical Overview of Basic RF Concepts
Sine-wave transmitter:
• The problem with the spark transmitter is that the
signal generated was broadband. No two
simultaneous communications were possible
because of interference.
Poulsen,
1903
• In 1899, Marconi provided coverage of the America’s Cup yacht
race. It was a big success. In 1901, he tried to repeat the
experience. Two other groups were encouraged to transmit
information too. No information was received because of
interference.
• Poulsen made the first sine-wave transmitter, with
a resonant L-C circuit. (continuous wave, single tone)
• A Morse key was used to short 1 or 2 turns of the
inductor, shifting the frequency and pulling the
transmitter in and out of tune with the receiver
(digital FM !).
ωo =
1
LC
Poulsen arc transmitter
Historical Overview of Basic RF Concepts
4
Sine-wave transmitter:
• Any LC resonant tank that is used a sine-wave
(carrier) generator needs a negative resistance to
compensate losses.
• Poulsen’s
arc transmitter used glowing DC arc as
negative resistance to maintain oscillation.
• Still the oscillation was not maintained indefinitely,
but was stable enough for radiotelegraphy.
NMOS resonant VCO
• Fessenden in 1906 achieved the first audio radio
transmission. His main problem was to generate a
continuous carrier. This first voice transmission in
1900 used a spark transmitter; a mechanical device
switched it 10.000 times per second.
Poulsen arc transmitter
Historical Overview of Basic RF Concepts
Transmitter power:
• These transmitters had no amplifiers (were not
“discovered” until ∼1910). How to transmit to larger
distances??
• Huge powers (up to 1 MW !!) and huge antennas
(up to 150 m !!) were needed to transmit at large
distances.
• Around 1900, Marconi noticed the importance to
ground one of the terminals of a monopole antenna.
• This allowed him the first transatlantic
communication in December 12th, 1901.
Antenna used for the first
AM transmission
Historical Overview of Basic RF Concepts
5
RECEIVER
• Coherent detection: incoming signal is demodulated by multiplying with a
tone which frequency matches that of the transmitted carrier (heterodyne
receivers)
• Easy AM uncoherent detection: rectify & filter
Received waveform
Rectification and filtering
DC blocking
Images from “Communication Systems”, A. Bruce Carlson, McGraw-Hill
Historical Overview of Basic RF Concepts
Coherer detector:
• Edouard Branly developed an EM wave detector
(although he never used it to receive wireless signal transmission) :
Branly,
1892
a tube filled with metal particles.
• The large resistance between terminals drops several orders of
magnitude when an electromagnetic wave reaches it (the
electromagnetic wave sticks (or cohers) together the particles
inside the tube).
• Sir Oliver Lodge, in 1894, demonstrated a receiver
circuit based on a coherer, that detected electromagnetic waves. It was the first wireless transmission, but no
Lodge,
1894
intention to transmit messages was present, just signaling.
• Lodge coined the term “coherer”. He
improved it by automatically shaking
the tube after each reception.
• Lodge later proposed to use matched antennas
for tuning the communication.
Branly’s coherer
Historical Overview of Basic RF Concepts
6
Crystal detector:
• The first crystal detector consisted of a small wire
(catwhisker) that point-contacted a crystal surface. The
device behaved like a diode (despite randomness in the
Bose,
1901
position of the contact, pressure, etc).
• Several materials were tried (even silicon in 1907!),
but galena (lead sulfite) was the most widely used.
• A resonant LC circuit tuned the transmitted frequency
(carrier), the crystal rectified it, and earphones were
used to listen to the demodulated signal.
Early cristal detector
Historical Overview of Basic RF Concepts
Crystal detector:
• Still no amplifiers: it is expected that a sufficiently
strong audio frequency component is received.
Pickard,
1904
antenna
• Main advantages of the crystal detector are its
simplicity and no need of battery.
• Disadvantages are its poor sensitivity (signal must be
headset
strong enough to forward-bias the diode without previous
amplification). Also earphone must have high
impedance. Last, the LC filter provides poor
selectivity.
• The detector was later used as the simplest AM
receiver. Variable C was used to tune the desired
radio channel.
Historical Overview of Basic RF Concepts
7
BUT… WHO INVENTED THE RADIO ?
Popov,
1895
Branly,
1892
Lodge,
1894
Hertz,
~1888
Marconi,
1895
Bose,
1901
Fessenden,
1906
Historical Overview of Basic RF Concepts
First radio communication:
• Popov demonstrated in 1895 an equipment
(antenna, coherer) which detected the radiation
originated by lightning (he also wrote that could be used for
Popov,
1895
communicating messages)
• In 1896 he used his equipment to communicate
Morse signal between buildings. In subsequent years he
improved his radio communication system.
• Marconi made his first wireless transmission in
1895. From the beginning, he had clear idea of
using his system for messaging, and had clear idea
of its commercial use.
Marconi,
1895
• Marconi’s first experiment’s were exactly like Popov’s. But
Marconi made headlines, told the press, patented his inventions
(1897) and created his own communications company (in 1897,
which eventually has continuity up to today’s Marconi plc).
Although Popov and Lodge demonstrated the same physical
experiments, they always were behind Marconi’s application view.
Popov’s first radio
Historical Overview of Basic RF Concepts
8
Better receivers:
Marconi,
1901
• The basic coherer detector was usually
triggered by random electromagnetic
events (not signals). Moreover it had no
tuning capability (not much of a problem with
spark transmitters…).
• Marconi patented (Patent #7777, 1890) a
transmitting and receiving system that
used filtering and matched antenna
lengths to somehow tune the
communication.
• He achieved the first transatlantic
communication and commercialized his
system. In 1909 his radio system saved 1700 lives
when two ferries collided and one of threm sanked off
US coast
• He received the Nobel Prize in 1909
Marconi’s transmitter and receiver
Historical Overview of Basic RF Concepts
First voice transmission via radio:
Fessenden,
• Reginald A. Fessenden was the first to experience
1906
transmission of voice instead of Morse (dots and
dashes) code. (radiotelephony vs. radiotelegraphy)
• He achieved the first voice transmission in 1900.
• He used a carbon microphone in series with the
antenna to modulate a carrier (If the waves can be sent at
a high frequency, it is be possible to hear only the “variations due to
the human voice”).
•The carrier was generated with a spark transmitter,
switched 10.000 times per second.
• In Christmas Eve 1906, he used a high-power
alternator to generate a carrier and broadcast the
first AM emission. (Radiotelegraphists in ships were warned to
listen, and they heard a human voice, together with Christmas
carols and Haendel music).
Historical Overview of Basic RF Concepts
9
BETTER DEVICES:
VALVES (vacuum tubes)
Historical Overview of Basic RF Concepts
Vacuum tube or valve:
• John A. Fleming invented the two-terminal
vacuum tube, with rectifying properties.
Fleming,
1904
• It consisted of a bulb with a filament and a
plate, each connected to different
terminals.
• Current flowed in one direction (the
filament emits electrons when hot, which
are collected by the plate), but not in the
opposite direction.
• This effect had already been observed by the inventor
of the bulb, T.A. Edison, but gave it no importance.
• This Fleming valve was used to detect
radio signal, but it was little sensitive and
consumed much power.
Fleming
valve
Historical Overview of Basic RF Concepts
10
Vacuum tube or valve:
• Lee de Forest had the occurrence to add
a grid between the filament and the plate.
De Forest,
1906
• He called his invention “audion” (later
known as triode), and patented it as
detector. He (and others) did not discover
its amplifying properties until some years
later.
• The grid current controls the filament to
plate current (similar to base terminal in a
transistor), thus providing signal
amplification.
De Forest audion
• This was the first ever amplifying device,
and opened the door to receivers with
improved sensitivity.
Historical Overview of Basic RF Concepts
Audion amplifier:
• Edwin H. Armstrong in 1914 was the first
to correctly explain the audion’s behavior,
and filed the simplest amplifying detector
in 1914.
Armstrong,
1914
• It used a galena crystal as detector, and
the audion as amplifier.
• Signals from overseas could be easily
detected.
Historical Overview of Basic RF Concepts
11
HETERODYNE RECEPTION
• Typical receiver in RF-IC:
0
Rx
Down
Conversion
Band
Filter
Demodulator
Low Noise
Amplifier
Mixer
?0
ω
• Assumes narrowband emission
• Allows multiple transmissions
• Inherent tuning through ω0
Historical Overview of Basic RF Concepts
Heterodyne receiver:
Fessenden,
1902
• Fessenden patented in 1902 the heterodyne
receiver (to heterodyne=to mix different signals).
• The local oscillator was introduced for the first time.
It allowed tuning to the received carrier.
• Sensitivity was also increased: the oscillator signal
was strong enough to switch the diode on (despite
weak incoming signals).
• A significant problem (in later years) was that the
oscillator tone was also radiated to the antenna. In
subsequent receivers, isolation between the
oscillator and the antenna became critical.
• The heterodyne receiver used frequency
conversion for the first time (although this concept was still
unrecognized by the inventors).
Historical Overview of Basic RF Concepts
12
Heterodyne receiver:
• Received signal and
local oscillator signal
were just added.
Ex: 1 MHz
antenna
Ex: 1,001 MHz
L.O.
headset
Envelope: 1 KHz
• The local oscillator was
tuned to get a
comfortable beat audio
frequency
(www.tpub.com)
1 KHz
Historical Overview of Basic RF Concepts
Superheterodyne receiver:
Armstrong,
1918
• Audions gave little amplification above 1 MHz,
thus they could not be used to receive signals
above that limit.
• Following Fessenden’s heterodyne concept,
he proposed a two-stage receiver. The input RF
signal was translated to a intermediate
frequency (IF), which could be easily amplified
and demodulated.
• The amplifier and detector work at a fixed IF
frequency, while the only tuning happens at the
LO. This allows using the same receiver for
many RF signals.
• This superheterodyne receiver was the first
mass-produced AM radio by RCA, and is still
the basic receiver architecture used today.
Scheme of early superheterodyne receiver
Historical Overview of Basic RF Concepts
13
Homodyne receiver:
Colebrook,
1924
•The homodyne receiver can be understood as
a superheterodyne where the LO frequency
equals the RF input, thus providing a zero-IF De Bellescize
and no need of detection (demodulator).
1930
• Colebrook first observed this effect, by using a regenerative
receiver in which output was overcoupled to the input, thus an
oscillation was produced. When oscillation frequency
matched the input frequency, no detection was needed.
•Synchronization between input and oscillation
was critical. De Bellescize introduced a circuit
that guaranteed synchronization by detecting
the difference frequency and correcting the LO
according to its value. This is the principle of
the phase-locked loop, and De Bellescize is
considered the inventor of the PLL.
Historical Overview of Basic RF Concepts
AM RECEPTION: NOT A SINGLE SOLUTION
Historical Overview of Basic RF Concepts
14
Regenerative receiver:
•The regenerative receiver used a single
audion to detect and amplify.
Armstrong,
1915
•The grid-filament set act like a Fleming
valve detector.
•The plate delivers an amplified replica of
the rectified grid signal.
•The amplified signal was coupled to the
input with a RF transformer, to provide
positive feedback and thus further amplify
the input signal.
Historical Overview of Basic RF Concepts
Regenerative receiver:
•Armstrong introduced series inductances
(input, plate) that acted as impedance
matching networks (thus increasing the
available signal).
Armstrong,
1915
•The use of matching inductances and
selective feedback provided high Q, thus
narrow bandwidth and high selectivity.
•A number of innovative versions of the
circuit were later made, like a differential
one for noise rejection.
•Also, by increasing the coupling between
the output and input, the circuit becomes
an oscillator.
Historical Overview of Basic RF Concepts
15
Superregenerative receiver:
• Amplifier that can achieve gains as high as
100.000 with the minimum number of
components (still used today in cheap circuits)
Armstrong,
1922
• It is based on an unstable regenerative
amplifier. The circuit is initialized periodically,
thus it never saturates. After a given period of
time, the amplitude will be proportional to the
initial condition (the input signal).
• The resulting output is thus a series of
oscillation bursts whose amplitude is the input’s
amplitude amplified. This can be detected by a
simple AM amplifier.
• Note the circuit amplifies samples of the input,
with a frequency higher than the signal
bandwidth and lower than the RF carrier.
Historical Overview of Basic RF Concepts
FREQUENCY MODULATION
• Amplitude modulation (AM) had the problem
of being very sensitive to noise and interference
(particularly by meteorological phenomena). In
AM, the information is contained in the
amplitude, while the carrier frequency is
constant.
Armstrong,
1933
• He decided that the only solution to this
problem was to place information in variations
of the carrier frequency (frequency modulation,
FM), while keeping the amplitude constant.
First FM modulator
Historical Overview of Basic RF Concepts
16
GOOD BYE VALVES, WELCOME
SEMICONDUCTORS
A BJT mixer
A practical amplifier circuit
Historical Overview of Basic RF Concepts
First PN junction diode:
• World War II pushed the need of high-frequency
amplifiers for radar applications. Vacuum tubes could
not achieve high frequency
Ohl
1940
• In 1939, Russell Ohl, a (forgotten) researcher at Bell
Labs, tried with the (also forgotten, at that time)
catwhisker detector invented by Bose in 1901.
• After experimenting with different materials, he
(accidentally) came up to discover a semiconductor
diode (PN junction).
• Germanium diodes were immediately put into
production.
• Oleg Losev had (independently, and also forgotten)
developed solid state amplifiers working at 5 MHz
already in 1922.
Historical Overview of Basic RF Concepts
17
First semiconductor transistor:
• After the War, Shockley, Bardeen and Brattain
pursued the fabrication of a semiconductor triode.
• This was obtained in 1947, by cutting the tip of a
plastic triangle covered with a gold plate (thus two
close-by contacts were created), which contacted
a semiconductor (point-contact transistor)
Shockley,
Bardeen,
Brattain
1947
First transistor (Bell-Labs, 1947)
Historical Overview of Basic RF Concepts
First BJT transistor:
• In 1950, Shockley created the first real bipolar
junction transistor, or BJT.
Shockley,
1950
• Shockley, Bardeen and Brattain shared the
Nobel prize in 1956
• Other researchers had previous theoretical
descriptions of semiconductor transistors
(Lilienfeld, 1928; Heil, 1934), but there is no
evidence of their implementation before 1947.
• Also an European group developed the a
semiconductor transistor almost simultaneously
(Mataré, Welker, 1948)
Historical Overview of Basic RF Concepts
18
THE FINAL STEP….
Historical Overview of Basic RF Concepts
First Integrated Circuit:
• The first integrated circuits were
manufactured independently by two
scientists: Jack Kilby of Texas Instruments
(he developed an oscillator), and Robert Noyce
from Fairchild Semiconductor (later Intel)
Kilby,
Noyce
1959
• Although Noyce’s invention was about 6
months later, a large patent dispute
between the two companies started.
• Jack Kilby was awarded the Nobel Prize
in 2000.
First planar IC, 1961
First Integrated Circuit
(Texas Instruments, 1958)
Historical Overview of Basic RF Concepts
19
Moore’s Law:
Source: Intel
The number of
components in an IC
doubles every 18
months
Historical Overview of Basic RF Concepts
Historical Overview of Basic RF Concepts
20
Source: Intel
The number of
components
in an IC
15 nm
doubles every 18
10 nm
months
Historical Overview of Basic RF Concepts
System-on-a-Chip (SoC):
0,35 µm CMOS
H. Darabi, et al, “A
2.4 GHz CMOS
Transceiver for
Bluetooth”, IEEE
ISSC 2001.
Transilica
0,25 µm
CMOS
(RF IC)
0,25 µm CMOS
Frank Op’t
Eynde, et al., “A
Fully-Integrated
Single-Chip SoC
for Bluetooth”,
IEEE ISSC 2001
Historical Overview of Basic RF Concepts
21
System-on-a-Chip (SoC):
1.8 mm
• SoC GPSs
fo=1,57 GHz
Sensitivity -130 dBm (19 dB below thermal noise)
Historical Overview of Basic RF Concepts
ASSIGNMENTS FOR NEXT WEEK:
• Download SysCalc from http://petrus.upc.es/rfcs/Material/SysCalc4.rar and
install it in your personal computer. Navigate the menus and discover its
functionalities. Complete the tutorial.
• Download AppCAD from http://www.hp.woodshot.com/ and install it in your
personal computer. Navigate the menus and run the different utilities to
discover its functionalities
• (Can be done in pairs): Search for some wireless communication standard
and write in a table the main (for you) standard specs.
Historical Overview of Basic RF Concepts
22