modern radio techniques for probing the ionosphere...
TRANSCRIPT
Mod
ern
radi
o te
chni
ques
for
prob
ing
the
iono
sphe
re
Cesi
dio
Bian
chi I
NGV
- R
oma
Ital
y
Rece
iver
, rad
ar, a
dvan
ced
iono
sphe
ric
soun
der,
and
rel
ated
tech
niqu
es
Iono
sphe
ric
prop
erti
es r
elat
ed t
o ra
dio
wave
sTh
e m
ost
usef
ul
way
to p
erfo
rm s
yste
mat
ic m
easu
rem
ents
inth
e io
nosp
here
is
to
use
radi
o wa
ves.
Thi
s ca
n be
don
eex
ploi
ting
the
pro
pert
ies
of t
he i
onos
pher
e wh
en it
int
erac
tsin
var
ious
way
s w
ith
the
elec
trom
agne
tic
wave
s.
The
radi
o te
chni
ques
for
pro
bing
the
iono
sphe
re a
re s
prea
d in
near
ly a
ll ra
nges
of
radi
o fr
eque
ncy.
We
expl
ore
the
str
uctu
re
of
the
iono
sphe
re
by
boun
cing
radi
o wa
ves
of d
iffe
rent
fre
quen
cies
on
it, a
nd u
sing
spe
cial
rece
iver
s to
det
ect
how
the
ref
lect
ed w
aves
hav
e c
hang
edfr
om t
he t
rans
mit
ted
wa
ves.
We
als
o ex
amin
e t
he
chan
ges
of
the
rad
io w
aves
fr
omsa
telli
tes
tran
smit
ted
thro
ugh
the
iono
sphe
re e
tc..
Tech
niqu
es
- ve
rtic
al s
ound
ings
+ D
oppl
er s
hift
mea
sure
men
t
- in
cohe
rent
sca
tter
rad
ar
- TE
C m
easu
rem
ent
•Th
e ra
dio
is a
dev
ice
that
eit
her
gene
rate
s, o
rre
spon
ds t
o r
adio
wav
es.
•Th
e ra
dar
(rad
io d
etec
tor
and
rang
ing)
is
a de
vice
able
to
tran
smit
a p
ulse
d ra
dio
wave
and
rec
eive
its
echo
eva
luat
ing
also
the
ran
ge a
nd t
he m
odif
icat
ion
of t
he t
rans
mit
ted
rad
io w
ave.
Radi
o &
Rada
r p
rinc
iple
s
Basi
c re
quir
emen
ts f
or r
ecei
vers
:
- R
ecei
ving
, am
plif
ying
and
dem
odul
atin
g
AM
, FM
, ph
ase
code
d wa
ves,
etc
.
–ab
ility
to
tune
to
a sp
ecif
ic s
igna
l
–am
plif
y th
e si
gnal
tha
t is
pic
ked
up
Radi
o Re
ceiv
er
Supe
rher
odyn
e re
ceiv
er
sect
ions
func
tion
s &
requ
irem
ents
-m
odul
atio
n (am
plit
ude,
fre
quen
cy, p
hase
etc
..) (i
nfor
mat
ion)
-fi
lter
(s
elec
tivi
ty)
-am
plif
ier
(dyn
amic
, sen
siti
vity
and
line
arit
y)
-de
tect
ion
(dyn
amic
and
line
arit
y)
- co
ntro
l (dy
nam
ic a
nd li
near
ity,
AGC
, sel
ecti
vity
)
ante
nna
A r
adio
ant
enna
may
be
defi
ned
as a
str
uctu
reas
soci
ated
wit
h th
e re
gion
of
tran
siti
on b
etwe
ena
guid
ed w
ave
and
free
spa
ce o
r vi
ce v
ersa
(Kra
us)
RF f
ront
-end
Inte
rmed
iate
fre
quen
cy
Mix
er-
By
a lo
cal o
scill
ator
LO
, the
RF
is c
onve
rted
to
IF (R
F to
IF
tran
slat
ion)
. Sha
pe o
f th
e en
velo
pe r
emai
n th
e sa
me.
BW
is u
ncha
nged
–IF
is c
hose
n al
ways
lowe
r th
an R
F:m
ore
stab
le (d
o no
t os
cilla
te).
Usu
ally
one
RF a
mpl
ifie
r, I
F st
ages
>2
Det
ecti
on p
roce
ss
Det
ecti
on
Two
type
s•
Cohe
rent
(syn
chro
nous
): fr
eque
ncie
sus
ed f
or d
emod
ulat
ion
are
exac
t co
pyof
Tx
carr
ier
•N
on-c
oher
ent
(asy
nchr
onou
s):
enve
lope
det
ecti
on
Inte
rnal
noi
se
The
whit
e n
oise
is d
ue t
o th
e ra
ndom
mot
ion
of t
heel
ectr
ons.
The
vol
tage
acr
oss
the
two
resi
stor
ter
min
alat
the
abs
olut
e te
mpe
ratu
re T
is:
Vrm
s=2(
KTRB
)0.5
whe
re K
is t
he B
oltz
man
n co
nsta
nt (J
/Hz)
and
B is
the
ban
d of
fre
quen
cy c
onsi
dere
d.U
nder
wel
l mat
ched
con
diti
on t
he p
ower
is P
=KTB
(W)
By d
efin
itio
n th
e no
ise
fact
or F
is:
Sign
al-t
o-no
ise
rati
o(in
put)
/ S
igna
l-to-
nois
e ra
tio
(out
put)
Inte
rnal
noi
se 2
In t
he r
ecei
ver
it is
use
ful t
o de
fine
the
noi
se f
acto
rF
in q
uant
itat
ive
way
as:
wher
e P i
and
PA a
re t
he in
put
nois
e a
nd a
ddit
iona
lno
ise
mea
sure
d at
am
plif
ier
the
outp
utTh
e no
ise
figu
re is
f noi
se =
10
log 1
0 F
)o
/(/
APB
GKT
GPi
KToB
PiF
+=
envi
ronm
ent
nois
e &
inte
rfer
ence
s
•W
hat
is im
port
ant
at t
he a
nten
na le
vel i
s th
e si
gnal
-to
-noi
se r
atio
(S/N
)•
The
nois
e le
vel d
oes
not
allo
w to
incr
ease
the
sens
itiv
ity
as w
e de
sire
.
•Te
rres
tria
l env
iron
men
t is
con
tinu
ousl
y ex
pose
d to
elec
trom
agne
tic
radi
atio
ns, w
hich
set
up
a“b
ackg
roun
d ” o
f el
ectr
omag
neti
c no
ise.
The
elec
trom
agne
tic
back
grou
nd r
efer
s to
the
envi
ronm
ent
in w
hich
the
re a
re b
oth
natu
ral a
ndm
anm
ade
elec
trom
agne
tic
nois
e.
•Br
oadc
asti
ng s
tati
ons
can
caus
e st
rong
inte
rfer
ence
s wh
ich
affe
ct t
he r
ecep
tion
of
the
sign
al
Rada
r
TX
R XRe
ceiver
CCo
ntro
ller
Display
unit
T/R
switch
or
circ
ulat
or
Mon
o st
atic
rad
ar
Bi-s
tati
c ra
dar
Freq
uenc
y sy
nthe
size
r
DD
S
Rad
ar e
quat
ion
The
rada
r eq
uati
on r
epre
sent
s th
e ph
ysic
al d
epen
denc
es o
fbe
twee
n th
e tr
ansm
itte
d p
ower
and
rec
eive
d po
wer.
432 )
4()
(rP
GP
rad
dr
πσ
λ=
Rad
ar e
q
Var
iabl
eD
efin
ition
Uni
ts
P rPo
wer
rece
ived
by
the
rada
ran
tenn
aw
atts
(W)
λW
avel
engt
h of
sign
al re
ceiv
ed b
y ra
dar a
nten
nam
eter
s (m
)
Gd
Dire
ctiv
e ga
in o
f ant
enna
(mea
sure
of t
heco
ncen
tratio
n of
the
radi
ated
pow
er in
a p
artic
ular
dire
ctio
n)
unitl
ess
σRa
dar
cros
s se
ctio
n (c
hara
cter
izes
the
targ
et’s
abi
lity
to s
catt
er o
r re
flec
t en
ergy
)sq
uare
met
ers
(m2 )
P rad
Powe
r di
ssip
ated
thr
ough
the
cha
ract
eris
tic
impe
danc
e, R
rad,
of
the
TX r
adar
ant
enna
wat
ts (W
)
rD
ista
nce
mea
sure
d fr
om t
he r
adar
to
the
targ
etm
eter
s (m
)
43
2 )4(
)(
rPG
Prad
dr
πσ
λ=
Rada
r cr
oss
sect
ion
•Ra
dar
cros
s se
ctio
n is
def
ined
as:
2
24
=is
EEr
πσ
wher
e E s
and
Ei
are
defi
ned
as t
he s
catt
ered
and
inc
iden
tel
ectr
ic f
ield
s, r
espe
ctiv
ely.
Es
is m
easu
red
at t
he r
ecei
ving
ante
nna,
whe
reas
Ei i
s m
easu
red
at t
he t
arge
t le
vel
. Si
nce
the
scat
tere
d el
ectr
ic
fiel
d is
in
vers
ely
prop
orti
onal
to
dist
ance
, r, t
he r
adar
cro
ss s
ecti
on r
educ
es t
o th
e fo
llowi
ng:
2
2
24
4
=
≡is
is
EEErE
rπ
πσ
iono
sond
es 1
Enve
lope
det
ecto
r io
noso
nde
or H
F Ra
dar
iono
sond
e bl
ock-
diag
ram
Del
ay
- Th
e fr
eque
ncy
mea
sure
men
t is
ass
ured
by
the
rece
iver
sel
ecti
vity
alw
ays
tune
d wi
th t
hetr
ansm
itte
d fr
eque
ncy
In p
ract
ical
is t
he s
ame
freq
uenc
y sy
nthe
size
rth
at s
teer
s bo
th t
rans
mit
ter
and
rece
iver
2
•Ve
rtic
al s
ound
ing
are
perf
orm
ed b
y a
high
freq
uenc
y ra
dar
know
n as
io
noso
nde.
Th
eio
noso
nde
send
s sh
ort
puls
es o
f ra
dio
ener
gyve
rtic
ally
into
the
iono
sphe
re. T
hese
pul
ses
are
refl
ecte
d ba
ck t
owar
ds t
he g
roun
d an
d th
eio
noso
nde
reco
rds
the
tim
e de
lay
betw
een
tran
smis
sion
an
d re
cept
ion
of
puls
es.
Byva
ryin
g th
e ca
rrie
r fr
eque
ncy
of p
ulse
s fr
om 1
to
20
MH
z,
the
tim
e de
lay
at
diff
eren
tfr
eque
ncie
s is
rec
orde
d.
Vert
ical
sou
ndin
g
Mag
neto
plas
ma
sepa
rate
the
wav
e in
to t
woco
mpo
nent
s
fp, ν
and
fB
- th
e pl
asm
a fr
eque
ncy
fp is
:
02
21
επmNe
f p=
-The
fre
quen
cy o
f co
llisi
on b
etwe
en e
lect
rons
and
neu
tral
mol
ecul
es ( ν
)
is:
ν=1
/ τ b
eing
τ is
the
ave
rage
tim
e be
twee
n c
ollis
ions
-fre
quen
cy o
f cy
clot
ron
( fB)
f B =
e B
/ m
2π
esta
blis
hes
the
cond
itio
n of
pro
paga
tion
of
the
wave
thro
ugh
the
mag
neti
sed
iono
sphe
ric
plas
ma.
Iono
sphe
ric
plas
ma
iono
gram
Iono
gram
’s ch
arac
teri
stic
s
Bott
om p
rofi
le (p
ost-
proc
ess)
Puls
e co
mpr
esse
d io
noso
ndes
C
hirp
: typ
ical
pha
se c
odin
g or
mod
ulat
ion
appl
ied
to t
hera
nge
puls
e of
a r
adar
des
igne
d to
ach
ieve
a la
rge
ti
me-
band
widt
h pr
oduc
t. T
he r
esul
ting
pha
se is
qua
drat
ic in
tim
e, w
hich
has
a li
near
der
ivat
ive.
Suc
h co
ding
is o
ften
calle
d lin
ear
freq
uenc
y m
odul
atio
n, o
r lin
ear
FM.
•Th
e m
ost
sign
ific
ant
adva
ntag
es o
f th
e ch
irp
tech
niqu
esov
er o
ther
pul
se H
F sy
stem
are
:•
the
redu
ced
vuln
erab
ility
to
narr
ow-b
and
inte
rfer
ence
•th
e us
e of
low
powe
r du
e to
the
abi
lity
to t
rans
mit
wit
h a
near
ly u
nit
duty
cyc
le.
CHIR
P
Chir
p m
odul
atio
n (C
W-F
M)
Chir
p io
noso
nde
Chir
p te
chni
ques
1
Chir
p te
chni
ques
2
• F
requ
ency
ana
lysi
s of
the
de-
chir
ped
sign
al is
know
n to
be
iden
tica
l to
a m
atch
ed f
ilter
in p
ulse
com
pres
sion
rad
ar. T
he p
ulse
com
pres
sion
rat
io G
is g
iven
by:
G =
BT
w
here
B is
the
fre
quen
cy s
weep
ran
ge a
nd T
isth
e ti
me
dura
tion
for
one
spe
ctru
m a
naly
sis]
.Ra
nge
reso
luti
on ∆
r is
giv
en b
y:
∆r
= c
/ 2B
w
here
c is
the
vel
ocit
y of
ligh
t.
Obl
ique
sou
ndin
g
Obl
ique
iono
gram
Phas
e-co
ded
iono
sond
e
Code
gen
erat
ion
base
band
Tim
e-do
mai
n co
rrel
atio
n
Puls
e co
mpr
essi
on
The
phas
e pa
th P
is g
iven
by
Proc
essi
ng g
ain
•M
ore
or le
ss 3
0 dB
•A
bout
15
dB d
ue t
o co
rrel
atio
npr
oces
s
•A
bout
15
dB d
ue t
o ph
ase
cohe
rent
inte
grat
ion
The
reco
nstr
uction
of
the
code
, ba
seba
nd,
star
ting
fro
m t
he e
cho
sign
al is
the
follo
wing
:•the
ana
log
sign
al a
t th
e ou
tput
of
the
IF (
typica
lly 1
00 k
Hz)
is
sampled
bot
h in p
hase
and
quad
ratu
re a
t th
e sa
me
freq
uenc
y•the
qu
adra
ture
sam
pling
allows
to
obta
in t
heam
plitud
e an
d, m
ore
impo
rtan
t, t
he ph
ase
of t
hesign
al t
o re
cons
truc
t th
e ba
seba
nd•a
fter
the
A/D
con
vers
ion
the
signa
l is f
edth
roug
h th
e digita
l mat
ched
file
r im
plem
ente
d on
the
DSP
boa
rd•the
pro
cess
is
repe
ated
for
the
eve
n an
d od
dco
de if
complem
enta
ry c
ode
is u
sed.
Code
rec
onst
ruct
ion
Com
plem
enta
ry c
ode
In t
he c
ompl
emen
tary
pha
se c
ode
the
sid
e lo
bes
of t
heco
rrel
atio
n pr
oces
s an
d in
a c
erta
in m
easu
re t
he n
oise
supe
rim
pose
d to
the
sig
nal
16.0
0272
7
3.01
0122
u1l
u2l
240
180
l18
019
020
021
022
023
024
010
0
1020
l
32.0
0177
6
0.04
5786
u1l
u2l
180
190
200
210
220
230
240
2002040
Pu
lse
compr
ession
tec
hnique
The
ener
gy (E
) of
the
echo
sig
nal f
rom
the
iono
sphe
re, u
nder
cert
ain
prop
agat
ive
cond
itio
n, i
s pr
opor
tion
al t
o th
etr
ansm
itte
d po
wer
(P) a
nd t
he p
ulse
leng
th (T
)E=
P ⋅T
In t
he o
ld io
noso
nde
the
powe
r P
was
of t
he o
rder
of
1000
0W
whi
le t
he p
ulse
leng
th, t
o ha
ve t
he d
esir
ed h
igh
reso
luti
on, w
as 3
0 µs
, so
the
ener
gy w
as o
f th
e or
der
of 0
.3J. Th
e ph
ase
code
d H
F ra
dar
uses
a p
ulse
leng
th o
f ab
out
500
µs a
nd a
pow
er o
f 20
0 W
and
the
ene
rgy
of t
he p
ulse
is 0
.1 J
(sam
e or
der
of m
agni
tude
). T
he r
esol
utio
n is
mai
ntai
ned
beca
use
an a
dequ
ate
num
ber
of s
ub-p
ulse
τ c
onst
itut
e th
epu
lse
leng
th T
.
1
•Th
e pa
rtic
ular
seq
uenc
e of
the
sub
-pul
ses
that
is w
hat
we s
ay a
cod
e.
The
puls
eco
mpr
essi
on c
onsi
sts
to in
put
the
puls
e T
(sub
puls
e se
quen
ce) i
n a
mat
ched
filt
er,
whic
h is
sen
siti
ve o
nly
to t
he c
hose
n co
de,
whos
e ou
tput
con
cent
rate
its
ener
gy in
ati
me τ.
•So
the
mat
ched
filt
er m
agni
fies
onl
y th
ese
gmen
t of
the
sig
nal t
hat
cont
ains
the
code
seq
uenc
e.
Filt
erin
g an
d in
tegr
atio
n
•A
fter
the
FFT
a d
igit
al f
ilter
to
redu
ce t
he a
mpl
itud
e of
the
stro
nges
t f
requ
ency
co
mpo
nent
, can
be
impl
emen
ted.
This
filt
er c
ut o
ut t
he f
requ
ency
of
the
inte
rfer
ing
radi
obr
oadc
asti
ng e
tc..
This
filt
er f
ollo
ws e
mpi
rica
l cr
iter
ia a
ndca
n b
e m
odif
ied
acc
ordi
ng t
o t
he p
arti
cula
r so
undi
ng s
ite.
•Th
e ph
ase
cohe
rent
inte
grat
ion
is a
sum
in t
he f
requ
ency
dom
ain
last
ing
till
the
phas
e di
ffer
ence
bet
ween
the
fir
stan
d th
e la
st e
choe
s of
the
inco
min
g si
gnal
is le
ss t
han
90
degr
ees.
Aft
er t
hat
the
inte
grat
ion
proc
ess
is n
ot u
sefu
l.Th
is p
roce
ss t
akes
into
acc
ount
the
tim
e co
here
nce
of t
here
flec
tion
pro
cess
in t
he io
nosp
here
.
Dig
ital
sig
nal p
roce
ssin
g 1
Dig
ital
sig
nal p
roce
ssin
g 2
Dig
ital
sig
nal p
roce
ssin
g 3
Dig
ital
sig
nal p
roce
ssin
g 4