RADIOFREQUENCY TRANSMISSION DEVICE
A radiofrequency transmission device (D′) includes: a transmission unit ( 10 ) for transmitting a voltage signal (S) in pulsed form; a radiofrequency antenna (A); filtering elements ( 30 ′); and a voltage source (Vcc), wherein the filtering elements ( 30 ′) include: “n” coils (B 1 , B 2 . . . B n ), electrically connected in series, of which (n−1) coils each have a natural resonance frequency such that: f RLi =i×f F each having an inductance (L i ) such that, at the predetermined fundamental frequency: L TOT =L 1 +L 2 + . . . L i + . . . L n =Z TOT =Z 1 +Z 2 + . . . Z i + . . . Z n and L i =Z i where f RLi Is the natural resonance frequency of the i-th coil i is a number varying from 2 to n, L TOT is the total inductance of the n coils, L i is the inductance of the i-th coil, Z TOT is the total impedance of the n coils, Z i is the impedance of the i-th coil, n is an integer greater than zero.
1 . A radiofrequency transmission device (D′) comprising:
a transmission unit ( 10 ) for transmitting a pulsed voltage signal (S) at a predetermined fundamental frequency (f F ), generating parasitic voltage signals at frequencies which are multiples of the predetermined fundamental frequency (f F ),
a radiofrequency antenna (A),
matching means (M 1 ′) for matching the transmission frequency of the antenna (A) to the value of the predetermined fundamental frequency (f F ),
filtering means ( 30 ′) for filtering the parasitic voltage signals,
a voltage source (Vcc), connected to the matching means (M 1 ) and supplying voltage to the transmission unit ( 10 ),
wherein:
the filtering means ( 30 ′) are electrically connected to the transmission unit ( 10 ), and to the matching means (M 1 ′), and
said filtering means ( 30 ′) comprise:
a number “n” of coils (B 1 , B 2 , B i . . . B n ), electrically connected in series with each other, of which (n−1) coils (B 2 , B 3 , B 4 , . . . B n ) have a natural resonance frequency (f RLi ) such that:
f RLi =i×f F
where
f RLi is the natural resonance frequency of the i-th coil (B i ) ,
i is a number varying from 2 to n,
f F is the predetermined fundamental frequency.
each having an inductance (L i ) such that, at the predetermined fundamental frequency (f F ):
L TOT =L 1 +L 2 + . . . L i + . . . L n =Z TOT =Z 1 +Z 2 + . . . Z i + . . . Z n
and
L i =Z i
where
L TOT is the total inductance of the “n” coils,
L i is the inductance of the i-th coil (B i ),
Z TOT is the total impedance of the “n” coils,
Z i is the impedance of the “i-th” coil (B i ),
n is an integer greater than zero.
2 . The radiofrequency transmission device (D′) as claimed in claim 1 , wherein the filtering means ( 30 ′) comprise three coils (B 1 , B 2 , B 3 ).
3 . The radiofrequency transmission device (D′) as claimed in claim 1 , wherein the predetermined fundamental frequency (f F ) is in the range from 310 MHz to 434 MHz.
4 . A wheel unit, which comprises a radiofrequency transmission device (D′) as claimed in claim 1 .
5 . A hands free access badge for accessing a motor vehicle, wherein the hands free access badge comprises a radiofrequency transmission device (D′) as claimed in claim 1 .
6 . A motor vehicle, which comprises a radiofrequency transmission device (D′) as claimed in claim 1 .
7 . The radiofrequency transmission device (D′) as claimed in claim 2 , wherein the filtering means ( 30 ′) comprise three coils (B 1 , B 2 , B 3 ).
8 . A wheel unit, which comprises a radiofrequency transmission device (D′) as claimed in claim 2 .
9 . A wheel unit, which comprises a radiofrequency transmission device (D′) as claimed in claim 3 .
10 . A hands free access badge for accessing a motor vehicle, wherein the hands free access badge comprises a radiofrequency transmission device (D′) as claimed in claim 2 .
11 . A hands free access badge for accessing a motor vehicle, wherein the hands free access badge comprises a radiofrequency transmission device (D′) as claimed in claim 3 .
12 . A motor vehicle, which comprises a radiofrequency transmission device (D′) as claimed in claim 2 .
13 . A motor vehicle, which comprises a radiofrequency transmission device (D′) as claimed in claim 3 .