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 comprising:
a transmission device configured to transmit a pulsed voltage signal 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 system configured to match the transmission frequency of the antenna to the value of the predetermined fundamental frequency (f F );
a filter configured to filter the parasitic voltage signals, the filter being electrically connected to the transmission unit and the matching system;
a voltage source, connected to the matching system and supplying voltage to the transmission device,
wherein the filter comprises:
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 ) each have an inductance (L i ) such that, at the predetermined fundamental frequency (f F ), each of the (n−1) coil have a natural resonance frequency (F RLi ) equal to:
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, and such that each coil of the “n” coils has an impedance equal to:
Z i =K×L i
where
K=j×ω,
with:
ω=2×π× f F
and such that for all of the “n” coils:
Z TOT =( Z 1 +Z 2 + . . . +Z i + . . . Z n )= K×L TOT =K ×( L 1 +L 2 + . . . +L i + . . . L n )
with:
L TOT being the total inductance of the “n” coils (H),
L i being the inductance of the i-th coil (H),
Z TOT being the total impedance of the “n” coils (Ω),
Z i being the impedance of the i-th coil (Ω),
n being an integer greater than zero,
f F being the predetermined fundamental frequency (Hz),
j being the complex part,
π being equal to 3.14, and
ω being the angular speed.
2. The radiofrequency transmission device according to claim 1 , wherein the filter comprises three coils.
3. The radiofrequency transmission device according to claim 1 , wherein the predetermined fundamental frequency (fF) is in the range from 310 MHz to 434 MHz.
4. A wheel unit, comprising:
the radiofrequency transmission device according to claim 1 .
5. A hands free access badge for accessing a motor vehicle, comprising:
the radiofrequency transmission device according to claim 1 .
6. A motor vehicle, comprising:
the radiofrequency transmission device according to claim 1 .