Impedance matching network
An impedance matching network ( 10 ) for an active RFID transceiver ( 1 ), the impedance matching network ( 10 ) including: an impedance transformer ( 14 ) including a transformer input ( 13 ) and a transformer output ( 15 ), wherein the transformer input ( 13 ) is connectable to an antenna ( 12 ), an RF modulator ( 16 ) connectable to the transformer output ( 15 ), and an RF demodulator ( 20 ) capacitively coupled to the transformer output ( 15 ) via a capacitor ( 18 ).
1 . An impedance matching network ( 10 ) for an active RFID transceiver ( 1 ), the impedance matching network ( 10 ) comprising:
an impedance transformer ( 14 ) comprising a transformer input ( 13 ) and a transformer output ( 15 ), wherein the transformer input ( 13 ) is connectable to an antenna ( 12 ),
an RF modulator ( 16 ) connectable to the transformer output ( 15 ), and
an RF demodulator ( 20 ) capacitively coupled to each of the transformer output ( 15 ) and the RF modulator ( 16 ) via a capacitor ( 18 ).
2 . The impedance matching network ( 10 ) according to claim 1 , wherein the impedance transformer ( 14 ) comprises a first branch ( 21 ) provided with a first inductor ( 22 ), the first branch ( 21 ) being connected to the transformer input ( 13 ) with a first end and being connected to the RF modulator ( 16 ) with a second end.
3 . The impedance matching network ( 10 ) according to claim 1 , further comprising a second branch ( 23 ) provided with a second inductor ( 24 ), the second branch ( 23 ) being connected to the RF modulator ( 16 ) with a first end and being connected to ground with a second end.
4 . The impedance matching network ( 10 ) according to claim 2 , further comprising a second branch ( 23 ) provided with a second inductor ( 24 ), the second branch ( 23 ) being connected to the RF modulator ( 16 ) with a first end and being connected to ground with a second end,
wherein an inductance of the first inductor ( 22 ) is larger than an inductivity of the second inductor ( 24 ).
5 . The impedance matching network ( 10 ) according to claim 2 , further comprising a second branch ( 23 ) provided with a second inductor ( 24 ), the second branch ( 23 ) being connected to the RF modulator ( 16 ) with a first end and being connected to ground with a second end,
wherein the first end of the second branch ( 24 ) is connected to the first inductor ( 22 ).
6 . The impedance matching network ( 10 ) according to claim 1 , further comprising a third branch ( 25 ) provided with a tunable capacitor ( 26 ), the third branch ( 25 ) being connected to the RF modulator ( 16 ) with a first end and being connected to ground with a second end.
7 . The impedance matching network ( 10 ) according to claim 2 , further comprising a third branch ( 25 ) provided with a tunable capacitor ( 26 ), the third branch ( 25 ) being connected to the RF modulator ( 16 ) with a first end and being connected to ground with a second end,
wherein the first end of the third branch ( 25 ) is connected to the first inductor ( 22 ).
8 . The impedance matching network ( 10 ) according to claim 2 , wherein at least one of the RF modulator ( 16 ) and the RF demodulator ( 20 ) is implemented in an integrated circuit ( 8 ) and wherein the first inductor ( 22 ) is external to the integrated circuit ( 8 ).
9 . The impedance matching network ( 10 ) according to claim 1 , wherein the RF modulator ( 16 ) comprises a tunable resistor ( 30 ).
10 . The impedance matching network ( 10 ) according to claim 9 , wherein the tunable resistor ( 30 ) comprises a first resistor branch ( 37 ) and at least a second resistor branch ( 38 ) parallel to the first resistor branch ( 37 ), wherein at least one of the first resistor branch ( 37 ) and the second resistor branch ( 38 ) comprises a resistor ( 31 , 33 ) in line with a switch ( 32 , 34 ).
11 . An impedance matching network ( 10 ) for an active RFID transceiver ( 1 ), the impedance matching network ( 10 ) comprising:
an impedance transformer ( 14 ) comprising a transformer input ( 13 ) and a transformer output ( 15 ), wherein the transformer input ( 13 ) is connectable to an antenna ( 12 ),
an RF modulator ( 16 ) connectable to the transformer output ( 15 ), and
an RF demodulator ( 20 ) capacitively coupled to the transformer output ( 15 ) via a capacitor ( 18 ), wherein the RF demodulator ( 20 ) comprises a push pull amplifier ( 50 ) comprising a first and a second PMOS transistor (Pla, P 1 b ) and a first and a second NMOS transistor (N 1 a , N 1 b ) and wherein the gates of the first and second NMOS transistor are connected to the transformer output ( 15 ) via the capacitor ( 18 ).
12 . The impedance matching network ( 10 ) according to claim 11 , wherein the RF demodulator ( 20 ) comprises a common mode feedback loop ( 40 ) connected with a first end to a drain of the first PMOS transistor (P 1 a ) and to a drain of the second PMOS transistor (P 1 b ) and connected with a second end to a source of the first NMOS transistor (N 1 a ) and to a source of the second NMOS transistor (N 2 a ).
13 . An active RFID transceiver ( 1 ) comprising:
an antenna ( 12 ),
the impedance matching network ( 10 ) according to claim 1 and connected to the antenna ( 12 ), and
a signal processor ( 60 ) connected to an output of the RF demodulator ( 20 ) of the impedance matching network ( 10 ).