Transconductance/C complex band-pass filter

A complex filter comprising:

• n stages connected in cascade, each of the n stages comprising:
• a first and second transconductor each having a first transconductance and each having an input coupled to a first and second input signal respectively;
• a third and fourth transconductor configured as a gyrator, each having a second transconductance and each having an input coupled to an output of the first and second transconductor respectively;
• and
• a first and second impedance each coupled to an output of the third and fourth transconductance respectively.

A method of implementing a complex gm/C filter based on a biquadratic filter topology, the gm/C filter having a transfer characteristic and having n stages said method comprising:

• for each of the n stages:
• buffering a first and second stage input with a gain stage, the gain stage comprising at least two transconductors having a first transconductance (gm1);
• and
• establishing at least one pole of the transfer characteristic with a gyrator, the gyrator comprising at least two transconductors having a second transconductance (gm2), the gyrator further comprising a first and second input coupled to a first and second output of the gain stage, and a first and second stage output coupled to a first (Z1) and a second (Z2) impedance respectively, wherein Z1 and Z2 comprise a capacitance (C).

A Radio Frequency (RF) receiver of a wireless device comprising an amplifier for amplifying a received RF signal comprising to or more channels, the amplifier coupled to a down-converter for converting the received RF signal to a down-converted IF or baseband frequency, the RF receiver further comprising:

• a channel select filter for selecting one of the one or more channels of the RF signal, the channel select filter operable to receive the down-converted signal from the down-converter, the channel select filter further comprising:
• n stages connected in cascade, each of the n stages comprising:
• a first and second transconductor each having a first transconductance and each having an input coupled to a first and second input signal respectively;
• a third and fourth transconductor configured as a gyrator, each having a second transconductance and each having an input coupled to an output of the first and second transconductor respectively;
• and
• a first and second impedance each coupled to an output of the third and fourth transconductance respectively;
• wherein the transfer function of the channel select filter is substantially equal to
• g
• m1
• ⁢
• g
• m2
• ⁢
• Z
• 1
• ⁢
• Z
• 2
• 1
• +
• g
• m2
• 2
• +
• (
• Z
• 1
• ⁢
• Z
• 2
• )
• ,
• wherein gm1 is the first transconductance, gm2 is the second transconductance, Z1, is the first impedance and Z2 is the second impedance;
• and
• wherein
• Z
• 1
• =
• Z
• 2
• =
• R
• 1
• +
• sRC
• ,
• wherein R is a resistance and C is a capacitance.