Transmitter with reduced counter-intermodulation

A system, comprising:

• a mixer component configured to mix a baseband current with a local oscillator frequency, an output of the mixer component including a radio frequency signal and a higher order radio frequency signal;
• a balun coupler connected with the mixer component, the balun coupler configured to send the radio frequency signal to a differential output of the balun coupler, the differential output having a positive terminal and a negative terminal, the balun coupler including a notch filter component integrated into the balun coupler, the notch filter component comprising a capacitor coupled in series with an inductor, wherein the capacitor in series with the inductor are coupled with the positive terminal and the negative terminal in parallel with the differential output to filter the higher order radio frequency signal before being output by the differential output:
• and
• a cascode transistor component and a second filter component connected with an input of the cascode transistor component, the cascode transistor component and the second filter component being coupled between the mixer component and the balun coupler, and the second filter component configured to initially filter the higher order radio frequency signal in a current domain before the balun coupler, and the notch filter component configured to subsequently filter the higher order radio frequency signal after the balun coupler, the second filter component comprising a differential capacitor connected in parallel with the cascode transistor component and another capacitor coupled in parallel with an input of the balun coupler.

A method of mixing a signal, comprising:

• converting a baseband voltage signal to a baseband current signal;
• mixing, with a mixer component, the baseband current signal with a local oscillator frequency signal to obtain an unconverted signal comprising a radio frequency signal and a higher order radio frequency signal;
• first filtering the unconverted signal output from the mixer component in a current domain at a cascode device coupled in parallel with a differential capacitor and another capacitor coupled across an input of a balun transformer to initially filter out the higher order radio frequency signal before input to the balun transformer;
• and
• filtering out the higher order radio frequency signal after the balun transformer by creating a short circuit of the higher order radio frequency signal at a differential output of a balun before outputting the radio frequency signal to a non-linear block of circuitry, the short circuit created by a notch filter integrated in the balun transformer, the notch filter comprising an inductor coupled in series with a capacitor, one of the inductor or the capacitor coupled with a positive output of the differential output and the other of the inductor or the capacitor coupled with a negative output of the differential output.