Method and apparatus for a class-E load tuned beamforming 60 GHz transmitter
View Patent ↗The class-E amplifier can be tuned to pass only the fundamental frequency to the antenna by optimizing the second harmonics at the drain of the final PA driver transistor. A CPW in series with a capacitor between the PA transistor and the load forms a band pass filter that only allows the fundamental frequency to pass to the load of the antenna. A supply inductor to couple the drain of the final PA driver transistor to the power supply is tuned at the second harmonic with the parasitic capacitance of the drain of the PA transistor. A load capacitance is adjusted at the fundamental frequency to insure that the current waveform and voltage waveforms at the drain of the PA driver transistor do not overlap, thereby minimizing the parasitic power dissipation and allowing maximum energy to be applied to the antenna.
1. A Class E amplifier comprising:
a first transistor with a gate, source, drain and substrate;
an input coupled to said gate;
said source coupled to a ground supply;
an inductor coupled between a power supply and said drain;
said drain coupled to a first co-planar waveguide in series with a first capacitor;
said first capacitor coupled to a signal pad;
an output of a second transistor capacitively coupled to a gate of said first transistor;
an output of a balun coupled to input of said second transistor; and
a second co-planar waveguide coupled between said output of said second transistor and said power supply.
2. The apparatus of claim 1 , further comprising:
a second capacitor coupled between said signal pad and said ground supply.
3. The apparatus of claim 1 , wherein
said substrate is coupled to said ground supply.
4. The apparatus of claim 1 , wherein
said signal pad is coupled to an antenna.
5. An apparatus comprising:
an inductor coupled between a power supply and an output of a first transistor;
said output of said first transistor coupled to a co-planar waveguide in series with a capacitor;
said capacitor coupled to a signal pad;
a second capacitor coupled between said signal pad and a ground supply;
an output of a second transistor capacitively coupled to a gate of said first transistor;
a second co-planar waveguide coupled between said output of said second transistor and said power supply; and
an output of a balun coupled to said input of said second transistor.
6. The apparatus of claim 5 , further comprising:
inputs of said balun driven by outputs of a composite mixer that up-converts an input signal.
7. The apparatus of claim 6 , further comprising:
an antenna coupled to said signal pad, whereby
said up-converted input signal is propagated into free space from said antenna as electromagnetic radiation.
8. A method of passing a signal with a fundamental frequency to a signal pad, comprising the steps of:
coupling said signal to an input of a transistor;
coupling an inductor between a power supply and an output of said transistor;
coupling said output of said transistor to a co-planar waveguide in series with a first capacitor;
coupling said first capacitor to a signal pad;
capacitively coupling an output of a second transistor to a gate of said first transistor;
coupling an output of a balun to input of said second transistor; and
coupling a second co-planar waveguide between said output of said second transistor and said power supply.
9. The method of claim 8 , further comprising the steps of:
coupling a second capacitor between said signal pad and a ground supply.
10. The method of claim 9 , wherein said inductor is adjusted to resonate at a second harmonic with a drain capacitance of said transistor.
11. The method of claim 10 , wherein the waveform is shaped at said output of transistor to constrain a fundamental impedance.
12. The method of claim 11 , wherein a value of said second capacitor is adjusted to achieve a desired susceptance at said fundamental frequency.
13. The method of claim 8 , wherein current and voltage waveforms at a drain of said transistor non-overlap.