Communicating with a self-clocking amplitude modulated signal

1. A method for transmitting a signal, the method comprising:

generating a Manchester encoded data stream;

combining the Manchester encoded data stream with an amplified clock signal to produce an amplitude modulated signal having a zero crossing at each edge of the amplified clock signal, wherein combining the Manchester encoded data stream with an amplified clock signal includes subtracting the voltage of the Manchester encoded data stream from the voltage of the amplified clock signal; and

sending the amplitude modulated signal over a communication medium.

2. The method of claim 1 , comprising:

amplifying a clock signal to produce the amplified clock signal, wherein amplifying includes producing a signal having a peak-to-peak amplitude greater than a peak-to-peak amplitude of the Manchester encoded data stream.

3. The method of claim 1 , wherein sending the amplitude modulated signal includes sending the amplitude modulated signal as a square wave.

4. The method of claim 2 , wherein amplifying includes producing a signal having a peak-to-peak amplitude twice that of the peak-to-peak amplitude of the Manchester encoded data stream.

5. The method of claim 2 , wherein generating a Manchester encoded data stream includes XORing the clock signal with a data signal.

6. A method for transmitting an amplitude modulated signal, the method comprising:

encoding a data signal to produce a DC balanced data signal;

combining the DC balanced data signal with a clock signal to produce a plurality of square wave pulses having edges corresponding to edges of the clock signal and amplitudes corresponding to a digital value of the data signal, wherein each of the plurality of square wave pulses has an amplitude larger than a threshold amplitude to represent a first digital level of the data signal, and each of the plurality of square wave pulses has an amplitude smaller than the threshold amplitude to represent a second digital level of the data signal; and

transmitting the plurality of square wave pulses.

7. The method of claim 6 , wherein the threshold amplitude when positive corresponds to a positive voltage level and when negative corresponds to a negative voltage level, and wherein transmitting a plurality of square wave pulses includes:

transmitting a pulse having a positive amplitude above the positive voltage level when the data signal and the clock signal are at the first digital level;

transmitting a pulse having a negative amplitude below the negative voltage level when the data signal is at the first digital level and the clock signal is at a second voltage level;

transmitting a pulse having a positive amplitude below the positive voltage level when the data signal is at the second digital level and the clock signal is at the first digital level; and

transmitting a pulse having a negative amplitude above the negative voltage level when the data signal and the clock signal are at the second digital level.

8. The method of claim 7 , wherein transmitting a pulse having a positive amplitude above the positive voltage level includes transmitting a pulse having about three times the amplitude of a pulse having a positive amplitude below the positive voltage level.

9. A transmitter comprising:

an encoding circuit configured to receive a clock stream and a data stream, the encoding circuit configured to combine the clock stream and data stream into one or more intermediate signals; and

a plurality of current sources coupled to the encoding circuit and configured to receive the intermediate signals, wherein the encoding circuit and plurality of current sources are configured to generate an amplitude modulated signal having edges corresponding to edges of the clock stream and an amplitude corresponding to the data stream.

10. The transmitter of claim 9 , wherein the one or more intermediate signals include a Manchester encoded stream.

11. The transmitter of claim 9 , wherein the plurality of current sources are configured to generate a pulse having an amplitude larger than a threshold amplitude when the data stream is at a first digital level, and transmitting a pulse having an amplitude smaller than the threshold amplitude when the data stream is at a second digital level.

12. The transmitter of claim 9 , wherein the plurality of current sources include a first current source and a second current source, the second current source configured to generate a greater current than the first current source;

wherein the one or more intermediate signals include control signals coupled to the first and second current sources, the control signals configured to switch the first current source based on the data stream being at a first digital level and to switch the second current source based on the data stream being at a second digital level.

13. The transmitter of claim 9 , wherein the one or more intermediate signals are configured to generate a square wave signal with the one or more current sources.