Low power radio transmitter using pulse transmissions

1. A radio transmitter comprises:

intermediate frequency stage operably coupled to up-convert frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

signal to pulse conversion module operably coupled to convert the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency, wherein N is greater than M, and wherein the signal to pulse conversion module includes:

rate converter operably coupled to increase rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulator operably coupled to convert the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency;

second rate converter operably coupled to increase rate of the J-bit pulse density signal at the intermediate frequency to produce a rate increased L-bit signal at the intermediate frequency; and

radio frequency module operably coupled to increase frequency of the rate increased L-bit signal at the intermediate frequency into the M-bit signal at the radio frequency; and

power amplifier operably coupled to amplify the M-bit signal at the radio frequency.

2. The radio transmitter of claim 1 , wherein the intermediate frequency stage further comprises:

first mixing module operably coupled to mix an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

second mixing module operably coupled to mix a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing module operably coupled to sum the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

3. The radio transmitter of claim 1 further comprises:

the rate converter including:

oversampling module operably coupled to oversample the N-bit signal at the intermediate frequency to produce an oversampled N-bit signal; and

sample and hold module operably coupled to sample and hold, at a first rate, the oversampled N-bit signal to produce the rate increased K-bit signal at the intermediate frequency; and

the second rate converter including:

second oversampling module operably coupled to oversample the J-bit pulse density signal at the intermediate frequency to produce an oversampled M-bit signal; and

second sample and hold module operably coupled to sample and hold, at a second rate, the oversampled M-bit signal to produce the rate increased L-bit signal at the intermediate frequency.

4. The radio transmitter of claim 1 , wherein the pulse density modulator further comprises:

bandpass sigma delta modulator that includes:

first summing module to subtract a feedback signal from an input signal to produce a first resultant, wherein the feedback signal is representative of the J-bit pulse density signal at the intermediate frequency and the input signal is representative of the rate increased K-bit signal at the intermediate frequency;

bandpass integrator module operably coupled to integrate components of the first resultant in a bandpass region to produce a bandpass integrated signal;

second summing module operably coupled to subtract a second feedback signal from the bandpass integrated signal to produce a second resultant, wherein the second feedback signal is representative of a scaled version of the J-bit pulse density signal at the intermediate frequency; and

integrator module operably coupled to integrate the second resultant to produce the J-bit pulse density signal at the intermediate frequency.

5. The radio transmitter of claim 1 , wherein the power amplifier comprises at least one of:

comparator operably coupled to compare the M-bit signal at the radio frequency with a reference to produce an amplified M-bit signal;

class A amplifier operably coupled to amplify the M-bit signal at the radio frequency;

inverter operably coupled to invert the M-bit signal at the radio frequency; and

transistor pull-up and pull-down circuit operably coupled to amplify the M-bit signal at the radio frequency.

6. The radio transmitter of claim 1 further comprises:

ceramic bandpass filter operably coupled to bandpass filter an output of the power amplifier to produce a bandpass M-bit square wave signal; and

an antenna operably coupled to transmit the bandpass M-bit square wave signal.

7. A method for radio frequency signal transmissions, the method comprises:

up-converting frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

converting the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency, wherein N is greater than M, and wherein the converting of the N-bit signal at the intermediate frequency into the M-bit signal at the radio frequency includes:

increasing rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulating the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency;

increasing rate of the J-bit pulse density signal at the intermediate frequency to produce a rate increased L-bit signal at the intermediate frequency; and

increasing frequency of the rate increased L-bit signal at the intermediate frequency into the M-bit signal at the radio frequency; and

amplifying the M-bit signal at the radio frequency.

8. The method of claim 7 , wherein the up-converting the frequency of the baseband signal further comprises:

mixing an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

mixing a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

9. The method of claim 7 further comprises:

increasing rate of the N-bit signal at the intermediate frequency includes:

oversampling the N-bit signal at the intermediate frequency to produce an oversampled N-bit signal; and

sampling and holding, at a first rate, the oversampled N-bit signal to produce the rate increased K-bit signal at the intermediate frequency; and

increasing rate of the J-bit pulse density signal at the intermediate frequency includes:

oversampling the J-bit pulse density signal at the intermediate frequency to produce an oversampled M-bit signal; and

sampling and holding, at a second rate, the oversampled M-bit signal to produce the rate increased L-bit signal at the intermediate frequency.

10. The method of claim 7 , wherein the pulse density modulating further comprises:

subtracting a feedback signal from an input signal to produce a first resultant, wherein the feedback signal is representative of the J-bit pulse density signal at the intermediate frequency and the input signal is representative of the rate increased K-bit signal at the intermediate frequency;

bandpass integrating components of the first resultant in a bandpass region to produce a bandpass integrated signal;

subtracting a second feedback signal from the bandpass integrated signal to produce a second resultant, wherein the second feedback signal is representative of a scaled version of the J-bit pulse density signal at the intermediate frequency; and

integrating the second resultant to produce the J-bit pulse density signal at the intermediate frequency.

11. The method of claim 7 further comprises:

bandpass filtering the amplified M-bit signal at the radio frequency to produce a bandpass M-bit square wave signal; and

providing the bandpass M-bit square wave signal to an antenna for transmission.

12. An apparatus for radio frequency signal transmissions, the apparatus comprises:

processing module; and

memory operably coupled to the processing module, wherein the memory includes operational instructions that cause he processing module to:

up-convert frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

convert the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency by:

increasing rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulating the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency;

increasing rate of the J-bit pulse density signal at the intermediate frequency to produce a rate increased L-bit signal at the intermediate frequency; and

increasing frequency of the rate increased L-bit signal at the intermediate frequency into the M-bit signal at the radio frequency;

wherein N is greater than M; and

amplify the M-bit signal at the radio frequency.

13. The apparatus of claim 12 , wherein the memory further comprises operational instructions that cause the processing module to up-convert the frequency of the baseband signal by:

mixing an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

mixing a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

14. The apparatus of claim 13 , wherein the memory further comprises operational instructions that cause the processing module to:

increase rate of the N-bit signal at the intermediate frequency by:

oversampling the N-bit signal at the intermediate frequency to produce an oversampled N-bit signal; and

sampling and holding, at a first rate, the oversampled N-bit signal to produce the rate increased K-bit signal at the intermediate frequency; and

increase rate of the J-bit pulse density signal at the intermediate frequency by:

oversampling the J-bit pulse density signal at the intermediate frequency to produce an oversampled M-bit signal; and

sampling and holding, at a second rate, the oversampled M-bit signal to produce the rate increased L-bit signal at the intermediate frequency.

15. The apparatus of claim 13 , wherein the memory further comprises operational instructions that cause the processing module to pulse density modulate by:

subtracting a feedback signal from an input signal to produce a first resultant, wherein the feedback signal is representative of the J-bit pulse density signal at the intermediate frequency and the input signal is representative of the rate increased K-bit signal at the intermediate frequency;

bandpass integrating components of the first resultant in a bandpass region to produce a bandpass integrated signal;

subtracting a second feedback signal from the bandpass integrated signal to produce a second resultant, wherein the second feedback signal is representative of a scaled version of the J-bit pulse density signal at the intermediate frequency; and

integrating the second resultant to produce the J-bit pulse density signal at the intermediate frequency.

16. The apparatus of claim 12 , wherein the memory further comprises operational instructions that cause the processing module to:

bandpass filter the amplified M-bit signal at the radio frequency to produce a bandpass M-bit square wave signal; and

provide the bandpass M-bit square wave signal to an antenna for transmission.

17. A radio transmitter comprises:

intermediate frequency stage operably coupled to up-convert frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

signal to pulse conversion module operably coupled to convert the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency, wherein N is greater than M, the signal to pulse conversion module including:

a rate converter operably coupled to increase rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulator operably coupled to convert the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency; and

radio frequency module operably coupled to increase frequency of the J-bit pulse density signal at the intermediate frequency into the M-bit signal at the radio frequency; and

power amplifier operably coupled to amplify the M-bit signal at the radio frequency.

18. The radio transmitter of claim 17 , wherein the intermediate frequency stage further comprises:

first mixing module operably coupled to mix an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

second mixing module operably coupled to mix a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing module operably coupled to sum the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

19. The radio transmitter of claim 17 , wherein the power amplifier comprises at least one of:

comparator operably coupled to compare the M-bit signal at the radio frequency with a reference to produce an amplified M-bit signal;

class A amplifier operably coupled to amplify the M-bit signal at the radio frequency;

inverter operably coupled to invert the M-bit signal at the radio frequency; and

transistor pull-up and pull-down circuit operably coupled to amplify the M-bit signal at the radio frequency.

20. The radio transmitter of claim 17 further comprises:

ceramic bandpass filter operably coupled to bandpass filter an output of the power amplifier to produce a bandpass M-bit square wave signal; and

an antenna operably coupled to transmit the bandpass M-bit square wave signal.

21. A method for radio frequency signal transmissions, the method comprises:

up-converting frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

converting the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency, wherein N is greater than M, and wherein the converting of the N-bit signal at the intermediate frequency into the M-bit signal at the radio frequency includes:

increasing rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulating the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency; and

increasing frequency of the J-bit pulse density signal at the intermediate frequency into the M-bit signal at the radio frequency; and

amplifying the M-bit signal at the radio frequency.

22. The method of claim 21 , wherein the up-converting the frequency of the baseband signal further comprises:

mixing an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

mixing a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

23. The method of claim 21 further comprises:

bandpass filtering the amplified M-bit signal at the radio frequency to produce a bandpass M-bit square wave signal; and

providing the bandpass M-bit square wave signal to an antenna for transmission.

24. An apparatus for radio frequency signal transmissions, the apparatus comprises:

processing module; and

memory operably coupled to the processing module, wherein the memory includes operational instructions that cause he processing module to:

up-convert frequency of a baseband digital signal into an N-bit signal at an intermediate frequency;

convert the N-bit signal at the intermediate frequency into an M-bit signal at a radio frequency by:

increasing rate of the N-bit signal at the intermediate frequency to produce a rate increased K-bit signal at the intermediate frequency;

pulse density modulating the rate increased K-bit signal at the intermediate frequency into an J-bit pulse density signal at the intermediate frequency; and

increasing frequency of the J-bit pulse density signal at the intermediate frequency into the M-bit signal at the radio frequency;

wherein N is greater than M, and

amplify the M-bit signal at the radio frequency.

25. The apparatus of claim 24 , wherein the memory further comprises operational instructions that cause the processing module to up-convert the frequency of the baseband signal by:

mixing an in-phase component of the baseband digital signal with an in-phase intermediate frequency signal to produce a first mixed signal;

mixing a quadrature component of the baseband digital signal with a quadrature intermediate frequency signal to produce a second mixed signal; and

summing the first and second mixed signals to produce the N-bit signal at the intermediate frequency.

26. The apparatus of claim 24 , wherein the memory further comprises operational instructions that cause the processing module to:

bandpass filter the amplified M-bit signal at the radio frequency to produce a bandpass M-bit square wave signal; and

provide the bandpass M-bit square wave signal to an antenna for transmission.