Level de-multiplexed delta sigma modulator based transmitter
This specification discloses a level de-multiplexed DSM based transmitter and a method for providing the same. Broadly embodiments of the present specification enable wireless transmitters that are based on multi-level de-multiplexed DSM. A three-level de-multiplexed DSM based transmitter is disclosed as an example. More generally, the use of m-level de-multiplexed DSM is also taught, the specification thereby being enabling for broader applications to a person skilled in the art. At least one of the efficiency and linearity of transmitters can be enhanced as required for specific applications by a person of skill in the art in view of this specification and the teachings of its disclosed embodiments.
1. A level de-multiplexed Delta Sigma Modulator (DSM) based transmitter, comprising:
a. an m-level DSM unit, wherein m is an integer greater than or equal to 3, the DSM unit adapted to quantize an input signal into m−1 non-Zero quantization levels and a Zero level, the DSM unit further adapted to generate (m−1) de-multiplexed signal streams with substantially no time overlap between any two signal streams, each signal stream having a Zero-level component and a Non-zero component, the non-zero component corresponding to one of the (m−1) non-Zero quantization levels;
b. a signal up-conversion block, adapted to receive the (m−1) de-multiplexed signal streams from the m-level DSM unit and to frequency up-convert the (m−1) signal streams into (m−1) radio frequency (RF) signals; and
c. a signal amplification block adapted to receive the (m−1) RF signals, to amplify the (m−1) RF signals into (m−1) amplified signals and to combine the (m−1) amplified signals into an output signal.
2. The level de-multiplexed DSM based transmitter of claim 1 , wherein the m-level DSM unit is within a digital processing block further comprising a signal components separator adapted to receive a time-varying input signal and to extract components of the time-varying input signal based on a selected representation, a signal components interpolator adapted to receive the components of the time—varying input signal from the signal components separator, to perform oversampling on the component and to send the oversampled components to the DSM unit.
3. The level de-multiplexed DSM based transmitter of claim 1 , wherein within the m-level DSM unit the input signal is quantized by one of either (m−1) quantizers or one quantizer followed by (m−1) comparators.
4. The level de-multiplexed DSM based transmitter of claim 1 , wherein the signal up-conversion block comprises (m−1) bit level mappers (BLMs) adapted to receive the (m−1) de-multiplexed signal streams and to convert them to (m−1) baseband signals, and one of an (m−1) single-channel up-converters and an (m−1)-channel up-converter adapted to up-convert the (m−1) baseband signals to the (m−1) RF signals.
5. The level de-multiplexed DSM based transmitter of claim 1 , wherein the signal amplification block comprises (m−1) switching-mode amplifiers (SMPAs), each one of the (m−1) SMPAs adapted to receive and amplify one of the (m−1) RF signals.
6. The level de-multiplexed DSM based transmitter of claim 5 , wherein at least two of the (m−1) SMPAs of the signal amplification block are connected in back-to-back configuration.
7. The level de-multiplexed DSM based transmitter of claim 5 , wherein at least one of the (m−1) SMPAs of the signal amplification block is operated in saturation most of the time.
8. The level de-multiplexed DSM based transmitter of claim 5 , wherein at least one of the (m−1) SMPAs of the signal amplification block provides a saturated output power higher than that of at least another one of the (m−1) SMPAs of the signal amplification block.
9. The level de-multiplexed DSM based transmitter of claim 1 , wherein the transmitter is substantially linear.
10. The level de-multiplexed DSM based transmitter of claim 1 , further comprising a band pass filter connected at the output of the signal amplification block.