Pulse insertion systems and methods for polar modulation
View Patent ↗Systems and methods for bandwidth reduction in polar modulation systems are described. Detection of problematic signal transition paths may performed, and then, dependent on the signal path, a correction signal may be generated and added to the signal to improve system performance. In typical implementations, detection of problematic signal paths may be performed by determining whether the signal transitions through a particular region in the signal constellation, such as a region about the origin, or whether the signal instantaneous frequency exceeds a predetermined threshold, and then responsively generating the correction signal.
1. A method of bandwidth performance enhancement of a solar modulation transmitter comprising:
detecting entry of a transmit signal into a predetermined region in a signal constellation plane upon which said transmit signal is represented;
responsive to said detecting, combining a correction signal with the transmit signal to form a combined signal characterized by a combined signal trajectory positioned outside the predetermined region,
wherein the predetermined region is an annular region about the origin of the transmit signal constellation plane;
wherein said detecting comprises determining when the transmit signal instantaneous frequency exceeds a preset threshold;
wherein said determining comprises calculating a phase difference between samples of the transmit signal; comparing the phase difference to a preset value, and; signaling an event detection if the phase difference exceeds the preset value.
2. The method of claim 1 further comprising screening for a predetermined number of sequential event detections, and;
blocking said signaling of an event detection until the number of sequential event detections exceeds the predetermined number.
3. A method of bandwidth performance enhancement of a solar modulation transmitter comprising:
detecting entry of a transmit signal into a predetermined region in a signal constellation plane upon which said transmit signal is represented;
responsive to said detecting, combining a correction signal with the transmit signal to form a combined signal characterized by a combined signal trajectory positioned outside the predetermined region;
wherein said combining comprises scaling the correction signal; time delaying the transmit signal; determining an optimal insertion time, and; adding the scaled correction signal to the time delayed transmit signal at the optimal insertion time.
4. The method of claim 3 wherein said determining an optimal insertion time comprises detecting when the transmit signal instantaneous frequency exceeds a preset threshold.
5. The method of claim 4 wherein said determining an optimal insertion time further comprises determining a phase difference between samples of the transmit signal;
comparing the phase difference to a preset value, and;
signaling an optimal insertion time if the phase difference exceeds the preset value.
6. The method of claim 3 wherein said adding the scaled correction signal to the time delayed transmit signal at the optimal insertion time comprises adding the scaled correction signal to the transmit signal wherein the scaled correction signal is substantially orthogonal to the trajectory of the transmit signal at the optimal insertion time.
7. A system for bandwidth performance enhancement of a polar modulator comprising:
detection circuitry comprising a detection module for detecting entry of a transmit signal into a predetermined region in a signal constellation plane upon which said transmit signal is represented;
a signal correction module for combining a correction signal with the transmit signal to form a combined signal characterized by a combined signal trajectory positioned outside the predetermined region;
wherein the detection module comprises an event detection module; and
wherein the event detection module comprises a phase differentiator and a threshold detector, the threshold detector operative to trigger an event detection when the phase differentiator output exceeds a preset threshold.
8. A system for bandwidth performance enhancement of a polar modulator comprising:
detection circuitry comprising a detection module for detecting entry of a transmit signal into a predetermined region in a signal constellation plane upon which said transmit signal is represented;
a signal correction module for combining a correction signal with the transmit signal to form a combined signal characterized by a combined signal trajectory positioned outside the predetermined region
wherein the detection module comprises an event detection module and an event screener; and
wherein the event screener comprises cascaded unit delay modules and associated logic operative to output a signal when a preset number of unit delayed events have occurred.
9. The system of claim 8 wherein the signal correction module comprises a correction signal generator, a scaling factor generator, a time delay module, and a signal combiner.
10. The system of claim 9 wherein the correction signal generator comprises a unit normal pulse generator, a pulse scaler, and a pulse shaper.
11. The system of claim 9 wherein the scaling factor generator comprises an root mean square (RMS) approximator and a multiplier, the multiplier operative to multiply an RMS approximation of the transmit signal generated by the RMS approximator by a preset scaling factor.
12. The system of claim 9 wherein the time delay module comprises a shift register.
13. The system of claim 9 wherein the signal combiner comprises an adder wherein the adder is operative to combine a time delayed version of the transmit signal with the correction signal.