Frequency planning for digital power amplifier
Systems and techniques relating to wireless communication devices and digital power amplifiers include, according to an aspect, a device including: modulation circuitry of a radio frequency transmitter having a local oscillator frequency; a digital power amplifier coupled with the modulation circuitry; and a clock input coupled with the digital power amplifier; wherein the clock input provides a clock signal to the digital amplifier at a sampling clock frequency; and wherein the local oscillator frequency is an integer multiple of the sampling clock frequency.
1. A device comprising:
modulation circuitry of a radio frequency transmitter having a local oscillator frequency receivable on a local oscillator input from an oscillator source;
a digital power amplifier coupled with the modulation circuitry; and
a clock input coupled with the digital power amplifier, the clock input being separate from the local oscillator input, the clock input configured to couple with a clock source that is different from the oscillator source;
wherein the clock input provides a clock signal to separate segments of the digital power amplifier at a sampling clock frequency; and
wherein the local oscillator frequency is an integer multiple of the sampling clock frequency.
2. The device of claim 1 , wherein the local oscillator frequency is equal to the sampling clock frequency.
3. The device of claim 1 , comprising one or more antennas.
4. The device of claim 3 , wherein the digital power amplifier is coupled directly to the one or more antennas.
5. The device of claim 4 , wherein the local oscillator frequency is two times the sampling clock frequency.
6. The device of claim 5 , wherein the device is a wireless communications device configured to transmit a 5 GHz WiFi signal using the modulation circuitry, the digital power amplifier, and the one or more antennas.
7. A device of claim 3 , comprising:
modulation circuitry of a radio frequency transmitter having a local oscillator frequency;
a digital power amplifier coupled with the modulation circuitry;
a clock input coupled with the digital power amplifier, wherein the clock input provides a clock signal to the digital power amplifier at a sampling clock frequency, and wherein the local oscillator frequency is an integer multiple of the sampling clock frequency;
one or more antennas; and
an anti-alias filter coupled between the digital power amplifier and the one or more antennas, wherein the anti-alias filter is designed to filter out one or more alias signals in accordance with the local oscillator frequency and the sampling clock frequency.
8. The device of claim 7 , wherein the device is a System on Chip (SoC) comprising:
processor electronics;
transceiver electronics coupled with the processor electronics; and
a single clock source that distributes a common clock signal to at least one processing unit of the processor electronics and to the clock input of the digital power amplifier.
9. The device of claim 7 , wherein the digital power amplifier is a Polar digital power amplifier.
10. The device of claim 1 , wherein the digital power amplifier is an IQ/Cartesian digital power amplifier.
11. A method comprising:
upconverting a baseband signal using a carrier frequency for wireless transmission to generate a transmission signal;
feeding the transmission signal to multiple, respective segments of a digital power amplifier;
sampling the transmission signal in selected ones of the segments of the digital power amplifier using a clock frequency that is harmonized with the carrier frequency;
amplifying the sampled transmission signal in the selected ones of the segments of the digital power amplifier to generate amplified output signals; and
combining the amplified output signals for radio frequency transmission.
12. The method of claim 11 , wherein the sampling comprises sampling using a clock frequency that is equal to the carrier frequency.
13. The method of claim 11 , comprising:
generating the baseband signal in accordance with a wireless communication standard; and
transmitting the combined output signals using an antenna in accordance with the wireless communication standard.
14. The method of claim 13 , comprising feeding the combined output signals directly to the antenna, using circuit parasitics to effect filtering of alias signals out of the combined output signals before transmission.
15. The method of claim 13 , wherein the sampling comprises sampling using a clock frequency that is one half of the carrier frequency.
16. The method of claim 15 , wherein the wireless communication standard is a 5 GHz WiFi standard.
17. The method of claim 11 , comprising filtering alias signals out of the combined output signals before transmission using an anti-alias filter designed in accordance with the clock frequency and the carrier frequency.
18. The method of claim 11 , comprising distributing a single clock signal to both (i) a baseband processing unit for generating the baseband signal and (ii) the digital power amplifier for the sampling.
19. The method of claim 11 , comprising phase modulating the transmission signal before feeding the transmission signal to the multiple, respective segments of the digital power amplifier.
20. The method of claim 11 , wherein the feeding comprises feeding the transmission signal to separate I and Q banks of the digital power amplifier.