Systems and methods for performing phase tracking within an ADC-based tuner
View Patent ↗Systems and methods for performing phase tracking scheme for an Analog to Digital converter based tuner. In many embodiments, a phase tracking scheme is used that includes a phase locked loop that corrects the phase of the output signals and an amplitude modulation compensator that modulates the amplitude of the output digital signals to compensate for phase noise based upon the received output digital signals.
1. An Analog to Digital Converter (ADC) based tuner comprising:
a low noise amplifier that amplifies a received analog signal;
an ADC that receives the received analog signal and converts the received analog signal to a received digital signal;
a Phase Locked Loop (PLL) that provides a clock signal to the ADC;
a channelizer that receives the received digital signal from the high-speed ADC and performs mixing and filtering operations on the received digital signals in the digital domain;
a digital signal mixer that receives the received digital signal from the channelizer and mixes the received digital signals with a phase adjustment estimation signal to provide an output digital signal;
a digital phase lock loop that receives the output digital signal from the digital signal mixer and provides the phase adjustment estimation signal to the digital signal mixer based upon the output digital signal; and
an amplitude modulation compensator that receives the output digital signal from the digital signal mixer and modulates the amplitude of the output digital signal to compensate for amplitude modulation from phase noise, including phase noise due to the PLL, based upon the received output digital signal wherein the amplitude modulation compensator comprises:
an amplifier that receives the output digital signal from the digital signal mixer and amplifies the output digital signal based upon a gain adjustment signal,
a phase error detector that receives the output digital signal from the amplifier and outputs an amplitude detection error signal, and
a gain adjustment loop that receives the amplitude detection error signal from the phase error detector and generates the gain adjustment signal based upon the amplitude detection error signal.
2. The phase tracking scheme of claim 1 wherein the gain adjustment loop comprises a first order loop.
3. The phase tracking scheme of claim 2 wherein the first order loop comprises an multiplier and an accumulator.
4. The phase tracking scheme of claim 1 wherein the gain adjustment loop comprises a second order loop.
5. The phase tracking scheme of claim 4 wherein the second order loop comprises:
a first multiplier that multiplies the amplitude detection error with a linear coefficient to provide a first amplitude adjustment error signal;
a second multiplier that multiplies the amplitude detection error with an integral coefficient to provide a current intermediate second amplitude adjustment error signal;
a first accumulator that receives the current intermediate second amplitude adjustment signal and adds a previous intermediate second amplitude adjustment error signal to the current intermediate second amplitude adjustment error signal to produce a second amplitude adjustment error signal;
an adder that adds the first amplitude adjustment error signal and the second amplitude adjustment error signal to provide a current intermediate gain adjustment signal; and
a second accumulator that receives the current intermediate gain adjustment signal from the adder and adds a previous intermediate gain adjustment signal to the current intermediate gain adjustment signal to provide the gain adjustment signal.
6. The phase tracking scheme of claim 1 wherein the phase error detector also provides a phase detection error signal of the output digital signals and the phase lock loop comprises:
a loop filter that receives the phase detection error signal from the phase error detector and outputs a current intermediate phase corrected signal based upon the phase detection error signal;
an accumulator that receives the current intermediate phase corrected signal from the loop filter and adds a previous intermediate phase corrected signal to the current intermediate phase corrected signal to provide a phase corrected signal; and
a direct digital frequency synthesizer that receives the phase corrected signal from the phase accumulator and provides the phase correction signal based upon the phase corrected signal.
7. A method of performing phase tracking within an Analog to Digital Converter (ADC) based tuner comprising:
receiving a digital signal from an ADC based tuner;
mixing the received digital signal with a phase adjustment estimation signal to provide an output digital signal;
generating the phase adjustment information signal for mixing with the received digital signal based upon the output digital signal; and
modulating the amplitude of the output digital signal to compensate for amplitude modulation from phase noise based upon the received output digital signals, wherein the modulating of the amplitude of the output signal comprises:
amplifying the output digital signal based upon a gain adjustment signal,
determining an amplitude detection error signal from the output digital signal, and
generating the gain adjustment signal based upon the amplitude detection error signal.
8. The method of claim 7 wherein the generating of the gain adjustment signal comprises:
multiplying the amplitude detection error signal with a linear coefficient to provide a first amplitude phase adjustment error signal;
multiplying the amplitude detection error signal with an integral coefficient to provide a current intermediate second amplitude adjustment error signal;
adding a previous intermediate second amplitude adjustment error signal to the current intermediate second amplitude adjustment error signal to produce the second amplitude adjustment error signal;
adding the first amplitude adjustment error signal and the second amplitude adjustment error signal to provide a current intermediate gain adjustment signal; and
adding a previous intermediate gain adjustment signal to the current intermediate gain signal to provide the gain adjustment signal.
9. The method of claim 7 wherein the generating of the phase correction signal comprises:
determining a phase detection error signal from the output digital signals;
generating a current intermediate phase corrected signal based upon the phase detection error signal;
adding a previous intermediate phase corrected signal to the current intermediate phase corrected signal to provide a phase corrected signal; and
providing the phase adjustment estimation signal based upon the phase corrected signal.
10. The method of claim 7 further comprising:
receiving an analog signal; and
converting the received analog signal to a received digital signal using an ADC that receives a clock signal from a Phase Locked Loop (PLL) wherein the PLL introduces phase noise that modulates the digital signal.