Upsampling/interpolation and time alignment mechanism utilizing injection of high frequency noise

A method of increasing the sampling rate of a discrete-time input sample stream, said method comprising the steps of:

• differentiating said input samples to generate differentiated samples therefrom;
• upsampling and interpolating said differentiated samples to generate interpolated samples therefrom;
• delaying said interpolated samples by a predetermined duration to generate delayed samples therefrom;
• and
• integrating said delayed samples to generate upsampled output samples therefrom.

A multi-rate digital filter, comprising:

• a differentiator operative to receive a discrete-time input sample stream and to generate differentiated samples therefrom;
• one or more cascaded upsampling units coupled to said differentiator, each upsampling unit comprising:
• an upsampler operative to upsample and interpolate samples to generate interpolated samples therefrom;
• and
• an integrator operative to integrate the output of said one or more cascaded upsampling units to generate upsampled output samples therefrom.

A multi-rate digital filter, comprising:

• a differentiator operative to receive a discrete-time input sample stream and to generate differentiated samples therefrom;
• one or more cascaded upsampling units coupled to said differentiator, each upsampling unit comprising:
• an upsampler operative to upsample and interpolate samples to generate interpolated samples therefrom;
• a delay alignment unit operative to delay said interpolated samples by a predetermined duration to generate delayed samples therefrom;
• and
• an integrator operative to integrate the output of said one or more cascaded upsampling units to generate upsampled output samples therefrom.

A polar radio frequency (RF) transmitter (TX), comprising:

• means for generating a discrete-time frequency command word (FCW) signal and a discrete-time amplitude command word (ACW) signal in accordance with input TX IQ data samples;
• a first multi-rate digital filter operative to increase the sampling rate of said FCW signal by upsampling and interpolating said FCW signal to generate an upsampled FCW signal therefrom;
• a second multi-rate digital filter operative to increase the sampling rate of said ACW signal by upsampling and interpolating said ACW signal to generate an upsampled ACW signal therefrom;
• a frequency synthesizer operative to generate an RF signal having a frequency in accordance with a frequency reference input and said upsampled FCW signal;
• and
• a digital power amplifier (DPA) operative to receive said RF signal and to generate a modulated RF output signal in proportion to said upsampled ACW signal.

A single chip radio, comprising:

• a phase locked loop (PLL);
• a transmitter coupled to said phase locked loop, said transmitter comprising:
• means for generating a discrete-time frequency command word (FCW) signal and a discrete-time amplitude command word (ACW) signal in accordance with input transmitter IQ data samples;
• a first multi-rate digital filter operative to increase the sampling rate of said FCW signal by upsampling and interpolating said FCW signal to generate a filtered FCW signal therefrom;
• a second multi-rate digital filter operative to increase the sampling rate of said ACW signal by upsampling and interpolating said ACW signal to generate a filtered ACW signal therefrom;
• a frequency synthesizer operative to generate an RF signal having a frequency in accordance with a frequency reference input and said filtered FCW signal;
• a digital power amplifier (DPA) operative to receive said RF signal and to generate a modulated RF output signal in proportion to said filtered amplitude command signal;
• a receiver coupled to said phase locked loop;
• and
• a baseband processor coupled to said transmitter and said receiver.