System for frequency domain receive channelization
A phased array antenna (PAA) comprising thousands of antennas acquires radio frequency analog signals that are processed by analog to digital converters to generate time domain raw samples. A digital beamformer (DBF) connected to a subset of these antennas processes the raw samples into frequency domain (FD) samples that are processed by a beamformer algorithm. In one implementation the beamformed FD samples are sent to a processor that filters samples into arbitrary frequency ranges associated with arbitrary channels. The filtered samples are then converted back to time domain (TD) channel samples that are then processed by a demodulator to recover data. In another implementation the DBF performs the filtering and conversion to TD, with the TD channel samples sent to a demodulator to recover data. This system supports reception and processing of analog waveforms of various bandwidths within an overall receive passband acquired by a PAA.
1 . A system comprising:
a phased array antenna comprising a plurality of antennas;
a plurality of radio frequency (RF) front ends, wherein a first RF front end of the plurality of RF front ends comprises:
an RF input connected to a subset of the plurality of antennas, and
an analog output;
a plurality of analog-to-digital converters (ADCs), wherein a first ADC of the plurality of ADCs comprises:
an analog input that is connected to the analog output of the first RF front end, and
a first digital output that sends raw samples acquired at a sample rate, wherein the raw samples are in a time domain (TD);
a plurality of digital beamformers (DBFs), wherein a first DBF of the plurality of DBFs comprises:
a first digital input that receives the raw samples from an ADC;
a discrete Fourier transform (DFT) module that implements a DFT algorithm to convert the raw samples from the TD to frequency domain (FD) raw samples;
a first beamformer module that implements a first beamforming algorithm to process the FD raw samples to generate first beamformed FD samples; and
a second digital output that sends second beamformed samples comprising one of (i) the first beamformed FD samples or (ii) data based on the first beamformed FD samples; and
a processor comprising:
a second digital input that receives the second beamformed samples;
one or more modules to process the second beamformed samples and provide first TD channel samples comprising samples associated with a first channel that are represented in the time domain;
a demodulator to receive the first TD channel samples and generate first data; and
a third digital output that sends the first data.
2 . The system of claim 1 , the first beamforming algorithm comprising a delay and sum algorithm that changes one or more of a phase or amplitude of a sample.
3 . The system of claim 1 , the processor further comprising:
a frequency filter module comprising one or more frequency filtering algorithms to process the second beamformed samples to generate filtered samples, wherein the filtered samples are associated with the first channel and are in the frequency domain; and
an Inverse DFT (IDFT) module that implements an IDFT algorithm to convert the filtered samples from the frequency domain to the first TD channel samples.
4 . The system of claim 3 , wherein the IDFT module utilizes a first set of bins, each bin associated with a specified range of frequencies, and further wherein the first set of bins comprises:
a lower guard bin associated with samples having a frequency between a minimum frequency and a first frequency of an analog signal;
a plurality of bins, wherein each bin is associated with samples within a specified frequency range;
a supplemental bin having a frequency width that is less than or equal to a maximum doppler shift associated with operation of the system; and
an upper guard bin associated with samples having a frequency between a second frequency and a maximum frequency of the analog signal.
5 . The system of claim 1 , the first DBF further comprising:
a frequency filter module comprising one or more frequency filtering algorithms to process the second beamformed samples to generate filtered samples, wherein the filtered samples are associated with the first channel; and
an IDFT module that implements an IDFT algorithm to convert the filtered samples from the FD to the first TD channel samples; and
wherein:
the second beamformed samples consist of the first TD channel samples.
6 . The system of claim 5 , wherein the IDFT module utilizes a first set of bins, each bin associated with a specified range of frequencies, and further wherein the first set of bins comprises:
a lower guard bin associated with samples having a frequency between a minimum frequency and a first frequency of an analog signal;
a plurality of bins, wherein each bin is associated with samples within a specified frequency range;
a supplemental bin having a frequency width that is less than or equal to a maximum doppler shift associated with operation of the system; and
an upper guard bin associated with samples having a frequency between a second frequency and a maximum frequency of the analog signal.
7 . The system of claim 1 , the processor further comprising:
the one or more modules to process the second beamformed samples and provide second TD channel samples comprising samples associated with a second channel that are represented in the time domain, wherein:
the first channel has a first bandwidth and the second channel has a second bandwidth that is a rational number multiple of the first bandwidth.
8 . A computer-implemented method comprising:
receiving at a first digital beamformer (DBF), raw samples acquired at a sample rate, wherein the raw samples are representative of one or more analog signals received using a phased array antenna in a time domain (TD);
processing at the first DBF the raw samples using a discrete Fourier transform (DFT) algorithm to generate frequency domain (FD) raw samples;
processing at the first DBF the FD raw samples using a first beamforming algorithm to generate first beamformed FD samples;
determining, at the first DBF, second beamformed samples comprising one of (i) the first beamformed FD samples or (ii) data based on the first beamformed FD samples;
processing at a first processor the second beamformed samples to provide first TD channel samples comprising samples associated with a first channel that are represented in the time domain;
demodulating the first TD channel samples to generate first data that is associated with the first channel; and
sending the first data.
9 . The method of claim 8 , wherein the first beamforming algorithm comprises a delay and sum algorithm that changes one or more of a phase or amplitude of a sample.
10 . The method of claim 8 , wherein the second beamformed samples comprise the first beamformed FD samples; and
processing at the first processor the first beamformed FD samples using one or more frequency filtering algorithms to generate filtered samples, wherein the filtered samples are associated with the first channel and are in the frequency domain; and
processing at the first processor the filtered samples using an Inverse DFT (IDFT) algorithm to convert the filtered samples from the frequency domain to the first TD channel samples.
11 . The method of claim 10 , wherein the IDFT algorithm utilizes a first set of bins, each bin associated with a specified range of frequencies, and further wherein the first set of bins comprises:
a lower guard bin associated with samples having a frequency between a minimum frequency and a first frequency of an analog signal;
a plurality of bins, wherein each bin is associated with samples within a specified frequency range;
a supplemental bin having a frequency width that is less than or equal to a maximum doppler shift associated with operation; and
an upper guard bin associated with samples having a frequency between a second frequency and a maximum frequency of the analog signal.
12 . The method of claim 8 , further comprising:
processing at the first DBF the first beamformed FD samples using one or more frequency filtering algorithms to generate filtered samples, wherein the filtered samples are associated with the first channel and are in the frequency domain; and
processing at the first DBF the filtered samples using an Inverse DFT (IDFT) algorithm to convert the filtered samples from the frequency domain to the first TD channel samples; and
wherein:
the second beamformed samples consist of the first TD channel samples.
13 . The method of claim 12 , wherein the IDFT algorithm utilizes a first set of bins, each bin associated with a specified range of frequencies, and further wherein the first set of bins comprises:
a lower guard bin associated with samples having a frequency between a minimum frequency and a first frequency of an analog signal;
a plurality of bins, wherein each bin is associated with samples within a specified frequency range;
a supplemental bin having a frequency width that is less than or equal to a maximum doppler shift associated with operation; and
an upper guard bin associated with samples having a frequency between a second frequency and a maximum frequency of the analog signal.
14 . The method of claim 8 , further comprising:
processing at the first processor the second beamformed samples to provide second TD channel samples comprising samples associated with a second channel that are represented in the time domain wherein:
the first channel has a first bandwidth and the second channel has a second bandwidth that is a rational number multiple of the first bandwidth.
15 . A system comprising:
a plurality of digital beamformers (DBFs), wherein a first DBF of the plurality of DBFs comprises:
a first digital input that receives raw samples from one or more analog-to-digital converters (ADCs), wherein the raw samples are time domain (TD) representations of analog signals acquired by one or more antennas of a phased array antenna;
a Discrete Fourier Transform (DFT) module that implements a DFT algorithm to convert the raw samples from the TD to frequency domain (FD) raw samples;
a first beamformer module that implements a first beamforming algorithm to process the FD raw samples to generate first beamformed FD samples; and
a first digital output that sends second beamformed samples comprising one of (i) the first beamformed FD samples or (ii) data based on the first beamformed FD samples; and
a processor comprising:
a second digital input that receives the second beamformed samples;
one or more modules to process the second beamformed samples and provide first TD channel samples comprising samples associated with a first channel that are represented in the time domain;
a demodulator to receive the first TD channel samples and generate first data; and
a second digital output that sends the first data.
16 . The system of claim 15 , the first beamforming algorithm comprising a delay and sum algorithm that changes one or more of a phase or amplitude of a sample.
17 . The system of claim 15 , the processor further comprising:
a frequency filter module comprising one or more frequency filtering algorithms to process the second beamformed samples to generate filtered samples, wherein the filtered samples are associated with the first channel and are in the frequency domain; and
an Inverse DFT (IDFT) module that implements an IDFT algorithm to convert the filtered samples from the frequency domain to the first TD channel samples.
18 . The system of claim 17 , wherein the IDFT module utilizes a first set of bins, each bin associated with a specified range of frequencies, and further wherein the first set of bins comprises:
a lower guard bin associated with samples having a frequency between a minimum frequency and a first frequency of an analog signal;
a plurality of bins, wherein each bin is associated with samples within a specified frequency range;
a supplemental bin having a frequency width that is less than or equal to a maximum doppler shift associated with operation of the system; and
an upper guard bin associated with samples having a frequency between a second frequency and a maximum frequency of the analog signal.
19 . The system of claim 15 , the first DBF further comprising:
a frequency filter module comprising one or more frequency filtering algorithms to process the second beamformed samples to generate filtered samples, wherein the filtered samples are associated with the first channel; and
an Inverse DFT (IDFT) module that implements an IDFT algorithm to convert the filtered samples from the FD to the first TD channel samples; and
wherein:
the second beamformed samples consist of the first TD channel samples.
20 . The system of claim 15 , the processor further comprising:
the one or more modules to process the second beamformed samples and provide second TD channel samples comprising samples associated with a second channel that are represented in the time domain, wherein:
the first channel has a first bandwidth and the second channel has a second bandwidth that is a rational number multiple of the first bandwidth.