Modernized global navigation satellite system (GNSS) receivers and commercially viable consumer grade GNSS receivers
GNSS receivers and systems within such receivers use improvements to reduce memory usage while providing sufficient processing resources to receive and acquire and track E5 band GNSS signals directly (without attempting in one embodiment to receive L1 GNSS signals). Other aspects are also described.
1 . A system for processing GNSS signals in a GNSS receiver, said system comprising:
a radiofrequency analog to digital converter (ADC) configured to generate a digital representation of received GNSS signals;
a baseband sample memory to store the digital representation of the received GNSS signals as digitized GNSS sample data, the baseband sample memory configured to store an array of the digitized GNSS sample data in N2 rows and N1 columns, the digitized GNSS sample data in the array being stored in row order in the baseband sample memory and N2 being larger than N1, the row order containing the digitized GNSS sample data that was received over a time period that includes a first time period and a second time period such that a first row in the row order contains digitized GNSS sample data received during the first time period and a second row, which follows the first row in the row order, contains digitized GNSS sample data received during the second time period that follows, in time, the first time period, the baseband sample memory coupled to the radiofrequency ADC;
a set of arithmetic logic units (ALU) configured to perform discrete Fourier transform (DFT) operations, the set of ALUs coupled to the baseband sample memory, the set of ALUs configured to perform, in parallel and concurrently in time, N1 DFTs on the digitized GNSS sample data, wherein each of the N1 DFTs contains N2 points, from the digitized GNSS sample data, in the DFT and the outputs of the N1 DFTs are stored in a partial result sample array, and wherein the set of ALUs are configured to then perform N2 DFTs, each of the N2 DFTs containing N1 points from the partial result sample array, the N2 DFTs providing an output stored in an DFT result array that is arranged in column order.
2 . The system as in claim 1 , wherein the baseband sample memory is configured as a circular memory buffer that stores the array.
3 . The system as in claim 1 , wherein the N1 DFTs use the same operations and same program control instructions for the set of ALUs to operate on different data.
4 . The system as in claim 3 , wherein the N2 DFTs are performed consecutively over time and wherein the baseband sample memory stores more than one frame of pseudorandom GNSS codes which is more than 1 millisecond.
5 . The system as in claim 3 , wherein the N1 DFTs and the N2 DFTs use a decimation in time method and wherein N1 is one of the integer values: 5 or 10 or 20 or 40.
6 . The system as in claim 3 , wherein a change from row order to column order avoids a re-ordering algorithm, the change produced by a combination of the N1 DFTs followed by the N2 DFTs.
7 . The system as in claim 3 , wherein a GNSS code generator is configured to generate a GNSS PRN code which is processed with a set of DFTs on the GNSS PRN code to provide a code spectrum result data stored in a code spectrum memory in a column order, the code spectrum result data including GNSS PRN code data that is frequency and/or time shifted.
8 . The system as in claim 7 , wherein the set of ALUs is configured to multiply the code spectrum result data by the output stored in the DFT result array to produce a product array.
9 . The system as in claim 8 , wherein the set of ALUs is configured to perform an inverse DFT on the product array to correlate the received GNSS signals with the GNSS PRN code data.
10 . The system as in claim 9 , wherein the inverse DFT comprises: (1) in a first stage, N2 DFTs with conjugated inputs, each of the N2 DFTs containing N1 points, and (2) in a second stage that follows the first stage, N1 DFTs, each of the N1 DFTs containing N2 points.
11 . The system as in claim 7 , wherein the baseband sample memory is a dual port memory.
12 . The system as in claim 7 , wherein the GNSS code generator generates a pseudorandom noise code for each GNSS SV in view every millisecond when it is needed during an acquisition phase and does not store a generated pseudorandom noise code after it is used, and the generated pseudorandom noise code is used to generate the GNSS code spectrum.
13 . The system as in claim 12 wherein the GNSS code spectrum is aligned in place in memory in both frequency and phase to match code phase and frequency shift hypotheses associated with the received GNSS signals.
14 . The system as in claim 13 wherein the alignment is performed by CORDIC hardware.
15 . The system as in claim 1 , wherein the GNSS receiver receives and processes only GNSS signals in an L5 radio frequency (RF) band and does not use GNSS signals in an L1 RF band.
16 . The system as in claim 15 , wherein the GNSS receiver includes time domain correlators, and the time domain correlators are used in a tracking mode after GNSS signals have been acquired.
17 . The system as in claim 1 , wherein a code spectrum data for each of a first GNSS primary PRN code data and a second GNSS primary PRN code data are generated with a series of DFTs repeatedly during a time period while acquiring GNSS signal components that include the first GNSS primary PRN code data and the second GNSS primary PRN code data and wherein the code spectrum data includes GNSS PRN code data that is frequency and/or time shifted and wherein the time period is more than two milliseconds.
18 . The system as in claim 1 , wherein the GNSS receiver receives and processes GNSS signals in an L5 RF band using the set of ALUs, and also receives and processes GNSS signals in an L1 RF band.
19 . A system for processing GNSS signals in a GNSS receiver, the system comprising:
an analog to digital converter (ADC) to generate a digital representation of received GNSS signals;
a baseband sample memory to store the digital representation of the received GNSS signals, the baseband memory coupled to the ADC;
a GNSS processing system coupled to the baseband sample memory to process the digital representation of the received GNSS signals in an array processing system, the GNSS processing system configured to acquire up to four GNSS signal components of a GNSS signal by non-coherently integrating, over a period of time, the up to four GNSS signal components from a single GNSS SV, the array processing system being in an acquisition engine in the GNSS processing system and the array processing system receiving GNSS sample data from the baseband memory and the GNSS sample data being formatted in a two dimensional (N1 by N2) array having a plurality of rows and a plurality of columns, wherein the array processing system processes the GNSS sample data in the two dimensional array to acquire GNSS signals using a series of DFTs that comprise a first set of N1 DFTs, each having N2 points, followed in time by a second set of N2 DFTs, each having N1 points, wherein N2 is greater than N1.
20 . The system as in claim 19 , wherein the array processing system comprises processing logic that performs the series of DFTs using a decimation in time algorithm followed by a set of inverse DFTs, and wherein the GNSS sample data in the two dimensional array is slightly more than 1 millisecond of sample GNSS signals.
21 . The system as in claim 20 , wherein an output from the array processing system provides frequency and GNSS SV identifiers for storage in hypothesis memory to integrate hypotheses for GNSS signals to acquire the GNSS signals.
22 . The system as in claim 19 , wherein the array processing system receives the GNSS sample data in a first order and produces an output in a second order that is different than the first order, and wherein the first order is one of a row order or a column order in the two dimensional array, and wherein the first order is based on the time of receipt of the GNSS sample data.
23 . The system as in claim 19 , wherein the N1 DFTs use the same operations and same program control instructions to operate on different data, and the N1 DFTs are performed in parallel and concurrently.
24 . The system as in claim 19 , wherein a GNSS code generator in the GNSS processing system is configured to generate a GNSS PRN code which is processed with a set of DFTs on the GNSS PRN code to provide a code spectrum result data stored in a code spectrum memory, the code spectrum result data including GNSS PRN code data that is frequency and/or time shifted, and wherein the GNSS processing system is configured to multiply the code spectrum result data by an output from the series of DFTs to produce a product array, and wherein the GNSS processing system is configured to perform an inverse DFT on the product array to correlate the received GNSS signals with the GNSS PRN code.
25 . The system as in claim 24 , wherein the code spectrum result data is aligned in place in memory in both frequency and phase to match code phase and frequency shift hypotheses associated with the received GNSS signals.
26 . The system as in claim 19 , wherein the GNSS receiver receives and processes only GNSS signals in an L5 radio frequency (RF) band and does not use GNSS signals in an L1 RF band.
27 . The system as in claim 26 , wherein the GNSS receiver includes time domain correlators, and the time domain correlators are used in a tracking mode after GNSS signals have been acquired.
28 . The system as in claim 19 , wherein a code spectrum data for each of a first GNSS primary PRN code data and a second GNSS primary PRN code data are generated repeatedly, in the GNSS receiver, during a time period while acquiring GNSS signal components that include the first GNSS primary PRN code data and the second GNSS primary PRN code data and wherein the code spectrum data includes GNSS PRN code data that is frequency shifted and/or time shifted and wherein the time period is more than two milliseconds.
29 . The system as in claim 19 , wherein the GNSS receiver receives and processes GNSS signals in an L5 RF band using the set of ALUs, and also receives and processes GNSS signals in an L1 RF band.