GPS World, February 2014
Ubiquitous Positioning SIGNAL PROCESSING array approach presented here cannot match the performance of CRPA with its careful design antenna calibration and precise knowledge of relative location of phase centers of individual elements However it can still offer a significant interference protection to networked GNSS users The multi platform phased array implements a cascaded space time adaptive processing STAP as illustrated in FIGURE 4 DVFDGHG 67 3 LPSOHPHQWV WHPSRUDO OWHULQJ DW D SUH FRUUHODWLRQ VWDJH ZKLOH VSDWLDO OWHULQJ LQ D IRUP RI WKH GLJLWDO EHDP IRUPLQJ RU LV FDUULHG out at post correlation Cascaded STAP is implemented instead of joint STAP formulation to remove the need to exchange raw signal samples which is necessary when LV DSSOLHG DW SUH FRUUHODWLRQ DQG VXSSRUW D QRYHO DSSURDFK WKDW GRHV QRW UHTXLUH SUHFLVH WKDW LV VXE centimeter to centimeter level knowledge of relative position and clock states between network nodes described later Signal samples are still exchanged for the estimation of signal covariance PDWULFHV WKDW DUH UHTXLUHG IRU WKH FRPSXWDWLRQ RI WHPSRUDO DQG VSDWLDO ZHLJKWV RZHYHU WKH VDPSOH H FKDQJH UDWH LV UHGXFHG VLJQL FDQWO DV FRPSDUHG WR WKH joint STAP for example only 100 samples are currently being exchanged out of the total of 5000 samples over a 1 ms signal accumulation interval 7KH XVHV WKH 0LQLPXP 9DULDQFH LVWRUWLRQ OHVV 5HVSRQVH 09 5 IRUPXODWLRQ IRU WKH FRPSXWDWLRQ RI VSDWLDO ZHLJKW YHFWRU 09 5 FRQVWUDLQV power minimization by the undisturbed signal reception in the satellites direction 1 ZKHUH ĭ LV WKH PXOWL QRGH VLJQDO FRYDULDQFH PDWUL WKDW LV FRPSXWHG EDVHG RQ WHPSRUDO OWHU RXWSXWV VXSHUVFULSW GHQRWHV WKH WUDQVSRVH DQG FRPSOH FRQMXJDWH RSHUDWLRQ DQG Ș LV WKH VWHHULQJ YHFWRU WKDW FRPSHQVDWHV IRU SKDVH GLIIHUHQFHV between array elements for the signal coming from the satellites direction 2 Q X LV WKH UHFHLYHU WR VDWHOOLWH OLQH RI VLJKW 26 XQLW YHFWRU UP LV WKH UHODWLYH SRVLWLRQ YHFWRU EHWZHHQ SKDVH FHQWHUV RI WKH PWK QRGH DQG 0867 5 LV WKH YHFWRU GRW SURGXFW DQG LV WKH FDUULHU ZDYHOHQJWK ROORZLQJ FRPSXWDWLRQ RI ZHLJKW PXOWL QRGH PV 36 VLJQDO functions are combined 4 where is the complex 1 ms accumulated signal amplitude of the mth node for the l p bin of the code carrier open loop tracking search space The result is further accumulated for example over 20 ms and then applied for the open loop estimation of signal parameters 2QH RI WKH PRVW FKDOOHQJLQJ UHTXLUHPHQWV RI WKH FODVVLFDO 09 5 EDVHG is the necessity to estimate relative multi node position and clock states at a FHQWLPHWHU OHYHO RI DFFXUDF 7R HOLPLQDWH WKLV UHTXLUHPHQW DQG H WHQG SRWHQWLDO DSSOLFDWLRQV RI PXOWL QRGH SKDVHG DUUD V WKH ZDV PRGL HG DV LOOXVWUDWHG in FIGURE 5 For radio interference weve got your back Download your free copy of our solutions whitepaper www septentrio com interference Versatile OEM Receivers for Demanding Applications www septentrio com www gpsworld com February 2014 GPS World 31
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