(Regular Paper) 21 5, 2016 9 (JBE Vol. 21, No. 5, September 2016) http://dx.doi.org/10.5909/jbe.2016.21.5.803 ISSN 2287-9137 (Online) ISSN 1226-7953 (Print) GNSS RF a), a) Design and Performance of a Direct RF Sampling Receiver for Simultaneous Reception of Multiband GNSS Signals Jong-Won Choi a) and Bo-Seok Seo a) GNSS(global navigation satellite system) RF(radio frequency) RF. RF IF(intermediate frequency) AD(analog to digital) IF, (mixer) AD. IF AD.. AD,,. GPS L1, GLONASS G1 G2 GNSS RF. AD. Abstract In this paper, we design a direct radio frequency (RF) sampling receiver for multiband GNSS signals and demonstrate its performance. The direct RF sampling is a technique that does not use an analog mixer, but samples the passband signal directly, and all receiver processes are done in digital domain, whereas the conventional intermediate frequency (IF) receiver samples the IF band signals. In contrast to the IF sampling receiver, the RF sampling receiver is less complex in hardware, reconfigurable, and simultaneously converts multiband signals to digital signals with an analog-to-digital (AD) converter. The reconfigurability and simultaneous reception are very important in military applications where rapid change to other system is needed when a system is jammed by an enemy. For simultaneous reception of multiband signals, the sampling frequency should be selected with caution by considering the carrier frequencies, bandwidths, desired intermediate frequencies, and guard bands. In this paper, we select a sampling frequency and design a direct RF sampling receiver to receive multiband global navigation satellite system (GNSS) signals such as GPS L1, GLONASS G1 and G2 signals. The receiver is implemented with a commercial AD converter and software. The receiver performance is demonstrated by receiving the real signals. Keyword : GNSS, GPS, GLONASS, direct RF sampling, multiband receiver
(JBE Vol. 21, No. 5, September 2016). SDR(software defined radio) [1]. SDR,,. [1]. SDR (cognitive radio) [2], SIGINT (signal intelligence) [3]. SDR AD(analog-to-digital). (mixer) 0 (intermediate frequency: IF) Nyquist 2 [4]. RF(radio frequency) RF SDR. RF SDR, AD RF AD. a) (Department of Electronics Engineering, Chungbuk National University) Corresponding Author : (Bo-Seok Seo) E-mail: boseok@cbnu.ac.kr Tel: +82-43-261-3267 ORCID: http://orcid.org/0000-0002-1610-3667 2015,. Manuscript received June 21, 2016; Revised August 30, 2016; Accepted August 30, 2016. 3~4 GHz AD [5]. 1 RF 1/3 [6]. RF 2 RF 2 [7].. [7]. RF GNSS(global navigation satellite system) [7]. GNSS GPS(global positioning system), GLONASS, GALILEO, Beidou. GNSS L1, L2, L5 [8]. GNSS. GNSS (jamming) [8]. RF... GNSS IF [9].. AD. RF AD AD. GNSS
[10] GNSS RF GPS L1 C/A P L3. [11] GNSS IF GPS L1 Beidou B1. [12] GPS Galileo SDR IF Galileo. [13] Beidou, GPS, Galileo GNSS IF. [14] GNSS 5 RF GPS. [15], RF GPS., RF. [16] GNSS RF. GPS L1 GLONASS G1, G2 RF AD. [16] AD,, AD.,. 2 RF, 3 RF. 4 L1 G1, G2, 5.. RF RF. 1 (filtering). (low noise amplifier: LNA) AD. FPGA, DSP, PC. RF AD.. 1. ( ). (alias). RF ( ). [4]., RF. RF, RF. (1) RF,.,, (sample rate) (interpolation) (decimation),,
(JBE Vol. 21, No. 5, September 2016). IF 4. I-Q I-Q. RF 0 IF, IF. IF 4. 1 IF [7].,. IF (digital down conversion: DDC). 0Hz. 0Hz, Nyquist. [7]. AD. [7].,. (1), (3), (4). 2. RF (aliasing noise).,.....,. AD, AD. AD,. 4. DDC (interpolation) (decimation) (sample rate) 4..
. GNSS RF RF. GNSS RF. GNSS GPS L1, GLONASS G1, G2. GNSS RF 1. AD, RF, IF. 273ms AD PC PC. GNSS IF. 1. LNA. AD. Novatel GNSS GPS- 701-GGL. L1 G1 80MHz, G2 40MHz, LNA. LNA GPSNetworking WNLA20RPDC 49dB. 1.1GHz 1.7GHz L1, G1 G2. AD TI AD ADC12J4000EVM TSW14J56. AD 3GHz 4GHz. 2. AD AD 2,. 1 GPS L1, GLONASS G1, G2. GLONASS FDMA(frequency division multiple access). G1 1602MHz -7 6 14. 562.5kHz 1598.0625MHz 1605.375MHz. G2 1. GNSS RF Fig. 1. Structure of the direct RF sampling receiver for multiband GNSS signals
(JBE Vol. 21, No. 5, September 2016) -7 6 G1 14, 437.5kHz 1246 MHz 1242.9375MHz 1248.625MHz.. 2 (1) ~ (4) 1 ~ 2 GHz.. TI, (1) ~ (4) 1966.08MHz. 3. RF 3 RF. RF AD IF. 3 3 BPF. 1. GPS L1, GLONASS G1 G2 Table 1. Specification of GPS L1, GLONASS G1 and G2 signals System Signal Modulation Chip rate (Mcps) Data rate (bps) Bandwidth Carrier frequency GPS L1 C/A CDMA/BPSK 1.023 50 2.046 1575.42 GLONASS G1 FDMA/SS/BPSK 0.511 50 8.4375 1598.0625 ~ 1605.375 G2 FDMA/SS/BPSK 0.511 50 6.5625 1242.9375 ~ 1248.625 2. GPS L1, GLONASS G1, G2 RF Fig. 2. Allowable sampling frequency ranges for direct RF sampling of GPS L1, GLONASS G1 and G2 signals
3. RF Fig. 3. Structure of the digital RF signal processing. 2. 2. BPF Table 2. Center frequencies and bandwidths of the anti-aliasing BPFs (a) Filter Center frequency Bandwidth Passband signal BPF1 390.66 10 L1 BPF2 364.08 20 G1 BPF3 720.08 20 G2 GPS L1 C/A 2.046MHz. ( ( )/() Q ). 390.66MHz 10MHz. 8.4375MHz G1 364.08MHz 20MHz BPF, 6.5625MHz G2 720.08 MHz 20MHz BPF. 4 (b) (c) 4. (a) GPS L1, (b) GLONASS G1, (c) G2 1 Fig. 4. The frequency responses of the anti-aliasing bandpass filters for (a) GPS L1, (b) GLONASS G1 and (c) G2 signals. 9:1 218.4533MHz, 1/9 3.
(JBE Vol. 21, No. 5, September 2016) (a) (b) 5. (a) RF (b) Fig. 5. Spectrums of the signals (a) after AD conversion, and (b) after decimation 3. 1 9:1 Table 3. Intermediate frequencies after 9:1 decimation Signal before decimation after decimation L1 390.66 46.2469 G1 364.08 72.8269 G2 720.08 64.7198 5. 1 IF 0Hz DDC. DDC. L1. 4 5 2 BPF. 5. 2 BPF Table 5. Center frequencies and bandwidths of the second BPFs Filter Center frequency Bandwidth Passband signal BPF4 13.6530 6 L1 BPF5 13.6530 9 G1 BPF6 13.6530 8 G2 0 Hz 4:1 2 54.613MHz., 4. 4. Table 4. Intermediate frequencies after frequency translation Signal Translation frequency before translation after translation L1-32.5939 46.2469 13.6530 G1-59.1739 72.8269 13.6530 G2-51.0668 64.7198 13.6530 4. IF IF IF GNSS (real signal) (complex signal).. 6 L1 IF
그림 6. L1 신호의디지털 IF 신호처리과정 Fig. 6. Digital IF processing for the L1 signal. IF cos sin ( ) I, Q. (20ms). [7]. 1/2 E(early), P(prompt), L(late) Early-Late [7] E L ( ). 0 NCO., Doppler., I. 6, GPS L1 6 24. G1 G2 L1 NCO. G1, G2 14 28 IF.. RF GNSS. GNSS 2015 11 10 5 20, 273ms. 7 LNA, AD. LNA 49dB, AD 1966.08MHz. GPS L1 GLONASS G1 L1 (1575MHz 100MHz) GLONASS G2 L2 (1246MHz 50MHz) 390MHz 720MHz. GNSS.
(JBE Vol. 21, No. 5, September 2016) 7. AD Fig. 7. Spectrum of the output of the AD converter.. 8 BPF 1 9:1 L1, G1, G2. 2. 9 DDC LPF IF 2 4:1 IF. 4. (a) (b) (c) 8. 1. (a) L1, (b) G1, (c) G2 Fig. 8. Spectrums of the first decimator outputs for (a) L1, (b) G1, and (c) G2 signals (a) (b) (c) 9. 2. (a) L1, (b) G1, (c) G2 Fig. 9. Spectrums of the second decimator outputs for (a) L1, (b) G1, and (c) G2 signals
L1 G1, G2 6, 5, 6. GPS PRN(pseudo random noise) 1, 3, 4, 11, 28, 32, PRN 1. G1-3, 1, 3, 5, 6, 6. G2 5, 3, -1, -2, -3, -6, 1. 10 L1, G1 G2 3. x (), y.. Doppler,.. 6 6. GNSS Table 6. Results of the receiver test for L1, G1 and G2 signals GNSS signal GPS L1 GLONASS G1 GLONASS G2 Satellites Peak value ( ) Code phase (chips) Doppler shift (Hz) PRN #1 13.1483 3500 13200 PRN #3 12.1563 6500 600 PRN #4 4.1056 3000 11100 PRN #11 11.0357 3500 11200 PRN #28 5.5796 6000 12400 PRN #32 4.5430 4000 3800 Ch #-5 2.3261 48700 25 Ch #-3 2.9871 29000 18 Ch #1 5.3340 27000 25 Ch #3 21.0215 44000 21 Ch #6 27.5315 51000 15 Ch #-1 7.5222 27000 3 Ch #-2 5.1441 18000 2 Ch #-3 4.5389 44000 8 Ch #-6 5.6555 28000 9 Ch #3 2.2862 51000 11 Ch #5 3.5233 48000 1 (a) (b) (c) 10.. (a) L1 PRN #1 (b) G1 Ch #6 (c) G2 Ch #-1 Fig. 10. Correlation functions of spreading codes and the received signals for (a) L1 PRN #1 (b) G1 Ch #6 and (c) G2 Ch #-1 signals
(JBE Vol. 21, No. 5, September 2016) 11. L1 PRN #1 Fig. 11. Maximum correlation value of L1 PRN #1 as a function of time. 11 L1.. +. 50ms,. 20ms... RF GNSS RF, GPS L1, GLONASS G1, G2. L1, G1, G2 6, 5, 6. RF GNSS,.. AD 273ms., Galileo, Beidou GNSS. (References) [1] Walter H.W. Tuttlebee, "Software-defined radio : facets of a developing technology", IEEE Personal Communications, vol. 6, pp. 38-44, 1999. [2] Joseph Mitola, and Gerald Q. Maguire, "Cognitive radio : making software radios more personal", IEEE Personal Communications, vol. 6, pp. 13-18, 1999. [3] M. C. Jackson, P. Matthewson, "Digital processing of bandpass signals", General Electric Company journal of research, vol. 4, no. 1, 1986. [4] Rodney. G. Vaughan, Neil. L. Scott, D. Rod. White, "The theory of bandpass sampling", IEEE Trans. on Signal processing, vol. 39, pp. 1973-1984, 1991. [5] N. Vun and A. Premkumar, "ADC Systems for SDR Digital Front-End, Proc. Ninth Int. Symp. Consumer Electronics (ISCE), Hong Kong, pp. 359-363. June 2005. [6] Ramon Gomez, "Theoretical Comparison of Direct-Sampling Versus Heterodyne RF Receivers", IEEE Trans. on Circuits and Systems I:Regular Papers, Vol. 63, Issue. 8, pp. 1276-1282, Aug. 2016.
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