1 : GNSS RF (Jong-Won Choi et al.: Design and Performance of a Direct RF Sampling Receiver for Simultaneous Reception of Multiband GNSS Signals) (Regu

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1 (Regular Paper) 21 5, (JBE Vol. 21, No. 5, September 2016) ISSN (Online) ISSN (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

2 (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) boseok@cbnu.ac.kr Tel: ORCID: ,. Manuscript received June 21, 2016; Revised August 30, 2016; Accepted August 30, ~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

3 [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),,

4 (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..

5 . 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 kHz MHz MHz. G2 1. GNSS RF Fig. 1. Structure of the direct RF sampling receiver for multiband GNSS signals

6 (JBE Vol. 21, No. 5, September 2016) -7 6 G1 14, 437.5kHz 1246 MHz MHz MHz.. 2 (1) ~ (4) 1 ~ 2 GHz.. TI, (1) ~ (4) MHz. 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 GLONASS G1 FDMA/SS/BPSK ~ G2 FDMA/SS/BPSK ~ GPS L1, GLONASS G1, G2 RF Fig. 2. Allowable sampling frequency ranges for direct RF sampling of GPS L1, GLONASS G1 and G2 signals

7 3. RF Fig. 3. Structure of the digital RF signal processing BPF Table 2. Center frequencies and bandwidths of the anti-aliasing BPFs (a) Filter Center frequency Bandwidth Passband signal BPF L1 BPF G1 BPF G2 GPS L1 C/A 2.046MHz. ( ( )/() Q ) MHz 10MHz MHz G MHz 20MHz BPF, MHz G 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: MHz, 1/9 3.

8 (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 :1 Table 3. Intermediate frequencies after 9:1 decimation Signal before decimation after decimation L G G IF 0Hz DDC. DDC. L BPF BPF Table 5. Center frequencies and bandwidths of the second BPFs Filter Center frequency Bandwidth Passband signal BPF L1 BPF G1 BPF G2 0 Hz 4: MHz., Table 4. Intermediate frequencies after frequency translation Signal Translation frequency before translation after translation L G G IF IF IF GNSS (real signal) (complex signal).. 6 L1 IF

9 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 L G1 G2 L1 NCO. G1, G IF.. RF GNSS. GNSS , 273ms. 7 LNA, AD. LNA 49dB, AD MHz. GPS L1 GLONASS G1 L1 (1575MHz 100MHz) GLONASS G2 L2 (1246MHz 50MHz) 390MHz 720MHz. GNSS.

10 (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, G DDC LPF IF 2 4:1 IF. 4. (a) (b) (c) (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) (a) L1, (b) G1, (c) G2 Fig. 9. Spectrums of the second decimator outputs for (a) L1, (b) G1, and (c) G2 signals

11 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, L1, G1 G2 3. x (), y.. Doppler, 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 # PRN # PRN # PRN # PRN # PRN # Ch # Ch # Ch # Ch # Ch # Ch # Ch # Ch # Ch # Ch # Ch # (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

12 (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 L ms,. 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 , [2] Joseph Mitola, and Gerald Q. Maguire, "Cognitive radio : making software radios more personal", IEEE Personal Communications, vol. 6, pp , [3] M. C. Jackson, P. Matthewson, "Digital processing of bandpass signals", General Electric Company journal of research, vol. 4, no. 1, [4] Rodney. G. Vaughan, Neil. L. Scott, D. Rod. White, "The theory of bandpass sampling", IEEE Trans. on Signal processing, vol. 39, pp , [5] N. Vun and A. Premkumar, "ADC Systems for SDR Digital Front-End, Proc. Ninth Int. Symp. Consumer Electronics (ISCE), Hong Kong, pp June [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 , Aug

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