TWSTFT using DPN signals Yi-Jiun Huang and Wen-Hung Tseng National Time and Frequency Standard Lab., Chunghwa Telecommunication Laboratories (TL), Taiwan APMP 2012 November 26, 2012 Wellington, New Zealand Telecommunication Laboratories

Outline Introduce DPN TWSTFT signal and system DPN TWSTFT system @ 2010 and 2012 Time link result and TDEV comparison Summary and discussion Telecommunication Laboratories

Dual Pseudorandom Noise (DPN) Signal Telecommunication Laboratories

Communication Channel DPN TWSTFT System Conventional Modem does not support TX/RX function for DPN Hardware: Arbitrary waveform generator A/D sampler Software: (especially at RX) Signal acquisition  tracking Group delay estimation, i.e. τ = - dφ/dω (Use GPU for accelerating correlation and convolution) A/D Sampler, 64Msps Arbitrary Waveform Generator Communication Channel Sample Stream Software PC with GPU Telecommunication Laboratories

DPN TWSTFT System (Receiver) A/D FFT LNB I F T Phase Detector Group Delay Band Pass Filter LO, 11.3 GHz Down Converter NCO, higher tone NCO, lower tone UTC (TL) Pseudorandom Code Telecommunication Laboratories

DPN TWSTFT System @ 2010 UTC(TL) UTC(NICT) IS-8 AWG A/D AWG A/D 66.4 MHz 86.4MHz 66.4 MHz 86.4MHz Wideband BPF 20MHz Telecommunication Laboratories

Time Link Result @ 2010 17 days Telecommunication Laboratories

Time Link Result @ 2010 2 days Telecommunication Laboratories

TDEV Comparison @ 2010 PPP: 15ps@300s DPN: 9.9ps@300s Telecommunication Laboratories

Modification of DPN system @ 2012 To improve short term resolution: Increase band separation (not occupied bandwidth) Use narrow BPF to avoid in-band noise thus get high signal-to-noise ratio Unfortunately, observations: 300 (real time)  15 @5min Telecommunication Laboratories

DPN TWSTFT System @ 2012 UTC(TL) UTC(NICT) GE-23 54.175MHz AWG A/D AWG Wideband BPF 32MHz Narrowband BPF 4MHz Telecommunication Laboratories

TDEV Comparison @ 2012 DPN: 14.9ps@300s PPP: 12.3ps@300s Telecommunication Laboratories

Comparison DPN TWSTFT Experiment @2010 @2012 future Observation 300 obs @ 5min 15 obs @5min 300 obs @5min Real-time observation? Yes No Separation 20 MHz 31.2 MHz Single bandwidth / code rate 200 kHz / 127.75 kcps Band Pass Filter 20MHz@NICT, TL 4MHz x 2 @NICT 32MHz@TL 2MHz x 2 @NICT, TL TDEV @ 300 s 9.9 ps 14.9 ps < 10 ps(expected) Telecommunication Laboratories

Summary and Discussion We appreciate NICT colleagues for their great deals of system development and equipment DPN saves more bandwidth (200kHz x 2) than conventional TWSTFT (2.5 MHz) DPN provides the same resolution (10 ps level) as GPS PPP and DPN can be perform in real-time DPN TWSTFT has been conducted between NICT and TL (baseline more than 2000km) for 9 months, and it agreed with Cirt. T. Only a fixed offset existed due to no calibration Software-based receiver can be more flexible than the conventional one, e.g. decoding algorithm can be modified Telecommunication Laboratories

Summary and Discussion We appreciate NICT colleagues for their great deals of system development and equipment DPN saves more bandwidth (200kHz x 2) than conventional TWSTFT (2.5 MHz) DPN provides the same resolution (10 ps level) as GPS PPP and DPN can be perform in real-time DPN TWSTFT has been conducted between NICT and TL (baseline more than 2000km) for 9 months, and it agreed with Cirt. T. Only a fixed offset existed due to no calibration Software-based receiver can be more flexible than the conventional one, e.g. decoding algorithm can be modified Thank you for your listening!! Telecommunication Laboratories