Ing. Jiří Svatoň, Ph.D.

The upcoming decade will see a surge in Moon exploration missions: public and private actors are targeting a wide range of goals, including human exploration and settlement, scientific research, technology demonstration and in-situ resources utilisation. The achievements that can be obtained during the course of these missions are occasionally limited by the performance of traditional PVT (Position, Velocity, Time) determination systems, in terms of accuracy and latency. To address this issue, the use of Earth GNSS signals for autonomous real-time navigation in the cis-lunar space has been extensively studied, with the authors playing an active role in this well-established field of research. Now it’s time to fly it. In the framework of the NAVISP program, SpacePNT has developed NaviMoon, a ultra-high sensitivity GNSS receiver capable to acquire and track Galileo and GPS signals down to 15 dB Hz, fuse the corresponding measurements with a high-fidelity dynamics model to deliver unprecedented navigation performance (~100 m RMS positioning accuracy). Embarked on SSTL’s Lunar Pathfinder, NaviMoon represents the pivotal element of Phase 1 in ESA’s Lunar PNT Implementation Roadmap. Despite being implemented on a low-cost, COTS-based hardware platform, NaviMoon is designed to operate for at least 3 years in lunar orbit, and it is ready to be evolved into a fully space qualified product used operationally in lunar missions. This paper presents the design of NaviMoon, its simulated performance assessment and the current status of the hardwarein-the-loop test results.

Objective is a joint primary and secondary code (SC) acquisition estimator of tiered Global Navigation Satellite Systems (GNSS) signals. The estimator is based on the Parallel Code Search algorithm (PCS) combined with the Single-Block-Zero-Padding (SBZP) and the Pre-correlation Coherent Accumulation (PCA). The PCA realizes the extension of the coherent integration time in front of the PCS. However, the PCS with the SBZP and the PCA is affected by a navigation/SC bit transition problem due to its cyclic property of a computed Cross-Ambiguity Function (CAF). This CAF is degraded by diverse parasitic fragments and is not directly applicable for an acquisition. A novel analysis of this mechanism and its impact is presented. Then, the proposed modified SBZP (mSBZP) modified PCA (mPCA) PCS estimator is constructed, which does not degrade the CAF. The mSBZP allows the use of the PCS algorithm in the presence of SC bit transition, while the mPCA decreases the number of PCS algorithm calculations by a factor of SC chip count due to SC pre-correlation processing. The algorithm has the same detection performance in comparison with conventional Double-Block-Zero-Padding (DBZP). However, it allows using the PCS of half-length with longer latency up to a factor of SC chip count

This paper presents a new modified Single Block Zero-Padding (mSBZP) Partial Correlation Method (PCM) Parallel Code Search (PCS) algorithm for effective acquisition of weak GNSS tiered signal using coherent processing of its secondary code (SC) component. Two problems are discussed: acquisition of primary codes with longer period using FFT blocks of limited length, and the utilization of PCS in the presence of SC bit transition. The PCM and SC bit transition forms parasitic fragments in the Cross-Ambiguity-Function (CAF) to devaluate signal detection performance. A novel analysis of this mechanism and its impact is presented. A novel mSBZP-PCM-PCS algorithm is proposed, which does not degrade the CAF. Then, the algorithm is combined with SC bit transition removal schema and sequential search to construct an estimator for weak tiered signal acquisition. The performance of the method is demonstrated by analysis and computer simulation using Galileo E1C and GPS L1C-P signals.

Objective of this contribution is the acquisition algorithm for modern GNSS signals containing secondary codes. This algorithm is usable for a hardware based GNSS signal acquisition unit using the parallel code search (PCS) algorithm. The contribution deals with standard post-correlation methods and focuses on a comparison of methods based on a pre-correlation accumulation of the signal by the Pre-correlation Coherent Accumulation principle (PCA). The aim is a comparison of properties of different types of used zero-padding methods in both pre and post correlation approaches. An extension of a coherent time in front of a PCS-FFT algorithm based unit by help of a pre-correlation processing could considerably reduce a required minimal latency of FFT blocks. A latency time equal to one period of primary code for the post-correlation combining is replaced for a proposed algorithm to a much longer time equal to a period of the secondary code.

Correlation of GNSS signals that is implemented into a block processing by help of a FFT allows using and evolving of methods that has never been used before in a traditional continual processing. Our contribution focuses on utilization of a block pre-correlation processing for an acquisition of modern GNSS signals. This method combines the parallel in code search (PCS) algorithm with the Pre-Correlation Averaging (PCA) method for an acquisition of a secondary code of GNSS signals. The PCA method averages samples of consecutives signal periods and averages them together period-by-period coherently to allow using a longer coherent time without additional costs in correlation stage and without boost of the FFT unit size.

This contribution describes an architecture of additional system of memories for an existing GNSS (Global Navigation Satellite Systems) signal acquisition unit in frequency domain. The unit is designed for an FPGA-based HW receiver and has three 4K FFT blocks. The receiver is based on the System on Chip (SoC) Xilinx ZYNQ platform. The proposed additional memories are used as accumulators of complex signals samples and are placed in front or after the acquisition unit. They enable to process GNSS signals of different navigation systems more effectively with limited resources

The objective of this contribution is a design of optimal algorithms for an universal GNSS acquisition unit. The unit is designed for a FPGA-based HW receiver and is implemented in frequency domain with three 4K FFT blocks. The unit is able to acquire usual civil signals (GPS C/A, BeiDou B1, IRNSS L5/S-band, and GLONASS L1OF) directly and to acquire the Galileo E1 longer code signal with proposed improved algorithm of the partial correlation. Pre- and mainly post-correlation methods are analyzed and selected with respect to implementation on the target System on Chip (SoC) Xilinx ZYNQ platform with limited computing resources.

The objective of this contribution is a design of universal GNSS acquisition unit for an FPGA-based HW receiver, which is able of direct acquisition of usual civil signals (GPS C/A, BeiDou B1, IRNSS L5/S-band, and GLONASS L1OF). Due to high complexity of calculation and requirements for latency, processing in frequency domain with parallel search in code is adopted. Optimal processing methods even for the long codes of Galileo E1 or future GPS L1C signals are analyzed. For each block of the acquisition unit, a method is selected with respect to implementation on the target System on Chip (SoC) Xilinx ZYNQ platform. The unit is intended as a HW acquisition accelerator with a minimal SW handling requirements for the developed receiver.

We are witnesses of a big boom in satellite navigation today. Current systems are updated with new signals, new systems are in development and new frequency bands are searched due a overcrowding of L-band. Current GNSS systems with full operational capacity are two yet. American GPS and Russian Glonass. GPS third generation with new L1C signal is ready to launch and Glonass is in preparation for its first CDMA signal. Beside of European Galileo countries on east are developing own satellite navigation systems. Chinese BeiDou 2 (called as a Compass for a short time in past) and Indian IRNSS are potentially most interesting systems for us. The Chinese BeiDou in its second global coverage generation prepare new type of satellite. First BeiDou 2 satellites were launched after 2007 and its first signal specification was publicized in 2011, second one with specification of signal in another frequency in 2013. We were able to track and verify both signals in 2012. Indian Regional Navigation Satellite System – IRNSS satellites were launched since 2013 and its signals specification is known since half of year 2014. This system has a regional coverage so far, but will be probably developed to the global navigation system. We deals with it because its signals also covers a considerable part of Eastern and Central Europe and its L5 signal has been received even in Finland. IRNSS also implement signal in new frequency band out of a traditional Lband as the first. Existing GNSS systems are a traditional application of L-band (from 1 to 2 GHz). Usage of an additional band for the Radio Navigation Satellite Service (RNSS) purpose has been considered since 1998. The S (2483.5 to 2500 MHz) and C (5010 to 5030 MHz) bands have been taken into account in the process of the Galileo signals design too, but hasn’t been used for Galileo yet. A part of the S-band has been lately used for the Open Service of the Regional Indian Radio Navigation Satellite System.

The satellite navigation is typically considered as the processing of satellite radio signals in the L frequency band (1.151 to 1.214, 1.215.6 to 1.350, and 1.559 to 1.617 GHz). However, in the process of the Galileo signals design the S (2483.5 to 2500 MHz) and C (5010 to 5030 MHz) bands have been taken into account, too. The S band was allocated to the Radiodetermination Satellite Service by the International Telecommunication Union (ITU) at the World Radio Conference 2000 (WRC 2000), whereas the C band signals were intensively studied in the period 1998 – 2004. Both of the bands were associated with the plans for the Galileo but have not been applied yet. A part of the S band has been lately (since summer 2013) used for the Open Service of the Regional Indian Radio Navigation Satellite System (IRNSS). The two bands have both specific advantages and deficiencies which we will analyse in our contribution. We will refer also to our experiments with the S band IRNSS signals reception and their use for determination of ionosphere and troposphere properties.

Accurate positioning is a strategic information. Beside of American GPS and Russian Glonass another countries on east are developing own satellite navigation systems. The Chinese BeiDou and Indian IRNSS are potentially most interesting systems for us. Although the first plans for an independent Chinese satellite navigation system could be dated in an end of previous century first satellites were launched after 2007 and its first signal specification was publicized in 2011. Very interesting is Indian Regional Navigation Satellite System – IRNSS. Satellites were launched since 2013 and its signal specification is known since half of year 2014. IRNSS specifies the first public signal out of L-band as a first GNSS systems. Our contribution describes our experience with these systems and with a first reception of satellite navigation system signal in S-band

This work deals with construction of the high frequency part of the future multi-constellation GNSS receiver. We investigate influence of this part called a radio front-end to systematic navigation receiver parameter – a positioning error. At the start we summarize the current information about the space vehicle constellation of present and planned global navigation satellites systems as is GPS, Glonass, Galileo and BeiDou 2. Then we compare current and future state of GNSS and potential benefits. Firstly we explain effect of the satellite constellation to error using DOP factor (dilution of precision) and benefits of multi-constellation. The crucial part is a study of influence of radio front-end parts parameters as is noise proportion and bandwidth to this error. Subsequently we use this knowledge for a development of self radio-front end parts as are ultra-low noise antenna preamplifier and unit for amplifying and filtering of each GNSS sub bands.

Although the sensitivity analysis is implemented in contemporary software tools for computer-aided design, kinds of available sensitivities are limited. For example, Spice or Micro-Cap calculate DC or small-signal AC sensitivities, and SpectreRF contains a periodic noise analysis or a parametric sensitivity analysis that can be efficiently used for determining the phase noise. In this paper, some novel types of the noise sensitivity analysis are described, which are not implemented in the usually applied circuit simulators. First, a procedure for determining the sensitivities of the noise figure was suggested. Second, an improvement of the algorithm for computing the noise figure was described, which incorporates circuit matching and eliminates necessary subtraction of the output noise generated by the load resistance at each frequency. Third, a new formula was derived for a computation of the sensitivities of the noise figure. The sensitivity analysis of the noise spectral density is demonstrated by means of an analytically solved example. The application of the sensitivity analysis of the noise figure for improving the noise properties of a microwave integrated circuit is described in a detailed way as well. Finally, using a sophisticated multi-objective optimization is suggested for a better selection of the operating point instead of classical circuit matching. This method was utilized for a practical design of an antenna preamplifier for a GPS/Galileo/GLONASS/Compass receiver.

The paper presents analysis of the requirements on the RF Front-end of the Multi-Constellation GNSS Receiver. One of the main problems of the multi-constellation GNSS receiver is the amplifying ans splitting of signals of partial systems working in different bands.The paper studies a variety of possibilities of the design of the multi-constellation receiver frontend from the noise figure and jamming resistance point of view.