Software Defined DCF77 Receiver

This paper shows the solution of time stamp software defined receiver integration into low cost com-mercial devices. The receiver is based on a general pur-pose processor and its analog to digital converter. The amplified signal from a narrow-band antenna is connected to the converter and no complicated filtration has to be used. All signal processing is digitally provided by the processor. During signal reception, the processor stays available for its main tasks and signal processing con-sumes only a small part of its computational power

The Model of the Low Rate Telemetry Communication System for Matlab-Simulink

This article is dedicated to the model of low rate telemetry system, which has been developed for Matlab-Simulink environment. The purpose of this model is a research of the low rate telemetry transmission reliability in those cases where the modulation scheme carrier-subcarrier is used. This modulation scheme is widely used in case of the interplanetary spacecrafts. The main purpose of the model is a research of the effects of AWGN and phase noise especially for very low value of Eb/N0. Effects can be evaluated for the whole transmission system or for its components parts. The model described is very versatile and it can be easily modified or expanded

Efficient Spectral Power Estimation on an Arbitrary Frequency Scale

The Fast Fourier Transform is a very efficient algorithm for the Fourier spectrum estimation, but has the limitation of a linear frequency scale spectrum, which may not be suitable for every system. For example, audio and speech analysis needs a logarithmic frequency scale due to the characteristic of a human’s ear. The Fast Fourier Transform algorithms are not able to efficiently give the desired results and modified techniques have to be used in this case. In the following text a simple technique using the Goertzel algorithm allowing the evaluation of the power spectra on an arbitrary frequency scale will be introduced. Due to its simplicity the algorithm suffers from imperfections which will be discussed and partially solved in this paper. The implementation into real systems and the impact of quantization errors appeared to be critical and have to be dealt with in special cases. The simple method dealing with the quantization error will also be introduced. Finally, the proposed method will be compared to other methods based on its computational demands and its potential speed

Band-monitoring Payload for a CubeSat Satellite

During changing sun activity, the ionosphere is responding accordingly and therefore it is interesting to observe the propagation behavior of shortwave bands. For the above mentioned purpose we have designed a band-monitoring payload for an experimental CubeSat satellite. The payload consists of a receiver, which is able to receive SSB modulated narrowband signals in 28 MHz uplink band, and a transmitter with FM modulation in UHF downlink band. The receiver frequency is selected to be at the center of radio amateur activity with low data rate digital modulations

Novel Optimization Method of Active Frequency Multiplier Utilizing Harmonic Terminating Impedances with DGS

A novel method for the optimization of the active frequency multiplier utilizing the harmonic terminating impedances with the defected ground structures (DGS) has been developed. Furthermore, a new type of the low-pass filter with DGS for the higher harmonic suppression will be reported. Experimental conversion gains (14.52 dB for the doubler, 5.56 dB for the tripler and 0.43 dB for the quadrupler) and real power-added efficiency (32.76 % for the doubler, 10.15 % for the tripler and 1.42 % for the quadrupler) have been attained. To our knowledge, in the considered frequency range, these results represent the best performance reported up to date for the active frequency multipliers utilizing the low-cost BJTs

The Low Rate Telemetry Transmission Simulator

The presented paper is dedicated to the low rate telemetry transmission simulator. The basic concept of the system uses the carrier (DSB) and subcarrier (BPSK). The research is focused on the AWGN and carrier phase noise influence. Presented system can be extended with the described carrier phase noise model. In this paper, some issues related to the described model are also discussed. For example, the relation between bit error rate for uncoded bit stream and bit stream with differential coding, which is used in the model. Authors prove the using of Costas loops for very low energy per bit to noise power spectral density ratio. The influence of additive white Gaussian noise and phase noise is also investigated

Effective DSP Methods of PSK Feedback Timing Synchronization

This paper deals with simplification and improvement of data timing synchronization algorithms. Timing error synchronizers are usually the most complicated subsystems in the demodulator, and limit the DSP technique used for the high-rate application. This article is focused on feedback timing estimators for PSK modulation schemes, and shows modifications of widely used algorithms, that are suitable for the DSP implementation, as well as reach better parameters of the detection process. The methods applied in the evaluation of a timing error detector, which is a crucial part of the synchronizer, are described in the last part

Modeling of the Phase Noise in Space Communication Systems

Our work is focused on the investigation of an influence of an additive thermal noise and a multiplicative phase noise in space communication chains. The most important properties of both noise types are summarized. The main concern of this paper is on the multiplicative phase noise that is especially important in systems with the phase shift keying. The simulation procedure for modeling of a signal degraded by the multiplicative phase noise is described. One starts from the frequency domain, where noise properties are set up. Five basic phase noise types can be included. After a passing to the time domain, the final noisy signal is obtained. To prove the modeling correctness, two ways are used. Firstly, Allan variances are utilized as a time domain processing. Finally, for a comparison, the direct conversion formula from the frequency to the time domain is exploited. Created signal corrupted by the phase noise expresses the harmonic oscillator output signal. A pair of these oscillators, disturbed by different phase noise processes, is installed into a communication channel model and with its help, the simultaneous influence of both oscillators on the useful signal is examined. Results show a good coincidence with theoretical presumptions

Static and Dynamic Nonlinearity of A/D Converters

The dynamic range of broadband digital system is mostly limited by harmonics and spurious arising from ADC nonlinearity. The nonlinearity may be described in several ways. The distinction between static and dynamic contributions has strong theoretical motivations but it is difficult to independently measure these contributions. A more practical approach is based upon analysis of the complex spectrum, which is well defined, easily measured, and may be used to optimize the ADC working point and to somehow characterize both static and dynamic nonlinearity. To minimize harmonics and spurious components we need a sufficient level of input noise (dither), which destroys the periodicity at multistage pipelined ADC, combined with a careful analysis of the different sources of nonlinearity

Identification Of Novel Autoinducer-2 Receptors In Clostridia Reveals Plasticity In The Binding Site Of The LsrB Receptor Family

Autoinducer-2 (AI-2) is unique among quorum-sensing signaling molecules, as it is produced and recognized by a wide variety of bacteria and thus facilitates interspecies communication. To date, two classes of AI-2 receptors have been identified: the LuxP-type, present in the Vibrionales, and the LsrB-type, found in a number of phylogenetically distinct bacterial families. Recently, AI-2 was shown to affect the colonization levels of a variety of bacteria in the microbiome of the mouse gut, including members of the genus Clostridium, but no AI-2 receptor had been identified in this genus. Here, we identify a noncanonical, functional LsrB-type receptor in Clostridium saccharobutylicum. This novel LsrB-like receptor is the first one reported with variations in the binding-site amino acid residues that interact with AI-2. The crystal structure of the C. saccharobutylicum receptor determined at 1.35 Å resolution revealed that it binds the same form of AI-2 as the other known LsrB-type receptors, and isothermal titration calorimetry (ITC) assays showed that binding of AI-2 occurs at a submicromolar concentration. Using phylogenetic analysis, we inferred that the newly identified noncanonical LsrB receptor shares a common ancestor with known LsrB receptors and that noncanonical receptors are present in bacteria from different phyla. This led us to identify putative AI-2 receptors in bacterial species in which no receptors were known, as in bacteria belonging to the Spirochaetes and Actinobacteria phyla. Thus, this work represents a significant step toward understanding how AI-2–mediated quorum sensing influences bacterial interactions in complex biological niches