• AM-AM/AM-PM IN A C-BAND TELEMETRY TRANSMITTER USING 16-APSK

      Baxter, Jason; Perrins, Erik; DePardo, Dan; University of Kansas, Electrical Engineering & Computer Science Department (International Foundation for Telemetering, 2018-11)
      Due to the economic importance of spectrum allocation, modulation schemes traditionally used in telemetry are being replaced with more spectrally efficient schemes. Amplitude and Phase Shift Keying (APSK) is one modulation scheme being considered for implementation in aeronautical telemetry. However, an APSK modulated signal is vulnerable to nonlinearities of a transmitter’s RF power amplifier (PA). Driving a PA into saturation produces two undesired nonlinearities: amplitude-to-amplitude modulation (AM-AM) and amplitude-to-phase modulation (AMPM). This paper characterizes the PA in a C-Band transmitter using a 16-APSK test signal in terms of these nonlinearities.
    • A CHANNEL SPACING ANALYSIS FOR CODED-APSK

      Pathak, Sumant; Perrins, Erik; University of Kansas, Electrical Engineering & Computer Science Department (International Foundation for Telemetering, 2018-11)
      Amplitude Phase Shift Keying (APSK) is an attractive alternative to continuous phase non-linear modulations in telemetry systems with its low Peak-to-Average Power Ratio (PAPR). Since the PAPR is not exactly unity, we use APSK paired with Low-Density Parity Check (LDPC) codes to compensate for loss in power efficiency due to the power amplifier operating with backoff. In this paper we consider the adjacent channel spacing of a system with multiple configurations using LDPC coded APSK and SOQPSK-TG. We consider different combinations of 16 and 32-APSK and SOQPSK-TG and find the minimum spacing in frequency between the respective waveforms that does not distort system performance.
    • SCALABILITY OF MESH NETWORK TELEMETRY FOR SWARMS OF UNMANNED AERIAL SYSTEMS

      Keshmiri, Shawn; Hauptman, Dustin; Shukla, Daksh; Blevins, Aaron; University of Kansas, Electrical Engineering & Computer Science Department; University of Kansas, Department of Aerospace Engineering (International Foundation for Telemetering, 2018-11)
      Swarms of autonomous unmanned aerial systems (UASs) are becoming increasingly popular as efficient replacement for manned aircraft. The major component that makes the swarm of UASs possible is an efficient exchange of aircrafts states (e.g. position & velocity) for all agents and the ground station. Advanced communication technologies are required to be implemented on each agent to enable real-time communication at high frequencies (e.g. 20 Hz) to avoid inter collisions and holding formations. To assess mesh network limitations and to identify bottlenecks, a series of simulations are carried out using actual hardware that is used for swarms of UASs, which are: (1) Amount of bandwidth that can be guaranteed given the communication system being used (XBee-900HP), each plane that the KU team uses, transmits 127 variables, 4 bytes each, at 20 Hz which means each plane needs 10 KBps and the mesh network might be able to support 53 UASs theoretically (2) Range limitations (3) Latency issues.
    • UNIFICATION OF SIGNAL MODELS FOR SOQPSK

      Perrins, Erik; Rice, Michael; University of Kansas, Electrical Engineering & Computer Science Department; BYU, Department of Electrical and Computer Engineering (International Foundation for Telemetering, 2018-11)
      This paper begins by summarizing a recent advancement in the way that shaped offset quadrature phase shift keying (SOQPSK) waveforms can be viewed. This new viewpoint succeeds in eliminating the need for SOQPSK to be thought of as a “special” kind of correlated, ternary continuous phase modulation (CPM). Instead, SOQPSK can be viewed as an ordinary, binary CPM. We provide all of the details necessary to achieve a complete unification of SOQPSK models at the waveform level, at the bit sequence level, and in terms of waveform initialization. With this information, SOQPSK users can easily mix and match SOQPSK models at the transmitter and receiver in order to make use of the advantages of each model.