In the conventional airborne telemetry system, the pre-modulation filter with a multipole active Bessel filter is preferred to use in Pulse Code Modulator (PCM)/FM transmission. In the existing system, it is not possible to change the cutoff frequency for different data rates dynamically as required in the launch scenario of a long-range aerospace vehicle. In general, aerospace vehicle has multiple propellant stages to travel a desired trajectory path. Each stage gets separated from the vehicle at different instances. Each stage measurement plan is defined and correspondingly the PCM format is generated with an optimum data rate. Hence, the telemetry system is required to transmit variable data rates at various instances of a long-range aerospace vehicle from launch point to end point of a vehicle. This can be addressed by designing a dynamically tuneable pre-modulation (DTPM) filter. Here, a suitable DTPM filter scheme is proposed to mitigate variable data rate transmission in the telemetry system. The scheme is analysed as per IRIG-106 standard and simulated using MATLAB. The same has been modelled using VHDL and implemented targeting 28 nm technology Xilinx Zynq FPGA device. How to cite this article: Karnati SR, Bopanna L, Jahagirdar DR. Dynamically tuneable pre-modulation filter for an airborne PCM/FM telemetry system. IET

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The on-board telemetry system of an aerospace vehicle sends the vehicle performance parameters to the ground receiving station at all instances of its trajectory. During the course of its trajectory, the communication channel of a long range vehicle, experiences various phenomena such as plume attenuation, stage separation, manoeuvring of a vehicle and RF blackout, causing loss of valuable telemetry data. The loss of communication link is inevitable due to these harsh conditions even when using the space diversity of ground receiving systems. Conventional telemetry systems do not provide redundant data for long range aerospace vehicles. This research work proposes an innovative delay data transmission, frame switchover and multiple frames data transmission schemes to improve the availability of telemetry data at ground receiving stations. The proposed innovative schemes are modelled using VHDL and extensive simulations have been performed to validate the results. The functionally simulated net list has been synthesised with 130 nm ACTEL flash based FPGA and verified on telemetry hardware.

Airborne telemetry data is inevitable during the development phase of an aerospace vehicle. With the availability of telemetry data the vehicle characteristics are evaluated and the vehicle objectives are achieved subsequently. During the trajectory path, the airborne telemetry system transmits vehicle data continuously and ground receiving station receives it. The availability of data at ground station is solely dependent on various parameters; primarily data rate, modulation, RF power, etc. In this paper, typical data rate of telemetry for long range aerospace vehicle is analyzed and an innovative scheme is proposed for optimal data rate transmission with multi-resolution of high speed image data for distributed telemetry system. The scheme is implemented on 25 nm ZYNQ CSOC of telemetry hardware and synthesized netlist is simulated, performance is evaluated and results verified on telemetry hardware.