1,486 research outputs found
Low cost tracking Navaids error model verification
Features and characteristics of the tracking navaids (Microwave Scanning Beam Landing System, Radar Altimeter, Tacan, rendezvous radar and one way Doppler extracter) were investigated. From the investigation, a set of specifications were developed for building equipment to verify the error model of the tracking navaids. Breadboard verification equipment (BVE) was built for the Microwave Scanning Beam Landing System and the radar altimeter. The breadboard verification equipment generates signals to the tracking navaids which simulate the space shuttles trajectory in the terminal area. The BVE simulates sources of navaids error by generating pseudorandom perturbations on the navaids signals. Differences between the trajectory value and the navaid derived values are taped and form the basis for the navaids error model
Communications techniques and equipment: A compilation
This Compilation is devoted to equipment and techniques in the field of communications. It contains three sections. One section is on telemetry, including articles on radar and antennas. The second section describes techniques and equipment for coding and handling data. The third and final section includes descriptions of amplifiers, receivers, and other communications subsystems
Interstellar Communication: The Case for Spread Spectrum
Spread spectrum, widely employed in modern digital wireless terrestrial radio
systems, chooses a signal with a noise-like character and much higher bandwidth
than necessary. This paper advocates spread spectrum modulation for
interstellar communication, motivated by robust immunity to radio-frequency
interference (RFI) of technological origin in the vicinity of the receiver
while preserving full detection sensitivity in the presence of natural sources
of noise. Receiver design for noise immunity alone provides no basis for
choosing a signal with any specific character, therefore failing to reduce
ambiguity. By adding RFI to noise immunity as a design objective, the
conjunction of choice of signal (by the transmitter) together with optimum
detection for noise immunity (in the receiver) leads through simple
probabilistic argument to the conclusion that the signal should possess the
statistical properties of a burst of white noise, and also have a large
time-bandwidth product. Thus spread spectrum also provides an implicit
coordination between transmitter and receiver by reducing the ambiguity as to
the signal character. This strategy requires the receiver to guess the specific
noise-like signal, and it is contended that this is feasible if an appropriate
pseudorandom signal is generated algorithmically. For example, conceptually
simple algorithms like the binary expansion of common irrational numbers like
Pi are shown to be suitable. Due to its deliberately wider bandwidth, spread
spectrum is more susceptible to dispersion and distortion in propagation
through the interstellar medium, desirably reducing ambiguity in parameters
like bandwidth and carrier frequency. This suggests a promising new direction
in interstellar communication using spread spectrum modulation techniques
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