Apparatus for a digital averaging filter, particularly suited for use with an aeronautical navigation receiver, for reducing oscillatory deviation errors that appear in a course deviation voltage produced by the receiver and occur as the result of reflected incoming radio-navigation signals and/or interfering signals as described. In essence, this apparatus first amplifies, filters and repetitively samples the course deviation voltage to provide digital representations thereof. Each digital representation is then converted by a digital to pulse count converter into a series of pulses wherein the value of each digital representation is encoded into the number of pulses in the series. Thereafter, these pulses are totalized over a pre-defined interval. The resulting totalized count is then divided to produce an average value, which at the end of the pre-defined interval accurately reflects the average course deviation error.
Phase-Locked Digital Very High Frequency Omni-Range (Vor) Receiver
A very high frequency omni-range (VOR) receiver for use in aircraft radio-navigation, which provides an indication of course deviation that is substantially immune to effects such as reflections in transmitted VOR signals, transients occurring in an aircraft's electrical system and propeller and/or rotor modulations of an incoming VOR signal and the like which are all unrelated to actual course deviation, is disclosed. Specifically, in accordance with the invention, a stream of timing pulses is generated which are accurately phase-locked to a stream of pulses corresponding to a received reference signal transmitted from a desired VOR station. Both these streams are then used to produce an "OBS" signal which is phase shifted by an amount representative of a preselected radial emitted by that station. Thereafter, the phase difference occurring between the OBS signal and a stream of pulses corresponding to a received variable signal transmitted by that same VOR station is determined and used to produce a deviation signal. The deviation signal has a value that represents any course deviation existing between the preselected radial and the present magnetic course of the aircraft with respect to the VOR station and is advantageously substantially unaffected by any effects other than actual course deviations.
Rapidly Responding Vertical Speed Indicator For Use In Aircraft
A vertical speed indicator uses a substantially rigid hollow closed air chamber; a capillary tube having a reduced inside diameter connected to the chamber for routing atmospheric air from an aircraft static system at a reduced flow rate into the chamber; a differential pressure transducer having two inlet ports; a pneumatic conduit connecting the chamber and one of the ports of the transducer for exposing that port to internal chamber air pressure; a pneumatic conduit connected to the other port for exposing that port to atmospheric pressure occurring within the static system; and electronic processing circuitry connected to the transducer for providing an indication of the vertical speed of the aircraft. The processing circuit first compensates the signal by varying its phase in a leading direction to at least offset any pneumatic induced lag occurring in the inventive VSI, and then amplifies and displays the result on a zero center analog meter or digitizes it for subsequent use by other airborne avionic systems. Alternatively, the compensated signal can be digitally averaged over a pre-defined time period to remove random noise and similar effects.
Apparatus And Method For Use In Instrument Landing System Localizer And Glide-Slope Receivers For Deriving Course Deviation Information
Apparatus and method for use in instrument landing system (ILS) localizer and/or glide-slope receivers for deriving course deviation information are described. Specifically, a detected incoming ILS (localizer or glide-slope) signal is first filtered in order to extract appropriate 90 and 150 Hz navigation tones therefrom. Thereafter, two streams of timing pulses are generated; the first stream is phase-locked to the 90 Hz navigation tone and the second stream is phase-locked to the 150 Hz navigation tone. The peak amplitude of the 90 Hz navigation tone is sampled in response to the occurrence of a particular timing pulse occurring in the first pulse stream and the peak amplitude of the 150 Hz navigation tone is sampled in response to the occurrence of a particular timing pulse occurring in the second pulse stream. The sampled values of both navigation tones are then combined to obtain the difference therebetween which, in turn, is used to produce a signal which represents the actual localizer or glide-slope course deviation.
Crystal Oscillator Synchronized Digital Very High Frequency Omni-Range (Vor) Instrumentation Unit
A very high frequency omni-range (VOR) receiver for use in aircraft radio-navigation, which provides an indication of course deviation that is substantially immune to effects such as reflections in transmitted VOR signals, transients occurring in an aircraft's electrical system and propeller and/or rotor modulations of an incoming VOR signal and the like which are all unrelated to actual course deviation, is disclosed. The receiver phase synchronizes a signal from a 1. 08 MHz crystal oscillator to a 30 Hz reference signal and a 30 Hz variable signal; both the reference and variable signals are received from a VOR ground station. As a result of the phase synchronization, the receiver produces timing pulses which are accurately phase synchronized to a synchronized reference pulse stream derived from the 30 Hz reference signal. Additionally, the receiver produces a synchronized variable pulse stream that is derived from the 30 Hz variable signal. The receiver produces, in response to the synchronized reference pulse stream and the timing pulses, a signal (henceforth referred to as the "OBS" signal) which is phase shifted by an amount representative of a selected radial emitted by that station.