Apparatus for providing a digital signal for an aircraft transponder indicating aircraft altitude with a unique sensor forming part of an oscillator, a counter which accumulates counts from the sensor during a predetermined gating period, a ROM which is addressed during a further gating period to apply a sequence of digital numbers to a comparator. The address indicating one thousand foot increments a second counter which receives pulses from the sensor together with the first counter after the comparator indicates the ROM number exceeds the first counter number so that the number in the second counter indicates one hundred foot and 10 foot increments when the comparator indicates the first counter number equals the ROM output to the comparator and gating for applying the outputs of the second counter and ROM address to the transponder for transmission. In one embodiment structure for providing barometric correction is included.
A low altitude radio altimeter of the FM/CW type which transmits a sawtooth frequency wave and has a transmitting and a receiving aerial. A beat frequency signal Fb.sub.t between the transmitted and received waves is produced at the output of a mixer. The altimeter includes means for digitizing Fb.sub.t at the rate of n samples per sawtooth, a first memory (M1) to store n.times.k samples S.sub.j.sup.i (where i varies from 1 to k and j varies from 1 to n), a second memory (M2) to store n sums ##EQU1## first computing means (PR) for determining ##EQU2## representative of Fb.sub.4, for storage in a third memory (M3), and additional computing and storage means (PR, M4) producing difference signals Fb.sub.t -Fb.sub.f.
An apparatus for converting aircraft altitude encoder measurements into higher resolution values, including a microprocessor connected to monitor the aircraft altitude encoder output signals, a pressure transducer and converter network for providing incremental pressure change readings, also connected to the microprocessor; the microprocessor being programmed to utilize the incremental pressure readings to calculate corresponding incremental altitude signals between transition points of the aircraft altitude encoder readings. The method of the invention includes the steps of monitoring aircraft altitude encoder transition points, reading incremental pressure variations between transition points, and calculating incremental altitude variations between altitude encoder transition points.
An altimeter code converter that converts a parallel signal of a first code to a serial signal of a second code; The code converter of this invention includes a code conversion means having memory means with an addressable look-up table to convert Gray code to a binary code; a data conversion means having parallel-to-series shift registers connected in series and a flip-flop parity generator for converting the parallel signal to a serial signal; and operably connected to the above means are means for forming and outputting timing and initializing signals.
A solid-state barometric altimeter-encoder. The atmospheric pressure is cared to a reference vacuum on a hybrid IC pressure transducer which generates a proportional signal. This analog signal is then converted into digital data, corrected for atmospheric to altitude non-linearity by use of a ROM look-up table, displayed as a digital readout and also converted to Grey code format for transponder MC (altitude) transmission.
Utilizing a three-wire input from a synchro, a signal representing the rate of rotation of the synchro shaft is generated by means of: summing amplifiers to generate signals representing the cosine of the shaft angle and the sine of the shaft angle; a circuit for generating a signal representing the tangent of the shaft angle; a circuit for generating the signal representing the cotangent of the shaft angle; feedback circuits for linearizing both the tangent and cotangent signals; a differentiator circuit for differentiating the tangent signal; a differentiator circuit for differentiating the cotangent signal; and a switching circuit for selecting the rate output from the differentiator with a linear output.
