Landing and approach system scan-rate station identification

Claim 2

In a microwave landing system of the type wherein a left localizer, upper glide slope, right localizer, and lower glide slope beam are switched on and off in sequence, for reception by an airborne receiver, apparatus to permit transmitting and receiving a Morse Code identification of the station transmitting the beams comprising: a. means to generate a beam switching input to the transmitter to cause the beams to be switched at a first frequency to represent a mark and a second frequency to represent a space; and b. means in the airborne receiver to decode said first frequency and provide a tone output on each occurrence of said first frequency.

Claim 3

The invention according to claim 1 wherein said means to generate said switching input comprise: a. means to generate logic signals representative of the station code; b. an oscillator; and c. means to divide said oscillator output by a first number when said logic signal indicates a mark and by a second number when said logic signal indicates a space.

Claim 4

The invention according to claim 2 wherein said logic signal means provides a first signal when a mark is to be transmitted and a second signal when a space is to be transmitted and said means to divide comprise: a. a first AND gate having said oscillator output and said first signal as inputs; b. a first divider, adapted to divide by said first number, obtaining its input from said first AND gate; c. a second AND gate having said oscillator output and said second signal as inputs; d. a second divider, adapted to divide by said second number, obtaining its input from said second AND gate; and e. an OR gate having the outputs of said first and second dividers as inputs and providing said beam switching input to said transmitters as its output.

Claim 5

The invention according to claim 3 wherein said logic means comprise: a. a code wheel having alternate opaque and clear areas representing the station code; b. means to rotate said wheel; c. a light source on one side of said wheel; d. a photodetector on the other side of said wheel opposite said light source; and e. an inverter coupled to the output of said detector whereby said detector output is said first logic signal and said inverter output said second logic signal.

Claim 6

The invention according to claim 1 wherein said means to decode comprises: a. a bandpass filter centered at the second harmonic of said first frequency and having its input coupled to one of the local oscillator mixer outputs of the receiver; b. a detector coupled to the output of said filter to provide an output when its input exceeds a value indicative of signal reception at one of said first frequency and said second harmonic; c. an audio tone generator; and d. a sound transducer coupled to said tone generator to provide an aural tone output.

Claim 7

In a microwave landing system of the type wherein a left localizer, upper glideslope, right localizer, and lower glideslope beam are switched on and off in sequence, for reception by an airborne receiver, apparatus to permit transmitting and receiving a Morse Code identification of the station transmitting the beams comprising: a. a code wheel having alternate opaque and clear areas representing the statIon code; b. means to rotate said wheel; c. a light source on one side of said wheel; d. a photodetector on the other side of said wheel opposite said light source; e. an inverter coupled to the output of said detector whereby said detector output provides a first logic signal and said inverter output provides a second logic signal; f. an oscillator; g. a first AND gate having said oscillator output and said first signal as inputs; h. a first divider, adapted to divide by a first number, obtaining its input from said first AND gate and providing an output at a first frequency; i. a second AND gate having said oscillator output and said second signal as inputs; j. a second divider adapted to divide by a second number obtain its input from said second AND gate and providing an output at a second frequency; k. an OR gate having the outputs of said first and second dividers as input and providing its output as a beam switching input to the transmitter; l. a bandpass filter in the airborne receiver countered at the second harmonic of said first frequency and having its input coupled to one of the local oscillator mixer outputs of the receiver; m. a detector coupled to the output of said filter to provide an output when its input exceeds a value indicative of signal reception at one of said first frequency and second harmonic; n. an audio tone generator; and o. a sound transducer coupled to said tone generator to provide an aural tone output.

Claim 8

In a microwave landing system of the type wherein a left localizer, upper glideslope, right localizer, and lower glideslope beam are switched on and off in sequence, for reception by an airborne receiver, apparatus to permit transmitting and receiving a Morse Code identification of the station transmitting the beams comprising: a. a code wheel having alternate opaque and clear areas representing the statIon code; b. means to rotate said wheel; c. a light source on one side of said wheel; d. a photodetector on the other side of said wheel opposite said light source; e. an inverter coupled to the output of said detector whereby said detector output provides a first logic signal and said inverter output provides a second logic signal; f. an oscillator; g. a first AND gate having said oscillator output and said first signal as inputs; h. a first divider, adapted to divide by a first number, obtaining its input from said first AND gate and providing an output at a first frequency; i. a second AND gate having said oscillator output and said second signal as inputs; j. a second divider adapted to divide by a second number obtain its input from said second AND gate and providing an output at a second frequency; k. an OR gate having the outputs of said first and second dividers as input and providing its output as a beam switching input to the transmitter; l. a bandpass filter in the airborne receiver countered at the second harmonic of said first frequency and having its input coupled to one of the local oscillator mixer outputs of the receiver; m. a detector coupled to the output of said filter to provide an output when its input exceeds a value indicative of signal reception at one of said first frequency and second harmonic; n. an audio tone generator; and o. a sound transducer coupled to said tone generator to provide an aural tone output.

Claim 9

In a microwave landing system of the type wherein a left localizer, upper glideslope, right localizer, and lower glideslope beam are switched on and off in sequence, for reception by an airborne receiver, a method to permit transmitting and receiving a Morse Code identification of the station transmitting the beams comprising: a. switching the beams at a frequency to represent a mark and at a second frequency to represent a space; and b. decoding said first frequency in the airborne receiver to provide a signal to key an audio tone generator.

Claim 10

In a microwave landing system of the type wherein a left localizer, upper glideslope, right localizer, and lower glideslope beam are switched on and off in sequence, for reception by an airborne receiver, a method to permit transmitting and receiving a Morse Code identification of the station transmitting the beams comprising: a. switching the beams at a frequency to represent a mark and at a second frequency to represent a space; and b. decoding said first frequency in the airborne receiver to provide a signal to key an audio tone generator.

Claim 11

The method of claim 7 wherein said decoding is done by passing the output of one of the local oscillator mixers in the receiver through a bandpass filter centered at the second harmonic of said first frequency.

Claim 12

The method according to claim 8 wherein the filter is coupled to the localizer local oscillator mixer output.