Patent US3810181A successfully refreshed from Google Patents.
US3810181A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low cost guidance receiver
Assignee: Singer Co
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Filing: 1973-01-02
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Granted: 1974-05-07
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Expires: 1993-01-02
Abstract
Abstract A low cost airborne set for a microwave landing system in which a voltage controlled oscillator only accurate to within two channels is used for tuning. The oscillator, after selection of a desired channel on the control panel is scanned by a ramp voltage and, upon receiving a proper microwave signal, an AFC loop closed to hold the signal. The beams of the transmitter are switched at a variable rate to transmit a Morse Code identifying number which is decoded upon receipt and compared with the selected channel number. If a comparison results, the AFC remains in and the instruments are enabled. If the wrong station is being received, the AFC is removed and scanning resumed until the next signal is received and the process repeated until the proper channel is obtained.
Inventors
- 👤 P Tierney
- 👤 A Lohman
- 👤 D Andrus
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:32
CPC Classifications
G; G01; G01S; G01S1/00; G01S1/02
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
336 words
In a microwave landing system of the type wherein a plurality of beams are transmitted in sequence to define a path to be followed when landing an aircraft, the switching rate of said beams being varied to transmit at least one coded character identifying which of several possible channels is being transmitted and wherein there is provided an airborne receiver comprising at least means to process the received beams to provide a localizer and a glide slope output signal, said receiver including a local microwave oscillator which is tuneable to one of several channels, apparatus to permit using a low accuracy voltage controlled oscillator in the receiver comprising: a. channel selection means providing as outputs a first voltage which will tune the local oscillator to within a predetermined number of channels from the selected channel and a digital word indicative of the channel selected; b. a ramp sweep generator providing an output which will sweep over a range of voltages representing plus and minus said predetermined number of channels; c. means to sum the output of said sweep generator and said first voltage and to provide said sum as a control input to oscillator; d. means to detect the presence of any one of the localizer and glide slope outputs in said receiver, and to provide an output indicative thereof; e. automatic frequency control (AFC) means; f. means responsive to said detector output to cause the voltage output at said sweep generator to be held and to be controlled by said automatic frequency control means; g. means to decode and store in digital form the identifying character in said transmitted signal; and h. means having said decoder output and said digital word as inputs to compare said decoder output with said digital word and to provide one output if the two inputs are the same and another output if the two inputs are different; i. said means responsive to the detector output being responsive to said another output to cause said sweep generator to resume scanning.
Claim 2
Dependent Claim
336 words
In a microwave landing system of the type wherein a plurality of beams are transmitted in sequence to define a path to be followed when landing an aircraft, the switching rate of said beams being varied to transmit at least one coded character identifying which of several possible channels is being transmitted and wherein there is provided an airborne receiver comprising at least means to process the received beams to provide a localizer and a glide slope output signal, said receiver including a local microwave oscillator which is tuneable to one of several channels, apparatus to permit using a low accuracy voltage controlled oscillator in the receiver comprising: a. channel selection means providing as outputs a first voltage which will tune the local oscillator to within a predetermined number of channels from the selected channel and a digital word indicative of the channel selected; b. a ramp sweep generator providing an output which will sweep over a range of voltages representing plus and minus said predetermined number of channels; c. means to sum the output of said sweep generator and said first voltage and to provide said sum as a control input to oscillator; d. means to detect the presence of any one of the localizer and glide slope outputs in said receiver, and to provide an output indicative thereof; e. automatic frequency control (AFC) means; f. means responsive to said detector output to cause the voltage output at said sweep generator to be held and to be controlled by said automatic frequency control means; g. means to decode and store in digital form the identifying character in said transmitted signal; and h. means having said decoder output and said digital word as inputs to compare said decoder output with said digital word and to provide one output if the two inputs are the same and another output if the two inputs are different; i. said means responsive to the detector output being responsive to said another output to cause said sweep generator to resume scanning.
Claim 3
Dependent Claim
14 words
The invention according to claim 1 wherein said predetermined number of channels is two.
Claim 4
Dependent Claim
25 words
The invention according to claim 1 wherein said at least one coded character includes a number coded in Morse Code identifying the channel being transmitted.
Claim 5
Dependent Claim
86 words
The iNvention according to claim 3 wherein a space is transmitted at a first frequency and a dot or dash at another frequency and said means to decode comprise: a. means to detect said second frequency and provide an output when said frequency is being received; b. a shift register; and c. means to load into said shift register a one when said frequency lasts for a time period representing a dash and a zero when said frequency lasts for a time period representing a dot.
Claim 6
Dependent Claim
169 words
The invention according to claim 4 wherein said first frequency is higher than said second frequency and said means to detect said second frequency comprises: a. a first retriggerable one shot having the received signal as an input and having a time constant longer than the time between pulses at said first frequency but shorter than the time between pulses at said second frequency whereby said one shot will have an inverted output which will be at zero when said first frequency is input and an output at said second frequency when said second frequency is input; and b. a second retriggerable one shot having the inverted output of said first one shot as an input and having a time constant longer than the time between pulses at said second frequency whereby the output of said one shot will be high in response to said second frequency being input and zero in response to the zero input resulting from said first frequency being input to said first one shot.
Claim 7
Dependent Claim
138 words
The invention according to claim 5 wherein the localizer and glide slope signals provided in said receiver comprise a first pair of localizer and a second pair of glide signals and further including: a. a band pass filter limiter having said first and second pairs of signals as inputs and providing an output containing any and all signals present at its input; and b. a third one shot having a time constant slightly less than the time between two pulses on any one of said input signals at said first frequency having the output of said limiter as an input and providing its output to said detecting means whereby, when more than one of said signals is present, only the first signal to be received will trigger said one shot thereby providing an output at the proper frequency.
Claim 8
Dependent Claim
40 words
The invention according to claim 4 and further including a keyed audio oscillator and a speaker, said oscillator being keyed by said detector output and providing its output to said speaker thereby providing an aural indication of the received code.
Claim 9
Dependent Claim
84 words
The invention according to claim 4 wherein said means to load comprises a first single shot multivibrator having an output pulse of a length less than the length of a dash but greater than a length of a dot, the trailing edge of said pulse being provided as a shift input to said shift register, the output of said means to detect providing its leading edge as a triggering input to said single shot and said pulse being a data input to said register.
Claim 10
Dependent Claim
69 words
The invention according to claim 4 wherein said code further includes a plurality of letters in addition to said number, a space larger than the space between dots and dashes in each letter being transmitted between each of said number and letters and further including means to detect a number and to enable said comparator output only in response to a decoded number being loaded into said shift register.
Claim 11
Dependent Claim
173 words
The invention according to claim 9 wherein said detecting and enabling means comprise: a. a module 5 counter providing an output each time its count reaches five; b. a second single shot having the output of said frequency detector as in input and providing an output at a first level for as long as the space between inputs does not exceed the space between dots and dashes and providing said output to the reset input of said counter, said counter being responsive to reset upon the change of said single shot output from said first level to a second level when a longer space occurs; c. a flip-flop; d. means to set said flip-flop in response to the simultaneous presence of said comparator one output and said counter output and to reset said counter in response to said comparator another output and said counter output whereby said one output will be transferred to said flip-flop set output only when said counter reaches a count of five in response to a number being received.
Claim 12
Dependent Claim
147 words
The invention according to claim 1 wherein said ramp sweep generator and said responsive means comprise: a. an integrator having an input and an output and providing said output to said summing means; b. means to reset said integrator whenever said output exceeds a pre-determined valve; c. a first resistor coupling the input of said integrator to a referenced voltage, said resistor selected to provide a first time constant in said integrator; d. a switch coupling said integrator input through a second resistor to the output of said automatic frequency control circuit, said second resistor selector to provide a second time constant in said integrator at least an order of magnitude shorter than said first time constant; and e. means to close said switch in response to an output from said detecting means and to open said switch in response to said another output from said comparator.
Claim 13
Dependent Claim
94 words
The invention according to claim 11 wherein said means to reset said integrator comprises a single shot having the output of said integrator as an input and adjusted to trigger at said pre-determined level and providing its output at a polarity opposite that of said reference through a third resistor to the input of said integrator, the length of said pulse being such that, for the time constant of said integrator through said third resistor, it will provide said output for a time sufficient to cause said integrator to integrate to its reset point.
Claim 14
Dependent Claim
59 words
The invention according to claim 11 wherein said means to close said switch comprise: a. a flip-flop providing its set output to close said switch; b. means to set said flip-flop in response to the output of said detector means indicative of a received signal; and c. means to reset said flip-flop in response to said comparator another output.
Claim 15
Dependent Claim
51 words
The invention according to claim 13 wherein said AFC control means provides a signal output which is provided to said switch and further provides a logic output indicating it is operating in the proper range and further including means to enable said detector means only when said logic output is present.
Claim 16
Dependent Claim
104 words
The invention according to claim 14 wherein said enabling means comprise an AND gate having said logic output and said detector output as inputs and providing its output to set said flip-flop and further including a one shot having a trigger input responsive to said detector output, a second AND gate having the inverted output of said one shot and said another output as inputs an providing its output to reset said flip flop, said one shot having a time constant longer than the time to make a comparison whereby said flip-flop cannot be reset during the period when a comparison is being made.
Claim 17
Dependent Claim
174 words
In a switched beam microwave landing system, a method of transmitting and decoding signals so that a low accuracy local oscillator may be used in the receiver comprising: a. switching the transmitted beams such that the switching rate transmits a Morse Code identifying group of characters identifying the microwave channel; b. providing a low accuracy voltage controlled oscillator (VCO) in the microwave receiver; c. providing a nominal input voltage to said VCO corresponding to a desired channel; d. developing a ramp scan voltage having a range corresponding to plus and minus the oscillator accuracy and adding said ramp voltage to said nominal voltage; e. detecting the presence of any received channel; f. closing an automatic frequency control (AFC) loop in response to detecting a channel; g. decoding and storing the transmitted Morse Code channel number; h. comparing said stored number with the desired channel number; and i. maintaining said AFC loop closed when said two numbers are the same and opening said loop to resume scanning when said two numbers are not the same.
Claim 18
Dependent Claim
174 words
In a switched beam microwave landing system, a method of transmitting and decoding signals so that a low accuracy local oscillator may be used in the receiver comprising: a. switching the transmitted beams such that the switching rate transmits a Morse Code identifying group of characters identifying the microwave channel; b. providing a low accuracy voltage controlled oscillator (VCO) in the microwave receiver; c. providing a nominal input voltage to said VCO corresponding to a desired channel; d. developing a ramp scan voltage having a range corresponding to plus and minus the oscillator accuracy and adding said ramp voltage to said nominal voltage; e. detecting the presence of any received channel; f. closing an automatic frequency control (AFC) loop in response to detecting a channel; g. decoding and storing the transmitted Morse Code channel number; h. comparing said stored number with the desired channel number; and i. maintaining said AFC loop closed when said two numbers are the same and opening said loop to resume scanning when said two numbers are not the same.
Claim 19
Dependent Claim
90 words
The invention according to claim 16 wherein the Morse Code group of characters includes a number and a plurality of letters and further including the steps of: a. transmitting a space between each of said letters and said number greater than the space between characters in a letter and number; b. detecting said space to detect the beginning of each letter and number; c. counting the number of characters in each number and letter, d. perform the step of comparing only when the number of characters ie equal to five.
Claim 20
Dependent Claim
27 words
The invention according to claim 17 wherein said oscillator is accurate to two channels and said ramp voltages scans a range of plus and minus two channels.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-06 | 1977-11-05 | 1978-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-06 | 1981-11-05 | 1982-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-06 | 1985-11-05 | 1986-05-07 | $7700.00 | Window Closed / Lapsed |