# Patent

## Title
Apparatus and methods of accessing all channels of a superheterodyne receiver simultaneously

## Abstract

An apparatus and method associated with exploiting a characteristic in super-heterodyne receivers such that a modulated signal will be received on all channels simultaneously regardless of the channel selected on the receiver.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/842,715, filed Jul. 3, 2013, entitled “Apparatus and Methods of Accessing All Channels of a Superheterodyne Receiver Simultaneously,” the disclosure of which is expressly incorporated by reference herein.


STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used and licensed by or for the United States Government for any governmental purpose without payment of any royalties thereon. This invention (Navy Case 102,716) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Technology Transfer Office, Naval Surface Warfare Center Crane, email: Cran_CTO@navy.mil.


BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to interaction with an electronics system. One example can include simultaneously accessing all channels of a superheterodyne audio receiver of interest. Using methods and apparatus in accordance with examples of the invention, a modulated signal can be received or detected simultaneously on all channels of a receiving device that employs a superheterodyne design, regardless of the channel selected on the receiving device.
An exemplary embodiment of the present invention relates to one or more apparatuses and methods operable for simultaneously accessing all channels of a superheterodyne receiver. Using exemplary aspects of the invention including methods and apparatus described herein, a transmitted signal can be received or detected at a receiving device that employs a superheterodyne design as long as the radio is powered on.
One aspect of an exemplary embodiment of the invention includes an aspect enabling a system to be directional, affecting only selected devices or omni-directional affecting all devices of targeted design within range.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.



BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description of the drawings particularly refers to the accompanying figures in which:
FIG. 1 shows an exemplary diagram where an exemplary device in accordance with one embodiment of the invention might be used;
FIG. 2 shows an exemplary diagram of a front end of a receiver to illustrate how an one example of an interaction with a receiver;
FIG. 3 shows a functional schematic in accordance with one embodiment of the invention;
FIG. 4 shows a power to frequency chart showing relationships of modulated and unmodulated frequencies in accordance with one embodiment of the invention;
FIG. 5 shows an exemplary schematic description of a system in accordance with one embodiment of the invention;
FIG. 6 shows an exemplary method in accordance with one embodiment of the invention; and
FIG. 7 shows another exemplary method in accordance with another embodiment of the invention.



DETAILED DESCRIPTION OF THE DRAWINGS
The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention.
Referring initially to FIG. 1, illustrates an exemplary situation where an embodiment of the invention, not shown in this figure (e.g. see FIG. 4), might be used. In this exemplary situation, a temporary controlled air space 2 has been declared and a small aircraft 4 is approaching this airspace. An employee or agent of an activity seeking to influence entities within or related to this controlled airspace attempts to hail the small aircraft 4. However, communication bands of aviation radios have over 800 channels and agent or employee does not know what channel the small aircraft 4 pilot is monitoring. The agent or employee can hail the pilot on all channels simultaneously using an exemplary embodiment of the invention. An exemplary omni-directional antenna 6 can be used with the invention to create a hemispherical transmission/reception zone where the size of the zone can be dependent upon such an antenna's transmitter power within the controlled airspace 2 with an un-modulated frequency. A pilot would not receive comprehensible messages or information on an aircraft radio from a signal where an unmodulated signal or frequency is used. A directional antenna 3 can be adapted to transmit a narrow beam 5 at a desired aircraft e.g., aircraft 4 within the controlled airspace 2. This narrow beam can be modulated with a message and may extend outside of the zone created by the omni-directional antenna 6, but only the aircraft 4 that receives both frequencies, i.e. is within the zone created by the omni-directional antenna 6 transmitting the first frequency and is within the directional antenna transmitting the narrow beam 6 on a second frequency will receive a desired message as well as resulting in the aircraft 4 receiving the message on all channels simultaneously.
FIG. 2 shows an exemplary embodiment, e.g., a typical superheterodyne receiver. The following two figures provide an exemplary description for interacting with a superheterodyne receiver. The examples provided herein may be amenable to several heterodyne based radios. An embodiment of the invention can be used on the super-heterodyne architecture. Multiple stage super-heterodyne receivers are variations on a basic super-heterodyne receiver. Receivers, such as discussed herein, have a similar or same front end and are susceptible to a same or similar interaction with an exemplary embodiment of the invention. The exemplary system shown in FIG. 2 includes a receiver antenna 7. The exemplary FIG. 2 system also includes an initial band pass filter 8 which only allows RF frequencies received by the antenna that are in a desired band to pass through. In this example, a system is shown using a civilian aviation communications band of 118 to 137 MHz. An exemplary system can also utilizes a reference frequency F2 supplied by a local oscillator, in this example 139.4 to 158.4 MHz. A mixer 9 takes signals that pass through a filter 8, referred to as F2, and mixes the signals with a local oscillator frequency referred to as F1 and outputs F1+F2 and F1−F2. An IF band pass filter 11 can be provided which, in this exemplary embodiment, is a very narrow filter set at a desired intermediate frequency (IF) (e.g., in this example it is centered at 21.4 MHz). In this example, since this filter only allows the narrow band of 8 to 25 KHz centered at 21.4 MHz into an IF stage, a user can select which input frequency or channel they want by adjusting the local oscillator frequency. In one example, to select the 118 MHz channel, a user or system can tune the local oscillator to 139.4 MHz then F1−F2=139.4−118=21.4 MHz. If a user desires a 136 MHz channel, the user or system will then tune the local oscillator to 158.4 MHz and F1−F2=158.4−136=21.4 MHz. In another example, where a user or system tunes a local oscillator to a frequency of 21.4 MHz higher than the desired frequency then the difference will be 21.4 MHz and only that frequency will pass through the IF band pass filter.
FIG. 3 describes an interaction in accordance with an embodiment of the invention. In one embodiment, a basic aspect of design that super-heterodyne receivers relies upon relates to supplying an internal un-modulated frequency, sometimes known as a local oscillator signal, to mix with all frequencies received by an antenna that pass through an initial band pass filter; only a received frequency that mixes to yield F1−F2=IF passes on to IF circuitry. In this example radio, an IF is 21.4 MHz. One exemplary interaction used herein provides one or more continuous wave (CW) tones (un-modulated transmitted signals) and a modulated signal that, when mixed, can result in a desired IF frequency. In this example, an initial band pass filter is a single order filter with corners at 118 and 137 MHz. With a single order filter frequencies set at half the lower corner or twice the upper corner are attenuated to one half the power of the pass band so that signals at frequencies between these half power points and the corner frequencies can still get to the mixer; such signals require an additional transmitting power. In this example, F1 and F2 are both received by an antenna 12, F1 is a CW signal set in an upper corner of the band pass filter 13, and F2 is a modulated frequency set in the lower corner of this filter and they are separated by the IF frequency of 21.4 MHz, then when these input signals are mixed in the mixer, F1−F2 will be equal to the IF frequency.
Referring to FIG. 4, in this example, a CW unmodulated frequency 16 can be set at 137.7 MHz and a modulated frequency 17 can be set at 113.3 MHz. An IF 18 can then be determined as 137.7 MHz−116.3 MHz=21.4 MHz. In this example the two selected frequencies are just barely in the shoulders of the band pass filter, so very little attenuation will result from operation of this exemplary system. Low attenuation results in this case can be expected when this example is used with many aviation radios given designers of such radios generally select a low IF frequency (<30 MHz) and such an aviation communications band that the filter must pass is specified by standard as 19 MHz.
FIG. 5 shows an implementation of an exemplary interaction system with an example radio. An embodiment of the invention can include an RF signal generator 19 set at frequency F1, e.g., 137.7 MHz. An RF signal generator 20 can be set at, e.g., 116.3 MHz. An audio signal selector 21 can allow a user to select a tone, a recorded message, or live audio from a microphone for use to modulate a signal F1. The RF modulator 22 modulates audio onto a desired RF signal. An omni-directional antenna 23 transmits a CW signal roughly covering a zone or bubble such as, e.g., shown in FIG. 1. A directional antenna 24 illuminates a target aircraft with a modulated F2 signal.
Alternative embodiments can include multiple CW tone frequencies for cases where two frequencies within the initial pass band do not exist for which F1−F2 or F1+F2 is equal to an IF frequency. In this example, if three frequencies are used then a mixer output comprises triplets F1+F2+F3, F1+F2−F3, F1−F2+F3, F2+F3−F1, F1−F2−F3 as well as couplets F1−F2, F1+F2, F1−F3, F1+F3, F2−F3 and F2+F3 where F1, F2 and F3 are all in the pass band and F1 is larger than F2 and F2 is larger than F3 and only one frequency is modulated.
FIG. 6 shows a method of communicating with an entity having an unknown selection of radio communication channel setting in accordance with one embodiment of the invention. At step 101, detecting an unauthorized aircraft comprising a superheterodyne communication architecture system comprising a band pass filter and intermediate frequency filter. At step 103, determining the aircraft location and bearing. At step 105, selecting at least a first and second frequency or channel to respectively broad cast an omnidirectional signal and a directional signal, wherein the first and second frequency or channel is selected based on one or more design parameters of the superheterodyne receiver architecture system, the one or more design parameters comprising frequencies which said superheterodyne receiver architecture system will not reject using said band pass filter or another filter. The first and second frequency or channels are also determined based on an intermediate frequency at the band pass filter frequency of said superheterodyne receiver architecture system. The intermediate frequency determines a separation between a frequency separation between the first and second frequency. At step 107, orienting the directional signal towards the unauthorized aircraft and maintaining the aircraft within the directional signal beam path during a period to transmit a message to the unauthorized aircraft. At step 109, modulating and transmitting one of the directional signal or the omnidirectional signal with the message for the period to transmit the message. In one embodiment of the invention, one of the omnidirectional signal or direction signal comprises of multiple frequencies. Another embodiment can add a step of selecting additional frequencies or channels to generate additional frequency products within a one or more band pass filters of the superheterodyne communication architecture systems for matching different respective intermediate frequencies.
FIG. 7 shows another alternative method of communicating with an entity having an unknown selection of radio communication settings in accordance with another embodiment of the invention. At step 201, communicating with an unauthorized aircraft comprising a superheterodyne communication architecture system comprising a band pass filter and intermediate frequency filter. At step 203, generating a library of sets of the first and second frequencies or channels associated with different said superheterodyne communication architecture systems, each of the first and second frequencies or channels operable for respectively broadcasting an omnidirectional signal and a directional signal, wherein each set of the first and second frequencies or channels is selected based on one or more design parameters of a particular one of the different said superheterodyne communication architecture systems, the one or more design parameters comprising frequencies which the superheterodyne communication architecture system will not reject using the band pass filter or another filter, the sets of the first and second frequency or channels are also determined based on an intermediate frequency at each the band pass filter of each the different said superheterodyne communication architecture systems, wherein each the intermediate frequency determines a separation between the first and second frequency. At step 205, selecting one of the sets of the first and second frequencies. At step 207, orienting the directional signal towards the unauthorized aircraft and maintaining the aircraft within the directional signal beam path during a period to transmit a message to the unauthorized aircraft. At step 209, modulating and transmitting one of the directional signal or the omnidirectional signal with the message for the period to transmit the message using said one of the sets of the first and second frequencies. An alternative embodiment can have one of the omnidirectional signal or direction signal comprises of multiple frequencies. Another alternative embodiment can include selecting additional frequencies or channels to generate additional frequency products within a one or more band pass filters of the superheterodyne communication architecture systems for matching different respective intermediate frequencies. An alternate embodiment can include a case wherein the modulation is other than amplitude modulation such as frequency, phase or any of the other digital or analog modulation schemes such as phase shift key or asymmetric phase shift key.
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.

## Claims

1. A method of communicating with an entity having an unknown selection of radio communication channel setting, comprising:
detecting an unauthorized aircraft comprising one of a plurality of superheterodyne communication architecture systems, each of said superheterodyne communication architecture systems comprising a band pass filter type with a first frequency range associated with aircraft communications bands and one of a plurality of different intermediate frequency filter types each associated with different superheterodyne radio architectures, wherein each of said band pass filter type and ones of associated said plurality of different intermediate frequency filter types are respectively associated with each of said plurality of superheterodyne communication architecture systems;
determining the unauthorized aircraft's location and bearing using an aircraft location detection system;
selecting a first of said plurality of superheterodyne communication architecture systems comprising said band pass filter and a first intermediate frequency filter type of said plurality of different intermediate frequency filter types;
selecting at least a first frequency or channel and a second frequency or channel configured for respectively broadcasting a first omnidirectional signal from a first omnidirectional antenna and a directional signal from a directional antenna, wherein said first frequency or channel and said second frequency or channel is selected based on one or more design parameters of said first of said plurality of superheterodyne receiver architecture systems, said one or more design parameters of said first of said plurality of superheterodyne receiver architecture systems comprising frequencies which said first of said plurality of superheterodyne receiver architecture systems will not reject using said band pass filter type or said first intermediate filter type of said plurality of different intermediate frequency filter, said first frequency or channel and said second frequency or channel are also determined based on a mixer product that results in a first intermediate frequency that will pass through said first intermediate frequency filter type, wherein said first intermediate frequency is further determined based on determining a frequency range separation between said first frequency or channel and second frequency or channel by differencing said first frequency or channel from said second frequency or channel to determine an absolute value difference that defines said first intermediate frequency that is equivalent to said frequency range separation;
broadcasting said first omnidirectional signal from a omnidirectional antenna;
orienting a beampath of said directional signal towards said unauthorized aircraft and maintaining said aircraft within said beampath of said directional signal during a period to transmit a message to said unauthorized aircraft; and
modulating and transmitting said directional signal with said message for said period to transmit said message so as to mix said first omnidirectional signal and said directional signal at said unauthorized aircraft's location during said period to transmit said message.

2. A method as in claim 1 further comprising selecting a third frequency or channel to broadcast a second omnidirectional signal if no radio response is received from said unauthorized aircraft in response to said message during or after said message period, wherein said third frequency or channel is selected based on one or more frequencies that a second of said plurality of superheterodyne receiver architecture systems will not reject using said band pass filter type, wherein said second of said plurality of superheterodyne receiver architecture system comprises one said bandpass filter type and a second intermediate frequency filter type of said plurality of said intermediate frequency filter types, wherein said first, second, and third frequencies or channels are also determined based on predicted mixing of said first, second and third frequencies or channels after they pass through said band pass filter type to produce a second intermediate frequency associated with said second of said plurality of superheterodyne receiver architecture systems.

3. A method as in claim 1, wherein said step of determining the mobile vehicle's location and bearing is further determined based on a prediction of said mobile vehicles location based on prior observation or predicted path.

4. A method of communicating with an entity having an unknown selection of radio communication settings
communicating with an unauthorized aircraft comprising a superheterodyne communication architecture system comprising a band pass filter and one of a plurality of intermediate frequency filters associated with different superheterodyne communication architecture systems;
providing a library of sets of first frequencies or channels and second frequencies or channels each respectively associated with each said different superheterodyne communication architecture systems, each of said first frequencies or channels and second said frequencies or channels are selected to be operable for respectively broadcasting an unmodulated omnidirectional signal and a directional signal, wherein each set of said first frequency or channel and said second frequency or channel is selected based on one or more sets of design parameters associated with a particular one of said different said superheterodyne communication architecture systems, each set of said one or more design parameters comprising a frequency range that each associated said superheterodyne communication architecture system will not reject using said band pass filter or respective said intermediate frequency filter, said sets of said first frequencies or channels and second frequencies or channels are also determined based on one of a plurality of intermediate frequencies at each said intermediate frequency filter of each said different said superheterodyne communication architecture systems, wherein each said intermediate frequency is defined by a different separation between each set of said first and second frequencies;
selecting one of said sets of said first and second frequencies;
orienting said directional signal towards said unauthorized aircraft and maintaining said aircraft within said directional signal beampath during a period to transmit a message to said unauthorized aircraft; and
modulating and transmitting one of said directional signal with said message for said period to transmit said message using said one of said sets of said first and second frequencies.

5. A method as in claim 4, wherein one of said omnidirectional signal or directional signal comprises multiple frequencies.

6. A method of communicating with an entity having an unknown selection of radio communication channel setting, comprising:
detecting a mobile vehicle comprising one of a plurality of superheterodyne communication architecture systems, each of said superheterodyne communication architecture systems comprising a band pass filter type with a first frequency range associated with said mobile vehicle type's communications bands and one of a plurality of different intermediate frequency filter types each associated with different superheterodyne radio architectures, wherein each of said band pass filter type and ones of associated said plurality of different intermediate frequency filter types are respectively associated with each of said plurality of superheterodyne communication architecture systems;
determining the mobile vehicle's location and bearing using an mobile vehicle location detection system or a prediction of said mobile vehicles location based on prior observation or predicted path;
selecting a first of said plurality of superheterodyne communication architecture systems comprising said band pass filter and a first intermediate frequency filter type of said plurality of different intermediate frequency filter types;
selecting at least a first frequency or channel and a second frequency or channel configured for respectively broadcasting a first omnidirectional signal from a first omnidirectional antenna and a directional signal from a directional antenna, wherein said first frequency or channel and said second frequency or channel is selected based on one or more design parameters of said first of said plurality of superheterodyne receiver architecture systems, said one or more design parameters of said first of said plurality of superheterodyne receiver architecture systems comprising frequencies which said first of said plurality of superheterodyne receiver architecture systems will not reject using said band pass filter type, said first frequency or channel and said second frequency or channel are also determined based on a first intermediate frequency that will pass through said first intermediate frequency filter type, wherein said first intermediate frequency is further determined based on determining a frequency range separation between said first frequency or channel and second frequency or channel by differencing said first frequency or channel from said second frequency or channel to determine an absolute value difference that defines said first intermediate frequency that is equivalent to said frequency range separation;
broadcasting said first omnidirectional signal from a omnidirectional antenna;
orienting a beampath of said directional signal towards said mobile vehicle and maintaining said mobile vehicle within said beampath of said directional signal during a period to transmit a message to said mobile vehicle; and
modulating and transmitting said directional signal with said message for said period to transmit said message so as to mix said first omnidirectional signal and said directional signal at said mobile vehicle's location during said period to transmits said message.

7. A method as in claim 6, wherein said mobile vehicle is an aircraft.

8. A method as in claim 7, wherein said aircraft is an unauthorized aircraft that is entering a restricted area when said message is broadcast.

9. A method as in claim 6, further comprising selecting a third frequency or channel to broadcast a second omnidirectional signal if no radio response is received from said mobile vehicle in response to said message during or after said message period, wherein said third frequency or channel is selected based on one or more frequencies that a second of said plurality of superheterodyne receiver architecture systems will not reject using said band pass filter type, wherein said second of said plurality of superheterodyne receiver architecture system comprises one said bandpass filter type and a second intermediate frequency filter type of said plurality of said intermediate frequency filter types, wherein said first, second, and third frequencies or channels are also determined based on predicted mixing of said first, second and third frequencies or channels after they pass through said band pass filter type to produce a second intermediate frequency associated with said second of said plurality of superheterodyne receiver architecture systems.

10. A method of communicating with an entity having an unknown selection of radio communication channel settings, comprising:
determining a plurality of different first intermediate frequencies (IF) each respectively associated with one of a plurality of different superheterodyne communication architecture systems that may be installed in an aircraft, each of said plurality of superheterodyne communication architecture systems comprising a band pass frequency type with a first frequency range that allows a plurality of aircraft communications frequencies to pass through each of the band pass filter types;
identifying a plurality of frequency pairs each comprising a respective F1 and F2 frequency value, wherein each of said respective F1 and F2 frequency values respectively associated with each of said frequency pairs is within the plurality of aircraft communication frequencies that will pass through the band pass filter types, wherein each said frequency pairs are each further defined so that when any two F1, F2 pairs are respectively differenced, the differenced product for each pair is respectively equal to one of the plurality of different first IFs;
detecting a first aircraft entering a predetermined restricted airspace comprising one of said plurality of superheterodyne communication architecture systems;
determining the first aircraft's location and bearing from a point within a frame of reference using an aircraft location detection system;
selecting one of said plurality of frequency pairs each comprising a respective F1, F2;
selecting at a first and second transmission frequency each respectively equal to said one of said plurality of frequency pairs F1, F2;
transmitting an unmodulated omnidirectional first transmission signal at said first transmission frequency from an omnidirectional antenna;
orienting a beampath of a narrow beam directional antenna from said point within said frame of reference along said bearing towards said first aircraft and maintaining said first aircraft within said beampath during a first time period;
modulating and transmitting a second transmission signal from said narrow beam directional antenna within said beampath with a message during said first time period so as to mix said first transmission signal and said second transmission signal at said first aircraft's location as it transits during said first period; and
selecting a different first and second transmission frequency each respectively equal to a different one of said plurality of frequency pairs F1, F2 if an operator in said first aircraft does not respond to said message and repeating said transmitting orienting, modulating and transmitting steps using the different first and second transmission frequency.

11. A method as in claim 10, further comprising providing a library comprising said plurality of frequency pairs each associated with one of said plurality of different IFs that are each respectively associated with one of said plurality of different superheterodyne communication architecture systems, wherein said step of selecting first and second transmission frequencies further comprises selecting said first and second transmission frequencies from said library based on a retrieval of one or more said frequency pairs from said library.

12. A method as in claim 10, wherein said message comprises a tone, a recorded message, or live audio from a microphone.