Patent Application
20060217145
The invention relates to a secure wireless communication system. More specifically, the present invention relates to a system for an improved system and method for wireless communication between two locations, and the wireless monitoring of one location from a second location.
Wireless communication in the abstract has been known and popular for some time. In recent years, various improvements in radio transmission bandwidth and signal strength have enhanced the number and type of wireless communication systems available to consumers. An exemplary wireless monitoring system is disclosed in U.S. Pat. No. 6,759,961 to Fitzgerald et al. Various other exemplary wireless monitoring systems are currently offered for sale by Fisher-Price, among others.
Wireless monitoring systems can be used for a variety of purposes, such as home security, intercom devices, and law enforcement. Another application particularly suited for wireless monitoring systems is a baby monitor, in which a transmitting device is positioned at the location of an infant, for example, a baby crib, and captures noises made by the infant. A receiving device is positioned elsewhere, such that a parent can attend to other duties while listening to the sounds transmitted from the infant's location.
One shortcoming of present wireless monitoring systems is that the sound data transmitted from the transmitting device to the receiving device is typically in analog form. For example, the sound is in the standard analog waveform, and is therefore subject to standard waveform degradation. In such systems, owing to analog signal degradation, the quality of the sound received by the receiver will be inherently less than the quality of the sound sent by the transmitter. Across a substantial distance, the reduction in sound quality can be so substantial as to render the received sounds indistinguishable from background noise.
Another shortcoming of present wireless monitor systems is that they are susceptible to eavesdropping. The audio transmission between the transmitting and receiving devices is a standard radio transmission, which can be received by a standard radio reception device listening at the correct frequency. Such devices are notoriously insecure, and for the same reason can interfere with other radio transmissions such as a wireless phone or stereo system. Conversely, such wireless monitor devices receive interference from the other radio devices as well, sometimes requiring the user to place the devices in awkward places to avoid interference.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior systems and/or methods of this type. A full discussion of the features and advantages of the present invention is deferred to the detailed description, which proceeds with reference to the accompanying drawings.
A secure wireless communication system is provided comprising a transmitter and a receiver. The transmitter has an input for receiving audio information and a filter for modifying the audio information. The transmitter further comprises a selector for selecting a radio frequency, and an antenna for transmitting the modulated audio information on the selected radio frequency carrier. The receiver has an antenna for receiving the modulated audio information from the transmitter, and a filter for modifying the audio information. The receiver further comprises an output for communicating the audio information.
It is an object of the present invention to provide a wireless communication system that will both transmit and receive audio information having a higher sound quality than systems known in the art. To that end, the transmitter of the present system is, in one embodiment, provided with a converter to convert captured analog sound to a digital equivalent prior to transmission. Conversely, the receiver in that embodiment is provided with a converter for converting the received digital audio information into an analog form prior to communicating the information to the sound output.
It is a further object of the present invention to provide for a wireless communication system for the secure transmission of audio information. In an embodiment, the transmitter of the present system is provided with a translator for translating the audio information into an encrypted audio information prior to transmission. Likewise, in that embodiment, the receiver is provided with a translator for translating received encrypted audio information into non-encrypted audio information, prior to communicating the information to the sound output.
In an embodiment, the transmitter of the present invention is provided with an amplifier to amplify the audio information captured by the input, thereby increasing the sound quality and dynamic range of the captured audio information. Preferably, the receiver is also provided with an amplifier for further improving the sound quality and volume level of the audio information.
It is a further object of the present invention to provide a wireless communication system that will have a greater range of transmission capability from the transmitter to the receiver. In an embodiment, the transmitter is provided with a radio frequency (“RF”) power amplifier for increasing the distance over which the transmitter can transmit the audio information. Preferably, the receiver also comprises a low noise amplifier (“LNA”) for further increasing the operable distance at which the receiver can receive transmissions from the transmitter.
It is a further object of the present invention to provide a wireless communication system that will be less susceptible to interference from neighboring radio frequency devices, and will be less likely to provide interference for those neighboring devices. In an embodiment, the transmitter is provided with a radio frequency filter for determining a radio frequency at which to transmit the audio information. Preferably, the receiver likewise comprises a radio frequency filter for receiving the audio information transmitted at the radio frequency selected by the transmitter.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.
To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:
While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.
Referring initially to
The transmitter 100 includes a filter 103, 106, 108, 110 for modifying the audio information and radio signal. As illustrated in
In another embodiment, the filter for modifying the audio information is a Gaussian low pass filter 106. A Gaussian low pass filter 106 in the present system is advantageous for use in an embodiment involving an analog-to-digital (“A/D”) converter 104. When analog audio information is converted to digital form, the resulting audio signal is a square waveform. A Gaussian low pass filter 106 can be used to “smooth” the edges of that digitized audio waveform, resulting in a waveform suitable for frequency modulation (“FM”). As will be understood by one of skill in the art, a Gaussian low pass filter 106 is essentially an equation applied upon the input audio information signal to approximate a Gaussian curve. The Gaussian low pass filter 106 is also useful for achieving radio transmission compliance with Part 15 of the rules of the Federal Communications Commission. While it is particularly advantageous to use the Gaussian low pass filter 106 in an embodiment with the A/D converter 104, it is to be understood that the Gaussian low pass filter 106 can also be used in the present invention without the A/D converter 104.
In another embodiment, the filter for modifying the radio frequency signal is a surface acoustic wave (“SAW”) filter 108. The purpose of the SAW filter 108 is to accept radio waves within a desired frequency range, while rejecting radio waves outside of the designed range. In any RF transmission, captured audio information will necessarily include information at undesirable frequencies, usefully heard by the user as a background static “hiss”. Furthermore, audio information transmitted at frequencies relatively close to each other, such as a cordless phone and a standard home radio receiver, can be more effectively isolated from each other by using the SAW filter 108, whereby interference from other radio frequency devices can be reduced.
As illustrated in
The transmitter 100 further comprises a selector for selecting a radio frequency at which to transmit the modulated audio information. The selected radio frequency can be pre-programmed into the transmitter 100, such that by default, the audio information will be transmitted at the selected radio frequency. In another embodiment, a selector switch is provided for the user to select a radio frequency, to which the frequency modulator 107 is tuned to frequency modulate and transmit the digitized audio information.
The transmitter 100 further comprises an antenna 111, which is used to radiate electromagnetic waves at the selected frequency. Antenna 111 converts radio frequency electrical energy to radiated electromagnetic energy. The size of antenna 111 is determined by the frequency of the signal to be transmitted. In a preferred embodiment, a wire cut to one-half wavelength is sufficient for the purposes of the present invention.
In one embodiment, the transmitter 100 further comprises an A/D converter 104, which converts the captured analog audio information to a digital signal representing equivalent information. As will be understood by one of skill in the art, A/D converter 104 samples and stores a plurality of data points of the amplitude of the captured input analog audio information, and based on those stored sample points, creates a digitally equivalent signal. It will be further understood by those of skill in the art that in the present invention, a variety of A/D conversion algorithms can be used without departing from the principles of the invention, including Delta-Sigma, CVSD, ADPCM, PCM, uLaw, aLaw and the like.
In one embodiment, the transmitter 100 further comprises a microcontroller 105, which is used to control the routing of data through the various electrical components of the transmitter 100. As illustrated in
As illustrated in
In one embodiment, and as illustrated at step 204, error checking information can be added as meta-data to the data packet awaiting transmission. It will be appreciated by one of skill in the art that a variety of encryption and error-checking algorithms can be used with the present invention without departing from the principles thereof. Encryption is useful in the present invention, so as to avoid surreptitious eavesdropping upon the transmissions from the transmitter 100. Error checking is useful in the present invention, so as to provide a way for the receiver 300 to ensure that all of the data transmitted by the transmitter 100 was actually received.
Referring again to
Another amplifier for use in the transmitter 100 is a radio frequency power amplifier 109, which boosts the voltage level or power level of a signal, thereby creating a linear replica of the input signal, but with enhanced power level prior to transmission. The purpose of the power amplifier 109 is to increase the signal strength of the transmitter 100, and thus enhance both the distance at which transmitter 100 and receiver 300 may effectively communicate, and increase the clarity of the audio information received by receiver 300. The output signal from the power amplifier 109 may also be a non-linear analog function of the input signal. As illustrated in
In one embodiment, transmitter 100 further comprises a voltage control oscillator 107, which changes its frequency according to a control input, thereby creating a radio frequency carrier signal. The voltage control oscillator 107 optionally includes a radio frequency modulator, which in turn modulates the frequency of the voltage control oscillator 107 output, thereby creating a frequency-modulated signal for FM transmission. Voltage control oscillator 107 and radio frequency modulator are preferably, and as illustrated, contained in the same discrete electronic component, but may be separated without departing from the principles of the present invention.
Referring to
The receiver 300 further comprises a filter 313, 315, 301. In one embodiment, the filter 313 is a radio frequency SAW filter 313, 315, discussed previously in the context of the transmitter 100. As in the transmitter 100, the SAW filter 313, 315 in the receiver 300 is for isolating a desired range of radio signal information from background noise, thereby increasing the clarify and range of the audio information. As illustrated in
The low noise amplifier 314 is provided in one embodiment, to enhance the strength of signals received from the transmitter 100, thereby increasing the operative distance at which transmitter 100 and receiver 300 may communicate. Amplifier 314 can be constructed of a discrete radio frequency transistor, or of MMIC amplifiers. In another embodiment, the receiver 300 further comprises an audio amplifier 320, for increasing the amplitude of the audio information before it is transmitted to the audio output 321. To adjust the sound level of the audio output 321, the audio amplifier 320 may be operably driven by a volume control operable by the user. Audio amplifier 320 is preferably, as will be understood by one of skill in the art, an integrated circuit device optimized for high audio voltage gain, with the ability to drive the low impedance of a standard speaker coil.
In a preferred embodiment, the receiver 300 further comprises a radio frequency receiver circuit 316, which detects, demodulates and amplifies received radio frequency signals. The radio frequency receiver circuit in turn comprises a voltage control oscillator 301, a radio frequency mixer 302, a filter 303 and a signal detector 304. As will be understood by one of skill the art, the radio frequency receiver circuit 316 is for selecting from among the electromagnetic information received by the antenna 312 the audio information transmitted at the selected frequency by the transmitter 100. Exemplary radio frequency receiver circuits for use in the present invention are available as model no. ML2722 from Micro Linear and model no. BH4127 from ROHM.
In one embodiment, the receiver further comprises a microcontroller 317, for routing information between the various electrical components of the receiver 300, and for performing various data operations upon the received audio information. Referring now to
In the preferred event that the audio information transmitted from the transmitter 100 was encrypted, the microcontroller 317 next, at step 404, decrypts the encrypted audio information. Information necessary for decrypting the encrypted audio information may be pre-programmed into the microcontroller 317, or may be included in the meta-data of the transmitted audio information packet. In the preferred event that the meta-data associated with the audio information packet includes error checking information, the microcontroller 317 next, at step 405, uses that error checking information to verify that the audio information received from the transmitter 100 is received from error. The algorithms necessary for performing the decryption and error checking have been discussed in referenced to the transmitter 100, and will be understood by one of skill in the art. Lastly, at step 406, the microcontroller transmits the decrypted audio information to the next element in the electrical assembly of the receiver 300.
In one embodiment, the receiver 300 further comprises a digital-to-analog (“D/A”) converter 316, for translating received digital audio information into analog audio information so that it may be communicated to the audio output 321. Preferably and as previously discussed and as illustrated in
The receiver 300 further comprises an output 321. In a preferred embodiment, the audio output 321 is a standard speaker, an electro-acoustic transducer for converting electrical signals into sound audible by the user. In the preferred embodiment, the speaker 321 has an impedance between 8 and 32 ohms at up to 1 watt of voltage. Audio output 321 can also be an audio output port, such as a quarter-inch or eighth-inch stereo output port, or RCA output port.
As illustrated in
While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.
