Patent Application
20070126522
The present invention relates to signals having essentially no sidebands in a frequency domain. More particularly, it relates to control of communication systems that modulate/demodulate and/or transmit/receive such signals. In one aspect, hardware and software of devices such as transmitters and receivers are contemplated. In another, control is derived from a carrier upon which an input signal is impressed. In still another, control contemplates adjusting gain to effect modulation.
In the prior art, it has been fairly suggested that signals in communication systems can be transmitted and recovered without the signal having any substantial sidebands in the frequency domain. In this manner, communication bandwidth is greatly enlarged. This is not trivial, either. Bear in mind, the available spectrum, especially for radio, television, etc., is quite limited, quite expensive and exceptionally regulated by government entities.
Among some of the suggested features in the art, a sine wave carrier with a single frequency includes data impressed thereon per every half or full wave cycle of the sine wave. In one instance, data can be expressed as one amplitude for a binary zero and another, higher amplitude for a binary one per every half or full cycle of the sine wave. In another, data can be expressed as one amplitude for a 00 value, a higher amplitude for a 01 value, a still higher amplitude for a 10 value and a highest amplitude for a 11 value per every half or full cycle of the sine wave. In still another, binary data can be represented on a single frequency sine wave by turning the sine wave on or off after every full wave cycle thereof. Binary ones then represent the presence of the sine wave while binary zeros represent the absence of the sine wave. Still other data impression schemes include quantizing amplitudes of a data or information signal and resetting the amplitude of a single frequency carrier sine wave to match the quantized amplitudes per every full cycle of the carrier, especially when amplitudes of the carrier have relatively no energy, such as when it crosses the x axis of a mathematical representation of same.
Regardless of data transmission/reception scheme, communication systems involved with signals having no sidebands are fledgling designs that generally lack robustness. For instance, control of circuitry in the prior art designs appears founded on traditional communication systems. That is, carriers for modulating input signals are separated from the system control of circuitry that, in turn, impresses the data or information of the input signals onto the carrier. Unfortunately, since the frequencies of the information or data of the input signal must be adjusted to match the carrier frequency in systems having signals with substantially no sidebands, additional circuit components, including hardware, software and/or combinations thereof, must be found in the system. This adds complexity. Also, clocking signals to coordinate circuitry that controls the impressing of information of an input signal onto a carrier in a transmitter, and modulating same, needs to be conveyed or transmitted to a receiver for demodulating same. To the extent bandwidth availability is increased in systems contemplating signals with essentially no sidebands, some of the gains achieved by the system are given back by needing to transmit clocking signals.
Accordingly, the art of modulating/demodulating signals with no sidebands has need of improved control of systems involved with such signals. Furthermore, the improved control need contemplate hardware devices, such as transmitters, receivers, components, ASIC's etc., software such as various routines, algorithms, etc., programmed controllers and/or combinations thereof. Naturally, any improvements should further contemplate good engineering practices, such as relative inexpensiveness, low power consumption, ease of manufacturing, low complexity, etc.
The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described methods and apparatus for controlling communication systems that transmit and receive signals having essentially no sidebands.
In one aspect, information of input signals is impressed upon carriers. Circuitry for controlling such impression is, in turn, controlled by signals derived from the carrier itself. In this manner, frequency and/or phase of the input and the carrier can be maintained.
In another aspect, circuitry adjusts the frequency of an input signal into that of the carrier. The result then serves as an input of a gain adjustable module to adjust gain. Another input to the module is the carrier itself. The output of the module, then, is the signal having essentially no sidebands in a frequency domain. Representative modules include operational amplifiers, resistor networks and/or transistors. Representative gains include those on the order of about ten-to-one or five-to-one depending upon whether logic ones or zeros are being modulated.
In still another aspect, preferred carriers include sine waves while preferred control signals, derived there from, include square waves. In turn, square waves have more precise leading and trailing edges to activate or not various functional circuit components. In instances of modulating/demodulating signals having information per every half wave cycle of the carrier, control is implemented in a signal having a twice multiple integer of frequency of that of the carrier frequency. For modulating/demodulating signals having information per every full wave cycle of the carrier, the frequency of the control signal is a single multiple or the same frequency of that of the carrier. Naturally, circuitry components of the communication systems include discrete hardware, ASIC's, software or combinations thereof.
Transmitters, receivers and communication medium are also contemplated.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the present invention. In accordance with the present invention, methods and apparatus for controlling communication systems that transmit and receive signals having essentially no sidebands are hereinafter described.
With reference to
At element 30, via hardware (discrete and/or integrated components), and/or software/firmware and/or combinations thereof, a control signal 32 is derived from the carrier 16. In turn, the control signal 32 controls the circuitry 14 (alternatively: circuitry 11) of the transmitter. In this manner, separate clocking signals and attendant circuitry are unnecessary. They also need not be transmitted with the output signal to an attendant receiver for use in demodulation. This avoids complexity and saves system capacity. Also, a known frequency and phase relationship between the carrier 16 and the control of the circuitry 14 is readily obtained. This, as will become apparent below, enables greatly simplified circuitry. Further, it tends to ease manufacturing constraints and minimizes costs.
In various preferred embodiments, the derived control signal is a clocking signal. In one instance, it represents a square wave having precise leading and trailing edges as is typical for a clock. In another, it represents a sine wave or other signal useful in controlling circuitry. In either, the control signal typically includes a frequency that is an integer multiple of the frequency fc of the carrier. In this regard, representative integer multiples include 1, 2, 3, etc. As described subsequently, the integer multiple contemplates how regularly information from the input signal is impressed on the carrier. Namely, if information is impressed per every half wave cycle of a sine wave carrier, a twice multiple integer of frequency of the carrier is used to control circuitry. In other words, the frequency of the control signal is double the frequency of the carrier. On the other hand, if impression of information occurs per every full wave cycle of the sine wave, a single multiple integer of frequency of the carrier is used. Stated differently, the control signal has the same frequency of the carrier. Also, phase of the control signal is preferred the same as that of the carrier upon derivation. Various delays in the control circuitry, however, will undoubtedly alter this.
Regardless of control signal type, frequency, or phase, a data signal 34 is ultimately obtained. Preferably, it is the result of adjusting the frequency of the information contained in the input signal 12 into that of the frequency fc of the carrier. It is also preferred that the signal strength or amplitude of the data signal is made binary. Sequentially, the data signal 34 and carrier 16 are supplied to a gain adjustable module 40 to ultimately create the output signal 18. In one instance, the module is an operational amplifier with an attendant resistor network that the data signal gates to adjust gain between about five-to-one and about ten-to-one. In such instance, the former gain is then used to impress a first binary state of information, such as a zero, of information of the data signal onto the carrier, whereas the latter is to impress a second binary state of information, such as a one. Of course, the impressed information is caused to occur per every full or half wave cycle of the carrier sine wave at times when the sine wave 16 has no energy such as upon crossing the time, t, axis.
With more specificity,
In
In the instance of every full wave cycle of the sine wave carrier being impressed with information of an input signal embodied in a frequency matched data signal,
In
With reference to
With reference to
While pure sine waves of a carrier are theoretically possible, for most practical applications they are seldom attainable or maintainable. Therefore, in practical applications, purity is relative and is measured against current standards. For applications of this invention, attainable purity is more than adequate to advance the state of the art by several orders of magnitude while at the same time solving the universal problem of limited communication bandwidth.
Thus, the carrier can be typically embodied as a high quality sine wave oscillator 402 of stable frequency, generally but not necessarily, implemented around a commercially available crystal, which is constructed to oscillate precisely at a given frequency. As shown, the frequency is 20 MHz but, in practice, can vary from as little as 30 Hz to 3 GHz, or more. In sequence, the output sine wave of the oscillator conveys by line 17A to element 30 for deriving the control signal 32. It also conveys simultaneously, by line 17B, to the gain adjustable module 40, especially a linear amplifier 33 that will boost its power to a required level for a particular transmitting application.
Upstream of the gain adjustable module 40 is the data signal 34 that contains the information of the input signal 12, but is adjusted into an integer multiple of the frequency of the carrier 16. To accomplish this adjustment, the input signal 12 is supplied to an amplifier 404 having gain set according to a given application. In turn, the input signal (now V IN) is digitized in an analog-to-digital (A/D) converter 410. In this manner, the input signal can be scaled, without appreciable signal distortion, into a voltage range and waveform complimentary of the control circuitry. Naturally, the sampling rate of the A/D converter is at least twice that of the highest frequency component of the input signal according to the well known Shannon's Sampling Theorem. For example, if the input signal is audio on the order of about 2-20 kHz, the digital quantizing or sampling occurs at a rate greater than or equal to 40 kHz (e.g., 2×20 kHz). From the A/D converter, the output is preferably a series of 12-bit words ranging as a binary one or zero between 0 and +2.5 volts. Of course, TTL voltages range 0 to +5 volts; CMOS ranges higher and these and other voltage values and bit word sizes are equally embraced herein. As a practical matter, however, one actual A/D converter having utility with the invention is part number AD 7893, sold by manufacturer Analog Devices, and includes an 80 kHz sampling rate with series of 12-bit words as outputs.
Once digitized, the output S DATA of the A/D converter is clocked into a shift register (S/R) 412 at the sampling rate of the A/D. However, the output of the S/R, i.e., the data signal 34, is related to the carrier. That is, the frequency of the data signal is an integer multiple of the frequency of the carrier. For instance, if the carrier is 20 MHz and it is preferred to modulate an output signal 18-H or 18-F (see
To actually achieve the necessary clocking out of the data signal 34 from the S/R 412 at the appropriate frequency, the control signal 32 derived from the carrier 16 is supplied to a processor, of sorts, 420. In turn, the control signal is supplied as a clocking signal to both the S/R and A/D converter. Various pins of components, such as chip select (CS), S Clock, etc. are given in this regard. On the other hand, software implementation, ASIC implementation, or various combinations thereof with or without discrete components, will require appropriate routing of the control signal and such is within the scope of a skilled artisan's role.
To actually derive a control signal from the carrier, one implementation of the invention contemplates the carrier on line 17A supplied to a voltage comparator 55. The reference voltage source 43 for comparator 55 is set to the exact mean voltage of the carrier sine wave. The mean voltage of the sine wave is midway between the positive and negative peak voltage values and occurs at the 0, 180, and 360 degree phase points of the sine wave (see
Namely, at the gain adjustable module 40, the data signal 34 gates an electronic switch, i.e., transistor Q1, such that the resistor network R1, R2, R3 and R4 about the linear amplifier 33 includes or not the resistor value R1. That is, the gain equation is either R4/(R1+R2) or R4/R2. Then, during use in instances when R1 is not included, the transistor is conducting (such as when the data signal 34-H or 34-F is a voltage +2.5 volts, e.g., a binary one) and the gain of the adjustable module is about ten-to-one (e.g., R4/R2). Conversely, in instances when R1 is included in the resistor network, the transistor is not conducting (such as when the data signal 34-H or 34-F is a voltage 0, e.g., a binary zero) and the gain of the adjustable module is about five-to-one (e.g., R4/(R1+R2)). Of course, other gain adjustable strategies could be used to implement this feature.
Ultimately, an output signal 18 is transmitted having essentially no sidebands in the frequency domain and bandwidth availability for a given application is greatly enlarged. Again, simplicity is achieved because no separate clocking circuitry for control need be implemented with this design. In turn, no clocking need be transmitted to a receiver to help in demodulating the transmitted signal. This greatly increases practicality over the prior art.
With reference to
At 512, a phase locked loop (PLL) compares the incoming frequency (e.g., 20 MHz from the transmitted carrier) to a voltage controlled oscillator (VCO) (not shown) which is operating near the frequency of interest. In turn, a phase comparison between the frequency of the VCO and the incoming frequency is maintained constant by the inherent operation of PLL's (as is well known) and the incoming frequency is then determined or locked. The PLL also generates a logic level pulse train at the incoming frequency and such is used as the control or clocking signal 514 for the demodulation circuitry. Intuitively, just as the transmitter obtains its control by deriving a signal from the carrier, the control in the receiver is also derived from the carrier and is done via the only signal from the transmitter. That is, the modulated carrier 510 is used to extract the control or clocking signal. In this way, the 20 MHz sine wave carrier from the previous example is used to clock the receiver at either 20 MHz, 40 MHz, or other integer multiples of the carrier frequency. Control is thus simplified.
At 516, a binary counter enables time division encoding from the clocking signal for sequential control of logic functions in other components. As shown, four parallel outputs A, B, C, D provide input to control logic 518. Within 518, the control logic is preferably various “and/or” functions that produce control for still other components, such as the digital to analog (D/A) converter 520. Other embodiments of the receiver contemplate a processor of sorts instead of the control logic and/or the binary counter. Naturally, ASIC's are contemplated.
At 512, the clocking pulse 514 derived from the modulated carrier 510 is supplied 523 to a synchronous demodulator 522. In turn, the binary data of the modulated carrier is extracted 511. In a preferred embodiment, the synchronous demodulator senses the relative peak amplitude of the modulated carrier 510 and those above a certain voltage level, L, are deemed binary ones while those below the certain voltage level are binary zeroes. Of course, extracted data 511 can be on the order of every full wave or half wave cycle of the sine wave of the modulated carrier depending upon how transmitted.
Lastly, the D/A converter 520 undoes the digitizing of the A/D converter in the transmitter such that the input signal is fairly reproduced as the recovered signal 530. Naturally, sampling rates and voltage levels of the D/A converter of the receiver are known from use in the A/D converter of the transmitter.
In a larger perspective, a communications system of the invention may include transmitters, receivers, repeating stations, satellites, computers, transceivers, etc. To fairly sell transmitters, receivers, transceivers, etc. in embodiments, such as cell phones, radios, televisions, and computers, for individual use, it is contemplated that each transmitter can have its own tuned frequency, e.g., 10.000 MHz so that demodulation occurs exactly at the same frequency. In turn, the next sold item has a tuned frequency of 10.001 MHz with the next being 10.002 MHz and so on. While most conventional communications systems, due to limited bandwidth, are unable to achieve such functionality, it should be appreciated this departs from the conventional wisdom because bandwidth of signals having essentially no sidebands is so precise that unrelated components can have exceptionally close spectral parameters without causing interference. In turn, millions of precisely and uniquely tuned items can be purchased and sold. Alternatively, various frequency identifiers can be embedded in modulated signals of purchased items such that upon reception, the identifier is first learned and then demodulated, to get a recovered signal, at the frequency specified by the identifier. In still other embodiments, combinations of the two are possible. Naturally, skilled artisans can envision other feasible designs.
Also, the foregoing describes, in one instance, a carrier used to derive a control signal, especially a clock, for controlling circuitry in communication systems/devices. In other embodiments, however, the derivation can be reversed. That is, a control signal can be the signal from which a carrier is derived and still obtain the robustness of the invention. With reference to
In still other embodiments, the advantages of the invention, especially tying carrier and control signals to one another, for deriving one from the other, can be utilized in typical communication systems including, but not limited to, FM, AM, PSK, QAM, and the like.
Finally, the foregoing description is presented for purposes of illustration and description of the various aspects of the invention. The descriptions are not intended, however, to be exhaustive or to limit the invention to the precise form disclosed. Accordingly, the embodiments described above were chosen to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.
This application claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 60/742,164, filed Dec. 5, 2005, entitled “Zero Point Modulation Receiver Method.”
| Number | Date | Country | |
|---|---|---|---|
| 60742164 | Dec 2005 | US |
