Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/38—Transmitter circuitry for the transmission of television signals according to analogue transmission standards
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/10—Polarisation diversity; Directional diversity
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/41—Structure of client; Structure of client peripherals
  • H04N21/4104—Peripherals receiving signals from specially adapted client devices
  • H04N21/4113—PC
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
  • H04N21/4363—Adapting the video stream to a specific local network, e.g. a Bluetooth® network
  • H04N21/43637—Adapting the video stream to a specific local network, e.g. a Bluetooth® network involving a wireless protocol, e.g. Bluetooth, RF or wireless LAN [IEEE 802.11]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/64—Circuits for processing colour signals
  • H04N9/641—Multi-purpose receivers, e.g. for auxiliary information

Definitions

• the present invention relates to the high-quality wireless transfer of composite video information from a computer to a television set. More specifically, it applies to situations of severe multi-path propagation due to reflections, as is common in indoor propagation.
• BACKGROUND OF THE INVENTION Television sets are extremely common, and typically receive a television signal in one of several standard formats.
• the reception is either over a wire, as in cable systems, or over a wireless channel via an external antenna, be it a roof-top directional antenna aimed at the transmission antenna or a satellite dish.
• the signal quality is usually high and, most important, is not subject to the effects of indoor wireless propagation.
• Yet another option entails the use of a set-top antenna, but this typically results in poor reception quality, "ghosts" on the screen , etc.; such an arrangement is clearly inferior to the two previous ones, and is typically used only in the absence of a better alternative.
• the preferred approach is to enable the collaborative use of a standard computer and a standard television set, thereby making the computer resources available at the most desirable setting for any application (This approach does not prevent the use of the services of a service provider, with the connection done from the main home computer However, this would not be mandated and would only be done as necessary or desired by the user )
• the most challenging problem to this end is carrying the high-bandwidth signal containing the video and audio information from the computer to the television set and, possibly, in the other direction
• the simplest way of carrying the desired signal is through an appropriate cable connecting the computer with the television set
• this is impractical in many situations due to the aesthetic ramifications of installing a cable through a furnished home
• a wireless channel can be constructed between the two rooms
• a standard composite television signal is created at the PC, its carrier frequency is shifted to a permissible range and the result is transmitted
• the received signal's frequency is then shifted to one of the standard television channel frequencies and supplied to the television set
• This approach exemplified by the V900SX product of Recoton of Florida, USA and WaveCom by RF-Link Systems of Taipei Taiwan, is extremely limited in range and is highly susceptible to any imperfections in the signal-propagation environment
• the range limitations stem, in part, from regulatory constraints that severely restrict the transmission power, but both they and the inconsistent signal quality stem from propagation phenomena such as reflections, multi-path interference, and polarization distortion due to the numerous obstacles in the signal path in a typical home
• Yet another approach is to modulate the signal onto the mains (power) lines within the home, thereby reaching the desired room, and to either use very short range wireless links between a mains outlet in each room and the respective equipment (computer or television set) or use wires for this purpose.
• This approach attempts to overcome the wiring problem, but its quality is unreliable and it is susceptible to interference by equipment connected to the mains line.
• an object of the present invention to provide a wireless link for carrying high bandwidth signals, such as video and audio signals, within a home without requiring line of sight.
• the link would be used between a computer (typically) located in one room and a television set (typically) located in a different room or vice versa.
• a system for providing the output of a computer to a television set via wireless channel within a building includes a transmission antenna unit; a transmission processor, a reception antenna unit and a reception processor.
• the transmission processor is connected between the computer and the transmission antenna unit and converts the computer output to a composite video signal, upconverts the composite video signal to a carrier frequency not within a range reserved for television transmissions and provides the upconverted signal to the transmission antenna for transmission within the building.
• the reception antenna unit has at least one set of two, differently polarized reception antennas and receives the transmitted signal.
• the reception processor processes and combines the output of the two antennas of each set and adapts the processing in accordance with the quality of the output.
• the reception processor includes means for measuring the quality during non-image periods and for adapting the processing when necessary.
• the transmission antenna can be a multi-polarization antenna, a single polarization antenna or a steerable polarization antenna.
• the steerable polarization antenna includes a first antenna polarized in a first direction which directly transmits the upconverted signal, a controllable processor which provides at least one of amplification and phase shifting to the upconverted signal and a second antenna polarized in a second direction other than the first direction which transmits the output of the processor. The amount of the relative phase shift and relative amplification can be changed thereby to change the polarization direction of the combined signal transmitted by the pair of antennas.
• the steerable polarization antenna includes a multiplicity of first antennas lying in a first plane, a multiplicity of second antennas lying in a second plane and a selector. Each first antenna has a different polarization direction within the first plane. Each second antenna has a different polarization direction within the second plane. The selector selects one of the first antennas and one of the second antennas thereby to define a polarization direction. The upconverted signal is transmitted through the selected first and second antennas.
• the reception processor includes one adaptable antenna processing unit per set of reception antennas, a downconverter and a quality feedback unit.
• Each adaptable antenna processing unit has a control unit for controlling the relative phase shift and relative attenuation between the output of each reception antenna and one combiner for combining the processed output of the antenna set.
• the downconverter converts the output of at least one of the combiners to a television signal to be provided to the television set.
• the quality feedback unit measures the quality of the television signal and selects control values for the control unit accordingly.
• the quality feedback unit includes input units for receiving quality definitions from a user.
• FIG. 1 is a schematic illustration of a system for transmitting, within a building, video signals from a computer to a television set, constructed and operative in accordance with a preferred embodiment of the present invention
• Fig 2 is a schematic illustration of the transmission system useful in the system of Fig 1
• Fig 3 is a schematic illustration of a multipola ⁇ zation antenna useful in the system of Fig 1 ,
• Figs 4A and 4B are schematic illustrations of a reception system useful in the system of Fig 1 ,
• Fig 5 is a flow chart illustration of the operation of a quality control loop, useful in the system of Fig 1 ,
• Fig 6 is a graphical illustration showing one method for measuring the quality of a signal, useful in the method of Fig 5,
• Fig 7 is a block diagram illustration of a unit for measuring the rise time of the signal in Fig 6
• Fig 8 is a schematic illustration of a wireless input unit
• Fig 9 is a schematic illustration of an alternative transmission system useful in the system of Fig 1 .
• Figs 10A and 10B are schematic illustrations of an alternative reception system useful in the system of Fig 1
• Fig 1 1 is a schematic illustration of a steerable polarization antenna useful in the system of Fig 1
• Fig 1 1 is a schematic illustration of a steerable polarization antenna useful in the system of Fig 1
• Fig 12A is a schematic illustration of an alternative steerable polarization antenna
• Fig 12B is a schematic illustration of a selector useful in controlling the antenna of Fig 12A DETAILED DESCRIPTION OF THE PRESENT INVENTION
• the invention relates to the transmission and reception of an analog high-bandwidth composite video signal from a computer to a television set through a medium, such as a building, that typically does not offer line of sight between transmitter and receiver.
• Fig. 1 illustrates the system of the present invention within a building.
• the system includes a computer 10, such as a personal computer (PC), a television 12 between which are a blocking wall 14, a reflective wall 16 and a refractive wall 17.
• the system also includes a PC antenna signal processor 18 and a TV antenna signal processor 20, both for controlling the operations of their respective antennas 22 and 24.
• the system includes a wireless input unit 26 with which a user provides his input to the computer 10.
• Fig. 1 shows three copies, labeled 32, 34 and 36, all of which differ in the polarization, intensity, phase and angle at which they arrive to the reception antenna 24.
• a signal transmitted indoors in one or more directions undergoes an unpredictable sequence of reflections, refractions, scattering and diffraction as it goes through or is redirected by various obstacles and materials.
• wall 14 causes diffraction
• wall 16 minimally causes reflection
• wall 17 causes refraction.
• the signal arriving at the receiver antenna comprises a set of signals, some of which may have gone through different paths, and thus arrive after different delays, some of whose phase is altered due to reflections or other phenomena, and all of whom have different amplitudes.
• a signal that was originally transmitted with vertical linear polarization may go through a material that attenuates signals differently depending on their polarization.
• the result is a signal with a linear polarization different than that of the original signal. If different components of the transmitted signal undergo different phase changes, the result is generally a signal with elliptical polarization, a special case of which is circular polahzation. A combination of the two phenomena can result in a linearly-polarized component and an elliptically-polarized one.
• the various effects on the signal are a function of the type of walls in the building, their placement within the building and, more importantly, the relative placement of the computer 10 and television 12. Some relative locations within the building cause greater disturbance to the signals than others.
• antennas are generally built to have a single polarization, if the changes in polarization of the transmitted signal are such that the pola zation is completely changed, it is possible that an antenna placed in the wrong position might not receive any signal.
• the present invention attempts to remain operative no matter where the transmission and reception antennas are placed. As discussed hereinbelow, the present invention, however, utilizes a combination of transmission and reception antennas that, together, attempt to ensure that some signal is successfully received despite the possibly poor and/or unpredictable transmission conditions of the building.
• FIG. 2 details the elements of the transmission system
• Fig. 3 illustrates an exemplary transmission antenna 22
• Figs. 4A and 4B detail the elements of the reception system.
• the computer 10 produces an output signal which includes the audio and video signals that normally go to the speakers and computer monitor, respectively.
• PC antenna signal processor 18 prepares the output signal for transmission through the antenna 22. It includes a TV output generator 40, an upconverter 42 and a carrier frequency setter 44.
• the TV output generator 40 produces a TV output signal from the output of the computer 10.
• Upconverter 42 shifts the carrier frequency to the frequency defined by setter 44, where the carrier frequency is determined by signal quality and regulatory considerations. For the United States, the unlicensed bands are around 900MHz, 2.4GHz, 5GHz and 24GHz.
• the TV output generator 40 includes an RGB to TV unit 46 and a TV modulator 48.
• the computer video signals for the different colors are fed into the RGB to TV unit 46 which combines them to form a composite video signal, for example in a standard format such as NTSC or PAL.
• the composite video signal and the audio signal are fed into the TV modulator 48, which combines them to form a composite television signal.
• the modulator 48 also provides synchronization pulses known as frame sync, and line sync. The synchronization signals are provided to the frequency setter 44.
• Exemplary TV output generators 40 are the PC2TV chip from ATI of
• TV output generator 40 is a part of the computer itself.
• the composite signal is fed to upconverter 42 whose main components are a voltage controlled oscillator (VCO) 50, a mixer 52 and bandpass filters 54 and 56.
• VCO voltage controlled oscillator
• Upconverters are well known in the art and, therefore, upconverter 42 will be described only briefly.
• the frequency of oscillation of the VCO 50 determines the amount by which the signal frequency will be shifted.
• the mixer 52 performs the shift, and filter 54 filters the composite signal prior to its shifting in order to reduce the undesirable spectral sidelobes of the signal.
• the mixed signal is then further filtered by filter 56
• the filtered output of the mixer is fed to an amplifier 58, whose output is connected to antenna 22
• the frequency setter 44 sets the current carrier frequency of the transmitted signal Similar to cordless telephones, the number of frequency ranges is limited and a new frequency range is manually or automatically chosen only if there is significant interference on the previous frequency range from other wireless devices in the building
• the frequency setter 44 includes an encoder 60 and a frequency controller 62
• the encoder 60 defines the allowable frequency ranges and frequency controller 62 activates the VCO 50 in accordance with the current setting of encoder 60
• frequency controller 62 if the frequency range must be changed, frequency controller 62 typically changes it during "dead" periods of the TV signal, such as the "blanking periods” which occur during the return time of the beam at the end of a frame or a during horizontal scan line
• frequency controller 62 receives the sync outputs of the TV modulator 48
• transmission antenna 22 can be any suitable type of antenna
• the antenna 22 is a single polarization antenna
• antenna 22 can be a "multi-polarization" antenna having multiple, polarization directions
• the transmitted signal has one polarization direction
• the signal received at the reception antenna 24 is a collection of signals which have multiple polarization directions and which are phase shifted one from the other
• the TV antenna signal processor 20 can
• the resultant signal may not have a high signal to noise ratio.
• a multi-polarization antenna For a multi-polarization antenna, multiple signals are transmitted, each with different polahzation directions.
• the reception antenna unit 24 will still receive a collection of multi-polarized signals; however, at least one of the signals should provide a relatively high signal to noise ratio.
• the multi-polarization antenna "spreads the bets" as to which polarization is most effective for the various relative locations of computer 10 and television 12. With the multiple transmission signals and multiple polarization directions, the computer 10 and television 12 can be placed at whatever locations the user decides is right for him or her and the locations can change. For each location, one of the multiple signals most probably will provide a successful transmission.
• the multi-polarization antenna can be produced in any suitable way.
• the multi-polarization antenna can be any antenna with poor cross-polarization.
• such as antenna can be formed of two or three orthogonal linearly-polarized antennas.
• one antenna with linear, horizontal polarization and one antenna with linear, vertical polarization can be produced in any suitable way.
• Fig. 3 illustrates a further embodiment of a multi-polarization antenna. It comprises a conical monopole 70 whose tip 72 is connected to a ground plane 74.
• the spreading angle ⁇ should be larger than 120°.
• the ground plane 74 should be small relative to the wavelength of the transmitted signals.
• the antenna of Fig. 3 produces polarization in two orthogonal angular directions, known as ⁇ and ⁇ .
• FIG. 4A and 4B together form a block diagram of a reception system, according to an embodiment of the invention, which is useful with the transmission system of Fig. 2.
• the reception antenna unit 24 typically comprises multiple antennas which are paired such that each pair includes at least one antenna 80 having a first polarization and another antenna 82 having a second, different polarization.
• the two types of antennas 80 and 82 provide polarization diversity and the multiplicity of sets of antennas provide spatial diversity and directional adaptivity.
• the reception system also includes a antenna signal processor 84 and phase controller 86 per set of antennas, a combiner 88, a downconverter 90 and a quality control unit 92.
• the antenna signal processors 84, phase controller 86 and combiner 88 are controlled by the quality control unit 92 to adaptively tune the received signal.
• Downconverter 90 converts the received signal to one which television set 12 can process and quality control unit 92 determines the quality of the received signal, thereby to change the operation of units 84, 86 and 88.
• Reception antenna signal processors 84 can be any suitable unit which adjusts the relative phase shift and/or relative attenuation of the antennas connected thereto and which combines the results.
• antenna signal processors 84 each include an amplifier 94 and an attenuator 96 per antenna, a phase shifter 98 receiving the output of one of the attenuators 96 and a combiner 100 receiving the output of phase shifter 98 and the other attenuator 96.
• the attenuators 96 and phase shifter 98 receive an antenna control (ANTC) signal from the quality control unit 92.
• ANTC antenna control
• the reception antenna signal processors 84 assume that the signal which arrives at the reception antenna unit 24 is a single signal with unknown polarization.
• the received signal might be a linearly-polarized signal whose vertical and horizontal components are Kv * sin( ⁇ ) * cos( ⁇ t + ⁇ ) and Kh * cos( ⁇ ) * cos( ⁇ t + ⁇ ), where ⁇ is the angle of polarization. If two antennas, one with vertical polarization and the other with horizontal polarization, are used to receive the signal, their outputs would equal (to within the same multiplicative constant) the expressions just listed.
• the undesired signals can be viewed as interference or noise affecting the desired signal.
• the reception antenna signal processors 84 adjust the output of the antennas in order to reduce the affect of the undesired signals.
• Each signal has a horizontal component and a vertical component defined by the equations hereinabove; however, the polahzation angles, amplitudes and phases are different for the two signals.
• the desired signal has a polarization angle ⁇ such that the signs of the cosine and sine are equal
• the undesired signal has a polarization angle ⁇ ' such that the signs of the cosine and the sine are different from each other. If the outputs of the two antennas are added, the undesired signal will be partially canceled, since it requires subtraction for best reception.
• the two (horizontal and vertical) components of the undesired signal can made to effectively cancel one another without affecting the desired signal.
• the choice whether to add or subtract the outputs of the two antennas can be used to amplify the desired signal; moreover, in conjunction with variable attenuation, it is also possible to essentially eliminate the most problematic linearly-polarized interfering signal if its polarization angle is within a given 180° range.
• phase shifters 98 adjust the relative phases to offset the difference. Amplitude attenuation can again be employed to reduce the effect of undesired arriving signals.
• the reception antenna signal processors 84 produce a tunable reception antenna, under control of quality control unit 92, which can effectively achieve polarization steering in the case of elliptically-polarized signals.
• Antenna signal processors 84 enable the reception system of Figs. 4A and 4B to attempt to match the polahzation of the desired signal. For a linearly-polarized arriving signal, the effect is slightly different: the decision whether to add or subtract the two signals provides a two-state polarization tuning, and the variable attenuation can be used to reduce the adverse effect of undesired signals whose polarization is in a different 180° range than that of the desired signal.
• the output signals of the different reception antenna signal processors 84 are each provided to their corresponding phase controller 86, also under control of the quality control unit 92.
• Phase controllers 86 shift the phase of one or both of the output signals of the reception antenna signals processors 84 to have matching phases.
• the output signals of the phase controllers 86 are then fed to the combiner 88 which, under control of the quality control unit 92, merges the signals to achieve the effect of a directional antenna.
• the phase controllers 86 and the subsequent combiner 88 are replaced by a selector that selects one of the signals. Since there are two or more sets of antennas, the antenna set in the currently best location can be selected. This is known as space diversity.
• the signal at the output of the combiner 88 or, in the alternative embodiment, at the output of the selector, is fed to downconverter 90 which shifts the carrier frequency of the signal to a channel that can be received by the television set 12.
• the downconverter contains a mixer 102, a tunable oscillator, such as a voltage-controlled oscillator 104, for determining the frequency shift, and bandpass filters 106 to prevent any undesirable spectral pollution.
• the "PCTV" signal output of the downconverter 90 is then fed into a signal splitter 108 that allows most of the signal to continue into an antenna combiner 110 which feeds the signal along with a signal from a conventional TV antenna or cable system 112 to the television receiver 12.
• the carrier frequency of the PCTV signal coming out of the downconverter 90 differs from that of the signals coming from the conventional antenna 112 so that the PCTV signal does not interfere with the conventional TV signals and, if desired, both the PCTV signal and the conventional TV signals can be viewed simultaneously on the screen of the television set 12. This is similar to the "picture in a picture" feature of some recent television sets.
• quality control unit 92 measures the quality of the signal during the blanking periods of the signal (i.e. duhng the vertical and horizontal return of the electron beam of the television set), which transmit no information. Quality control unit 92 can change the control variables during the blanking periods or at any other suitable time du ng the transmission.
• the present invention utilizes the blanking period of the signal currently being provided to the television set 12.
• Quality control unit 92 comprises a frequency shifter 120 (under control of a voltage controlled oscillator 121), a low pass filter 122, a sync separator 124, a microcontroller 126 and a frequency encoder 128.
• the frequency shifter 120 removes the carrier frequency of the PCTV signal so as to recover the baseband composite video signal.
• the composite video signal is filtered by low pass filter 122 and is then fed into sync separator
• the microcontroller 126 assesses the quality of the blank periods of the PCTV signal via methods described hereinbelow with respect to Fig. 5. If the quality is less than desired, the microcontroller 126 changes the polarization direction as defined by the attenuation values, phase shift values and combination/selection of the antenna output signals. If the quality is very poor, the transmission frequency can also be changed. The microcontroller 126 typically attempts a variety of settings, assesses their quality and selects the current best setting for the next frame. As long as the quality stays above a desired level, the microcontroller 126 will make no further changes.
• the microcontroller 126 specifies the attenuation levels of the different attenuators 96, the phase shifts of the phase controllers 98 and 86, and the selection to be made by the selector (in the relevant embodiment).
• the microcontroller 126 also selects the frequency shift of the downconverter 90, based on a frequency sequence generated by the encoder 128, to shift the carrier frequency of the transmitted signal to one which the television set 12 can receive.
• microcontroller 126 indicates the new frequency range through an appropriate command (not shown) to the voltage controlled oscillators 50 (Fig. 2) and 121
• the microcontroller 126 communicates commands to the transmission system of Fig. 2 via a wireless channel.
• reception system could include an extra antenna-tuning mechanism for the sole purpose of continually testing the received signal.
• special signals can be transmitted duhng the blanking periods in order to facilitate the assessment of signal quality.
• Fig. 5 illustrates a method, performed by the microcontroller 126, for automatically selecting an acceptable picture quality.
• the quality of the picture is assessed by microcontroller 126. This can be achieved in any of a number of ways, all of which are incorporated into the present invention.
• the quality is measured by the intensity of the sync signals which, unlike the television signals, carry no information thereon and therefore, should have a single intensity level. When the intensity is below a predetermined threshold, the transmission quality is poor. Intensity can be measured by a rectification and averaging circuit, whose output voltage reflects the intensity of the received signal or it can be measured digitally, by the microcontroller 126.
• the quality is defined by the sharpness of the sync pulses, as shown in Fig. 6 to which reference is now made.
• Fig. 6 shows two exemplary sync pulses 132 and 134, where the first pulse 132 propagated along only one path and the second pulse 134 propagated along many paths.
• the second pulse 134 in effect, is a collection of many pulses which arrived at slightly different times.
• the first pulse 132 is much sharper than the second pulse 134 and this can be measured by their rise times T1 and T2.
• the rise time T1 of the first pulse 132 is much smaller than that of the second pulse 134.
• the sharpness of the signal is measured by its rise time. If the rise time is below a predetermined value, the signal quality is high.
• Measurement unit 135 typically receives the output of the sync separator 124 and provides input to the microcontroller 126. It includes an automatic gain control (AGC) amplifier 180, a high pass filter 182, a rectifier and averager 184 and an analog to digital (A/D) converter 186.
• AGC automatic gain control
• the output of the automatic gain control amplifier 180 is the sync signal in its original shape but with a predetermined intensity.
• the output of the AGC amplifier 180 is then fed into high-pass filter 182, producing a signal whose intensity is a monotonically decreasing function of the rise and fall times of the sync signals.
• the outputs of the filter 182 and of the AGC amplifier 180 are fed into rectification and averaging circuit 184, which produces a voltage level that increases as the sharpness of the sync signal increases. This signal is fed back into the gain-control input of the AGC amplifier in order to control its gain such that the signal level at the output remains generally constant. Details of the method for obtaining a signal at an essentially constant intensity are omitted, since they well known in the art.
• ADC analog-to-digital converter
• the signal quality can also be measured by a combination of intensity and sharpness.
• the signal quality is good (step 136)
• no change will be made duhng this blanking period (step 138). Otherwise, the microcontroller
• acceptable can have any suitable meaning for this purpose. It can be measured by being above some predetermined threshold, or it can be the most optimal of the entire set of values or it can mean a change of a certain amount from the previous value.
• step 142 the phase shift of the currently active antenna(s) is changed by microcontroller 126 in small increments, measuring the quality change resulting from each new phase shift. If the quality is high enough for any of the phase shift values (as checked in step 143), the settings (step 148) are changed by microcontroller 126 to the new phase shift and attenuation values.
• step 144 a similar operation is performed (step 144) on the attenuation values.
• step 146 the results are reviewed. If they are above a predetermined quality threshold, then the settings are changed (step 148) to the new phase shift and attenuation values. Otherwise, a new frequency setting is selected (step 150) and the process repeats at step 142. If the quality does not improve once all frequency settings are reviewed, the original settings are maintained.
• the picture quality can be measured in another way, as indicated in Fig. 8 to which reference is now briefly made.
• the input unit 26 shown in Fig. 1 has a number of buttons 190 thereon with which the user indicates the quality of the signal he or she is seeing.
• buttons might indicate lack of "snow", sharpness, etc.
• the input unit 26 has two wireless transmitters 192 and 194, where the former transmits input to the computer 10 and the latter transmits the quality information to the television antenna signal processor 20.
• the television antenna signal processor 20 does not need to separate out the sync signals.
• the input unit 26 can have a single wireless transmitter that transmits to the computer 10 and the latter transmits the user's quality information, in the blanking periods, to the television antenna signal processor 20. Still further, the input unit 26 can transmit to the computer 10 and the PC antenna signal processor 18 could include the microcontroller 126 shown in Fig. 4A. In this embodiment, the PC antenna signal processor 18 transmits the control signals to the television antenna signal processor 20 and the latter does not include the feedback elements of units 120, 121 , 124 and 126 shown in Fig. 4A.
• each combination of locations of computer 10 and television set 12 typically has one direction and polarization which provides the best path from computer 10 to television set 12.
• the reception processing of the present invention attempts to optimize the effective polarization of the reception antennas but that might not satisfy the user. For example, if the building causes a vertical polarized signal to go through an obstacle that does not let vertical through, there will not be any signal to receive.
• Figs. 9, 10A and 10B illustrate an alternative embodiment of the transmission and reception systems, respectively, utilizing a transmission antenna 150 which has steerable polarization and to Figs. 11 , 12A and 12B which illustrate two embodiments of such a steerable polarization antenna.
• the transmission system is similar to that of the previous embodiment.
• the PC antenna signal processor 152 of this embodiment is essentially the same as PC antenna signal processor 18.
• steerable polahzation antenna 150 is an antenna whose polarization direction can be adaptively changed
• the television antenna signal processor of Figs. 10A and 10B, labeled 153 is simplified compared to that of Figs. 4A and 4B.
• the television antenna signal processor 153 includes the quality control unit 92 but the control signal is also transmitted, via a wireless channel as discussed hereinabove, to the steerable polarization antenna 150.
• Fig. 11 shows one embodiment of the steerable polarization antenna 150.
• Its input signal is an original signal specified (as a function of time) by the function s(t) and it comprises two antennas 154 and 156 where antenna 154 has horizontal polarization and antenna 156 has vertical polarization, two amplifiers
• phase shifter 160 158 and 159, one per antenna, and an optional phase shifter 160.
• the polarization of a signal transmitted by the two antennas 154 and 156 is the vector sum of the output of the two antennas.
• input signal s(t) is fed into vertical antenna 156 after being amplified, in amplifier 159, by a constant Kv, and similarly fed into horizontal antenna 154 after being amplified, in amplifier 158, by Kh
• the resulting signal which is the vector sum of the two, has an intensity which is the square root of (Kv 2 +Kh 2 ) and is polarized at an angle defined by the arctangent of (Kv /Kh) relative to horizontal.
• Microcontroller 126 changes the polahzation of steerable polahzation antenna 150, typically in small steps, to select the polarization direction which provides the best transmission signal.
• Figs. 12A and 12B illustrate a different steerable polarization antenna, 5 labeled 150'.
• This antenna comprises a plurality of first antennas 170 in a first plane 171 , a matching plurality of second antennas 172 in a second plane 173 and a selector 174.
• the antennas 170 and 172 transmit in a different directions. Any combination of one first antenna 170 and one second antenna 172 provides an antenna with a different polahzation, where the polarization is the vector sum l o of the two polarizations.
• Selector 174 receives the input signal s(t) and provides it to the currently selected first and second antennas 170 and 172, respectively. Selector 174 chooses the two antennas in accordance with instructions from microcontroller 126. 15 For both types of steerable polahzation antennas 150 and 150', the adjustment sequence involves first setting the transmitted polahzation and transmitting the signal. The reception antennas are then adjusted, as described hereinabove with respect to Fig. 5, and the quality level is recorded. The process is repeated for each possible polarization, where, for the steerable polahzation 20 antenna 150 of Fig. 11 , the values of the phase shift and amplifications are stepped. The microcontroller 126 selects the polahzation level to the one which produced the best results and provides the appropriate signals to the steerable polahzation antenna 150 or 150' and to the antenna signal processor 84.
• the combinations of transmission and reception 25 antennas shown herein are not the only combinations possible.
• the transmission antenna can be a steerable polarization antenna and the reception antenna can be a multiple set antenna such as is shown in Fig. 2.
• the receiver can have a multi-polarization antenna or, if the transmission antenna is a steerable polarization antenna, the receiver can have a single 30 antenna. Any and all of the combinations shown hereinabove are incorporated in the present invention. The many features and advantages of the present invention are apparent from the written description, and thus, it is intended by the appended claims to cover all such features and advantages of the invention.

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Computer Networks & Wireless Communication (AREA)
• Radio Transmission System (AREA)
• Details Of Television Systems (AREA)
• Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
• Radio Relay Systems (AREA)

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• 1997
  • 1997-08-26 IL IL12163697A patent/IL121636A/xx not_active IP Right Cessation
• 1998
  • 1998-08-23 WO PCT/IL1998/000400 patent/WO1999010999A2/en not_active Application Discontinuation
  • 1998-08-23 BR BR9814443-0A patent/BR9814443A/pt not_active IP Right Cessation
  • 1998-08-23 CA CA002301578A patent/CA2301578A1/en not_active Abandoned
  • 1998-08-23 EP EP98940525A patent/EP1010272A4/de not_active Withdrawn
  • 1998-08-23 CN CNB988103745A patent/CN1164111C/zh not_active Expired - Lifetime
  • 1998-08-23 AU AU88828/98A patent/AU8882898A/en not_active Abandoned

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