Patent Publication Number: US-8125386-B2

Title: Steerable antenna and receiver interface for terrestrial broadcast

Description:
RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 11/839,202, filed Aug. 15, 2007 now U.S. Pat. No. 7,633,441 which is a divisional of U.S. patent application Ser. No. 11/346,643, filed Feb. 3, 2006 which issued as U.S. Pat. No. 7,425,920 and which is a continuation of U.S. patent application Ser. No. 10/020,703 filed on Nov. 30, 2001 which issued as U.S. Pat. No. 7,006,040 and which claims the benefit of U.S. Provisional Application Ser. No. 60/257,219 filed Dec. 21, 2000, each of the preceding applications is hereby expressly incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to methods and apparatus for implementing and using antennas, and, more particularly, to methods and apparatus for implementing and controlling steerable antennas, e.g., for use in receiver devices such as television sets. 
     BACKGROUND OF THE INVENTION 
     Digital Vestigial Sideband (VSB) is the modulation format selected as the US terrestrial broadcast standard. As with all digital modulation formats, a critical aspect of receiver design is the handling of multipath, especially severe multipath interference combined with a marginal signal-to-noise ratio. The severity of the problem is maximized with indoor antennas used in urban environments. This is because, in urban environments, there are numerous buildings which tend to interfere with reception while also reflecting the transmitted signal leading to significant multipath interference. At present, multipath is handled by an equalizer in the demodulator portion of a receiver. 
     Despite recent improvements in equalizer design, signal reception under strong multipath conditions remains a technical problem confronting digital terrestrial broadcast. 
     In the context of satellite and analog television systems, various attempts have been made to improve reception by controlling one or more antenna characteristics. Unfortunately, such attempts have, for the most part, focused on satellite antennas or have generally ignored issues relating to multipath interference. Furthermore, such system generally ignore and/or issues relating to the receiver/antenna interface. 
     For example, U.S. Pat. No. 6,111,542 describes a user terminal including a rotating electronically steerable antenna system which combines coarse mechanical beam steering with fine electronic beam steering to provide full hemispherical coverage and enable hand-offs in a satellite communication system. Unfortunately, this reference fails to address issues relating to multi-path interference or to provide a simple control mechanism by which a digital receiver can automatically control multiple antenna characteristics. 
     The abstract of Published Japanese Patent Application 61296573 describes an adaptive antenna system which generates a steering signal based on an MSN algorithm implemented by a processor coupled to the antenna. The generated steering signal is used to adjust a directivity characteristic of an antenna element so that the major beam will be directed to the desired wave incoming direction even if the incoming direction of the desired wave is changed. As with the preceding reference, this reference fails to address issues relating to multi-path interference or to provide a simple control mechanism by which a digital receiver can automatically control multiple antenna characteristics. 
     U.S. Pat. No. 5,771,015 describes a system which relies on viewer input to select from a plurality of possible antenna settings. The described system includes a controllable antenna intended for indoor use as part of a television system. The system includes various electro-mechanical assemblies for controlling physical attributes of the antenna such as the orientation of antenna elements about a vertical axis, the length of antenna elements, the angular orientation of a loop antenna about a vertical axis, etc. Electrical attributes of the antenna such as the gain of variable gain elements can also be controlled. A viewer of the system selects what is perceived to be the optimum settings for a particular channel and the settings are stored for future use when the channel is selected. The described system has the disadvantage of relying on viewer input to determine the appropriate antenna settings. The need for such input results in a relatively complicated and non-user friendly control system. Furthermore, the specific problem of multipath interference is not addressed by the reference. 
     Given the challenges presented by multipath interference, there remains a need for antenna designs which are intended to eliminate and/or reduce the effect of multipath on received signals. In addition, while various systems have addressed controlling various physical and electrical characteristics of an antenna, there remains room for improvement in the way antennas are controlled. In particular, there is a need for improved antenna control methods which eliminate the need for viewer input. There is also a need for improvements in the number of antenna characteristics that can be controlled, and for improvements in the signaling techniques used to control antenna settings. Furthermore, in order to provide increased reliability and reduce manufacturing costs, it is desirable that the use of movable mechanical parts be reduced and/or eliminated at least in some embodiments. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to methods and apparatus for implementing and controlling steerable antennas. Various embodiments of the invention are directed to antennas suitable for indoor use. Such antennas may be, e.g., incorporated into television receivers, e.g., to facilitate the reception of DTV signals. To reduce the effects of multipath interference, in various embodiments antenna patterns with one or more nulls are used. Aligning a null with a source of signal interference, e.g., a strong multi-path signal, the signal to noise ratio is improved resulting in an increased ability to demodulate and decode a received signal. 
     While the antenna control techniques of the present invention can be used with mechanically steerable antennas, to reduce the number of mechanical parts and to facilitate rapid redirection of the antenna pattern through the use of digital control signals, many embodiments of the invention are directed to antennas with electrically steerable reception patterns. 
     In accordance with various embodiments of the invention, the antenna pattern, e.g., it orientation, is directed by control circuits within a receiving device such as, for example, a demodulator and associated circuits, or by a similar device located in or coupled to the antenna. In accordance with the invention, the circuitry used to control the steerable antenna communicates with the antenna via digital signals transmitted over a digital bus. 
     The digital bus may be separate from the line(s), e.g., coaxial cable, used to couple the antenna elements to the receiver circuitry. Alternatively, the coaxial cable may be used as the bus in addition to the communications path by which signals received by the antenna are provided to the receiver circuitry. 
     From the users&#39; standpoint, the steering can be automatic. Control can be effected, in accordance with the invention, by a one or two-way digital link. Use of a two-way link between the steerable antenna and antenna control circuitry provides for more advanced control functions, as compared to a one-way link. It also allows for the exchange of stored antenna characteristic information from the steerable antenna to the circuitry used to control the antenna. 
     In accordance with one feature of the invention, the antenna is implemented with an antenna pattern having one or more receiving directions characterized by relatively high reception “gain” and one or more other directions characterized by low gain (“nulls”). Low gain, e.g., null, antenna pattern regions may have, for example, a gain which is 6 dB or more down from the gain in a high gain antenna pattern region. The angular coverage of the “high gain” region (i.e., the number of degrees of arc over which the gain is substantially constant) is a function of antenna complexity and performance. However, antenna complexity does not affect the general concept of the present invention, as long as it is possible to steer the high gain condition to the various directions in which reception is to be supported, e.g., around a full circle of coverage in various embodiments. 
     The control signal used to control the antenna is derived, in various embodiments, by analysis of various aspects of the received signal such as, e.g., signal-to-noise ratio, multipath, other interference, etc. Measurements of such aspects of a signal are often inherent in digital demodulation making them well suited for use in antenna control while adding relatively little additional cost or complexity to a digital receiver. 
     The digital control signal can easily provide for many more antenna states than are necessary or practical for a low-cost antenna. While the number of antenna pattern positions which are supported may be important to performance in some embodiments, the present invention does not require any specific number of antenna pattern positions but rather only that multiple antenna pattern positions be supported. 
     In some embodiments, the optimum antenna pattern position is determined by emphasis on achieving the highest antenna gain. Such an antenna position control approach is useful where, e.g., addressing low signal power is an important, or the only, reception issue. In other embodiments where multipath or other signal interference is an important factor, the position of the antenna pattern is steered to position a reception “null” facing the direction of the multipath signal or other interference. More advanced control techniques, which may be used in accordance with the invention, involve consideration of a plurality of factors in determining the optimum antenna pattern position. 
     In various embodiments, in addition to a controllable antenna pattern position, a pre-amplifier associated with the antenna has its gain adjusted under the control of signals received via the control bus. Antenna pre-amplifier adjustments may depend, for example, on signal level and the presence or absence of other strong signals that might overload the amplifier. 
     In some embodiments, in addition to antenna position and gain adjustments, adjustments in antenna polarization are also supported. Antenna polarization is selected, e.g., in embodiments which use an antenna which provides, e.g., more than one horizontal and/or vertical polarization. 
     Various embodiments of the invention are intended for use in consumer devices such as television receivers. For such embodiments, for cost reasons, fairly simple antenna patterns, gain and polarization adjustments are described and used. However, the same concepts and features apply to more complicated and expensive antennas which can also be implemented in accordance with the invention. Likewise, the control bus of the present invention and control signals are intended to be simple and of relatively low speed, for reasons of cost and control of radiation from the digital signals on the bus. However, faster and more elaborate control signals are also possible and within the scope of the present invention. 
     Although the present application is directed towards digital television, terrestrial broadcast signals, and their demodulators, the general principles of a steerable antenna controlled by analysis of the received signal apply to other digital signals such as, analog TV, radio and other signals. Furthermore, the antenna control techniques of the present invention can be used in mobile as well as stationary devices. 
     Although various features of the present invention are described in the context of exemplary embodiments which use electrically steerable antenna patterns, the signaling and control methods of the present invention, including the antenna control interface, can be used in conjunction with mechanically steerable antennas, e.g., one mounted on a rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a building having a television set implemented in accordance with the present invention located therein. 
         FIG. 2  illustrates an exemplary antenna pattern which may be used in accordance with the present invention for implementing a steerable antenna. 
         FIG. 3  illustrates the television of the present invention shown in  FIG. 1  in greater detail. 
         FIG. 4  illustrates the exemplary antenna used in the exemplary embodiment shown in  FIG. 3 . 
         FIG. 5  illustrates the controller of the present invention shown in  FIG. 3 , in greater detail. 
         FIG. 6  illustrates an exemplary steerable antenna that may be used with the present invention. 
         FIG. 7  illustrates an exemplary multi-bit digital control signal which can be used to control an antenna in accordance with the present invention. 
         FIG. 8  illustrates a portable computer system using multiple antennas in accordance with a mobile embodiment of the present invention. 
         FIG. 9  illustrates an exemplary television set incorporating the novel antenna and receiver features of the present invention might appear as viewed from the front. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, the present invention is directed to methods and apparatus for implementing, using, and controlling steerable antennas. 
     While not limited to indoor applications, the methods and apparatus of the present invention are particularly well suited for implementing indoor receivers, such as television sets, which use indoor antennas. 
       FIG. 1  illustrates a television receiver  104  implemented in accordance with the present invention. The television  104  includes an antenna  302 , a receiver  310  and a display device  320  which are coupled together as shown in  FIG. 1 . The television  104  is an indoor device as indicated by its location inside a building  102 . The building  102 , may be e.g., a residence such as a home or apartment.  FIG. 9  illustrates how an exemplary television  104 , incorporating the features of the present invention, might appear when viewed from the front of the television. 
     As will be discussed in detail below, the antenna  302  receives and supplies broadcast signals to the receiver  310 . In addition the antenna  302  and receiver  310  interact so that the antenna pattern of the antenna  302  is steered under the control of the receiver  310  as a function of the signal to be received and/or signal interference which may be encountered. In addition to the direction of the antenna pattern other antenna characteristics may also be controlled by the receiver  310 . Receiver  310  demodulates and, optionally, decodes, signals received from the antenna  302 . The resulting signals are supplied to the display device  320 . In addition to generating the signals to be displayed, the receiver  310  is responsible for generating the antenna control signal or signals used to control the antenna  302 . 
       FIG. 7  illustrates an exemplary digital antenna control signal  700 . The signal  700  may be generated by the receiver  310  and supplied to the antenna  302  in accordance with the present invention. As illustrated the exemplary control signal  700  includes direction, gain, channel number and polarization control values  702 ,  704 ,  706 ,  708 , respectively. Eight bits  702  are used to control the direction of the antenna pattern. Two bits  704  are used to control the gain of an amplifier in the antenna  302 . Seven bits  706  are used to specify the number of the channel, e.g., television channel, to be received. Another two bits  708  are used to specify antenna polarity. Fewer or more bits than those shown in  FIG. 7  can be used to control various functions and, in cases where all control functions are not supported, some bits may be omitted. For example, in the case of antennas which do not support adjustable polarity the two bits  708  used to specify antenna polarity may be omitted from the control signal or, alternatively, disregarded by the antenna  302 . While eight bits  702  are shown as being used to support direction control, when fewer than 2 8  positions are supported, less than 8 bits may be used to specify direction. 
     As discussed above, in urban environments, multipath signals resulting from reflections off nearby buildings can make it particularly difficult to demodulate and decode a transmitted signal. One feature of the present invention is directed to an antenna with an electrically steerable pattern. For purposes of being able to reduce the effect of interference from a particular direction, it is desirable that the utilized relatable antenna pattern have relatively deep nulls located at one or more points. 
     An example of a suitable antenna pattern for use in accordance with the present invention is a cardioid  200 , such as the one shown in  FIG. 2 . As illustrated the cardioid antenna pattern includes a large main lobe  201  located to the front of the antenna pattern  200 , a small rear lobe  203  and deep nulls  202 . In the  FIG. 2  diagram, the larger the antenna pattern lobe, the stronger will be the reception in the area corresponding to the lobe. 
     In the case of strong multipath or other interference, steering of the antenna pattern  200  involves moving the pattern&#39;s nulls  202  to minimize multipath and/or other interference. In the case of strong interference, this can be preferable to steering the main lobe  201  to maximize signal strength. The pattern  200  of  FIG. 2  provides a broad main lobe  201  in addition to well-defined nulls  202  and/or the region of attenuation  204 . 
     The cardioid pattern of the antenna  302  rotates under control of the receiver  310 . Continuous rotation may be supported but is not required. Four discrete positions (e.g., north, south, east, west) may be sufficient for many applications. However, finer rotational control is likely to provide better results. 
     The exemplary pattern shown in  FIG. 2  uses a pattern with a large front-to-back ratio for an inner city multipath environment. While not being inconsistent with the invention, a steerable single dipole pattern is probably not as good as the suggested cardioid in the case of multipath conditions due to the lack of a large front to back ratio. Use of other patterns than the one shown in  FIG. 2  is possible and contemplated as being within the scope of the invention. 
     The exemplary television  104  of the present invention shown in  FIG. 1  is illustrated in greater detail in  FIG. 3 . In particular,  FIG. 3  shows exemplary contents of the receiver  310  and antenna  302  which are coupled to the display device  320 . The receiver  310  receives/sends information and control signals over a bus  311 . In addition, signals from the received by the antenna  302  are communicated to the receiver via co-axial cable  313 . DC power is supplied from the receiver to the antenna via a power supply line  315 . 
     The receiver  310  includes a controller circuit  312 , a tuner  314  and a demodulator  316 . The tuner performs various filtering and equalization operations on the received signals supplied by the antenna  302 . After processing of the received signal by the tuner, the received signal is subject to demodulation and/or decoding prior to being supplied to display device  320 . Demodulator  316  is responsible for performing the demodulation operation on the received signal and for generating various signal measurements which are used by the controller  312  in generating the antenna control signals. The signal measurements may include, e.g., signal amplitude, signal to noise level (S/N) and other measurements, e.g., various channel condition estimation measurements. While a demodulator is shown in  FIG. 3  as the device making the signal measurements from which antenna pattern position control signals are based, signal demodulation is not required in all embodiments and relatively simple circuitry may be used in place of a demodulator for making such signal measurements. For example a received signal could be processed by a rectifier and then subject to amplitude measurements with the resulting measurements then being used to control antenna pattern position. 
     In  FIG. 3  the control signal generated by the controller  312  is transmitted to the antenna  302  over a stand alone communications link, e.g., bus  311 , or by way of tuner  314 , over the same line, e.g., co-axial cable  313 , used to supply the received signal from the antenna  302  to the receiver  310 . 
     The antenna  302  is responsive to the control signal or signals received from the receiver  310 . The antenna  302  includes an antenna loop  304  which is coupled to an antenna control and parallel tuned coil and varactor diode circuit  306 . The tuned coil varactor diode circuit  306  is optional, and omitted in some embodiments, e.g., in a exemplary UHF TV antenna embodiment. The circuit  306  communicates with the controller  312 . 
     The antenna loop  304  may be small in size. However, even with an electrically small size the antenna loop can achieve adequate bandwidth for many receiver applications without being deliberately lossy. In the context of a television receiver embodiment, where 6 MHz is allocated per television channel, the “full-gain” bandwidth will normally correspond to at least one TV channel, e.g., 6 MHz. 
     As will be discussed further below with reference to  FIG. 4 , the antenna control and parallel tuned coil and varactor diode circuit  306  provides tuning if necessary or helpful to maximize the delivered signal level and/or S/N ratio. A single-tuned L-C circuit maybe adequate for use in the circuit  306 . The tuned L-C circuit may comprise, e.g., a coil and varactor diode combination at the antenna terminal where it feeds into the co-axial cable or twin-lead. 
     The dc voltage for controlling the varactor diode is generated in the antenna  302 . The receiver  310  provides channel number information as part of the control signal  700 , but it need not provide the actual dc voltage used to control the varactor diode since this voltage will be generated locally. This is so that the antenna  302  and the tuner  314 , which may be purchased separately, do not need matching voltage-versus-frequency characteristics. As will be discussed with regard to  FIG. 4 , the antenna  302  includes circuitry to translate the channel number to a suitable dc voltage of sufficient accuracy and resolution for antenna tuning. 
       FIG. 4  illustrates an exemplary antenna  302 . The antenna  302  includes the controllable antenna loop  304  and the antenna control and parallel-tuned coil and varactor diode circuit  306 . A connector  303  is used to connect the power supply line, control bus, and antenna output (co-axial cable) to the receiver. 
     Circuit  306  includes a decoder/control logic circuit  404 , channel number-to-tuning voltage ROM  414 , Digital to Analog Converter (DAC)  416 , parallel-tuned coil and varactor diode  418 , variable gain signal amplifier  420 , and antenna capabilities information  422 . 
     The decoder/control logic circuit  404  is responsible for receiving and parsing antenna control signals to generate individual signals used to control each of the adjustable antenna characteristics. Decoder/control logic circuit  404  includes decoder control  406 , direction decoder  408 , gain decoder  410 , and polarization control  412 . 
     The decoder control circuit  406  is responsible for initial parsing of received control signals. Assuming receipt of the exemplary control signal shown in  FIG. 7 , the decoder control circuit  406  will extract the data in each of the control fields  702 ,  704 ,  706 ,  708  and supply them to the corresponding decoder or control circuit. 
     For example, the 8 bits corresponding to direction control will be extracted from a control signal by decoder control circuit  406  and supplied to the direction decoder control circuit  408 . 
     The direction decoder circuit  408  interprets the 8 bit direction signal and generates antenna loop switch control signals to implement the direction instruction. The switch control signals are supplied to the controllable antenna loop  304  and are used to control switches included therein which determine antenna pattern direction. 
     An exemplary antenna structure  600 , e.g., controllable antenna loop, which uses PIN diodes  602 ,  604 ,  606 ,  608  as controllable switches, is shown in  FIG. 6 .  FIG. 6  is a conceptual drawing provided for purposes of explanation. In an actual implementation, the actual antenna configuration, number of gaps, etc. may look and be different as long as it allows for antenna pattern steering in accordance with the invention. As shown in  FIG. 6 , the antenna  600  comprises four elements,  610 ,  612 ,  614 , and  616 . PIN diodes  602 ,  604 ,  606 , and  608  are located at each of the gaps. The PIN diodes  602 ,  604 ,  606  and  608  are coupled to the direction decoder circuit  408  by control lines  622 ,  624 ,  626 ,  620  respectively. Antenna steering is accomplished by supplying one of the antenna loop switch control signals generated by the direction decoder circuit  408  to each of the PIN diodes which serve as switches. Opening or closing these switches in controlled combinations can steer the antenna pattern. 
     In various implementations of the lines  620 ,  622 ,  624 ,  626  used to supply control voltages to the PIN diodes are arranged to have minimal impact on the antenna pattern, or the effects of the control lines are included in the pattern design. 
     Referring once again to  FIG. 3 , the receiver  310  sends a signal instructing the indoor antenna  302  to move its pattern to another location, at point in time determined by the controller  312 . The receiver  310  does not affect the steering/switching controls directly but through the direction decoder circuitry  408  included in the antenna. The control signal  700  from the receiver  310  is delivered on a digital bus. A serial bit stream can be implemented with adequate speed and can be used as a cost-effective way to supply the control signal  700  to the antenna  302 . As illustrated in  FIG. 4 , the mapping of the receiver&#39;s steering instructions to actual PIN diode control signals is the responsibility of the antenna  302 . 
     The direction instructions from the receiver  310  can take the form “move to the next possible position in a clockwise/counterclockwise direction”, or there could be unique codes for the available antenna positions. In the case where unique codes are used for each antenna position, the receiver  310  issues an instruction to move to a particular position. 
     The receiver  310  is responsible for searching for and identifying the optimum position under the direction of an optimum antenna positioning routine  510  (See, e.g.,  FIG. 5 ). The antenna and receiver communicate via an established protocol how many positions are available in one complete revolution of the pattern, the estimated switching time, etc. 
     The receiver  310  may have possible codes for more positions than are supported in the actual antenna  302 . If so, and if the receiver&#39;s search for an optimum position eventually directs the antenna to a state more “fine-grained” in position than the antenna actually offers, then the antenna&#39;s direction decoder  408  selects the closest available position automatically. Thus, position resolution can also be calculated in the receiver  310  even if the antenna  302  doesn&#39;t inform the receiver  310  of the number of available states it supports. The number of positions an antenna supports, along with information about the antenna&#39;s other capabilities is stored in a block of memory  422  in the antenna  302 . The antenna capabilities information  422  is communicated to a receiver  310  when the antenna  302  is first connected to the receiver  310  or whenever requested by the receiver module as discussed below. 
     Referring once again to  FIG. 4 , it can be seen that in addition to supplying the bits used for controlling antenna pattern direction to the direction decoder  408 , the decoder control  406  supplies the 2 bits from a received control signal used to control gain to the gain decoder  410 . In addition it supplies the 7 bits representing a channel number to the channel number to tuning voltage ROM  404 . The two bits of the control signal  700  used to control antenna polarization are supplied to polarization control circuit  412 . 
     The gain decoder  410  converts the 2 bit gain control signal into a voltage level which is used to control the gain of variable gain element  420 . Accordingly, the gain applied to the signal received by the antenna can be controlled by the receiver  310  through the use of control signal  700 . 
     Channel number to tuning voltage ROM  414  is implemented using a channel number to voltage look-up table. For a given channel number input, the ROM  414  will output the appropriate tuning voltage as indicated by the contents of its look-up table. Digital to analog circuit  416  converts the digital voltage value output by ROM  414  to an analog voltage signal which is used to control the parallel-tuned coil and varactor diode circuit  418  so that it is properly tuned for the channel to be received. 
     Antenna polarization is controlled by the two bits of the control signal  700  that are supplied to the polarization control circuit  412 . The polarization control circuit  412 , in response to the received control bits, generates a switching control signal that is supplied to the controllable antenna loop  304  to control antenna polarization. In many embodiments, antenna polarization control is not supported and polarization control circuit  412  is omitted in such embodiments. 
     In order to minimize the number of wires between the indoor antenna and receiver  310  and the number of pins on the connector(s), communication is accomplished in some embodiments through the use of a self-clocking serial bus  311 . In addition to this bus  311  there will be the co-axial cable  313  (or twin lead). In some embodiments, a dc power line from the receiver  310  to the antenna  302  will also be included. 
     In cases where the antenna  302  supplies antenna information, e.g., position or capabilities information, to the receiver  310  a two-way bus  311  is used. However, in less advanced implementations where the antenna does not send information to the receiver  310 , a one-way bus is used. 
     Signals from the receiver  310  to the antenna may include, e.g.: 1) instructions to move the antenna to a different pattern position; 2) channel number information; and 3) other controls for pattern or gain depending on the implementation. Signals from the antenna to the receiver may include, e.g.: 1) information about the number of available pattern positions; 2) information about the speed of moving patterns (e.g., to allow for inclusion of mechanically steered antennas in this plan); 3) other information if available and/or needed. 
     The serial bus  311  carries digital signals, which radiate some amount of electrical noise into the antenna loop  304  and thus into the tuner  314 . The wires are arranged to minimize pick-up of such noise. Some embodiments may have high-pass filters in the signal leads to reduce the noise further. In other embodiments, it is possible to effect some control of the rise-time of the edges of the signals sent from the receiver  310  and antenna  302 . 
     The functions that are controlled by the receiver  310  include antenna pattern direction, antenna pre-amplifier gain, and antenna polarization. An antenna  302  is not required to implement all of these functions. In some embodiments antennas decode the instructions that it is capable of following and ignore the others. For example, a small indoor antenna may not have the ability to change polarization. Control signals from the receiver  310  to the antenna are considered “upstream,” while signals from the antenna  302  to the receiver  310  are considered “downstream”. 
     Although not required, the antenna  310  may have the ability to inform the receiver  310  when it has reached the new state to which it has been directed. Such a feature is useful when mechanical rotation of an antenna is used. This is because mechanical rotation takes different amounts of time to achieve the desired state depending on the amount of rotation to be performed. This makes it useful to receive a notification when the rotation has been completed. The antenna  302  may also inform the receiver  310  about the functions it is capable of implementing, the number of directional states it can resolve, etc., by sending the information stored in block  422  to the receiver  310 . 
     The upstream states and examples of the associated numbers of bits allocated in a control message are: 
     Direction: 
     In one embodiment, the bit stream can devote as many bits as practical to controlling the directional pattern, e.g., 8 bits, or 256 unique directional states, is an exemplary maximum for consumer products. Not all antennas will have 256 unique states, and simpler antennas will respond only to the higher order bits, e.g., defining 8 unique states by using only the 3 most significant bits. 
     Pre-Amplifier Gain: 
     In one embodiment, the bit stream can devote 2 bits to controlling gain of the pre-amplifier. The four states are: 1) pre-amplifier OFF; 2) low gain; 3) mid-level gain; 4) maximum gain. 
     Polarization: 
     In one embodiment, the bit stream can devote 2 bits to polarization, to enable horizontal, vertical, or circular polarization, if available in the antenna. 
     Channel Number: 
     In one embodiment, the bit stream devotes 7 bits to inform the antenna  302  of the channel selected. Use of these bits by the antenna  302  is optional. They are provided to enable band switching or tuning functions, if desired. 
     The downstream states and the associated numbers of bits are: 
     State Achievement: 
     In one embodiment, the antenna  302  informs the receiver  310  that it has reached the new state, e.g., position, to which it has been directed. One bit is sufficient for this function. This function will be most useful for slow-moving antenna pattern changes, such as those achieved with a motor and mechanical motion of the antenna. Electrically-steered patterns move more quickly and may not need this signal. 
     Antenna Functionality: 
     In one embodiment, the antenna  302  informs the receiver  310  what functions it is capable of implementing. For example antenna  302  describes the number of states it supports for each of the above antenna functions. In one embodiment, 8 downstream bits tell the receiver  310  how many directional states will actually be used, 2 additional bits are used to indicate the number of available gain states, and 2 more bits specify the available polarization states if any. This information is held in block  422  of the antenna  302  and is transmitted to the receiver  310 , e.g., at power up or when requested. 
     Information from the antenna  302  to the digital receiver  310  is sent very infrequently, and, in some embodiments, only at the request of the digital receiver  310 . For example, the information can only be sent for initialization at the first connection, and thereafter it can be stored in the receiver  310 , e.g., in memory block  508 . Alternatively, it could be sent each time the receiver  310  and antennas  302  are turned on. This procedure minimizes any effects of signal radiation and interference from the control bus  311 . 
     The interface and the coding between the antenna  302  and the receiver  310  can include: 
     1) Low Complexity and Low Speed 
     In one embodiment, the interface uses a serial bit stream on single wire bus  311 . The interface is bi-directional, enabling state information to be relayed from the antenna  302  to the receiver  310  and control information to be transferred from the receiver  310  to the antenna  302 . A one-wire interface can provide both “upstream” and “downstream” directions of information flow. In addition, the single wire can provide DC power from the receiver  310  to the antenna  302 . In one particular embodiment the RF signals containing the received TV signals are also carried on this single wire. 
     The serial information is sent at a &lt;9 KHz bit rate to minimize RF interference into the DTV receiver&#39;s tuner  314 . The control and information bit stream is turned off unless the receiver  310  is actually changing the antenna state or receiving antenna information. Thus, during normal program viewing, the digital antenna control and information signals do not exist. 
     The code used to communicate antenna control signals and antenna information is self-clocking for simplicity, to effect synchronization easily between receiver  310  and antenna  302 , and to minimize the frequency of all components. 
     2) No DC Component 
     In one embodiment, the serial bit stream is desirably coded so that there is no DC component. This enables the wire to carry a DC voltage to power the antenna without disrupting the communications channel used to transmit antenna control signals and information.
 
3) Standard and Simple Technology
 
In one embodiment, the code used to transmit antenna control and information signals is a well-known Manchester code, for which standard algorithms and simple encoder and decoder implementation are available.
 
     The controller  312  of receiver  310  is responsible for implementing the antenna control method of the invention. As illustrated in  FIG. 5 , the controller  312 , which may be implemented as a microprocessor, includes a processor  502 , input/output module  504 , and memory  506 . Memory  506  includes antenna information  508 , antenna positioning and control routine  510 , and antenna preset information  512 . Memory  506  includes a block of memory  514  used to store an antenna state information associated with each channel. Thus the receiver  310  may include sets of antenna information for each channel. Different sets of state information may be stored for each of a plurality of different antennas. In the antenna  302 , there need not be a priori compass direction information—the receiver  312 , under direction of the antenna control and position routine  510  searches the circular (or spherical) antenna space without regard to compass. The search may comprise stepping around the full circle from one state to its adjacent neighbors. The directional coding supports the notion that high order bits define the “big” directions, and so changing high order bits moves the pattern in large increments. “Fine-tuning” is accomplished by the lower order bits. Antennas of different complexity may or may not use all of the bits—i.e., low-complexity antennas with relatively few discrete pattern states may respond only to the high order bits. More complex antennas may use all of the pattern-defining bits. Note that this application supports all of these modes, and the antenna directional control values do not need to be defined uniquely for antennas or control algorithms of different complexity. 
     In order to enable synchronization between the antenna  302  and receiver  310  and to enable turn-off of the digital signal when not needed, in various embodiments a “barker code” of up to 13 bits preceding the data bits, e.g., the 19 bits of control signal  700 . If desired, another bit can be used to tell the antenna  302  that the next time slot is available for downstream transmission. A standard Manchester code, including parity bits if needed, meets these recommendations, and such a code also enables simple encoder and decoder designs. 
     Synchronization between antenna  302  and receiver  310  permits a known time slot for the downstream information bits, as identified above, to be sent from the antenna  302 . The disclosed concept does not require that these bits be sent, and receiver algorithms can, and in various embodiments are, designed to be effective without them. 
     In various embodiments, there is a “wake-up” procedure, associated with communications between the antenna  302  and receiver  310 . This is because, in general, the antenna&#39;s decoder&#39;s digital circuits will be OFF when the receiver  310  wants to initiate an antenna state change. One solution is for the receiver  310  to turn the antenna power OFF and then ON to signal a “power-on reset” that re-starts the antenna circuits&#39; clock to allow synchronizing to the barker code. 
     The control bit stream, e.g., signal  700 , is sent upon each channel change and under conditions where the receiver  310  determines that the error rate (or other measure of signal quality) is too poor. The bit stream continues to be sent until terminated by the receiver  310 , e.g., upon successful antenna optimization. 
     Hardware for the communications link is simple, of complexity comparable to Manchester coders/decoders used in Ethernet cards. 
     The link described above can be carried on the co-axial cable between the antenna and receiver  310  that also carries the RF signals. As described the serial bit stream is separable in frequency from the RF signals, and it contains no DC, thus enabling provision of DC power to the antenna on the same co-ax cable. Alternatively, a separate 2-, 3- or 4-wire physical interfaces could carry the power, control and antenna information signals. 
     If a co-axial cable is the interface where backwards compatibility is a concern, then the antenna  302  should form a dipole or other simple pattern in the event that it is plugged into a “legacy”, e.g., NTSC receiver, incapable of supporting the control signals of the present invention. 
     In accordance with the invention, multiple antennas may be used. This is particularly beneficial in mobile applications where the optimum antenna pattern position may vary frequently due to movement of the device in which the antenna is housed. In such an embodiment, while one antenna has its antenna pattern position adjusted, e.g., to maximize signal reception, the other antenna is used to receive information. Switching between the two antennas is used to maximize signal reception without the loss of signal reception during periods when the antenna pattern position is adjusted which might occur if a single antenna were used. 
       FIG. 8  illustrates a mobile system  800  implemented in accordance with a mobile embodiment of the present invention. The system  800  maybe, e.g., notebook computer, personal data assistant (PDA) or even a cell phone. Two antennas modules  302 ,  302 ′ are used to allow adjustment of one antenna position pattern in accordance with the invention while the other antenna  302  or  302 ′ is used to receive information, e.g., data or other signals. Each of the antennas  302 ,  302 ′ is coupled to a receiver module  804 . The receiver module  804 , in turn, is coupled to a central processing unit (CPU)  812 . The central processing unit (CPU)  812  is coupled to input/output devices, e.g., display  814  and keyboard  816 . The CPU  812  receives information, e.g., data or other signals, from the receiver module  804  which is processed and/or displayed on the display  814 . 
     The receiver module  804  includes two antenna pattern position control circuits  806 ,  806 ′ which are used to direct, e.g., control, the position of the antenna patterns of antennas  302 ,  302 ′ in accordance with the invention. The circuits  806 .  806 ′ may, but need not, include full demodulators. Antenna selection circuit  808  is coupled to a each of the antenna pattern position control circuits  806 ,  806 ′ and selects between the antenna outputs from each of these circuits. In this manner, the signal from one of the antennas  302 ,  302 ′ will be supplied to signal processor  810  at any given time. Signal processor  810  is responsible for decoding the received signal prior to supplying it to CPU  812 . 
     By adjusting the position of one of the antenna patterns corresponding to antennas  302 ,  302 ′ at a time while using the output of the other antenna  302 ,  302 ′ as the input to the signal processor  810 , signal antenna pattern position adjustments can be continually made without interfering with signal reception. 
     While  FIG. 8  illustrates selecting between the output of two antennas with adjustable antenna patterns, in various embodiments of the present invention multiple, e.g., four or more, antennas with different fixed antenna patterns are used. In one such embodiment each antenna pattern has at least one high gain region and one low gain, e.g., null, region with the orientation of each antenna pattern relative to the receiver device being different. Multiple identical antennas, e.g., each having the same antenna pattern, e.g., the antenna pattern illustrated in  FIG. 2 , mounted with different orientations may be used in such an embodiment. 
     In accordance with the invention, the output of one of the plurality of antennas is selected, as a function of a signal, e.g., noise measurement, to be used at any given time. For example, the antenna output with the lowest signal to noise ratio may be selected to be demodulated and displayed. In this manner, an antenna with a pattern having a null aligned with a signal interference source may be preferred over another antenna which has a greater received signal strength but also more interference. In this manner, a device can obtain the benefit of selecting an antenna pattern with a signal interference source located in an antenna pattern null without having to use antenna&#39;s with steerable patterns or the control circuitry associated therewith. 
     By using the antenna pattern adjustment techniques and/or by selecting between the outputs of a plurality of antennas with low gain regions located at different positions, broadband and other wireless communications are supported in portable devices in accordance with the invention. 
     Numerous variations on the above described embodiments of the present invention are possible without departing from the scope of the invention. For example, a general purpose processor, e.g., CPU, may be programmed to perform antenna control signal decoding operations in addition to antenna control operations. In one such embodiment the decoder/control logic  404  is implemented using a CPU and memory which stores the software used to control the CPU to perform the decoding and control operations.