The present disclosure generally relates to antenna assemblies such as those configured for reception of television signals, including high definition television (HDTV) signals.
Many people enjoy watching television, and the television-watching experience has been greatly improved due to HDTV. Although a great number of people pay for HDTV through their existing cable or satellite TV service provider, in fact, HDTV signals are required to be broadcast over the free public airwaves. This means that HDTV signals may be received for free with the appropriate antenna.
Modern homes often have several TV sets located in multiple rooms, for example, in living rooms, bedrooms and family rooms, where different individuals may be simultaneously watching dissimilar TV program channels. Such homes have TV signal distribution wiring which typically carries signals from a single antenna location and distributes them to each set location.
However, often the signals for different channel frequencies arrive at the antenna from different transmitter directions. Available antennas are usually optimized for highest signal sensitivity, meaning that they have relatively narrow acceptance angles, so pointing the antenna for best reception of one channel might not be optimum for receiving another channel. This creates a problem when the same antenna is to be used for receiving more than one channel at a time.
In the past, the direction problem has been addressed by using a) a motorized antenna rotator to aim the antenna toward the broadcast being watched, b) an array of antennas, each aimed toward different arriving signals, or c) an omni-directional antenna. The first solution does not solve the multiple-viewer issue and adds cost and inconvenience; the second solution requires that the antennas in the array be at least one wavelength apart at the lowest frequency and have electrical isolation, i.e. separate amplifiers or filters associated with each antenna in the array, the result of which is both bulky and expensive; and the third solution is mainly applicable in close proximity to the TV transmitters because omni-directional antennas generally have low signal sensitivity and no directions from which the antenna can reject interfering signals.
Various antennas and/or antenna/reflector combinations, such as wideband antennas and bow-tie antennas, are disclosed in U.S. Pat. Nos. 2,918,672, 3,373,432, 4,160,980, 4,293,861, 6,466,178, 6,480,168, 7,050,013, 7,990,332, 8,674,897, 8,773,322, 8,994,600, 9,281,566.
Most HDTV digital signals are broadcast in the high UHF band from 470 to 710 MHz. Therefore, a need exists to provide a compact UHF antenna optimized to receive high definition television (HDTV) digital signals in the UHF band. A further need exists for a wide beam width antenna with high interference rejection. Yet a further need exists for a UHF antenna with good sensitivity. Another need exists for a low cost HDTV antenna for use outdoors or indoors that has an aesthetic appearance. Furthermore, a need exists for such an antenna to be easily constructed for low cost using conventional manufacturing methods and materials.
Many antennas are based upon the dipole principle. Starting with a basic dipole element, many antenna designs add passive elements, such as directors and/or reflectors, to enhance their performance in order to achieve certain performance goals. For example, the well-known Yagi-Uda antenna design employs this method to enhance the sensitivity in a desired direction, at the expense of sensitivity in other directions. In other words, the Yagi antenna has good gain, but is highly directional. The use of added passive elements is particularly true of terrestrial television (TV) antenna designs where the extra elements help to improve their signal capturing gain, but also where this method limits the ability of such antennas to simultaneously receive signals from multiple directions.
Since in North America, terrestrial TV signals are required to be horizontally polarized, i.e. the e-field lies in the horizontal plane, TV antennae must be designed to pick-up such signals. The basic horizontal dipole antenna is horizontally polarized, so it has an antenna pattern which is omni-directional in the vertical plane, but has a figure-8 shape in the azimuthal (horizontal) plane. Thus, the dipole has maximum sensitivity when the signal approaches from the broad side of the antenna, but no pick-up sensitivity when the incoming signal approaches from the ends of the antenna.
Antenna gain is specified as the ratio of sensitivity in the direction of greatest signal pick-up to that of a reference antenna, expressed in decibels (dB). The reference antenna is commonly taken as a hypothetical intrinsic antenna—one with equal sensitivity in all directions—so the gain is expressed in dBi, where the “i” indicates that the reference being used is the intrinsic antenna. In the direction of maximum sensitivity, i.e. when the incoming signal approaches broadside to the antenna, the dipole has a (maximum) gain of about 2 dBi.
In turn, the half power beamwidth (HPBW or 3 dB down BW) is approximately 70 degrees. Note that at the edges of the beam, the gain is −1 dBi which is actually less than that of the intrinsic antenna. Thus, the low gain and narrow beamwidth of the unaided dipole makes it a poor candidate for TV reception, in spite of its wide use in the common “rabbit ears” design.
One approach to improving the gain of a dipole antenna is to add a passive reflector behind the active dipole in order to redirect incoming energy, which has not been captured and has passed by the dipole, back toward the dipole. Such reflectors are highly effective. An extreme example is the parabolic dish antenna used for radio astronomy or spacecraft communications, where many tens of dBi of gain are achieved, yet still using only a dipole as the active element. However, whenever a reflector is used to improve gain, there is a sacrifice in beamwidth. The above mentioned dish antennas have extremely narrow beamwidths, which is beneficial for radio astronomy or space communications, but not necessarily for terrestrial TV reception. When adding even a simple plane reflector behind a dipole, the maximum forward gain can be increased to over 7 dBi, but the beamwidth then decreases to less than 65 degrees.
In virtually all terrestrial TV reception antenna designs, both halves of the dipole are energized by the same electromagnetic (EM) wave. Even with a reflector, where the dipole receives energy from two directions at once, there is no difference between the energy arriving at each half of the dipole. This is also true when directors are added to the design. The active dipole element “sees” the same signal energy and amplitude at each half, and in-phase, as is required for proper operation.
In the conventional configuration of
Described herein is a compact digital television antenna that uses a unique design to increase the width of the reception angle to produce a substantially wider beam width than conventional antennas without increasing antenna size. The antenna described herein can achieve beam widths of greater than 130 degrees, while maintaining virtually constant, and relatively high, sensitivity over the entire angular range, and excellent rejection of interfering signals arriving from the rear of the antenna and above/below the antenna. This inherent interference rejection allows for low unwanted-signal interference, and provides a clean signal to the receiving apparatus.
The antenna is configured to electrically match its load impedance for maximizing the signal transferred to the load and minimizing signal reflections within the transmission line connecting the antenna to the load (e.g. television set). The antenna described herein has a remarkably accurate impedance match to the universal impedance of 300 Ohms across its extremely wide bandwidth of operation.
In certain embodiments, the antenna consists of two swept back V-shaped dipoles arranged one above the other, and spaced slightly in front of a planar reflector. The dipoles are supported at their corners by insulating elements. A feed assembly of conductors carries the received signal to a central location where an insulating connecting “block” is conveniently located for making the output connection, either directly to 300 Ohm feed line, or via a “balun transformer” to match the impedance to a different value, for example the commonly used 75 Ohms coaxial feed line. The balun transformer may be separate, or housed within the connecting block. The front of the V-shaped elements is held separated by two insulating bars. Thus, in certain embodiments, the entire antenna consists of four main V-shaped active elements, two Y-shaped feed elements comprising the feed assembly, seven insulators of only three different shapes and the planar reflector.
The antenna described herein can be used for either or both receiving and transmitting.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more examples of embodiments and, together with the description of example embodiments, serve to explain the principles and implementations of the embodiments.
In the drawings:
Example embodiments are described herein in the context of an antenna. The following description is illustrative only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to those of ordinary skill in the art having the benefit of this disclosure. Reference will be made in detail to implementations of the example embodiments as illustrated in the accompanying drawings. The same reference indicators will be used to the extent possible throughout the drawings and the following description to refer to the same or like items.
In the description of example embodiments that follows, references to “one embodiment”, “an embodiment”, “an example embodiment”, “certain embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. The term “exemplary” when used herein means “serving as an example, instance or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer's specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure.
Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.
The configuration of the wide-direction antenna 20 allows both the upper (22a) and lower (22b) halves of the dipole to be excited by energy arriving broadside to each half—the lower half being energized by the incoming EM wave and the upper half being energized by the reflected EM wave. (It should be noted that the terms “upper” and “lower” are used for convenience only and do not denote a preferred orientation of the antenna.) This is because the dipole is only sensitive to EM energy arriving broadside to the element and is insensitive to energy arriving from the ends—that is, from the end-fire direction. Thus, the wide-direction antenna 20 design is notably different from conventional antenna designs in that the individual halves of the active dipole are energized by different sources of energy. In particular, the reflector 24, the first element 22a, and the second element 22b are configured to orient the first element 22a substantially broadside to the reflected EM radiation and end-fire to the incident EM radiation when the second element 22b is oriented substantially broadside to the incident EM radiation. The converse, of course, is also true: the reflector 24, the first element 22a, and the second element 22b are configured to orient the second element 22b substantially broadside to the reflected EM radiation and end-fire to the incident EM radiation when the first element 22a is oriented substantially broadside to the incident EM radiation. Moreover, although the discussion herein relates to reception of incoming EM radiation, the same principles apply for transmission of EM signals by antenna 20, as is expected in the antenna art.
Of course, in both the conventional design of
The wide-direction antenna 20 operates similarly to a conventional dipole antenna when the signal comes from straight ahead—that is, both halves of the dipole receive equal energy both from the direct arriving EM wave and also from the reflected EM wave. Thus, the performance of the wide-direction antenna 20 is similar to the conventional design over a range of acceptance angles close to “straight ahead”. Where the wide-direction antenna 20 differs is that this performance is maintained out to much greater acceptance angles than the conventional designs. In other words, the new design has a much greater beam width. Beam widths of nearly 180 degrees can be achieved with the wide-direction antenna 20 design.
Besides having a very broad beam width, another advantage of the wide-direction antenna 20 design is that it allows for a smaller, more compact antenna. The two designs of
In addition, the wide-direction antenna 20 has improved signal interference/multipath performance. Although the addition of a reflector does reduce the conventional dipole's sensitivity to interference and multipath signals arriving from the rear of the antenna, the excess omni-directional dipole's sensitivity in the vertical direction allows for the pick-up of spurious interfering and multipath signals from, for example, aircraft flying overhead and/or electronics or motors etc. located below the antenna. Since all TV transmissions originate from broadcast stations on the ground (i.e. in the horizontal plane), there is no need for the excess vertical sensitivity and instead it is a liability. The wide-direction antenna 20, by comparison, exhibits significantly reduced vertical sensitivity, as can be seen from the vertical cross-section beam patterns described infra. Because of the relatively narrow vertical beam shape, the wide-direction antenna 20 also displays significantly reduced interference pick-up, providing a much cleaner signal for better TV viewing, while still maintaining excellent sensitivity for TV signals coming from multiple azimuthal directions.
As there are many types of dipole antennas, for example, the simple and folded dipoles, the bowtie (see, for example, U.S. Pat. No. 2,175,253), biquad, biconical (see, for example, U.S. Pat. No. 2,267,889), etc., it is beneficial that the wide-direction antenna design principle described herein works with nearly all of them. Therefore, it is possible to utilize the disclosed design for broadening an antenna's beam width to enhance the performance of many conventional antenna designs. It should be noted that, due to the large element tip diameter of the prior art biconical dipole, a half-bicone should be used so the rearward canted dipole shape can be accomplished without the element ends touching, or shorting to, the reflector.
In addition, known antenna bandwidth widening methods, such as using large diameter dipole elements, and tapered, or triangular, dipole elements are all compatible with the V-shaped elements used herein and are just one example for broadbanding an antenna. All known such methods are compatible with the wide-direction antenna 20, providing further advantages of the design.
Turning to
In
In addition, with reference to
In the simplified view of
In certain embodiments, the four V-shaped conductors 46 are arranged substantially symmetrically about a center point of the antenna, protruding forward of the reflector 44 at approximately 45 degrees (
Signal-combining feed harness 48 is made of ⅛″ aluminum in certain embodiments, and serves to connect the apex of each V-shaped conductor 46 to a signal output point, for example located in the center of the antenna, as described below. In particular, harness portion 48A is electrically coupled to the apex of V-shaped conductors 46A1, 46A2 of dipole element 46A, and harness portion 48B is electrically coupled to V-shaped conductors 46B1, 46B2 of dipole element 46B. Another function of the feed harness 48 is to act as an impedance matching transformer to assure that the overall output impedance of the antenna has the characteristics shown in
In
As seen from
One consideration in designing an antenna is how it can be mounted, whether indoors or outdoors. Such consumer antennas are usually mounted to a vertical mast made of metallic tubing, which provides a convenient means for adjusting the height and azimuthal pointing angle. Such a mast 64 is shown in
Directional reception performance in the horizontal, or azimuthal, plane of a wide-direction antenna such as antenna 42 is shown in
The structure of antenna 42 is one of many possible configurations that meet the specifications described herein. As another example,
The antennas described herein are scalable in frequency. However, when scaling the antennas, the resulting reception patterns may alter. Further tuning and adjustments of the antenna segments after scaling can be used to achieve the same, or nearly identical, performance, without departure from the spirit or scope of the invention.
While embodiments and applications have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts disclosed herein. The invention, therefore, is not to be restricted based on the foregoing description. This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.
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