Patent Application
20140091976
Improved antennas and a transceiver for UHF wireless communications are disclosed.
Broadcast analog TV in the UHF bandwidth is well-known in the art. Due to the migration from analog to digital TV, that allows channels to be adjacent, stations were able to relocate and pack together into the upper VHF and lower UHF portions of the spectrum. The areas abandoned are often referred to as “TV White Space.”
Various antenna designs also are well-known in the art. Examples of antenna structures include cylindrical dipoles, biconical dipoles, and log-periodic antennas.
Transceivers for use with antennas also are well-known in the art.
However, in the past, the UHF bandwidth has not been used for purposes other than analog TV broadcast. TV transmission equipment and their antennas are designed for extremely large amounts of power. What is needed is improved antennas and transceivers that are suitable for broadcasting other content—such as data and voice communication—over the UHF bandwidth using dramatically less power than broadcast TV.
The aforementioned problems and needs are addressed by two novel antenna designs particularly suited for UHF communication and an improved transceiver for use with those antennas.
Two antenna embodiments and one transceiver embodiment will now be described.
Cylindrical antennas are known in the art. Biconical antennas also are known in the art. However, the applicants have found that a novel cylindrical-biconical hybrid antenna is particularly well-suited for UHF communication.
An embodiment is shown in
Hybrid antenna 10 comprises two sets of dipoles 20 and 40. Dipole 20 comprises upper structure 21 and lower structure 22. Dipole 40 comprises upper structure 41 and lower structure 42. Dipoles 20 and 40 are mounted upon center pole 50. Center pole 50 is constructed from a non-conductive material such as fiberglass. Antenna lead 60 runs within or along center pole 50. Antenna lead 60 comprises a conductive material, such as a coaxial cable. Antenna lead is coupled to connector 70 (shown in
With reference now to
The components of dipole 20 will now be described with
Lower structure 21 comprises outer ring 23 and inner ring 24. Lower structure 21 further comprises elements 25a1 . . . 25ai. Upper structure 22 comprises outer ring 26 and inner ring 27. Upper structure 22 comprises elements 28a1 . . . 28ai.
In the embodiment shown in
As can be seen in
Dipole 40 is identical in design as dipole 20, except that it connects to segment 62 instead of segment 61.
The distance between the center of dipole 20 and the center of dipole 40 is equal to the wavelength of the median frequency of the intended spectrum.
As can be seen, dipole 20 and dipole 40 each is a cylindrical, biconical hybrid. Outer ring 23, inner ring 24, outer ring 26, and inner ring 27 in dipole 20 and the corresponding parts in dipole 40 are characteristics of a cylindrical antenna. Elements 28a1 . . . 28ai and elements 25a1 . . . 25ai in dipole 20 and the corresponding parts in dipole 40 are characteristics of a biconical antenna.
The applicants have confirmed that the disclosed embodiment is capable of transmitting and receiving a bandwidth of 470 MHz to 800 MHz with a gain approaching 6 dB over an isotropic antenna.
Boom 110 and boom 120 contains elements 160a1 . . . 160ai. In this particular example, i=15. One of ordinary skill in the art will understand that i can be set to other values. Elements 160a1 . . . 160ai transmit and receive UHF signals. The height and relative placement of elements 160a1 . . . 160ai affect the properties of the antenna.
For this embodiment, Table 1 contains the height and relative placement of each element 160a1 . . . 160a15:
One of skill in the art will appreciate that the heights shown in Table 1 correspond to an average tau value of 0.945.
As can be seen in
The inventors have built and tested this embodiment. It is capable of transmitting and receiving frequencies in the range 450-800 MHz in a sector of approximately 90 degrees with a gain of approximately 10 dBi over an isotropic antenna.
One embodiment is an input impedance matching circuit 210 that is well-suited for the full bandwidth of the TV broadcast band used for UHF transmission.
Impedance matching circuit 210 is shown in greater detail in
The allowable emissions on radio frequencies outside the intended area of transmission (channel) are very restricted by federal regulations and the FCC, and thus, the matching requirements in the amplification section need to be heroic to obtain level power over bandwidth. A method is needed to add and subtract matching capacitance at the correct phase location according to transmit frequency selected. A process of experimentation with RF tuning diodes, high Q capacitors and forward and back-biased voltages was done to determine a method that would be successful in achieving the correct match over the band. An embodiment is depicted in
The default setting for back-biased diodes 310, 320, 330, and 340 is to be in an “off” state. Each will be turned “on” if a certain voltage is placed between it and capacitors 350 and 360. Those voltages will be placed there by frequency sensing circuit 390 based on the frequency of UHF output 300. The frequencies that will turn each diode “on” is shown in Table 2:
When a diode is turned “on,” the path between UHF output 300 and ground will become conductive through that diode, and capacitors therefore will be coupled to UHF output 300. For example, when diode 310 is turned on, capacitors 350 and 370 will become coupled to UHF output 300. This will add matching capacitance at the correct phase location according to the transmit frequency that is sensed by frequency sensing circuit 390.
In the foregoing description, various methods and apparatus, and specific embodiments are described. However, it should be obvious to one conversant in the art, various alternatives, modifications, and changes may be possible without departing from the spirit and the scope of the invention which is defined by the metes and bounds of the appended claims.
