MXPA00005219A - Multi-band helical antenna with varying pitch - Google Patents

Abstract

A helix antenna 129 for multi-band operation is achieved according to the present invention by varying the pitch angle, represented by s1 and s2, on the helical coil in a suitable manner. In particular, by using an non-uniform pitch angle and keeping the total length of the wire constant, the second resonance of the antenna can be shifted high or low as a function of the pitch angle, while the first resonance is not affected. The diameter, d1 and d2 of the portions of the helical coil can be varied according to alternate embodiments of the invention. The antenna 129 is contained within an outer housing (Fig 11, 902) and connected to the wireless communication device(1130) via a monopole 802.

Description

HELICOIDAL ANTENNA FIELD OF THE INVENTION This application refers to an antenna and more particularly to an "helical" antenna adapted to operate in more than one frequency band. BACKGROUND- E- THE INVENTION With the increasing increase of wireless communication devices ^ the spectrum 'has become scarce, in many cases the network operators provide services in a particular band, and have an id -proveer- serv In a separate band to accommodate its customers, for example "network operators that provide service" ~ err a GSI ^ system in a 900MHz frequency band have to rely on a "DCS err" band or ^ -frequency- "of 180O Mffz. Therefore, wireless communication devices, such as "cellular radio" telephones, must be capable of communicating on both frequencies or even on a third system such as PCS 190O. Such a requirement to "function-in-dss or more frequencies produces several problems." For example, the wireless single-wire device must have an antenna adapted to receive signals in more than one frequency band. Also, as the wireless positioning devices decrease in size there has been a need to reduce-associate ssrr ~ e-dispositivcr. Also- while nailing HELICOIDAL ANTENNA FIELD OF THE INVENTION This application refers to an antenna and more particularly to a helical antenna adapted to operate, in more than one frequency band. BACKGROUND OF THE INVENTION With the increasing increase in wireless communication devices, the spectrum has become scaled, in many cases the network operators provide services in a particular band, and have had to provide service in a separate band to accommodate their clients. , for example network operators that provide service in a GSM system in a 900MHz frequency band have to rely on a DCS system in a frequency band of 1800 MHz. Therefore, wireless communication devices, such as cellular radio telephones they must be able to communicate on both frequencies or even in a third system such as PCS 1900. Such requirement to operate in two or more frequencies produces several problems. For example, the wireless communication device must have an antenna adapted to receive signals in more than one frequency band. Also as the wireless position devices decrease in size there has been a need to reduce associated with the device. In addition, while an extendable antenna offers certain advantages, such an antenna establishes problems for an end user, because the antenna will typically work better. In an extended position, the user is required to extend the antenna before operating the wireless communication device. As a result many end users prefer a fixed antenna that does not need to be extended during the operation, from a design point of view, it is also considerably more difficult to attach a retractable antenna both in the up and down positions when the antenna is designed to operate in two or more frequency bands.- A helical antenna can have several resonance frequencies as a function of the wire length, angle of inclination and the number of turns. Usually, these resonance frequencies can be adjusted using suitable techniques to obtain an operation of a single cellular band or of a later one. These techniques may include varying the dimensions of the wire and / or adding other components. A helical antenna having a uniform angle of inclination can be tuned to operate in a GSM band (900 MHz) however, the second resonance mode will not be in the DCS bands (1800MHz or PCS "1900 MHz) any change in the length of wire, diameter and angle of inclination, will displace both the high and low resonant frequencies thus making the operation impossible for the desired frequencies.There is therefore a need for a small helical antenna adapted to receive signals in multiple frequency bands. DESCRIPTION OF THE DRAWINGS FIGURE 1 is a block diagram of a wireless communication device such as a cellular radio telephone, according to the present invention; FIGURE 2 is a helical coil antenna according to the present invention; FIGURE 3 is a helical coil antenna according to an alternative embodiment of the present invention; FIGURE 4 is a helical coil antenna according to an alternative embodiment of the present invention; FIGURE 5 is a helical coil antenna according to an alternative embodiment of the present invention; FIGURE 6 is a helical coil antenna according to an alternative embodiment of the present invention: FIGURE 7 is a helical coil antenna coupled to a coaxial transmission line according to an alternative embodiment of the present invention; FIGURE 8 is a helical coil antenna harnessed to a monspolo according to an alternative embodiment of the present invention; FIGURE "9 is a cross-sectional view of the antenna of FIGURE 8 according to the present invention: FIGURE 10 is a plan view of an encapsulated antenna of FIG. 8 according to the present invention. invention, and FIGURE 11, is a partial perspective view of an antenna according to the present invention coupled to the wireless communication device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION According to the method and apparatus set forth herein Description, a fixed type antenna formed by a single helical wire does not have a uniform angle of inclination.The dual band operation is obtained according to an embodiment of the invention by adjusting the total length of the wire for the lower band and the angle of inhomogeneous tilt for the high band, in particular with the use of a non-uniform tilt angle and keeping the total length of the wire constant according to the present description, the The resonance can be shifted up or down as a function of the angle of inclination as long as the first resonance is not affected. According to other embodiments of the invention, the diameter of the helical coil can be varied to achieve multi-band operation. Considering first Fig. 1, there is shown a block diagram of a wireless communication device, such as a dual band cellular telephone radio that incorporates the present invention. In the preferred embodiment, an ASIC 101 frame generator, such as a CMOS ASIC obtainable from Motorola, Inc., and a 1Q3 microprocessor, such as a 68HC11 microprocessor, also obtainable from Motorola, Inc., are combined to generate the protocol. of communication necessary to operate in a cellular system. The microprocessor 103 uses the memory 104 comprising RAM 10.5, EEPROM 107, and ROM 109, preferably consolidated in an ili package, to perform the steps necessary to generate the protocol and perform other functions for the communication unit such as writing to a screen 113 accept information from a keyboard 115, control a frequency synthesizer 125 or perform steps necessary to amplify a signal according to the method of the present invention. ASIC 101 ~ processes the audio transformed by the audio circuit 119 from a microphone 117 to a speaker 121. A transducer processes the radio frequency signals. In particular, a transmitter 123 and 124 transmit through an antenna 129 using carrier frequencies produced by a frequency synthesizer 125. The information received by the antenna 129 of the communication device enters the receivers 127 and 128 through a network of coupling and a 130 transmitter / receiver switch.

A preferred coupling network and a transmitter / receiver switch 130 will be shown in greater detail in Fig. 10. Receivers 127 and 128 demodulate the crue symbols comprising the message frame using the frequencies carriers of the frequency synthesizer 125. Transmitters and receivers are collectively called a transducer. The communication device may optionally include a message receiver and storage device 131 including means for processing the digital signal. The message receiving and storage device may be, for example, a digital answering machine or a locating receiver. A helical antenna is suitable for telephone and cellular communications due to the considerations of size and polarization. A simple helical antenna N turnsEach turn has a diameter d and the space between the turns is s. The antenna height of the antenna is h = Ns and the length of the wire is 1 = N lo. Here is the length of the wire between each turn. The angle of inclination is defined as the inverse tangent of the ratio s / d. Usually when the dimensions of the antenna are small at wavelength, the antenna is in a normal mode of operation and the radiation characteristics are similar to that of a quarter-wave monopole, but the profile (at the height of the helical antenna) is much smaller (shorter) than the monopole. The helical antenna provides an elliptical polarization which is a useful feature especially when the antenna is rotated an angle with respect to a linearly polarized fixed transmitter. A good example is when the user keeps the cell phone at various angles and the antenna will still be able to receive signal from the base station linearly polarized and fixed, since an elliptical polarization can be decomposed into two orthogonal linear polarizations. A helical antenna can have several resonant frequencies as a function of the length of inclination angle and number of turns. Usually these resonance frequencies can be adjusted using suitable techniques to obtain a single band or a cellular band operation. Those techniques may include varying the dimensions of the helical wire and / or adding other components. A helical antenna having a uniform angle of inclination can be tuned to operate in a GSM band (900 Mz). However, the second resonance mode will not be in the DCS (1800 MHz) or PCS (1900 MHz) bands. Any change in wire length diameter and tilt angle will displace the high or low resonant frequencies thus making multi-band operation impossible. A multi-band operation can only be achieved if the angle of inclination is modified in a suitable manner. In particular with the use of a non-uniform angle of inclination and keeping the total length of the wire constant according to the present description, the second resonance can be moved high or low as a function of the angle of inclination, while not being affected. the first resonance. Considering now Fig. 2, a helix with decreasing angle of inclination will move the second resonance closer to the first. In particular, a propeller has a feed point 203 coupled to a first portion 202 that extends at a height r "from a proximal end 204 to a distal end 206 and with an inclination represented by Si. Although the inclination can be set at Through the first portion 202, sl could "" represent an average pitch or pitch that would vary through the first portion 202. The diameter of the helical coil through the first portion 202 is represented by D. The helix also has a second portion 208 that extends a height p2 from a proximal end 210 to a distal end 212 and has a pitch or tilt represented by s2 Although the step s2 could be set through the second portion 208, s2 could represent an average of step that could vary through the second portion 208, where s2 is different from sl.The diameter of the helical coil for the second portion 208 is represented by d2, in the embodiment of Fig. 2, x is equal to d2. Considering now Fig. 3, a helix with an increasing pitch angle will move the second resonance away from the first. In particular, a propeller has a feed point 301 coupled to a first portion 3,02 that extends a height px from a proximal end 304 to a distal end 306 and has a tilt step represented by s ... Although the step sl could be set through the first portion 303, sl could represent an average of one step that would vary through the first portion 302. The diameter of the helical coil through the first portion 302 is represented by di. The helix also has a second portion 308 that extends a height p2 from a proximal end 310 to a distant height 312 and has a pitch represented by s2. Although step s2 could be set through the second portion 308, s2 could represent an average of a step that would vary through the second portion 208, where s2 is different from sl. The diameter of the helical coil through the second portion 308 is represented by d2. In the modality of Fig. 3, say, es = a d2. The design process can be chosen as the total wire length as the variation parameter to align the AMPS / GSM band first and then adjust the angle of inclination until the second resonance aligns with the DCS band. The total length of the antenna can be selected by the number of turns and the diameters of i, as well as two portions of the coil. The bandwidth and loss of return can be improved "more" by using a suitable coupling circuit which is well known in the art. The efficiency of the non-uniform pitch or pitch antenna is measured as better than 80% at the center frequency of each band. According to alternative embodiments of the present invention, the diameter of the coil can also be varied, eating is shown in FIG.4, the diameter of a first portion 402 of the coil extending from a proximal end 404 to a distal end 406 is generally greater, while the diameter of a second portion 408 of the coil extending from a "proximal end 410 at a distal end 412 is generally smaller, in particular a propeller having a feed point 401" engages a first portion 402 having a pitch or tilt represented by "sl, the diameter" of the The helical coil for p1 is represented by d- .. The helix also has a second portion 408 ~ with a pitch represented by s2 The diameter of the helical coil for p is shown for d.22 In the embodiment of Fig-. 4, dx is greater- than d2.

In contrast, the diameter of the lower portion of the coil in the embodiment of FIG. 5 is generally smaller, while the diameter of the upper portion of the coil is generally larger. In particular a propeller having a feed point 501 arrayed to a first portion 502, extends from a proximal end 504 to a distal end 506 and has a pitch represented by Sj., The diameter of the helical coil through the first portion 502 is represented by dx. The helix also has a second portion 508 that extends from a proximal end 510 to a distal end 512 and has an or inclination represented by s3. The diameter of the helical coil through the second portion 508 is represented by d2. In the mode of Fig. 5, dj. is less than d2. Although the step s-, and s2 could be set through the first and second portions 302 and 308 in the embodiments of Figs. 4 and 5, could represent a step average that would vary through the respective portions. Similarly, although the diameters dL and d2 are preferably fixed they could also vary according to the present invention. Also, although the diameters x and d2 could be fixed in Figs. 4 and 5, could also represent the average of the variable diameters through the portions 402 and 408. Considering now Fig. 6, an alternative embodiment of the present invention includes both variable pitch or inclination and variable diameter. In particular, both the step and the diameter decrease from a proximal end 604 of the antenna (near a feed point 605) to a distant end 606 of the antenna. Although a combination of variations is shown, any combinations of pitch and diameter variation including a pitch or fixed diameter and the relative locations of varying the diameter or pitch, fall within the scope of the present invention. Also more than two segments of varying diameter or pitch, may be employed according to the present invention. Considering now Fig. 7, a coaxial transmission line is gathered at the feed point of the helical coil, in particular a helical coil as shown in Fig. 2, it is attached to a coaxial transmission line 712 having an external conductor 71 ^ and an internal conductor 716 stored to a supply point 213. Although the helical coil of Fig. 2 shows any helical coil of Figs. 3-7 could be coupled to the coaxial transmission line, according to the present invention. The advantage of the coaxial transmission line feeding the variable pitch antenna is that the length of the coaxial feed line can be used to change the current distribution in the PC board, so that optimum radiation efficiency can be obtained, particularly when use the phone The reason for the optimization is that the coaxial transmission line changes the input impedance "of the variable pitch, so that also the current distribution in the PC board, because the current in the PC board has important radiation. for the distant field, then varying the distribution of "current can lead to an optimal state of the radiation efficiency of the antenna. When the telephone is used, the current in the antenna and in the PC board changes significantly due to the proximity of the user's body. With the power supply of the transmission line, the changed current can be compensated. Considering now Figs. 8-10, the perspective view shows a helical coil antenna 801 according to the present invention, coupled to a monopole 802 having a threaded portion 804 and a contact portion 806, although the helical coil of FIG. 2 shows any helical coil of Figs. 3-7 could be coupled to the monopole A cross-sectional view in Fig. 9 shows the cross-section or cross-section of an embodiment of the antenna of Fig. 10. In particular a dielectric core 904 inside the envelope. mold 902 ~ comprises "preferably a dielectric material., the core could be a dielectric material comprising santaprene and polypropylene. For example, the dielectric core could be composed of 75% santaprene and 25% polypropylene to create a dielectric material with a dielectric constant of 2.0. A plan view in Fig. 10 shows the antenna 129 separated from the wireless communication device. As will be described in Fig. 11 any antenna described in this application could be coupled to a whip -whip portion, which is to be incorporated into a retractable antenna. Considering now Fig. 11, there is shown in partial cross section, an antenna according to the present invention coupled to a wireless communication device, such as that shown in Fig. 1. The antenna 129 comprises an outer box or overmold 902 having a sleeve 1004. Monopole 802 comprises a threaded portion 804 which extends to a gathering portion 806. The monopole length in general affects vertical polarization, where a longer monopole generally provides greater vertical polarization. . The monopole will be described in greater detail with reference to Figs. remaining. The antenna is coupled with a pin 1110 having a contact element 1112 at the end of a flexible arm 1114 that is attached to the base portion 1116. This base portion 1116 is preferably attached to a circuit board having a circuitry of the Fig. 1 or another suitable circuit. The bracket 1110 includes a second contact 1118 arrayed to the flexible arm 1120 which also extends to the base portion 1116. The gathering portion 1108 is retained by the flexible arms 1114 and 1120 which also provide electrical contact. The dimensions of the flexible arms are preferably selected to bring the efficiency of the antenna to an optimum state. That is, the length and width of the flexible arms are selected to provide adequate inductance or capacitance for the antenna, where a narrower arm provides greater inductance and a larger arm provides greater capacitance. Fig. 11 also shows a box 1130 of a wireless communication device of Fig. 11. The box includes a receiver sleeve 1132 shown in the cross section with a threaded slot 234 for receiving the threaded portion 1106 of the antenna. Although the feeding point of the antenna is preferably made in the contact elements 1112 and 118 near the base of the coupling portion 1105, the feeding point could be made in the threaded slot 1134 according to the present invention. Although the present description concentrates on a stubby antenna, any antenna presented in this application may be incorporated into a retractable antenna such as a retractable antenna presented in the application No. 0"9 / 219,561 for" adapted antenna "" to operate in a plurality of band frequency filed on December 23, 1998 and assigned to the owner of the present invention. Attenuated, coupling circuit arrangements according to application No. 09 / 219,561 application that was incorporated by reference, could also be used. In summary, a multi-band antenna can be achieved in accordance with the present invention by modifying the inclination angle of a helical coil in a suitable manner. In particular, using a non-uniform inclination angle and keeping the total length of the wire constant. The second resonance can be moved up or down as a "function of the angle of inclination as long as the first resonance is not affected." Although the invention has been described and illustrated in the foregoing description and in the drawings, it is understood that this description example only "and that numerous changes and modifications can be made by the technical without leaving the scope and spirit of the invention. Although the present invention finds particular application in portable radiotelephones, the invention can be applied to any wireless communication device, including radiolocalists, electronic organizers or computers. The applicant's invention should be limited only by the claims.

Claims (3)

1. NOVELTY OF THE INVENTION Having described the invention as above, it is claimed as property and content in the following: CLAIMS l. - An antenna adapted to operate on at least two frequencies, characterized in that a helical coil extends from a proximal end to a distal end, the helical coil has a step or inclination varying from the far end to the proximal end.
2. 2. The antenna according to claim 1, wherein the diameter of the helical coil varies from the proximal end to the distal end.
3. 3. The antenna according to claim 1, characterized in that a first helical portion extends from a first distal end to a first proximal end, the first helical portion has a first step, and a second helical portion extends from a second proximal end accommodated at the first distal end of the first helical portion, at a second distal end, the second helical portion has a second passage which is different from the first pass, or inclination. . - The antenna according to claim 3, characterized in that the first step is greater than the second step. 5. - The antenna according to claim 3, characterized in that the first step is basically fixed. 6. - The antenna according to claim 3, characterized in that the first step varies. 7. The antenna according to claim 3. characterized because the second step varies. 8. The antenna according to claim, characterized in that the first step or inclination is basically fixed and the second step varies. 9. - The antenna according to claim 3, characterized in that the first helical portion has a first diameter and the second helical portion has a second diameter that is smaller than the first diameter, 10. - The antenna according to claim 3, characterized in that it has a monopole, wherein a first end of the helical portion is coupled to the monopole.