WO2005069434A1

WO2005069434A1 - Retractable antenna and wireless application systems incorporating same

Info

Publication number: WO2005069434A1
Application number: PCT/IB2005/000008
Authority: WO
Inventors: Wing Yan Leung
Original assignee: Pets & Supplies Hong Kong Limited; Davies, Paul, R.
Priority date: 2004-01-06
Filing date: 2005-01-06
Publication date: 2005-07-28

Abstract

An antenna comprising a driven member for conversion of radio-frequency signals between wired electrical signals and wireless electromagnetic signals and at least one non-driven member for conditioning the radiation pattern of said antenna, both said driven member and non-driven member comprise an elongated and retractable conductive member connected in series with a printed circuit pattern of conductive elements, the elongated conductive members of said driven and non-driven members being substantially parallel and retractable towards their respectively connected printed circuit patterns of conductive elements.

Description

RETRACTABLE ANTENNA AND WIRELESS APPLICATION SYSTEMS INCORPORATING SAME

FIELD OF THE INVENTION

This invention relates to antennae for radio-frequency ("RF") applications and, more particularly, to portable or mobile antennae for RF-applications. More specifically, although of course not solely limited thereto, this invention relates to mobile or portable antennae of the Yagi type and wireless application systems comprising such antennae.

BACKGROUND OF THE INVENTION An antenna is an important component in a wireless application system which provides the necessary interfacing in the conversion between wired electrical signals and wireless electromagnetic waves. It is well known that the characteristic dimensions of an antenna are typically dependent on the characteristic operating frequencies of the wireless application systems. As the wavelength of an RF signal increases with a decrease in frequency, the characteristic dimensions of an antennae will become more significant at the lower end of the radio-frequency spectrum, for example, the HF(3-30 MHz), VHF(30-300 MHz) and UHF(300-3000 MHz) bands.

For example, when the characteristic operating radio frequency is at 150 MHz, the wavelength (λ) is 2m. For an antenna utilizing a half-wavelength (λ!2) dipole, the characteristic physical dimension is dependent on the length of the dipole which is in the region of 1m. It will be appreciated that an antenna of such a significant characteristic physical dimension would not be very convenient or desirable for mobile or portable applications, such as, for example, on-field tracking of animals during a hunting game or the tracking of mobile objects.

Among the many types of antennae, the Yagi antenna is widely used in high- or radio- frequency applications, especially in the radio-frequency spectrum mentioned above. The Yagi antenna generally consists of three types of elements, namely, Reflector, Radiator, and Director, although it may comprise only a Radiator and a Reflector.

The Radiator is an active or driven element which is driven by a source of radio-frequency signals or which sinks electromagnetic energy in the vicinity of the antenna of the appropriate frequency. In other words, the Radiator is directly responsible for receiving or transmitting the relevant radio-frequency signals. The Reflector and Director are non-driven or parasitic elements which, when in combination with the driven element, control the direction and the beam-width of the radiation pattern of the antenna. Typically, the Reflector and the Director are respectively inductive and capacitive parasitic elements.

A basic Yagi antenna includes a Radiator, a Reflector on one side of the Radiator and one or more Directors on the other side of the Radiator. The Radiator is usually a half-wavelength dipole. However, it will be appreciated by persons skilled in the art that, depending on the application, the Yagi antenna may include only a single Radiator with only one Reflector at the minimum. Depending on the specific applications, Directors may be added to suit the particular applications. In general, the half-wave dipole driven element of the Radiator determines the key physical or operation dimensions of a Yagi antenna and such dimensions may not be convenient for many applications, especially for operation in the lower end of the radio-frequency spectrum as mentioned above. For example, in the MURS band (FCC part 95) which is allocated for many general practical applications, there are 5 channels as tabulated below with the following characteristic center operating frequencies near 150MHz.

Exemplary MURS Channels

In this frequency band, the Yagi (or Yagi-Uda) antenna is recognized as the most suitable directional antenna for used on the receiver side. On the other hand, the Yagi antenna typically comprises a half-wavelength dipole element having an operational physical length of about 1m, an antenna of such a dimension is less than ideal for portable or mobile applications.

Hence, it would be highly desirable if there can be provided portable or mobile antennae and/or application systems with a compact size for operation in the above mentioned radio-frequency spectrum with enhanced portability or mobility.

OBJECT OF THE INVENTION Accordingly, it is an object of the present invention to provide an antenna for operation in the radio-frequency spectrum with enhanced mobility or portability. Specifically, although not solely limited thereto, it is also an object of this invention to provide a compact Yagi antenna suitable for operation in the MURS Band. At a minimum, it is an object of this invention to provide the public with a useful choice of antenna designs or systems incorporating such antenna designs. SUMMARY OF THE INVENTION

Broadly speaking, the present invention has described an antenna comprising a driven member for conversion of radio-frequency signals between wired electrical signals and wireless electromagnetic signals and at least one non- driven member for conditioning the radiation pattern of said antenna, both said driven member and said non-driven member comprise an elongated and retractable conductive member connected in series with a printed circuit pattern of conductive elements, the elongated conductive members of said driven and non- driven members being substantially parallel and retractable towards their respectively connected printed circuit patterns of conductive elements. The use of a printed circuit pattern in series with a retractable antenna member substantially mitigates the requirements of an antenna with a large physical dimension while maintaining an adequate electrical length.

According to a preferred embodiment of the present invention, there is provided an antenna which comprises at least a driven member for conversion of radio-frequency signals between wired electrical signals and wireless electromagnetic signals. The driven member comprises a series connection of a rod-type dipole portion and a printed circuit dipole portion. The rod-type dipole portion comprises first and second elongated and retractable rod-type dipole elements and the printed circuit dipole portion is connected in series with and is intermediate both the first and the second rod-type dipole elements. The printed circuit dipole portion comprises a printed circuit pattern of conductive elements. The retractable rod-type dipole elements being substantially parallel and non collinear with each other, the rod-type dipole elements being retractable towards the printed circuit dipole portion. By disposing the pair of first and second rod-type dipole elements parallelly but non-collinearly, the fully retracted first and second dipole elements can be stored in a a juxtaposed manner with enhanced spatial efficiency. In a preferred embodiment, the antenna being adapted for operation at a characteristic center operation frequency, the driven member being adapted for transmitting radio-frequency electromagnetic signals away from the antenna and/or for receiving radio-frequency electromagnetic signals, wherein the at least one non-driven member including a Reflector for conditioning the characteristic beam direction or front-to-back ratio of the radiation pattern of the antenna, the fully extended length of the driven member being significantly less than half of the wavelength of the characteristic center operation frequency.

Preferably, the separation between the substantially parallel elongated conductive members of the driven member and the Reflector being significantly less than 15% of the wavelength of the characteristic center operation frequency.

Preferably, the elongated conductive member including a telescopically extendable rod-type dipole element which is movable relative to the printed circuit pattern of conductive elements when in the fully retracted state. Preferably, the elongated conductive members of both driven and non- driven members including first and second retractable elongated conductive members which are retractable towards their respectively connected printed circuit patterns of conductive elements, the printed circuit patterns of conductive elements being connected in series with and intermediate the first and second elongated conductive members.

Preferably, the distance between the ends of the fully extended first and second elongated conductive members of the driven member being significantly less than half of the wavelength of the characteristic center operation frequency. Preferably, the printed circuit pattern of conductive elements comprises a meandering pattern including a plurality of substantially parallel elongated printed conductive elements connected in series.

Preferably, the elongated printed conductive elements being substantially orthogonal to the first and second elongated conductive members connected to the printed circuit pattern of conductive elements.

Preferably, the printed circuit pattern of the conductive elements of the Radiator PCB1 comprise first and second printed portions interconnected by an intermediate printed transformer.

Preferably, the spacing between adjacent elongated printed conductive elements being about 0.15 cm, the width and length of the elongated printed conductive elements being respectively about 0.05 cm and 2 cm.

Preferably, the first and second elongated conductive members of the driven or non-driven member which are connected to a printed circuit pattern of conductive elements being substantially overlapping in their fully retracted state and being substantially non-overlapping at their fully extended state.

Preferably, the first and second elongated conductive members being substantially overlapping and substantially non-overlapping with the printed circuit pattern of the printed circuit pattern of conductive elements respectively in the fully retracted and extended states of the first and second elongated conductive members.

Preferably, the first and second retractable elongated conductive members connected to the same printed circuit pattern of conductive elements being substantially parallel but non-collinear.

Preferably, the antenna further including a main housing in which the printed circuit patterns of conductive elements are housed, the first and second elongated conductive members of the driven and non-driven members being substantially contained within the housing in their fully retracted state. Hence, according to this invention, the fully expanded physical width of the antenna, as substantially characterised by the fully extended length of the two dipole conductive members plus the width of PCB1 , is significantly less than λll, the characteristic dimensions required by conventional Yagi antenna. This reduced fully extended characteristic width of the antenna can be further reduced by utilizing the retractable configurations mentioned herein to further enhance portability during transportation and to restore to their fully extended states during normal operation.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will be explained in further detail below by way of examples and with reference to the accompanying drawings, in which:-

Fig. 1 is a schematic layout of a typical Yagi antenna with a Reflector, a Radiator and a plurality of directors with the more relevant characteristic dimensions label on the Figure,

Fig. 2 is a schematic physical layout showing the typical dimensions of a standard 150 MHz Yagi antenna of Fig. 2 comprising a Radiator, a Reflector and a Director with the more relevant dimensions label, Fig. 3 is a schematic physical layout of a preferred embodiment of an antenna of this invention comprising a Radiator and a Reflector,

Fig. 4 shows the side elevation fields of the antenna of Fig. 3,

Figs. 5A and 5B respectively show exemplary printed pattern of conductive elements of PCB1 and PCB2 of Figs. 3 and 4, Figs. 6A, 6B and 6C illustrate the antenna of Fig. 3 respectively in its fully expanded, intermediately expanded and fully retracted state,

Figs. 7A and 7B show in more detail the printed conductive pattern of PCB1 of Fig. 5A in more detail,

Figs. 8A and 8B show in more detail the printed conductive pattern of PCB2 of Fig. 5B in more detail, Figs. 9A and 9B respectively show the simulated radiation pattern in the H- and E-planes of the antenna of Fig. 3,

Fig. 10 illustrates a partially exploded perspective view of the preferred embodiment of an antenna of this invention with the PCBs displaced to show the rod-type dipole elements in the fully retracted and stored state,

Fig. 11 is the antenna of Fig. 10 with the dipole element in the fully extended state, and

Fig. 12 is the antenna of Fig. 11 in a state intermediate that of Fig. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The Yagi antenna is widely used in RF applications and, more particularly, in the HF (3-30 MHz), VHF (30-300 MHz) and UHF (300-3000 MHz) bands, which cover home TV broadcasting and MURS applications. As mentioned above, the Yagi antenna typically comprises a number of linear dipole elements which can be divided into 3 main types, namely Radiator, Reflector and Director. The Radiator can be the source or sink of signals. In the former case, the Radiator is energized for example directly by a feed transmission line. In the latter case, the Radiator is used as a sink of electromagnetic waves. The Director and the Reflector are parasitic elements with signals induced by mutual couplings. Typically, the Director is put in the forward beam location and is used for controlling the beam- width, which is a parameter indicating how narrow the main lobe of the radiation pattern is. The Reflector is usually located behind the Radiator and the Directors and is for controlling the Front-to-Back Ratio, which is a ratio of the gain in the forward beam direction to that in the opposite direction. To obtain a radiation pattern of a prescribed degree of directivity, for example, a radiation pattern resembling the well-known "endfire" beam pattern, there are certain known rules to be followed. For example, the length of the Radiator is slightly less than 0.5/1 and the length of the Directors is less than that of the Radiator (usually (but not essentially) between 0.45-0.49 1). For a good front-to-back ratio, the length of the Reflector is slightly longer than that of the Radiator. Generally speaking, a higher directivity can be obtained by having a Yagi antenna with one Reflector and a plurality of Directors. The theoretical dimensional requirements of a typical Yagi antenna, with segment separation details, for operation at 150 MHz are illustrated in Fig. 1 as a convenient example. It should be appreciated that the Radiator and the Directors may be of different diameters.

Hence, it will be appreciated that an antenna of this standard conventional design is probably too bulky or inconvenient for mobile or portable operation in the MURS Band or other RF bands. In the description below, the general design parameters of a convention Yagi antenna for a MURS band will be described, to be followed by the description of a preferred embodiment of an improved Yagi antenna design of this invention with enhanced compactness and portability.

Firstly, for a Yagi antenna operating at a characteristic center or operating frequency of 150 MHz, the characteristic dimensions can be related to the wavelength (A)as follows:

λ = — where, / ^{c :} Speed of Light (c = 3x10^s ms^~λ ) f : Operation Frequency (150 MHz in this case) λ : Wavelength

Hence, for 150 MHz operation,

λ = 7- = 2m 150 l0⁶

Length of Radiator: 0.5/1 = \m = 100cm Length of Director: 0.475A = 0.95m = 95cm Length of Reflector: 0.525/1 = 1.05m = 105cm Separation between Radiator and Director = 0.15/1 = 0.3m = 30cm

Separation between Radiator and Reflector = 0.25 1 = 0.5m = 50cm

Based on the above calculations, the dimensions of an exemplary standard 150MHz Yagi antenna is shown in Fig. 2.

Referring to Figs. 3-10, there is shown a preferred embodiment of the antenna of the present invention in the form of a Yagi antenna 100 comprising only a Radiator 200 and a Reflector 300 for simplicity for the benefit of succinctness in description. Both the Radiator and the Reflector comprise a serial connection of rod-type and printed circuit type dipole portions.

Referring firstly to the Radiator, the rod-type dipole portion of the Radiator comprises first and second elongated conductive members (221, 222) each of which is similar to the rod-type dipole elements of conventional dipole elements. The printed circuit dipole portion comprises a printed circuit board ("PCB") with a printed circuit pattern of conductive elements which are arranged in continuous meandering lines as a convenient example. Specifically, the printed circuit pattern of conductive elements on the PCB of the Radiator, namely, PCB1 210, comprises a plurality of parallel elongated conductive line elements connected in series at their respective ends as shown in Figs. 5A. For an exemplary application at 150 MHz, the exemplary spacing between adjacent elongated printed conductive elements being about 0.15 cm, the exemplary width and length of the elongated printed conductive elements being respectively about 0.05 cm and 2 cm. In order to generate a single output from a differential input from the active dipole elements, a transformer is formed in PCB1 of the Radiator intermediate first and second printed circuit patterns of meandering lines more particularly shown in Figs. 5A, 7A and 7B.

Each of the first and second elongated conductive members comprises a rod-type dipole element (221, 222) similar to that found in conventional Yagi antennae. There fore, the complete dipole element is formed by a series connection of the first elongated conductive member, the printed circuit dipole portion and the second elongated conductive member, with the printed circuit dipole portion intermediate the first and second elongated conductive members. This series connection is adapted to constitute an equivalent circuit of an appropriate equivalent electrical length required for the necessary dipole performance and the specific design can be optimized by computer simulation tools such as, for example, Ansoft HFSS®. Specifically, In this example, an overall equivalent electrical length of λll is required for the total series connection of the rod-type and printed circuit dipole portions. As a convenient example, each of the elongated conductive members of the Radiator has a length of 25 cm (λ/8) during normal operation and the total physical length of the first and second conductive members (221, 222) during normal operation is about 50 cm ( λ 14). The meandering lines printed on the PCB1 account for the remaining equivalent electrical length of A/4 on a PCB of a width 6 cm. The actual layout can be obtained and optimized by appropriate computer simulation. To further enhance compactness in antenna size during transportation, the first and second elongated conductive members of the rod-type portion are rod- type dipole elements which are retractable towards or extendable from the printed circuit dipole portion. An example of suitable retractable elongated conductive members for use in the rod-type dipole portion is the conventional telescopically extendable dipole antenna commonly found in portable FM-radio applications. In this example, the rod-type dipole portion is retractable and extendable between 6cm and 25cm.

Hence, it will be appreciated that, by utilizing a series combination of the rod-type and printed-circuit dipole portions, the total fully extended physical length of the Radiator can be significantly reduced, for example, to only 56 cm in the above example, as compared to the 100 cm length required in a conventional design. Further, by utilizing a further space saving design in addition to having the first and the second conductive members of the rod-type dipole portion in retractable form, the size of the fully retracted antenna can be further reduced. As can be seen from the description below, this size reduction technique will enable the totality of printed circuit dipole portion and the first and second conductive members each having a fully extended length of 25 cm to be totally housed within a main housing of a very compact size, for example, of about 6cm wide in this example.

The Yagi antenna of this preferred embodiment includes a Reflector to improve the front-to-back ratio. Similar to the Radiator, the Reflector also comprises a series connection of rod-type and printed-circuit type dipole portions. Thus, the complete dipole element is also formed by a series connection of the first elongated conductive member, the printed circuit dipole portion and the second elongated conductive member, with the printed circuit dipole portion intermediate the first and second elongated conductive members. This series connection is adapted to constitute an equivalent circuit of an appropriate equivalent electrical length required for the necessary dipole performance and the specific design can also be optimized by computer simulation tools.

As described above and also shown in Fig. 2, the total electrical length of this Reflector should be slightly more than λ 12 for better directivities and a Reflector of a conventional design will have an exemplary length of 105cm. On the other hand, the Reflector of this invention provides a substantially equivalent performance to the conventional design by having a series connection of the rod-type 321, 322 and printed circuit-type 310 dipole elements similar to that of the Radiator design described above. Similar to the Radiator design, the rod-type dipole portion 321, 322 comprises first and second elongated (or rod- type) conductive members but each having a length of 28 cm when fully extended. The remaining or outstanding electrical length of the Reflector is then made up for by a printed circuit dipole portion. Similar to the printed circuit dipole portion of the Radiator, the printed circuit dipole portion comprises a printed circuit board (PCB2 310) of 6cm wide with two printed circuit patterns of conductive elements which are arranged in continuous meandering lines. Likewise, the printed circuit pattern of conductive elements on PCB2 310 comprises a plurality of parallel elongated conductive line elements connected in series at their respective. Unlike the Radiator, however, there is no transformer connected the two portions of the meandering lines. Thus, in this preferred embodiment and, as a convenient example, each of the elongated conductive members has a length of 28 cm during normal operation and the total physical length of the first and second conductors during normal operation is about 56 cm. The meandering lines printed on the PCB1 account for the remaining equivalent electrical length of λl4 on a PCB of a width 6 cm. As a result, the total fully extended physical length of this Reflector is only about 62 cm, compared to the 105 cm required in the conventional design.

The rod-type dipole portion of the Reflector also comprises first and second retractable elongated conductive members (or rod-type elements 321, 322) which can be retracted into a main housing and PCB2 is intermediate the retractable first and second rod-type members. Hence, similar to that of the Radiator, the retractable first and second rod-type elements can retract towards, and extend from, PCB2. Consequently, the total characteristic width of the Reflector is also substantially less than the typical characteristic width of a Reflector of a conventional Yagi antenna design for the same application.

Furthermore, simulation and experiments show that the use of this i approach, namely, dipole elements comprising a series connection of the rod-type and printed-circuit type dipole portions, also reduces the spacing between the Radiator and Reflector. In this example, the spacing between the parallel rod-type elements respectively of the Radiator and the Reflector has been significantly reduced from 50 cm to only 14 cm.

In this example, the Director has not be specifically described with reference to the antenna design since the front-to-back ratio is a more important aspect for this exemplary application, namely, an animal tracking system, in which a very narrow beam-width is not a prerequisite. Of course, if an antenna of a narrow beam-width is needed, an appropriate Director or Directors can be added without loss of generality. Furthermore, while the design of the Directors have not been specifically described, it will be appreciated that the design topology and methodology described above will apply mutatis mutandis to the design of an Yagi antenna with a Director without loss of generality.

Referring now in more detail to the design of the exemplary antenna design of Fig. 3 with reference to Figs. 4 to 10.

The two PCBs of Fig. 3, namely, PCB1 and PCB2, are both FR4 with a relative dielectric constant (ε) of 4.4 and a thickness of 1.6 mm. Specifically, PCB1 and PCB2 are respectively of dimensions (length x width) 4 x 6 cm and 2.5 x 6 cm.

Two rod-type dipole elements are connected to the respective ends of the meandering lines by coaxial cables, as shown in Fig. 4. Hence, there are a total of four rod-type dipole elements connected to the two PCBs.

While two retractable conductive members are used as examples above, it would be appreciated that the use of multiple retractable conductive members connected in series with each other, with the PCB connected intermediate both first and second conductive members are for further miniaturization since there is a physical limit to the minimum length of a retractable conductive member of the telescopic type for use as telescopic dipole elements.

Referring to Figs. 4, 6A-6C, a further aspect of the invention which further enhances the compactness or miniaturization of an antenna is shown. In this arrangement, the first and second elongated conductive members (or rod-type dipole elements) are disposed in a substantially parallel but non-collinear manner and off the plane of the PCBs. As is more particularly shown in Figs. 3 & 4, the rod-type dipole elements are disposed off the plane of the PCB and connected to the PCBs with appropriate connection means. In other words, the axes of the rod- type dipole elements are non-collinear with each other and non-coplanar with the plane of the PCBs.

By disposing the rod-type dipole elements off-plane of the PCB, the retractable rod-type dipole elements can be telescopically retracted towards the connecting (near) edge of the PCB and move further beyond towards the distal PCB edge. As a result, and as shown in Figs. 6A-6C, the rod-type dipole elements can be fully (or at least substantially) retracted into the main housing and a non-insignificant portion of them can be stored under the foot-print of the PCBs, thereby further reducing the minimum dimension of the main housing 400 and the antenna. As can be seen in the Figs. 6 and 10, the dipole elements are substantially parallel and overlapping with each other when in the fully retracted and stored state. Also, the retracted dipole elements, while off the plane of their respectively connected PCBs, are substantially overlapping with the projection of PCB. To enable this further compactness, a flexible or non-rigid connection is made between the rod-type dipole elements and the PCB so that after the rod- type dipole element has entered into the fully retracted state, the fully retracted rod-type dipole element can move relative to the PCB, pass the near edge and further towards the distal edge for maximal storage space utilization. Specifically, the base 323 (and in fact the last portion) of the rod-type dipole element is slidably moveable along a tubular compartment 324 in which the rod-type element is substantially housed when in the fully retracted and stored state as shown in Figure 10. When in the fully retracted and stored state, the base member is moved to the distal side 325 of the tubular compartment. When in the fully extended state of Figure 11, the base 323 is moved to the near edge of the tubular compartment 326 and makes contact with the printed circuit portion 310 via a tubular conductive contact member interfacing the printed circuit portion 310 and the rod-type element 321. While the present invention has been explained by reference to the examples or preferred embodiments described above, it will be appreciated that those are examples to assist understanding of the present invention and are not meant to be restrictive. The scope of this invention should be determined and/or inferred from the preferred embodiments described above and with reference to the Figures where appropriate or when the context requires. In particular, variations or modifications which are obvious or trivial to persons skilled in the art, as well as improvements made thereon, should be considered as falling within the scope and boundary of the present invention.

Furthermore, while the present invention has been explained by reference to Yagi antenna, it should be appreciated that the invention can apply, whether with or without modification, to other antennae, for example, for antennae using conventional rod-type dipole elements, without loss of generality.

Claims

1. An antenna comprising a driven member for conversion of radio-frequency signals between wired electrical signals and wireless electromagnetic signals and at least one non-driven member for conditioning the radiation pattern of said antenna, both said driven member and non-driven member comprise an elongated and retractable conductive member connected in series with a printed circuit pattern of conductive elements, the elongated conductive members of said driven and non-driven members being substantially parallel and retractable towards their respectively connected printed circuit patterns of conductive elements.

2. An antenna according to claim 1, wherein said antenna being adapted for operation at a characteristic center operation frequency, said driven member being adapted for transmitting radio-frequency electromagnetic signals away from said antenna and/or for receiving radio-frequency electromagnetic signals, wherein said at least one non-driven member including a Reflector for conditioning the characteristic beam direction or front-to-back ratio of the radiation pattern of the antenna, the fully extended length of said driven member being significantly less than half of the wavelength of the said characteristic center operation frequency.

3. An antenna according to claim 2, wherein the separation between the substantially parallel elongated conductive members of said driven member and said Reflector being significantly less than 15% of the wavelength of said characteristic center operation frequency.

4. An antenna according to claim 3, wherein said elongated conductive member including a telescopically extendable rod-type dipole element which is movable relative to said printed circuit pattern of conductive elements when in the fully retracted state..

5. An antenna according to claim 2, wherein the elongated conductive members of both said driven and non-driven members including first and second retractable elongated conductive members which are retractable towards their respectively connected printed circuit patterns of conductive elements, said printed circuit patterns of conductive elements being connected in series with and intermediate said first and second elongated conductive members.

6. An antenna according to claim 5, wherein the distance between the ends of the fully extended first and second elongated conductive members of said driven member being significantly less than half of the wavelength of said characteristic center operation frequency.

7. An antenna according to claim 6, wherein the separation between the substantially parallel elongated conductive members of said driven member and said Reflector being significantly less than 15% of the wavelength of said characteristic center operation frequency.

8. An antenna according to claim 7, wherein said elongated conductive member including a telescopically extendable rod-type dipole element which is movable relative to said printed circuit pattern of conductive elements when in the fully retracted state.

9. An antenna according to claim 5, wherein said printed circuit pattern of conductive elements comprises a meandering pattern including a plurality of substantially parallel elongated printed conductive elements connected in series.

10. An antenna according to claim 9, wherein the elongated printed conductive elements being substantially orthogonal to said first and said second elongated conductive members connected to the printed circuit pattern of conductive elements.

11. An antenna according to clam 10, wherein said printed circuit pattern of the conductive elements of the Radiator PCB1 comprise first and second printed portions interconnected by an intermediate printed transformer.

12. An antenna according to claim 10, wherein the spacing between adjacent elongated printed conductive elements being about 0.15 cm, the width and length of said elongated printed conductive elements being respectively about 0.05 cm and 2 cm.

13. An antenna according to claim 5, wherein said first and second elongated conductive members of said driven or non-driven member which are connected to a printed circuit pattern of conductive elements being substantially overlapping in their fully retracted state and being substantially non-overlapping at their fully extended state.

14. An antenna according to claim 13, wherein said first and said second elongated conductive members being substantially overlapping and substantially non-overlapping with the printed circuit pattern of said printed circuit pattern of conductive elements respectively in the fully retracted and extended states of said first and second elongated conductive members.

15. An antenna according to claim 5, wherein said first and second retractable elongated conductive members connected to the same printed circuit pattern of conductive elements being substantially parallel but non-collinear.

16. An antenna according to claim 15, further including a main housing in which said printed circuit patterns of conductive elements are housed, said first and second elongated conductive members of said driven and non-driven members being substantially contained within said housing in their fully retracted state.

17. An antenna comprising at least a driven member for conversion of radio- frequency signals between wired electrical signals and wireless electromagnetic signals, said driven member comprising a series connection of a rod-type dipole portion and a printed circuit dipole portion, said rod-type dipole portion comprises first and second elongated and retractable rod-type dipole elements and said printed circuit dipole portion being connected in series with and being intermediate both said first and second rod-type dipole elements, said printed circuit dipole portion comprises a printed circuit pattern of conductive elements, said retractable rod-type dipole elements being substantially parallel and non collinear with each other, said rod-type dipole elements being retractable towards said printed circuit dipole portion.

18. An antenna according to Claim 17, further comprising at least a non-driven member, said non-driven member comprising a series connection of a rod- type dipole portion and a printed circuit dipole portion, said rod-type dipole portion comprises first and second elongated and retractable rod-type dipole elements and said printed circuit dipole portion being connected in series with and being intermediate both said first and second rod-type dipole elements, said printed circuit dipole portion comprises a printed circuit pattern of conductive elements, said retractable rod-type dipole elements being substantially parallel and non collinear with each other, said rod-type dipole elements being retractable towards said printed circuit dipole portion.

19. An antenna according to Claim 18, wherein said driven and non-driven members being respectively a Radiator and a Reflector, the elongated rod- type dipole elements of said Reflector and said Radiator being substantially parallel but non-collinear.