TWI519000B - Communication device and its multi - frequency antenna - Google Patents

Description

Communication device and multi-frequency antenna thereof

The present invention relates to a device and an antenna thereof, and more particularly to a communication device and a multi-frequency antenna thereof.

Referring to Fig. 1, a multi-frequency antenna disclosed in U.S. Patent No. US20040246188, comprising a ground plane 11, a feed-in radiating element 12 and a grounding parasitic arm 13.

The ground plane 11 is used to provide a reference ground potential.

The feed-in radiating unit 12 includes a grounding arm 121 protruding from the grounding surface 11 , two radiating arms 122 extending from the grounding arm 121 to a first direction X, and an electrical connection of the radiating arms 122. Feeding unit 123.

The grounding parasitic arm 13 protrudes from the ground plane 1 in a second direction Y perpendicular to the first direction X, and then extends a distance to the -Y direction, and the grounded parasitic arm 13 is interposed between the feeding radiation unit 12 and between the ground planes 11.

The disadvantages of this multi-frequency antenna are:

1. The grounded parasitic arm 13 must be physically connected to the ground plane 11 and thus has a low degree of design freedom.

2. The grounding parasitic arm 13 protrudes from the ground plane 1 and The effect is similar to the extension of the ground plane 11 , so that an equivalent height of the radiating arms 122 to the ground plane 11 becomes smaller, and the closer the ground parasitic arm 13 is to the radiating arms 122, the radiating arms 122 are received. The interference will be larger, so that the bandwidth of the resonance of the radiating arms 122 becomes smaller; however, if the grounded parasitic arm 13 is not brought close to the radiating arm 122 at a limited antenna height, the grounding is caused. The height of the parasitic arm 13 (distance from the ground plane 11) is not large enough to resonate with a large bandwidth.

Therefore, it is an object of the present invention to provide a multi-frequency antenna with high degree of freedom in design.

Thus, the multi-frequency antenna of the present invention comprises a ground plane, a feed radiation unit and a floating parasitic arm.

The ground plane includes an edge.

The feed radiation unit is spaced apart from the ground plane and adjacent to the edge, and includes: a feed arm and a radiation arm.

The feed arm has a free end adjacent the edge and a top portion of the edge remote from the ground plane and is provided with a feed point adjacent the edge of the ground plane.

The radiating arm is electrically connected to the top of the feeding arm and has a first free end and a first radiating arm section.

The first radiating arm segment extends from the first free end of the radiating arm And between the top of the feed arm, and a first resonant path from the free end of the feed arm to the first free end of the radiating arm is substantially L-shaped and is used to generate a first frequency band Resonance.

The floating parasitic arm is physically isolated from the ground plane and the feed radiation unit, and includes a first free end and a second free end opposite to each other, and a long arm section adjacent to the first free end of the floating parasitic arm And the long arm segment, the first radiating arm segment and the edge of the ground plane overlap at a distance in a first direction, the long arm segment and the radiating arm jointly define a first coupling gap.

Thereby, the floating parasitic arm and the feeding radiation unit transmit electromagnetic energy in a coupled manner, and a second resonant path between the first free end and the second free end of the floating parasitic arm is used to generate coverage A resonance of a second frequency band.

Another object of the present invention is to provide a communication device.

The communication device comprises the multi-frequency antenna, a circuit module and a coaxial cable as described above.

The circuit module includes an RF signal transmission end for transmitting and receiving an RF signal and a reference ground.

The coaxial cable is electrically connected between the multi-frequency antenna and the circuit module for exchanging the RF signal and has an inner conductor and an outer conductor. The inner conductor is electrically connected to the feeding point of the multi-frequency antenna and the radio frequency signal transmitting end of the circuit module, and the outer conductor is electrically connected to the grounding surface of the multi-frequency antenna and the reference ground of the circuit module

The invention has the effect that the floating parasitic arm of the multi-frequency antenna is not physically connected to the ground plane or the feed radiation unit, and thus has design freedom.

11‧‧‧ Ground plane

12‧‧‧Feed radiation unit

121‧‧‧ Grounding arm

122‧‧‧radiation arm

123‧‧‧Feeding Department

13‧‧‧ Grounding parasitic arm

2‧‧‧ ground plane

21‧‧‧ edge

22‧‧‧Conductor patch

3‧‧‧Feed radiation unit

31‧‧‧Feeding arm

311‧‧‧Free end

312‧‧‧ top

32‧‧‧radiation arm

321‧‧‧The first free end

322‧‧‧First Radiation Arm Section

323‧‧‧Second free end

324‧‧‧second radiant arm section

33‧‧‧Feeding point

4‧‧‧suspension parasitic arm

41‧‧‧First free end

42‧‧‧Second free end

43‧‧‧Long arm section

431‧‧‧Connected end

44‧‧‧Bent arm section

5‧‧‧First short circuit parasitic arm

51‧‧‧ Grounding

52‧‧‧First free end

53‧‧‧Second free end

54‧‧‧First coupling upper edge

55‧‧‧Second coupling upper edge

6‧‧‧Second short-circuit parasitic unit

61‧‧‧ Grounding terminal

62‧‧‧Free end

7‧‧‧Substrate

71‧‧‧Upper surface

72‧‧‧ side

8‧‧‧welding block

10‧‧‧Multi-frequency antenna

20‧‧‧ circuit module

201‧‧‧RF signal transmission end

202‧‧‧reference ground

30‧‧‧Coaxial cable

G1‧‧‧first coupling gap

G2‧‧‧second coupling gap

G3‧‧‧3rd coupling gap

G4‧‧‧fourth coupling gap

P1‧‧‧First resonance path

P2‧‧‧ second resonance path

P3‧‧‧ third resonance path

P4‧‧‧ fourth resonance path

P5‧‧‧ fifth resonance path

P6‧‧‧ sixth resonance path

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a schematic diagram of a conventional multi-frequency antenna; FIG. 2 is a first preferred embodiment of the multi-frequency antenna of the present invention. FIG. 3 is a schematic diagram of a voltage standing wave ratio of the first preferred embodiment; FIG. 4 is a schematic diagram of a second preferred embodiment of the multi-frequency antenna of the present invention; and FIG. 5 is a multi-frequency antenna of the present invention. FIG. 6 is a schematic view showing a fourth preferred embodiment of the multi-frequency antenna of the present invention; FIG. 7 is a schematic view showing a fifth preferred embodiment of the multi-frequency antenna of the present invention; 8 is a block diagram of a preferred embodiment of the communication device of the present invention.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 2, a first preferred embodiment of the multi-frequency antenna of the present invention comprises a ground plane 2, a feed-in radiating unit 3, a floating parasitic arm 4, a first short-circuit parasitic unit 5, and a second short-circuit parasitic unit 6. And a substrate 7.

The ground plane 2 includes an edge 21.

The feed radiation unit 3 is spaced apart from the ground plane 2 and adjacent to the edge 21, and is from a first direction X between the floating parasitic arm 4 and the edge 21 of the ground plane 2, and is suspended The parasitic arm 4 and the ground plane 2 are physically isolated.

The feed radiation unit 3 includes a feed arm 31 and a radiation arm 32.

The feed arm 31 has a free end 311 and a top 312. The free end 311 is adjacent to the edge 21 of the ground plane 2, the top 312 is away from the edge 21 of the ground plane 2, and the feed arm 31 is provided with a feed point 33 adjacent to the edge 21 of the ground plane 2.

The radiating arm 32 is electrically connected to the top 312 of the feeding arm 31 and has a first free end 321 , a first radiating arm section 322 , a second free end 323 and a second radiating arm section 324 .

The first radiating arm section 322 extends substantially in a second direction Y perpendicular to the first direction X and extends between the first free end 321 of the radiating arm 32 and the top 312 of the feeding arm 31, and A first resonant path P1 from the free end 311 of the feed arm 31 to the first free end 321 of the radiating arm 32 is substantially L-shaped and is used to generate a resonance covering a first frequency band.

The second free end 323 of the radiating arm 32 is opposite the first free end 321 .

The second radiating arm segment 324 protrudes from the feeding arm 31 and extends to the second free end 323 of the radiating arm 32, and is opposite to the first radiating arm segment 322 located at the feeding arm 31 a side, and substantially an opening toward the U-shape of the feed arm 31, and a third resonant path P3 of the free end 311 of the feed arm 31 to the second free end 323 of the radiating arm 32 is used to generate coverage A resonance of a third frequency band.

The floating parasitic arm 4 is physically isolated from the ground plane 2 and the feed radiation unit 3, and includes a first free end 41 and a second free end 42. A long arm section 43 and a bent arm section 44.

The first free end 41 and the second free end 42 are opposite ends of each other, and the feed radiation unit 3 is adjacent to the first free end 41 of the floating parasitic arm 4 and away from the second free end 42 of the floating parasitic arm 4 The first radiating arm section 322 extends from the feed arm 31 away from the first free end 41 of the floating parasitic arm 4 and in the second direction Y of the second free end 42 of the floating parasitic arm 4.

The long arm section 43 is adjacent to the first free end 41 of the floating parasitic arm 4 and extends substantially from the first free end 41 in the second direction Y and has a connecting end 431. In the preferred embodiment, the first free end 41 and the second radiating arm section 324 of the feed radiation unit 3 overlap in the first direction X.

The bent arm section 44 is substantially L-shaped and extends from the connecting end 431 of the long arm section 43 to the second free end 42 of the floating parasitic arm 4.

The long arm section 43, the first radiating arm section 322 and the edge 21 of the grounding surface 2 are spaced apart in the first direction X, and the feeding radiation unit 3 is interposed between the long arm section 43 and the edge. Between 21 . The long arm section 43 and the radiating arm 32 together define a first coupling gap g1, whereby the floating parasitic arm 4 and the feeding radiation unit 3 transmit electromagnetic energy in a coupled manner, and the floating parasitic arm A second resonant path P2 between the first free end 41 and the second free end 42 of 4 is used to generate a resonance that encompasses a second frequency band.

In the preferred embodiment, the first resonant path P1 is electrically long. The degree is essentially a quarter wavelength corresponding to 2100 MHz. The second frequency band covers the frequency band from 704 MHz to 960 MHz, and the electrical length of the second resonant path P2 is substantially one quarter wavelength corresponding to 832 MHz (832=(704+960)/2). . The electrical length of the third resonant path P3 is substantially one quarter wavelength corresponding to 2595 MHz (2595 = (2500 + 2690)/2). In addition, the first radiating arm segment 322 can generate a resonance with a center frequency of 2100 MHz, and can also adjust the second frequency band (704 to 960 MHz) via the reactance value equivalent to the first gap g1 at the radio frequency. The center frequency and the impedance matching, wherein the narrower the width of the first gap g1 in the first direction X or the longer the length in the second direction Y, the lower the center frequency of the second frequency band is shifted to the lower frequency. And the input impedance corresponding to the second frequency band measured from the feed point 33 also changes with the length and width of the first gap g1.

The first short circuit parasitic unit 5 is substantially T-shaped and is located between the long arm section 43 of the floating parasitic arm 4 and the edge 21 of the ground plane 2, and is electrically connected to the ground plane 2 but with the feed radiation Unit 3 and the floating parasitic arm 4 are physically isolated.

The first short circuit parasitic unit 5 includes a grounding end 51, a first free end 52, a second free end 53, a first coupling upper edge 54 and a second coupling upper edge 55.

The ground terminal 51 is electrically connected to the ground plane 2 . In the preferred embodiment, the grounding end 51 and the grounding surface 2 are adhered by a conductor patch 22 such that the grounding end 51 is electrically connected to the grounding surface 2 through the conductor patch 22.

The first free end 52 is adjacent to the feed radiation unit 3, and the first free end 52 is located between the first radiating arm segment 322 and the edge 21 of the ground plane 2 in the first direction X, and A fourth resonant path P4 of the first short-circuit parasitic unit 5 to the first free end 52 of the first short-circuiting parasitic unit 5 is used to generate a resonance covering a fourth frequency band.

The second free end 53 is away from the feed radiation unit 3 and located between the floating parasitic arm 4 and the edge 21 of the ground plane 2, and from the ground end 51 of the first short circuit parasitic unit 5 to the first short circuit A fifth resonant path P5 of the second free end 53 of the parasitic element 5 is used to generate a resonance covering a fifth frequency band.

In the preferred embodiment, the fourth frequency band and the fifth frequency band are in close proximity to collectively cover a frequency band of 1710 MHz to 2170 MHz.

The first coupling upper edge 54 is coupled to the first free end 52 of the first short circuit parasitic unit 5 and partially overlaps the first radiating arm segment 322 in the first direction X and defines a second coupling gap g2 .

The second coupling upper edge 55 is connected to the second free end 53 of the first short circuit parasitic unit 5 and defines a third coupling gap g3 with the floating parasitic arm 4.

The second short-circuit parasitic unit 6 is electrically connected to the ground plane 2 and substantially has an L shape, and the first short-circuit parasitic unit 5 is located in the second short-circuit parasitic unit 6 and the feed in the second direction Y. Between the radiating elements 3.

The second short-circuit parasitic unit 6 is spaced apart from the floating parasitic arm 4 in the first direction X and located at the floating parasitic arm 4 and the ground plane 2 Between the edges 21 and the projection of the bending arm segment 44 in the first direction X, the second shorting parasitic unit 6 and the bending arm segment 44 define a fourth coupling gap g4 to enable the The two-band frequency down, in other words, the coupling between the second short-circuit parasitic element 6 and the floating parasitic arm 4 can cause the floating parasitic arm 4 to produce a second, 704 MHz to 960 MHz with a shorter physical length. The resonance of the frequency band.

The second short circuit parasitic unit 6 includes a ground end 61 and a free end 62.

The grounding end 61 is electrically connected to the edge 21 of the ground plane 2. In the preferred embodiment, the grounding end 61 and the grounding surface 2 are adhered by a conductor patch 22 such that the grounding end 61 is electrically connected to the grounding surface 2 through the conductor patch 22.

The free end 62 is located between the first short-circuit parasitic unit 5 and the edge 21 of the ground plane 2, and is used from the ground end 61 of the second short-circuit parasitic unit 6 to a sixth resonant path P6 of the free end 62. Generating a resonance covering a sixth frequency band from 1710 MHz to 1880 MHz, the electrical length of the sixth resonance path P1 being substantially one corresponding to 1795 MHz (1795=(1710+1880)/2) Quarter wavelength.

The substrate 7 is made of a non-conductor material, such as a glass substrate, and includes an upper surface 71 and a side surface 72.

The upper surface 71 is configured to set the bending arm segment 44, the feeding spoke The firing unit 3, the first short circuit parasitic unit 5, the second short circuit parasitic unit 6, and the plurality of solder fixing blocks 8 described below.

The side surface 72 is perpendicular to the upper surface 71, and the side surface 72 is To set the long arm section 43. The long arm section 43 is also welded to the soldering fixtures 8 for practical application of the robustness requirement.

Referring to FIG. 3, a voltage standing wave ratio (VSWR) of the first preferred embodiment shows that the floating parasitic arm 4 can be connected to the feeding radiation unit 3 The resonance of the second frequency band (704~960 MHz) is generated under the condition that the ground 2 physical contact, and the floating parasitic arm 4 does not interfere with the feeding radiation unit 3, the first short circuit parasitic unit 5 and the second Short-circuiting the parasitic unit 6, so that the first frequency band and the third to sixth frequency bands of the preferred embodiment can indeed cover the frequency band of 1710 MHz to 2690 MHz, and thus are applicable to LTE 3/4/7/13/17/20 , GSM 800/900 and IMT-2000 and other communication systems.

Referring to FIG. 4, the second preferred embodiment of the multi-frequency antenna of the present invention is similar to the first preferred embodiment. The difference is: 1. The second short-circuit parasitic unit 6 in the first preferred embodiment is not included (see 2); and 2. The bent arm section 44 of the floating parasitic arm 4 extends from the connecting end 431 of the long arm section 43 toward the edge 21 of the grounding surface 2 for a length, and then approaches the first short-circuiting parasitic unit 5 Extending a length, and finally extending a length toward the edge of the ground plane 2, and the second free end 42 is adjacent to the edge 21 of the ground plane 2 to achieve the effect of down-converting the second frequency band.

Referring to FIG. 5, a third preferred embodiment of the multi-frequency antenna of the present invention is similar to the first preferred embodiment. The difference is that the third preferred embodiment does not include the first short circuit in the first preferred embodiment. The parasitic element 5 (see Fig. 2) differs in efficacy from the first preferred embodiment in that the third preferred embodiment does not cover the frequency band from 1920 MHz to 2170 MHz.

Referring to FIG. 6, a fourth preferred embodiment of the multi-frequency antenna of the present invention is similar to the first preferred embodiment. The difference is that the fourth preferred embodiment does not include the first short circuit in the first preferred embodiment. The parasitic element 5 and the second shorting unit 6 (see Fig. 2) differ in efficiency from the first preferred embodiment in that the third preferred embodiment does not cover the frequency band 1710 MHz to 2170 MHz.

Referring to FIG. 7, a fifth preferred embodiment of the multi-frequency antenna of the present invention is similar to the fourth preferred embodiment. The difference is that the fifth preferred embodiment does not include the second radiating arm of the fourth preferred embodiment. Segment 324 (see Figure 6) differs in efficacy from the fourth preferred embodiment in that the fifth preferred embodiment does not cover the band 2620 MHz to 2690 MHz.

Referring to FIG. 8, a preferred embodiment of the communication device of the present invention includes a multi-frequency antenna 10, a circuit module 20, and a coaxial cable 30.

The multi-frequency antenna 10 may be any of the foregoing first to fifth preferred embodiments.

The circuit module 20 includes an RF signal transmission end 201 for transmitting and receiving an RF signal and a reference ground 202.

The coaxial cable 30 is electrically connected between the multi-frequency antenna 10 and the circuit module 20 for exchanging the RF signal and has an inner conductor and an outer conductor (not shown). The opposite ends of the inner conductor are electrically connected to the feeding point 33 of the multi-frequency antenna 10 and the RF signal transmitting end 201 of the circuit module 20, respectively. The opposite ends of the outer conductor are electrically connected to the ground plane 2 of the multi-frequency antenna 20 and the reference ground 202 of the circuit module 20, respectively.

Referring to Table 1 below, the multi-frequency antenna 10 of the communication device is adopted. The three-dimensional antenna radiation efficiency measured by the first preferred embodiment, wherein -3 dB corresponds to a radiation efficiency of 50%, -6 dB corresponds to a radiation efficiency of 25%, and so on. It can be proved from Table 1 that the first preferred embodiment of the multi-frequency antenna can achieve effective radiation corresponding to the impedance bandwidth (i.e., the frequency band shown in the voltage standing wave ratio diagram of FIG. 3).

Incidental note: LTE in Table 1 above is a long-term evolution technology ( Abbreviation for Long Term Evolution, GSM is the abbreviation of Global System for Mobile Communications, PCS is the abbreviation of Personal Communication Service, and IMT-2000 is the International Mobile Telecommunications-2000. abbreviation of.

In summary, the foregoing preferred embodiment has the following advantages over the prior art multi-frequency antenna:

1. The floating parasitic arm 4 is not limited to be physically connected to the feed radiating unit 3 or physically connected to the ground plane 2, and energy can be transferred via electromagnetic coupling with the feed radiating unit 3 and Resonance is generated, thus providing additional design freedom.

2. The floating parasitic arm 4 is physically isolated from the ground plane 2 and is not electrically conductive, and therefore does not belong to the extension of the ground plane 2, so the feed radiation unit 3 is in the first direction by the floating parasitic arm 4 and The ground plane 2 is framed therein and does not cause radiation energy shielding or impedance mismatch.

Accordingly, the foregoing preferred embodiments are capable of achieving the objects of the invention.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

2‧‧‧ ground plane

21‧‧‧ edge

22‧‧‧Conductor patch

3‧‧‧Feed radiation unit

31‧‧‧Feeding arm

311‧‧‧Free end

312‧‧‧ top

32‧‧‧radiation arm

321‧‧‧The first free end

322‧‧‧First Radiation Arm Section

323‧‧‧Second free end

324‧‧‧second radiant arm section

33‧‧‧Feeding point

4‧‧‧suspension parasitic arm

41‧‧‧First free end

42‧‧‧Second free end

43‧‧‧Long arm section

431‧‧‧Connected end

44‧‧‧Bent arm section

5‧‧‧First short circuit parasitic arm

51‧‧‧ Grounding

52‧‧‧First free end

53‧‧‧Second free end

54‧‧‧First coupling upper edge

55‧‧‧Second coupling upper edge

6‧‧‧Second short-circuit parasitic unit

61‧‧‧ Grounding terminal

62‧‧‧Free end

7‧‧‧Substrate

71‧‧‧Upper surface

72‧‧‧ side

8‧‧‧welding block

G1‧‧‧first coupling gap

G2‧‧‧second coupling gap

G3‧‧‧3rd coupling gap

G4‧‧‧fourth coupling gap

P1‧‧‧First resonance path

P2‧‧‧ second resonance path

P3‧‧‧ third resonance path

P4‧‧‧ fourth resonance path

P5‧‧‧ fifth resonance path

P6‧‧‧ sixth resonance path

Claims (9)

A multi-frequency antenna comprising: a ground plane comprising an edge; a feed radiation unit spaced apart from the ground plane and adjacent to the edge, and comprising: a feed arm and a radiation arm, the feed arm having a proximity a free end of the edge, and a top portion of the edge away from the ground plane, and a feed point adjacent to an edge of the ground plane, the radiating arm being electrically connected to the top of the feed arm and having: a first a free end; a first radiating arm segment extending between the first free end of the radiating arm and the top of the feed arm, and from the free end of the feed arm to the first free end of the radiating arm a first resonant path substantially in an L shape for generating a resonance covering a first frequency band; a second free end opposite the first free end of the radiating arm; and a second radiating arm segment from the The feed arm protrudes out and extends to the second free end of the radiating arm, and is located on opposite sides of the feeding arm from the first radiating arm segment, and substantially faces an opening toward the feeding arm U-shaped, and the free end of the feed arm to the second of the radiating arm a third resonant path from the end for generating a resonance covering a third frequency band; and a floating parasitic arm physically isolated from the ground plane and the feed radiating element, and including a first free end and an opposite end a second free end, and a long arm segment adjacent to the first free end of the floating parasitic arm, and the long arm segment, the first radiating arm segment and the edge of the ground plane are at a first Interspersed in a spaced manner, the long arm segment and the radiating arm together define a first coupling gap; thereby, the floating parasitic arm and the feeding radiation unit transmit electromagnetic energy in a coupled manner, and the suspension A second resonant path between the first free end of the parasitic arm and the second free end is used to generate a resonance that encompasses a second frequency band. The multi-frequency antenna of claim 1, wherein an electrical length of the second resonant path is substantially a quarter wavelength corresponding to a center frequency of the second resonant frequency band. The multi-frequency antenna of claim 1, wherein the feed radiation unit is adjacent to a first free end of the floating parasitic arm and away from a second free end of the floating parasitic arm, and the long arm section, the first radiation The arm segment and the edge of the ground plane extend substantially in a second direction perpendicular to the first direction. The multi-frequency antenna according to claim 3, further comprising: a first short-circuit parasitic unit substantially in a T shape, electrically connected to the ground plane and physically isolated from the floating parasitic arm and the feed radiation unit, The first short-circuiting parasitic unit is located between the floating parasitic arm and the grounding surface in the first direction, and includes: a grounding end electrically connected to the grounding surface; a first free end adjacent to the feeding radiation unit And the first free end is located between the first radiating arm segment and the edge of the grounding surface in the first direction, and from the ground end of the first short-circuiting parasitic unit to the first short-circuiting parasitic unit a fourth resonant path of a free end Generating a resonance covering a fourth frequency band; a second free end, away from the feed radiation unit, and located between the floating parasitic arm and an edge of the ground plane, and from the ground end of the first short circuit parasitic unit a fifth resonant path of the second free end of the first short circuit parasitic unit is configured to generate a resonance covering a fifth frequency band; a first coupled upper edge connecting the first free end of the first short circuit parasitic unit, and the The first radiating arm segments partially overlap in the first direction and define a second coupling gap; and a second coupled upper edge connecting the second free end of the first shorting parasitic unit and the floating parasitic arm A third coupling gap is defined. The multi-frequency antenna according to claim 3, further comprising a second short-circuit parasitic unit electrically connected to the ground plane, the second short-circuit parasitic unit is substantially in an L shape, and the first short-circuit parasitic unit is in the second The direction is between the second short-circuit parasitic unit and the feed-in radiating unit, and the second short-circuit parasitic unit is spaced apart from the floating parasitic arm to down-convert the second frequency band. The multi-frequency antenna according to claim 5, wherein the second short-circuit parasitic unit comprises: a ground end electrically connected to an edge of the ground plane; and a free end located at the first short-circuit parasitic unit and the ground plane A sixth resonant path between the edges and from the ground of the second shorted parasitic element to the free end is used to generate a resonance covering a sixth frequency band. The multi-frequency antenna of claim 6, wherein the long arm section of the floating parasitic arm substantially from the first free end of the floating parasitic arm toward the second side Extending and having a connection end, and the feeding radiation unit, the first short circuit parasitic unit and the second short circuit parasitic unit are located between the long arm segment and an edge of the ground plane in the first direction, The floating parasitic arm further includes: a bent arm segment substantially in an L shape, and extending from a connecting end of the long arm segment to a second free end of the floating parasitic arm, and the bent arm segment and the first The second short circuit parasitic unit defines a fourth coupling gap. The multi-frequency antenna of claim 7, further comprising a substrate, the substrate comprising: an upper surface, the bent arm segment, the feed radiation unit, the first short circuit parasitic unit, and the second short circuit a parasitic unit; and a side perpendicular to the upper surface for positioning the long arm section. A communication device, comprising: the multi-frequency antenna according to any one of claim 1 to claim 8; a circuit module comprising an RF signal transmission end for transmitting and receiving an RF signal, and a reference ground And a coaxial cable electrically connected between the multi-frequency antenna and the circuit module for exchanging the RF signal, and having an inner conductor and an outer conductor, the inner conductor electrically connecting the feeding of the multi-frequency antenna And an RF signal transmission end of the circuit module, the outer conductor is electrically connected to a ground plane of the multi-frequency antenna and a reference ground of the circuit module.