阅读说明：本技术 双频双馈高增益滤波天线及电子设备 (Double-frequency double-fed high-gain filtering antenna and electronic equipment ) 是由 谢建华 杨椰楠 杨丽平 徐雨 于 2021-06-25 设计创作，主要内容包括：本发明公开了一种双频双馈高增益滤波天线及电子设备,包括PCB板、两个低频单元、三个高频单元、第一同轴线、第二同轴线、第三同轴线和CPW传输线；PCB板包括相对的第一面和第二面,CPW传输线包括CPW信号线和CPW地线；两个低频单元设置于PCB板的第一面上,三个高频单元设置于PCB板的第二面上；第二同轴线与第一低频单元连接,第一低频单元和第二低频单元通过第三同轴线连接；第一同轴线与第一高频单元连接,第一高频单元、第二高频单元和第三高频单元通过CPW传输线依次连接；CPW地线在第二高频单元的一侧处设有第一断缝。本发明可提升天线增益。(The invention discloses a double-frequency double-fed high-gain filter antenna and electronic equipment, which comprise a PCB (printed Circuit Board), two low-frequency units, three high-frequency units, a first coaxial line, a second coaxial line, a third coaxial line and a CPW (compact peripheral component interconnect) transmission line, wherein the PCB is provided with a first low-frequency unit and a second high-frequency unit; the PCB board comprises a first surface and a second surface which are opposite, and the CPW transmission line comprises a CPW signal line and a CPW ground line; the two low-frequency units are arranged on the first surface of the PCB, and the three high-frequency units are arranged on the second surface of the PCB; the second coaxial line is connected with the first low-frequency unit, and the first low-frequency unit is connected with the second low-frequency unit through a third coaxial line; the first coaxial line is connected with the first high-frequency unit, and the first high-frequency unit, the second high-frequency unit and the third high-frequency unit are sequentially connected through a CPW transmission line; the CPW ground line is provided with a first break at one side of the second high frequency unit. The invention can improve the gain of the antenna.)

1. A double-frequency double-fed high-gain filter antenna is characterized by comprising a PCB, a first low-frequency unit, a second low-frequency unit, a first high-frequency unit, a second high-frequency unit, a third high-frequency unit, a first coaxial line, a second coaxial line, a third coaxial line and a CPW transmission line; the PCB board comprises a first surface and a second surface which are opposite, and the CPW transmission line comprises a CPW signal line and a CPW ground line;

the first low-frequency unit, the second coaxial line and the third coaxial line are arranged on the first surface of the PCB, and the first high-frequency unit, the second high-frequency unit, the third high-frequency unit, the first coaxial line and the CPW transmission line are arranged on the second surface of the PCB;

the second coaxial line is connected with the first low-frequency unit, and the first low-frequency unit and the second low-frequency unit are connected through the third coaxial line; the first coaxial line is connected with the first high-frequency unit, and the first high-frequency unit, the second high-frequency unit and the third high-frequency unit are sequentially connected through the CPW transmission line;

the CPW ground wire is provided with a first broken joint at one side of the second high-frequency unit.

2. The dual-frequency double-fed high-gain filter antenna according to claim 1, further comprising a low-frequency feed point bonding pad and a high-frequency filter, wherein the low-frequency feed point bonding pad is arranged on the first surface of the PCB, and the second coaxial line and the third coaxial line are respectively connected with the low-frequency feed point bonding pad; the high-frequency filter is arranged on the second surface of the PCB; and a first through hole is formed in the position, corresponding to the low-frequency feed point bonding pad, of the PCB, and the high-frequency filter is connected with the low-frequency feed point bonding pad through the first through hole.

3. The dual-band double-fed high-gain filter antenna according to claim 1, further comprising a high-frequency feed point bonding pad, wherein the high-frequency feed point bonding pad is disposed on the second surface of the PCB board, and the first coaxial line and the CPW transmission line are respectively connected to the high-frequency feed point bonding pad.

4. The dual-frequency doubly-fed high-gain filtering antenna as claimed in claim 3, wherein a second broken seam is arranged at a connection position of the CPW signal line and the high-frequency feed point bonding pad.

5. The dual-band dual-feed high-gain filtering antenna according to claim 4, wherein the second broken seam is a straight seam, a curved seam or a broken seam.

6. The dual-band dual-feed high-gain filtering antenna according to any one of claims 3 to 5, further comprising a short-circuit line disposed on the first side of the PCB board; a second through hole is formed in the position, corresponding to the high-frequency feed point bonding pad, of the PCB, and a third through hole is formed in the position, corresponding to the CPW ground wire, of the PCB; one end of the short-circuit line is connected with the CPW signal line sequentially through the second via hole and the high-frequency feed point bonding pad, and the other end of the short-circuit line is connected with the CPW ground line through the third via hole.

7. The dual-band dual-feed high-gain filtering antenna according to claim 6, wherein the length of the short-circuited line is less than a quarter of the low-frequency operating wavelength.

8. The dual-band dual-feed high-gain filtering antenna according to claim 1, wherein the distance between the first low-frequency unit and the second low-frequency unit is a length of one wavelength when low-frequency signals are transmitted in the third coaxial line.

9. The dual-band dual-feed high-gain filtering antenna according to claim 1, wherein the distance between the second high-frequency unit and the first high-frequency unit is the same as the distance between the second high-frequency unit and the third high-frequency unit, and both are the length of one wavelength when a high-frequency signal is transmitted in the CPW transmission line.

10. An electronic device comprising a dual-band dual-fed high-gain filtering antenna according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of wireless communication, in particular to a double-frequency double-fed high-gain filter antenna and electronic equipment.

Background

At present, a dual-frequency double-fed high-gain WIFI antenna of a router or an ONT on the market usually supports dual-frequency operation of 2.4GHz and 5 GHz. To achieve high gain (gain >4dBi), typically 3 high frequency units are required and connected by coaxial cable, or to reduce cost, the coaxial cable is replaced with a single-sided CPW (coplanar waveguide) transmission line. The common denominator is that the middle high-frequency element is a pure parasitic element, on which there is only a small amount of coupled high-frequency power. Therefore, the amplitude distribution imbalance of the 3 high-frequency units is poor (generally not more than 3dB) in the side lobe suppression of an E-plane pattern, and the improvement of the main lobe gain is limited.

In addition, in actual production, due to the fact that the single-sided CPW (due to the fact that the low-frequency antenna oscillator is arranged on the other side, the double-sided CPWG with strong shielding capability cannot be used) has poor signal shielding capability, and the distance between the tail ends of the high-frequency oscillator and the low-frequency oscillator is small, the isolation degree is critical, and the isolation degree of mass-produced antennas cannot be stably larger than 20 dB.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: a dual-frequency and dual-feed high-gain filtering antenna and an electronic device are provided, which can improve the gain of the antenna.

In order to solve the technical problems, the invention adopts the technical scheme that: a double-frequency double-fed high-gain filter antenna comprises a PCB, a first low-frequency unit, a second low-frequency unit, a first high-frequency unit, a second high-frequency unit, a third high-frequency unit, a first coaxial line, a second coaxial line, a third coaxial line and a CPW transmission line; the PCB board comprises a first surface and a second surface which are opposite, and the CPW transmission line comprises a CPW signal line and a CPW ground line;

the first low-frequency unit, the second coaxial line and the third coaxial line are arranged on the first surface of the PCB, and the first high-frequency unit, the second high-frequency unit, the third high-frequency unit, the first coaxial line and the CPW transmission line are arranged on the second surface of the PCB;

the second coaxial line is connected with the first low-frequency unit, and the first low-frequency unit and the second low-frequency unit are connected through the third coaxial line; the first coaxial line is connected with the first high-frequency unit, and the first high-frequency unit, the second high-frequency unit and the third high-frequency unit are sequentially connected through the CPW transmission line;

the CPW ground wire is provided with a first broken joint at one side of the second high-frequency unit.

The invention also relates to an electronic device comprising a dual-frequency dual-feed high-gain filtering antenna as described above.

The invention has the beneficial effects that: the coaxial line in front of the high-frequency unit is replaced by the CPW transmission line, so that the cost can be reduced; through setting up the broken joint with CPW ground wire in middle high frequency unit unilateral for one side of middle high frequency unit becomes direct feed's dipole, compares in the parasitic element of the weak coupling feed in prior art scheme both sides, can balance the amplitude distribution of three high frequency unit, improves the vice lamella and suppresses, and then promotes the gain. The invention can solve the problem of low gain in the prior art.

Drawings

Fig. 1 is a schematic structural diagram of a dual-band dual-feed high-gain filtering antenna according to a first embodiment of the present invention;

fig. 2 is a schematic structural diagram of a dual-band dual-feed high-gain filtering antenna according to a second embodiment of the present invention;

FIG. 3 is a schematic standing wave diagram of the dual-band dual-feed high-gain filtering antenna according to the present invention;

FIG. 4 is a schematic diagram of isolation of the dual-band dual-feed high-gain filtering antenna according to the present invention;

FIG. 5 is a low frequency E-plane pattern of the dual-band dual-feed high-gain filtering antenna of the present invention;

fig. 6 is a high-frequency E-plane directional diagram of the dual-band dual-feed high-gain filtering antenna of the present invention.

Description of reference numerals:

1. a PCB board; 2. a first low frequency unit; 3. a second low frequency unit; 4. a first high frequency unit; 5. a second high frequency unit; 6. a third high frequency unit; 7. a first coaxial line; 8. a second coaxial line; 9. a third coaxial line; 10. a CPW transmission line; 11. a low frequency feed pad; 12. a high-frequency filter; 13. a high frequency feed pad; 14. short-circuit lines;

201. a first radiator; 202. a second radiator;

401. a third radiator; 402. a fourth radiator;

501. a dipole unit; 502. a parasitic element;

1001. a CPW signal line; 1002. a CPW ground line; 1003. a first broken seam; 1004. and (7) second breaking the seam.

Detailed Description

In order to explain technical contents, objects and effects of the present invention in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

Referring to fig. 1, a dual-band dual-feed high-gain filter antenna includes a PCB, a first low-frequency unit, a second low-frequency unit, a first high-frequency unit, a second high-frequency unit, a third high-frequency unit, a first coaxial line, a second coaxial line, a third coaxial line, and a CPW transmission line; the PCB board comprises a first surface and a second surface which are opposite, and the CPW transmission line comprises a CPW signal line and a CPW ground line;

the first low-frequency unit, the second coaxial line and the third coaxial line are arranged on the first surface of the PCB, and the first high-frequency unit, the second high-frequency unit, the third high-frequency unit, the first coaxial line and the CPW transmission line are arranged on the second surface of the PCB;

the second coaxial line is connected with the first low-frequency unit, and the first low-frequency unit and the second low-frequency unit are connected through the third coaxial line; the first coaxial line is connected with the first high-frequency unit, and the first high-frequency unit, the second high-frequency unit and the third high-frequency unit are sequentially connected through the CPW transmission line;

the CPW ground wire is provided with a first broken joint at one side of the second high-frequency unit.

From the above description, the beneficial effects of the present invention are: the CPW ground wire is provided with the broken seam at one side of the middle high-frequency unit, so that the amplitude distribution of the three high-frequency units can be balanced, the side lobe suppression is improved, and the gain is further improved.

The PCB further comprises a low-frequency feed point welding disc and a high-frequency filter, wherein the low-frequency feed point welding disc is arranged on the first surface of the PCB, and the second coaxial line and the third coaxial line are respectively connected with the low-frequency feed point welding disc; the high-frequency filter is arranged on the second surface of the PCB; and a first through hole is formed in the position, corresponding to the low-frequency feed point bonding pad, of the PCB, and the high-frequency filter is connected with the low-frequency feed point bonding pad through the first through hole.

As can be seen from the above description, the second coaxial line and the third coaxial line are conveniently connected by providing the low-frequency feed point bonding pad; by adding a high-frequency filter at the low-frequency feed point, the isolation of the high-frequency band is greatly improved.

Further, the PCB further comprises a high-frequency feed point welding disc, the high-frequency feed point welding disc is arranged on the second surface of the PCB, and the first coaxial line and the CPW transmission line are respectively connected with the high-frequency feed point welding disc.

As can be seen from the above description, the connection of the first coaxial line and the CPW transmission line is facilitated by providing the high frequency feed pad.

Furthermore, a second broken seam is arranged at the joint of the CPW signal wire and the high-frequency feed point bonding pad.

Further, the second broken seam is a straight seam, a curved seam or a broken seam.

As can be seen from the above description, the CPW signal line is provided with the broken seam at the high-frequency feed spot welding disc, so that the series distributed capacitance can be formed.

Further, the PCB comprises a short circuit line, wherein the short circuit line is arranged on the first surface of the PCB; a second through hole is formed in the position, corresponding to the high-frequency feed point bonding pad, of the PCB, and a third through hole is formed in the position, corresponding to the CPW ground wire, of the PCB; one end of the short-circuit line is connected with the CPW signal line sequentially through the second via hole and the high-frequency feed point bonding pad, and the other end of the short-circuit line is connected with the CPW ground line through the third via hole.

Further, the length of the short-circuit line is less than one quarter of the low-frequency operating wavelength.

As can be seen from the above description, by providing a short-circuit line, a parallel distributed inductance can be formed.

Further, the distance between the first low frequency unit and the second low frequency unit is the length of one wavelength when low frequency signals are transmitted in the third coaxial line.

Further, the distance between the second high frequency unit and the first high frequency unit is the same as the distance between the second high frequency unit and the third high frequency unit, and both are the length of one wavelength when the high frequency signal is transmitted in the CPW transmission line.

The invention also relates to an electronic device comprising a dual-frequency dual-feed high-gain filtering antenna as described above.

Example one

Referring to fig. 1, a first embodiment of the present invention is: a dual-frequency double-fed high-gain filtering antenna can be applied to a router or an ONT, and dual frequencies in the embodiment are 2.4GHz and 5GHz of WIFI respectively.

As shown in fig. 1, the Printed Circuit Board (PCB) 1 includes a first low frequency unit 2, a second low frequency unit 3, a first high frequency unit 4, a second high frequency unit 5, a third high frequency unit 6, a first coaxial line 7, a second coaxial line 8, a third coaxial line 9, and a CPW transmission line 10. The PCB board 1 comprises a first surface (top surface) and a second surface (bottom surface) which are opposite; the CPW transmission line 10 includes a CPW signal line 1001 and a CPW ground line 1002, and further includes a CPW signal line 1001 and two CPW ground lines 1002, where the two CPW ground lines 1002 are respectively located at two sides of the CPW signal line 1001. The first low-frequency unit 2, the second low-frequency unit 3, the second coaxial line 8 and the third coaxial line 9 are arranged on the first surface of the PCB board 1, and the first high-frequency unit 4, the second high-frequency unit 5, the third high-frequency unit 6, the first coaxial line 7 and the CPW transmission line 10 are arranged on the second surface of the PCB board 1.

The second coaxial line 8 is connected with the first low frequency unit 2, and the first low frequency unit 2 and the second low frequency unit 3 are connected through the third coaxial line 9. Further, the distance between the two low frequency units is about the length of one wavelength of the low frequency signal transmitted in the third coaxial line.

The first coaxial line 7 is connected to the first high frequency unit 4, and the first high frequency unit 4, the second high frequency unit 5, and the third high frequency unit 6 are connected in sequence through the CPW transmission line 10. Further, the three high-frequency units are equidistantly distributed, that is, the distance between two adjacent high-frequency units in the three high-frequency units is the same, which is about the length of a high-frequency signal when the high-frequency signal is transmitted in one wavelength in the CPW transmission line.

The CPW ground line 1002 is provided with a first break 1003 at one side of the second high frequency unit 5. At this time, the second high-frequency unit is a dipole + parasitic composite unit, wherein one side close to the first broken seam is a dipole unit 501, and the other side (i.e. the side where the CPW transmission line is short-circuited) is a parasitic unit 502. The CPW ground wire at the dipole side is provided with a slot, so that high-frequency signal current on the CPW ground wire directly flows to the dipole unit to form direct feed; the two L-shaped radiating arms separated by the first break in the second high-frequency unit form two radiating arms of a dipole. The parasitic element can only be indirectly fed by a small amount of space coupling current of the first high-frequency element and the third high-frequency element and weak induced current outside the CPW ground wire.

And the first high-frequency unit and the third high-frequency unit are dipole antennas and are directly connected with and fed by two ends of the CPW transmission line. The dipole antenna has two radiation arms, and when the CPW transmission line is used for feeding, one radiation arm needs to be connected with a CPW signal line, and the other radiation arm needs to be connected with a CPW ground wire so as to form a complete high-frequency signal loop.

Further, as shown in fig. 1, the printed circuit board further includes a low frequency feed pad 11 and a high frequency filter 12, the low frequency feed pad 11 is disposed on the first surface of the PCB board 1, and the second coaxial line 7 and the third coaxial line 8 are respectively connected to the low frequency feed pad 11; i.e. the low frequency feed pad 11, is used to connect the second 7 and third 8 coaxial lines. The high-frequency filter 12 is arranged on the second surface of the PCB board 1 and corresponds to the low-frequency feed spot welding disc 11 in position; the PCB board 1 is provided with a first through hole corresponding to the low-frequency feed point bonding pad, and the high-frequency filter 12 is connected with the low-frequency feed point bonding pad 11 through the first through hole.

Wherein the low frequency feed pad 11 is located in the first low frequency cell 2. Specifically, in the present embodiment, the first low frequency unit 2 includes a first radiator 201 and a second radiator 202, the first radiator 201 is a rectangle with a gap, the gap is adjacent to the second radiator 202, and the low frequency feed spot welding plate 11 is disposed at the gap, that is, the low frequency feed spot welding plate 11 is located between the first radiator 201 and the second radiator 202. The second radiator 202 is U-shaped, and the opening faces away from the first radiator 201. One end of the second coaxial line 8 is connected with the first radiator 201 and the low-frequency feed point pad 11 in sequence; one end of the third coaxial line 9 is connected to the second radiator 202 and the low frequency feed spot welding disc 11 in sequence, and the other end is connected to the second low frequency unit 3.

In a specific implementation, a first radiator may be formed by coating copper on a specific region of one end of the first surface of the PCB, and the first radiator may serve as a reference ground of the high frequency filter.

In this embodiment, the high-frequency filter is integrated by the PCB, without adding a surface-mounted device, and the antenna routing space is multiplexed, i.e., without adding extra cost and size.

In the embodiment, the gap is formed in the single side of the middle high-frequency unit of the CPW ground wire, so that the second high-frequency unit obtains direct feed of the CPW transmission line and becomes a dipole + parasitic composite unit, and other high-frequency and low-frequency units are in a half-wave dipole form. Therefore, the low-frequency unit forms a 2-unit array antenna, the high-frequency unit forms a 3-unit array antenna, the amplitudes of the high-frequency units are balanced, and compared with parasitic elements of weak coupling feed at two sides of the prior art, the amplitude distribution of three high-frequency units can be balanced, side lobe suppression is improved, gain is further improved, and higher gain characteristics are realized.

Meanwhile, the high-frequency filter is arranged at the low-frequency feed point, so that the high-frequency signal reaching the low-frequency antenna through space coupling is filtered when being transmitted to the low-frequency feed point bonding pad of the low-frequency antenna, the high-frequency isolation degree is improved, and the cost and the size are not additionally increased.

Example two

Referring to fig. 2, the present embodiment is a further development of the first embodiment, and the same points are not described in detail, but the present embodiment further includes a high-frequency feed spot welding disc 13, where the high-frequency feed spot welding disc 13 is disposed on the second surface of the PCB board 1, and the first coaxial line 7 and the CPW transmission line 10 are respectively connected to the high-frequency feed spot welding disc 13; i.e. the high frequency feed pad 13, is used to connect the first coaxial line 7 and the CPW transmission line 10.

In this embodiment, a high frequency feed spot welding disc 13 is located in the first high frequency unit 4. The first high-frequency unit 4 comprises a third radiator 401 and a fourth radiator 402, one end of the first coaxial line 7 is sequentially connected with the third radiator 401 and the high-frequency spot feeding pad 13, a CPW signal line 1001 is connected with the high-frequency spot feeding pad 13, and a CPW ground line 1002 is connected with the fourth radiator 402.

Further, a second broken seam 1004 is arranged at the joint of the CPW signal line 1001 and the high-frequency spot-feeding welding disc 13. Wherein, the second broken seam 1004 can be a straight seam, a curved seam or a broken seam.

The capacitor is formed by two conductors which are close to each other and a layer of non-conductive insulating medium which is sandwiched between the two conductors. Therefore, a capacitor is realized from a physical structure by arranging a broken seam on the CPW signal wire, and the capacitor is not a surface-mounted device, but is realized by directly using PCB wiring and utilizing transmission line distribution parameters, so that the capacitor is called a distributed parameter capacitor. Therefore, the CPW signal wire is provided with a broken seam at the high-frequency feed spot welding disc, and series distributed capacitance can be formed.

Further, the PCB also comprises a short circuit line 14, wherein the short circuit line 14 is arranged on the first surface of the PCB 1; a second through hole is formed in the position, corresponding to the high-frequency feed spot welding disc 13, of the PCB 1, and a third through hole is formed in the position, corresponding to the CPW ground wire 1002, of the PCB; one end of the short-circuit line 14 is connected to the high-frequency spot welding feeding pad 13 through the second via hole, and further connected to the CPW signal line 1001 through the high-frequency spot welding feeding pad 13, and the other end of the short-circuit line 14 is connected to the CPW ground line 1002 through the third via hole. Wherein the short-circuit line 14 has a length less than one quarter of the low-frequency operating wavelength.

Any one section of PCB wire can be equivalent to a distributed parameter circuit of series inductance and parallel capacitance, and when the wire is thin and long, the inductance characteristic is obviously reflected, so that one section of thin and long short circuit wire is equivalent to a short circuit distributed parameter inductance. Therefore, by providing the short-circuit line, a parallel distributed inductance can be formed.

The LC circuit of series capacitor and parallel inductor forms a high-pass low-resistance filter which can filter low-frequency signals. In the embodiment, the second broken seam and the short circuit line are arranged, so that the ideal low-frequency filter with high pass and low resistance is formed, and the PCB space is multiplexed with the high-frequency and low-frequency antenna, so that the excellent low-frequency isolation performance can be realized, and the cost and the size are not additionally increased.

In this embodiment, the second break and the short-circuit line are provided at the same time to form an ideal low-frequency filter. Of course, in other embodiments, only the second break or only the short-circuit line may be provided, partially implementing the low-frequency filtering function.

EXAMPLE III

Referring to fig. 3-6, the present embodiment is test data of the above embodiments.

Fig. 3 is a schematic standing wave diagram of the dual-band dual-feed high-gain filtering antenna of the present invention, wherein S11 represents a low-frequency standing wave, and S22 represents a high-frequency standing wave, which are all less than 2. Fig. 4 is a schematic diagram of the isolation of the dual-band dual-feed high-gain filtering antenna of the present invention, wherein S21 represents the isolation, and it can be seen from the diagram that the isolation of both high and low frequencies is greater than 20 dB.

Fig. 5 is a low-frequency E-plane directional diagram of the dual-band dual-feed high-gain filtering antenna of the present invention, and it can be seen that the maximum radiation direction is in the horizontal plane. Fig. 6 is a high-frequency E-plane directional diagram of the dual-band dual-feed high-gain filtering antenna of the present invention, and it can be seen that the maximum radiation direction is located in the horizontal plane, and the side lobe suppression is greater than 5 dB.

In summary, according to the dual-frequency and dual-feed high-gain filter antenna and the electronic device provided by the invention, the coaxial line in front of the high-frequency unit is replaced by the CPW transmission line, so that the cost can be reduced; the CPW ground wire is provided with the broken seam at one side of the middle high-frequency unit, so that one side of the middle high-frequency unit becomes a direct-feed dipole, and compared with the parasitic units with weak coupling feed at two sides in the prior art, the amplitude distribution of the three high-frequency units can be balanced, the side lobe suppression is improved, and the gain is further improved; the high-frequency filter is arranged at the low-frequency feed point, so that the isolation of a high-frequency band is greatly improved; a broken seam is arranged on the CPW signal wire near the high-frequency feed point, and a short circuit wire with the wavelength less than one quarter of the low frequency is arranged to form a low-frequency filter, so that the isolation of a low-frequency band is further improved; the high-frequency filter and the low-frequency filter are integrated on the same PCB, surface-mounted devices do not need to be added, and the routing space of the antenna is multiplexed, i.e. the cost and the size do not need to be additionally increased.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.