LOW -LOSS FOUR-ELEMENT ENHANCED PATCH MM-WAVE ANTENNA WITH GAIN CONTROL TUNABILITY AND RECONFIGURABLE FEATURES

Abstract

The invention describes a frequency-reconfigurable and gain-enhanced millimeter-wave antenna designed on a Rogers RT Duroid 5880 substrate (101) with a thickness of 0.508 mm and permittivity of er=2.2. The antenna features a primary rectangular patch (105) with appended side (103) and top patches(104) to form a four-element array, achieving a gain of 9.81 dBi over dual bands (29.83–33.79 GHz, 35.44–37.33 GHz). Central rhombus-shaped (106) slots enhance impedance matching, while two PIN diodes (107) facilitate frequency reconfiguration, and a varactor diode (108) enables fine-tuning with a 2.1 pF capacitance at 28V, providing adaptable performance across Ka-band frequencies

Specification

Description:The following specification particularly describes the invention and the manner in which it is to be performed:
TECHNICAL FIELD

The present invention relates to the filed of wireless transmission and more particularly to relates to the field of tuneable and reconfigurable mm-wave antenna

BACKGROUND
The microwave frequency range spectrum is usually ranging from 300 MHz to 300 GHz and millimeter wave (mm-wave)range from 30GHz to 300THz .As the lower frequency range becomes crowdy with 5G and other microwave/wireless communications applications from the past two decades technologies are growing additional extensive in markets around the entire globe.
A lot of investigations have been available on microstrip patch antennas in the low-frequency range FR1 band (Sub-6GHz <6GHz) for 5G applications[2]. However, few literatures are available within the FR2 band Sub-6GHz band (24.75GHz to 60GHz).Path loss, transmission loss, shadowing, and user effects are various challenges in mm-wave propagations in a mobile terminal[3].With the advancement in MMIC, MIC, and HIC integrated circuits and microwave devices, the mm-wave antennas and components are most demanding.
Amm-wave antenna/components are highly recommended for transmitter/receivers in radar, satellite communications, launchers, and high-speed wireless communications in microwave/mm-wave transitions Therefore, the design of mm-wave antenna for the next generation of 5G and beyond communications with a new approach is extremely demanding.
CN209544599U 5G broadband millimeter-wave antenna array, made of LCP material, is designed for high-speed wireless communications. It features multiple antenna elements spaced at regular intervals, aiming to operate at millimeter-wave frequencies, making it compatible with 5G network infrastructures.
US10673135B2 describes 5G terminal antenna with reconfigurable radiation patterns. The antenna includes multiple sub-arrays that are connected to a radio frequency (RF) frontend module. The sub-arrays can be switched between transmitting and receiving modes, allowing the antenna to dynamically adjust its radiation pattern for optimal performance. The antenna is designed for operation in 5G frequency bands, enhancing communication efficiency in 5G terminals. The use of advanced materials and reconfigurable components makes it suitable for high-speed data transmission in modern wireless networks. But it lacks multi-frequency or multi-band operation, and lacks real-time gain control.
CN110892580B describes a multiband millimeter-wave antenna array designed for high-frequency applications, particularly in 5G wireless communication systems. The antenna structure includes multiple radiating elements and uses a dielectric substrate for better performance and efficiency. The construction focuses on creating an antenna that can support various frequency bands, ensuring reliable communication over a wide range of frequencies. The materials used include standard dielectric substrates commonly applied in mm-wave designs to minimize losses. The working frequencies are in the millimeter-wave range (above 10 GHz), making it ideal for 5G and beyond wireless communications. The application targets advanced communication systems that require high-speed data transmission, enhanced connectivity, and multi-frequency operation. But it lacks active frequency tuning or gain control, limiting its adaptability in dynamic environments. But it but lacks active tuning or reconfigurability features.
Based on the limitation of the mentioned patents , there is the the need for an innovative antenna design that provides dynamic frequency reconfigurability, dual-band operation, gain control, and cost-effective construction.

SUMMARY
The invention introduces a novel technique of patch size enhancement using duplication of the primary patch without a traditional array setup. The use of PIN diodes for frequency reconfiguration and a varactor diode for sensing is a unique approach to achieve both gain enhancement and frequency agility, setting this design apart from existing state-of-the-art technologies
The object of the invention is to design an antenna array by just duplicating the main patches with a slight increase in the substrate dimensions of the antenna and adjoining them in such a way that they will result in good reflection and radiation characteristics by eliminating the need of tedious power divider/impedance transformer techniques in the case of array antennas
Another object of invention is to design a mm-wave microstrip patch antenna that can work within the microwave Ka-band 26GHz to 40GHz.
Another object of invention is to enhance the size of the patch by patch repetition and impedance matching method to achieve enhanced gain.
Another object of invention is to is to control the operation of the four antenna elements by switching two PIN diodes (BAR6402V) and one varactor diode (BB 135, 115) as sensing elements within the specified mm-wave range to achieve a dual-band reflection coefficient


BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing detailed description of embodiments is better understood when read in conjunction with the attached drawing.
Figure 1
Figure 2 illustrates the trimetric front and rear view of the proposed antenna
Figure 3 illustrates the radiating patch development in terms of reflection coefficient, S11(dB) against frequency plot
Figure 4 illustrates reflection Coefficient tuning of the 4-element antenna using varactor diode.
Figure 5 illustrates reflection Coefficients plots of 4-element frequency reconfigurable antenna with PIN diodes switching
Figure 6 illustrates reflection Coefficients plots of proposed 4-element frequency reconfigurable antenna
Figure 7 illustrates the proposed fabricated antenna prototype models
Figure 8 illustrates proposed antenna reflection coefficient and radiation pattern measurements photographs
Figure 9 illustrates proposed Antenna simulated and measured reflection coefficient plots
Figure 10 illustrates 3D- Radiation Patterns without PIN Diodes and With two PIN Diodes switching four Cases
Figure 11 illustrates Gain plot of the proposed mm-wave Antenna
Figure 12 illustrates current density distributions of the proposed antenna.

DETAILED DESCRIPTION
In one of the embodiments, for mm-wave (26 GHz to 40 GHz) applications operations, a center frequency of 32.5 GHz was preferred as the design frequency. A low-loss Rogers RT Duroid substrate was selected for the mm-wave range.
In another embodiment, the antenna design begins with the analysis of a conventional rectangular patch antenna. A rectangular antenna patch length and patch width were evaluated by using the standard microstrip rectangular patch analysis formulas. The antenna is fabricated on a substrate (RT Duroid 5880) having permittivity er = 2.2, low-loss tangent (tand = 0.0009), and thickness h=0.508mm. A 50? microstrip feed line width and length are evaluated with the help of standard microstrip line theory. The length of the feed line is kept one-fourth of the guided wavelength long i.e. Lf = ?_g/4 (1.687mm) and the evaluated width is 1.5652mm.
In another embodiment, for higher frequency applications the patch area tremendously decreases and most of the area of the substrate is free from copper. Therefore, at mm-wave (32.5GHz), the patch size (LP×WP) is reduced to 2.7735mm×3.6488mm and the parent size of the substrate (LP+Lf+3h) × (3h+WP+3h) becomes 5.9845mm ×6.6968mm. The reduced ground length Lg=1.8mm towards the feed (Lg??_g/4) increases the overall bandwidth of the single-element patch antenna. A rhombus (a circle of radius RC=1mm with four segments) of each arm length equal to 1.4142mm had been placed at the center to improve the reflection coefficient, S11 values below -10dB.
Referring to figure 2, the single-element conventional antenna and slotted antennas are presented in (201). To enhance the antenna gain by a sufficient amount the duplicate three more patches are arranged on the top surface of the substrate without affecting the ground length as shown in (202). All four elements are connected by a 106? impedance rectangular joint of length, ?_g/8 and width, ?_g/16 . So that maximum power will transfer to each element. The three appended outer antenna patches are connected as shown in (202) by 45? rectangular slant stubs.
Referring to figure 2, to control the gain and bandwidth with frequency reconfigurability features two PIN diodes (BAR6402V) are connected between the main patch and two side patches. To improve the tuning and sensing a varactor diode (BB 135, 115) is introduced between the front patch and main patch. The top and rear views of the geometrical structure of the low-loss ultra wideband BAR6402V controlled antenna with patch size enhancement for mm-wave monopole antenna is represented in (202).
In another embodiment, the evaluated and simulated design dimensional parameters of single-element and four-element proposed antennas have been illustrated in Table 1.

Table 1.Dimensions of the modified array patch antenna

Parameter Single Element Patch (in mm) Four-Elements Patch
(in mm)
Patch Length, LP 2.7735 2.7735
Patch Width, WP 3.6488 3.6488
RT Duuroid5880 Substrate thickness, h 0.508 0.508
Substrate Length, LS=Lf+LP+3h 5.9845 8.6345
Substrate Width, WS=WP+6h 6.6968 11.9968
Feed Length, Lf==?_g/4 1.687 1.687
Feed Width, Wf 1.5652 1.5652
Ground Length, Lg 1.8 1.8
Ground Width, Wg=WS 6.6968 11.9968
Width of all square slot arms
Arm1=Arm2=Arm3=Arm4 (Warm) 1.414213562 1.4142
Length of Rectangular joints between patches, LJ=?_g/8 0.8 0.8
Width of Rectangular joints between, WJ=?_g/16 0.4 0.4
Outer slant line Lengths, L1 ----- 6.22
Inner slant line Lengths, L2 ----- 3.8391
Circular slot-Radius (RC) with 4-segments 1.0 1.0
Number of Patches 1 No. 4 No.

Referring to figure 3, the radiating patch is developed in six steps. The step-by-step development of the patch is illustrated in Fig. 3 with their family of reflection coefficient plots. Table 2 shows the resultant parameters of all six cases. In step first conventional rectangular single-element patch (301) is analyzed, it results in a wide fractional bandwidth but a low reflection coefficient and gain. The second step involves cutting a rhombus slot (302) at the centre of a rectangular patch to improve the reflection coefficient below -10dB. The third step connects three similar rhombus-slotted radiating patches (303) using 106? rectangular joints of each length, ?_g/8 and width, ?_g/16 to couple maximum power in the three sections from the main patch. This results in the lowest reflection coefficient value of -36.73dB at 31GHz and further enhancement in gain value but narrowing -10dB fractional bandwidth. In the fourth step, the two side patches are connected with the front patch by two 45? slant sections of width equal to the half of the patch length (304). This couples more current into the front patch from the two side patches and result in further enhancement in gain value 8.32dBi and wider-10dB FBW from 29.99GHz to 33.20GHz. The fifth step removes two side joints to connect two-PIN diodes BAR6402V (305), improving gain value gain value of 9.66dBi at the design frequency of 32.5GHz and widen the bandwidth from 30.16GHz to 36.56GHz. The final step removes the middle joint of the front patch for connecting one varactor diode for tuning and sensing purposes (306), resulting in resonating and design frequencies in close approximation with little decreased gain value of 8.13dBi and -10dB FBW 29.85GHz to 35.08GHz. Table 2 shows the resultant parameters of all six cases

Table 2. Radiating patch development

Antrnna Geometry Development

Design fr
(GHz) S11 (dB) -10dB BW
(fL- fH GHz) Gain
(dBi)
@fr S11 @
32.5GHz (dB) Gain @ 32.5GHz
(dBi)
Single-element antenna (301) 27.0 -16.04 (22.35-35.64) 3.82 -12.02 6.79
Single-element antenna with square slot (302) 26.20 -17.70 (21.65-34.36) 6.51 -11.12 7.02
4-element antenna with square slot (303) 31.04 -36.73 (29.82-32.37) 6.97 -9.27 7.73
4-element antenna with square slots and slant sections (304) 31.88 -16.67 (29.99-33.20) 8.31 -14.06 8.32
4-element slotted- antenna with PIN diodes cuts (305) 35.24 -18.65 (30.16-36.56) 9.11 -13.57 9.66
4-element slotted- antenna with PIN and Varactor diodes cuts (306) 32.67 -14.37 (29.85-35.08) 8.15 -14.34 8.13
* fr=Resonance Frequency; S11=Reflection Coefficient; BW=Bandwidth; @=at

In another embodiment, the varactor diode is most suitable at radio frequencies (RF) for tuning any antenna. The varactor diodes operate in reverse bias and show variation in the capacitance with the increased reverse bias voltage. Here a varactor diode BB 135,115 is connected between the main patch and the front patch. The varactor diode BB135, 115 has a capacitance of 2.1pF when 28V DC voltage is applied across it, and when to reverse bise DC supply decreases to 0.5V its capacitance value becomes 21pF. The reflection coefficients of three cases, when no varactor diode is connected between the slot and with 28V and with 0.5V DC power supply, have been studied and the experimental results are tabulated in Table 3 and their curves are illustrated in Fig. 4.

Table 3. Tunning of Four-element slotted antenna using varactor diode
4-Element Slotted Antenna Varactor diode voltage and tuning capacitor fr
(GHz) S11 (dB) -10dB BW
(fL- fH GHz) Gain
(dBi)
At fr S11 at
32.5GHz (dB) Gain at 32.5GHz
(dBi)
With PIN and Varactor diodes cuts WithoutVaractor
i.e. Unbiased 32.67 -14.37 (29.85-35.08) 8.15 -14.34 8.13
With PIN cuts and Varactor diode V=28V, C=2.1pF 35.24 -19.99 (29.98-36.41) 8.01 -13.09 9.68
With PIN cuts and Varactor diode V=0.5V, C=21pF 35.24 -19.50 (29.95-36.43) 9.15 -13.22 9.70

Referring to figure 4 and Table 3 above, it is observed that the connection of varactor diodes widens the bandwidth and enhances the antenna gain values while shifting/tunes the frequency at 35.24GHz. It also observed that the decreased reverse bias voltage improves the reflection coefficient value below -10dB
Referring to figure 5 and table 4, the antenna is frequency reconfigured by connecting two PIN diodes BAR6402V in the replacement place of the two side patch joints. When no varactor diode is connected in the front patch joint place, then four switching mode digital combinations are experimented and their resultant data have been collected in Table 4 and are illustrated in Fig. 5. All four switching modes provide the gain values at design frequency 32.5GHz approximately 8.70dBi with improved reflection coefficient and bandwidth when both PIN diodes are in ON states (forward-biased) The highest gain of the antenna is achieved when other PIN diodes are in OFF states (reverse biased).The resonance frequency and shapes of all the reflection coefficients remain unchanged.

Table 4. Four-element slotted antenna switching with Two PIN diodes
Two PIN diodes switching Without Varactor diode
D1, D2 fr
(GHz) S11 (dB) -10dB BW
(fL- fH GHz) Gain
(dBi)
At fr S11 at
32.5GHz (dB) Gain at 32.5GHz
(dBi)
OFF, OFF 31.95 -12.47 (30.0-34.09) 8.30 -12.10 8.74
OFF, ON 31.95 -12.72 (29.94-36.41) 8.34 -12.41 8.72
ON, OFF 32.01 -13.01 (29.87-34.36) 8.32 -12.72 8.68
ON, ON 32.01 -13.07 (29.87-34.81) 8.32 -12.89 8.69

Figure 6 and Table 5 indicates frequency reconfigure With varactor diode set for 2.1pF @ 28V. A varactor diode is connected at the location of the front partch joint and the two PIN diodes are connected at the location of the two-side patch joints. When the varactor diode is supplied with a 28V DC power supply then it behaves as a 2.1pF capacitor and the four digital switching combinations of two PIN diodes ON and OFF states operations have been experimentally performed. The experimentally optimized results of all four switching modes have been arranged in Table 5and illustrated in Fig.6.

Table 5. Four-element slotted antenna switching with Two PIN diodes with varactor diode capacitance 2.1pF
Two PIN diodes switching With Varactor diode
D1, D2 fr
(GHz) S11 (dB) -10dB BW
(fL- fH GHz) Gain
(dBi)
At fr Gain (dBi)
at 32.5
GHz
OFF, OFF 31.62, 36.37 -12.69, -11.23 (29.80-33.34), (35.77-36.85) 9.15, 9.12 9.55
OFF, ON 31.83, 36.24 -12.27, -12.70 (30.03-33.47), (35.32-36.92) 9.42, 7.0 9.81
ON, OFF 31.75, 36.50 -12.35, -13.06 (29.99-33.41), (35.64-37.27) 9.20, 8.71 9.65
ON, ON 31.83, 36.50 -13.10, -13.51 (29.83-33.79), (35.44-37.33) 9.21, 8.65 9.47


It is

It is noticed that a dual-band reflection coefficient occurs in all four switching modes. The first resonating frequency is because of the frequency reconfigurability of the two PIN diodes and the second resonance is due to the tuning of the antenna because of the varactor diode. As the switching mode moves from OFF, OFF states to ON, ON states every time the improved reflection coefficient values are achieved with fine resonance tuning frequencies in the two bands as illustrated in Fig.6.
In another embodiment, the method of fabricating the proposed antenna is as follows: a spatially arranged 50? SMA female connector of frequency range up to 50GHz is soldered at the end with great concern for the RF excitation. An enhanced patch size wideband monopole antenna for mm-wave application is fabricated using the photolithography, UV exposure, and etching processes on a piece of 8.6345 mm×11.9968 mm RT Duroid 5880 of height 0.508mm.
Figure 7 illustrates the prepared prototypes of the antenna model with front and rear views without diodes and with PIN and varactor diodes supply wire soldering.
In another embodiment, the proposed enhanced patch mm-wave wideband antenna is measured and tested in the microwave laboratory on a vector network analyzer (Agilent N5247A) and anechoic chamber.
Referring to figure 8, the reflection coefficient, gain, and radiation pattern measurement are obtained using the experimental hardware setup.
In another embodiment, The reflection coefficient of the antenna is measured with the vector network analyzer (Agilent N5247A) which can measure uptoa frequency of 67GHz. The antenna is proposed for Ka-band 26 GHz to 40 GHz. The performance parameters are measured and tested from 26 GHz to 40GHz and compared with the simulated results.
Referring to figure 9, initially, the antenna reflection coefficient was measured without connecting the PIN diodes and varactor diodes as displayed in (901). It is noticed from the reflection coefficients plots the simulated and measured reflection coefficients are found in concord with better reflection coefficient value and higher upper frequency and hence wider measured -10dB fractional bandwidth.
Referring to figure 9, after making the slot at the position of the patch joint a varactor diode BB135,115 is connected at the same place of the front and main patch joint. Then a reverse-biased DC supply voltage of 28V is applied across the varactor diode that corresponds to a capacitor 2.1pF. The simulated and measured reflection coefficient parameters in this case are compared in (902) and they are found in excellent match with each other.
Referring to figure 9, finally, two PIN diodes BAR6402V are placed in replacement of the side patch joints,and a 28V DC supply is connected in the front joint location. The reflection coefficients of all four switching modes simulated reflection coefficients are compared with the measured four switching modes of two PIN diodes. All four switching modes' reflection coefficients have better reflection coefficients below -10dB with improved wider bandwidths as shown in (903).
Referring to figure 10. the radiation patterns of the proposed antenna at the design frequency 32.5GHz without connecting any diodes are shown in (1001). This results in 8.15dBi gain with bidirectional radiation patterns in the E-plane and omnidirectional radiation patterns in the H-plane. The gain radiation patterns of all four switching modes are illustrated in (1002). All switching operations result in improved gains as compared to without diode connection cases. All four switching modes (OFF, OFF; OFF, ON; ON, OFF; and ON, ON) results peak gain of 9.55dBi, 9.81dBi, 9.65dBi, and 9.47dBi respectively. The maximum value of gain is the result of the OFF, and ON switching states of the two PIN diodes with varactor diode supplied with maximum reverse bias bearable DC voltage i.e. 28V.
Referring to figure 11, the antennae without diode connections have lower values of gain over the entire frequency range. When the antenna falls under the switching operations of the PIN diodes the antenna gain enhances after a frequency of 30GHz. The antenna gain of 12.46 dBi is maximum at the frequency of 39.60GHz with two PIN diodes ON, and OFF states switching mode and approximately 9.55dBi at the main design frequency 32.5GHz in all the switching modes of operations.
In another implementation, for the proposed antenna ,the antenna gain is controlled by the switching mode of the two PIN diodes.
Referring to figure 12, The blue color shows the lowest current while the red color is corresponding to the maximum current magnitudes. It is noticed from the four switching modes when both diodes are either in ON states or in OFF states as represented in (1201), the maximum current will couple into the three patches from the main patch and hence corresponding to this the antenna radiation becomes smaller and hence the gain enhancement in these cases 9.55dBi and 9.47dBi respectively. When either one diode is in its ON State or one diode is in OFF state as represented in (1202), in these switching mode cases very small current coupling has occurred, and therefore antenna radiation is enhanced in these cases and it will results improved antenna gain values 9.81dBi, and 9.65dBi respectively.
In another embodiment, proposes a novel four-element patch antenna designed for millimeter-wave (mm-wave) applications, specifically within the Ka-band.
In another embodiment, The antenna enhances the size of the patch through patch duplication and employs slotted patches for better impedance matching and reflection loss reduction, ensuring high gain and low losses.
In another embodiment, the proposed antenna integrates two PIN diodes (BAR6402V) to allow frequency reconfiguration, enabling the antenna to switch between different frequency bands.
In another embodiment, a varactor diode (BB135 115) is used for fine-tuning the operating frequency and improving bandwidth, achieving dual-band operation in the 29.83 GHz to 33.79 GHz and 35.44 GHz to 37.33 GHz ranges
, Claims:1. A frequency-reconfigurable, and gain-enhanced millimeter-wave antenna comprising:
a. a Rogers RT Duroid 5880 substrate (101) of thickness 0.508 mm and permittivity er=2.2;
b. A main rectangular radiating patch (102) of dimensions 2.7735 mm × 3.6488 mm;
c. three rectangular patches comprising of two side patches (103) and one top patch (104) of identical dimensions appended to the main patch (102) to form a four-element array;
d. a 50O microstrip feedline (105) optimized for the design frequency of 32.5 GHz;
e. a rhombus-shaped slot (106) with a radius of 1.0 mm cut at the center of the each radiating patch to enhance impedance matching and reduce reflection losses;
f. Two PIN diodes (107) connected between the main patch and the side patches for frequency reconfiguration for achieving the gain enhancement control;
and
g. A varactor diode (108) connected between the main patch and the front patch , for achieving frequency tuning with a capacitance values of 2.1pF at 28V;
wherein the antenna is characterized by achieving a gain of 9.81dBi in the frequency range of 29.83 GHz to 33.79 GHz and 35.44 GHz to 37.33 GHz;

2. The antenna as claimed in claim 1, wherein, the two PIN diodes (BAR6402V) enable frequency reconfiguration across multiple switching modes, allowing the antenna to switch between different frequency bands in the Ka-band range.
3. The antenna as claimed in claim 1, wherein, the varactor diode provides frequency tunability by adjusting the reverse bias voltage, resulting in fine-tuned resonance frequency and enhanced bandwidth

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