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Chip Antenna for Millimeter Wave Communications

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Chip Antenna for Millimeter Wave Communications

Abstract

The study deals with the integration of chips with the technology in wave communications that addresses the concerns on the efficiency of performance of chip antenna in receiving and sending information through different wireless communication system. This presents the different advantages and possibilities that could be achieved in using small-sized chips but obtaining the optimum level of efficiency. Millimeter-wave communications include the full utilization of millimeter-wave antennas which are integrated for systems which works on frequencies higher than 10GHz. Considering the elements of bandwidth, higher efficiency and the relatively small size of the chip antenna it is expected that manufacturing process and precision and material selection are crucial in the design of the system. The yield of the antenna in terms of sending and receiving electromagnetic interference is affected and this is measured through the efficiency of feeding the line of communication among devices.

Introduction

Chip antennas are known for their function to radiate high frequency electromagnetic waves. Because of this, chip antennas are often embedded in circuit boards and with the limited range chip antennas are best used for WiFi routers and cell phones. Chip antennas are also known to function the same way as regular antennas but the advantage of it is its small size which makes it possible for chip antennas to be placed in circuit boards of smaller devices. Chip antennas are the best alternative for regular antennas which are sometimes impractical to use because of the less in cost it entails while serving the same purpose. There are several more advantages in using chip antennas, one of which is the lay out. Due to its nature as a ground dependent antenna, chip antennas need to be placed in a well-proportioned and accurately sized plane in order for it to perform its resonant function.

The PCB is often used as the plane for chip antenna, the way the components of the PCB are placed and properly spaced from each affects the performance of the chip antenna. Even if it is placed on PCB together with other components, the chip antenna still needs to be placed on the edge of the plane (PCB) separated from the other components that is uninhibited by metallic components and ground free. The PCB should also be placed in a vertical position in order to enable the chip to broadcast in all possible directions.

The antenna aperture is also an important consideration. This affects the efficiency of transmission; the impedance of the materials should be balanced with the charge transmitted and the electromagnetic wave. When there is a minimal energy reflected then maximum charge gives an efficient transmission.

Chip antennas are commonly used for handheld electronic devices such as cell phones. The chips are embedded in the PCB and are protected by polymer or rubber enclosures which serve as protector from environmental elements such as dusts, moisture, shock vibration and chemicals. Aside from handheld devices, chip antennas are widely used in telecommunications. These use ranges from tablets, computers, portable television, peripherals of personal computers, cell phones, WiFi and WLAN routers, headsets, PDAs, satellite radio, GPS devices, and USB dongles. And with its intensive use in telecommunications, chip antennas also comply with the standards sets by the Institute of Electrical and Electronics Engineers as reflected in the IIEE 802.11 or commonly known as the wireless networking standard.

Wave communication refers to the utilization of electromagnetic radiation in order to transmit information. This includes the use of different types of waves like microwaves, infrared, radio waves, light and radiation. Since the beginning of 19th century communication has taken a rapid change. Morse code had been the means of communication that is used for long distances. But the use of Morse code requires flashes of light and the visibility of signals is limited within a short distance only. Modern day communication still involves codes and signals however it has changed in terms of its expanse. Today, both analogue and digital signals are very significant in communication. The signals sent through analogue features a change in the frequency and amplitude which affects the quality of music transmitted. However digital signals only send using signs with values of 0 and 1 which corresponds to on and off.

Along the process of transmission, both analogue and digital signals can catch unwanted signals which distort the original signal. Digital signals the unwanted signal which is referred to as noise, can be cleaned up through regeneration. But for analogue signals when the original signal is amplified the noise is likewise amplified too. This makes digital signals better option than analogue.

The application of millimeter waves in systems had made significant impact in communications and other fields. With the emergence of millimeter wave devices, communication has been further enhanced with smaller size yet capable of giving strong interference and several advantages. Aiming to provide better efficiency in wireless communication utilization of smaller antenna that complements the latest technology in semiconductors, chip antenna are very useful given the low cost of production it presents.

Background of the study

The integration of chip antenna using silicon technologies in millimeter wave communication is significant in modifying the complex process and developing a low-cost system of communication and sensing application. Together with two useful fabrications process like SiGe and CMOS the radiation efficiency of the antenna can be maximized. The reduction of the on-chip antenna in miniature size have made it possible to integrate it even to the smaller electronic devices but reduction of its size have not been equally to have reduced its functionality. With more technologies and electronic devices powering up their functions not only on terms of capacity but even so on their efficiency it is indeed significant to achieved a breakthrough in the fabrication process where low budget is required but the on-chip antenna will be able to power up more.

The aim to power up the efficiency of on-chip antenna is attributed to the increasing traffic in wireless data communication. The millimeter-wave communications is the most likely answer to this predicament that will pave the way for the fifth-generation of wireless communication system. And to be able to design such complex and robust communication system it requires knowledge and understanding of the dynamics of space and time relative to frequencies. Given the limitations of millimeter-wave to blocking and poor signal attenuation compared to microwave signals it has been an area of focus for researches to explore the possible design modifications in the on-chip antenna in order to lessen the limitations.

The interest in chip antenna for millimeter-wave communication has been a trend in research studies within the past ten years. This has been further made into a global interest when the unlicensed utilization for the 60GHz radio frequency released by the United States. Other countries share the same unlicensed utilization of the 60GHz bandwidth with probably different allocations but the commonly shared 5GHz unlicensed bandwidth is unilateral. With this bandwidth available the transmission through wireless capabilities has exceeded whatever the current wireless communication system is capable of offering. And it has been determined that one of the key factors for such rapid change in the wireless communication field is the integration of on-chip antenna using CMOS circuits in different devices.

The interaction facilitated by the antenna with the ground plane and the silicon material that is placed within the circuit allowed easier dissipation of radiation around the antenna thus improving the radiation efficiency and gain. And with the promising impact that this will continue to lead, the use of chip antenna on millimeter-wave is highly anticipated as this would also revolutionized the traditional antenna which requires directional anchorage in order to facilitate communication in an expansive distance. With the modified high gain antenna and the CMOS technology high frequency antenna are a new addition to the millimeter-wave communication system.

Review of Literature

The Antenna on Chip or AoC and Antenna in Package (AiP) are among the solutions recently added to the integrated millimeter wave that is significant in wireless communications. In adherence to the standards set by the IIEE, application of 60-GHz in wireless communication is a welcome idea in terms of the advantages in communication and also in budget. Among the papers in the IIEE Transactions and Propagation, Zhang and Liu (Zhang & Liu, 2009) went into the detailed discussion of the Antenna on Chip as a possible solution on high permittivity and low resistivity and the efficiency of using AoC. In terms of using AoC, it is not yet that efficient according to their findings. It still reflected a relatively 12% lower efficiency which was attributed to the surface waves and loses on power. For AiP, there were also low-loss in the interconnection between the antenna and the chip. If the wire bonding will be feasible in terms of the 60-GHz band and the appropriate schemes are applied then AiP could possibly yield an efficiency rate that is 90% better. The issues with AoC and AiP have been linked to electromagnetic interference and with both the advantages and disadvantages presented the solutions highlights economic and electrical benefits and positive insights for system designers.

If millimeter wavelength antenna will be integrated in silicon technology it will result to a low cost system but will yield a higher rate of communication and sensory applications. In the study of Moussa, Torres, Nashef and Ngoya (Moussa, et al., 2013), an experiment was conducted wherein an antenna was patched to a silicon for millimeter wave using the technology QUBIC 4X Copper on NXP conductors. The results showed an increase in the efficiency of the antenna and the set up was also simulated using a 4GHz bandwidth.

The use of millimeter-wave chip-to-chip interconnections in multi-chip systems presents a lot of advances, challenges and future possibilities. This is the purpose of the paper (Ganguly, et al., 2018), which used the silicon technology in looking into the yield of multi-processor systems-on-chips. Through the study, the weakness of chips in yielding the expected efficiency had been attributed to the transformation of designs due to geometric modifications and the density of the products. As more modifications occur during manufacturing thus it may be expected that failures or lower efficiency will continue to increase, To resolve this matter, the proponents looked into possible solutions such as the disintegration of the of the chip into smaller chips or chiplets. This move is perceived to increase the rate of efficiency and reduce further the cost of manufacturing. In addition to this, functional flexibility and scalability of the chips will also enhance the memory module and interconnection fabric. The challenges were also considered in this strategy and one of the perceived challenges is the integration of the chiplets in systems where different voltages and frequencies are required. As the paper further explored the advantages and challenges, it was seen that energy consumption had been increased at the same time that bandwidth data was decrease throughout the communication from chip to chip. Given a multi-chip system integrated with a millimeter-wave wireless connection is made possible between several aspects of wireless communications design.

Chips on antenna are characterized through a method that uses millimeter-wave frequencies. In the study conducted by Payandeho and Abhari (2009), they used a dipole as a test antenna. This fabricated using a low-cost CMOS process with coplanar strips. Through the set-up the radiation pattern and gain of the antenna was simulated. The yield of the antenna was determined using a vector network analyzer and a probe station. This was also calibrated to simulate perfectly the effects of the probes and cables used for connection. The set-up was likewise tested to validate the results of the antenna from different angles where a good simulation had been determined at 55 GHz and 60 GHz.

Design and analysis of circularly polarized and dual-polarized on-chip micro strip antennas are popularly used for 60GHz wireless communication. This has been pointed out in the research conducted by Deen, Elhammied and Malhat (2016). Using the circularly polarized chip antenna, the antenna was made of circular aluminum patch composed of two overlapping circular slots that are powered through a transmission line. Among the noted characteristic of the antenna is the radiation of the circularly polarized (CP) chip which was analyzed using electromagnetic solvers. With the Cp chip, circular polarization was tried to function as a power transmitter. Meanwhile for the dual polarization chip was also used as an antenna at 60GHz and was tested as a chip receiver. The dual polarization chip has two poles which were designed to be isolated to serve as two on-chip receivers. Aside from investigating separately the level of radiation based on the distance of their isolation, the circularly polarized and dual polarized chip were also compared. The variables of comparison of the yield were transmission gain, transmission coefficient, and reflection coefficient.

The measurement of radiation pattern in the set-up of on-chip antenna is important in the operation of 60GHz non licensed bandwidth. According to Titz, Kyro, Luxey, Abdeljelil, Jacquemod and Vainikainen (2010), the radiation measurement is determined through the inverted F-antenna that is integrated in the CMOS that also demonstrates the capabilities of the set-up. The set-up in the study was comparable to the 20% efficiency at the 60GHz bandwidth. The study was also enthused by the global utilization of the 6GHz bandwidth especially in the field of Wireless Personal Area Network.

With the development of 60GHz trans receivers and antenna for increasing the efficiency of WiFi and 5G modules, millimeter waves proved to be useful in the wireless communication industry. Based on researches an IP trans receiver box was developed by to innovate designs using chips and antenna modules. Using 80GHz and 60GHz as the standard rate for data transmission for mobile devices and the access point the trans receiver chip on CMOS seemed to be the best solution (IMEC). The designs for millimeter wave antennas showed high potential for increasing the speed of communication. The bandwidth and speed are becoming the most important indicators on how connections and technology may be evaluated on their efficiency. While capacity had been answered by fiber based connections and optical technology it did not prove to be the same solution to answer the need for speed and cost. With the antenna as the main part of the solution, this was both a response on performance and cost efficiency. The antenna is the access point for dealing with the interference and distance in communication. The design of which determines the expanse of coverage and prevention of disturbance and interference during transmission. Antennas can likewise be designed to control the gain using the energy concentrated during the emission of beam and how this could also lead to better efficiency. Given the standards in the communication industry, the allowed power output of an antenna has been limited to the quality of narrower beam. Thus in order to provide lesser interference without breaking the standards the designs of the antenna needs to be efficient yet requires lower power output. As strict as the standards may be there is still a point of leniency where parabolic designed antennas are allowed to be used. These kinds of antenna designs are very common in telecommunications. These antennas serve well the purpose of satellite communication that connects distant linkages of radio communication. But the best designs in the antenna innovations would be the patch antenna which are made from low cost materials or commonly known as PCB. This are relatively smaller and thus saves a lot on costs. These patchy antennas are now used both to function as receiver and transmitter on the same level of frequency that allows sending and receiving of signals. And as RF Design (2017) asserts, the antennas are very significant in the multi point links that resolves both cost and strength of communications. And as a crucial component of the system efficiency of performance is tantamount to functionality and lower cost.

If measurement package for millimeter-wave antennas is to be considered, the accuracy of measurement on Antennas on Chip or AoC is one of the most challenging tasks. The inherent small size of the antenna itself has implications on the amount of substrate and the radiation efficiency of the antenna. As presented by Johannsen, Smolders and Reniers (2010) in their paper, the design for a low cost antenna could possibly resolve the above mentioned challenges. With the low cost design proposed the wire bonding that allows feasible interconnection is still part of the features of the antenna design. Thus with this inclusion, the feed line of the on-chip antenna is anchored to a PCB. The proper amount of distance from the chip helps in reducing the influence of the probe. After the radiation pattern were measured it was asserted that the AoCs size is enough to function under low radiation efficiency and the best method to complement the size of AoCs would be the radar-cross section or RCS.

The functional use of millimeter-wave leads to the aim of improving not just the capacity but also the efficiency of space and frequencies. Along with the concerns on security and privacy, the utilization of millimeter-wave frequencies allows also the limitation of range and widths that could be breached. There are several reasons why millimeter-wave frequencies are better used in communication, one of which is the flexibility in terms of spatial resolution. The antennas using small wavelengths also yields modest amount of beam width. The size of antenna used in millimeter-wave frequencies are practical solutions to integrating the antenna on PCB chip. And since there have not been a lot of innovations in this area of radio spectrum there is a possibility of gaining access on more bandwidth and more frequencies. Likewise the millimeter-wave frequencies can also be used again to function for short distances.

If the allocation in the United States will be used as a basis, in a 60GHz band there is an allowance of 5GHz bandwidth which is intended for Industrial, Scientific and Medical purposes but this is under unlicensed applications. The frequency bands under the millimeter-wave frequency allows services and products which caters to unlicensed short ranged but high speed links for WPAN and the wireless high definition of streaming videos.

Recent development and innovations in millimeter-wave that is aimed at reducing the cost in manufacturing was achieved through utilization of silicon based SiGe and CMOS technologies. With the two innovations the high frequency capacity has improved and the unity between the gain frequency and maximum frequency was reached. When silicon based technologies replaced the traditional GaAs, the millimeter-wave frequencies have been dominated by silicon technologies. Compared to CMOS the SiGe technology has more reliable designs and tools which are capable of meeting the needs of millimeter-wave. But then in terms of cost management CMOS technology is more advantageous than SiGe because SiGe makes use of digital band together with its analog and RF circuits. Thus under SiGe technology there is a need to use several chips unlike with CMOS where RF, digital and analog circuits could all be integrated in one.

In radio systems the on-chip antenna are important because the antenna and the system itself contribute to the efficiency of the system in removing the noise and reducing the front-end loss. Among the advantages of technologies is the silicon germanium (SiGe) and complementary metal oxide semiconductor (CMOS). Both have been very useful innovations because of their high integration capabilities and maturity. In order to radiate sufficient amount of input power and sustain the battery life it is necessary to have an efficient antenna. Recently, on-chip antenna has been taking the market like a storm because given its small size it only requires minimal costs to fabricate. With the miniature size of the antenna its configurations have also been compacted through the use of highly permeable materials. It may have been reduced in size but its function still retains the high radiation efficiency. The design and measurements of the antenna allows for high-permittivity dielectric resonator where the chip could be placed on a radio chip because of the h-slot aperture. To get a better idea on how the efficiency of the antenna could be improved, the passivation layer on the top slot of the antenna was removed. As noted by Nezhad-Ahmadi, Fakharzadeh, Biglarbegian and Safavi Naeni (2010), the simulation conducted had concretely shown an increase of 59% on the efficiency of the chip antenna. The results they got from the simulation have been verified and validated using the Wheeler method which indicated that the efficiency of the system went higher than 48%. And so far this has been the highest recorded measured efficiency rate on an on-chip antenna that was integrated in low-resistant silicon. This has shown proofs on the effects of low-resistivity silicon technologies on improving the radiation efficiency of on-chip antenna. With the results of the simulation conducted it was even proposed by the researchers that a configuration with high permittivity dielectric resonator be integrated using an H-slot antenna in the silicon circuit. The design of which was meant to maximize the efficiency of the antenna showing a gain in radiation by 1 DBi at 35GHz, plus a bandwidth of 4.15 GHz.

As the interest in using chip antenna for millimeter-wave communication systems is being taken seriously for the past decade, it is likewise looked into for further improving the efficiency of the antenna by integrating different technologies such as CMOS. In a study conducted by Gutierrez, Parrish and Rappaport (2009), a simulation study on on-chip antenna had been done in order to explore the possibility of resolving the reduction of interconnection losses and likewise reducing the wireless trans receiver costs without sacrificing the flexibility of the device where the antenna is embedded. The exploration went through several pitfalls and challenges particularly in designing the antenna and the circuit where it will be grounded. Finally the design and measurement of the antenna based on microwave and high frequency communication systems was finalized. In addition to the simulation, the study was also able to produce aside from the antenna design another way of measuring the results on the test apparatus which was presented as the RFIC system.

Definition of Terms

The antenna is a trans receiver device that facilitates the conversion of radio frequency from alternating current and vice versa. Antennas can both function as a transmitter and receiver of radio transmissions and is very important in the operations of radio equipment and recently it has also been significant in the wireless communication networks, mobile communication and satellite communication. In addition to this Technopedia (technopedia) further explains antenna in terms of its physical characteristics, an antenna refers to the arrangement of metallic conductors with an electrical connection to transmitters and receivers. It is composed of conductors which are creating the magnetic field in the circuit which helps the antenna to induce power and the oscillating fields generates the magnetic waves which enables signals to propagate within distances.

Chip Antennas or more technically referred as dielectric resonator antennas that create a wave of electrical field with a given frequency. According to the Electrical Engineering Stacker (Electriocal Engineering Stacker), the chip antenna may also be a cavity resonator which is defined geometrically to oscillate and thereby transmit and receives signals. The difference of the chip antenna to a typical antenna is the radiation pattern that is somehow similar to a dipole and instead of being hosted on a metal structure for its base or grounding the chip antenna is placed in a dielectric chip which has higher permittivity constant to enable easier dissipation of energy.

The millimeter wave referred to in this paper is also the same as the millimeter band that ranges from 30GHZ to 300GHz. This has been very interesting for researchers on fifth-generation wireless wave spectrum (Rouse). With the extremely high frequency or very high frequency that are being utilized in wireless communication networks and systems the millimeter wave is the underdeveloped aspect that could bring forth new innovations and discoveries that will bring products and services at a high-speed point. This will also bring wireless connection networks into a higher rate of data sharing up to 10Gbps.

Millimeter-wave communication is said to be the future for wireless communication. This millimeter-wave communication is the focal point of studies nowadays which aims to improve further the efficiency of delivery of signals from different point and at an expansive distance while reducing the manufacturing cost and fabrication process. Most of electronic devices now operates through wireless communication and wireless networks as just as important part of the daily tasks globally. The highly congested wireless communication network now brings researchers and developers to explore further possibilities of increasing the efficiency of the chip antenna that is now a common feature in handheld electronic devices. The foreseen increase in the efficiency of the chop antenna and the low cost fabrication process it comes with will definitely lead the wireless or millimeter-wave communication to a different level with speed and capacity as its main features.

Limitation of the Study

Just as advantages are foreseen to be achieved with the chip antenna, there are also restrictions and limitations that were encountered by developers and researchers through heir simulation activities. The said limitations are also parallel to the expected challenges to be encountered in using chip antenna for millimeter-wave communication. As Karim, Yang, and Shafique pointed out in their study, the on-chip antenna or OCA is becoming an essential part of the wireless system and it is continuously challenge by traditional or conventional off-chip antenna techniques. As the low cost manufacturing and increase efficiency are aimed in developing on-chip antenna the OCA seemed a promising innovation in wireless communication but it is not all advantages for this prospect. Since the on-chip antenna is being fabricated together with non metallic components the accuracy of measurement is one of the limitations of the antenna. This has been the biggest challenge too for the manufacturers to get the accurate and precise measure of the antenna which has been reduced to a miniature size. The size of the on-chip antenna is very different from the traditional off-chip one for one the size of the traditional cannot serve the function intended for the OCA. Thus innovations and techniques are required in order to make the correct set up for the OCA.

The OCA may have reduced the conventional antenna in terms of its size but it does not mean that the overall functionality has also been reduced. But when OCA had been reduced and embedded with silicon substrate the performance of the antenna is affected. The SiGes and CMOS technologies that are applied to on-chip antenna have been originally designed for large scale SoC integration, thus there is incompatibility in the lay out and the size of the antenna. There is also the interaction between the passives and the electromagnetic signals that are generated. If space is not properly planned and the position of the chip antenna is not carefully designed then it will not function as expected.

Aside from this there were also concerns on the fabrication errors and defects of the on-chip antennas. During the polishing stage the chip may cause a change in the thickness of the substrate that will likely affect the impedance of the antenna. The polished surface may also affect the generation of waves that may deteriorate the OCAs performance and efficiency. While in the slicing process the residual silicon substrate that serves as a buffer around the area of the IC may also affect adversely the OCA which was a result of the chip dicing process. Another limitation expected comes during the integration of the chip antenna in the circuit. The circuit itself acts as the RSS and in the fabrication process the dimensions of the chip antenna changes to fit into the cavity that may have changed during fabrication. As it was mentioned before the size of the antenna in this kind of circuit is crucial to its efficiency.

In terms of the frequency offset there is an anticipated 1GHz of reflection coefficient that was observed during the fabrication process which also alters the patch length. And when the frequency is shifted from 4GHz to 14GHz during simulation the reflection coefficient of the OCA has been relatively affected by the substrates’ weight and relative permitivity value. The production tolerance for the circuit where the chip antenna is integrated is also crucial consideration because during mass production it cannot be helped that there will be slight difference in the size of the antenna.

Another major factor of limitation is the absence of a mutually designed Electronic Design Automation that can assessed both the simulation set-up and the OCA with all its trans receiver components. This makes the OCA a crucial design because during the simulation process the other components used in the design were meant to function as trans receivers for IC design packages and not for chip antenna. The antenna design tools do not have a feature of built-in functionality that are aimed to check the design process. With the multiple alterations done during the simulation process it is unlikely to achieved the optimum results in a onetime set-up. It takes several alterations on the design and the IC tools until the desired results are achieved and the final designed is ready for fabrication and testing.

Conclusion

The on-chip antenna definitely gives an optimistic perspective on the direction of innovations in the field of wireless communication. The need for efficiency and bigger capacity is a response to the growing need of the users and to resolve the problems on data traffic due to congestion of data transmission with the present set up and kind of antenna being used. The innovations in technology show reduction of size and cost in production without sacrificing the efficiency of the product and service. This is a challenge but with all the interest in research and conduct of simulations it is not an impossible idea that at certain point the limitations that were encountered will also be resolved and thus usher the global community and the wireless network systems into the fifth-generation level of wireless communication.

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