Rhylee Suyom has hopped in three different worlds: the academe, the corporate, and the media. He enjoys being with nature and his family.
Spark Core with Chip Antenna
Chip Antenna for Millimeter Wave Communications
The study deals with the integration of chips with the technology in wave communications that address the concerns on the efficiency of performance of chip antennae in receiving and sending information through the different wireless communication systems. This presents the different advantages and possibilities that could be achieved using small chips but obtaining the optimum efficiency level. Millimeter-wave communications include the full utilization of millimeter-wave antennas, which are integrated for systems that work 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 the manufacturing process, precision, and material selection are crucial in the system's design. 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.
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 their 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 cost it entails while serving the same purpose. There are several more advantages to using chip antennas, including the layout. Due to its nature as a ground-dependent antenna, chip antennas must be placed in a well-proportioned and accurately sized plane to perform their resonant function.
The PCB is often used as the plane for the chip antenna; the way the components of the PCB are placed and adequately spaced from each affects the performance of the chip antenna. Even if it is placed on PCB with other components, the chip antenna still needs to be placed on the edge of the plane (PCB), separated from the other components, uninhibited by metallic components, and ground-free. The PCB should also be placed in a vertical position to enable the chip to broadcast in all possible directions.
The antenna aperture is also an important consideration. This affects the transmission efficiency; the materials' impedance should be balanced with the charge transmitted and the electromagnetic wave. When minimal energy is reflected, 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 protectors from environmental elements such as dust, moisture, shock vibration, and chemicals. Aside from handheld devices, chip antennas are widely used in telecommunications. This 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 their intensive use in telecommunications, chip antennas also comply with the Institute of Electrical and Electronics Engineers standards as reflected in the IIEE 802.11, the wireless networking standard.
Wave communication refers to the utilization of electromagnetic radiation to transmit information. This includes microwaves, infrared, radio waves, light, and radiation. Since the beginning of the 19th century, communication has taken rapid change. Morse code has been the means of communication used for long distances. But the use of Morse code requires flashes of light, and the visibility of signals is limited to a short distance only. Modern-day communication still involves codes and signals; however, its expanse has changed. Today, both analog and digital signals are very significant in communication. The signals sent through analog feature 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 transmission process, both analog and digital signals can catch unwanted signals that distort the original signal. Digital signals, the unwanted signal referred to as noise, can be cleaned up through regeneration. But for analog signals, the noise is likewise amplified when the original signal is amplified. This makes digital signals a better option than analog.
The application of millimeter waves in systems has significantly impacted communications and other fields. With the emergence of millimeter wave devices, communication has been further enhanced with smaller sizes yet capable of giving substantial 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 is handy given its low production cost.
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 communication and sensing application system. Together with two helpful fabrications process SiGe and CMOS, the antenna's radiation efficiency can be maximized. The reduction of the on-chip antenna in miniature size has made it possible to integrate it even into smaller electronic devices. Still, its size reduction has not been equal to having reduced its functionality. With more technologies and electronic devices powering up their functions in terms of capacity and efficiency, it is significant to achieve a breakthrough in the fabrication process where a low budget is required, as well as the on-chip antenna will be able to power up more.
The aim to power up the efficiency of the on-chip antenna is attributed to the increasing traffic in wireless data communication. The millimeter-wave communications are the most likely answer to this predicament that will pave the way for the fifth generation of wireless communication systems. And to design such, a complex and robust communication system requires knowledge and understanding of the dynamics of space and time relative to frequencies. Given the limitations of millimeter-wave blocking and poor signal attenuation compared to microwave signals, it has been an area of focus for researchers to explore the possible design modifications in the on-chip antenna to lessen the limitations.
The interest in chip antennae 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 of the 60GHz radio frequency released by the United States. Other countries share the exact 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 critical 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 placed within the circuit allowed easier radiation dissipation 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 revolutionize the traditional antenna, which requires directional anchorage to facilitate communication at an expansive distance. 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, the application of 60-GHz in wireless communication is a welcome idea regarding the advantages in communication and budget. Among the papers in the IIEE Transactions and Propagation, Zhang and Liu (Zhang & Liu 2009) discussed the Antenna on Chip as a possible solution for 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 attributed to the surface waves and loss of power. For AiP, there was also low loss in the interconnection between the antenna and the chip. If the wire bonding is feasible in terms of the 60-GHz band and the appropriate schemes are applied, then AiP could yield an efficiency rate that is 90% better. The issues with AoC and AiP have been linked to electromagnetic interference. With both the advantages and disadvantages presented, the solutions highlight economic and electrical benefits and positive insights for system designers.
If a millimeter wavelength antenna is integrated into silicon technology, it will produce a low-cost system but yield a higher communication and sensory applications rate. In the study of Moussa, Torres, Nashef, and Nagoya (Moussa, et al., 2013), an experiment was conducted wherein an antenna was patched to silicon for a millimeter wave using the technology QUBIC 4X Copper on NXP conductors. The results showed an increase in the antenna's efficiency, and the setup 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 paper's purpose (Ganguly et al., 2018), which uses silicon technology to look 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. The proponents looked into possible solutions to resolve this matter, such as disintegrating the chip into more minor chips or chipsets. This move is perceived to increase the rate of efficiency and further reduce the cost of manufacturing. In addition, the chips' functional flexibility and scalability 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 increased at the same time that bandwidth data was decreased throughout the communication from chip to chip. A multi-chip system integrated with a millimeter-wave wireless connection is made possible between several aspects of wireless communications design.
Chips on antennae 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 is fabricated using a low-cost CMOS process with coplanar strips. The antenna's radiation pattern and gain were simulated through the setup. The yield of the antenna was determined using a vector network analyzer and a probe station. This was also calibrated to simulate the effects of the probes and cables used for the 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 microstrip antennas are popular for 60GHz wireless communication. This has been pointed out in the research by Deen, Elhammied, and Malhat (2016). The circularly polarized chip antenna was made of a circular aluminum patch composed of two overlapping circular slots 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, 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 designed to be isolated to serve as two on-chip receivers. Aside from separately investigating the radiation level based on the distance of their isolation, the circularly polarized and dual-polarized chips were also compared. The variables of comparison of the yield were transmission gain, transmission coefficient, and reflection coefficient.
The measurement of the radiation pattern in the set-up of an on-chip antenna is essential in the operation of 60GHz nonlicensed bandwidth. According to Titz, Kyro, Luxey, Abdeljelil, Jacquemod, and Vainikainen (2010), the radiation measurement is determined through the inverted F-antenna integrated into 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 Wireless Personal Area Networks.
With the development of 60GHz trans receivers and antennae for increasing the efficiency of WiFi and 5G modules, millimeter waves proved helpful in the wireless communication industry. Based on research, an IP trans receiver box was developed 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 of the trans receiver chip on CMOS seemed to be the best solution (IMEC). The designs for millimeter wave antennas showed high potential for increasing communication speed. The bandwidth and speed are becoming the most important indicators of how connections and technology may be evaluated on efficiency. While fiber-based connections and optical technology had answered capacity, it was not the exact solution to answer the need for speed and cost. With the antenna as the central part of the solution, this was a response to performance and cost efficiency. The antenna is the access point for dealing with interference and distance in communication. The design 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 the 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 a narrower beam. Thus, to provide lesser interference without breaking the standards, the antenna designs need to be efficient yet require 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 the purpose of satellite communication that connects distant linkages of radio communication. But the best design in the antenna innovations would be the patch antenna made from low-cost materials commonly known as PCB. These are relatively smaller and thus save a lot on costs. These patchy antennas are now used both to function as receivers and transmitters 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 resolve both the cost and strength of communications. And as a crucial component of the system efficiency of performance is tantamount to functionality and lower cost.
If the 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 antenna's radiation efficiency. As presented by Johannsen, Smolders, and Reniers (2010) in their paper, the design of a low-cost antenna could 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 reduce the probe's influence. After the radiation pattern was measured, it was asserted that the AOCs size is enough to function under low radiation efficiency. 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 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 also allows 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 yield a modest amount of beam width. The antenna size used in millimeter-wave frequencies is a practical solution to integrating the antenna on a PCB chip. And since there have not been a lot of innovations in this area of the radio spectrum, there is a possibility of gaining access to more bandwidth and frequencies. Likewise, the millimeter-wave frequencies can also be used again to function for short distances.
Suppose the allocation in the United States will be used as a basis in a 60GHz band. In that case, 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 allow services and products which cater to unlicensed short ranged but high-speed links for WPAN and wireless high-definition streaming videos.
Recent development and innovations in millimeter-wave that is aimed at reducing the cost of manufacturing were achieved through the utilization of silicon-based SiGe and CMOS technologies. The high-frequency capacity has improved with the two innovations, and the unity between the gain frequency and maximum frequency was reached. When silicon-based technologies replaced the traditional GaAs, the millimeter-wave frequencies were dominated by silicon technologies. Compared to CMOS, the SiGe technology has more reliable designs and tools capable of meeting millimeter-wave needs. But then, in terms of cost management, CMOS technology is more advantageous than SiGe because it uses digital bands 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 into one.
In radio systems, the on-chip antenna is vital because it and the system contribute to the system's efficiency in removing the noise and reducing the front-end loss. Among the advantages of technologies are silicon germanium (SiGe) and complementary metal oxide semiconductor (CMOS). Both have been beneficial innovations because of their high integration capabilities and maturity. To radiate a sufficient amount of input power and sustain the battery life, it is necessary to have an efficient antenna. Recently, the 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 highly permeable materials. It may have been reduced in size, but its function retains high radiation efficiency. The design and measurements of the antenna allow for a 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 of how the antenna's efficiency 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% in 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 system's efficiency went higher than 48%. And so far, this has been the highest measured efficiency rate on an on-chip antenna integrated into low-resistant silicon. This has shown proof of the effects of low-resistivity silicon technologies on improving the radiation efficiency of the on-chip antenna. With the simulation results, the researchers even proposed that a configuration with high permittivity dielectric resonator be integrated using an H-slot antenna in the silicon circuit. The design was meant to maximize the antenna's efficiency, showing a gain in radiation by 1 DBi at 35GHz, plus a bandwidth of 4.15 GHz.
As the interest in using chip antennae for millimeter-wave communication systems has been taken seriously for the past decade, it is likewise looked into to improve the antenna's efficiency by integrating different technologies such as CMOS. In a study conducted by Gutierrez, Parrish, and Rappaport (2009), a simulation study on an on-chip antenna was done 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 underwent 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 were 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 receivers of radio transmissions and are very important in the operations of radio equipment. Recently, it has also been significant in wireless, mobile, and satellite communication. In addition, Technopedia (technopedia) further explains an 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 creating the magnetic field in the circuit, which helps the antenna to induce power. The oscillating fields generate magnetic waves, which enable signals to propagate within distances.
Chip Antennas or more technically referred to as dielectric resonator antennas, create a wave of the electrical field with a given frequency. According to the Electrical Engineering Stacker (Electrical Engineering Stacker), the chip antenna may also be a cavity resonator defined geometrically to oscillate and thereby transmit and receive signals. The difference between the chip antenna to a typical antenna is the radiation pattern that is somehow similar to a dipole. Instead of being hosted on a metal structure for its base or grounding, the chip antenna is placed in a dielectric chip with higher permittivity constant to enable easier energy dissipation.
The millimeter wave referred to in this paper is the same as the millimeter band, which ranges from 30GHZ to 300GHz. This has interested researchers on the fifth-generation wireless wave spectrum (Rouse). With the extremely high or very high frequency being utilized in wireless communication networks and systems, the millimeter wave is the underdeveloped aspect that could bring forth innovations and discoveries that will bring products and services at a high-speed point. This will also bring wireless connection networks to a higher rate of data sharing, up to 10Gbps.
Millimeter-wave communication is said to be the future of wireless communication. This millimeter-wave communication is the focal point of studies nowadays, which aims to improve further the efficiency of the delivery of signals from a different point and at an expansive distance while reducing the manufacturing cost and fabrication process. Most electronic devices now operate through wireless communication and wireless networks as just as important part of 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 standard 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 lead wireless or millimeter-wave communication to a different level with speed and capacity as its main features.
Limitations of the Study
Just as advantages are foreseen to be achieved with the chip antenna, there are also restrictions and limitations that developers and researchers encounter through their simulation activities. The limitations also parallel the expected challenges in using chip antennae 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 traditional off-chip antenna techniques continuously challenge it. As low-cost manufacturing and increased efficiency are aimed at developing on-chip antennae, the OCA seemed a promising innovation in wireless communication. Still, it is not all advantages for this prospect. Since the on-chip antenna is being fabricated with non-metallic components, measurement accuracy is one of the limitations of the antenna. This has been the biggest challenge for the manufacturers to get accurate and precise measurements 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 to make the correct setup for the OCA.
The OCA may have reduced the conventional antenna size, but it does not mean that the overall functionality has also been reduced. But the antenna's performance is affected when OCA has been reduced and embedded with a silicon substrate. The SiGes and CMOS technologies applied to on-chip antennae have been initially designed for large-scale SoC integration. Thus, there is an incompatibility between the layout and the antenna size. There is also the interaction between the passives and the generated electromagnetic signals. If space is not planned correctly and the position of the chip antenna is not carefully designed, then it will not function as expected.
Aside from this, there were concerns about 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 adversely affect the OCA resulting from the chip dicing process. Another expected limitation is during the chip antenna integration in the circuit. The circuit acts as the RSS, and in the fabrication process, the dimensions of the chip antenna change to fit into the cavity that may have changed during fabrication. As mentioned before, the antenna size in this kind of circuit is crucial to its efficiency.
In terms of the frequency offset, an anticipated 1GHz of reflection coefficient was observed during the fabrication process, which also alters the patch length. And when the frequency is shifted from 4GHz to 14GHz during the simulation, the reflection coefficient of the OCA is relatively affected by the substrates’ weight and relative permittivity 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 a slight difference in the size of the antenna.
Another major limiting factor is the absence of a mutually designed Electronic Design Automation that can assess both the simulation setup 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 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 is aimed at checking the design process. With the multiple alterations done during the simulation, it is unlikely to achieve the optimum results in a one-time set-up. It takes several alterations to the design and the IC tools until the desired results are achieved, and the final design is ready for fabrication and testing.
The on-chip antenna 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 setup and kind of antenna being used. Technological innovations show a 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 a 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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