 Hello and welcome to the antenna implementation guide. My name is Miroslav and I will walk you through the session. I don't think you will be bored, so let's start. Due to expansion of virus devices and appliances today, a proper antenna design is becoming more important. Virus devices are widely used and can be found in any kind of application. This guideline is going to give you a general insight for implementing PCB antennas in to BLE or generally 2.4 GHz design. Although I have no doubt that there are experienced engineers among you who can do so. Another possible way is to use a ceramic antenna for which similar rules can apply as stated in this guideline. In part 1, we will grab the information how to implement antenna correctly and what to avoid to not lose a performance. We will focus on metallic object and environment. Today it is not very convenient to have an external antenna or an antenna connected to the enclosure. Therefore, the antenna began to be an integral part of the PCB and you must create the conditions for its proper functioning all the more. It is necessary to become familiar with this component. The antenna is a key component that can simply better or degrade the RF link Thus when designing or implementing the antenna several important aspects need to be acquired. Here are several basic aspects we need to consider. The permittivity or if you want the altriconstant of laminate is a critical design parameter for PCB trace antennas. Variation can cause severe detuning of narrowband antennas, especially if the stackup of various layers is used. At frequencies in GHz bands a low loss laminate should be considered. Unlike chip antennas PCB trace antennas cannot be copied to another device expecting a good performance. If implementing the PCB antenna you should always consider a custom design or at least adjustment for your conditions. The reason for will be explained further. When the PCB trace antenna is placed on the motherboard it is in fact a 2D structure in the same plane as the ground. The amount of surface area for the antenna is then very limited than because of lack of the third dimension. It can lead to less performance than other antenna type. PCB antenna can be matched to 50 ohm and in most cases they are. Due to external conditions an antenna needs to be fine tuned as it is often out of dedicated band. To have good performance it is necessary to adjust the antenna by matching network that is in front of the antenna port. It is a kind of resonance circuit or a filter that enable more power to get into the antenna from a feeder. In RF we call this as impedance matching. Antenna matching components allow compensating uncertainties related to PCB material and other external impacts as mechanical objects nearby. This also help to decrease an amount of prototype rounds due to simply adjusting lamp components instead of adjusting antenna shape. Let's talk about inverted F-antena. The inverted F-antena is a kind of basic monopole antenna that uses a shorted arm to define an impedance. This antenna needs a sufficient ground plane to operate. This is not only a difference between such kind of antenna and dipole ones but from design point of view it is a significant factor. The ground plane is a mirror for the antenna and it is integral part of antenna. Radiation efficiency depends on the size of the board or metal planes. There exists a limit where antenna becomes not operating and getting loss and efficiency. Therefore when considering about antenna look at a PCB to evaluate antenna performance and select the right type and location for the antenna. Many antennas of this kind needs a clearance. This is an area under the antenna where no ground, no metal is present. This clearance must be kept in all PCB layers. The size of clearance is designed in such a way to help antenna to radiate effectively and to not impact its performance so never interfere to this reserved space. Performance of the antenna depends on dielectric material and its thickness, especially a resonance frequency and return loss is affected. For frequencies of our concern it means 2.4 GHz a common FR-4 material is used as a cost-effective solution. Reducing antenna length is possible as this is quite common task to make the board smaller. Therefore the antenna is in folded form. It preserves a resonance frequency but it can have smaller efficiency especially if this parameter is not taken into account when designing it. During this session I will introduce a couple of examples to explain consequences of various implementations. All of them will be presented on planar inverted f-antina, designed in full 3D electromagnetic simulation tool. The first example is the clear antenna design. All the others will be affected by various matters. And I will show you how the parameters change. So let's explain the basic one. The highlighted area is the clearance for antenna. We already know this should be out of metal objects. The antenna is located at the edge of PCB. And this area creates ground plane for antenna. Such size is enough for keeping efficiency. Here is so called return loss parameter depicted. This is a basic parameter showing how the antenna is adjusted. The left hand side representation is a magnitude plot and we are trying to get the graph as deep as possible and at the same time to preserve enough bandwidth. Looking up by difference of outer markers. A representation on the right hand side is smith chart that depicts the same but in complex numbers. In this case we try to get the plot between markers close to center of smith chart. As we already stated a bandwidth is measured as a difference of two crossings with horizontal line of appropriate region loss magnitude level. Resonance frequency corresponds to the mineral level of the plot. These two dimensional plots are the basic radiation pattern cuts. It is an envelope of the three dimensional far field in certain angle. These can be in absolute numbers expressing some of the horizontal and vertical components of the field or only in particle component. In the particle pattern cut we can show the angle and appropriate value of antenna directivity. This telling us again or directivity of antenna from various angles depending on if efficiency is included or not. A 3D far field for this type of antenna is an omnidirectional pattern. This plot is almost optimal far field we can get from planar inverted f antenna. We can determine three basic radiation pattern cuts. Let's mark them in the picture. The plane YZ specifies the red circle here. The plot shows an envelope of 3D far field. The plot is 8 shaped. The XZ plane specifies the green circle here. So the envelope creates a nice circle. The XY plane is made by blue circle. We can see here it is a cross section which plot is number 8 shape. Let's discuss more about the antenna implementation. Considering planar inverted f antenna we have to endure a couple of meters. The outline of the antenna is given by its clearance. No other components are allowed here as those could impact performance of antenna. There are designed certain spaces around the antenna, mainly on the right and on the left ground edge. These are important from radiation pattern point of view as this impacts a shape of the far field. The distances must be kept if you want to preserve performance of the antenna. As to keep it out of any metal side strips. You never know if these metal edges were taken into account when designing the antenna or if they can be removed as they impact radiation pattern. But if the PIFA antenna is designed with such side ground areas and they will not properly fit into PCB, don't use them. Always it is feasible to assess if this is necessary to keep them or better to remove them. The clearance is located from the main arm of antenna toward the feeder and or let's say desirable ground. This distance affects efficiency and bandwidth. Keep this distance as it is from design. Antenna trace width depends on used FF4 material the electric constant and its thickness. In the case of composed stack up it is even more complicated but the antenna should be adjustable by matching network and its length even so. This example is about modification of a clearance size. The antenna shape is a bit closer to a ground plane so this can be a case of wrong implementation of antenna non-respecting needed space on PCB. The situation is expressed in the picture on the right hand side. The red frame portion was moved toward ground plane so the clearance became smaller. The ground plane is preserved in size. Let's look at the return loss changes. Here are the return loss results in already well-known representations. This can be expressed in VSWR as well. A resonance is slightly shifted downwards and magnitude of return loss is much worse. This should be possible fine-tuned by matching network to get back to the center of the desired band although not in all cases this may happen. Resonance is decreased by 2 dBs in this particular case so it is only 63% of original value. It is predictable if the antenna would be even closer to ground plane would be worsened all the more. You should always consider the spacings of the antenna shape to the ground plane and it is always necessary to tune it in the environment where the antenna will be operated. The results visible from return loss are, resonance frequency is shifted down, worse magnitude of return loss and reduction of efficiency. Radiation pattern didn't change. Even in the 3D far field is not visible any change. This radiation pattern shape is preserved. Included directivity however gain is decreased by smaller efficiency. A radiation pattern is preserved only small changes are visible as the character of the antenna was preserved. We will make a short detour to explain matching network. Antenna port is at the edge of the ground plane where the antenna is connected with a feeder. Relocation of antenna port also means relocation of the antenna within PCB thus you will get different antenna behavior. Features of antenna is related to its placement. The important integral part of antenna is matching network. You can adjust the impedance of an antenna to the feeder with matching network. It allows as much power as possible to the antenna and subsequently radiates the power out. Matching network is a kind of RF filter so this is often made by reactance components inductors and capacitors. For BLE only discrete components are used. These parts should have to be high Q and low ESR utilizes. A planar components aren't feasible. The point is to get an antenna impedance that is almost never 50 ohm to impedance of the feeder. Better to say it matches the complex impedance of antenna to complex conjugated impedance seen at the end of the feeder. These circuits can be pi or t structure or even simpler shaped and they can serve as an additional RF filter as well. It can be used for suppression of harmonics. The matching network is adjusted after fitting all the components on board in operating conditions so inside the housing. Namely the antenna is affected by all these matters thus its impedance is changed then therefore you would fine tune the impedance in this step. As we already talked about the antenna is affected by all these matters therefore its impedance is impacted. An issue could be with significant difference between impedances of the feeder versus the antenna and then the quality factor of matching network becomes higher thus it makes a bandwidth smaller. Difficult case is a metallic enclosure. Generally a metal object is heavy NMA4 antenna. Metals make it impermeable for radiated waves and if nearby the antenna it impacts its impedance. In result it may change a character of antenna. The first case occurs while metallic object is far from antenna in far field. The waves are reflected and make the region behind the metallic object partially in shadow. The second case occurs when the object is near field or reactance field. The object is then becoming a part of antenna so the antenna can be completely detuned. From this perspective it can be a metallic enclosure for water meters, gas meters etc. In special cases if the PCB with antenna is enclosed only partially inside the housing then you can use the open part for radiation. Suitable is patch antenna or similar one that do not radiate backwards a lot. It must be well designed in terms of opening in housing. First is to use an external antenna but it is not usable everywhere or the solution makes it expensive. In cases where antennas are close to metallic objects it needs to be well adjusted by matching network. This example shows the performance of an antenna whose implementation in this PCB is not correct. The antenna seems to be sunk in the ground plane. This is represented by the side strips. So the antenna shape itself has not changed but the side strips change its character and features. Although they increase the ground plane size a bit they have a major effect on antenna tuning. The strips caused a shift of resonance frequency downwards significantly. The antenna became very mismatched. Efficiency has dropped considerably by 70 dBs in this case. The desired return loss in band is completely out of resonance. The ESWR in demanded band is really out of the good numbers. Fundamental resonance is at lower frequency than it should be and further resonance is appearing higher. This state should not be easily fined tuned by matching network only the layout change is the option. The results from return loss. The antenna is completely mismatched and further resonance is appearing there. There is significant efficiency loss that makes a radiation almost impossible. It has also consequences to radiation pattern. The antenna became more directive and its omnidirectional character is lost. The far field change can be seen from the images of pattern cuts. There is increased maximum directivity number. It is some 1 dB more. However, the efficiency is so miserable that antenna is useless. Moreover, it doesn't have the typical apple shape. It shouldn't be a problem if the other parameters weren't so bad. As a conclusion for pattern shape, the antenna became a bit more directive and its omnidirectional character is lost. Antenna is useless for transmitting a signal as efficiency is very low. This experiment concerns to antenna that is placed perpendicular to another ground plane. This may be the case of the Bluetooth module that is connected to the motherboard with headers. In general, a larger ground plane has a more positive effect on the antenna, especially to the efficiency. But this may not always be the case. Often, it changes a far field in terms of directivity. Let's look at the results. It shows up a similar result as detuning the antenna with distance to a ground plane. The return loss is somewhere between 2 and 4 dBs in magnitude in the desired band, and a resonance is out of band as well. It corresponds to some 4 to 7 in VSWR. Efficiency is decreased by 3 dBs. The antenna is tuned clever. At the same time, the return loss has worsened in magnitude. The antenna would need to be set up with a matching network. A new insight, there is a hint for further resonance at higher frequencies. The results for return loss are the antenna is mismatched a bit, there is further resonance appearing, and higher efficiency loss is present that corresponds to some 50% of original value. Why the efficiency is smaller? On the one hand, the role plays the mismatched and second apparently a location of the antenna versus the added motherboard. What is new in the effect on the radiation pattern? This is simply a consequence of the large ground plane which makes the antenna highly directional. If you place an antenna above ground plane, you basically get a similar far field as depicted. A shape depends on the mutual placement and the distance of the antenna and the added motherboard. Antenna pattern has changed a lot and it is more omnidirectional and worsen efficiency is not visible on the directivity but on a far field plot of antenna gain. Now we will deal with small size PCB. The next category is small PCB where installation of antenna and other electronics is task task. A reason is hardly reachable and enough counterpoise for the antenna. This is related to monopole antenna type. If the small PCB isn't a part of larger unit, then a significant decrease of efficiency will be a reality. The result is a range reduction. You have to realize that it overlaps to power consumption. Let's consider a flowing. If you would like to increase a range, you have to increase the output power or directivity of antenna. Even used antenna type is hardly made directional so the output power change is only the option then. The further parameter is an efficiency of antenna. You can manage it by increasing a size of antenna end or PCB size. But when you are going to design a large antenna on a stand-alone small board, this could be an issue as well because large antenna cannot be sufficiently mirrored in a small PCB ground plane. The mistake could be the adjustment of the size of the PCB board itself, which forms the ground for the antenna. This can have a very important consequence. Let's see what kind. So we reduced one dimension of the PCB by 20 mm. Next we will show what properties an antenna designed for a different PCB size will get. On contrary the case, with enough size of ground plane, this is about the reduction of ground plane. It is visible on resonance frequency that is going upwards now, but the written loss is becoming considerably worse in the desired band as same for larger ground plane. VSWR is on the wrong numbers so the antenna will redate badly. We are interested in the behavior of the antenna in the Bluetooth band where there is a significant reduction in efficiency. The antenna has almost lost the ability to radiate the delivered power. The results are the antenna is mismatched a lot so it has worse written loss. Low efficiency is present corresponding to some 20% of original value. The antenna must be placed on proper size of the board, otherwise it cannot radiate due to small so-called counterpoise. At first glance no changes are noticeable, perhaps only to blur the minimum in the characteristic. On closer view we can see a reduction in antenna directivity which we have not observed under any other external conditions. So definitely avoid this, as the matching network will no longer help the antenna. This is about small counterpoise which is the issue. The antenna pattern shape has changed a bit and antenna becomes more omnidirectional. But the antenna gain is very small so the radiation power will be very decreased. Thank you for watching the first part of the video focusing on general information and on metallic objects and environment. In the second part we are going to introduce you to the cases concerning dielectric and the human body effects on the antenna parameters. We will see you next time. Take care, bye.