When it was reported that the new iPhone 4 was making use of the metal band around the phone for the “antenna” and if you held the iPhone wrong the signal disappeared or got weaker, there as a flurry of articles about this method of antenna placement. Soon after, Apple (AAPL) announced that part of the problem was that their software formula for determining signal strength—i.e., showing how many “bars” of signal was available—was in error and that in reality the signal strength was really lower than that being shown.  What I have not seen discussed is the entire issue of the antenna, and its placement on wireless devices. There are a number of interwoven issues here, all of which can help explain the problems encountered. First, the weak link in any wireless or radio system is the antenna, its effectiveness and its location. If you watch TV with an outside antenna and you disconnect the antenna from the TV set you get no reception; if the antenna on your car breaks you get no AM or FM reception. This is because these systems are designed with the understanding that an external antenna is needed.In analog cellular days every phone had an external antenna, this gave the device better range when it was communicating with the cell sites. Then we switched to digital but analog was still operational and the antennas were still external. Today, our wireless network operators have built out many more cell sites—AT&T (T) and Verizon (VZ) each have more than 40,000 sites to cover the United States.  Still, we don’t have good coverage inside buildings or in areas where the nearest cell site is at a distance. But since coverage is many times better than it was earlier, the handset and network operators decided to hide the antennas inside the devices to make them more appealing, and make them easier to carry. This has had the effect of making them less sensitive than earlier devices that did use external antennas.  There is a reason that you will find external antennas mounted on police, Fire, and other vehicles that make use of two-way radio. You will also find there are external antennas on family radio walkie-talkies and hand-held two way radios used by first responders and others. Nextel (S) made use of external antennas on their phones—and some of them still have external antennas—all of this is to give the customer the ability to receive and send wireless information when in lower signal areas.  Special Offer: Paul McWilliams bougth Intel at $12 in late 2008 and urged Next Inning members to load up on CREE below $17. What now? Click here for instant access to portfolio moves in Next Inning Technology Research.  Next is the fact that we are not talking about a single antenna for the iPhone nor for any wireless device. Antennas have to be matched to the frequency on which they operate.  The match has to be such that as much power is transferred from the transmitter to the antenna as possible. A mismatched antenna can result in poor radio coverage, heat build-up inside of the radio and, therefore, shorter life for the device. Antenna experts are very good at designing antennas to be as efficient as possible, but again in the confines of a handheld device there are trade-offs that must be made.  Radio waves are absorbed by our bodies, by walls, and even by vegetation. Some of you might have experienced different performance of your wireless devices in the same location in the winter than in the summer. This is because leaves, and even pine needles can soak up a radio signal and cause the overall system to degrade during the spring and summer.  Also, since radio waves sometimes arrive at your device not directly from the radio tower but rather by being bounced off a building or hill, these signals may be much lower in signal strength than if you had a clear line of sight view to the cell site.  All of these factors affect the performance of our wireless devices, but we need to add yet another perimeter to all of this: Today’s wireless devices need multiple antennas in them. A typical “world phone” operates in 4 to 5 different portions of the spectrum from 800 MHz through 2.1 GHz or higher.  Then there is the antenna needed for Bluetooth, and Wi-Fi if it is built in, and one for the GPS receiver, and if you have mobile TV capabilities built in there will be another antenna to receive, say the MediaFLO TV signals on 700 MHz. Soon, Verizon first and then AT&T and others will be adding the 700 MHz band to these devices and the number of antennas needed inside a wireless device will increase again, and most LTE systems will make use of two antennas in each wireless device to increase both the coverage and the data speeds.As I mentioned antenna design engineers have gotten very good at what they do but since each antenna must be electrically matched to the transmitter and receivers, it has to have certain characteristics that differ from the antenna for a different portion of the spectrum.  Today the engineers have been able to design fewer antennas into these devices by making one antenna do the work of several, but there are limitations about what can be done. All of this also means that any company that is designing and building devices that does not have access to engineers who really understand the antenna systems required is going to have a problem building a device that works as well as someone else’s device with a better antenna system.  Some of you might remember when Wi-Fi was first being built into notebook computers, my company, as well as many others, ran tests to determine range and speed (the weaker the radio signal the less data speed), and found big differences. Today all of these notebooks offer about the same type of coverage but in those days there was a huge difference.  What we found is that the computer companies who hired or brought in antenna experts had products which performed better than those who thought that you could just build an antenna and put it inside a notebook. Not only is the length of the antenna important but where it is placed inside a device is just as critical. It is radiating radio signals so it could interfere with the devices receiver, or some of the radio waves could be absorbed by other components and even more can be absorbed by the placement of a hand over the portion of the phone where the antennas are located.  As you can see the entire issue of antenna design and placement is critical to the performance of a wireless device. What Apple was trying to accomplish was two-fold. First they were trying to gain room inside the iPhone 4 so that they could make it thinner and have a larger battery, and secondly, they were trying to get the antenna(s) outside of the device, just as you would by using an external antenna sticking out the top of the device. I have not tested an iPhone 4 in our lab, but will be doing so once they resolve the software signal strength issue, but it is easy to know why they were caught off guard by the complaints about poor coverage.  There is one more variable that needs to be taken into account. When your car radio receives an AM or FM broadband signal that is all that is happening—it is receiving the signal. However, depending upon the technology your network operator is deploying it is possible that your phone is both transmitting and receiving at the same time.  This creates additional problems in design because the same antenna that is “listening” for a signal is also transmitting a signal on a different portion of the spectrum at the same time. Unless these systems are designed carefully, the transmitted signal can cause noise in the receiver, making it not nearly as sensitive.  Perhaps the entire issue of receiver sensitivity deserves a mention about now. Receivers are designed to hear signals that are received by their associated antenna and then process these signals. However, if there is a lot of noise (interference) on the channel the receiver is listening to, it cannot detect the intended signal because it is covered by noise. Also, different types of receivers have different degrees of sensitivity.  To better understand this, visualize a single grain of sand. Hold that grain of sand between two you’re your fingers and you will hardly feel it, however if you put it into your eye it will feel like a boulder! In this case your eye is a more sensitive “receiver” than your fingertips. The more sensitive a receiver the better coverage the customer will experience.  Normally when testing these devices the first tests are done in a controlled environment where other radio signals are blocked (call a screen room), and the device is mounted in a test fixture, not held in someone’s hand. The final tests, just as the product is ready for market, are the field tests and it is very possible that the differences in coverage were not noticed because they were being tested as standalone devices and NOT against other devices in the same area by the same person.Once again, it is important to understand that antenna design needs to be carefully done and even then it is part science and part art, and the antenna experts who work on these devices clearly understand the art part.  The transfer of radio signals to and from the antenna and the radio receiver and transmitters, and the efficiency with which that is accomplished determines how well the device will perform. For voice the difference will be a clean completed call or a noisy dropped call, for data services the better the signal strength the higher the data rate you will obtain in both directions. If you device is not designed properly your results will be worse than someone standing next to you with a different and better designed device.  I am not saying the that the iPhone 4 was not designed properly, but it does appear to me that their goal was to provide for better performance and a better data experience for their customers, and if the “fix” is to put a rubberized case around it to keep hands from touching the metal portion of the phone than that is a simple enough “fix.” If this type of a fix does not prove to be workable, ie, there is something more involved, then I am sure that Apple and the network operators will figure it out and come up with a fix.  The point of this commentary was not to beat up Apple for what might have been a design mistake but rather to point out to our readers exactly how complex the entire issue of antenna design and placement is, and to also point out that the antenna is the weakest link between our wireless device and the cell sites, and that I am not talking about a single antenna here, but rather multiple antennas that all need to be the best that they can be, stuffed inside and smallest possible space without interfering with each other or the radio and computer components inside the same box.  It is truly amazing to me that we have engineers that possess the knowledge and the skills necessary to make all of these variables work together, and I suspect that moving forward we are going to find more examples where new attempts at antenna placement might be tried, some of which will work and some of which will fail, no matter how good a computer model you build to “prove out” the performance of these antennas, until you put them on or in the device and turn it on, you are not 100% sure what the results are going to be—that is the art on top of the science that is so important.
The iPhone 4 antenna issue may have a simple fix but technology that goes into smartphone antennas is anything but simple.