Posts Tagged‘antenna’

New Antenna Design Could Vastly Improve Mars Rover Communications.

The way we get most of the scientific data back from the rovers we currently have on Mars is through an indirect method. Currently there are four probes orbiting Mars (Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter and MAVEN) all of which contain communications relays, able to receive data from the rovers and then retransmit it back to Earth. This has significant advantages, mostly being that the orbiters have longer periods with which to communicate with Earth. Whilst all the rovers have their own direct connections back to Earth they’re quite limited, usually several orders of magnitude slower. Whilst current rovers won’t have their communication links improved for future missions having a better direct to Earth link could prove valuable, something which researchers at the University of California, Los Angeles (UCLA) have started to develop.

santos-ucla-mars-attenna

The design is an interesting one essentially being a flat panel of phased antenna array elements using a novel construction. The reasoning behind the design was that future Mars rover missions, specifically looking towards the Mars 2020 mission, would have constraints around how big of an antenna it could carry. Taking this into account, along with the other constraint that NASA typically uses X-band for deep space communications like this, the researchers came up with the design to maximise the gain of the antenna. The result is this flat, phased array design which, when tested in a prototype 4 x 4 array, closely matched their simulated performance metrics.

With so many orbiters around Mars it might seem like a better direct to Earth communications relay wouldn’t be useful however there’s no guarantees that those relays will always be available. Currently mission support for most of those orbiters is slated to end in the near future with the furthest one out slated for decommissioning in 2024 (MAVEN). Since there’s a potential new rover slated to land sometime in 2020, and since we know how long these things can last once they’ve landed, having better on board communications might become crucial to the ongoing success of the mission. Indeed should any of the other rovers still be functioning at that time the new rover may have to take on board the relay responsibilities and that would demand a much better antenna design.

There’s still more research to be done with this particular prototype, namely scaling it up from its current 4 x 4 design to the ultimate 16 x 16 panel. Should the design prove to scale as expected then there’s every chance that you might see an antenna based on this design flying with an orbiter in the near future. I’m definitely keen to see how this progresses as, whilst it might have the singular goal of improving direct to Earth communications currently, the insights gleaned from this design could lead to better designs for all future deep space craft.

iPhone 4 Antenna Issues: Let’s Get Some Things Straight.

I’ve steered clear of saying anything to do with the iPhone 4 antenna issue that’s been making the rounds for the past month orso mostly because I believe it’s almost a complete non-story. It seems pretty obvious that they made the choice to put the antenna on the outside for aesthetic reasons (although there’s not a whole lot of other places it could of gone really) and unfortunately the kinds of testing done wouldn’t pick up on this issue. Still there seems to be as many people ready to leap on Apple for any issue as there are lining up to buy their products but those two groups never seemed to have a big cross section as they do today. The problem I have however is not so much whether or not there is a problem, more that a stream of fud has begun to come out of various media outlets and PR firms that confuses the issue at hand rather than solving the problem outright.

For those of you not in the know the iPhone 4 has it’s antenna laid bare to the world in the form of the metal bands that wrap around the outside of the handset. Due to the size constraints of the handset there’s really no where else to put them as the handset is quite thin and the additional electronics that Apple plugged into the new handset doesn’t leave any room for your traditional internal antenna. Like most modern handsets it actually has 3 separate antennas, with one being used for things like Bluetooth/Wireless/GPS and the other two for 2G/3G cellular communications. The separation of the cellular and other antennas is done because the antennas are tuned to a specific range of frequencies and the two cellular antennas are done to improve reception. Realistically the only difference between the iPhone 4’s antenna and any other phone is the fact that you can see and touch it, and that’s where the problems are starting to arise.

You see nearly every phone in the market today has their antennas on the inside of the phone, usually at the bottom of the handset to reduce the radiation levels. They are put inside the handset to make sure that nothing can interfere with them directly like say keys in your pocket or your hand. The iPhone 4’s antenna is completely exposed to the world with those sleek bits of aluminium being electrically conductive. Your hand is also a good conductor and when your hand comes into contact with it you actually form part of a circuit with your phone. This wouldn’t be too much of a problem since electricity takes the path of least resistance (and your hand has a higher resistance than the metal) but the fatal flaw in Apple’s design is the gap that is bridged when the phone is held in the left hand.

When you bridge this gap you are completing a circuit between the two cellular antennas that the phone has. This has the effect of detuning the antennas and significantly reducing their performance and reducing the amount of usable signal available to the phone. This is why the problem can be replicated by both holding it normally or simply bridging the gap between the two antennas. The solution is quite simple the antennas simply need to be isolated from the conductive surface of your hands which is why the bumper cases were so effective in solving the problem.

Jobs has taken the unfortunate route of saying that all phones suffer from this issue and unfortunately that’s just not the case.

Now before any of you go ahead and link me to videos of it happening on other handsets let me explain why that’s not the issue that’s affecting the iPhone 4. You see all phones will suffer attenuation in signal when you put your hands over the top of their antenna. That’s pure physics at work since the signal has to pass through your hand which is actually quite good at absorbing radiation. It then follows that you could “death grip” any phone by just finding where it’s antenna is and covering that place up. Hell check any phone manual and they’ll probably show you where it is and tell you not to cover it up.

However that’s a different problem to the antenna being detuned by you touching it. When your signal drops due to you holding your phone that’s not you detuning your antenna, that’s just the signal being dampened by the barrier of your hand. You can’t detune the antenna when you aren’t able to make electrical contact with it and that’s where those videos that Jobs showed at the press conference were misleading. The problem they have isn’t one of attenuation due to the human hand, it’s one of the antenna being thrown out of whack electrically.

There’s no doubt that Apple handled this badly and in their classic style they’ve attempted to muddle the issue at hand whilst making themselves look like the good guys. Granted their move of giving every iPhone 4 owner a free bumper is a good move and I applaud them for doing so. However their handling of it by trying to bring everyone down and spreading fud about the issue hasn’t done them any favours in my book, nor in anyone else’s as far as I can tell. Hopefully I’ve cleared it up for you so that you understand the difference between the death grip on the iPhone 4 and any other handset out there, rather than the crap that I’ve seen spouted over this issue.