If anyone is morbidly interested a more technical explanation of CA with diagrams is
here
Interesting point is that this is generally only a trick that can pulled off in good coverage areas. Since 3G/UMTS days cells don't just operate in fixed frequencies per connection they use a single shared frequency and spread spectrum techniques that started in military use. Downside of this is if you want to aggregate frequencies you can only do that across cells, so it only works where your device can reach more than one.
But this is an aspect where a device will always win over a phone. What limits your connection is the not the power of the radio in the cell but the power of the radio in your device. Any phone has to limit the power to a certain peak and average level because it's assumed to be physically held next to your body for much of it's time. Devices such as routers or laptops have much higher limits so can hold connections further out and do more with them.
A key thing to look out for when buying a more router like device is it's LTE Category. Theoretically they go quite high but for practical purposes you'll find 2 common ones on the market. Cat 4 devices have a single spread spectrum band radio with 2 antenna and can achieve speeds of 150Mbps downstream and 50Mbps upstream, Cat 6 devices have 2 spread spectrum band radios with 2 antenna and can achieve 300Mbps downstream and 50Mbps upstream.
It's worth noting that to do this they need support on the network side too - higher categories use more of a cells resources for one connection so it can serve less people so, unsurprisingly, the ability to do so tends to only come with the higher priced contracts. For similar reasons more rural cells may not offer the ability even if you've paid for it if they need the bandwidth for other connections.
If you're buying a LTE Router than at least make sure it's Cat 4. All the ones I use are Cat 4 and to be honest I never hit the limit on them even doing remote work. If you want future proofing and peak performance get a Cat 6 devices - but to make the most of it ensure the contract on the SIM allows you to use the higher speeds. There are Cat 12 and 16 devices appearing now but in general they're not going to make much difference they'll just cost you more.
The Netgear Nighthawk pretty much implements every possible option making it massively capable but with a price tag to match as it has an extensive radio layer. It is however regarded as one of the most capable and bombproof mobile devices out there (without getting into the industrial ones) and yes I do wish I had one
