Nuand Research Blog

We hear where everyone is coming from with the lack of the HF and VHF bands.  Let me take some time to explain a little bit about why that is the case.

The main RF transceiver, the LimeMicro LMS6002D which makes all of this possible, is designed for wide bandwidth communication – specifically 1.5MHz to 28MHz bandwidths.  For lower frequencies, especially in the VHF or HF band, this poses a problem for radios that are meant to be sensitive to adjacent channels since the typical bandwidth in that area is anywhere from 3kHz to 25kHz.  Simply put, around 60 channels can fit within the smallest filter bandwidth of 1.5MHz.

For LimeMicro, it didn’t make sense to manufacture the device to cover the lower frequency bands since the adjacent channel rejection wouldn’t be very good.  Moreover, getting a 1.5MHz allocation in VHF is near impossible.

So, while the bladeRF natively supports 300MHz to 3.8GHz, there are options available for HF and VHF reception.

First, the LMS6002D brings the analog ADC/DAC pins out and are available to connect to any 50Ohm source. This means that a bladeRF can act as a direct conduit to a 40MHz ADC or DAC. There is no need to use the LNA’s or mixers in the RF transceiver if you don’t want to use them.

Furthermore, we are working on designing an up/down converter to bring 50MHz – 300MHz up to the native tuning frequency of the bladeRF.  When the design is completed, we’ll present it to the community in the form of an expansion board.  One of the biggest issues with working in the VHF band is the massive number of FM radio stations located very close to people who are trying to listen to signals which can extend down to -120dBm or lower. With wide bandwidth comes the potential to listen to wide noise! We need to be careful to not saturate our front ends with bogus signals and provide a terrible radio experience.

We are excited and extremely grateful for all the support and positive comments we’ve seen from this kickstarter campaign. We want to try to make this as accessible to everyone as possible, so, as always, comments and suggestions are welcome.

We have officially Kickstarter-ed our project, check it out!

http://www.kickstarter.com/projects/1085541682/bladerf-usb-30-software-defined-radio

In other exciting news, the bladeRF was used as a wireless UART bridge by an early access tester!

http://www.youtube.com/watch?v=iBSd3QOUfzA

We have spent the last couple of weeks further developing the platform and talking with part distributors. All of our parts at this point are in stock, and those that aren’t have reasonable lead times. We are taking these steps to ensure that if we do go to mass production there will be no hiccups.

As for some other exciting news, we recently got our hands on the first of several pieces of test equipment we will need to develop our intended examples and expansion boards. Having this sort of equipment at home is much more convenient than constantly scheduling lab time weeks in advance!

As a sanity check, we ran a conducted RF chirp on the bladeRF at 500MHz to see its maximum bandwidth capabilities. In previous experiments, we have seen about 28MHz of occupied bandwidth, which this run seems to agree with.

The spectrum analyzer was used to capture a spectrum of spurs over the bladeRF’s frequency range on the RX side. Besides the occasional spur, the noise floor of the device is surprisingly good.

Here is the same sort of spectrum capture but on the TX side, and again the spectrum looks pretty clear with the exception of a few spurs which appear to be related to the main 38.4MHz clock. Spurs this low on the TX side really don’t matter since they are so far down below the TX output power of the LMS that they will no be able to significantly interfere with any transmissions or even influence