This work presents a dual-band, dual-mode backscatter uplink leveraging shared hardware that combines a custom DQPSK mode at 900 MHz and a SSB BLE-compatible mode at 2.4 GHz. The DQPSK mode provides a data rate of 6.25 Mbps with a measured power consumption of 75 uW at the backscatter modulator, yielding a modulator efficiency of 12.4 pJ/bit. The SSB BLE-compatible mode provides a 1.0 Mbps data rate while consuming 198 uW at the backscatter modulator, yielding a modulator efficiency of 198 pJ/bit, which is >50X more efficient than most off-the-shelf BLE transmitters. The sideband rejection ratio was measured to be 10 dB, improving the in-channel signal strength and reducing out-of-channel emissions. This system provides real-time neural data uplink across both the 900 MHz and 2.4 GHz ISM bands, which to the best of our knowledge is unique in the literature on wireless BCIs. The dual-band compatibility of the backscatter front-end provides end-users and researchers the ability to leverage frequency diversity depending on the communication channel, offering experimental flexibility that could be advantageous in commercial applications outside of neural engineering as well.