I am planning to implement a frequency hopping spread spectrum transmitter and receiver in GNU Radio. In my project, the bandwidth of the message signal is around 200 kHz and the maximum frequency hopping interval is around 80 MHz. On the other hand, the USRP that I use can only support 40 MSample/sec which can not cover all the frequency bands of interest. Therefore, the use of a numerically controlled oscillator (NCO) is not applicable. Instead (as far as I consider), I should manipulate the carrier frequency of the local oscillator in the RF stage for such high carrier-frequency jumps.
My questions are:
- Is it possible to change the carrier frequency of the local oscillator instantaneously?
- How can I provide the synchronization of the receiver? (I am assuming that the transmitter sends a sync-word over a predetermined frequency. When the receiver detects the sync-word, the receiver changes the local oscillator frequency according to the hopping rule)