Transmit Control

The TexoTransmitParams.frequency controls the transmit center frequency. However, only a few frequencies are actually valid. For example when using the 40 MHz transmit firmware (the old firmware), each pulse shape symbol (+, -, 0) corresponds to 25ns. Because the hardware can only control the pulse in 25ns resolution, this implies that only certain frequencies are achievable (see table below). The 80 MHz firmware (new firmware) reduces the pulse shape symbol duration to 12.5 ns, allowing for better frequency control. Below is a table of possible frequencies.

40 MHz Firmware

80 MHz Firmware


 * Since the highest sampling frequency is 40 MHz, there is no point in transmitting at 40 MHz.

The recommended set up is to use the 80 MHz software, and setting the transmit frequency to one of the frequencies shown above. By repeating the pulse pattern (ex. +-+-+-+-), the transmit signal spectrum can be narrowed and signal power be increased. Due to the transfer function of the transducer, which is highly biased in  the 2 – 5 MHz range, it may be desirable to increase the transmit frequency component of the signal by repetition of the pulse pattern.