HF SDR TRANSCEIVER (HST)

HF SDR Transceiver is a high performance, low IF transceiver specifically designed for modern HF software defined radios for long range sky-wave communication. HST can be interfaced with a baseband processing card, through serial USB interface, to complete HF software radio hardware. Any commercial off-the-shelf card with DSP, FPGA or even a single board computer can be used as processing platform. One of the main advantages of HST is that it can be interfaced, through USB, with desktop computers or laptops for rapid prototyping of HF radios. Unlike conventional HF radios, it allows up to 48 KHz of input channel bandwidth that could be very useful for building high data rate HF radios by using modulation techniques like OFDM which can handle large delay spread of HF channels. HST has onboard state of art direct digital synthesis chip (DDS) by Analog Devices for carrier generation across the entire HF band from 3 to 30 MHz. It offers high frequency agility and sub hertz of tuning resolution that is beneficial for building HF radios with frequency hopping and automatic link establishment capabilities. Furthermore it can be used for HF cognitive radio applications which require the scanning of the entire band. HST uses Tayloe detector for down conversion which is ultra low noise, high performance, low IF product detector and preamplifier. Because of its direct conversion architecture, carrier image frequency related issues will be avoided. The advantage of having low IF instead of zero IF is that only one analog to digital converter (ADC) is needed at the receiver. Furthermore the IQ imbalance problem that is common in direct conversion receivers will not be an issue anymore. High adjacent channel rejection can be achieved by the digital FIR filters after ADC sampling in the digital domain. HST transmitter has output power of 3 watts across the entire HF band when operated with a properly matched antenna. An external amplifier will be required for long range skyway operation.