Method for real time control of transmit chain for software radios
View Patent ↗In a communications or jamming system, accurate timing for the control of the frequency, amplitude, modulation type, pulse repetition rate or other transmit characteristics is achieved for the transmission of digitally processed packetized signals through the use of standard non-realtime off-the-shelf components for the digital processing and a realtime interface which reads transmit chain headers and, with the assistance of a precise time reference, assures that the transmit chain is configured in time to transmit the packets. Note that the realtime interface assures nanosecond timing accuracy regardless of timing errors introduced by the off-the-shelf components used in upstream digital processing.
1. A method for the precision control of a software radio employing a transmit chain in the transmission of packetized data such that the transmit chain is configured in real time to transmit a realtime analog signal from the packet data, comprising the steps of:
generating packets of data to create realtime analog signals having components characterized by a periodic waveform, the packets having a header including a time stamp indicating when a packet is to be sent, the header describing the characteristics that the transmit chain is to have when transmitting a packet, the transmit chain generating a realtime analog signal having periodic waveform components timed to nanosecond accuracies greater than an accuracy associated with frame length, the transmit chain characteristics taken from the group consisting of frequency, amplitude and modulation type; and,
configuring the transmit chain in realtime responsive to the header describing the characteristics that the transmit chain is to have, whereby non-realtime processing can be accomplished by off-the-shelf components having non-realtime accuracies, the accuracy of the timing of the transmit chain being sufficient to generate and transmit the analog signals corresponding to the packet with nanosecond accuracies.
2. The method of claim 1 , wherein a packet is transmitted at the precise time corresponding to the associated time stamp thereof, and wherein the configuring step includes configuring the transmit chain sufficiently prior to the precise time that the analog signal is to be transmitted to permit transmission of the analog signal corresponding to the packet at the precise time to permit precision on the fly reconfiguring of the transmit chain.
3. A method for the realtime control of a software radio employing a transmit chain for the transmission of realtime analog signals having components characterized by a periodic waveform generated from packetized data, comprising the steps of:
generating the packets of data with off-the-shelf components having non-realtime accuracies; and,
providing realtime control signals having nanosecond accuracies for configuring the transmit chain, the transmit chain and associated transmitted realtime analog signal components characterized by a periodic waveform, the signal components being generated to nanosecond accuracies such that the components of the transmitted signal are generated with accuracies greater than an accuracy associated with frame length, the transmit chain characteristics taken from the group consisting of frequency, amplitude and modulator type, whereby on the fly changes in the transmit chain can be realized without the necessity of providing all realtime components, thus to minimize the cost of controlling the transmit chain, the packets being provided with headers specifying the transmit chain characteristic for the transmission of a packet, and the realtime control signals being generated responsive to the header specifying the transmit chain characteristic for a packet.
4. The method of claim 3 , wherein the packets are buffered prior to transmission and wherein the buffered headers are read at a precise time in relation to the time at which the packet is to be transmitted by the transmit chain, thus to establish nanosecond accuracy for the analog signal components.
5. The method of claim 4 , wherein the precise time is established by a realtime clock.
6. The method of claim 5 , wherein the realtime clock has the nanosecond accuracy.
7. The method of claim 5 , wherein the realtime clock includes a GPS receiver for referencing the realtime clock to Greenwich Mean Time.