PRINCIPLE OF CONSTRUCTION OF THE HIGH-FREQUENCY TRACUTE OF THE SOFTWARE-DEFINED RADIO SYSTEM

The paper considers the structural scheme of an "ideal" software-defined radio system, which involves the direct digitization of the received signal from the antenna, by connecting the receiver-transmitting antenna to the analog-digital converter, and the direct transmission of the transformed signal from the digital form to the analogue, by connecting the receiver-transmitter antenna to digital-to-analog converter. The general problem of using such a scheme is considered. The structure of a more perfect scheme of the transceiver of an "ideal" program-definable radio system, which has in its composition a reconfigurable bandpass filter-pre-selector, low noise amplifier, output power amplifier and low-pass filter, is presented. Broadband and multi-standard receiver is provided, since the functional circuit does not contain hardware narrow-band selective devices or devices depending on the carrier frequency and channel width. The sensitivity of the receiver depends on the noise factor of the linear part of the receiver, the channel width (band of the optimal filter), and the signal / noise ratio at the detector input. The noise factor of the linear part of the receiver is a hardware-dependent value and is determined, mainly, by the noise factor and the gain factor of the low noise amplifier. The selectivity on channels of false reception and on the adjacent channel can be realized by digital filtering. The main problem of the "ideal" software -definable radio system is considered. The task of constructing a software -definable radio system, the frequency characteristic of which will be independent of the parameters of a specific analog-digital converter, a digital-to-analog converter in conditions of work in a wide frequency range, is posed. with the provision of multi-standard, minimum distortion of information and the implementation of electromagnetic compatibility. In this case, the software-defined radio system must contain the minimum required hardware part, which is determined by the requirements for the characteristics of the software-determined radio system and the conditions for the implementation of electromagnetic compatibility. The method of solving the problem is considered, by constructing a high-frequency linear path of the receiver-transmitter. Thus, in order to construct a software-defined radio system, the frequency characteristic of which will be independent of the parameters of a particular analog-digital, digital-to-analog converter should be discarded from their parameters by constructing a linear high-frequency path that transmits the spectrum of the received signal at low frequencies and provides the necessary amplification and selectivity In the transmission mode, the modulated signal is formed in the signal processor (synthesizer of direct digital synthesis) at an intermediate frequency, converted to an analog form and converted into a mixer into a high-frequency modulated signal for transmission. Thus digitization and transformation of a digital signal into an analog is performed at a constant intermediate frequency, and work in a wide frequency range is realized by a high-frequency linear path.