V.A. Makovij

Common drawback of all known systems maintain the signal level on the analog-digital converter input is presence of transients in the received signals caused by changes in the transmission gain of the analog channel. Moreover, these transients in the received signal appear, even if the signal has a sufficient frequency separation with dynamic noise. To overcome this limitation of maintenance systems of input level of the analog-digital converter, systems of automatic adjustment of the sensitivity (AAS) have been offered. Key difference AAS from other systems of regulation is that AAS realizes not changes, as redistribution of analog-digital path (ADP) gain between the analog and digital domain at preservation invariable the overall transmission gain. One of the most important dynamic parameters characterizing possibility of a radio receiver to carry out signal reception in the presence of high amplitude noise, the dynamic band on blocking is. For the results of laboratory researches allowed to draw conclusions about the selectivity of equipment under actual operation conditions, it is offered to use three kinds of blocking signals at measurements: -The single frequency not modulated harmonic signal; -The dual-frequency not modulated biharmonic signal with the same amplitude of harmonic components; -Band noise with uniform spectral density in the band and the distribution of the instantaneous values of the normal distribution. Radio receiver without AAS The dynamic range of programmable radio receivers (PR) on blocking in the absence of AAS and restrictions in the ADC during the real-live to 12.3 dB lower, than that measured at the harmonic blocking signal. Measurements with a biharmonic blocking signal allow to mount dependence of a dynamic range on blocking from blocking signal peak factor at much more simple compared to the signal of the third kind measurements. Radio receiver with AAS on peak value of a signal The benefit in the value of the dynamic range, obtained by the introduction of AAS with the double peak detector, will make дБ. Typically, =3 дБ. Thus, the susceptibility on blocking PR with AAS, keeps strong dependence from blocking signal peak factor. Radio receiver with AAS on an average angle of restriction The most deficiencies of AAS with the peak detector can be eliminated by switching to regulation by the average angle of restriction. For the analysis of transit of clipped waveforms through the analog-digital converter the concept of average angle of restriction is introduced. These results suggest, that the benefit on blocking PR with AAS by the average angle of restriction over PR with AAS on peak value increases at increase blocking signal peak factor. Sensitivity adjustment by criterion of increase SNR The blocking factor can be not be the sole criterion for generating a control signal for the AAS system. If the value of the dynamic range at blocking by a signal with normal distribution of instantaneous values is not a priority at the design of the ADP, when you select the allowable limit of the average angle to guide admissible integral noise level added to the received signal at restriction. It is necessary to distinguish between two main functional modes of AAS with stabilizing of an average angle of restriction. These modes correspond to the two criteria of a choice of as much as possible admissible average angle of restriction formulated above. The first mode is applicable in those ADP which sampling frequency is close to the minimum required by the theorem of Nyquist. In this mode the value of the average angle of restriction shall be selected from the condition to ensure the interference power constraints at the proper noise ADC. The important feature of the offered AAS at an average angle of restriction is possibility to quickly change its properties over a wide range depending on actual conditions of reception by changing the threshold. This adjustment system allows to very stringent requirements for a new generation of radio - cognitive radio. The method of increasing the dynamic range of blocking based on gain redistribution between an analog and digital part of a programmable radio receiver is offered. For the first time the analytical ratios describing dependences of noise and a signal in-band reception from a degree of restriction at any from blocking signal are received. The parameter «average angle of restriction» is offered. Analytical expressions for calculation the dynamic range on blocking of the radio receiver with system AAS are received. Advantages of offered system AAS before previously known systems regulating the voltage at the input of the analog-digital converter are shown.