ABOUT THE POSSIBILITIES OF PRACTICAL USE OF A SIGNAL WITH A PHASE TRUTCH

Abstract

The possibilities of practical use of the signal by the modified phase manipulation and ±π/2 phase inserts with subsequent return to the phase are considered. It is shown that such a signal should consist of a support part, which is a segment of the radio carrier and the actual phase inset, which in phase differs from the carrier phase by π/2 or -π/2, depending on what is transmitted in this code position «1» or «0». The variant is considered when the supporting part contains 9 periods of oscillations of the carrier, and the phase inset ‑ 1 period. It is shown that with this ratio the carrier signal is easily distinguished, and the useful information signal of the phase inset after decoding has the form of a short pulse. A block diagram of the codec of the system using such a signal is proposed, and its virtual model is developed in the Simulink environment.The codec operation algorithm consists of a sample of pre-prepared FM signal fragments from a static memory containing discrete values of one period (Bd), the shape of which is expressed by the function cos(ωt).The article shows that all testing is conveniently carried out in a digital format, for which the standard resistive DAC R2R is used at the output of which an analog signal is formed. Next, the signal from the FM enters the low-pass filter, the parameters of which must ensure the fulfillment of Kotelnikov's theorem.In order to form a “phase inset”, the sequence of data selection from memory should be changed by the time of the tenth signal period, followed by restoration. Those. if at the beginning of the tenth period of the carrier signal to change the reading of data from the memory by ¼ of the period ahead, and at the end of the tenth period to restore the normal course of reading, a “phase inset” takes place, the nature of which is described by the function cos(ωt-π/2). If, at the beginning of the tenth period, to change the course of reading data from RAM by ¾ of the period ahead, this will lead to the formation of a “phase inset”, the shape of which is described by the function cos(ωt+π/2). In this regard, the counter circuit CT3 in the structure of the codec should provide the ability to pre-set the value of the account.