TAILIEUCHUNG - Jamingcg 5794

JAMMING TO SIGNAL (J/S) RATIO - CONSTANT GAIN [LINEAR] JAMMING | JAMMING TO SIGNAL J S RATIO - CONSTANT GAIN LINEAR JAMMING JAMMING TO SIGNAL J S RATIO MONOSTATIC J Gja Rx GjGja Tx 8 Gja Rx GjGja Tx C 2 ratio form S 4bf 4bof2 Gja RX The Gain of the jammer receive antenna Gj The gain of the jammer Gja Tx The Gain of the jammer transmit antenna or 10log J S 10log Gja Rx 10logGj 10logGja Tx - 10log 4bo 82 or if simplified radar equations developed in previous sections are used 10log J S 10log Gja Rx 10logGj 10logGja Tx -Go dB Keep 8 and o in same units. Note 8 c f Target gain factor Go 10log o 20log f1 K2 in dB K2 Values dB RCS o fi inMHz fa in GHz units K 2 K 2 m2 ft2 JAMMING TO SIGNAL J S RATIO BISTATIC Same as the monostatic case except Go will be different since RCS o varies with aspect angle. Since the jammer on the target is amplifying the received radar signal before transmitting it back to the radar both J and S experience the two way range loss. Figure 1 shows that the range for both the signal and constant gain jamming have a slope that is 40 dB per decade. Once the jammer output reaches maximum power that power is constant and the jamming slope changes to 20 dB per decade since it is only a function of one way space loss and the J S equations for constant power saturated jamming must be used. Normally the constant gain linear region of a repeater jammer occurs only at large distances from the radar and the constant power saturated region is reached rapidly as the target approaches the radar. When a constant gain jammer is involved it SELF SCREENING ESCORT JAMMING Figure 1. Sample Constant Gain Constant Power Graph may be necessary to plot jamming twice - once using J from the constant power saturated equation 1 in Section 4-7 and once using the constant gain linear equation 4 as in the example shown in Figure 1. CONSTANT GAIN SELF PROTECTION DECM Most jammers have a constant power output - that is they always transmit the maximum available power of the transmitter excepting desired ECM .

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