A method of operation of an energy transmitter adapted to transmit energy to a particular energy harvester (104-1) using radiative coupling, comprising: • for each time period (TP i ) of a plurality of time periods ({TP i } i=0,1,...,I-1 ) where I is a positive integer that is greater than or equal to 2: o for each time slot (TS i,j ) of one or more time slots ({TS i,j } j=0,1,...,J-1 ) where J is a positive integer that is greater than or equal to 1 for the time period (TP i ): ▪ transmitting , during the time slot (TS i,j ) of the time period (TP i ) on a frequency f mod(i,2) , a radio frequency signal (S T (i,j)) that is modulated with a signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i,2) is a first frequency f 0 for even values of i including i=0 and is a second frequency f 1 for odd values of i; and o attempting (518-520), during the time period (TP i ), to receive, from the particular energy harvester (104-1) on a frequency f mod(i+1,2) , a radio frequency signal (S R (i)) that is modulated with the signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i+1,2) is the second frequency f 1 for even values of i including i=0 and is the first frequency f 0 for odd values of i. • for each time period (TP i ) of a plurality of time periods ({TP i } i=0,1,...,I-1 ) where I is a positive integer that is greater than or equal to 2: o for each time slot (TS i,j ) of one or more time slots ({TS i,j } j=0,1,...,J-1 ) where J is a positive integer that is greater than or equal to 1 for the time period (TP i ): ▪ transmitting , during the time slot (TS i,j ) of the time period (TP i ) on a frequency f mod(i,2) , a radio frequency signal (S T (i,j)) that is modulated with a signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i,2) is a first frequency f 0 for even values of i including i=0 and is a second frequency f 1 for odd values of i; and o attempting (518-520), during the time period (TP i ), to receive, from the particular energy harvester (104-1) on a frequency f mod(i+1,2) , a radio frequency signal (S R (i)) that is modulated with the signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i+1,2) is the second frequency f 1 for even values of i including i=0 and is the first frequency f 0 for odd values of i. o for each time slot (TS i,j ) of one or more time slots ({TS i,j } j=0,1,...,J-1 ) where J is a positive integer that is greater than or equal to 1 for the time period (TP i ): ▪ transmitting , during the time slot (TS i,j ) of the time period (TP i ) on a frequency f mod(i,2) , a radio frequency signal (S T (i,j)) that is modulated with a signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i,2) is a first frequency f 0 for even values of i including i=0 and is a second frequency f 1 for odd values of i; and ▪ transmitting , during the time slot (TS i,j ) of the time period (TP i ) on a frequency f mod(i,2) , a radio frequency signal (S T (i,j)) that is modulated with a signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i,2) is a first frequency f 0 for even values of i including i=0 and is a second frequency f 1 for odd values of i; and o attempting (518-520), during the time period (TP i ), to receive, from the particular energy harvester (104-1) on a frequency f mod(i+1,2) , a radio frequency signal (S R (i)) that is modulated with the signature of the particular energy harvester (104-1), wherein mod(*) is the modulo-2 operator such that f mod(i+1,2) is the second frequency f 1 for even values of i including i=0 and is the first frequency f 0 for odd values of i. <EOS>