A method of operating a near-field charging pad, comprising: at a near-field charging pad that includes one or more processors and a plurality of power-transfer zones that each respectively includes at least one power-transferring element and a signature-signal receiving circuit: sending, by a respective power-transferring element included in a first power-transfer zone of the plurality of power-transfer zones, a plurality of test power transmission signals with first values for a first set of transmission characteristics, wherein the test power transmission signals are radio frequency, RF, power transmission signals; in conjunction with sending each of the plurality of test power transmission signals, detecting, using the signature-signal receiving circuit, respective amounts of reflected power at the first power-transfer zone; and based at least in part on the respective amounts of reflected power, determining, for each power-transfer zone of the plurality of power-transfer zones, whether (i) an authorized wireless power receiver and/or (ii) an object other than a wireless power receiver is present at a respective surface of the near-field charging pad that is adjacent to each of the plurality of power-transfer zones; wherein: the one or more processors of the near-field charging pad are in communication with a data source that includes the one or more predefined signature signals; and the method further comprises: in conjunction with the sending of the plurality of test power transmission signals by the respective power-transferring element included in the first power-transfer zone of the plurality of power zones, sending a further respective plurality of test power transmission signals by respective power transferring elements included in each power-transfer zone of the plurality of power-transfer zones; and detecting, using respective signature-signal receiving circuit included in each respective power-transfer zone of the plurality of power-transfer zones, respective amounts of reflected power at each of the plurality of power-transfer zones. sending, by a respective power-transferring element included in a first power-transfer zone of the plurality of power-transfer zones, a plurality of test power transmission signals with first values for a first set of transmission characteristics, wherein the test power transmission signals are radio frequency, RF, power transmission signals; in conjunction with sending each of the plurality of test power transmission signals, detecting, using the signature-signal receiving circuit, respective amounts of reflected power at the first power-transfer zone; and based at least in part on the respective amounts of reflected power, determining, for each power-transfer zone of the plurality of power-transfer zones, whether (i) an authorized wireless power receiver and/or (ii) an object other than a wireless power receiver is present at a respective surface of the near-field charging pad that is adjacent to each of the plurality of power-transfer zones; wherein: the one or more processors of the near-field charging pad are in communication with a data source that includes the one or more predefined signature signals; and the method further comprises: in conjunction with the sending of the plurality of test power transmission signals by the respective power-transferring element included in the first power-transfer zone of the plurality of power zones, sending a further respective plurality of test power transmission signals by respective power transferring elements included in each power-transfer zone of the plurality of power-transfer zones; and detecting, using respective signature-signal receiving circuit included in each respective power-transfer zone of the plurality of power-transfer zones, respective amounts of reflected power at each of the plurality of power-transfer zones. the one or more processors of the near-field charging pad are in communication with a data source that includes the one or more predefined signature signals; and the method further comprises: in conjunction with the sending of the plurality of test power transmission signals by the respective power-transferring element included in the first power-transfer zone of the plurality of power zones, sending a further respective plurality of test power transmission signals by respective power transferring elements included in each power-transfer zone of the plurality of power-transfer zones; and detecting, using respective signature-signal receiving circuit included in each respective power-transfer zone of the plurality of power-transfer zones, respective amounts of reflected power at each of the plurality of power-transfer zones. in conjunction with the sending of the plurality of test power transmission signals by the respective power-transferring element included in the first power-transfer zone of the plurality of power zones, sending a further respective plurality of test power transmission signals by respective power transferring elements included in each power-transfer zone of the plurality of power-transfer zones; and detecting, using respective signature-signal receiving circuit included in each respective power-transfer zone of the plurality of power-transfer zones, respective amounts of reflected power at each of the plurality of power-transfer zones.