| 摘要 |
A method of imaging within an absorptive object comprising: placing transmit and receive antennas in close proximity to a surface of said object; transmitting electromagnetic pulses from the transmit antenna into the object; and receiving a receive signal at the receive antenna simultaneously with the transmit antenna transmitting said pulses; wherein the transmitting and receiving comprises the following steps: a) setting a threshold level for the receive signal strength; b) transmitting one or more pulses; c) comparing the receive signal for said one or more pulses with the threshold level; d) changing the threshold level; e) repeating steps b), c) and optionally d) one or more times. This arrangement can operate at extremely high speed due to the absence of any slow multi-bit ADCs. Coupled radar applications require very high sampling rates and a high dynamic range is required if both the strong direct path signal and the weaker signal from depth are both to be received simultaneously. The use of a comparator as effectively a 1-bit ADC quantises the incoming signal into two levels; it can operate at high speed and thus provide the time resolution required for signal processing. The comparison threshold is adjustable, i.e. the quantisation level is adjustable. This provides the high dynamic range that makes coupled radar applications possible. |
