Phase comparator at 2.5 GHz

Images of biological objects can be obtained by exploration with microwaves. Reconstitution of the image takes place by distribution in phase and in amplitude of the diffracted field on a portion of a spherical surface. Obtaining these parameters requires a precision phase comparator at a working frequency of 2.5 GHz. The comparator consists of an arrangement of four couplers of 3 dB, one phase shifter of 90¿¿ followed by filtering and detection circuits such that one obtains: (¿¿l¿¿¿¿2) = arctan V1/V2, where V1 and V2 are measured directly. The realised system permits a phase measurement with an error of less than 5¿¿ at the nominal frequency (2.5 GHz) for levels of power between ¿¿10 dBm and ¿¿30 dBm.