Heterodyne Multifrequency Receiver for MST

Recently, a real-time and portable 2-D microwave imaging system operating at 24 GHz, incorporating modulation schemes similar to modulated scatterer technique and synthetic aperture radar (SAR) imaging technique, was designed using a heterodyne receiver with superior performance compared with a homodyne receiver. Multifrequency SAR images have the added advantage of providing for: 1) coherent averaging of image data over frequency and hence increasing system signal-to-noise ratio (SNR) and 2) enable volumetric (3-D) image production. This letter describes modifications to this receiver for enabling multifrequency operation through phase uncertainty (PU) analysis. These modifications show significant reduction in PU, thereby allowing the coherent addition of data necessary for SAR image formation with higher overall SNR.