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A method to adaptively calibrate a Hartley phasing-type single-sideband (SSB) modulator for obtaining high carrier and image suppressions is presented. The Hartley SSB modulator is extended by control elements to compensate for circuit nonidealities, a monitor circuit to measure the levels of the undesired residual carrier and image tones, and a digital controller. A direct search algorithm adjusts the control elements to maximize modulator performance. The effectiveness of the technique has been studied on an experimental SSB modulator. Carrier and image suppression ratios of 60 dB have been achieved over a carrier range from 1.40 to 2.35 GHz, a bandwidth of 51%.