A novel extended dynamic range synchronous detector for AM shortwave upconversion receivers

In an upconversion receiver based on a high intermediate frequency (IF), only a limited IF selectivity can be obtained. A synchronous detector is presented which is intended to provide the required additional selectivity. Generally, this type of selectivity is limited by the dynamic range of the carrier-regenerating PLL (phase-locked loop). The dynamic range of the PLL, and thus of the complete detector, has been greatly extended by using automatic gain control (AGG) and autozero techniques. After optimization of the AGC amplifiers, a sufficiently high gain control range of 55 dB has been established with a prototype integrated on a 400-MHz analog semicustom array. The resulting signal-handling dynamic range of the PLL has turned out to be more than 60 dB. It is concluded that the proposed synchronous detector architecture, equipped with appropriately designed circuits, can provide the performance required by upconversion receivers with limited IF selectivity at frequencies of about 100 MHz