A CCD FREQUENCY PRESCALER FOR BROAD-BAND APPLICATIONS

This paper describes a broadband, compact, and power-efficient frequen cy prescaler based on two-phase CCD's. The CCD frequency prescaler (CC D-FP) is similar in operation to flip-flop based divide-by-N circuits. However, the maximum operating frequency is determined by the charge transit time between CCD electrodes, rather than the propagation delay of a logic gate in which circuit parasitics limit performance. Since parasitic effects are minimized, relatively large gate length CCD elec trodes (1 mum) can be used in a millimeter wave device. A prototype CC D-FP has been implemented in a GaAs/AlGaAs modulation-doped CCD (MD-CC D) technology and demonstrated at frequencies up to 18 GHz. At 18.2 GH z the calculated power dissipation is 325 mW. The CCD-FP has a constan t input voltage sensitivity as a function of input frequency and the o utput signal is phase locked to the input. Expansion of the prescaler modulus incurs no penalty in speed of operation and very modest increa ses in power dissipation, circuit complexity, and chip area. In additi on, a novel method of simulating CCD's in SPICE is used extensively fo r circuit analysis. In conjunction with PISCES two-dimensional transie nt simulations of the 1-mum MD-CCD, SPICE analysis predicts that an In GaAs-based CCD-FP is capable of operating frequencies approaching 100 GHz. Both the two-dimensional device modeling and the circuit simulati ons are shown to be in excellent agreement with experimental data in t he microwave region.