Cadence Design Systems, Inc.

Gec Plessey Semiconductors, Inc.

Oskar Leuthold

Nigel Bleasdale

Paul Gregory

A system and method for simulating the noise characteristics of phase locked loops (PLL's) and other devices. Voltage Controlled Oscillator (VCO) transfer function and phase noise data is first imported for a particular circuit from a Radio Frequency (RF) simulator. The phase locked loop blocks in the circuit are converted to calibrated behavioral-level models. A combined analog/digital model is used to model the VCO, which in turn uses a pseudorandom signal generator for simulating VCO noise. Information about VCO periods is then written to a file or memory for post-processing, such as creating noise spectrum data and noise spectrum plots.

System and method for simulating the noise characteristics of phase locked loops in transient analysis

A method and apparatus for providing a lower frequency signal with reference to a higher frequency signal are disclosed. The apparatus of the invention comprises an oscillating signal generator, an integer logical divider, and a signal combiner. The signal generator receives an input voltage and, in response thereto, generates a first output oscillating signal and a second output oscillating signal, both having a first frequency. The two oscillating signals are separated by a ninety-degree phase shift. The integer logical divider receives the two oscillating signals and provides two output divided signals in response. The first divided signal is representative of the first oscillating signal except that its frequency is one-third the frequency of the first oscillating signal. Likewise, the second divided signal is representative of the second oscillating signal except that its frequency is one-third that of the second oscillating signal. The signal combiner receives these two divided signals and performs an XOR operation on them to produce an output signal having a second frequency which is equal to the first frequency divided by 1.5. Thus, the apparatus of the invention performs a logical divide-by 1.5 operation. By adjusting the phase difference between the two oscillating signals, and by properly modifying the other elements of the apparatus, other logical divide-by operations may be performed.

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Santa Cruz, CA, United States of America

Oskar Leuthold