Fast frequency switching synthesizer
US5872487A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 5, 1997 |
| Grant date | Feb 16, 1999 |
| Priority date | — |
| Expiry date | Jun 5, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/1075
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A frequency synthesizer that can switch an output frequency fast and generates little spurious output is provided. This frequency synthesizer comprises a phase locked loop including a voltage-controlled oscillator, a high frequency divider, a phase frequency comparator and a low-pass filter. The divisor controller circuit supplies a divisor that varies cyclically to the high frequency divider for a fractional dividing operation. When switching the output frequency, a passing bandwidth of the low-pass filter is enlarged to widen a loop bandwidth of the phase locking loop for fast switching. After switching, the passing bandwidth of the low-pass filter is reduced to narrow the loop bandwidth for reduction of a spurious output, at the timing when a predetermined period has passed for the switched output frequency to stabilize substantially.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.