Oscillators with active higher-in-order phase shift filtering
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorJesper Fredriksson
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Abstract
The present invention proposes a new way of improving the phase stability and frequency selectivity of a phase shift oscillator (100). By introducing a filter-order enhancing feedback loop (124) in association with a phase shift filter (122) in the oscillator, higher-order phase shift filtering can be achieved without using inductive elements as in conventional higher-order LC phase shift filters. This is a great advantage, since a high Q-value can be obtained without limited by the relatively high internal losses of inductive elements (L).
Claims12
An oscillator having at least one oscillator feedback system, wherein said oscillator feedback system comprises:
- a phase shift filter;
- and
- a filter-order enhancing feedback loop associated with said phase shift filter.
An oscillator having a number of phase shift filters arranged in a ring topology, wherein at least one of said phase shift filters is associated with a filter-order enhancing feedback loop for shaping the phase shift function of the phase shift filter to enable higher order phase shift filtering.
An oscillator having a cross-coupled oscillator feedback system comprising a number of phase shift filters, wherein each one of said phase shift filters is associated with a filter-order enhancing feedback loop for shaping the phase shift function of the phase shift filter to enable higher order phase shift filtering.
An oscillator having an oscillator feedback system, wherein said oscillator feedback system comprises:
- a phase shift filter arranged as a lead-and-lag network incorporating an active amplifier;
- and
- a filter-order enhancing feedback loop in connection with said active amplifier in said lead-and-lag network.
Dependencies are inferred from the claim text.