  The quasi-periodic feature of 1-10 years exhibited in pulsar timing noise has
not been well understood since 1980. The recently demonstrated correlation
between timing noise and variation of pulse profile motivates us to further
investigate its origins. We suggest that the quasi-periodicity feature of
timing noise, with rapid oscillations lying on lower frequency structure, comes
from the geodetic precession of an unseen binary system, which induces
additional motion of the pulsar spin axis. The resultant change of azimuth and
latitude at which the observer's line of sight crosses the emission beam is
responsible for the variation of timing noise and pulse profile respectively.
The first numerical simulation to both timing noise and pulse profile variation
are thus performed, from which the orbital periods of these pulsars are of 1-35
minutes. Considering the existence of the ultracompact binary white dwarf of
orbital period of 5.4 minute, HM Cancri, such orbital periods to pulsar
binaries are not strange. The change of latitude of the magnetic moment
exceeding the range of emission beam of a pulsar results in the intermittency,
which explains the behavior of PSR B1931+24. Therefore, it provides not only a
mechanism of the quasi-periodic feature displayed on some ``singular" pulsars,
like timing noise, variation of pulse profile and intermittency; but also a new
approach of searching ultra-compact binaries, possibly pulsar-black hole binary
systems.
