Characteristics of the ideal resonator for low Phase Noise oscillator are as follows:

• High Group Delay (high resonator Loaded-Q).
• High operating frequency.

• Low Loss.

• Moderate Drive Capability.

• Low frequency sensitivity to environmental stress (vibration, temperature, etc).

• Good short-term and long-term frequency stability.

• Accurate frequency set-on capability.

• External frequency tuning capability.

• No undesired resonant modes or higher loss in undesired resonant
  modes or undesired resonant mode frequencies far from desired
  operating frequency.

• High manufacturing yield of acceptable devices.

• In-circuit resonator effective Q can be determined by
  intentionally altering the circuit phase shift by a known amount and measuring the resultant oscillator signal frequency shift.