EEE445_Lectr24_cavity_reson

EEE445_Lectr24_cavity_reson - Crystal Resonators, Waveguide...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
EEE 591/445 Lecture 24 1 Crystal Resonators, Waveguide Cavity Resonators and Dielectric Resonators Overview of crystal resonators A crystal resonator consists of a small piece of quartz mounted between two metallic plates. Mechanical oscillations in the crystal are excited through the piezoelectric effect. Have unloaded Q ’s as high as 100,000; compared to lumped LC resonators which have unloaded Q ’s of in the 100s. Also have extremely small temperature drift (less than 0.001%/deg C).
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EEE 591/445 Lecture 24 2 Waveguide Resonators Waveguide resonators are usually constructed by short-circuiting the two ends of a length of standard waveguide to form a cavity. Coupling to a waveguide resonator is typically achieved using Small hole(s) Wire loops or probes
Background image of page 2
EEE 591/445 Lecture 24 3 Overview of Waveguide Resonators Precision tuning of the resonator is usually required. Precision tuning can be achieved using tuning screws. Waveguide resonators have large but finite Q . c d Q Q Q 1 1 1 + = Due to conductor loss Due to dielectric loss
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EEE 591/445 Lecture 24 4 6.3 Rectangular waveguide cavities Rectangular cavities with metallic walls were studied in EEE 341. We’ll provide a brief review here. Resonant Condition for Rectangular Cavity Waveguide propagation mode 2 2 2 2 2 2 add front and back walls, yielding cavity , 1,2,3, resonant wavenumber mn mn mnl m n k a b d m n l k a b d π β     = - -         = =       = + +             l l L (6.37) (6.38) (6.39)
Background image of page 4
EEE 591/445 Lecture 24 5 Geometry of Rectangular Cavity a b d
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
EEE 591/445 Lecture 24 6 Lowest Order Resonant Frequency of Rectangular Cavity r r ck f d a k μ ε π 2 : mode TE for frequency resonance Lowest 101 101 2 2 101 101 = + = If b < a and b < d , (6.40)
Background image of page 6
EEE 591/445 Lecture 24 7 Q of Rectangular Cavity The Q of the TE 10 l modes of a cavity with lossy conducting walls but lossless dielectric filling is given on p. 281. for TE 101 , The contribution to the Q due to dielectric losses is simply overall 1 tan 1 1 1 d d c Q Q Q Q δ = = + ( 29 ( 29 3 101 0 101 2
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 30

EEE445_Lectr24_cavity_reson - Crystal Resonators, Waveguide...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online