Rayleigh and surface transverse waves are being increasingly

Rayleigh waves that die out within two to three wavelengths
in depth from the surface, typically have velocities around 3000 m/s. But there
are some crystal cuts (explained in Chapter 3) such as YX-128? Lithium
niobate (LiNbO3) which propagate Rayleigh SAW at velocities close to
4000 m/s. Nevertheless, to achieve frequencies of operation above 1 GHz,
linewidths less than 1 µm are needed. So, pseudo-SAW modes with higher
velocities such as leaky SAWs and surface transverse waves (STW) are getting
increased attention due to their potential for achieving higher operating
frequencies. Table 1.1 shows a comparison of leaky and surface transverse wave
to that of Rayleigh wave velocities in different materials. With velocities
above 4000 m/s, devices based on leaky and surface transverse waves are being
increasingly employed in the lower GHz (1-3 GHz) region. In particular, STW
based devices above 2 GHz have been reported by Avramov et al. 9. More
recently, a second order leaky SAW mode called longitudinal leaky SAW 9 (LLSAW)
with velocities above 6000 m/s have been reported to exist in several
substrates. Longitudinal leaky waves with a velocity of 6700 m/sec on lithium
tetraborate (Li2B4O7) have been reported by Sato and Abe 10. They have also
fabricated filters at 1.2 GHz and 1.5 GHz without using sub-micron fabrication
techniques 11. Similarly, LLSAW on YZ-LiNbO3 with velocities around 6100 m/s
have been used at 2.5 GHz 12 and 5.2 GHz 13 by Makonnen et al. Also,
different crystal cuts of the same materials are also often explored in order
to strike a balance with velocity, temperature effects, insertion losses and
other propagation issues.

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Rayleigh waves that die out within two to three wavelengths
in depth from the surface, typically have velocities around 3000 m/s. But there
are some crystal cuts (explained in Chapter 3) such as YX-128? Lithium
niobate (LiNbO3) which propagate Rayleigh SAW at velocities close to
4000 m/s. Nevertheless, to achieve frequencies of operation above 1 GHz,
linewidths less than 1 µm are needed. So, pseudo-SAW modes with higher
velocities such as leaky SAWs and surface transverse waves (STW) are getting
increased attention due to their potential for achieving higher operating
frequencies. Table 1.1 shows a comparison of leaky and surface transverse wave
to that of Rayleigh wave velocities in different materials. With velocities
above 4000 m/s, devices based on leaky and surface transverse waves are being
increasingly employed in the lower GHz (1-3 GHz) region. In particular, STW
based devices above 2 GHz have been reported by Avramov et al. 9. More
recently, a second order leaky SAW mode called longitudinal leaky SAW 9 (LLSAW)
with velocities above 6000 m/s have been reported to exist in several
substrates. Longitudinal leaky waves with a velocity of 6700 m/sec on lithium
tetraborate (Li2B4O7) have been reported by Sato and Abe 10. They have also
fabricated filters at 1.2 GHz and 1.5 GHz without using sub-micron fabrication
techniques 11. Similarly, LLSAW on YZ-LiNbO3 with velocities around 6100 m/s
have been used at 2.5 GHz 12 and 5.2 GHz 13 by Makonnen et al. Also,
different crystal cuts of the same materials are also often explored in order
to strike a balance with velocity, temperature effects, insertion losses and
other propagation issues.Resonant modes R13Rayleigh waves that die out within two to three wavelengths in depth from the surface, typically have velocities around 3000 m/s. But there are some crystal cuts(explained in Chapter 3) such as YX-128? Lithium niobate (LiNbO3) which propagate Rayleigh SAW at velocities close to 4000 m/s. Nevertheless, to achieve frequencies of operation above 1 GHz, linewidths less than 1 µm are needed. So, pseudo-SAW modes with higher velocities such as leaky SAWs and surface transverse waves (STW) are getting increased attention due to their potential for achieving higher operating frequencies. Table 1.1 shows a comparison of leaky and surface transversewave to that of Rayleigh wave velocities in different materials. With velocities above 4000 m/s, devices based on leaky and surface transverse waves are being increasingly employed in the lower GHz (1-3 GHz) region. In particular, STW based devices above 2 GHz have been reported by Avramov et al. 9. More recently, a second order leaky SAW mode called longitudinal leaky SAW 9 (LLSAW) with velocitiesabove 6000 m/s have been reported to exist in several substrates. Longitudinal leaky waves with a velocity of 6700 m/sec on lithium tetraborate (Li2B4O7) have been reported by Sato and Abe 10. They have also fabricated filters at 1.2 GHz and 1.5 GHz without using sub-micron fabrication techniques 11. Similarly, LLSAW on YZ-LiNbO3 with velocities around 6100 m/s have been used at 2.5 GHz 12 and 5.2GHz 13 by Makonnen et al. Also, different crystal cuts of the same materials are also often explored in order to strike a balance with velocity, temperature effects, insertion losses and other propagation issuesResonant modes R13Rayleigh waves that die out within two to three wavelengths in depth from the surface, typically have velocities around 3000 m/s. But there are some crystal cuts(explained in Chapter 3) such as YX-128? Lithium niobate (LiNbO3) which propagate Rayleigh SAW at velocities close to 4000 m/s. Nevertheless, to achieve frequencies of operation above 1 GHz, linewidths less than 1 µm are needed. So, pseudo-SAW modes with higher velocities such as leaky SAWs and surface transverse waves (STW) are getting increased attention due to their potential for achieving higher operating frequencies. Table 1.1 shows a comparison of leaky and surface transversewave to that of Rayleigh wave velocities in different materials. With velocities above 4000 m/s, devices based on leaky and surface transverse waves are being increasingly employed in the lower GHz (1-3 GHz) region. In particular, STW based devices above 2 GHz have been reported by Avramov et al. 9. More recently, a second order leaky SAW mode called longitudinal leaky SAW 9 (LLSAW) with velocitiesabove 6000 m/s have been reported to exist in several substrates. Longitudinal leaky waves with a velocity of 6700 m/sec on lithium tetraborate (Li2B4O7) have been reported by Sato and Abe 10. They have also fabricated filters at 1.2 GHz and 1.5 GHz without using sub-micron fabrication techniques 11. Similarly, LLSAW on YZ-LiNbO3 with velocities around 6100 m/s have been used at 2.5 GHz 12 and 5.2GHz 13 by Makonnen et al. Also, different crystal cuts of the same materials are also often explored in order to strike a balance with velocity, temperature effects, insertion losses and other propagation issues