Notch filter incorporating saw devices and a delay line
AssigneeCTS Corporation
InventorThomas S. Hickernell
Life of this patent
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Abstract
A notch filter (100) includes a parallel coupled delay line (104) and surface acoustic wave resonator (102) which provides a pole at a desired passband. The surface acoustic wave resonator (102) and the delay line (104) are configured to provide a zero at an undesired frequency or stopband. In this way, the notch filter (100) augments the stopband rejection of an associated cascaded surface acoustic wave ladder filter (105). The notch filter (100) also provides a pole at a desired frequency or passband such that losses due to the notch filter (100) at the desired passband are minimized, thereby improving overall insertion loss performance.
Claims12
A notch filter with a first port and a second port and having a first attenuation at a first undesired frequency, the notch filter comprising:
- a delay line coupled in series between the first and second ports;
- and
- a surface acoustic wave resonator coupled in series between the first and second ports and in parallel with the delay line,
- the surface acoustic wave resonator and the delay line being configured to provide a zero at the first undesired frequency and a pole at a desired frequency such that insertion loss contributed by the notch filter at the desired frequency is minimized.
A surface acoustic wave filter including a ladder filter disposed on a piezoelectric substrate in a multilayer ceramic package, the surface acoustic wave filter including a notch filter comprising:
- a delay line coupled in series between first and second ports;
- and
- a surface acoustic wave resonator coupled in series between the first and second ports and in parallel with the delay line,
- the surface acoustic wave resonator and the delay line being configured to provide a zero at the first undesired frequency and a pole at a desired frequency such that insertion loss contributed by the notch filter at the desired frequency is minimized,
- the surface acoustic wave ladder filter coupled to the second port, the surface acoustic wave resonator of the notch filter functioning as a series resonator of the ladder filter wherein the ladder filter requires one less individual pole due to the additional pole provided by the surface acoustic wave resonator of the notch filter.
A radio communication device having a radio frequency receiver, transmitter, and a duplexer including a notch filter, the notch filter with a first port and a second port and having a first stopband at a first undesired frequency, the notch filter comprising:
- a delay line coupled in series between the first and second ports;
- and
- a surface acoustic wave resonator coupled in series between the first and second ports and in parallel with the delay line,
- the surface acoustic wave resonator and the delay line being configured to provide a zero at the first undesired frequency and a pole at a desired frequency such that insertion loss contributed by the notch filter at the desired frequency is minimized.
Dependencies are inferred from the claim text.