Microwave active notch filter and operating method with photonic bandgap crystal feedback loop
First Claim
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1. An active notch filter, comprising:
- an amplifier with an input for receiving an electrical microwave input signal and an output; and
a first photonic bandgap crystal (PBC) having an aperiodic dispersion relation connected in a feedback loop between said amplifier'"'"'s input and output, said crystal having at least one frequency bandgap within which it substantially attenuates the transmission of electromagnetic radiation, said PBC'"'"'s aperiodic dispersion relation causing said crystal to substantially pass the transmission of electromagnetic radiation at harmonic frequencies of said frequency bandgap so that the notch filter operates stably, said feedback loop causing said amplifier to impart a greater amplification to signals within said bandgap than to signals outside of said bandgap so that the amplifier and the PBC together filter and amplify the microwave input signal simultaneously thereby enhancing signal sensitivity.
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Abstract
An active microwave notch filter is formed by connecting a photonic bandgap crystal (PBC) in a feedback loop around a microwave amplifier. The PBC has an attenuation bandgap which establishes a frequency range of preferential amplification. Frequency selectivity can be achieved by applying signals to the dielectric members which form the PBC to vary their dielectric constants, and thus the bandgap, or by selecting among multiple parallel PBCs. Antennas are provided to transduce the electrical input to the PBC into electromagnetic radiation, and then back to an electrical signal after the radiation has been filtered by the PBC.
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Citations
21 Claims
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1. An active notch filter, comprising:
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an amplifier with an input for receiving an electrical microwave input signal and an output; and a first photonic bandgap crystal (PBC) having an aperiodic dispersion relation connected in a feedback loop between said amplifier'"'"'s input and output, said crystal having at least one frequency bandgap within which it substantially attenuates the transmission of electromagnetic radiation, said PBC'"'"'s aperiodic dispersion relation causing said crystal to substantially pass the transmission of electromagnetic radiation at harmonic frequencies of said frequency bandgap so that the notch filter operates stably, said feedback loop causing said amplifier to impart a greater amplification to signals within said bandgap than to signals outside of said bandgap so that the amplifier and the PBC together filter and amplify the microwave input signal simultaneously thereby enhancing signal sensitivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of filtering an electrical microwave input signal, comprising:
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obtaining the difference between said input signal and an electrical feedback signal to produce a difference signal, amplifying said difference signal to produce an electrical output signal, and generating said feedback signal by transducing said output signal into electromagnetic radiation, transmitting said radiation through a photonic bandgap crystal (PBC) having an aperiodic dispersion relation to attenuate a selected frequency band while passing the harmonic frequencies of said selected frequency band to insure stable operation, and transducing said filtered radiation back into said feedback signal, said feedback signal causing input signals within said selected frequency band to be simultaneously filtered and amplified thereby enhancing signal sensitivity. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification