US Patent 8130054 Frequency-adjustable radio frequency isolator circuitry

The present invention relates to a frequency-adjustable radio frequency (RF) isolator that may operate as a bandpass filter when processing RF signals in a forward direction and may operate as a notch filter when processing RF signals in a reverse direction. The notch filter has a notch frequency, which is adjustable to provide adequate isolation from reflected signals at a specific operating frequency. The frequency-adjustable RF isolator may include an electro-magnetic gyrator coupled to a variable impedance circuit, which may present a variable impedance to the electro-magnetic gyrator. The notch frequency may be dependent on the variable impedance. The notch filter may be a single-notch filter or may be a multiple-notch filter.