Tunable passive enhance Q microwave notch filter

Patent metadata

Field	Value
Publication number	US-10522889-B2
Application number	US-201815947906-A
Country	US
Kind code	B2
Filing date	Apr 9, 2018
Priority date	Apr 9, 2018
Publication date	Dec 31, 2019
Grant date	Dec 31, 2019

Abstract

A tunable notch filter comprising a transmission line, a tunable bandstop filter and a tunable bandpass filter. The transmission line has an input port, an output port and a length electrically connecting the input port to the output port and receiving an RF signal at the input port. The tunable bandstop filter comprises a first direct current voltage source, a first coupling line and a first tunable capacitor. The first direct current voltage source provides a first adjustable voltage to the first tunable capacitor. The first tunable capacitor adjusts its capacitance based on the first adjustable voltage. The tunable bandpass filter comprises a second direct current voltage source, a second coupling line and a second tunable capacitor. The second direct current voltage source provides a second adjustable voltage to second tunable capacitor. The second tunable capacitor adjusts its capacitance based on the second adjustable voltage.

First claim

What is claimed as new and desired to be protected by Letters Patent of the United States is:

1. A filter comprising:
a transmission line having an input port, an output port and a length electrically connecting said input port to said output port, said transmission line being operable to receive an RF signal at said input port, said length having a first portion, a second portion and a third portion, said second portion being disposed between said first portion and said third portion;
a tunable bandstop filter comprising a first direct current voltage source, a first coupling line and a first tunable capacitor, said first direct current voltage source being operable to provide a first adjustable voltage to said first tunable capacitor, said first tunable capacitor being operable to adjust a capacitance thereof based on the first adjustable voltage; and
a tunable bandpass filter comprising a second direct current voltage source, a second coupling line and a second tunable capacitor, said second direct current voltage source being operable to provide a second adjustable voltage to said second tunable capacitor, said second tunable capacitor being operable to adjust a capacitance thereof based on the second adjustable voltage,
wherein said tunable bandpass filter and said transmission line are arranged such that said second coupling line is operable to couple a first portion of the RF signal from said first portion of said length and such that said first portion of said length transmits a second portion of the RF signal to said second portion of said length,
wherein said tunable bandstop filter and said transmission line are arranged such that said first coupling line is operable to couple, to ground, a third portion of the RF signal as provided by said first portion of said length at said second portion of said length and such that said second portion of said length transmits a fourth portion of the RF signal to said third portion of said length,

wherein said tunable bandpass filter and said transmission line are further arranged such that said second coupling line is further operable to couple a passed portion of the first portion of the RF signal to said third portion of said length.

2. The filter of claim 1 , where said transmission line, said tunable bandstop filter and tunable bandpass filter are further arranged such that the fourth portion of the RF signal is one hundred eighty degrees out of phase with the first portion of the RF signal coupled to said third portion of said length.

3. The filter of claim 2 ,
wherein said first direct current voltage source is operable to provide a first bias voltage to said first tunable capacitor such that said tunable bandstop filter is operable to notch filter the second portion of the RF signal such that the fourth portion of the RF signal has frequency response having a notch centered around a predetermined frequency, and
wherein said second direct current voltage source operable to provide a second bias voltage to said second tunable capacitor such that said tunable bandpass filter is operable to bandpass filter the second portion of the RF signal such that the passed portion of the first portion of the RF signal has frequency response having a pass band centered around the predetermined frequency.

4. The filter of claim 3 , wherein said transmission line comprises a microstrip.

5. The filter of claim 1 ,
wherein said first direct current voltage source is operable to provide a first bias voltage to said first tunable capacitor such that said tunable bandstop filter is operable to notch filter the second portion of the RF signal such that the fourth portion of the RF signal has frequency response having a notch centered around a predetermined frequency, and
wherein said second direct current voltage source operable to provide a second bias voltage to said second tunable capacitor such that said tunable bandpass filter is operable to bandpass filter the second portion of the RF signal such that the passed portion of the first portion of the RF signal has frequency response having a pass band centered around the predetermined frequency.

6. The filter of claim 5 , wherein said transmission line comprises a microstrip.

7. The filter of claim 1 , wherein said transmission line comprises a microstrip.

8. A filtering method comprising:
providing an RF input signal to a tunable filter having:
a transmission line having an input port, an output port and a length electrically connecting the input port to the output port, the transmission line being operable to receive the RF signal at the input port, the length having a first portion, a second portion and a third portion, the second portion being disposed between the first portion and the third portion;
a tunable bandstop filter comprising a first direct current voltage source, a first coupling line and a first tunable capacitor, the first direct current voltage source being operable to provide a first adjustable voltage to the first tunable capacitor, the first tunable capacitor being operable to adjust a capacitance thereof based on the first adjustable voltage; and
a tunable bandpass filter comprising a second direct current voltage source, a second coupling line and a second tunable capacitor, the second direct current voltage source being operable to provide a second adjustable voltage to said second tunable capacitor, the second tunable capacitor being operable to adjust a capacitance thereof based on the second adjustable voltage; and

outputting a filtered signal,
wherein the tunable bandpass filter and the transmission line are arranged such that the second coupling line is operable to couple a first portion of the RF signal from the first portion of the length and such that the first portion of the length transmits a second portion of the RF signal to the second portion of the length,
wherein the tunable bandstop filter and the transmission line are arranged such that the first coupling line is operable to couple, to ground, a third portion of the RF signal as provided by the first portion of the length line at the second portion of the length and such that the second portion of the length transmits a fourth portion of the RF signal to the third portion of the length,
wherein the tunable bandpass filter and the transmission line are further arranged such that the second coupling line is further operable to couple a passed portion of the first portion of the RF signal to the third portion of the length.

9. The filtering method of claim 8 , where the transmission line, the tunable bandstop filter and tunable bandpass filter are further arranged such that the fourth portion of the RF signal is one hundred eighty degrees out of phase with the first portion of the RF signal coupled to the third portion of the length.

10. The filtering method of claim 9 ,
wherein the first direct current voltage source is operable to provide a first bias voltage to the first tunable capacitor such that the tunable bandstop filter is operable to notch filter the second portion of the RF signal such that the fourth portion of the RF signal has frequency response having a notch centered around a predetermined frequency, and
wherein the second direct current voltage source operable to provide a second bias voltage to the second tunable capacitor such that the tunable bandpass filter is operable to bandpass filter the second portion of the RF signal such that the passed portion of the first portion of the RF signal has frequency response having a pass band centered around the predetermined frequency.

11. The filtering method of claim 10 , wherein said transmission line comprises a microstrip.

Assignees

• Spawar Systems Ct Pacific
• Us Navy

Inventors

• Rowland Jason F
• Chieh Jia-Chi S

Classifications

• H01P1/20

  Frequency-selective devices, e.g. filters · CPC title

• H01P1/203 Primary

  Strip line filters · CPC title

• H01P3/08

  Microstrips; Strip lines · CPC title

• H01P1/2039 Primary

  Galvanic coupling between Input/Output · CPC title

• H03H2210/012

  Centre frequency; Cut-off frequency · CPC title