Tunable bandpass filter and method thereof

• US 7,116,954 B2
• Filed: 11/05/2004
• Issued: 10/03/2006
• Est. Priority Date: 04/11/2001
• Status: Expired due to Term

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Wireless Corporation (Kyocera Corporation)
• Inventors: Toncich, Stanley S.
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Le, Nhan T.
• Application Number:
  US10/981,814
• Publication Number:
  US 20050085200A1
• Time in Patent Office: 697 Days
• Field of Search: 333/171, 333/174, 333/175, 333/176, 333/167, 333/170, 455/286, 455/339, 455/120, 455/121, 455/193.1, 455/2, 455280-282, 455/178.1, 455/191
• US Class Current: 455/193.2
• CPC Class Codes: G01R 27/2694 Measuring dielectric loss, e.g. loss angle, loss factor or power factor
• CPC Class Codes: H01G 7/06 having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors electrets H01G7/02
• CPC Class Codes: H01L 27/0808 Varactor diodes
• CPC Class Codes: H01P 1/203 Strip line filters
• CPC Class Codes: H01P 1/20336 Comb or interdigital filters
• CPC Class Codes: H01P 1/20363 Linear resonators
• CPC Class Codes: H01P 1/20381 Special shape resonators
• CPC Class Codes: H01P 1/2039 Galvanic coupling between Input/Output
• CPC Class Codes: H01P 1/2056 Comb filters or interdigital filters with metallised resonator holes in a dielectric block
• CPC Class Codes: H01P 1/213 combining or separating two or more different frequencies H01P1/215 takes precedence
• CPC Class Codes: H01P 5/04 with variable factor of coupling
• CPC Class Codes: H03B 5/04 Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
• CPC Class Codes: H03B 5/124 the means comprising a voltage dependent capacitance
• CPC Class Codes: H03B 5/1262 the means comprising switched elements
• CPC Class Codes: H03B 5/1293 having means for achieving a desired tuning characteristic, e.g. linearising the frequency characteristic across the tuning voltage range
• CPC Class Codes: H03B 5/1841 the frequency-determining element being a strip line resonator H03B5/1805, H03B5/1817, H03B5/1864 and H03B5/1882 take precedence
• CPC Class Codes: H03B 5/362 the amplifier being a single transistor H03B5/364 - H03B5/368 take precedence
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/111 the amplifier being a dual or triple band amplifier, e.g. 900 and 1800 MHz, e.g. switched or not switched, simultaneously or not
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 : Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 3/191 : Tuned amplifiers H03F3/193, H03F3/195 take precedence
• CPC Class Codes: H03H 7/0123 : comprising distributed impedance elements together with lumped impedance elements
• CPC Class Codes: H03H 7/12 : Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency H03H7/09 takes precedence; automatic control of bandwidth in amplifiers H03G5/16
• CPC Class Codes: H03H 7/20 : Two-port phase shifters providing an adjustable phase shift
• CPC Class Codes: H03J 5/246 : using electronic means H03J5/244 takes precedence
• CPC Class Codes: H03L 1/022 : by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence
• CPC Class Codes: H03L 7/18 : using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence
• CPC Class Codes: H04B 1/0053 : with common antenna for more than one band
• CPC Class Codes: H04B 1/0458 : Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/30 : for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/40 : Circuits

Abstract

The present invention provides a tunable bandpass filter and method thereof. In a preferred embodiment, the tunable bandpass filter uses variable ferro-electric capacitors to adjust both the passband and the notch across the normal operating range of a wireless communications device. The tunable bandpass filter is capable of providing a tuning range over a desired frequency range with low I.L. and high out-of-band rejections.

Claims

1. A tunable bandpass filter comprising:

a first resonator;

a capacitive component connected to the first resonator, wherein the capacitive component causes a notch in a frequency response of the tunable bandpass filter, and wherein the capacitive component has variable capacitance;

a second resonator connected to the capacitive component;

a first variable capacitive block comprising a first variable ferro-electric capacitor, the first variable capacitive block connected to the first resonator;

a second variable capacitive block comprising a second variable ferro-electric capacitor, the second variable capacitive block connected to the second resonator; and

,

a control circuit connected to the first variable capacitive block, the second variable capacitive block, and the capacitive component, wherein the control circuit is configured to tune a passband and to vary the notch of the tunable bandpass filter.

2. The tunable bandpass filter of claim 1, wherein the first variable capacitive block is connected to ground through a first DC blocking capacitor, and the second variable capacitive block is connected to ground through a second DC blocking capacitor.

3. The tunable bandpass filter of claim 1, wherein the capacitive component comprises a third variable ferro-electric capacitor.

4. The tunable bandpass filter of claim 3, wherein the control circuit varies the notch so that the notch tracks the passband.

5. The tunable bandpass filter of claim 4, wherein the capacitive component further comprises a fourth variable ferro-electric capacitor and a divider network;

wherein the divider network is configured to provide an appropriate tuning range to the third and the fourth ferro-electric capacitors.

6. The tunable bandpass filter of claim 1, wherein the tunable bandpass filter has an insertion loss of less than 3.5 dB and an out-of band rejection of at least 38 dB.

7. The tunable bandpass filter of claim 1, wherein the tunable bandpass filter has a bandwidth of at least 60 MHz.

8. The tunable bandpass filter of claim 1, wherein the first and the second resonators are volumetric resonators.

9. The tunable bandpass filter of claim 1, wherein the first variable capacitive block is integrated with the first resonator, and the second variable capacitive block is integrated with the second resonator.