Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
1999-11-01
2002-03-12
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Unwanted signal suppression
C327S554000, C327S592000, C333S166000, C333S173000, C333S205000, C333S217000, C331S077000, C330S303000, C330S306000
Reexamination Certificate
active
06356143
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of radio frequency electronics. In particular the present invention discloses an active filter for filtering signals over a relatively large bandwidth range.
BACKGROUND OF THE INVENTION
Computer and digital communication networks have traditionally been constructed using wired network technologies. However, the expense and difficulty of installing a wired network has sped the growth of a wireless digital communication industry. Cellular telephone networks, satellite communication networks, and wireless computer networks all now use digital wireless communication technologies.
The military and large corporations have used digital wireless communication systems for many years now. However, the consumer market for digital wireless communications is still relatively young. To penetrate the consumer market, digital wireless communication systems must be simple, reliable, and most importantly inexpensive. Therefore, it would be desirable to improve the designs of wireless communication circuitry such that the wireless communication circuitry can be used in the consumer market.
SUMMARY OF THE INVENTION
A variable frequency active filter circuit for tuning in a specific bandpass frequency is disclosed. The active filter incorporates a controlled oscillator circuit for tuning into a specific frequency range. A frequency input signal controls the active filter bandpass frequency by tuning the oscillator circuit to a desired frequency. The controlled oscillator circuit further includes a gain input. The gain input is set to a value just below where the oscillator circuit would oscillate.
Other objects, features, and advantages of present invention will be apparent from the company drawings and from the following detailed description.
REFERENCES:
patent: 5180996 (1993-01-01), Shiga
patent: 5371475 (1994-12-01), Brown
patent: 5550520 (1996-08-01), Kabayashi
patent: 5977835 (1999-11-01), Huang
Callahan Timothy P.
Intreon Corporation
Nguyen Minh
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