A novel electromagnetic interference (EMI) filter is designed to attenuate one or more specific frequencies in order to provide electromagnetic compatibility of an electronic device while in the presence of an electromagnetic emitter operating at the same or similar frequencies. The EMI filter of the present invention combines an EMI low pass filter with one or more “notch” EMI filters tuned to the specific frequencies of interest. When combined in this fashion, the notch EMI filter can effectively attenuate the electromagnetic field of a powerful low frequency emitter which is outside the effective attenuation frequency range of the low pass filter, which is itself effective at filtering a broad range of higher frequencies. In a preferred embodiment, the notch EMI filter capacitive element is integrated in a co-planar relationship with a ceramic feedthrough filter capacitor assembly. This combined notch and low pass filter arrangement is particularly effective in an implantable medical device such as a cardiac pacemaker or implantable cardioverter defibrillator (ICD) against passage of external interference signals, such as those caused by both digital cellular phones and electronic article surveillance systems operating at low frequencies.

Electromagnetic interference (emi) filter and process for providing electromagnetic compatibility of an electronic device while in the presence of an electromagnetic emitter operating at the same frequency

An antenna for use with portable duplex radio transceivers, such as those found in hand-held cellular telephones, which includes a pair of co-planar radiating patch elements elevated above a conductive surface by a conductive bar. The surface and bar define a reference ground plane which inherently isolates the patches. The patches are shaped so that they operate in a desired frequency band as well as band-pass filters--one of the patches is tuned to the transmit band and serves a transmit structure, and the other patch is tuned to the receive band and serves as a receive structure. Switching devices such as positive-intrinsic negative (PIN) diodes can be disposed along the space between the patches and the ground plane to allow each structure to be tuned. The antenna is efficient, because of inherent isolation between the receive and transmit patches, and eases the front end filtering functions traditionally performed by a duplexer. It can be completely enclosed within the chassis of a hand-held telephone.

Duplexing antenna for portable radio transceiver

A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas. The antenna is not visible to a passerby observer when installed, since it is literally part of the vehicle. The microstrip radiating element is conformal to a passenger vehicle, and may, for example, be mounted under a plastic roof between the roof and the headliner.

Circular microstrip vehicular rf antenna

Near-isotropic low-profile microstrip radiator especially suited for use as a mobile vehicle antenna

Preferred embodiments include a microstrip patch antenna (38) which also acts as the resonator for an oscillator powered by IMPATT diodes (34, 36); this forms a monolithic transmitter (30) for microwave and millimeter wave frequencies.

Monolithic microwave transmitter/receiver

Two cylindrical sleeves of metal oxide varistor material (MOV) are used asapacitive elements of a low pass feedthrough pi-filter network. A metallic housing coaxially surrounds the MOV sleeves and provides electrical contact to ground. The inner surface of each sleeve is electrically connected to an inductor whose leads are terminated by feedthrough connectors on either side of the metal housing. The sleeve inner diameter is large enough to envelop the inductance thereby reducing the package length. The combined shunt capacitance and series inductance form the low pass pi-filter network. At normal signal levels, the package acts as a normal feedthrough low pass pi-filter network. At higher signal levels and transients, the bipolar MOV components clamp the voltage to a given level, determined by the MOV material grain structure and sleeve thickness.

EMP line filter using MOV devices

A microstrip array antenna, including spaced radiator elements supplied w microwave power and separated from an underlying ground reference plane by a layer of dielectric material, in which the antenna beam is phase scanned by periodically closing switching devices connected between the reference plane and at least one null point of each radiator element. In one embodiment, the radiator elements are identical rectangular patches disposed along a path, each patch having a length parallel to the path of one-half wavelength and a width transverse to the path not exceeding one wavelength in the underlying dielectric material at the antenna operating frequency. The patches are connected in series to receive microwave power by conductive strip elements whose widths are selected to effect a desired distribution of radiated microwave power from the patches.

Phase scanned microstrip array antenna

Two partial circular chips of metal oxide varistor (MOV) material are moud in a TO-5 transistor case. Each chip acts as a capacitive element to ground for a low pass pi-filter network. An inductance, whose value is chosen for the required filter impedance and cut off frequency, is placed across the MOV chips and connected to TO-5 contacts, along with the MOV, completing the filter network. At normal signal levels, the package acts as a normal low-pass pi-filter network. At higher signal levels and transients, the bipolar MOV components clamp the voltage to a given level, determined by the MOV material grain structure and chip thickness.

EMP circuit board filter using MOV devices

A variable microwave stripline power divider, in which the power seen at h of two outputs can be varied over a wide range without appreciably changing the power seen at the other output. In one embodiment, this is accomplished mechanically by shorting posts connecting the patch member to a ground plane member of the device at selected points. In another embodiment of the invention, this is accomplished electronically by a plurality of electronic switching devices connected between a like plurality of patch member shorting points and a ground plane member, which are selectively activated by a microcomputer.

Morris Campi

Papers

EMP line filter using MOV devices

Phase scanned microstrip array antenna

EMP circuit board filter using MOV devices

Variable microwave stripline power divider