Plural cavity bandpass waveguide filter

Claim 2

A plural cavity waveguide filter comprising, a. a plurality of waveguide cavities, each resonating at its resonant frequency in a first and a second independent orthogonal mode; b. first discontinuity coupling means oriented in each of said cavities for intra coupling said first mode to said second mode; c. second coupling means connecting selected ones of said cavities for inter coupling like oriented modes in said selected cavities said second coupling means including polarization discriminating means adapted to provide selective inter coupling between like oriented modes in said cavities.

Claim 3

The invention as recited in claim 1 wherein said first coupling means is adaptable to provide either an intra coupling having a first phase or an intra coupling hAving a second phase differing from said first phase by 180* .

Claim 4

The invention as recited in claim 2 wherein said second coupling means includes a reflective plate directly connecting two of said cavities, said plate including an iris for selectively inter coupling the identical modes in said two cavities.

Claim 5

The invention as recited in claim 1 wherein said filter includes tuning means in each of said cavities for independently tuning each of said modes to the cavity resonant frequency.

Claim 6

The invention as recited in claim 4 wherein said second coupling means is a reflective plate having a coupling iris, the dimensions of said iris being selected to provide said selective inter coupling between identical modes.

Claim 7

The invention as recited in claim 5 wherein said waveguide cavities are cylindrical waveguide sections and wherein said tuning means includes two adjustable screws mounted in said waveguide sections and coincidently disposed along said independent orthogonal resonant modes.

Claim 8

The invention as recited in claim 6 wherein said plurality of cavities include an input and an output cavity, said input cavity being coupled to an input waveguide by a first reflective plate having a polarization discriminating coupling iris, and said output cavity of the filter is connected to an output waveguide by a second reflective plate having a polarization discriminating iris.

Claim 9

The invention as recited in claim 1 comprising N physical cavities resonating in said orthogonal modes whereby said filter is equivalent to 2N physical cavities resonating in a single mode.

Claim 10

A waveguide filter having an elliptic function response comprising: a. a first waveguide cavity resonant in first and second independent orthogonal modes; b. a second waveguide cavity resonant in said first and said second independent orthogonal modes; c. tuning means in each of said cavities for independently tuning each of said resonant modes to its resonant frequency; d. coupling means in said first cavity for capacitively intra coupling said first resonant mode to said second resonant mode; e. coupling means in said second cavity for capacitively coupling said first resonant mode to said second resonant mode and for shifting the phase of said second mode by 180* with respect to said first mode of said first cavity; f. inductive coupling means for selectively inter coupling said first resonant modes and said second resonant modes in said cavities.

Claim 11

A waveguide filter having an elliptic function response comprising: a. a first waveguide cavity resonant in first and second independent orthogonal modes; b. a second waveguide cavity resonant in said first and said second independent orthogonal modes; c. tuning means in each of said cavities for independently tuning each of said resonant modes to its resonant frequency; d. coupling means in said first cavity for capacitively intra coupling said first resonant mode to said second resonant mode; e. coupling means in said second cavity for capacitively coupling said first resonant mode to said second resonant mode and for shifting the phase of said second mode by 180* with respect to said first mode of said first cavity; f. inductive coupling means for selectively inter coupling said first resonant modes and said second resonant modes in said cavities.

Claim 12

An elliptic filter as recited in claim 9 wherein said inductive coupling means physically disposed between said first and said second waveguide cavities.

Claim 13

A filter as recited in claim 10 wherein said tuning means comprise two screws, mounted in the wall of each cavity, which are coincident with the vectors of said orthogonal modes.

Claim 14

A filter as recited in claim 11 wherein said inductive coupling means is a first reflective plate having a coupling iris whereby the degree of coupling between identical modes in each cavity is selectively adjusted by varying the dimensions of said iris.

Claim 15

An elliptic filter as recited in claim 12 wherein said first cavity of the filter is connected to an input waveguide by a second reflective plate having a polarization discriminating coupling iris, and said second cavity of the filter is connected to an output waveguide by a third reflective plate having a polarization discriminating coupling iris.

Claim 16

A filter as recited in claim 9 wherein a plurality of said first and second waveguide cavities are connected in cascade and wherein said inductive coupling means includes a first means for directly connecting adjacent cavities and a second means for inter connecting selected cavities.