Hybrid band pass-band stop filter

Claim 2

A hybrid filter comprising: a. a first common port; b. a band pass port; c. a band stop port; d. first band pass filter means electrically connecting said first common port and said band pass port, said first band pass filter means having a band pass frequency response for transmitting a range of frequencies from a low crossover frequency substantially greater than zero frequency to a high crossover frequency; e. first band stop filter means electrically connecting said first common port and said band stop port, said first band stop filter means having a band rejection frequency response for transmitting all frequencies except the range of frequencies transmitted by said first band pass filter means; and f. complementary filtering and phase inversion means electrically connecting said band pass port and said band stop port, said complementary filtering and phase inversion means providing cancellation of the effect of undesired frequencies.

Claim 3

The hybrid filter as recited in claim 1, wherein said complementary filtering and phase inversion means comprises: a. a second band pass filter means having a band pass frequency response substantially identical to the band pass frequency response of said first band pass filter means; b. a second band stop filter means having a band rejection frequency response substantially identical to the band rejection frequency response of said first band stop filter means; and c. means electrically connected between said second band pass filter means and second band stop filter means for phase inverting frequencies, said last-named means including a series circuit in which said second band pass filter means is electrically connected to said band stop port and said second band stop filter means is electrically connected to said band pass port.

Claim 4

The hybrid filter as recited in claim 2 wherein said means for phase inverting frequencies comprises a center-tapped inductor.

Claim 5

The hybrid filter as recited in claim 3, further including: a. a second common port; and b. said center-tapped inductor further including a magnetically coupled secondary winding electrically connected to said second common port.

Claim 6

The hybrid filter as recited in claim 2 wherein: a. said first and second band pass filter means each include a capacitor and an inductor connected in series; and b. said first and second band stop filter means each include a capacitor and an inductor connected in parallel.

Claim 7

The hybrid filter as recited in claim 5 wherein: a. the inductors and capacitors of said first and second band pass filter means have values of LS and CS, respectively; and b. the inductors and capacitors of said first and second band stop filter means havE values of LP and CP, respectively; where LS (R Square Root 2)/(2 pi (FH - FL))CS (FH - FL)/(FH . FL) . 1/(2 pi R Square Root 2)LP (FH - FL)/(FH . FL) . (R Square Root 2)/(2 pi ) CP 1/(2 pi R Square Root 2 (FH -FL)) R is a value of impedance characteristic of a transmission line to which the hybrid filter is adapted to be connected, FL is the low crossover frequency, and FH is the high crossover frequency.

Claim 8

The hybrid filter as recited in claim 2 wherein: a. said first and second band pass filter means comprise first and second band pass T filters, respectively, each band pass T filter having two series branches and a shunt branch; and b. said first and second band stop filter means comprise first and second band stop T filters, respectively, each band stop T filter having two series branches and a shunt branch.

Claim 9

The hybrid filter as recited in claim 7 wherein: a. each series branch of said first and second band pass T filter comprises an inductor of value LS and a capacitor of value CS connected in series; b. each shunt branch of said first and second band pass T filters comprises an inductor of value KLP and a capacitor of value CP/K connected in parallel; c. each series branch of said first and second band stop T filters comprises an inductor of value LP and a capacitor of value CP connected in parallel; and d. each shunt branch of said first and second band stop T filters comprises an inductor of value KLS and a capacitor of value CS/K connected in series; where K equals 0.34444, LS (R Square Root 2.4516316)/(2 pi (FH - FL))CS (FH - FL)/(FH . FL) . 1/(2 pi R Square Root 2.4516316 LP (FH - FL)/(FH . FL). (R Square Root 2.4516316 /(2 pi ) CP 1/( 2 pi R (FH - FL) Square Root 2.4516316) R is a value of impedance characteristic of a transmission line to which the hybrid filter is adapted to be connected, FL is the low crossover frequency, and FH is the high crossover frequency.

Claim 10

The hybrid filter as recited in claim 1 wherein said complementary filtering and phase inversion means comprises: a. a second common port; b. a second band stop filter means electrically connecting said band pass port and said second common port, said second band stop filter means having a band rejection frequency response substantially identical to the band rejection frequency response of said first band stop filter means; and c. means for band pass filtering and phase inverting which electrically connects said band stop port and second common port, said means for band pass filtering and phase inverting having a band pass frequency response substantially identical to the band pass frequency response of said first band pass filter means and further having the capability of phase inverting undesired frequencies.

Claim 11

The hybrid filter as recited in claim 9 wherein said first and second band stop filter means comprise first and second band stop T filters, each band stop T filter having two series branches and a shunt branch.

Claim 12

The hybrid filter as recited in claim 10 wherein said first band pass filter means comprises a first band pass T filter having two series branches and a shunt branch.

Claim 13

The hybrid filter as recited in claim 11 wherein said means for band pass filtering and phase inverting comprises: a. two series branches; and b. an intermediate network electrically connected between the two series branches; the intermediate network including a center-tapped inductor having first and second windings wound for phase inversion.

Claim 14

The hybrid filter as recited in claim 12 wherein: a. each series branch of said first and second band stop T filters comprises an inductor of value LP and a capacitor of value CP connected in parallel; b. each shunt branch of said first and second band stop T filters comprises an inductor of value KLS and a capacitor of value CS/K connected in series; c. each series branch of said first band pass T filter comprises an inductor of value LS and a capacitor of value CS connected in series; d. the shunt branch of said first band pass T filter comprises an inductor of value KLP and a capacitor of value CP/K connected in parallel; e. each series branch of said means for band pass filtering and phase inverting comprises an inductor of value LS and a capacitor of value CS connected in series; and f. the intermediate network of said means for band pass filtering and phase inverting further includes two capacitors of value CP/2K, one capacitor being connected in parallel with the first winding and the other capacitor being connected in parallel with the second winding, the first and second winding having a shunt inductance of value KLP; where K equals 0.34444, LS (R Square Root 2.4516316)/(2 pi (FH - FL))CS (FH - FL)/(FH .FL). 1/(2 pi R Square Root 2.4516316)LP (FH - FL)/(FH .FL).(R Square Root 2.4516316))/ (2 pi )CP 1 /( 2 pi R (FH - FL ) Square Root 2.4516316) R is a value of impedance characteristic of a transmission line to which the hybrid filter is adapted to be connected, FL is the low crossover frequency, and FH is the high crossover frequency.

Claim 15

The hybrid filter as recited in claim 10 where said first band pass filter means and said means for band pass filtering and phase inverting each comprise: a. two series branches; and b. an intermediate network electrically connected between the two series branches, the intermediate network of said first band pass filter means including a center-tapped inductor having first and second windings wound for in-phase signal transmission, and further having a predetermined coupling coefficient, and the intermediate network of said means for filtering and phase inverting including a center-tapped inductor having first and second windings wound for phase inversion, and further having a coupling coefficient substantially identical to the coupling coefficient of the center-tapped inductor of said first band pass filter means.

Claim 16

The hybrid filter as recited in claim 14 wherein: a. each series branch of said first and second band stop T filters comprises an inductor of value LP and a capacitor of value CP connected in parallel; b. each shunt branch of said first and second band stop T filters comprises an inductor of value KLS and a capacitor of value CS/K connected in series; c. each series branch of said first band pass filter means and of said means for band pass filtering and phase inverting comprises an inductor of value LS and a capacitor of value CS connected in series; d. each intermediate network of said first band pass filter means and said means for band pass filtering and phase inverting further includes two capacitors of value CP/2K, one capacitor being connected in parallel with the first winding of each center-tapped inductor and the other capacitor being connected in parallel with the second winding of each center-tapped inductor, the first and second windings of both cenTer-tapped inductors having a shunt inductance of value KLP; where K equals 0.34444 LS (R Square Root 2.4516316)/( 2 pi (FH - FL))CS (FH - FL)/(FH .FL). 1/( 2 pi R Square Root 2.4516316)LP (FH .FL)/(FH .FL). (R Square Root 2.4516316)/(2 pi ) CP 1 /(2 pi R (FH - FL) Square Root 2.4516316) R is the value of impedance characteristic of a transmission line to which the hybrid filter is adapted to be connected, FL is the low crossover frequency, and FH is the high crossover frequency.