Crystal band pass filter circuit

Claim 2

A band pass filter circuit for passing frequencies within a predEtermined band pass comprising, input circuit means for receiving signals including signals which fall within the band pass of the filter circuit, first monolithic crystal-selecting means including a single crystal element having first and second pairs of electrodes thereon forming first and second coupled resonators, second monolithic crystal-selecting means including a single crystal element having third and fourth pairs of electrodes thereon forming third and forth coupled resonators, each resonator of said first and second monolithic crystalselecting means having the same resonant frequency, said input circuit means being coupled to said first pair of electrodes to apply signals to said first resonator, output circuit means coupled to said fourth pair of electrodes to receive from said fourth resonator signals of frequencies within the band pass of the filter circuit, and de-Qing circuit means coupled to said second and third pairs of electrodes for applying signals from said second resonator to said third resonator and including a first resistor connected between electrodes of said second and third pairs, a resistor connected across said electrodes of said second pair, a third resistor connected across said electrodes of said third pair, a first capacitor bridging said second resistor, and a second capacitor bridging said third resistor, said de-Qing circuit means reducing ringing effects through said resonators.

Claim 3

The band pass filter circuit of claim 1 wherein said first resistor has a value of 820 ohms and said second and third resistors each have a value of 15 k Omega and said first and second capacitors have a value of 1.5 pf.

Claim 4

The band pass filter circuit of claim 1 including a 0.24 pf. capacitor connected between said first and second pairs of electrodes to form a shunt coupling between said first and second coupled resonators.

Claim 5

The band pass filter circuit of claim 1 including a 0.39 pf. capacitor connected between said third and fourth pairs of electrodes to form a shunt coupling between said third and fourth coupled resonators.

Claim 6

A band pass filter circuit of claim 1 further including a first inductance element having one end thereof connected to said input circuit means and the other end thereof connected to a reference potential, a second inductance element having one end thereof connected to the output circuit means and the other end thereof connected to said reference potential, resistance means coupled in parallel with each of said first and second inductance elements, a first capacitive element connected between said input circuit means and said first pair of electrodes, and having a capacitance value with respect to said first inductance element and said associated resistance means to form a first impedance matching network, and a second capacitive element connected between said output circuit means and said fourth pair of electrodes and having a capacitance value with respect to said second inductance element and said associated resistance means to form a second impedance-matching network, whereby changes in impedance coupled to said input circuit means or said output circuit means are minimized by said first and second impedance-matching networks, respectively to prevent loading of said first and second monolithic crystal-selecting means.

Claim 7

A band-pass filter circuit for passing frequencies within a predetermined band pass comprising, input circuit means for receiving signals including signals which fall within the band-pass of the filter circuit, first monolithic crystal-selecting means including a single crystal element having first and second pairs of electrodes thereon forming first and second coupled resonators, second monolithic crystal-selecting means including a single crystal element having third and fourth pairs of electrodes thereon forming third and fourth coupled resonators, each resonator of said first and second monolithic crystal-selecting means having the same resonant frequency, saiD input circuit means being coupled to said first pair of electrodes to apply signals to said first resonator, amplifying circuit means having an input coupled to said fourth pair of electrodes to receive from said fourth resonator signals of frequencies within the band pass of the filter circuit, first de-Qing circuit means coupled to said second and third pairs of electrodes for applying signals from said second resonator to said third resonator and including a first resistor connected between electrodes of said second and third pairs, a second resistor connected across said electrodes of said second pair, a third resistor connected across said electrodes of said third pair, a first capacitor bridging said second resistor, and a second capacitor bridging said third resistor, said de-Qing circuit means reducing ringing effects through said first, second, third and fourth resonators, third monolithic crystal-selecting means including a single crystal element having fifth and sixth pairs of electrodes thereon forming fifth and sixth coupled resonators, fourth monolithic crystal-selecting means including a single crystal element having seventh and eighth pairs of electrodes thereon forming seventh and eighth coupled resonators, each resonator of said third and fourth monolithic crystal-selecting means having the same resonant frequency, said amplifying circuit means having an output coupled to said fifth pair of electrodes to apply signals to said third resonator, output circuit means coupled to said eighth pair of electrodes to receive from said eighth resonator signals of frequencies within the band pass of the filter circuit, and second de-Qing circuit means coupled to said sixth and seventh pairs of electrodes for applying signals from said sixth resonator to said seventh resonator and including a fourth resistor connected between electrodes of said sixth and seventh pairs, a fifth resistor connected across said electrodes of said sixth pair, a sixth resistor connected across said electrodes of said seventh pair, a third capacitor bridging said fifth resistor, and a fourth capacitor bridging said sixth resistor, said second de-Qing circuit means reducing ringing effects through said fifth, sixth, seventh and eighth resonators.

Claim 8

A band-pass filter circuit for passing frequencies within a predetermined band pass comprising, input circuit means for receiving signals including signals which fall within the band-pass of the filter circuit, first monolithic crystal-selecting means including a single crystal element having first and second pairs of electrodes thereon forming first and second coupled resonators, second monolithic crystal-selecting means including a single crystal element having third and fourth pairs of electrodes thereon forming third and fourth coupled resonators, each resonator of said first and second monolithic crystal-selecting means having the same resonant frequency, saiD input circuit means being coupled to said first pair of electrodes to apply signals to said first resonator, amplifying circuit means having an input coupled to said fourth pair of electrodes to receive from said fourth resonator signals of frequencies within the band pass of the filter circuit, first de-Qing circuit means coupled to said second and third pairs of electrodes for applying signals from said second resonator to said third resonator and including a first resistor connected between electrodes of said second and third pairs, a second resistor connected across said electrodes of said second pair, a third resistor connected across said electrodes of said third pair, a first capacitor bridging said second resistor, and a second capacitor bridging said third resistor, said de-Qing circuit means reducing ringing effects through said first, second, third and fourth resonators, third monolithic crystal-selecting means including a single crystal element having fifth and sixth pairs of electrodes thereon forming fifth and sixth coupled resonators, fourth monolithic crystal-selecting means including a single crystal element having seventh and eighth pairs of electrodes thereon forming seventh and eighth coupled resonators, each resonator of said third and fourth monolithic crystal-selecting means having the same resonant frequency, said amplifying circuit means having an output coupled to said fifth pair of electrodes to apply signals to said third resonator, output circuit means coupled to said eighth pair of electrodes to receive from said eighth resonator signals of frequencies within the band pass of the filter circuit, and second de-Qing circuit means coupled to said sixth and seventh pairs of electrodes for applying signals from said sixth resonator to said seventh resonator and including a fourth resistor connected between electrodes of said sixth and seventh pairs, a fifth resistor connected across said electrodes of said sixth pair, a sixth resistor connected across said electrodes of said seventh pair, a third capacitor bridging said fifth resistor, and a fourth capacitor bridging said sixth resistor, said second de-Qing circuit means reducing ringing effects through said fifth, sixth, seventh and eighth resonators.

Claim 9

The band pass filter circuit of claim 6 including a first shunting capacitor connected between said first and second coupled resonators and a second shunting capacitor connected between said seventh and eighth coupled resonators for shaping the band pass characteristic curve.

Claim 10

The band pass filter circuit of claim 7 wherein said first shunting capacitor is a 0.24 pf. capacitor and said second shunting capacitor is a 0.39 pf. capacitor.