US4875019A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Receiver preamplifier with tuned circuit adapted for Loran reception
Assignee: Bahr Technologies Inc
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Filing: 1988-07-21
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Granted: 1989-10-17
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Expires: 2008-07-21
Abstract
Abstract A preamplifier system adapted for a Loran receiver includes a buffer amplifier receiving the signal from the antenna at its input and a tuned circuit connected between the input of the buffer amplifier and ground. The tuned circuit includes a parallel combination of a resistance, capacitance and inductance with values selected such that a resonant frequency is provided substantially at or near the carrier frequency of the Loran signal to pass it while higher and lower frequencies, constituting extraneous noise signals, are substantially attenuated. In particular, low frequency, e.g. 60 Hz signals and DC from sources such as precipitation static, are shunted to ground through the parallel inductor in the tuned circuit so that these low frequency components do not affect the performance of the receiver. A secondary filter section is connected to the output of the buffer amplifier and has components that may be selected in value such that the overall transfer function of the preamplifier, including the tuned input circuit, has a desired bandpass characteristic. Thermal noise contributed by the parallel resistor in the tuned circuit may be reduced by feeding back the output of the buffer amplifier through the resistor to effectively reduce its noise contribution while leaving the effective input resistance the same. Notch filters may be incorporated with the input tuned circuit to reject strong extraneous signals within the passband.
Inventors
- 👤 Mark B. Monson
- 👤 Thomas P. Blandino
- 👤 Dennis E. Bahr
- 👤 Kendall E. Post
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 01:41
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/50; H03F1/00; H03F1/56; H03F1/565; H03F3/189; H03F3/19; H03F3/193; H03F3/1935; H03H; H03H11/00; H03H11/02; H03H11/04; H03H7/00; H03H7/01; H03H7/0115; H03F2203/00; H03F2203/50; H03F2203/5018; H03F2203/5036
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
140 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which will pass the carrier frequency of the particular signal to be received; and (d) a secondary filter section connected to the output of the buffer amplifier.
Claim 2
Dependent Claim
140 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which will pass the carrier frequency of the particular signal to be received; and (d) a secondary filter section connected to the output of the buffer amplifier.
Claim 3
Dependent Claim
41 words
The preamplifier system of claim 1 wherein the secondary filter section has filter components which are selected in value such that the overall filter characteristic of the preamplifier system including the the parallel tuned circuit provides a desired overall bandpass characteristic.
Claim 4
Dependent Claim
35 words
The preamplifier system of claim 1 including means for feeding back the output of the buffer/amplifier through the resistance of the tuned circuit to reduce the effective thermal noise contribution of the tuned circuit resistance.
Claim 5
Dependent Claim
75 words
The preamplifier system of claim 3 wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings and means for connecting the output signal from the buffer amplifier to the primary and for connecting the secondary to the tuned circuit resistance, and with the turns ratio of the transformer selected to provide a desired amplification of the voltage level of the output of the buffer amplifier.
Claim 6
Dependent Claim
31 words
The preamplifier system of claim 1 wherein the buffer amplifier comprises a junction field effect transistor with the input signal to the amplifier being provided to the gate of the transistor.
Claim 7
Dependent Claim
37 words
The preamplifier system of claim 1 wherein the input means includes a resistor connected in series from the antenna to the input to the buffer amplifier to add a pole outside the passband of the preamplifier system.
Claim 8
Dependent Claim
51 words
The preamplifier system of claim 1 wherein the tuned circuit inductance comprises an inductor connected between the input to the buffer amplifier and ground, and further including a notch filter connected to a tap in the tuned circuit inductor and having a notch frequency within the passband of the preamplifier system.
Claim 9
Dependent Claim
34 words
The preamplifier system of claim 4 further including a notch filter connected between the primary of the feedback transformer and ground and having a notch frequency within the passband of the preamplifier system. .
Claim 10
Dependent Claim
38 words
The preamplifier system of claim 4 further including a notch filter connected between the output of the buffer amplifier and the primary of the feedback transformer and having a notch frequency within the passband of the preamplifier system.
Claim 11
Dependent Claim
19 words
The preamplifier system of claim 7, 8, or 9 including means for increasing the Q of the notch filter.
Claim 12
Dependent Claim
32 words
The preamplifier system of claim 1 wherein the values of the tuned circuit inductance, capacitance and resistance are selected to provide a resonant frequency selected to pass the carrier frequency of LORAN-C.
Claim 13
Dependent Claim
89 words
The preamplifier system of claim 3 wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings and wherein the resistance of the tuned circuit is provided on the primary side of the transformer by a resistor connected between the output of the buffer amplifier and the primary of the transformer, and wherein the secondary of the transformer is connected to the input to the buffer amplifier, and wherein the inductance of the tuned circuit is provided by the transformer.
Claim 14
Dependent Claim
158 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which sill pass the carrier frequency of the particular signal to be received; and (d) means for feeding back the output of the buffer amplifier through the parallel resistance of the tuned circuit to reduce the effective thermal noise contribution of the tuned circuit resistant.
Claim 15
Dependent Claim
158 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which sill pass the carrier frequency of the particular signal to be received; and (d) means for feeding back the output of the buffer amplifier through the parallel resistance of the tuned circuit to reduce the effective thermal noise contribution of the tuned circuit resistant.
Claim 16
Dependent Claim
56 words
The preamplifier system of claim 13 wherein the resistance of the tuned circuit is provided by a resistor connected to the input of the buffer amplifier and wherein the means for feeding back the output of the buffer amplifier includes an operational amplifier connected between the output of the buffer amplifier and the tuned circuit resistor.
Claim 17
Dependent Claim
93 words
The preamplifier system of claim 13 wherein the resistance of the tuned circuit comprises a resistor connected to the input of the buffer amplifier and wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings, the secondary of the transformer connected to the tuned circuit resistor, and the primary of the transformer connected to the output of the buffer amplifier, the turns ratio of the transformer selected to provide a desired amplification of the voltage level of the output of the buffer amplifier.
Claim 18
Dependent Claim
44 words
The preamplifier system of claim 15 including amplification means, connected between the output of the buffer amplifier and the primary of the transformer, for providing output impedance isolation of the signal from the buffer amplifier before it supplied to the primary of the transformer.
Claim 19
Dependent Claim
89 words
The preamplifier system of claim 13 wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings and wherein the resistance of the tuned circuit is provided on the primary side of the transformer by a resistor connected between the output of the buffer amplifier and the primary of the transformer and wherein the secondary of the transformer is connected to the input to the buffer amplifier, and wherein the inductance of the tuned circuit is provided by the transformer.
Claim 20
Dependent Claim
33 words
The preamplifier system of claim 13 wherein the input means includes a resistor connected in series from the antenna to the input to the buffer amplifier to add a pole outside the passband.
Claim 21
Dependent Claim
43 words
The preamplifier system of claim 18 wherein the values of the tuned circuit inductance, capacitance and resistance are selected, with the resistance of the series resistor of the input means, to provide a resonant frequency which will pass the carrier frequency of LORAN-C.
Claim 22
Dependent Claim
51 words
The preamplifier system of claim 13 wherein the tuned circuit inductance comprises an inductor connected between the input to the buffer amplifier and ground, and further including a notch filter connected to a tap in the tuned circuit inductor and having a notch frequency within the passband of the preamplifier system.
Claim 23
Dependent Claim
32 words
The preamplifier system of claim 15 including a notch filter connected between the primary of the feedback transformer and ground and having a notch frequency within the passband of the preamplifier system.
Claim 24
Dependent Claim
38 words
The preamplifier system of claim 15 further including a notch filter connected between the output of the buffer amplifier and the primary of the feedback transformer and having a notch frequency within the passband of the preamplifier system.
Claim 25
Dependent Claim
31 words
The preamplifier system of claim 17 including a notch filter connected between the primary of the transformer and ground and having a notch frequency within the passband of the preamplifier system.
Claim 26
Dependent Claim
44 words
The preamplifier system of claim 17 including a notch filter connected in parallel with the resistor which is connected between the output of the buffer amplifier and the transformer primary, the notch filter having a notch frequency within the passband of the preamplifier system.
Claim 27
Dependent Claim
20 words
The preamplifier system of claim 20, 21, 22, 23 24 including means for increasing the Q of the notch filter.
Claim 28
Dependent Claim
148 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which will pass the carrier frequency of the particular signal to be received; and (d) a notch filter connected to the tuned circuit and having a notch frequency within the passband of the preamplifier system.
Claim 29
Dependent Claim
148 words
A preamplifier system for a receiver adapted to be connected to an antenna to receive a radio signal of a particular selected carrier frequency, such as a LORAN-C radio signal, and having a passband of frequencies which includes the selected carrier frequency, comprising: (a) input means for receiving the signal from the antenna; (b) a high input impedance buffer amplifier with an input and output and having its input connected to the input means; (c) a parallel tuned circuit connected between the input to the buffer amplifier and ground, the tuned circuit comprising the parallel combination of an inductance, capacitance and resistance, the values of which are selected to provide a resonant frequency which will pass the carrier frequency of the particular signal to be received; and (d) a notch filter connected to the tuned circuit and having a notch frequency within the passband of the preamplifier system.
Claim 30
Dependent Claim
36 words
The preamplifier system of claim 26 including means for feeding back the output of the buffer amplifier through the resistance of the tuned circuit to reduce the effective thermal noise contribution of the tuned circuit resistance.
Claim 31
Dependent Claim
56 words
The preamplifier system of claim 27 wherein the resistance of the tuned circuit is provided by a resistor connected to the input of the buffer amplifier and wherein the means for feeding back the output of the buffer amplifier comprises an operational amplifier connected between the output of the buffer amplifier and the tuned circuit resistor.
Claim 32
Dependent Claim
93 words
The preamplifier system of claim 27 wherein the resistance of the tuned circuit comprises a resistor connected to the input of the buffer amplifier and wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings, the secondary of the transformer connected to the tuned circuit resistor, and the primary of the transformer connected to the output of the buffer amplifier, the turns ratio of the transformer selected to provide a desired amplification of the voltage level of the output to the buffer amplifier.
Claim 33
Dependent Claim
44 words
The preamplifier system of claim 29 including amplification means, connected between the output of the buffer amplifier and the primary of the transformer, for providing output impedance isolation of the signal from the buffer amplifier before it supplied to the primary of the transformer.
Claim 34
Dependent Claim
88 words
The preamplifier system of claim 27 wherein the means for feeding back the output of the buffer amplifier includes a transformer having primary and secondary windings and wherein the resistance of the tuned circuit is provided on the primary side of the transformer by resistor connected between the output of the buffer amplifier and the primary of the transformer and wherein the secondary of the transformer is connected to the input of the buffer amplifier, and wherein the inductance of the tuned circuit is provided by the transformer.
Claim 35
Dependent Claim
33 words
The preamplifier system of claim 26 wherein the input means includes a resistor connected in series from the antenna to the input to the buffer amplifier to add a pole outside the passband.
Claim 36
Dependent Claim
43 words
The preamplifier system of claim 32 wherein the values of the tuned circuit inductance, capacitance and resistance are selected, with the resistance of the series resistor of the input means, to provide a resonant frequency which will pass the carrier frequency of LORAN-C.
Claim 37
Dependent Claim
51 words
The preamplifier system of claim 26 wherein the tuned circuit inductance comprises an inductor connected between the input to the buffer amplifier and ground, and further including a notch filter connected to a tap in the tuned circuit inductor and having a notch frequency within the passband of the preamplifier system.
Claim 38
Dependent Claim
32 words
The preamplifier system of claim 29 including a notch filter connected between the primary of the feedback transformer and ground and having a notch frequency within the passband of the preamplifier system.
Claim 39
Dependent Claim
37 words
The preamplifier system of claim 29 including a notch filter connected between the output of the buffer amplifier and the primary of the feedback transformer and having a notch frequency within the passband of the preamplifier system.
Claim 40
Dependent Claim
32 words
The preamplifier system of claim 31 including a notch filter connected between the primary of the feedback transformer and ground and having a notch frequency within the passband of the preamplifier system.
Claim 41
Dependent Claim
37 words
The preamplifier system of claim 31 including a notch filter connected between the output of the buffer amplifier and the primary of the feedback transformer and having a notch frequency within the passband of the preamplifier system.
Claim 42
Dependent Claim
21 words
The preamplifier system of claim 34, 35, 36, 37 or 38 including means for increasing the Q of the notch filter.
References Cited (Backward Citations)
US4559503A
Cited
US4814771A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-16 | 1993-04-17 | 1993-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-16 | 1997-04-17 | 1997-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-16 | 2001-04-17 | 2001-10-17 | $7700.00 | Window Closed / Lapsed |