US3794935A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable equalizer
Assignee: NEC Corp
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Filing: 1972-05-30
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Granted: 1974-02-26
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Expires: 1992-05-30
Abstract
Abstract An equalizer, having a variable amplitude characteristic, for equalizing amplitude distortion especially in frequency-division multiplexed systems. The equalizer includes parallel signal paths, one path transmitting received signals essentially unchanged while the second path includes a circuit network having the transfer function tA (2 Alpha k/1 + Alpha k). The parallel paths are coupled to a subtraction circuit, the output of the subtraction circuit appearing as the output of equalizer. The ratio of the output signal V2 at the output of the subtraction circuit to the input signal V1 is equal to (1 Alpha k/1 + Alpha k). Various circuit arrangements which produce the transfer function TA are disclosed.
Inventors
- 👤 T Tsuchiya
- 👤 S Shida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 18:25
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/04; H04B3/14; H04B3/141
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
175 words
An equalizer of variable amplitude characteristic comprising: means for providing first and second analog signals derived from an input signal both proportional to said input signal to be equalized by said equalizer, said second analog signal having an amplitude substantially twice as great as said first analog signal; a two-terminal circuit and a variable resistance element connected to a common junction the real part of the admittance of said two terminal circuit having a predetermined frequency characteristic, said two-terminal circuit and variable resistance element being connected to the output of said second analog signal providing means; and means for providing a difference signal representative of the arithmetic difference in amplitude between said first analog signal and the analog signal obtained at said common junction of said variable resistance element and said two-terminal circuit; wherein the ratio of the voltage applied to said two-terminal circuit to that applied to said resistance element is changed by varying the resistance of said resistance element, thereby to obtain the output analog signal of said equalizer from said difference signal.
Claim 2
Dependent Claim
175 words
An equalizer of variable amplitude characteristic comprising: means for providing first and second analog signals derived from an input signal both proportional to said input signal to be equalized by said equalizer, said second analog signal having an amplitude substantially twice as great as said first analog signal; a two-terminal circuit and a variable resistance element connected to a common junction the real part of the admittance of said two terminal circuit having a predetermined frequency characteristic, said two-terminal circuit and variable resistance element being connected to the output of said second analog signal providing means; and means for providing a difference signal representative of the arithmetic difference in amplitude between said first analog signal and the analog signal obtained at said common junction of said variable resistance element and said two-terminal circuit; wherein the ratio of the voltage applied to said two-terminal circuit to that applied to said resistance element is changed by varying the resistance of said resistance element, thereby to obtain the output analog signal of said equalizer from said difference signal.
Claim 3
Dependent Claim
112 words
The equalizer of claim 1 wherein said analog signal obtained at said common junction is equal to the amplitude of the first analog signal multiplied by the transfer function given by the expression (2 Alpha k/1 + Alpha k,) where Alpha is a predetermined frequency dependent term and k is a real number variable coefficient whose absolute value is not greater than unity, and said variable resistance means being operative for varying the value of k, whereby the variable amplitude frequency characteristic of said equalizer is given by the subtraction of said second analog signal from said first analog signal, said variable amplitude frequency characteristic being substantially equal to 2k (in nepers).
Claim 4
Dependent Claim
26 words
The equalizer of claim 2 further comprising a plurality of parallel connected circuit means having the voltage transfer function TA (2 Alpha k/1 + Alpha k).
Claim 5
Dependent Claim
23 words
The equalizer of claim 2 wherein said means for providing a second analog signal comprises an amplifier with a gain of substantially two.
Claim 6
Dependent Claim
20 words
The equalizer of claim 4 wherein said two terminal circuit is comprised of a series connected inductance, capacitance and resistance.
Claim 7
Dependent Claim
132 words
The equalizer of claim 4 wherein said amplifier includes two outputs respectively providing a gain of substantially plus and minus two, said two terminal circuit including a series connected inductance and capacitance, said variable resistance circuit comprising a fixed resistor serially connected to a parallel circuit comprised of a first and second variable resistor, the circuit node between said fixed resistor and parallel circuit and being connected to said second input of said subtraction circuit, further including a first switch means selectively connecting the input of Said two terminal circuit to either of the two amplifier outputs and a second switch means selectively connecting the output of said two terminal circuit to either said fixed resistor or directly to the full value of one of the variable resistors of said parallel circuit.
Claim 8
Dependent Claim
82 words
The equalizer of claim 4 wherein said two terminal circuit coupled to said amplifier includes a series connected inductance and a capacitance, and said variable resistance circuit coupled to said two terminal circuit comprises a hybrid transformer having a primary winding coupled to the two terminal circuit, a secondary winding having a grounded center tap, and a fixed resistance and a variable resistance having their one end coupled together and their other ends coupled to the respective ends of the secondary winding.
Claim 9
Dependent Claim
20 words
The equalizer of claim 4 wherein said two terminal circuit is comprised of a parallel connected inductance, resistance and capacitance.
Claim 10
Dependent Claim
75 words
The equalizer of claim 4 wherein said two terminal circuit comprises a parallel connected inductance and capacitance and said variable resistance circuit comprises a hybrid transformer having a primary winding coupled to the amplifier output, a secondary winding having a grounded center tap, and a fixed resistance and a variable resistance having their one ends coupled together to the two terminal circuit and their other ends coupled to the respective ends of the secondary winding.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |