EP0416622A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Predistorter for linearization of electronic and optical signals
Assignee: Ortel Corp
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Filing: 1990-09-06
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Granted: —
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Expires: 2010-09-06
Abstract
Abstract An electronic circuit provides a linear output from an amplitude modulated transmission device such as a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two paths with primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. A distortion generator in the secondary path generates intermodulation signals, the amplitude of which is adjusted to match the amplitude of the distortion of the nonlinear device. A tilt adjustment is made to compensate the amplitude of the predistortion for frequency dependence of the amplitude of the distortion. A adjustment of the predistortion signal is also included so that phase of the distortion signal generated is in proper phase relation with the distortion inherent in the nonlinear device. A push-push amplifier is used as a distortion generator, with bias current unbalanced to produce net odd order intermodulation products as well as even order intermodulation products of the fundamental frequencies.
Inventors
- 👤 Henry A. Blauvelt
- 👤 Howard L. Loboda
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 15:22
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/50; H04B10/501; H04B10/503; H04B10/504; H03; H03F; H03F1/00; H03F1/32; H03F1/3241; H03F1/3252; H04B1/00; H04B1/62; H04B10/58
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
142 words
A predistortion circuit comprising: means for splitting an input modulation signal for a nonlinear device into a primary electrical path and a secondary electrical path; means for generating at least second order intermodulation products in the secondary electrical path having a relative amplitude corresponding to the amplitude of distortion in the nonlinear device; filtering means in series with the means for generating intermodulation products for adjusting the amplitude of the signal on the secondary electrical path as a function of frequency for providing frequency dependent predistortion on the secondary path; means for adjusting the relative phase of the intermodulation products and the distortion of the nonlinear device; and means for additively recombining the primary and secondary paths into a single path to form a signal composed of the fundamental signal and frequency dependent intermodulation product predistortion for application to the nonlinear device.
Claim 2
Dependent Claim
142 words
A predistortion circuit comprising: means for splitting an input modulation signal for a nonlinear device into a primary electrical path and a secondary electrical path; means for generating at least second order intermodulation products in the secondary electrical path having a relative amplitude corresponding to the amplitude of distortion in the nonlinear device; filtering means in series with the means for generating intermodulation products for adjusting the amplitude of the signal on the secondary electrical path as a function of frequency for providing frequency dependent predistortion on the secondary path; means for adjusting the relative phase of the intermodulation products and the distortion of the nonlinear device; and means for additively recombining the primary and secondary paths into a single path to form a signal composed of the fundamental signal and frequency dependent intermodulation product predistortion for application to the nonlinear device.
Claim 3
Dependent Claim
29 words
A predistortion circuit as claimed in claim 1 comprising time delay means in the primary electrical path for compensating relative phase difference between the primary and secondary electrical paths.
Claim 4
Dependent Claim
37 words
A predistortion circuit as claimed in claim 1 or 2 further comprising means in series with the other elements in the secondary electrical path for compensating relative phase difference between the secondary path and the nonlinear device.
Claim 5
Dependent Claim
28 words
A predistortion circuit as claimed in at least one of claims 1 to 3 wherein the primary electrical path carries a major portion of the input signal power.
Claim 6
Dependent Claim
25 words
A predistortion circuit as claimed in at least one of claims 1 to 4 wherein the means for generating intermodulation products comprises a push-push amplifier.
Claim 7
Dependent Claim
120 words
A predistortion circuit as claimed in at least one of claims 1 to 5 wherein the push-push amplifier comprises: means for splitting the input signal into first and second electrical paths, said signals being equal in magnitude and opposite in sign; first amplification means in the first electrical path for generating positive intermodulation products of the signal carried on the path; second amplification means in the second electrical path for generating positive even order intermodulation products and negative odd order intermodulation products of the signal carried on the path; and signal combining means for additively recombining the first and second electrical paths after the intermodulation products have been generated, thereby at least partially cancelling the odd order intermodulation product components.
Claim 8
Dependent Claim
54 words
A predistortion circuit as claimed in at least one of claims 1 to 6 wherein the push-push amplifier further includes biasing means for unbalancing the first and second amplification means such that cancellation of the odd order intermodulation products is not complete, thereby producing a predistortion signal comprising even and odd order intermodulation products.
Claim 9
Dependent Claim
53 words
A predistortion circuit as claimed in at least one of claims 1 to 7 wherein the biasing means includes a first sense of adjustment to the bias current of the first amplification means and an opposite sense of adjustment to the second amplification means for maintaining substantially constant magnitude even order intermodulation products.
Claim 10
Dependent Claim
29 words
A predistortion circuit as claimed in at least one of claims 1 to 8 further comprising filtering means in series with each amplification means for suppressing the fundamental frequencies.
Claim 11
Dependent Claim
27 words
A predistortion circuit as claimed in at least one of claims 1 to 9 wherein the filtering means is integral with the first and second amplification means.
Claim 12
Dependent Claim
30 words
A predistortion circuit as claimed in at least one of claims 1 to 10 comprising means in the secondary electrical path for suppressing the fundamental frequencies of the modulation signal.
Claim 13
Dependent Claim
26 words
A predistortion circuit as claimed in at least one of claims 1 to 11 wherein the means for suppressing comprises the first and second amplification means.
Claim 14
Dependent Claim
119 words
A predistortion circuit comprising: a first directional coupler for splitting an input modulation signal into primary and secondary electrical paths; a distortion amplifier in series with the secondary electrical path for producing at least second order intermodulation products of the input frequencies; a time delay in the primary electrical path for reducing the relative phase difference between the primary and secondary electrical paths; a second directional coupler for recombining the primary and secondary signal paths into a single signal for modulating a nonlinear device with predictable distortion characteristics; and a time delay in one of the electrical paths for compensating relative phase difference between the intermodulation products in the secondary electrical path and the distortion of the nonlinear device.
Claim 15
Dependent Claim
119 words
A predistortion circuit comprising: a first directional coupler for splitting an input modulation signal into primary and secondary electrical paths; a distortion amplifier in series with the secondary electrical path for producing at least second order intermodulation products of the input frequencies; a time delay in the primary electrical path for reducing the relative phase difference between the primary and secondary electrical paths; a second directional coupler for recombining the primary and secondary signal paths into a single signal for modulating a nonlinear device with predictable distortion characteristics; and a time delay in one of the electrical paths for compensating relative phase difference between the intermodulation products in the secondary electrical path and the distortion of the nonlinear device.
Claim 16
Dependent Claim
49 words
A predistortion circuit as claimed in claim 13 further comprising filter means in the secondary electrical path for adjusting the relative amplitude and phase of the signal as a function of frequency such that the modulation signal is predistorted for offsetting a frequency dependent distortion of the nonlinear device.
Claim 17
Dependent Claim
38 words
A predistortion circuit as claimed in claim 13 or 14 wherein the input signal is split into a plurality of secondary paths, each path comprising means for generating one or more intermodulation products of the input modulation signal.
Claim 18
Dependent Claim
22 words
A predistortion circuit as claimed in at least one of claims 13 to 15 wherein the distortion amplifier is a push-push amplifier.
Claim 19
Dependent Claim
47 words
A predistortion circuit as claimed in at least one of claims 13 to 16 wherein the push-push amplifier includes biasing means for unbalancing the amplifier so that odd order intermodulation products are not entirely cancelled, thereby producing a predistortion signal comprising even and odd order intermodulation products.
Claim 20
Dependent Claim
28 words
A predistortion circuit as claimed in at least one of claims 13 to 17 wherein the primary electrical path carries a major portion of the input signal power.
Claim 21
Dependent Claim
29 words
A predistortion circuit as claimed in at least one of claims 13 to 18 further comprising filtering means in series with each amplification means for suppressing the fundamental frequencies.
Claim 22
Dependent Claim
150 words
An amplifier for producing intermodulation products of frequencies in an input signal comprising: means for splitting the input signal into first and second electrical paths, said signals being equal in magnitude and opposite in sign; first amplification means in the first electrical path for generating positive intermodulation products of the signal carried on the path; second amplification means in the second electrical path for generating positive even order intermodulation products and negative odd order intermodulation products of the signal carried on the second path; signal combining means for additively recombining the first and second electrical paths after the intermodulation products have been produced, thereby cancelling at least a portion of the odd order intermodulation product components; and biasing means for unbalancing the first and second amplification means such that cancellation of the odd order intermodulation products is not complete, thereby producing a signal comprising even and odd order intermodulation products.
Claim 23
Dependent Claim
150 words
An amplifier for producing intermodulation products of frequencies in an input signal comprising: means for splitting the input signal into first and second electrical paths, said signals being equal in magnitude and opposite in sign; first amplification means in the first electrical path for generating positive intermodulation products of the signal carried on the path; second amplification means in the second electrical path for generating positive even order intermodulation products and negative odd order intermodulation products of the signal carried on the second path; signal combining means for additively recombining the first and second electrical paths after the intermodulation products have been produced, thereby cancelling at least a portion of the odd order intermodulation product components; and biasing means for unbalancing the first and second amplification means such that cancellation of the odd order intermodulation products is not complete, thereby producing a signal comprising even and odd order intermodulation products.
Claim 24
Dependent Claim
62 words
An amplifier as claimed in claim 20 wherein the biasing means includes means for increasing a bias current for either the first or second amplification means and means for proportionally decreasing the bias current for the other amplification means such that the odd order intermodulation products are prevented from cancelling and the even order intermodulation products do not change substantially in magnitude.
Claim 25
Dependent Claim
155 words
A distortion amplifier for producing second order and higher order intermodulation products of an input frequency comprising: a 180° splitter dividing a source signal into first and second electrical paths, the signal on the first path being equal in magnitude and opposite in sign to the signal on the second path; first and second amplification means in each of the first and the second electrical paths, respectively, for generating intermodulation products of the input signal of substantially equal magnitude, such that the even and odd order intermodulation products so generated are opposite in sign; a zero-degree combiner additively recombining the first and second electrical paths after the intermodulation products have been generated, thereby cancelling the fundamental and odd order intermodulation product components; and biasing means for unbalancing the first and second amplification means such that the odd order intermodulation products are not entirely cancelled, thereby producing a signal comprising even and odd order intermodulation products.
Claim 26
Dependent Claim
155 words
A distortion amplifier for producing second order and higher order intermodulation products of an input frequency comprising: a 180° splitter dividing a source signal into first and second electrical paths, the signal on the first path being equal in magnitude and opposite in sign to the signal on the second path; first and second amplification means in each of the first and the second electrical paths, respectively, for generating intermodulation products of the input signal of substantially equal magnitude, such that the even and odd order intermodulation products so generated are opposite in sign; a zero-degree combiner additively recombining the first and second electrical paths after the intermodulation products have been generated, thereby cancelling the fundamental and odd order intermodulation product components; and biasing means for unbalancing the first and second amplification means such that the odd order intermodulation products are not entirely cancelled, thereby producing a signal comprising even and odd order intermodulation products.
Claim 27
Dependent Claim
86 words
An amplifier as claimed in claim 22 wherein the biasing means includes first means for increasing a bias current for either the first or second amplification means and second means for decreasing the bias current for the other amplification means, the first and second bias current means being sufficiently matched that the even order intermodulation products generated do not change substantially in magnitude and the odd order intermodulation products generated from the first and second amplification means are unequal in magnitude and thereby do not cancel.
Claim 28
Dependent Claim
19 words
A distortion amplifier as claimed in claim 22 or 23 further comprising filtering means for suppressing the fundamental frequency.
Claim 29
Dependent Claim
30 words
A distortion amplifier as claimed in at least one of claims 22 to 24 comprising means in the secondary electrical path for suppressing the fundamental frequencies of the modulation signal.
Claim 30
Independent Claim
148 words
The method of reducing distortion in an amplitude modulated signal from a nonlinear modulating device comprising the steps of: splitting an input modulation signal into primary and secondary electrical paths; generating at least second order intermodulation distortion in the secondary electrical path and adjusting the magnitude of the intermodulation distortion to be equal in magnitude and opposite in sign to distortion inherent in a nonlinear modulating device; adjusting the amplitude and phase of the intermodulation distortion in the secondary electrical path as a function of frequency to match the frequency dependence of distortion inherent in the modulating device; adjusting the phase of the signal in the primary electrical path to match the phase of the final signal in the secondary electrical path; and recombining the primary and secondary electrical signals for providing an output signal with frequency dependent intermodulation predistortion for cancelling distortion in the nonlinear modulating device.
Claim 31
Independent Claim
148 words
The method of reducing distortion in an amplitude modulated signal from a nonlinear modulating device comprising the steps of: splitting an input modulation signal into primary and secondary electrical paths; generating at least second order intermodulation distortion in the secondary electrical path and adjusting the magnitude of the intermodulation distortion to be equal in magnitude and opposite in sign to distortion inherent in a nonlinear modulating device; adjusting the amplitude and phase of the intermodulation distortion in the secondary electrical path as a function of frequency to match the frequency dependence of distortion inherent in the modulating device; adjusting the phase of the signal in the primary electrical path to match the phase of the final signal in the secondary electrical path; and recombining the primary and secondary electrical signals for providing an output signal with frequency dependent intermodulation predistortion for cancelling distortion in the nonlinear modulating device.
Claim 32
Dependent Claim
77 words
A method as recited in claim 26 wherein the intermodulation distortion is made substantially equal in magnitude to the distortion of the nonlinear modulating device at a relatively lower frequency, and tilt is adjusted to make the intermodulation distortion generated at a relatively higher frequency substantially equal in magnitude to the distortion of the nonlinear modulating device at the relatively higher frequency without substantially changing the magnitude of the intermodulation distortion generated at the relatively lower frequency.
Claim 33
Dependent Claim
45 words
A method as recited in claim 26 or 27 wherein the time delay of the signal in one of the paths is adjusted at a relatively higher frequency to be 180° out of phase with the distortion of the nonlinear device at the higher frequency.
Claim 34
Independent Claim
31 words
A method as claimed in at least one of claims 26 to 28 further comprising the step of suppressing the fundamental frequencies of the modulated signal in the secondary electrical path.
References Cited (Backward Citations)
No citation records indexed.
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