US6566944B1
Expired / Lapsed
US
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Current modulator with dynamic amplifier impedance compensation
Assignee: Ericsson Inc
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Filing: 2002-02-21
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Granted: 2003-05-20
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Expires: 2022-02-21
Abstract
Abstract An amplitude modulation circuit (modulator) provides modulated supply current, possibly in combination with modulated supply voltage, to a radio frequency (RF) power amplifier (PA), and includes a detection circuit responsive to changes in the ratio of that voltage to the modulated supply current, described herein as its AM modulation impedance. Such impedance (resistance) changes commonly arise from changing coupling characteristics at the RF antenna assembly driven by the PA. A gain control circuit may be associated with the detection circuit, and made responsive thereto, thus allowing adjustment of modulation gain control responsive to changes in PA AM modulation impedance. In one embodiment, this arrangement permits the modulator to hold a fixed modulation gain over changing PA AM modulation impedance, while in other embodiments, modulation gain varies in response to PA impedance changes to avoid signal clipping. Such clipping might otherwise occur where current modulation values in combination with increased PA resistance would result in PA voltages exceeding the supply voltage of the PA.
Inventors
- 👤 David R. Pehlke
- 👤 Aristotele Hadjichristos
- 👤 William O. Camp, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:33
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/02; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3036; H03G3/3042; H03G3/3047; H03F1/0205; H03F1/0211; H03F1/0216; H03F1/0233; H03F1/0261; H03F1/0272; H03F1/56; H03G3/004; H03F2200/00; H03F2200/504
Claims Analysis
Total Claims: 71
Claim 1
Independent Claim
132 words
A current modulator to supply a modulated supply current to a power amplifier responsive to an amplitude modulation signal, the current modulator comprising: a modulation control circuit generating a modulation control signal responsive to the amplitude modulation signal; an output circuit generating the modulated supply current responsive to the modulation control signal; a reference circuit generating a reference current proportional to the modulated supply current, and including a reference control element responsive to an inferential sense signal to maintain the reference current at a known proportionality relative to the modulated supply current; and a detection circuit generating the inferential sense signal as a function of an operating voltage of the power amplifier and the reference current such that the inferential sense signal varies in dependence on power amplifier (PA) AM modulation impedance.
Claim 2
Dependent Claim
132 words
A current modulator to supply a modulated supply current to a power amplifier responsive to an amplitude modulation signal, the current modulator comprising: a modulation control circuit generating a modulation control signal responsive to the amplitude modulation signal; an output circuit generating the modulated supply current responsive to the modulation control signal; a reference circuit generating a reference current proportional to the modulated supply current, and including a reference control element responsive to an inferential sense signal to maintain the reference current at a known proportionality relative to the modulated supply current; and a detection circuit generating the inferential sense signal as a function of an operating voltage of the power amplifier and the reference current such that the inferential sense signal varies in dependence on power amplifier (PA) AM modulation impedance.
Claim 3
Dependent Claim
30 words
The current modulator of claim 1 , wherein the output circuit comprises an output transistor deriving the modulated supply current from a supply voltage responsive to the modulation control signal.
Claim 4
Dependent Claim
36 words
The current modulator of claim 2 , wherein the reference circuit includes a reference transistor controlling the reference current responsive to the modulation control signal, and having a known geometric scaling relative to the output transistor.
Claim 5
Dependent Claim
48 words
The current modulator of claim 3 wherein the reference control element controls an operating condition of the reference transistor to vary identically with a corresponding operating condition of the output transistor, such that the reference current is maintained at the known proportionality relative to the modulated supply current.
Claim 6
Dependent Claim
19 words
The current modulator of claim 4 wherein the reference control element controls an operating voltage of the reference transistor.
Claim 7
Dependent Claim
73 words
The current modulator of claim 5 , wherein the reference control element comprises a control transistor disposed in series with the reference transistor, and configured as a variable resistor responsive to the inferential sense signal, to vary the operating voltage of the reference transistor with changes in a corresponding operating voltage of the output transistor such that the operating voltage of the reference transistor remains equal to operating voltage of the output transistor.
Claim 8
Dependent Claim
20 words
The current modulator of claim 6 wherein the operating voltage of the reference transistor is generated by the reference current.
Claim 9
Dependent Claim
55 words
The current modulator of claim 6 , wherein the reference transistor includes a first signal terminal coupled to the supply voltage, a second signal terminal coupled to the control transistor, and a control terminal coupled to the modulation control circuit such that the reference transistor varies the reference current responsive to the modulation control signal.
Claim 10
Dependent Claim
23 words
The current modulator of claim 8 wherein the control transistor controls the operating voltage of the reference transistor at the second signal terminal.
Claim 11
Dependent Claim
59 words
The current modulator of claim 9 , wherein the output transistor includes a first signal terminal coupled to a supply voltage, a second signal terminal coupled to a supply input of the power amplifier, and a control terminal coupled to the modulation control circuit such that the reference transistor varies the reference current responsive to the modulation control signal.
Claim 12
Dependent Claim
24 words
The current modulator of claim 10 wherein the operating voltage of the reference transistor is equal to the supply voltage to the power amplifier.
Claim 13
Dependent Claim
51 words
The current modulator of claim 6 , wherein the detection circuit comprises a differential amplifier circuit connected between the output circuit and the reference circuit to generate the inferential sense signal based on a difference between the operating voltage of the reference transistor and the operating voltage of the output transistor.
Claim 14
Dependent Claim
35 words
The current modulator of claim 12 , wherein the differential amplifier circuit includes a feedback loop closed through the reference control element such that the variable resistor varies responsive to changes in the PA resistance.
Claim 15
Dependent Claim
44 words
The current modulator of claim 6 , wherein the modulation control circuit comprises a differential amplifier circuit generating the modulation control signal based on the difference between a feedback voltage derived from the operating voltage of the reference transistor and the amplitude modulation signal.
Claim 16
Dependent Claim
42 words
The current modulator of claim 14 , wherein a feedback loop of the differential amplifier circuit is closed around the reference control element such that a control gain of the differential amplifier varies as a function of the PA AM modulation impedance.
Claim 17
Dependent Claim
25 words
The current modulator of claim 1 wherein the detection circuit generates a compensation control signal that varies with changes in power amplifier AM modulation impedance.
Claim 18
Dependent Claim
36 words
The current modulator of claim 16 further comprising a compensation controller responsive to the compensation control signal from the detection circuit to generate a compensation signal that compensates for changes in power amplifier AM modulation impedance.
Claim 19
Dependent Claim
30 words
The current modulator of claim 17 wherein the compensation controller comprises a modulation gain control circuit to vary a modulation gain of the modulation circuit responsive to the compensation signal.
Claim 20
Dependent Claim
57 words
The current modulator of claim 18 wherein the modulation gain control circuit comprises a peak detector to generate the compensation signal responsive to the compensation control signal and a resistor network coupled to the modulation control circuit to provide a variable effective resistance to the modulation control circuit responsive to the compensation signal from the peak detector.
Claim 21
Dependent Claim
23 words
The current modulator of claim 17 wherein the compensation controller controls scaling of the amplitude modulation signal responsive to the compensation control signal.
Claim 22
Dependent Claim
31 words
The current modulator of claim 17 wherein the compensation control circuit generates a compensation signal to adjust the impedance of a matching network coupled to the output of the power amplifier.
Claim 23
Dependent Claim
45 words
The current modulator of claim 1 , further comprising a bias controller to generate a bias voltage for biasing the power amplifier such that quiescent supply current provided to the power amplifier by the current modulator under quiescent conditions equals a desired quiescent current value.
Claim 24
Dependent Claim
56 words
The current modulator of claim 22 , wherein the bias controller comprises: a detection circuit to generate a sense signal proportional to quiescent supply current into the power amplifier; a closed loop control circuit to adjust the bias voltage applied to the power amplifier such that the quiescent supply current equals the desired quiescent current value.
Claim 25
Dependent Claim
81 words
The current modulator of claim 23 , wherein the closed loop control circuit of the bias controller comprises: an error amplifier to generate an error signal based on a difference between the sense signal and a quiescent current reference voltage representing the desired quiescent current value; and a track-and-hold circuit adjusting the bias voltage responsive to the error signal in a first state, and holding an adjusted level of the bias voltage in a second state irrespective of the error signal.
Claim 26
Dependent Claim
42 words
The current modulator of claim 24 , wherein the bias controller further comprises a timing function generating a bias calibration pulse, and wherein the track-and-hold circuit operates in one of the first and second states in dependence upon the bias calibration pulse.
Claim 27
Dependent Claim
41 words
The current modulator of claim 25 , wherein the bias controller further comprises an input control switch responsive to the bias calibration pulse to decouple the current modulation control circuit from the amplitude modulation signal during adjustment of the bias voltage.
Claim 28
Dependent Claim
33 words
The current modulator of claim 25 , wherein the bias controller further comprises a gain control circuit to selectively adapt the modulation control gain of the current modulator to facilitate bias voltage adjustment.
Claim 29
Dependent Claim
36 words
The current modulator of claim 25 , wherein the gain control circuit is responsive to the bias calibration pulse such that the modulation control gain of the current modulator is adapted during the bias calibration pulse.
Claim 30
Dependent Claim
85 words
The current modulator of claim 25 , wherein the current modulator includes a first feedback loop coupling a feedback control input of the modulation control circuit to an output of the current modulator, such that the first feedback loop provides supply voltage modulation feedback, and further includes a second feedback loop coupling the feedback control input of the modulation control circuit to a feedback voltage in the reference circuit responsive to the reference current, such that the second feedback loop provides supply current modulation feedback.
Claim 31
Dependent Claim
35 words
The current modulator of claim 29 , wherein the bias controller further includes a feedback switching circuit for selectively decoupling the second feedback loop from the current modulation control circuit during the bias calibration pulse.
Claim 32
Dependent Claim
40 words
The current modulator of claim 24 , wherein the bias controller includes switching circuits responsive to a transmit enable pulse, such that the modulation control circuit is de-coupled from the amplitude modulation signal during assertion of the transmit enable pulse.
Claim 33
Dependent Claim
48 words
The current modulator of claim 31 , wherein the switching circuits further enable the track-and-hold circuit during assertion of the transmit enable pulse to allow dynamic adjustment of the bias voltage responsive to differences between the quiescent current reference voltage and the detection signal during RF transmit operations.
Claim 34
Dependent Claim
36 words
The current modulator of claim 32 , further comprising a quiescent current reference voltage controller to dynamically control RF transmit power during the transmit operations by dynamically controlling a magnitude of the quiescent current reference voltage.
Claim 35
Dependent Claim
138 words
In a current modulator supplying a modulated current to a power amplifier, a method of inferentially sensing power amplifier (PA) AM modulation impedance in a current modulator where a power amplifier is supplied with a modulated supply current, the method comprising: generating said modulated supply current in an output circuit responsive to an amplitude modulation signal; generating a reference current in a reference circuit proportional to the modulated supply current; and slaving an operating voltage of the reference circuit generated by the reference current to an operating voltage of power amplifier such that the reference current is maintained at a known proportionality relative to the modulated supply current irrespective of changes in the PA AM modulation impedance; and generating an inferential sense signal as a function of the operating voltage of the power amplifier and the reference current.
Claim 36
Dependent Claim
138 words
In a current modulator supplying a modulated current to a power amplifier, a method of inferentially sensing power amplifier (PA) AM modulation impedance in a current modulator where a power amplifier is supplied with a modulated supply current, the method comprising: generating said modulated supply current in an output circuit responsive to an amplitude modulation signal; generating a reference current in a reference circuit proportional to the modulated supply current; and slaving an operating voltage of the reference circuit generated by the reference current to an operating voltage of power amplifier such that the reference current is maintained at a known proportionality relative to the modulated supply current irrespective of changes in the PA AM modulation impedance; and generating an inferential sense signal as a function of the operating voltage of the power amplifier and the reference current.
Claim 37
Dependent Claim
70 words
The method of claim 34 wherein slaving an operating voltage of the reference circuit generated by the reference current to an operating voltage of power amplifier comprises controlling an operating voltage of the reference circuit so as to maintain a fixed relation between the operating voltage of the reference circuit and a corresponding operating voltage in the output circuit that is dependent on the operating voltage of the power amplifier.
Claim 38
Dependent Claim
41 words
The method of claim 35 wherein slaving an operating voltage of the reference circuit generated by the reference current to an operating voltage of power amplifier further comprises varying a resistance in the reference circuit responsive to the inferential sense signal.
Claim 39
Dependent Claim
53 words
The method of claim 36 wherein varying a resistance in the reference circuit responsive to the inferential sense signal comprises configuring a control transistor as a variable resistor responsive to the inferential sense signal such that the effective resistance of the control transistor varies responsive to the operating voltage of the power amplifier.
Claim 40
Dependent Claim
57 words
The method of claim 34 wherein generating an inferential sense signal as a function of an operating voltage of the power amplifier and the reference current comprises generating the inferential sense signal in a differential amplifier circuit based on a difference between the operating voltage of the reference circuit to the operating voltage of the output circuit.
Claim 41
Dependent Claim
58 words
The method of claim 34 wherein generating the modulated supply current in an output circuit responsive to an amplitude modulation signal comprises generating a modulation control signal in a modulation control circuit and coupling the modulation control circuit to the output circuit such that the output circuit varies the modulated supply current responsive to the modulation control signal.
Claim 42
Dependent Claim
49 words
The method of claim 39 wherein generating a modulation control signal in a modulation control circuit comprises generating the modulation control signal in a differential amplifier circuit based on a difference between the amplitude modulation signal and a feedback signal derived from the operating voltage of the reference circuit.
Claim 43
Dependent Claim
44 words
The method of claim 40 further comprising varying a resistance of the reference circuit responsive to the inferential sense signal to maintain a fixed control gain in the modulation control circuit irrespective of changes in the PA AM modulation impedance of the power amplifier.
Claim 44
Dependent Claim
24 words
The method of claim 34 further comprising generating a compensation control signal responsive to changes in the AM modulation impedance of the power amplifier.
Claim 45
Dependent Claim
30 words
The method of claim 42 further comprising varying a modulation gain of the current modulator responsive to the compensation control signal to compensate for changes in PA AM modulation impedance.
Claim 46
Dependent Claim
37 words
The method of claim 43 wherein varying a modulation gain of the current modulator responsive to the inferential sense signal comprises varying a resistance of the current modulator to change the modulation gain of the current modulator.
Claim 47
Dependent Claim
28 words
The method of claim 42 further comprising adjusting an impedance of a matching network coupled to an output of the power amplifier responsive to the compensation control signal.
Claim 48
Dependent Claim
18 words
The method of claim 34 further comprising scaling the amplitude modulation signal responsive to the inferential sense signal.
Claim 49
Dependent Claim
127 words
A current modulator to supply a modulated supply current to a power amplifier responsive to an amplitude modulation signal, the current modulator comprising: an output circuit generating the modulated supply current responsive to the amplitude modulation signal; a reference circuit generating a reference current proportional to the modulated supply current, said reference circuit including an operating voltage generated by the reference current and slaved to an operating voltage of the power amplifier such that the reference current is maintained at a known proportionality relative to the modulated supply current; and a detection circuit generating an inferential sense signal as a function of an operating voltage of the power amplifier and the reference current such that the inferential sense signal varies in dependence on power amplifier (PA) impedance.
Claim 50
Dependent Claim
127 words
A current modulator to supply a modulated supply current to a power amplifier responsive to an amplitude modulation signal, the current modulator comprising: an output circuit generating the modulated supply current responsive to the amplitude modulation signal; a reference circuit generating a reference current proportional to the modulated supply current, said reference circuit including an operating voltage generated by the reference current and slaved to an operating voltage of the power amplifier such that the reference current is maintained at a known proportionality relative to the modulated supply current; and a detection circuit generating an inferential sense signal as a function of an operating voltage of the power amplifier and the reference current such that the inferential sense signal varies in dependence on power amplifier (PA) impedance.
Claim 51
Dependent Claim
29 words
The current modulator of claim 47 wherein the reference circuit comprises a reference control element responsive to the inferential sense signal to vary a resistance within the reference current.
Claim 52
Dependent Claim
25 words
The current modulator of claim 48 wherein the reference control element comprises a reference control transistor in the reference circuit configured as a variable resistor.
Claim 53
Dependent Claim
59 words
The current modulator of claim 47 wherein the output circuit includes an output transistor controlling the modulated supply current responsive to the amplitude modulation signal, and wherein the reference circuit includes a reference transistor controlling the reference current responsive to the amplitude modulation signal, and wherein the reference transistor has a known geometric scaling relative to the output transistor.
Claim 54
Dependent Claim
36 words
The current modulator of claim 50 wherein the reference control circuit further comprises a reference control element to maintain the operating conditions of the reference transistor the same as the operating conditions of the output transistor.
Claim 55
Dependent Claim
22 words
The current modulator of claim 51 wherein the operating voltage of the reference circuit comprises the drain voltage of the reference transistor.
Claim 56
Dependent Claim
30 words
The current modulator of claim 52 wherein the reference control element operates to maintain the drain voltage of the reference transistor equal to the drain voltage of the output transistor.
Claim 57
Dependent Claim
27 words
The current modulator of claim 53 wherein the drain voltages of the output transistor and the reference transistor both equal the operating voltage of the power amplifier.
Claim 58
Dependent Claim
21 words
The current modulator of claim 51 wherein the reference control element comprises a reference control transistor configured as a variable resistor.
Claim 59
Dependent Claim
19 words
The current modulator of claim 55 wherein the reference control transistor is connected in series with the reference transistor.
Claim 60
Dependent Claim
22 words
The current modulator of claim 47 wherein the operating voltage of the reference circuit equals the operating voltage of the power amplifier.
Claim 61
Dependent Claim
56 words
The current modulator of claim 47 wherein the detection circuit comprises a differential amplifier circuit connected between the output circuit and the reference circuit generating the inferential sense signal based on a difference between the operating voltage of the reference circuit and a corresponding operating voltage in the output circuit dependent on the power amplifier voltage.
Claim 62
Dependent Claim
33 words
The current modulator of claim 58 wherein the operating voltage of the reference circuit and the operating voltage of the output circuit are both equal to the operating voltage of the power amplifier.
Claim 63
Dependent Claim
56 words
The current modulator of claim 47 further comprising a modulation control circuit generating a modulation control signal responsive to the amplitude modulation signal, and wherein the modulation control circuit is coupled to the output circuit such that the output circuit controls the modulated supply current responsive to the modulation control circuit from the modulation control circuit.
Claim 64
Dependent Claim
30 words
The current modulator of claim 60 wherein the modulation control circuit is coupled to the reference circuit such that the reference signal is controlled responsive to the modulation control signal.
Claim 65
Dependent Claim
34 words
The current modulator of claim 61 wherein the modulation control circuit comprises a differential amplifier circuit comparing the amplitude modulation signal to a feedback signal derived from the operating voltage of the reference circuit.
Claim 66
Dependent Claim
40 words
The current modulator of claim 62 wherein feedback signal varies responsive to the inferential sense signal such that the control gain of the modulation control circuit remains fixed irrespective of changes in PA AM modulation impedance of the power amplifier.
Claim 67
Dependent Claim
27 words
The current modulator of claim 51 wherein the detection circuit generates a compensation control signal responsive to changes in PA AM modulation impedance of the power amplifier.
Claim 68
Dependent Claim
44 words
The current modulator of claim 64 further comprising a compensation controller circuit responsive to the compensation control signal to vary a modulation gain of the current modulator responsive to the compensation control signal to compensate for changes in power amplifier PA AM modulation impedance.
Claim 69
Dependent Claim
22 words
The current modulator of claim 65 wherein the gain controller varies a resistance of the current modulator to adjust the modulation gain.
Claim 70
Dependent Claim
23 words
The current modulator of claim 65 wherein the gain controller varies a scaling of the amplitude modulation signal to adjust the modulation gain.
Claim 71
Dependent Claim
40 words
The current modulator of claim 64 further comprising a compensation controller circuit responsive to the compensation control signal to adjust an impedance of a matching network coupled to an output of the power amplifier responsive to the compensation control signal.
References Cited (Backward Citations)
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