US4890066A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Envelope detector
Assignee: US Philips Corp
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Filing: 1988-08-29
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Granted: 1989-12-26
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Expires: 2008-08-29
Abstract
Abstract Envelope detector comprising a differential amplifier (A), a full-wave rectifier circuit and a smoothing filter (AF), which differential amplifier (A) converts an input voltage into a pair of current signals in phase opposition and which full-wave rectifier circuit comprises a pair of half-wave rectifiers (HWR1, HWR2) for half-wave rectifying the said pair of current signals, coupled to a first combining stage (S) for combining the output signals of the two half-wave rectifiers (HWR1, HWR2) with like polarity, which first combining stage (S) supplies a full-wave rectified signal. In order to reduce d.c. offsets, the detector comprises a frequency-dependent negative feedback loop which comprises a second combining stage (D) coupled to the outputs (R o1 , R o2 ) of the pair of half-wave rectifiers (HWR1, HWR2) for combining the output signals of the pair of half-wave rectifiers (HWR1, HWR2) with opposite polarity, said second combining stage (D) being negatively fed back to the input (I c ) of the differential amplifier (A) via a low-pass filter (LPF) for a selection of the d.c. component.
Inventors
- 👤 Willibrordus G. M. M. Straver
- 👤 Ernst H. Nordholt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 17:11
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/14; H03D1/18; H03D1/02; H03D1/06; H03D1/08; H03D1/10
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
140 words
An envelope detector comprising a differential amplifier, a full-wave rectifier circuit and a smoothing filter, said differential amplifier converting an input voltage into a pair of current signals in phase opposition, said full-wave rectifier circuit comprising a pair of half-wave rectifiers for half-wave rectifying the said pair of current signals and furnishing respective half-wave rectifier output signals corresponding to the so-rectified current signals, and a first combining stage coupled to said full-wave rectifier circuit for combining said half-wave rectifier output signals with like polarity, characterized by a frequency-dependent negative feedback loop which has a second combining stage coupled to the outputs of the pair of half-wave rectifiers for combining said half-wave rectifier output signals with opposite polarity, said second combining stage being negatively fed back to the differential amplifier via a low-pass filter for a selection of the d.c. component.
Claim 2
Dependent Claim
140 words
An envelope detector comprising a differential amplifier, a full-wave rectifier circuit and a smoothing filter, said differential amplifier converting an input voltage into a pair of current signals in phase opposition, said full-wave rectifier circuit comprising a pair of half-wave rectifiers for half-wave rectifying the said pair of current signals and furnishing respective half-wave rectifier output signals corresponding to the so-rectified current signals, and a first combining stage coupled to said full-wave rectifier circuit for combining said half-wave rectifier output signals with like polarity, characterized by a frequency-dependent negative feedback loop which has a second combining stage coupled to the outputs of the pair of half-wave rectifiers for combining said half-wave rectifier output signals with opposite polarity, said second combining stage being negatively fed back to the differential amplifier via a low-pass filter for a selection of the d.c. component.
Claim 3
Dependent Claim
53 words
An envelope detector as claimed in claim 1, characterized in that the pair of half-wave rectifiers is constituted by a diode pair which is arranged in the direction of conductivity between a pair of current outputs of the differential amplifier and ground, and whose diodes are fed with mutually equal diode bias currents.
Claim 4
Dependent Claim
120 words
An envelope detector as claimed in claim 1, characterized in that the differential amplifier comprises a transistor pair whose bases are coupled to an input terminal pair of the differential amplifier, whose emitters are connected via first and second emitter resistors, respectively, to a common emitter current source and whose collectors are coupled via first and second collector current sources, respectively, to a power supply voltage and to the pair of half-wave rectifiers, said current sources being coupled via a current mirror arrangement to a common reference current, said current mirror arrangement comprising a current bias circuit for biasing the current of the emitter current source at the sum value of the currents of the said two collector current sources.
Claim 5
Dependent Claim
81 words
An envelope detector as claimed in claim 2, characterized by a transistor pair whose emitters are coupled to the diodes of the said diode pair, whose bases are coupled to a common base bias voltage and whose collectors are coupled via the smoothing filter to both the first and the second combining stage, said smoothing filter being provided with a capacitance arranged between the two collectors and a pair of collector resistors arranged in the collector leads of the transistor pair.
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) | 1992-12-25 | 1993-06-26 | 1993-12-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-25 | 1997-06-26 | 1997-12-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-25 | 2001-06-26 | 2001-12-26 | $7700.00 | Window Closed / Lapsed |