Quadrature demodulator having active filters formed with emitter

Details Quadrature demodulator having active filters formed with emitter Quadrature demodulator having active filters formed with emitter

1996-11-15

1998-03-31

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

Including discrete semiconductor device

329306, 329318, 329323, 375324, 455214, 455312, 455337, H03D 122, H03D 716

Patent

active

057342954

ABSTRACT:
The invention provides a quadrature demodulator which removes unnecessary higher harmonic signals included in a demodulation output without giving rise to increase in number of externally connected parts and increase in current consumption. The quadrature demodulator includes a first double differential circuit to which a modulated signal and a first local signal are inputted, a first emitter follower circuit for effecting impedance conversion, a second double differential circuit to which the modulated signal and a second local signal having a phase shifted by 90-degrees from the first local signal are inputted, and a second emitter follower circuit connected to a pair of outputs of the second double differential circuit for effecting impedance conversion. The quadrature demodulator further includes a CR circuit including a resistor and a capacitor connected to each of the outputs of the first and second double differential circuits such that an active filter is formed from the CR circuit and a corresponding one of the first and second emitter follower circuits.

REFERENCES:
patent: 5140198 (1992-08-01), Atherly et al.
Malikov, et al. "A Linear Synchronous Detector," 1298 Telecommunication and radio engineering, vol. 35/36, No. 1, Jan. 1981, pp. 63-66.
Chapovskiy, et "Q-Factor Instability of the Complex Conjugate Poles of an Emmitter-Follower Active RC-Network," 1298 Telecommunications and radio engineering, Vo. 24, No. 10, Oct. 1969, pp. 139-140.

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