Telecommunications – Transmitter – Having harmonic radiation suppression
Patent
1990-05-18
1991-07-16
Eisenzopf, Reinhard J.
Telecommunications
Transmitter
Having harmonic radiation suppression
455126, 455302, 455317, H04B 104, H04B 110
Patent
active
050331108
ABSTRACT:
A frequency converter for a transmitter of a microwave radio communications system comprises an image reject mixer for mixing an IF signal with an LO or carrier frequency signal to produce an RF signal, and a nulling circuit for providing d.c. offsets to the image reject mixer to reduce carrier leak to the RF signal. The nulling circuit includes a source of phase quadrature chopper signals which are cross modulated with the LO signal to produce a modulated signal, and a single-ended mixer for mixing the modulated signal with part of the RF signal. The output of the single-ended mixer is low pass filtered and the resulting filtered signal is cross demodulated with the chopper signals to produce phase quadrature correction signals, which are integrated to produce the d.c. offsets for the image reject mixer. The arrangement avoids the need for, and expense of, a subsequent carrier frequency filter.
REFERENCES:
patent: 4243955 (1981-01-01), Daniel et al.
patent: 4591859 (1986-05-01), Campbell
patent: 4700151 (1987-10-01), Nagata
patent: 4811425 (1989-03-01), Feerst
Eisenzopf Reinhard J.
Haley R. John
Northern Telecom Limited
Pham Chi H.
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