Page 286 - Analog and Digital Filter Design

Phase-Shift Networks (All-Pass Filters) 283

1 OK P network

-
output 1

output 2

Figure 9.18
Active Quadrature Network (N = 4)

Both these designs have been simulated to prove that the component values are
correct, at least in principle. Imperfections in real components may lead to
increased phase-shift errors, resulting in less than ideal sideband rejection.

There is another method of producing single sideband modulation. It is known
as the “Third Method,” or the Weaver method (after D. K. Weaver who first
described it). This uses two pairs of mixers, each pair phase-shifting the base-
band signal by 90”. The Weaver circuit, and it’s relative the Barber circuit,
requires a longer explanation than the phasing method and is not really the
subject of this book.

References

I. Williams. A. B., and E J. Taylor. Electronic Filter Design Handbook,
New York: McGraw-Hill, 1988.
&. Thomlinson, G. H. Electrical iVetuTorks and Filters. London: Prentice
3
Hall, 1991.