FIG. 3 is a flow chart of the operation of the direction signal, on output 201, indicating when an adjustment signal
sensor in FIG. 2; from the adjustment signal source 202 needs to be changed.
FIG. 4 is a detailed schematic of an automatic gain and The change source signal is applied to the adjustment signal
phase control circuit; source 202.
FIG. S is a timing diagram of the direction sensor and 5 The adjustment signal source 202 is adapted to be capable
control circuitry operation for finding a peak; and of supplying currents of either negative or positive polarity.
FIG. 6 is a timing diagram of the direction sensor and ^ a change source signal is received by the adjustment
control circuitry operation for finding a null. signal source 202 from the direction sensitive device 200,
the adjustment signal source 202 is toggled to change the
DETAILED OF THE DRAWINGS 10 P0^^ of me source signal from negative to positive or
positive to negative, as the case may be. The adjustment
In many of the embodiments of the present invention data signal having the appropriate polarity is supplied from the
outputs and inputs are referred to. "Data" is used in a broad adjustment signal source 202 on lead 203 to the switch 210.
sense and can include both analog and digital information. As shown in FIG. 2D, the switch 210 preferably comprises
FIG. 1 shows a circuit 10 for reducing distortion, employ- 15 conductors 212 and 214, and dual switch 216.
ing an automatic control circuit 16, which includes the The control device 220 thereafter directs the adjustment
direction sensor of an embodiment of the present invention signal to one of the two data outputs of the switch 210, by
as will be later described. Circuit 10 provides a feedback sending an appropriate control signal to control input 221 to
signal to adjust a correction signal for reducing distortion. the switch 210. During a first output cycle the adjustment
The circuit 10 includes a signal combiner 12, an attenuation 20 signal is transferred to the first data output 24 of the switch
and phase circuit 14, an automatic control circuit 16, and a 210, while during a second output cycle the adjustment
coupler 18. The overall design of such a circuit 10 is known signal is transferred to the second data output 22 of the
in the art and can be derived from the circuit shown in FIG. switch 210. Intermediate buffer circuitry, which will be
2 of Myer, U.S. Pat. No. 4,580,105, the contents of which are described with reference to FIG. 4, can be provided to the
incorporated by reference herein. However, the operation 25 outputs 24 and 22 before they are applied to the attenuation
and design of the automatic control circuit 16 differs from and phase circuit 14 of FIG. 1. The adjustment signals from
that shown in Myer, U.S. Pat. No. 4,580,105, as will be the outputs 24 and 22 are each used to control gain and phase
further described with reference to FIGS. 2A-2D and 3. of a correction signal as described previously.
The overall operation of the circuit 10 in FIG. 1 will now 3Q The direction sensor 100, shown in detail in FIG. 2B, is
be described. The signal combiner 12 receives a distorted typically comprised of a switch 110, a control device 120,
carrier signal at its first input 11 and an adjusted correction two storage devices 130 and 132, a comparison device 140,
signal from the attenuation and phase circuit 14, at its second and a normalization device 150. As shown in FIG. 2C, the
input 13. The signal combiner 12 combines the distorted switch 110 is preferably comprised of conductors 112 and
carrier signal and the adjusted correction signal to form a J5 114 and a dual switch 116. The operation of the direction
"clean" carrier signal, at its output 15, which is substantially sensor 100 will be described with reference to the flow chart
free of distortion. A majority of the clean carrier signal is 300 of FIG. 3.
sent to other circuitry via coupler 18. However a small The nth test cycle begins at step 302. The integer n is used
portion of the clean carrier signal is used as a feedback to indicate that the operation of direction sensor 100 may be
signal and sent to the automatic control circuit 16 via input ^ started at any time. If n is even, a first control signal is
20- applied by control device 120, on control output 121, to the
The automatic control circuit 16 uses the feedback signal switch 110 to transfer the nth sample of the test signal from
at input 20 to create two control signals at outputs 22 and 24, the input 20 to the first data output 111 of the switch 110 at
respectively. The control signals are applied to the attenu- steps 304 and 306. Again, if n is even, the nth sample is
ation and phase circuit 14 and are used as adjustment signals 45 stored in the first storage device 130 in FIG. 2, at step 308.
to adjust the gain and phase of a correction signal appearing If n is odd, a second control signal is applied by control
at the data input 17 of the attenuation and phase circuit 14. device 120 to the switch 110, on control input 121 to transfer
The adjusted correction signal, from input 13, is again the nth sample of the test signal from the input 20 to the
combined with the distorted carrier signal, from input 11, in second data output 113 of the switch 110 and then to the
the signal combiner 12. This feedback technique preferably 50 second storage device 132 at steps 310 and 312.
continuously adjusts the correction signal to provide maxi- At step 314 it is determined if the number of samples is
mum reduction of distortion. greater man 1. If only one sample has been taken, n is
FIG. 2A shows a block diagram of the automatic control effectively incremented at step 316 by going to the next
circuit 16, for use in the circuit of FIG. 1, in accordance with sample and the next test cycle at step 302. If at least two
an exemplary embodiment of the present invention. The 55 samples have been taken, the samples in the first and second
automatic control circuit 16 typically includes a direction storage devices 130 and 132, respectively, are compared by
sensor 100, a direction sensitive device 200, an adjustment comparison device 140, which produces a comparison signal
signal source 202, a switch 210, and a control device 220. on output 141 at step 318. A normalization signal is pro
In operation, the automatic control circuit 16 shown in duced by control device 120, on its second control output
FIG. 2A receives a feedback signal, which will be called a 60 123 at step 320. The normalization device 150 combines the
"test signal" at the input 20. The test signal is processed by comparison signal and the normalization signal to produce a
the direction sensor 100, the details of which will be direction signal on output 160 at step 322. At step 324 n is
described subsequently with reference to FIGS. 2B and 2C. effectively incremented by starting another test cycle and the
The direction sensor 100 produces a direction signal at the testing loop begins again at step 302.
output 160 which is indicative of the direction of change of 65 The quantity "n" has been used for explanation purposes,
the test signal. The direction signal is applied to direction however an actual quantity "n" does not have to exist or be
sensitive device 200, which produces a change source examined. Rather control device 120 may simply alternate