Feed forward cancellation amplifier utilizing dynamic vector control

• US 5,508,657 A
• Filed: 01/30/1995
• Issued: 04/16/1996
• Est. Priority Date: 01/30/1995
• Status: Expired due to Fees

• Current Assignee: Microsemi RFIS, Inc. (Microchip Technology Incorporated)
• Original Assignee: Microsemi RFIS, Inc. (Microchip Technology Incorporated)
• Inventors: Behan, Scott T.
• Primary Examiner(s): MOTTOLA, STEVEN J
• Application Number:
  US08/380,042
• Time in Patent Office: 442 Days
• Field of Search: 330/52, 330/149, 330/151, 332/159, 332/162
• US Class Current: 330/151
• CPC Class Codes: H03F 1/3235 using a pilot signal
• CPC Class Codes: H03F 2201/3212 Using a control circuit to adjust amplitude and phase of a signal in a signal path

Abstract

A feed forward cancellation amplifier system for amplifying radio frequency telephony signals, including a main amplifier, an error correction circuit producing a message error signal, an error amplifier for producing an amplified message error signal that is then subtracted from the amplified and distorted message signal output of the main amplifier prior to a final output circuit, a negative feedback circuit responsive to a test signal for compensating and minimizing variation or drift in the operation of the error amplifier, the error correction circuit including a vector modulator responsive to modified quadrature vector components of the message error signal for producing a single voltage vector error signal, and the negative feedback circuit including an I & Q network for modifying the quadrature vector components of the error signal in the error correction circuit.

The preferred form of the invention utilizes PIN diodes to provide voltage controlled attenuators in the vector modulator.

An auxiliary negative feedback circuit is also provided for compensating variation or drift of the main amplifier.

Claims

1. An error correction circuit for modifying an error signal in response to a control signal, comprising:

a vector modulator including a first quadrature hybrid circuit having an input and a pair of outputs, a pair of voltage controllable attenuators coupled to respective outputs of said first quadrature hybrid circuit, and a power combiner having a pair of inputs coupled to respective ones of said attenuators, said power combiner also having an output;

means for applying the error signal to said input of said first quadrature hybrid circuit so as to produce the modified error signal at said output of said power combiner;

an I &

Q network including a power divider circuit having an input and two outputs, a pair of mixers coupled to respective outputs of said power divider, and a second quadrature hybrid circuit having two outputs also coupled to respective ones of said mixers, said second quadrature circuit also having an input;

circuit means coupling the outputs of said mixers to respective ones of said voltage controllable attenuators;

means for applying said control signal to said input of said power divider circuit; and

means for applying a test signal of predetermined frequency to said input of said second quadrature hybrid circuit for mixing with said control signal at said predetermined frequency to thereby control the modification of the error signal.

2. An error correction system including the error correction circuit of claim 1, and further comprising:

a circuit whose response is to be tested;

means for generating the test signal of predetermined frequency;

means for applying the test signal of predetermined frequency to said circuit whose response is to be tested; and

means for deriving from said circuit whose response is to be tested a residual portion of the test signal that is indicative of the circuit response, said residual signal portion then serving as the control signal.

3. An error correction system as in claim 2 wherein said circuit whose response is to be tested is a feed forward cancellation amplifier.

4. An error correction circuit as in claim 1 which includes a pair of low pass filter circuits coupling the outputs of said mixers to respective ones of said voltage controllable attenuators.

5. An error correction circuit as in claim 2 which includes a pair of low pass filter circuits coupling the outputs of said mixers to respective ones of said voltage controllable attenuators.

6. An error correction circuit as in claim 3 which includes a pair of low pass filter circuits coupling the outputs of said mixers to respective ones of said voltage controllable attenuators.

11. A feed forward cancellation amplifier system as in claim 3 wherein said vector modulator includes PIN diode circuits forming attenuators for modifying said quadrature vector components of said message error signal.

7. A feed forward cancellation amplifier having a main amplifier, and an error amplifier whose response is to be tested, comprising:

means for applying a test signal of predetermined frequency to the input of the main amplifier, and deriving a residual test signal from the output of the main amplifier;

a vector modulator having an input and an output, and including a pair of voltage controllable attenuators;

means for applying an error signal to said input of said vector modulator so as to produce a modified error signal at said output thereof;

an I &

Q network having two inputs, and also including a pair of mixers having outputs coupled to respective ones of said voltage controllable attenuators in said vector modulator, for modifying the error signal;

means for applying said residual test signal to one input of said I &

Q network; and

means for applying the test signal to the other input of said I &

Q network, for mixing with said residual test signal at said predetermined frequency to thereby control the modification of the error signal.

8. An error correction circuit as in claim 7 which includes a pair of low pass filter circuits coupling the outputs of said mixers to respective ones of said voltage controllable attenuators.

9. In a feed forward cancellation amplifier system for amplifying radio frequency telephony signals which includes a main amplifier, an error correction circuit producing a message error signal, an error amplifier for producing an amplified message error signal that is then subtracted from the amplified and distorted message signal output of the main amplifier prior to a final output circuit, and a negative feedback circuit responsive to a test signal for compensating and minimizing variation or drift in the operation of the error amplifier, the improvement comprising:

said error correction circuit including a vector modulator responsive to modified quadrature vector components of said message error signal for producing a single voltage vector error signal;

said negative feedback circuit including an I &

Q network for modifying said quadrature vector components of said error signal in said error correction circuit; and

wherein said vector modulator includes PIN diode circuits forming attenuators for modifying said quadrature vector components of said message error signal.

10. In a feed forward cancellation amplifier system for amplifying radio frequency telephony signals which includes a main amplifier, an error correction circuit producing a message error signal, an error amplifier for producing an amplified message error signal that is then subtracted from the amplified and distorted message signal output of the main amplifier prior to a final output circuit, test signal generating means for supplying a test signal to said main amplifier so as to produce a residual test signal at the final output circuit, and a negative feedback circuit responsive to the residual test signal for compensating and minimizing variation or drift in the operation of the error amplifier, the improvement comprising:

circuit means for breaking the message error signal into quadrature vector components;

said negative feedback circuit including an I &

Q network coupled to both the test signal generating means and the final output circuit and responsive to the residual test signal for producing quadrature control signals; and

circuit means including a vector modulator responsive to said quadrature control signals for dynamically and independently controlling the amplitudes of said quadrature components of said error signal and combining them into a single voltage vector error signal which is then supplied to said error amplifier.