Abstract In a circuit for translating to a variable carrier frequency an input signal with a fixed carrier frequency, comprises said signal at said variable frequency, the linearity of the amplifier being obtained by means of a negative feedback loop between the output of the amplifier and of the signal input of the frequency converter and this feedback loop including a frequency converter for re-translating the feedback signal to the frequency of the input signal, the variable phase-shifter ensuring the addition in phase opposition, in an adder, of the input signal and of the feedback signal is inserted between this adder and the frequency converter feeding the amplifier. This location of the phase-shifter causes the gain of the circuit to be substantially independent of the variable frequency which is used. In addition the phase-shifter is automatically controlled.
A frequency converting and amplifying circuit comprising: a main input for receiving a signal; summing means having a first input coupled to said main input, a second input and an output; a variable phase-shifter having aN input coupled to said output of said summing means, and an output; a first mixer having a first input coupled to said output of said summing means, a second input and an output; an amplifier having an input coupled to said output of said mixer; a feedback loop including a second mixer having a first input coupled to said output of said amplifier, a second input and an output which is coupled to said second input of said summing means; variable-frequency generating means for feeding said second inputs of said first and second mixers; a phase comparator having two inputs respectively coupled to said output of said second mixer and to said main input, and an output; and further means for controlling said variable phaseshifter as a function of the output signal of said phasecomparator.
Claim 2
Dependent Claim
171 words
A frequency converting and amplifying circuit comprising: a main input for receiving a signal; summing means having a first input coupled to said main input, a second input and an output; a variable phase-shifter having aN input coupled to said output of said summing means, and an output; a first mixer having a first input coupled to said output of said summing means, a second input and an output; an amplifier having an input coupled to said output of said mixer; a feedback loop including a second mixer having a first input coupled to said output of said amplifier, a second input and an output which is coupled to said second input of said summing means; variable-frequency generating means for feeding said second inputs of said first and second mixers; a phase comparator having two inputs respectively coupled to said output of said second mixer and to said main input, and an output; and further means for controlling said variable phaseshifter as a function of the output signal of said phasecomparator.
Claim 3
Dependent Claim
74 words
A frequency converting and amplifying circuit as claimed in claim 1, wherein said further means comprise a clock, a gate having two inputs respectively coupled to said output of said phase-comparator and to said clock and an output; a counter having an input coupled to said output of said gate and an output; and a digital-to-analogue converter having an input coupled to said output of said counter and an output coupled to said phase-shifter.