Precision high frequency phase adders
An electronic circuit including: a differential multiplier circuit with a first differential input and a second differential input and a differential output; and a phase locked loop (PLL) circuit including: (1) a balanced differential mixer circuit with a first differential input electrically connected to the differential output of the differential multiplier circuit, a second differential input, and an output; (2) a loop filter having an output and an input electrically connected to the output of the balanced differential mixer circuit; and (3) a voltage controlled oscillator (VCO) circuit having an input electrically connected to the output of the loop filter and with an output electrically feeding back to the second differential input of the balanced differential mixer circuit.
1. A method of initializing a phase adder circuit that comprises a multiplier circuit with a first input and a second input and an output; and a phase locked loop (PLL) circuit formed by: (1) a mixer circuit electrically connected to the output of the multiplier circuit; (2) an amplifier with an input electrically connected to the output of the mixer circuit; (3) a loop filter having an output and having an input electrically connected to an output of the amplifier; and (4) a voltage controlled oscillator (VCO) circuit electrically connected to the output of the loop filter and with an output electrically feeding back to the second input of the mixer circuit, said method comprising:
switchably connecting the first input of the multiplier circuit to ground;
switchably disconnecting the input of the loop filter from being electrically connected to the output of the amplifier and connecting the input of the loop filter to receive a signal derived from the output of the VCO;
while the first input of the multiplier circuit is connected to ground and the input of the loop filter receives the signal derived from the output of the VCO, adjusting a bias signal applied to the amplifier
until the output of the amplifier has a DC operating point approximately equal to the output of the loop filter; and
when the output of the amplifier has a DC operating point that is approximately equal to the output of the loop filter, switching the input of the loop filter from receiving the signal derived from the output of the VCO to electrically connect to the output of the amplifier.
2. The method of claim 1 , further comprising:
after switching the input of the loop filter from receiving the signal derived from output of the VCO to electrically connect to, the output of the amplifier, switchably connecting the first input of the multiplier to receive a first distributed signal and receiving a second distributed signal at the second input of the multiplier.
3. The method of claim 1 , wherein adjusting the bias signal applied to the amplifier until the output of the amplifier has a DC operating point approximately equal to the output of the loop filter comprises:
comparing the output of the amplifier to the output of the loop filter;
while comparing output of the amplifier to output of the loop filter, incrementally introducing incremental amounts of current into the input of the amplifier until the output of the amplifier has a DC operating point approximately equal to the output of the loop filter.
4. The method of claim 1 , wherein the multiplier circuit is a differential multiplier circuit.
5. The method of claim 1 , wherein the mixer circuit is a balanced differential mixer circuit.
6. The method of claim 1 , wherein the amplifier is a folded cascode amplifier.