A dual-PFD circuit with delay feedback generated by a dual-modulus prescaler based on mode control from a feedback delay generation circuit. The PFD circuit can be used with a PLL feedback divider to divide a VCO clock signal VCO_clk and generate FB and FB_DLY signals. The PLL feedback divider includes a dual modulus prescaler to selectively divide the VCO_clk by either M or M+1 (such as 4/5) based on a divide mode control input to generate a prescaled divide signal, and a programmed counter/divider (N counter/1/N divider) to selectively divide the prescaled divide signal to generate the FB signal, and a delay generation circuit to selectively delay the FB signal by a pre-defined delay to generate the FB_DLY signal. The prescaler is responsive to the pre-defined delay from the delay generation circuit to change divide modes. The dual PFD circuit response to the FB and FB_DLY signals in relation to a reference signal to generate a phase comparison signal. the dual-PFD circuit can be used with a charge-pump coupled to the dual PFD circuit, and responsive the phase comparison signal to generate a frequency tuning voltage, for input to a VCO for generating the VCO clock signal. The dual PFD circuit, charge pump and VCO can be used in a PLL frequency synthesizer.

A novel phase locked loop design utilizing novel phase-frequency detector, charge pump, loop filter and voltage controlled oscillator is disclosed. The phase-frequency detector includes a dual reset D-flip flop for use in multi-GHz phase locked loops. Traditional dead zone issues associated with phase frequency detector are improved/addressed by use with a charge transfer-based PLL charge pump.

The present invention relates to passive phased injection locked circuit and ring-based voltage controlled oscillators. A passive phased injection locked circuit comprises first and second transmission lines, each has a plurality of discrete elements, that are operative to delay the phase of AC signal. Between the first and second transmission lines, a capacitor network is formed to advance the phases of the AC signal in concert along the transmission lines. For the ring-based voltage controlled oscillators, each of the first and second transmission lines has an odd number of discrete elements.

A signal generator. A voltage controlled oscillator generates a signal that is fed to a comb generator, e.g., a nonlinear transmission line. A tone, from among a comb of tones at the output of the comb generator, is selected by a bandpass filter, its frequency is divided, e.g., by a direct digital synthesizer, and the result is compared, e.g., by a phase and frequency detector that receives a reference signal at its other input. The output of the phase and frequency detector is fed back, e.g., through a lowpass filter, to the voltage controlled oscillator.

A phase locked loop may be operable to generate, utilizing a frequency multiplier, a reference clock signal whose frequency is an integer M times a frequency of a crystal clock signal and is keyed on both rising and falling edges of the crystal clock signal. The phase locked loop may enable usage of both rising and falling edges of the crystal clock signal, based on the reference clock signal. The phase locked loop may perform an operation of the phase locked loop based on the enabling. The phase locked loop may perform a phase comparison function, based on both rising and falling edges of the crystal clock signal. By utilizing a sampled loop filter in the phase locked loop, the phase locked loop may eliminate, at an output of a charge pump in the phase locked loop, disturbance which is associated with duty cycle errors of the crystal clock signal.

In some embodiments, a phase locked loop includes a voltage-controlled oscillator whose output is fed back to a first input of a phase comparator via a fractional divider controlled by a delta-sigma modulator. The method of doubling the frequency of the initial reference signal of the phase locked loop involves generating, from the initial reference signal and the output signal furnished by the voltage-controlled oscillator, a secondary reference signal having edges of a first type synchronized with each of the rising and falling edges of the initial reference signal and edges of a second type between the edges of the first type, and a furnishing of the secondary reference signal at a second input of the phase comparator operating on the edges of the first type.

In some embodiments, a phase locked loop includes a voltage-controlled oscillator whose output is fed back to a first input of a phase comparator via a fractional divider controlled by a delta-sigma modulator. The method of doubling the frequency of the initial reference signal of the phase locked loop involves generating, from the initial reference signal and the output signal furnished by the voltage-controlled oscillator, a secondary reference signal having edges of a first type synchronized with each of the rising and falling edges of the initial reference signal and edges of a second type between the edges of the first type, and a furnishing of the secondary reference signal at a second input of the phase comparator operating on the edges of the first type.

Systems and methods are provided in which an offset phase-locked loop (PLL) system can be configured as part of a radio frequency transmitter. The PLL can include a phase detection circuit including a first input configured to receive an information signal and a second input configured to receive a feedback signal; a charge pump including an input coupled to the phase detection circuit and an output; a filter including an input coupled to the output of the charge pump; a voltage-controlled oscillator coupled to the charge pump and including an LC tank circuit comprising an inductive element and a capacitive element, wherein the inductive element of the LC tank circuit comprises the antenna; and a feedback path.

A phase locked loop may be operable to generate, utilizing a frequency multiplier, a reference clock signal whose frequency is an integer M times a frequency of a crystal clock signal and is keyed on both rising and falling edges of the crystal clock signal. The phase locked loop may enable usage of both rising and falling edges of the crystal clock signal, based on the reference clock signal. The phase locked loop may perform an operation of the phase locked loop based on the enabling. The phase locked loop may perform a phase comparison function, based on both rising and falling edges of the crystal clock signal. By utilizing a sampled loop filter in the phase locked loop, the phase locked loop may eliminate, at an output of a charge pump in the phase locked loop, disturbance which is associated with duty cycle errors of the crystal clock signal.

A dual-PFD circuit with delay feedback generated by a dual-modulus prescaler based on mode control from a feedback delay generation circuit. The PFD circuit can be used with a PLL feedback divider to divide a VCO clock signal VCO_clk and generate FB and FB_DLY signals. The PLL feedback divider includes a dual modulus prescaler to selectively divide the VCO_clk by either M or M+1 (such as 4/5) based on a divide mode control input to generate a prescaled divide signal, and a programmed counter/divider (N counter/1/N divider) to selectively divide the prescaled divide signal to generate the FB signal, and a delay generation circuit to selectively delay the FB signal by a pre-defined delay to generate the FB_DLY signal. The prescaler is responsive to the pre-defined delay from the delay generation circuit to change divide modes. The dual PFD circuit response to the FB and FB_DLY signals in relation to a reference signal to generate a phase comparison signal. the dual-PFD circuit can be used with a charge-pump coupled to the dual PFD circuit, and responsive the phase comparison signal to generate a frequency tuning voltage, for input to a VCO for generating the VCO clock signal. The dual PFD circuit, charge pump and VCO can be used in a PLL frequency synthesizer.