Abstract:
A phase detector circuit compares the phases of first and second periodic input signals to generate an output signal. The phase detector includes a circuit that makes two different combinations of the first and the second periodic input signals to generate third and fourth periodic signals. This circuit causes the third periodic signal to be based on a first combination of the first periodic signal and the second periodic signal that imparts a first relative phase shift. The circuit causes the fourth periodic signal to be based on a second combination of the first periodic signal and the second periodic signal to provide a different relative phase shift. The phase detector also includes a comparison circuit that compares a measure of the power of the third periodic signal to a measure of the power of the fourth periodic signal to generate the phase comparison output signal.
Abstract:
A phase detection circuit can include two phase detectors that each generate a non-zero output in response to input signals being aligned in phase. The input signals are based on two periodic signals. The phase detection circuit subtracts the output signal of one phase detector from the output signal of the other phase detector to generate a signal having a zero value when the periodic signals are in phase. Alternatively, a phase detector generates a phase comparison signal indicative of a phase difference between periodic signals. The phase comparison signal has a non-zero value in response to input signals to the phase detector being aligned in phase. The input signals are based on the periodic signals. An output circuit receives the phase comparison signal and generates an output having a zero value in response to the periodic signals being aligned in phase.
Abstract:
A phase- frequency detection system and method for enhancing performance of the frequency detector in a phase-frequency detection system. Filtering of the frequency detector inputs makes operation of the frequency detector more robust in the presence of intersymbol interference within the incoming data signal and other non-ideal characteristics such as noise and crosstalk.
Abstract:
A method and apparatus for determining a relationship between an input signal frequency (14) and a reference signal frequency is envisioned. The system derives a plurality of internal reference signals from the reference signal. The internal reference signals are provided to a level detection circuit (20a) which in turn samples the input signal a number of times within a period of time. Values associated with these samples are stored, as is one value of a sample from a previous period. The stored samples are correlated, and a relationship between the input signal frequency and the reference signal frequency is derived.
Abstract:
Known phase detectors have feedbackloops and do not function properly under severe conditions. By providing said phase detectors with difference establishers (1) for establishing differences between input signals and with selectors (2) for selecting one of said differences to be used as an output signal for phase locking purposes, the phase detectors operate better under more severe conditions, with any dead-zone having disappeared. Said selector (2) is a feedbackless selector, then a loop delay no longer exists, the linear range will not get any smaller for higher frequencies, the output jitter will not increase, for sampled input signals. Said selector (2) comprises latches (21,22) and a multiplexer (23). A converter (3) converts input signals into compensated input signals, via a buffer circuit (31,33) coupled to a replica circuit (32,34) per input signal, to provide input signals having substantially equal amplitudes and being compensated with process errors and temperature variations. The difference establisher (1) is based upon moduli or squares.
Abstract:
The invention relates to measuring in an accurate way, e.g. in a communication system, the phase difference of two periodic input signals (INA, INB) having essentially the same frequency (fi), with a high resolution and utilizing digital components. A high resolution digital phase detector (PD), which can be included in a phase locked loop (PLL), comprises an oscillator (O) providing a clock signal having a high frequency (fO) not being an integer multiple of the frequency of the imput signals (INA, INB). The clock signal is provided to a clock signal input of a counter (C) and the periodic signals (INA, INB) are fed to the start and stop terminals of the counter (C). Output terminals (I1) of the counter (C) are directly connected to inputs of a digital low-pass filter (DLP) in which an average value calculation is carried out of the integer values on the output of the counter. Because of the small frequency deviation ( DELTA f) from the integer multiple value a slow sliding of the oscillator phase compared to the phase of the input signals (INA, INB) is achieved, such that all possible integer values on the output of the counter (C) are run through. By the average value calculation of these integer values in the low-pass filter (DLP), a very accurate calculation of the phase position is achieved. In a complete phase-locked loop (PLL) a voltage controlled oscillator (VCO) provides one of the input signals to the counter (C) through a divider circuit (ND).
Abstract:
A voltage comparator (10) includes two sampled input networks connected in parallel between an input reference voltage (Vref) and the inverting input (16) of an integrator (12, 14), the other input (18) of which is grounded. The first input network has a first input capacitor (C1) which is through-switched at a first sampling frequency (F1). The second input network has a second input capacitor which is diagonally-switched at a second sampling frequency (F2), thus providing an output voltage to the integrator (12, 14) which is of opposite polarity to that of the first network. For a given ratio between the capacitors (C1, C2) the output (15) of the integrator is determined by the relationship between the sampling frequencies (F1, F2), thus providing a comparator capability.