摘要:
A digital-to-analog converter adapted for use as a feedback converter in a continuous time sigma delta analog-to-digital converter. The digital-to-analog converter has a discrete time digital signal input accepting digital signal samples that are synchronized with an assertion of a first data clock signal and a discrete time clock generator that generates an output pulse in response to receiving an assertion of the first data clock. The output pulse is asserted for a fixed duration that is independent of a jitter of the first data clock. The digital-to-analog converter also includes a continuous time analog output that produces, during assertion of the output pulse, a continuous time analog output signal having a magnitude corresponding to the digital signal samples.
摘要:
A double balanced mixer circuit (50) having a multiplication circuit (10) and an active filter circuit (30) coupled to the multiplication circuit (10). The active filter circuit (30) has a common-base differential amplifier (32) coupled to the differential outputs (52,54) of the multiplication circuit (10) and generates differential current outputs in response to the differential output current signal of the multiplication circuit (10), and a differential second order low pass active filter (34) coupled to the common-base differential amplifier (32) for filtering the differential current outputs of the common-base differential amplifier (32) and generating a filtered differential mixer output signal. A single direct current source coupled to the multiplication circuit (10) is also used to bias the active filter circuit (30). The mixer circuit (50) has utility in a non-differential mode as well as a fully differential mode.
摘要:
A filter (13) for providing temperature compensation for the quality factor thereof comprises transconductance amplifiers (23 and 24) in a gyrator configuration coupled between an input node (21) and an output node (22). A parallel capacitor (25) is coupled between the input node (21) and a supply voltage, and a parallel resistor (26) is coupled between the input node (21) and the supply voltage. A series capacitor (27) is coupled to the output node (22), and a series resistor (28) is coupled between the second capacitor (27) and the supply voltage.
摘要:
A paging receiver is provided which digitizes and stores received analog voice messages. The stored voice message may be retrieved by using a first switch for a normal playback mode, or by using a second switch for a fast forward and fast reverse playback mode. The fast forward and fast reverse playback modes are achieved by sequentially retrieving every N(th) message bit stored in memory.
摘要:
A receiver (200) includes an automatic frequency controller that determines the frequency of a receiver signal, and a calculates a frequency error from the received signal. The frequency error is used to calculate a correction factor (316) that is used to adjust the frequency of an oscillator (308) in response to the determined error.
摘要:
A digital-to-analog converter adapted for use as a feedback converter in a continuous time sigma delta analog-to-digital converter. The digital-to-analog converter has a discrete time digital signal input accepting digital signal samples that are synchronized with an assertion of a first data clock signal and a discrete time clock generator that generates an output pulse in response to receiving an assertion of the first data clock. The output pulse is asserted for a fixed duration that is independent of a jitter of the first data clock. The digital-to-analog converter also includes a continuous time analog output that produces, during assertion of the output pulse, a continuous time analog output signal having a magnitude corresponding to the digital signal samples.
摘要:
A sigma delta analog-to-digital converter (100) comprising a second or third order integrator block (105) featuring a feed-forward connection path between the input of the integrator block and an input of at least one of the plurality of integrators (130 or 150). A comparator (180) coupled to the output of the integrator block (105) generates as output a digital value representing a difference between the integrator output signal with respect to a threshold, or in a differential mode implementation, between component signals of a differential signal output by the integrator block (105). A digital sampling element (190) coupled to the output of the comparator (180) samples the output of the comparator (180) in response to a sampling clock signal at a predetermined sampling frequency to generate as output digital signal comprising samples of the digital values output by the comparator (180).
摘要:
An oscillator circuit (143) comprises a master phase-locked loop (PLL) circuit (202) that receives as input a first reference frequency signal (136) and generates a first clock signal (210) in response to an oscillator control signal (212). The oscillator circuit (143) includes a frequency sensitive slave circuit (206) having at least one frequency sensitive element (322) that is responsive to a tracking control signal (214) to generate a second clock signal (216). A tracking control circuit (204) is responsive to the oscillator control signal (212) for generating the tracking control signal (214). The tracking control signal (214) serves as a bias signal, and is connected to the frequency sensitive slave circuit (206) for achieving a fast power up sequence of the oscillator circuit (143).
摘要:
A data recovery device (208) for recovering data symbols having a period T from a received data stream. The data recovery device samples at least one data symbol in the received data stream at a rate determined by an integration envelope (301) having the period T. The samples are accumulated as a weighted sample count representing a recovered data symbol that is then stored as at least one recovered data bit.
摘要:
A selective call receiver (100) includes a receiver (1104) for receiving a signal. The receiver (104) includes a controlled filter (142) having a variable frequency response. A decoder (106) coupled to the controlled filter (142) of the receiver (104) decodes the received signal. The decoder (106) has a decoder clock for generating a decoder clock signal (122). A controlled oscillator (134) has an input filter (136) controlled by a control signal (132). The controlled oscillator (134) generates an output signal (140) in response to the control signal (132) for coupling to a comparator (124) which generates the control signal (126) from the decoder clock signal (122) and the output signal (140). The control signal (126) is further coupled to the controlled filter(142) for controlling the frequency response of the controlled filter (142) which filters the received signal.