摘要:
An apparatus comprising a low noise mixer comprising a transconductance amplifier configured to receive a differential voltage and to generate a differential current signal, a passive mixer directly connected to an output of the transconductance amplifier, and a transimpedance amplifier coupled to the passive mixer, wherein the transimpedance amplifier is configured to receive a current signal and convert the current signal to a voltage signal.
摘要:
Methods and corresponding systems for amplifying an input signal include inputting first and second differential input signals into first and second circuit legs, respectively, wherein the first circuit leg includes a first transistor coupled in series with a first variable current source, and wherein the second circuit leg includes a second transistor coupled in series with a second variable current source. The first and second variable current sources are dynamically set to provide first and second bias currents in response to the first and second differential input signals, wherein the first bias current is set inversely proportional to the second bias current. The first and second bias currents are sunk in the first and second circuit legs, respectively. First and second differential output signals are output from the first and second circuit legs, respectively.
摘要:
A variable attenuator and method of attenuating a signal is presented. The variable attenuator contains an input that receives an input signal to be attenuated. A voltage divider between a resistor and parallel MOSFETs provides the attenuated input signal. The MOSFETs have different sizes and have gates that are connected to a control signal through different resistances such that the larger the MOSFET, the larger the resistance. The control signal is dependent on the output of the attenuator. The arrangement extends the linearity of the attenuation over a wide voltage range of the control signal and decreases the intermodulation distortion of the attenuator.
摘要:
Methods and corresponding systems in a low noise amplifier include selecting a selected sub-band for amplifying, wherein the selected sub-band is one of a plurality of sub-bands, wherein each sub-band is a portion of a frequency band, and wherein each sub-band has a corresponding sub-band center frequency. Next, a gate-source capacitor is adjusted so that a real part of an LNA input impedance corresponds to a real part of a source impedance at the selected sub-band center frequency. A match capacitor is also adjusted so that the LNA input impedance corresponds to the complex conjugate of the source impedance at the selected sub-band center frequency. The gate-source capacitor and the match capacitor can each be adjusted by recalling capacitor values from memory that correspond to the selected sub-band, and connecting selected capacitor components in response to the recalled capacitor values.
摘要:
A frequency source having a fast start-up time and low noise in steady state is presented. The frequency source includes an oscillator and a hybrid automatic gain control (AGC) loop that switches between an analog AGC loop at oscillator start up and a digital AGC loop at steady state operation. The analog AGC loop includes a peak detector connected to the oscillator and an error integrator integrating the difference between the peak detector output and a reference voltage. The digital AGC loop includes a comparator comparing the peak detector output and high/low reference voltages, an oscillator counter providing a timer signal, a digital-to-analog converter (DAC) supplied with a digital word, and a low pass filter between the DAC and the oscillator. The timer signal causes a multiplexer to select either the analog AGC loop or the digital AGC loop.
摘要:
A high gain wide-band width RF amplifier 120 with automatic bias supply regulation. The load supply is actively adjusted in response to the amplifier's output signal level. At small output signals effective load supply voltage is minimum and at larger output signals the effective load supply voltages is maximized. The amplifier 120 includes a differential pair of field effect transistors (FETs) 102, 104 connected at common source connection 106 and biased by current bias FET 108 which is connected between common source connection 106 and amplifier signal input RFIN. A bias voltage (VB1) is applied to the gate of bias device 108 and an automatic gain control voltage (VAGC) is applied to the gates of differential FET pair 102, 104. The automatic bias supply circuit 122 is an active load and includes resistors 124, 126, capacitor 128 and a differential amplifier 130. Capacitor 128 is connected between the negative input 132 and the output 134 of differential amplifier 130. A load reference voltage VO is provided to the positive input. Resistor 124 is connected between the output 134 of differential amplifier 130 and the high gain wide-band amplifier output 136 at the drain of FET 104. Resistor 126 is connected between the output 136 at the drain of FET 104 and the negative input 132 to differential amplifier 130 providing amplifier load signal feedback.
摘要:
A temperature compensated crystal oscillator with an improved phase noise characteristic and a fast start up time includes a large time constant low-pass filter coupled to a temperature compensation circuit. At start up the low pass filter is effectively bypassed to enable the temperature compensation voltage and oscillator output frequency to settle quickly. A capacitance in the low-pass filter is precharged by a precharge circuit to match the temperature compensation voltage without disturbing the temperature compensation circuit and the concurrent settling of the oscillator. When the capacitance is fully charged, the low-pass filter is enabled without unsettling the oscillator output frequency.
摘要:
A method and apparatus for integrating a plurality of analog input signals. A first integrator(725) having a first pole frequency integrates a first of the input signals and a second integrator(730) having a second pole frequency different than the first pole frequency integrates a second of the input signals. A summer(735) is connected to the first and second integrators to then sum the integrated first and second signals and provide a composite integrated signal prior to transmitting a communications signal.
摘要:
A fully integrated, adjustable oscillator circuit for use with a crystal is disclosed in which a crystal oscillator, such as a Pierce oscillator, is arranged to utilize a tuning network that includes at least one integrated varactor (voltage-variable-capacitor) as a shunt element for providing at least one type of adjustment of the oscillating signal. More than one type of adjustment can be provided by including a bank of varactors for each of the shunt elements of the tuning network, in which various individual varactors are selected in binary (on-off) fashion to effect digital as well as analog adjustment of the crystal oscillator.
摘要:
An amplifier and method of amplifying a signal is presented. The amplifier contains a fixed gain stage, a digitally controllable gain stage, and a continuously variable attenuator connected between the fixed and controllable gain stages. The attenuator and controllable gain stage are controllable such that the gain of the controllable gain stage is decreased when the attenuation of the attenuator reaches a predetermined maximum value and the attenuation of the attenuator is reduced thereafter. The output power level of the amplifier remains constant.