Abstract: Variable gain low noise amplifier (LNA) system to reduce linearity requirements on a radio receiver. In the receiver, the LNA is coupled to receive an RF signal and produce an amplified signal at an LNA output. The receiver also comprises a VGA coupled to the LNA output to receive the amplified signal and produce a VGA output to downstream components of the receiver. The receiver also comprises a control network coupled to the LNA and the VGA. The control network operates to adjust gain factors of the continuously variable LNA and the VGA based on a received power indicator of the RF signal, so that a signal-to-noise ratio required for demodulation of the RF signal is met with a selected margin and the linearity requirements of the receiver are reduced.

Abstract: Adaptive receiver system that adjusts to the level of interfering signals. An adaptive system is provided for use with a radio receiver to adapt to interfering signals associated with a received RF signal. The radio receiver includes a LNA to receive the RF signal and produce an amplified signal that is coupled to a down-converting mixer that produces a mixer output. A peak detector is coupled to receive the mixer output to produce a peak signal. An integrator is coupled to the peak detector to receive the peak signal and produce an integrated signal and a mixer is coupled to receive the integrated signal and a transmit power indicator to produce a current control signal that is coupled to the LNA. The current control signal is used to control a bias current of the LNA, so that cross modulation associated with the received RF signal is reduced.

Abstract: A differential feedback system that minimizes even order distortion of a differential circuit. The feedback system includes a feedback circuit for use with a differential circuit to reduce even-order distortion and dc offset of a difference output signal produced by the differential circuit. The feedback circuit includes an integrator coupled to receive the difference output signal from the differential circuit and produce an integrator output signal. The feedback circuit also includes a control circuit coupled to the integrator to receive the integrator output signal to produce a control signal that is coupled to the differential circuit, wherein the control signal controls the differential circuit to reduce the even-order distortion and the DC offset.

Abstract: Voltage-controlled oscillator with apparatus for automatic calibration. The voltage-controlled oscillator includes switches connecting associated coarse-tuning capacitors to an LC resonant tank of the oscillator. The voltage-controlled oscillator also comprises a calibration loop used to appropriately set the switches associated with the coarse tuning apparatus based on a oscillator control signal.

Abstract: Continuous variable-gain low-noise amplifier. The amplifier continuously adjusts its gain between well-defined high and low values by using a cascode current-steering circuit to partition signal current between two different nodes of an output loading network. A shunt feedback network connected from an intermediate node of the loading network to the input provides negative feedback that linearizes the amplifier as its gain is decreased. The circuit degrades the noise figure at lower gains considerably less than conventional circuits by varying the gain without directly dumping the signal current to the power supply. The circuit produces only small changes in input and output impedances and preserves an improved reverse-isolation cascode characteristic as the gain is controlled.

Abstract: A translinear variable-gain amplifier. The translinear variable gain amplifier receives a differential input voltage and produces a differential output current having a selected gain. The amplifier comprises a buffer amplifier that receives the differential input voltage and produces a differential input current. The amplifier further comprises a translinear gain cell coupled to receive the differential input current and produce the differential output current. The gain cell includes a first adjustable bias source that operates to set a linear input range of the gain cell, and a second adjustable bias source that operates to set a gain value of the gain cell.

Abstract: A differential feedback system that minimizes even order distortion of a differential circuit. The feedback system includes a feedback circuit for use with a differential circuit to reduce even-order distortion and dc offset of a difference output signal produced by the differential circuit. The feedback circuit includes an integrator coupled to receive the difference output signal from the differential circuit and produce an integrator output signal. The feedback circuit also includes a control circuit coupled to the integrator to receive the integrator output signal to produce a control signal that is coupled to the differential circuit, wherein the control signal controls the differential circuit to reduce the even-order distortion and the DC offset.

Abstract: System for highly linear phase modulation. Apparatus is provided for linear phase modulation utilizing a phase-locked loop (PLL). The apparatus includes a PLL utilizing fractional N synthesis to realize a non-integer divide value. A two-port voltage-controlled oscillator includes a first port controlled by the phase-locked loop and a second port accessed for direct modulation. A second input to the fractional-N phase-locked loop is provided to remove the modulation introduced at the second port. Lastly, a calibration loop is provided wherein a frequency offset applied at the second port is adjusted until it cancels the effects of a known frequency offset introduced to the fractional-N phase-locked loop.

Abstract: A variable-gain BiCMOS transconductance amplifier (VGA). An NMOS differential pair amplifier with bipolar cascoding provides continuous gain control by adjustment of drain-source voltage to shift the NMOS differential pair from a saturation region operation and high gain to a triode operation and low gain. A simple control circuit is used in order to generate the desired exponential gain to linear control voltage characteristic that is stable over temperature and process. The shift from saturation to triode operation of the input NMOS differential pair simultaneously increases the input linearity as the gain is reduced.

Abstract: A differential integrator that uses a matched resistor array to reduce integrating currents and thereby realize a long time constant. The differential integrator includes a differential operational amplifier having inverting and noninverting amplifier input terminals, and inverting and noninverting amplifier output terminals, the amplifier output terminals form inverting and noninverting output terminals, respectively, of the differential integrator. The differential integrator also includes a noninverting differential integrator input terminal and an inverting differential integrator input terminal. The differential integrator also includes a resistor array that couples the noninverting differential integrator input terminal to the inverting and noninverting input terminals of the amplifier, and the resistor array also couples the inverting differential integrator input terminal to the inverting and noninverting input terminals of the amplifier.

Abstract: Amplitude-adjustable oscillator. The oscillator includes a feedback loop to control the amplitude of an oscillator output signal. The feedback loop includes a pair of clamping transistors, wherein base terminals of the clamping transistors are coupled to an adjustable voltage signal to prevent saturation of the oscillator circuit. The feedback loop also includes a filter to monitor the current flowing through the clamping transistors. The feedback loop also includes an amplifier to compare an output of the clamping transistors to a reference signal, and a reference generator to set an operating bias for the oscillator.