Abstract: A low noise quadrature mixer circuit for RF has an input stage which is a single ended to differential converter, where the cascode transistors each include two transistors with common emitter and base connections and separate collector outputs. The separate collectors serve as current outputs to drive the switching stages of the mixer. With two current outputs from both the positive and negative sides of the single ended to differential converter, this drives the emitters of two separate sets of cross coupled emitter coupled pair transistors that make up the output switching stages of the mixer. With the two sets of cross coupled emitter coupled pairs, one set is driven by an in phase local oscillator signal and the other is driven by a quadrature local oscillator signal. The resulting output signals are two intermediate frequency (IF) differential voltage output signals that are in quadrature (90.degree. out of phase with each other).

Abstract: A cordless phone configured to operate in both a scrambling mode and non-scrambling mode comprises a base station and a cordless handset terminal. Both the base station and the cordless handset terminal include voice scrambler circuits for scrambling and descrambling audio signals. Each of these voice scrambler circuits includes a bypass switch that when activated is adapted to couple audio signals from the input terminal of each scrambler circuit to the output terminal of each scrambler circuit via a bypass route. When the cordless phone operates in its non-scrambling mode, the audio signals are not affected by the internal circuitry of the voice scrambler circuits, leading to a substantially improved voice quality.

Abstract: Disclosed is an apparatus for reducing background noise in a telecommunications device, the telecommunications device including a microphone for receiving acoustic sights and generating corresponding electrical signals therefrom, the acoustic signals including voice signals and background noise signals. The apparatus of the present invention in one embodiment include an amplifier having an input for receiving the electrical signals from the microphone and an output, said amplifier operable to receive electrical signals at the first input and provide amplification to the electrical signals to produce amplified electrical signals. The amplifier is further operable to provide amplification at a first gain level and a second gain level, said first gain level exceeding the second gain level. The apparatus also includes a feedback device connected to the output of the amplifier and further operably connected to control the operation of the amplifier.

Abstract: Differential amplifier having multiple stages, each stage having the gain thereof set by digital control. The gain of each stage is individually controlled, thereby allowing wide dynamic range and gain. Each stage has a differential pair with multiple sets of gain-setting resistors in the emitters of the pair. By selecting which resistor set, or combination of resistor sets, is used, the gain of the stage is controlled. The result is a 4 stage, 0-45 dB gain amplifier for RF or IF applications, with the gain adjustable in 3 dB increments.