Nec Corporation

Nec Electronics Corporation

Hisaya Ishihara

Yukio Okazaki

A quadrature modulator includes a local oscillator oscillating at an oscillation frequency equal to 4/(2N+1) times a carrier frequency where N is a natural number, a frequency conversion block for multiplying the oscillation frequency by a factor of (2N+1)/2, a divider for dividing the multiplied oscillation frequency to output a pair of orthogonal carrier waves, first and second multipliers for modulating the carrier waves with a digital baseband signal, and an adder for adding the modulated carrier waves to output a carrier signal having the carrier frequency. The frequency conversion block includes a divider for dividing the oscillation frequency, N frequency mixers cascaded from one another and a band-pass-filter, which are cascaded in this order.

Quadrature modulator

There is disclosed a phase shifter using a polyphase filter, which achieves a broad band, suppresses errors in both amplitude and phase, and achieves low power consumption. A driving section includes a voltage-to-current conversion circuit for converting a voltage value of an input signal Si into a current value, and outputting an input current signal Ci. An RC polyphase filter outputs a corresponding polyphase phase-shifted current signal Co according to supplying of the input current signal Ci. A load circuit includes a polyphase current-to-voltage conversion circuit for converting a current value of the polyphase phase-shifted current signal Co into a voltage value, and outputting an output signal Vo.

Phase shifter with an RC polyphase filter

The differential amplifier circuit of the invention comprises operational amplifiers and having the negative inputs connected to input terminals and respectively, transistors and having the bases connected to each of the outputs of the operational amplifiers and respectively, constant current sources and connected between each emitter of the transistors and and a ground terminal respectively, constant current sources and connected between each collector of the transistors and and a power supply terminal respectively, a resistor connected between the collectors of the transistors and , transistors and having the emitters connected to each emitter of the transistors and respectively and the bases commonly connected to each other, and load resistors and connected between each collector of the transistors and and the power supply terminal respectively.

Differential amplifier circuit

A variable gain amplifier circuit enables the minimum gain to be established easily without changing DC voltage of output terminal at the time when the gain is to be variable. The variable gain amplifier circuit is provided with an input differential circuit consisting of a first and a second transistors whose respective bases are connected to input terminals, and whose respective emitters are connected to constant-current source, and a gain control differential circuit consisting of a third to an eighth transistors,and,which are connected mutually such that base, collector, and emitter become required relationship. Further, the variable gain amplifier circuit is provided with a first load resistor connected between collector of the third, fifth, and seventh transistors,and,and a first power supply terminal, and a second load resistor connected between collector of the sixth, eighth, and fourth transistors,and

Variable gain amplifier circuit

A phase shift circuit includes a CR phase shifter for receiving an input signal to output a pair of first signals having a 90.degree. phase difference therebetween, a pair of variable-gain amplifiers for receiving the first signals to output a pair of second signals, an adder for adding both the second signals to output a sum signal, a subtracter for outputting a difference signal between the second signals, and a phase error detector for detecting the phase difference between the outputs from the adder and the subtracter to output a pair of gain control signal based on the phase difference. The gain control signal is fed-back to the variable-gain amplifier to control the ratio between the gains of the variable-gain amplifiers.

Growing community of inventors

Kanagawa, Japan

Hisaya Ishihara