Kabushiki Kaisha Toshiba

Semiconductor Technology Academic Research Center

Hiroshi Tanimoto

Tetsuro Itakura

Takafumi Yamaji

Shoji Otaka

Mikio Koyama

Hiroshi Tsurumi

Takashi Ueno

Hiroshi Yoshida

Ryuichi Fujimoto

Osamu Watanabe

Koji Suzuki

Hisashi Yamada

Satoru Yoshida

Akira Yasuda

Zdzislaw Czarnul

Minoru Tanaka

Mikio Hayashihara

Satoshi Arai

Hiroshi Horiguchi

Myles H Wakayama

Makiko Okumura

Chikau Yakahashi

Mikio Hayashibara

Masayuki Katakura

A fully-differential amplifier able to operate at a low power supply voltage and provided with a common-mode signal suppression function is disclosed. This fully-differential amplifier is provided with a first fully-differential amplifier configured by a single-stage configuration inverting amplifier and canceling out the common-mode signal of the input side by a feedforward means and a second fully-differential amplifier configured by a single-stage configuration inverting amplifier and canceling out the common-mode signal of the output side by a feedback means, the output of the first fully-differential amplifier being connected to the input of the second fully-differential amplifier.

Fully-differential amplifier

An orthogonal demodulating section converts the frequency of received signals to the lower range after rejecting an image band thereof by an RE filter. An image rejecting section rejects the image band of the orthogonally converted output. It allows enough of an image rejecting degree to be obtained. An A/D converter section converts the whole range into a digital signal and an orthogonal demodulating section demodulates a desirable channel by means of digital processing. Then, a channel selecting section selects and outputs the desirable channel.

Receiver

An orthogonal demodulating section converts the frequency of received signals to the lower range in batch after rejecting an image band thereof by an RF filter. An image rejecting section rejects the image band of the orthogonally converted output. It allows an enough image rejecting degree to be obtained. An A/D converter section converts the whole range into a digital signal and an orthogonal demodulating section demodulates a desirable channel by means of digital processing. Then, a channel selecting section selects and outputs the desirable channel. It then allows wide-bands to be received in batch, flexible processing to be achieved by the digital processing and an enough image rejecting degree to be obtained.

A receiver having a function of a direct current offset, and including a receiving section for receiving a radio frequency signal, an analog signal processing section for amplifying, band-converting and frequency-converting an analog signal inputted from the receiving section, and an AD converting section for converting an output of the analog signal processing section from an analog signal to a digital signal. Also included is a digital signal processing section for processing the digital signal converted by the DC converting section. The receiver further includes an offset detecting element, provided in the digital signal processing section, for detecting a direct current offset signal produced in the receiving section or a frequency converting section, an offset holding element, provided in the digital signal processing section, for holding the direct current offset signal detected by the offset detecting element, a DA converting section for converting the direct current offset signal detected by the digital signal processing section into an analog signal, and a first offset correcting element, provided in the analog signal processing section, for correcting the analog signal on the basis of the direct current offset signal converted by the DA converting section into the analog signal.

Receiver having DC offset decreasing function and communication system using the same

A frequency converter includes a multiplying circuit, a load circuit, and an output buffer circuit. The multiplying circuit is arranged to multiply an RF signal and an LO signal and output a difference frequency signal with a frequency, which is the difference between the frequencies of the two signals, from its output terminal. The load circuit is arranged to connect the output terminal of the multiplying circuit to a power supply. The output buffer circuit is arranged to have an input terminal connected to the output terminal of the multiplying circuit, and an output terminal for outputting a signal to the next stage. A notch circuit for removing an undesired signal frequency component is combined in the load circuit. The notch circuit has an impedance characteristic in which the impedance is abruptly reduced to provide a valley point at the undesired signal frequency.

Frequency converter

A frequency converter including a mixer circuit which inputs a local oscillation signal and a radio-frequency input signal modulated for communication of information, and performs frequency conversion. A buffer amplifier is higher than a desired signal frequency band, and has a low-pass passage characteristic of cut-off frequency lower than an adjacent channel carrier frequency.

There is disclosed an impedance conversion circuit called a regulated cascode circuit in which a parasitic capacity deteriorating frequency characteristics is reduced during operation up to about several hundreds of megahertz or higher frequencies. In the impedance conversion circuit comprising two regulated cascode circuits in which active elements and reverse amplifiers are interconnected with a feedback applied thereto, a capacity element is disposed between a control end of one active element and an output end of the other active element.

Impedance conversion circuit

By disposing the first filter circuit and the second filter circuit whose connection structures are the same and whose element values are different on an integrated circuit, a phase shifter with output signals whose frequency characteristics and errors of phase shift characteristics equally vary can be accomplished.

Phase shifter

A frequency converter includes: a signal synthesizer element for inputting first and second input signals to synthesize these signals and for outputting a synthesized signal, from which noises even times as large as the frequency of the second input signal are removed; an amplitude limitation amplifier element, composed of a differential amplifier circuit, for amplifying the synthesized signal outputted from the signal synthesizer element to output an amplified signal having a constant amplitude; and a filter for inputting the amplified signal outputted from the amplitude limitation amplifier element, to remove an unnecessary signal component to produce an output a baseband signal including only a desired signal component. In addition, a radio receiver using the frequency converter of such a construction is designed to input the output of a local oscillator to a variable attenuator or a variable gain amplifier, to input the output of the variable attenuator or the variable gain amplifier as the first input signal to the frequency converter so as to perform the gain control. Thus, not only is self-mixing, a common problem in direct conversion receivers, prevented, but also, because a smaller local oscillation driving signal is required, power consumption is significantly reduced.

Frequency converter and radio receiver using same

A balanced amplifier includes first and second multi-input single-ended output differential amplifiers having matched characteristics and a feedback circuit. The feedback circuit connects differential input terminals and output terminals of the first and second multi-input single-ended output differential amplifiers so that all of the differential input terminals of the first and second multi-input single-ended output differential amplifiers are virtually shorted.

Balanced amplifier using single-ended output operational amplifiers

A noise analyzing apparatus includes an input unit for inputting a structure of an autonomous system, parameter values and analysis conditions, a periodic steady-state solution calculating unit for calculating a periodic steady-state solution of the autonomous system, a noise source adding unit for adding a noise source to a periodic linear time-variant system obtained by linearizing the autonomous system around the periodic steady-state solution, a time-variant transfer function calculating unit for calculating, for each noise source, a time-variant transfer function of the periodic linear time-variant system to which noise sources are added, a reflected component calculating unit for adding power of a time-variant transfer function reflected to a frequency to be observed, and an output unit for outputting as a result of analysis relating to noise based on results of calculations by the above-described calculating units.

Noise analyzing apparatus for analyzing noise of autonomous system by

In an FDNR type active filter fabricated on an integrated circuit, an FDNR circuit is provided wherein one ends of a first capacitor and an impedance element are connected to an inverted input of an operational amplifier, one ends of the impedance element and a second capacitor are connected to an output end of the operational amplifier, and the other ends of the first and second capacitors are connected to each other. To the impedance element, resistors are connected in series. To the connecting end of the resistors, one end of another resistor is connected, the other end thereof being grounded in an alternating current form. The capacity value of the second capacitor is greater than that of the first capacitor.

Electronic circuit and filter device using same

A gain switching circuit comprises first and second gain stages connected in parallel between the input terminal and the output terminal, and a control unit for allowing the first and second gain stages to be selectively operative, wherein the first and second gain stages respectively include input sections in which input impedance values viewed from the input terminal are substantially equal to each other, and output sections in which output impedance values viewed from the output terminal are substantially equal to each other. By this configuration, a gain switching circuit and a radio apparatus using such a gain switching circuit adapted so that input/output impedance does not fluctuate are provided without implementing switching between gain stages.

Variable gain circuit and radio apparatus using the same

A local signal of a predetermined frequency is supplied to an input terminal of a local signal input section. The local signal is applied to a control input terminal of a variable current supply and, in accordance with the local signal, a current is output from a variable current supply and sent to a phase-shifting section. The phase-shifting section includes two resonance circuits each comprised of a capacitor and inductor. The two resonance circuits are connected in parallel with a linear element constituting the local signal input section to output first and second output signals of the same frequency as that of the local signal and whose phases are shifted by a predetermined amount. The respective output signals of the phase-shifting section are output to a next stage through a signal output section comprised of two sets each of a current supply and transistor.

Phase shifter and communication system using the phase shifter

A local signal of preset frequency is supplied to an input terminal of a signal input section. The local signal is supplied to a control input terminal of a variable current source, a current corresponding to the local signal is output from the variable current source, and the current is supplied to a phase shifting section. The phase shifting section includes an integrator constructed by a capacitor and a resistor connected in series and a differentiator constructed by a resistor and a capacitor connected in parallel. As parallely connecting the phase shifting circuit with a linear element of which the signal input section consists, the phase shifting section outputs first and second output signals which has the same frequency as the local signal and whose phases are different from each other by 90.degree.. The output signals of the phase shifting section are output to the next stage via an orthogonal signal output section constructed by current source and transistors.

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Kawasaki, Japan

Hiroshi Tanimoto