Matsushita Electric Industrial Co., Ltd.

Makoto Taromaru

Hisao Koga

Shingo Sagata

Kiyoyuki Suenaga

Koji Muraoka

Kouta Okada

Hiroyuki Gondo

Tomohiro Shika

A diversity receiver with simplified construction, excellent receiving signal quality even with very low fading speeds wherein, on the basis of a signal from a receiving unit capable of detecting the receiving signal intensity, an antenna changeover is effected when the receiving signal intensity falls below a changeover threshold value. When, at the termination of a first lapse time from the first antenna changeover, the receiving signal intensity is below that immediately before the first antenna changeover, an antenna changeover is again effected and any antenna changeover is prevented from being effected for a second lapse time from the second changeover. The second lapse time is set to be longer than the first lapse time.

Diversity receiver

The invention aims at adaptive array diversity reception of high convergence speed of combined weight by a simple signal processing, in a receiver by time division transmission system. Signals received by antennas (branches) are converted into base band signals in a receiving circuit, and are combined by a complex multiplying section and complex adder. The weight of the complex multiplying section is calculated by a weight calculating section. In the weight update algorithm of the weight calculating section, the step size in the least mean square is variable. That is, the initial value is set at a large value, and is decreased according to the lapse of time in each time slot, and is initialized at every change of time slot. As a result, by the same amount of calculation as in ordinary least mean square, the convergence speed of weight updating can be enhanced.

Receiver

In a diversity receiver, an averaging circuit produces a short-time average value of an instantaneous value of a receiving electric field intensity at a receiving section. A ROM produces an appropriate threshold value corresponding to the short-time average value from the averaging circuit. A threshold decision circuit compares the threshold value produced from the ROM with the instantaneous value of the receiving electric field intensity and controls an antenna switch to switch antennas when the instantaneous value decreases below the threshold value.

A frequency modulator includes a reference frequency oscillator, a voltage controlled oscillator provided with a control input terminal and a modulation input terminal, a frequency divider for dividing an output of the voltage controlled oscillator, a phase comparator for generating an output signal corresponding to a phase difference between an output of the reference frequency oscillator and an output of the divider, a first filter having an input terminal and an output terminal, the input terminal thereof being connected to an output terminal of the phase comparator, while the output terminal thereof being connected to the control input terminal of the voltage controlled oscillator, and a second filter having an input terminal and an output terminal, the input terminal being inputted a modulating signal and the output terminal being connected to the modulation input terminal of the voltage controlled oscillator. The second filter has a lower amplitude characteristics in a low frequency range within a modulation frequency band than that in a high frequency range within the same.

Frequency modulator

An optical disk apparatus equipped with an objective lens for converging light from a light source onto a track formed on an optical disk, the objective lens being arranged to be movable and an error detecting section for detecting a difference in position between the light converged by the objective lens and the track on the optical disk. Included in the servo section of the optical disk apparatus are an amplifier for amplifying an output of the error detecting section with an amplification factor which is variable and a filter circuit for cutting off a frequency component of an output of the amplifying means, the cutoff frequency being variable. On the basis of the output of the filter circuit, a moving device moves the objective lens so that the difference between the converged light and said track is reduced. The amplification factor of the amplifier and the cutoff frequency of the filter circuit are determined in correspondence with the position of the objective lens. These amplification factor and cutoff frequency are prestored in a memory so that the corresponding amplification factor and cutoff frequency are read out therefrom in accordance with the current position of the objective lens.

Growing community of inventors

Fukuoka-ken, Japan

Makoto Taromaru