Blaupunkt-werke Gmbh

Kurt Wiedemann

Harald Bochmann

Heiko Brushaber

A modularly-designed FM vehicle radio for operation in connection with a plurality of antennas is disclosed, where the summing circuit consists of a series connection of the secondary coils of the output transformers of the input stages.

FM vehicle radio with modular phase shifters

A VHF radio receiver intended for mobile use, e.g. in a car, features inputs from multiple antennas. Each antenna signal is mixed with a locally-generated oscillator signal; the resulting mixed signals are added, with controllable phase position, to form a summation signal. Alternate frequencies, as defined by the Radio Data System (RDS) international standard, are stored. At periodic time intervals, momentary switchover is made to alternate frequencies to measure their reception quality and to store this parameter. Whenever the originally-tuned frequency provides inadequate reception quality, a control circuit 19 switches over to the best of the alternate frequencies, so quickly that the changeover is almost imperceptible to the listener.

Receiver with multiple antennas

To increase the fidelity of radio reception in a moving receiver, for example a car radio, the signals received from various antennas on the radio are mixed with a carrier in the receiver, and the resulting mixed signals, directly and 90.degree. phase-shifted, are added to a summing signal, in which, additionally, the phase positions of the direct and 90.degree. phase-shifted signals are changed in dependence on the phase difference between the respective intermediate frequency mixed signal and the overall summed signal in a direction to maximize the summed signal (u.sub.s).

Diversity radio receiver for use with multiple antenna, particularly car

In a circuit which matches the speaker input signal in a car radio to the then-present noise level, an additional RC circuit is interconnected between the speaker input terminal and the input of the volume control element. Sudden increases in the speaker input voltage following a modulation pause which cause a high increase in the gain of the volume control circuit will counteract this gain, thereby preventing the excessive increase in speaker sound output following such a modulation pause which took place in the known circuits. Zener diodes to limit the voltage at the volume control elements in dependence upon the battery output voltage and to a value such that the output stage driving the speaker will not be overdriven are also provided.

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Hildesheim, Germany

Kurt Wiedemann