Abstract: The input stage of a radio receiver incudes a differential amplifier circuit, whose gain is adjusted by a voltage generated by an AGC circuit, and a mixer circuit. An attenuator stage with a predetermined attenuation coefficient is coupled between the input terminal of differential circuit and the input terminal of the mixer circuit. When the level of the input signal increases beyond a given value, the differential amplifier circuit is deactivated and the signal reaches the mixer circuit through the attenuator stage.

Abstract: A signal converter comprises a filter formed of a first ferromagnetic resonator which supplied with an input signal that is to be converted and produces a filtered signal having a first frequency, a local oscillator formed of an active element and a second ferromagnetic resonator connected to the active element, produces an oscillating signal having a second frequency, a mixer receives and mixes the filtered signal and oscillating signal and produces a converted signal, the first ferromagnetic resonator is formed of a first ferrimagnetic crystal, a microstrip line magnetically coupled to the ferrimagnetic crystal and a first D.C. bias magnetic field means which applies a first D.C. bias magnetic field to the first ferrimagnetic crystal, the second ferromagnetic resonator is formed of a second ferrimagnetic crystal, a second microstrip line is magnetically coupled to the second ferrimagnetic crystal, and a second D.C. bias magnetic field means which applies a second D.C.

Abstract: A cell enhancer for use by one cellular provider in a cellular radio-telephone system particularly in a cell including a diversity function includes a first amplifier system for amplifying both up-link and down-link signals between a first set of upstream and downstream antennas and a second amplifier system for amplifying at least the up-link signals between a second set of upstream and downstream antennas. The upstream antennas have a selected minimum correlation between them to ensure that the diversity at the cell site is maintained.

Abstract: A method for effecting communication between first and second antennas, includes the steps of (a) mutually displacing the antennas and determining received signal strength at each antenna and positioning said antennas accordingly to obtain a first quality level of communication therebetween; and (b) effecting a second quality level of communication as between the antennas, exceeding the first quality level, by defining a plurality of succeedingly diminishing search movement patterns for each of the first and second antennas, transmitting from the first antenna while displacing the second antenna in one such pattern and detecting the level of receipt of such transmitted energy. The second antenna is now placed in its location of maximum received signal level and transmits while the first antenna is displaced in one of the patterns and its level of receipt of transmitted energy is monitored. The first antenna is now placed in its location of maximum received signal level.

Abstract: An AFC/AGC circuit utilized in a receiving apparatus of a ground station for the satellite communication system comprising a digital AFC/AGC controller functioning such that;when the pilot signal is not received, the gain control voltage and the frequency control voltage are respectively set to appropriate values based on the predetermined data;when the pilot signal starts to be received, the gain and frequency control voltages are switched from the set values to the values obtained from the digital AFC and AGC processings, respectively;so long as the pilot signal is being received, the signal generated in the digital AFC and AGC processings are sampled by respective sampling clock signals and the gain and frequency control voltages are determined in accordance with the sampled data; andwhen the pilot signal stops being received, each of the gain and frequency control voltages is held at the value sampled by a last pulse of the sampling clock signal immediately before the stopping, respectively.

Abstract: A double-balanced waveguide mixer is disclosed that utilizes a quad-ridge waveguide and a quad-diode ring. In a down-converter version of the mixer, the input signal is applied to one pair of opposed ridges of the quad-ridge waveguide and the local oscillator signal is applied to the other pair of opposed ridges. The diode ring is coupled through capacitors to one pair of opposed ridges, and is directly connected to the other pair of opposed ridges. The intermediate frequency is tapped off at the junction between the capacitors and the diode ring.

Abstract: A dynamically reconfigurable multiplexer (7) has applicability in a space diversity communications system or a polarization reuse communications system. Multiplexer (7) may be situated on board a communications satellite or at the control nexus of a terrestrial microwave communications system. Multiplexer (7) comprises a set of N series-connected field reversible circulators (51). Coupled to one of the three ports of each circulator (51) is a channelizing filter (53), followed by an output isolator (54) and a high power amplifier (55). The electromagnetic energy rotating within each circulator (51) is commanded to move in either a clockwise or counter-clockwise direction, depending upon whether it is desired to access the channel (52) corresponding to said circulator (51) via a first energy source (1) or second energy source (2). An input isolator (43, 44) associated with each antenna (1, 2) absorbs unwanted energy emanating from the opposing antenna (2, 1).

Abstract: An antenna circuit includes a ferrite core around which a main coil and a negative feedback coil are wound, and a field effect transistor (FET) with its source grounded, and with a voltage induced in the main coil being applied across the gate and the source of the FET to thereby form an aperiodic circuit and the drain of the FET being connected through the negative feedback coil to a load.

Abstract: A communication system with fixed stations (FS), mobile stations (MS), and control stations (LS) is disclosed in which the control stations are interconnected by transmission paths and have additional, closed transmission paths connected to them. In the transmission paths, the fixed stations (FS) are arranged in series. Communication is on a time-division-multiplex basis. The control stations (LS) assign the TDM channels to the individual mobile stations (MS) via the fixed station (FS) in charge of the respective mobile station.

Abstract: A mobile radio data communication system wherein a fixed unit transmits an operation command code sequence for an instruction to an operator having a portable unit. A speech synthesizer of the portable unit is responsive to the command code sequence to generate a speech signal which is audible to the operator. In response to the audible instruction, the operator replies by voice, and the speech signal is supplied to a speech recognition circuit which sends a code associated with the speech signal to the fixed unit.

Abstract: A portable unit that may be called from a base station through a radio control channel by a succession of terminating call signals that is sent through the control channel from the base station to the portable unit for a first or restricted time duration (T.sub.1), selected in consideration of a battery saving period of a battery saving operation carried out in the portable unit. Within the battery saving period, the portable unit is put into transient active and inactive states during a first time interval and a second time interval, respectively. Selection is made so that the first time duration is longer than the second time interval to receive at least one of the terminating call signals within the first time duration in the portable unit. The base station monitors an acknowledgement signal for a second time duration (T.sub.2) after the lapse of the first time duration and interrupts the control channel when the acknowledgement signal is not received within the first and the second time durations.

Abstract: The invention relates to a circuit arrangement for a home-entertainment apparatus which, by means of a memory and a timer, ensures that the apparatus can operate correctly only if a date has been entered. If this is not the case, the timer will disable the apparatus after a specific time interval.

Abstract: A demodulator of the type employed in a "zero-IF" system uses a local oscillator for providing quadrature output signals at the center frequency of a received signal to be demodulated. The demodulator has first and second mixers for separately mixing the received signal with the quadrature signals to provide a first and second output signal each in quadrature at the outputs of said mixers. These signals are low pass filtered. The demodulator includes third and fourth mixers with each mixer respectively receiving at an input one of the first and second low pass signals. At another input the mixers receive third and fourth signals. The third and fourth signals are derived from mixing a variable controlled oscillator (VCO) signal with local oscillator quadrature signals the frequency of said is independent of the center frequency of the received signal.

Abstract: Data receiving equipment is trained by training signal of optimum length through the steps that the sending equipment sends data signal after sending the training signal having a length corresponding to the characteristics of a line connected thereto and containing information indicating the length and the receiving equipment trains itself with the received training signal and detects, using the information indicating the length, the timing when the training signal changes to a data signal.

Abstract: A frequency conversion circuit having first and second input signal terminals, and first and second output terminals includes a plurality of non-linear elements, each one having a pair of input electrodes and an output electrode. The first input electrode of each non-linear element is successively interconnected by a two port input coupling means, said input coupling means having a first end coupled to the first input signal terminal and a second end terminated in a terminating impedance. The output electrode of each non-linear device is successively interconnected by a two port output coupling means coupled between the pair of output terminals. An input signal is fed to the first input signal terminal and is coupled to the input coupling means and a portion of such signal is fed to the first input electrode of each non-linear device. Each portion of the input signal is provided with a successive phase shift as it propagates along the input coupling means.

Abstract: In a microwave push-pull frequency converter having the form of a waveguide for effecting frequency conversion of a broadband microwave signal, which converter includes a converter module composed of a waveguide section and a pair of semiconductor mixer elements disposed in the waveguide section for effecting frequency conversion between a high frequency microwave signal and a low frequency microwave signal without intermediate frequency conversion, the converter further including a waveguide filter for the low frequency microwave signal connected to one side of the module, the waveguide filter includes a plurality of ridged waveguide sections and a plurality of blocking waveguide sections interposed between, and coupling, the ridged waveguide sections, and the converter module includes fastening devices supporting the semiconductor mixer elements and configured to give the coverter module the form of a ridged waveguide which permits the high and low frequency microwave signals to pass in a single mode.

Abstract: The circuit arrangement in a communication system which is protected by subscriber-specific passwords having a memory which contains all the possible passwords and a comparator which compares each received password with the memory content. A monostable delay circuit with a subsequent logic combining gate, are connected to the output of the comparator (2) via an input gate (5). The monostable delay circuit and the logic combining gate are such that in the presence of an energizing signal applied to a special input (C), when there is non-agreement between the received and the stored passwords the monostable delay circuit starts and during operation inhibits the logic combining gate, while when there is agreement the logic output gate (6) is enabled. Such a circuit arrangement can be provided before each selector stage of a switching system of before each accessible channel of a mobile radio system.

Abstract: A process and apparatus for simultaneously broadcasting a first intelligence signal with a plurality of second intelligence signals is disclosed. The transmitter performs the following steps: multiplexing the plurality of second intelligence signals into a single signal to form a first modulating signal; frequency modulating a first radio frequency carrier signal with the first modulating signal to form a second radio frequency carrier signal; amplitude modulating the second radio frequency carrier signal using the first intelligence signal as a second modulating signal; and broadcasting the resultant single radio frequency signal out over a transmitting antenna.

Abstract: The locating function of a cellular mobile radio telephone system is implemented so that, when the locating radio detects a sustained change from a very low signal quality or amplitude (indicating background noise rather than an active call in an adjacent cell) to a higher quality or amplitude (indicating the start of a call in one of the adjacent cells), the radio will modify its filtering process so that previous sample values (which can be attributed, for example, to noise before the start of the call) will not be used in the averaging process. The result of this improvement is that values reported from the locating radio during the initial portion of the call (0 to 20 seconds) will not be reported artifically low. This allows the system to make decisions about handoff during this initial portion of the call. Additionally, rather than having the locating radio take equal samples from each of the possible voice channels, in accordance with the invention, there are two scanning tasks.

Abstract: A radio communication device comprises a portable communication device and a power amplifier device adapted to accommodating the portable communication device thereinto for amplifying a transmitter output therefrom. The radio communication device further comprises a detector circuit for detecting that an electrical coupling between the portable communication device and the power amplifier device, thereby effecting a control such that the transmitter output power level is kept at a minimum input level required for the power amplifier device. Thus, this can suppress exceesive heat generation in the communication device when the portable communication device is used by being accomodated in the power amplifier device.