Abstract: A white clip circuit, formed as an integrated circuit, includes a negative impedance converter which in use is operative to increase the sensitivity of an inverting long-tailed pair of transistors adapted to invert the signals and feed them back to the input in order to control the clip level and to enable it to be effective at a relatively low level.

Abstract: A ball grid array arrangement comprises a dielectric multilayer substrate, in a lower metallization layer of which is disposed an array of solder balls. A passive circuit element is integrated into at least one of the metallization layers. The arrangement may be either a discrete component consisting of a triplate transmission-line resonator or interdigitated filter integrated into an inner metallization layer and defined by that layer in conjunction with adjacent layers, or it may take the form of an IC carrier or multichip-module carrier having such transmission structures situated within a central die-attach area of the substrate and having also a peripheral area containing bonding structures for the mounting of at least one chip or chip module. There will normally be at least two groups of such bonding structures, and a passive circuit element in the form of an inductor may be formed in the upper metallization layer between adjacent groups of bonding structures.

Abstract: In an amplifier circuit arrangement in which series resistive feedback is utilized in the main amplifier to minimize distortion, and a feedback amplifier is provided in a path from the output of the arrangement to the series feedback path effectively to boost the value of the feedback resistor, a further amplifier is arranged to provide positive feedback to the resistive load circuit of the main amplifier effectively to boost the value of the resistive load.

Abstract: An antenna arrangement is provided in which a slot antenna is attached to the surface of an equipment case made of a dielectric material, there being provided also a ground plane spaced a small distance apart from the case and behind the antenna. The equipment may be a personal computer, e.g. a notebook computer, and the antenna, which may take the form of a copper foil, may be attached to the lid of the computer by an adhesive on its rear surface. The ground plane may, in this case, take the form of an existing display backplane. The invention provides for the realization of a compact antenna arrangement due to the effect of the case dielectric on the effective electrical length of the slot antenna.

Abstract: In a frequency modulated digital radio transmission system, frequency differences between transmitter and receiver which give rise to DC offsets at the output of the demodulator are countered for any one data transmission by establishing a frequency controlling or DC level controlling signal during a preamble sequence having a known constant DC component, such as the sequence 10101 - - - used for clock or data synchronization, and retaining that controlling signal substantially unaltered for use during the remainder of that data transmission.

Abstract: In a video signal distribution system in which a plurality of video signals are modulated onto individual carrier signals spaced over a band of frequencies to form a composite signal for transmission over cables of the system, a point-to-point radio link forming part of the distribution system is provided in which the composite signal is transmitted as double side band phase modulation of a single microwave carrier signal.

Abstract: A direct conversion Binary FSK radio receiver has an AFC loop comprising an Exclusive-Or phase detector 104 responsive to the I.sub.3 and Q.sub.3 signals. I and Q filters 100, 101 are not identical but have different frequency-phase characteristics such that their phase shifts are identical when the local oscillator 102 is correctly tuned and differ when the local oscillator is off-tune. Detector 104 detects the change of phase and applies a control signal to local oscillator 102 such as to return the local oscillator frequency to the correct value. Alternatively, identical filters may be used in the I and Q channels, circuits having different phase shifts being coupled between the I.sub.3 and Q.sub.3 signals and the inputs of the phase detector 104.

Abstract: In a multilayer metallisation/dielectric structure on a silicon substrate a trimmable capacitor is formed between two of the higher metallisation layers, with one layer being segmented and the individual segments connected by way of one or more vias and respective narrow links to one terminal of the capacitor. The narrow links are formed from titanium tungsten on the oxide isolated silicon substrate.

Abstract: A radar transmitter/receiver arrangement for use, for example, in automotive vehicle control in which R.F. energy from a frequency modulated oscillator is applied to an antenna for transmission and to one input of a mixer by way of a rat-race device, and RF energy reflected from a target and received at the antenna is applied to another input of the mixer by way of the rat-race device.

Abstract: In a D.C. restoration circuit for a digital FM radio receiver, in which demodulated signals may be presented at the output of the demodulator as low-level differential signals superimposed on a variable D.C. level, the differential signal paths are capacitively coupled to the inputs of a comparator, and the voltage excursions at these inputs are clamped when the voltage between the inputs exceeds a predetermined value.

Abstract: An amplifier arrangement comprising a plurality of similar amplifier stages to which input signal voltages are applied in common, the output signal voltages being summed to retain bandwidth at the expense of gain compared with cascaded stages. The individual stages of the arrangement may be cascoded amplifier stages.

Abstract: An overvoltage protection circuit employs a series of semiconductor switching elements, each element having a control terminal and two main conduction terminals, in a totem pole configuration and two potential dividers whose tapping points feed, respectively, the control terminals and the main terminal junctions of the switching elements. Both the series of switching elements and the two potential dividers are connected between a reference node (zero volts) and a node to be protected from an electrostatic discharge. The resistive elements of the potential dividers are so arranged that, in the absence of a static discharge, all switching elements are cut off and experience a substantially equal voltage across the respective main terminals. In this way, the circuit may be usefully employed in integrated circuits which are based on a low-voltage integration process but which have also a high-voltage-supply rail (e.g. 30 V). The switching elements may be bipolar transistors, and preferably Darlington pairs.

Abstract: A Doppler microwave sensor for a vehicle alarm employs a mixer stage and a signal-processing stage on a printed circuit board, the printed circuit board having a ground plane containing a slot antenna which is coupled to the mixer stage. The ground plane is electrically connected to an electrically conductive enclosure which is disposed behind the slot antenna and encloses the component parts of the mixer and signal-processing stages. A dielectric lens may be placed over the slot antenna to provide a transmission beam pattern which is configured to the vehicle in which the sensor is to be used. In a preferred embodiment, the mixer stage is based arounda self-oscillating mixer arrangement in which the active element is a bipolar transistor and a single antenna is employed both to transmit the oscillator signal and to receive the Doppler-shifted return signal.

Abstract: An equalisation arrangement compensates for multipath phase and amplitude distortion effects in a transmission channel by first measuring such distortion effects as they occur over time in a calibration phase, thereby obtaining phase and amplitude compensation factors, then applying these factors to a correcting circuit situated in the signal path of the receiver at the appropriate times during a subsequent data transmission phase. Calibration is achieved by feeding a received calibration signal to an amplifier, preferably a successive detection logarithmic amplifier (26), comparing the phase of the limited linear output of the logarithmic amplifier with a delayed version of itself (30, 28), and using the amplitude information (39) in the logarithmic output (72) of the logarithmic amplifier (26) and the phase-change information (35) resulting from the phase comparison to compute the phase and amplitude compensation coefficients.

Abstract: In a video signal distribution system in which a plurality of video signals are modulated onto individual carrier signals spaced over a band of frequencies to form a composite signal for transmission over cables of the system, a point-to-point radio link forming part of the distribution system is provided in which the composite signal is transmitted as double side band amplitude modulation of a single microwave carrier signal.

Abstract: A preamplifier circuit arrangement for a magnetic or magneto resistive transducer, such as a record/replay head, in which a cascode preamplifier stage, and a stage providing a floating reference voltage for a following amplifier, are linked by an emitter coupled pair of transistors, one in each stage, such that the d.c. currents in the two stages flow in common through the transducer.

Abstract: An automatic frequency control (AFC) arrangement for use in a symmetrically modulated, homodyne FSK receiver or transceiver forms a value representing the baseband frequency for each of demodulated data states "1" and "0" by measuring the frequency (54, 56; 80, 82) during the appropriate data state, stores it (58, 60; 84, 86) during the opposite data state, and subjects the two stored values to a subtraction process in a difference-forming means (64, 88), the output of which is then used to effect control of the frequency of the local oscillator (32). The AFC arrangement may be realized by analogue techniques, using one or more frequency-to-voltage converters and sample-and-hold units, or by digital techniques, using one or more counters and latches, or by software techniques.

Abstract: An arrangement for making fatigue-free external connections to a device mounted on a direct copper bonded substrate, in which one or more connector tubes are brazed to respective copper areas on the substrate before the device is mounted on the substrate, and external connections are made by soldering leads or bus bars into the tubes.

Abstract: In a static random access memory made up of six-transistor memory cells arranged in rows and columns, an arrangement for detecting open circuit or "soft" defects in the individual inverters of a memory cell includes lowering the supply voltage of a cell under test to overcome the clamping effect of a feedback inverter, applying input signal voltage changes to one of the bit lines associated with the cell, and testing for the expected voltage changes on the other bit line associated with the cell.

Abstract: A contents addressable memory comprising an array of contents addressable memory cells arranged in rows and columns, each row of the array having a respective case between address bit values of a data word or words to be retrieved from the memory and bit values held by the cells of the respective row, and a chain of cells associated one with each match line to indicate which, if there are more than one, of the match lines indicating a match is of the highest priority.