Abstract: An Insulated Gate Bipolar Transistor has a gate in the form of a trench positioned in a p region in a silicon body. The device operates in a thyristor mode having a virtual emitter which is formed during operation by the generation of an inversion layer at the bottom of the trench within the p region. The device is inherently safe and turns off rapidly as removal of a gate signal collapses the emitter. As the trench gate is situated within the p region, it can withstand high voltages when turned off as the reverse electric field is prevented from reaching the trench gate.

Abstract: A system comprises an encoder, a precoder, a PRML channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies encoding such that the code string after passing through the precoder has a Hamming distance greater than one to eliminate error events with a small distance at the output of the PRML channel. The present invention also provides codes that after precoding have Hamming distance of 2 and 0 mod 3 number of ones. These codes when used over a PRML channel in an interleaved manner preclude +/-( . . . 010-10 . . . ) error events and error events +/-( . . . 01000-10 . . . ). The code string also has a predetermined minimum number of ones at the output of the PRML channel to help derive a clock from the input signal.

Abstract: A frequency synthesizer comprises a direct digital frequency synthesizer (DDFS), which provides in-phase and quadrature sinewave signals at a preset frequency from digital analogue converters respectively, and a balanced mixer. The balanced mixer provides an output signal having a carrier frequency twice that provided by DDFS and reduced levels of spurious signals. A signal having a desired frequency is generated by controlling the DDFS to generate sinewave output signals at half the desired frequency. The reduced levels of spurious signals obtained by the arrangement allows improved signals for use in, for example, local oscillator applications.

Abstract: An error correction circuit compensates for baseline wander which can occur when a data signal is passed through a DC isolation stage. The data signal, and its inverse are compared with a common reference level, and the error signal modifies the charge on a capacitor which forms part of a pair of negative feedback loop to control the baseline level.

Abstract: An amplifier comprises a common-base transistor 1 and a common-emitter transistor 2. The transistor 1 is arranged to receive an input signal applied to an input terminal 8 by an inductor 12 connected to its emitter. The transistor 2 is arranged to receive the input signal by a capacitor 13 connected to its base electrode. The transistors 1 and 2 are biased by a current mirror arrangement comprising a transistor 3 and a current source 16. Differential current output signals are provided on the collectors of the transistors 1 and 2.

Abstract: System X telecommunications system has a private circuit employing a switched connection, the circuit connecting from an originating subscriber to a terminating subscriber via an original directory number, and is controlled so that when the connection is terminated, an attempt is made to re-establish the connection from the originating subscriber by use of an alternative directory number where an indication is received that a further call may be successful, the attempt to re-establish the connection is repeated using the original and alternative directory numbers alternately until the call is re-established.

Abstract: A multiple function, electromagnetically shielded optical module employing flip chip bonded semiconductor lasers. The module positions a series of opto electronic dies on guides provided on an optical source. The dies may be simply stacked upon one another to form a passively aligned module. The shielding substantially reduces electrical cross talk and other sources of electromagnetic interference.

Abstract: To provide trimmable inductor structure for a multichip module, direct-chip-attach or surface mount assembly in which an inductive element is formed on or near a surface of the assembly, a planar chip of dielectric or ferrite material is mounted over the inductive element, this chip having on its upper surface a trimmable metallization layer, which may for example be patterned in concentric rings or in a spiral.

Abstract: A microwave frequency Doppler vehicle intruder alarm comprises an oscillator 3, a mixer 2 and an amplification stage 4, 5 having its output applied to a low-pass filter 7, whose output is split into two branches. A first branch, comprising a rectifier diode and a comparator, provides a signal on its output when a significant level of non-carrier microwave signals is received. This branch is sensitive to signals having Doppler frequencies of 0-200 Hz, which includes the intruder indicative frequencies. A second branch, comprising an amplifier 8, a high pass filter 9, and a comparator 10, provides an output signal on the detection of a significant level of signals in the 40-200 Hz band, which frequencies are indicative of externally generated interference. A logic element 15 mutes the output of the alarm when the second branch indicates the presence of externally generated interference. An antenna arrangement (FIG.

Abstract: In wireless local area networks utilizing frequency-hopping between different channels spaced over an allotted frequency band, two or more groups of transceivers in close proximity may be arranged to operate satisfactorily with the full bandwidth available to each by arranging that their hop sequences are kept separate. This may be achieved by arranging for the hop sequence of one group or of each group to skip at intervals from one point to another in the sequence, chosen at random.

Abstract: An output buffer of an integrated circuit arranged to be energised from a supply source providing predetermined potentials to supply conductors of the integrated circuit, comprises a potential divider R.sub.1, R.sub.2, R.sub.3 to define reference levels V.sub.1, V.sub.2 having a reduced swing compared to the supply levels V.sub.DD and 0, which reference levels are transferred to an output node V.sub.out, so that the reference potentials are unaffected by the loading of the output node, which the reduced voltage swing reduces pick-up caused by switching of the output buffer.

Abstract: In a single-chip multistandard video modulator arrangement in which audio signals for transmission with video signals are first modulated onto a subcarrier and then combined with the video signals for modulation onto a VHF or UHF main carrier, the modulated subcarrier signals are passed through a high-pass filter before being combined with the video signals in order to reduce the amplitude of any audio frequency components, and the resulting variations in main carrier amplitude, which tend to produce "sound in vision" effects.

Abstract: An amplifier, suitable for radio frequency applications, has good noise properties because of a special transistor configuration. A pair of transistors is connected in a cascode configuration, to overcome the Miller effect. The transistors have their bases driven by a common current source. The main current paths from ground to each of the output terminals are essentially noise-free. One of the transistors, acting as a transconductance amplifier, does introduce some noise though this is minimized by the use of an inductor. A third transistor forms a current source for the current path to one of the output terminals. A differential output is achieved at the output terminals because the pair of transistors has complementary outputs. In another embodiment, a capacitor is connected across the collector and base electrodes of one of the transistors to introduce a further stage of gain.

Abstract: A programming or function-setting cell for a field programmable gate array utilizes ferroelectric capacitors connected to the nodes of a latch circuit to retain charge representing the state of the cell so that, following a power loss or a specific event upset, the programming information held by the latch circuit may be reinstated. The latch circuit comprises a pair of inverters having their inputs and outputs cross-coupled by way of respective switching transistors, and the capacitors are connected between the nodes and a common plate conductor normally held at a potential intermediate the supply potentials for the inverters.

Abstract: Active filter circuit 1 consists of five filter stages 70-74 cascoded between a voltage supply and ground potential. The circuit has two major current paths, the first through the collector-emitter paths at transistors 31, 33, 35, 37 and 39, the second through transistors 32, 34, 36, 38 and 40. Each major current path is driven by a current source 61, 62. In operation, a differential input signal is applied to the base electrodes of transistors 31, 32 and a differential output signal is taken from the emitters of transistors 39, 40. The transistors 33, 34 of stage 71 have their collector and base electrodes cross-coupled. Transistors 35-40 of stages 72-74 are connected in the same manner. In another embodiment (FIG. 3, not shown) a cut-off frequency is varied under control of controllable current sources.

Abstract: A ring oscillator includes a set of metal-oxide-semiconductor (MOS) complementary, inverting stages, wherein each stage includes a pair of cross-coupled CMOS NAND or NOR gates. The first and last stages are also cross-coupled, such that positive and negative output signals of the last stage are connected respectively to negative and positive input signals of the first stage.

Abstract: An improved analog hearing aid is provided which incorporates a current source transconductance amplifier as an input stage. The gain defining bias current of the input stage transconductance amplifier is adjusted upon the application of battery power to the hearing aid to define a low input signal gain, and is then reduced by two gain regulators to define a compression threshold and compression ratio, and to provide a maximum output ceiling. Also provided is a method of trimming the low signal gain of the hearing aid at the time battery power is applied.

Abstract: An improved hearing aid amplifier circuit employs a Class D amplifier which includes an output to input feedback loop to minimize distortion, stabilize gain, and simplify the design requirements for several circuit elements of the Class D amplifier.

Abstract: A system and method includes an encoder and noise predictive Viterbi detector tuned such that error events with small values of the unique distance metrics are eliminated so that the error rate is enhanced. The system includes an encoder, a modulator, a PR channel and a detector. An input signal is input to the encoder. The encoder preferably encodes the input string with an even weight code to generate a code string thereby providing high code rates that are easy to implement. The output of the encoder is coupled to the input of the PR channel. The PR channel preferably comprises a filter and a noise source coupled to form a channel, a sampler, a low pass filter and an equalizer. The output of the channel is input to the low pass filter. The output of the low pass filter is coupled by the sampler to the input of the equalizer. Finally, the output of the equalizer is coupled to the input of the detector.

Abstract: A system comprises an encoder, a precoder, a PR channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies such encoding such that the code string after being modified by the precoder has a pre-selected parity structure. The encoder provides a systematic encoding scheme in which many of the encoded bits are the same as the input bits used to generate the encoded bits. This systematic approach of the present invention provides an encoder that is easy to implement because a majority of the bits are directly "feed through" and non-trivial logic circuits are only needed to generate the control bits. The systematic encoding also dictates a decoder that is likewise easy to construct and can be implemented in a circuit that simply discards the control bit.