Motorola Corporation

Freescale Semiconductor,inc.

Anthony D Newton

David T Jobling

Geoffrey W Perkins

Anil Gercekci

Robert Smith

Hans Staufer

Heinz Lehning

Thien Luong Huynh

The invention relates to an adaptive Radio Frequency (RF) filter (), which is particularly useful as an RF filter in Wireless Local Area Networks (WLAN's). As greater demands are placed on RF systems, for example in WLAN's in order to increase channel capacity by utilizing available bandwidth, corresponding demands are placed upon performance and tolerance of components used in FR circuits. An adaptive Radio Frequency (RF) filter for filtering first and second RF signals from an OFDM encoded carrier signal is provided, the adaptive RF filter comprises: a low-pass filter () configured to filter first and second RF signals, one from another, so as to provide a first RF output signal; the adaptive RF filter being tunable in response to one or more input signals, the at least one input signal being derived from a comparator (), which compares the first RF output signal with a desired value for said first RF output signal, and provides a connection factor for varying a characteristic of the filter (). An advantage of the invention is that it facilitates filter of two OFDM encoded RF signals, the first typically at 8.1 MHz and the second (unwanted) at 11.9 MHz, from a base-band signal, with a noise floor level of &#x2014;55 dB or better. Another advantage is that the filter is able to self calibrate and is able to take into account fluctuations which may affect performance, for example thermal drift, and automatically trim its characteristics so as to compensate for these fluctuations.

Adaptive radio frequency (RF) filter

The invention relates to gain calibration in a transceiver unit () having a transmitter unit and a receiver unit and a feed back coupling () between these. A signal level measurement unit () measures signal levels of a feedback signal through either the receiver unit or through a signal level detector (). A reference signal level of the feedback signal is set by adjusting the transmitter until the signal level measurement unit () measures a predefined value when connected through the signal level detector (). An absolute value of the transmitter gain is then calibrated. The signal level measurement unit () is connected through the receiver unit and the absolute gain of the receiver is calibrated. A gain is changed either in the receiver or the transmitter unit. The relative signal level change of the feedback signal is measured and used to calibrate the gain step.

Transmitter and receiver gain calibration by means of feedback in a transceiver

A synchronous demodulator ( ) drives an output antenna ( ) with a push-pull driver circuit ( ). The push-pull driver circuit ( ) includes two transistors connected in a push-pull configuration driving a center-tapped transformer ( ). The transformer ( ) couples the push-pull driver circuit ( ) to an antenna ( ). Received signals are demodulated in the output driver circuit ( ).

Synchronous demodulator

Bipolar differential amplifier

A timebase circuit for use in the vertical timebase of a television receiver in which a linearity control current fed to the ramp capacitor is derived by multiplying a current proportional to the difference between the instantaneous and average ramp voltages by a reference current which may be adjusted to control linearity.

Timebase circuit

CRT Control circuit

A timebase circuit is described, for compensation of picture dimensions of a television type display, for EHT fluctuations in which a control current is derived by multiplying a current dependent upon the picture beam current with a reference current derived from a digital to analogue converter fed with a digital code.

Frequency controlled oscillator utilizing an U/D counter in the feedback

A timebase circuit is described for providing a horizontal drive correction waveform to correct for pincushion distortion in which a parabolic correction current is derived by squaring a current proportional to the difference between the instantaneous and average values of the vertical ramp voltage. The correction current may be tilted by combination with a linear current proportional to the ramp voltage and may also be amplitude controlled.

An apparatus and method for the automatic setup of a CRT operating point, or dc signal level (black), as well as the contrast, or gain level (gray), of a video display by sampling the CRT signal level of the individual cathodes and locking the dc signal level to a common dc setup reference and gain level to a value determined by a common contrast control signal and gain reference. An apparatus and method in which a common brightness control signal is modulated by a common contrast control signal such that a brightness control pedestal is added to each video signal path of a video display whereby picture black level does not change with contrast.

Video driver circuit and method for automatic gray scale adjustment and

A current mirror circuit arrangement wherein an output current is provided by an output transistor and coupled between the base electrode of the output transistor and a reference potential is a series combination of a resistor and a diode. Signals are fed to the base electrode of the output transistor from a voltage supply via an emitter follower circuit and a resistor is connected across the diode so as to share current with the diode to increase its impedance at low current values and consequently to improve the overall linearity of the output current input voltage characteristic.

Current mirror circuit arrangement

A TV timebase circuit includes a vertical sync counter in the form of a ten-bit ripple-through counter. Additional logic circuitry including a pair of divide-by-four counters, a latch, a D flip-flop, and associated AND, NAND, and invertor gates are also provided. The circuit is responsive to a multiple of the horizontal frequency and to vertical sync pulses and is capable of automatic recognition of 525 or 625 line standard. The logic includes a mechanism for locking out the vertical counter's 525 count when operating in the 625 mode. The latch, in association with one of the divide-by-four counters serves a 'fly wheel' sync function, whereby a predetermined number of 'matches' must be recognized to lock the circuit into a given mode, and whereby a predetermined number of 'mis-matches' must occur to drop the circuit operation from the locked-in mode. Several outputs are taken off the vertical counter to operate ramp drive and blanking functions of the TV vertical sweep generator. An output representative of the particular line standard being decoded may be used to provide chrominance decoding information and picture height control information. An alternative embodiment capable of recognizing any given TV line standard comprises a register which is loadable with the line standard number, which in turn is provided from the vertical counter cumulative count between successive vertical sync pulses, the vertical counter being reset by each vertical sync pulse. Comparison logic is provided for locking the counter circuit onto a given line standard after a predetermined number of successful matches have occurred between the contents of the register and the vertical counter count at the moment of reset by the vertical sync pulse.

Vertical sync counter with automatic recognition of TV line standard

A phase detector circuit has low offsets and is easily made as a bipolar integrated circuit. A first input to the phase detector controls a transistor which in turn controls a current source. The output of the current source is connected to a current mirror which has an NPN transistor. The current mirror is connected to ground by a transistor which is controlled by a second input signal. When the first input signal is present and is out of phase with the second input signal the output of the phase detector flows from the current source through the collector base junction of the NPN transistor. When both input signals are in phase the output of the phase detector serves as a current sink whose current carrying capabilities is controlled by the output of the current source.

Growing community of inventors

Le Vaud, Switzerland

Anthony D Newton