Maxim Integrated Products, Inc.

Tektronix, Inc.

James W Marsh

Martin Tomasz

Brent R Jensen

Matthew Glenn Waight

Keith H Lofstrom

Scott Lindsey Williams

Howard Luong

A method and apparatus for an electronically tuned agile integrated bandpass filter is described. In one embodiment, the invention is an intermediate frequency filter for use in an integrated circuit. The filter includes a first filter stage, including a first LC resonator. The first filter stage further includes a first adjustable capacitor array coupled to the first LC resonator. The first adjustable capacitor array has an effective capacitance value adjustable through use of a first plurality of programmable data storage locations. The first plurality of programmable data storage locations are programmable through a serial control interface.

Electronically tuned agile integrated bandpass filter

A converter for the direct down-conversion of direct broadcast satellite signals such as those used for digital television. The direct broadcast satellite signal received from the satellite dish is amplified and then downshifted within the Low Noise Block (LNB), a subsystem contained with the satellite dish assembly, to a predetermined frequency band, typically in the L-band in the range 950 MHz to 2150 MHz. The signal is then sent via a coaxial cable to the set-top box unit located indoors, and there directly converted from the received frequency to baseband, in the preferred embodiment by a single integrated circuit, which may include on chip active filters for further integration and for rejection of adjacent channels and anti-aliasing of analog to digital converters. Use of a wide range variable gain amplifier, generation of closely controlled inphase and quadrature components of the down-converting mixers and offset compensation provides baseband inphase and quadrature components of sufficient quality for data recovery using conventional techniques.

Direct-conversion tuner integrated circuit for direct broadcast

A variable gain amplifier having improved bandwidth and linearity, and having improved dynamic range by allowing the amplifier to be designed for low noise performance, while retaining the linearity normally lost with low noise designs. The amplifier is of the current steering type, having a differential current steering input stage coupled to a further current steering stage for controlling the gain responsive to a gain control signal. Current is maintained in a pair of common base connected transistors in the output circuit so that these transistors do not create excessive noise or limit the bandwidth and linearity of the amplifier at low gain. Maintaining the current in these transistors responsive to the gain control signal may maintain a substantially constant current in these transistors independent of gain. Exemplary embodiments are disclosed.

Variable gain amplifier with improved linearity and bandwidth

A method for obtaining a rectified signal from a first alternating current signal. The method includes the step of inputting the first alternating current signal into a variable gain amplifier to obtain a second alternating current signal. The second alternating current signal has a substantially constant peak-to-peak voltage irrespective of a power level of the first alternating current signal. The method further includes the step of rectifying the second alternating current signal, using a power detector circuit, to obtain the rectified signal, whereby a direct current level of the rectified signal is substantially proportional to the power level of the first alternating current irrespective of the power level of the first alternating current. The rectified signal may then be employed in, for example, a feedback control circuit to control the amount of power output by an RF signal source.

Methods and apparatus for signal amplitude control systems

An improvement is provided for current sources of the type having three transistors configured as follows: The bases of the first (Q1) and second (Q2) transistors are tied together. The collector of the first transistor (Q1) is coupled to a first voltage (V.sub.CC,V.sub.EE) via a first resistor (R1). The emitter of the first transistor (Q1) is coupled to a second voltage (V.sub.EE,V.sub.CC) via a second resistor (R2). The collector of the second transistor (Q2) produces the output current (I.sub.OUT). The emitter of the second transistor (Q2) is coupled to the second voltage (V.sub.EE,V.sub.CC) via a third resistor (R3). The base of the third transistor (Q3) is coupled, either directly or indirectly through a fourth transistor (Q4), to the collector of the first transistor (Q1). The collector of the third transistor (Q3) is connected to the first voltage (V.sub.CC,V.sub.EE) and the emitter of that transistor (Q3) is connected to the bases of the first (Q1) and second (Q2) transistors. The improvement consists of a fourth resistor (R5) coupled between the base and the emitter of the first transistor (Q1), the fourth transistor preferably having a value that is one half of the value of the first resistor (R1) when no fourth transistor (Q4) is present and having a value that is equal to the value of the first resistor (R1) when a fourth transistor (Q4) is in the base path of the third transistor (Q3).

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Sherwood, OR, United States of America

James W Marsh