Abstract: An amplifier typically exemplified by a TIA is realized that provides an optimal band characteristic, that reduces the possibility of the oscillation, and that achieves a reduced dispersion of the band characteristics. An amplifier for amplifying an electric signal, comprising: a first buffer for amplifying the electric signal; a filter that is connected to an output of the first buffer and that includes a parallel circuit consisting of an inductor and a first capacity; and a second buffer connected to an output of the filter.

Abstract: Certain aspects of a method and system for RC-CR quadrature generation with wideband coverage and process compensation may include determining an amplitude mismatch between an in-phase (I) component and a quadrature (Q) component of a signal generated in a radio frequency (RF) transmitter or receiver. A variation in resistance of a quadrature network associated with the I component and Q component may be determined. The determined amplitude mismatch and the determined variation in the resistance of the quadrature network may be compensated by adjusting a resistance of a portion of the quadrature network associated with the I component and a resistance of a portion of the quadrature network associated with the Q component.

Abstract: A modulator circuit (28) for directing a voltage across a modulator element (26) to modulate a beam (20) includes a first inductor L1 that is electrically connected in parallel to the modulator element (26) and a second inductor L2 that is electrically connected in parallel to the first inductor L1 and the modulator element (26). A resonant frequency of the modulator circuit (28) is controllable over a range of between approximately 200 and 380 MHz. Additionally, the modulator circuit (28) can include a third inductor L3 that is electrically connected in parallel to the inductors L1, L2, and the modulator element (26). Further, the modulator circuit (28) can include an added capacitor (546) that is electrically connected in parallel to the inductors L1, L2, and the modulator element (26).

Abstract: A digital radio device having a quadrature demodulator that does not suffer from substantial amplitude roll-off at the relevant operating range. Such a device is obtained by a phase shifting network in a quadrature branch of the demodulator having a series arrangement of a resistor and an capacitor coupled to an inductor coupled to ground. A junction between the series arrangement and the inductor forms the output of the quadrature branch. Alternative embodiments are provided. The demodulator avoids asymmetric digital signal distortion which can have deteriorating effects, in particular to GFSK-signals or &pgr;/4-DQPSK signals, or the like, and further noise shift of data which is of particular importance in low [S/N]-systems such as paging systems.

Abstract: A frequency modulated signal demodulator circuit includes a phase shift element and a time delay element which operate on an input signal (V_IF). The phase shift element and the time delay element are provided by a gyrator component (14, 16, 20).

Abstract: An FM demodulation circuit includes a phase conversion circuit which converts a frequency variation of an input signal into a phase variation and has a variable conversion characteristic, and a control current source circuit which outputs, when the level of the input signal drops lower than a predetermined level, control current to vary the conversion characteristic of the phase conversion circuit so that the demodulation sensitivity may be raised.

Abstract: A high-performance voltage controlled oscillator without use of variable capacitance (varicap) diodes which is easy in fabrication in an semiconductor IC form. The voltage controlled oscillator includes:a differential amplifier having a differential pair of transistors (Q.sub.1, Q.sub.2); an LC resonance circuit having a coil (L.sub.0) and a capacitor (C.sub.0); a phase shift circuit for receiving a differential output of the differential amplifier via a buffer of transistors (Q.sub.3, Q.sub.4) and for providing its output for the differential amplifier in a positive feedback mode; and a current control circuit for variably controlling an operating current (Ie) of the phase shift circuit according to a controlled voltage applied from a circuit other than those in the voltage controlled oscillator.

Abstract: A demodulator circuit includes a gyrator circuit forming a derived equivalent inductance which is used in a demodulating circuit. The gyrator circuit has a first operational transconductance amplifier and a second operational transconductance amplifier, wherein a second input terminal of the first operational transconductance amplifier is connected to a first output terminal of the second operational transconductance amplifier. A second output terminal of the first operational transconductance amplifier is connected to a second input terminal of the second operational transconductance amplifier. Both of the second input terminal of the first operational transconductance amplifier and the second input terminal of the second operational transconductance amplifier are grounded via a constant dc voltage. A first output terminal of the first operational transconductance amplifier is connected to a first input terminal of the second operational transconductance amplifier.

Abstract: In a quadrature FM detector, demodulation is performed by a product detector which multiplies an amplitude limited FM modulated information signal by a version of the amplitude limited FM modulated information signal which has been phase shifted by a phase shifting network including a single tuned LC circuit. In order to assure that the LC circuit is tuned to the carrier frequency of the FM signal, the LC circuit is tuned by a variable impedance device in response to a control signal generated by a bus controlled DAC. The control signal is coupled to the variable impedance device at the same pin of an integrated circuit where the LC circuit is coupled to the demodulator.

Abstract: An FM demodulator having two input terminals (11, 12), to which FM input signals having 90.degree. phase relation are applied, the said FM demodulator including a phase comparator (1) and a tunable, phase shifting circuit (2), the phase shifting circuit (2) being tuned by the FM demodulator output signal via a feedback path comprising a loop, filter. By adding a compensation filter (5) to the tuning control loop the phase shifting circuit is effectively cancelled from the tuning control loop, thereby making the tuning control loop independent of the bandwidth of the phase shifting circuit (2). Thus the bandwidth of the phase shifting circuit (2) can be reduced for threshold extension.

Abstract: A demodulator for demodulating a binary frequency-modulated signal includes a demodulator with a quadrature tank circuit and a duty cycle monitor circuit. The quadrature tank circuit has a voltage-controllable resonant frequency for compensating for shifts in the carrier frequency of the incoming signal and shifts in the tank circuit component values so as to allow the use of a high-Q tank circuit and thereby maximize use of the incoming signal energy. The quadrature tank circuit is a reactive circuit (with both inductive and capacitive elements) which includes a varactor diode having a voltage-controllable capacitance. The duty cycle monitor circuit measures the duty cycle of the demodulated binary output from the demodulator, and provides a control voltage to the quadrature tank circuit for adjusting its center frequency of operation.

Abstract: A frequency demodulation circuit having an improved detection sensitivity is provided by forming an all-pass equalizer in a Quadrature-type demodulator capable of allowing a band covering at least a carrier frequency deviation to pass therethrough. The equalizer comprises a band-pass filter for detecting the frequency deviation of an inputted FM carrier signal, a gain-doubling amplifier and a substractor for performing subtraction between the signal inputted to the band-pass filter and the output of the amplifier. The operation of the circuit is such that a FM carrier signal is supplied to the band-pass filter through a phase shifter and to a phase comparator and the output of the substractor and the FM carrier signal are compared to each other by the phase comparator to thereby obtain a FM demodulated signal.

Abstract: An apparatus and method for demodulating and remodulating a transmitted signal prior to presentation to a television receiver, the transmitted signal comprising a video signal, a first channel signal, and a second channel signal, wherein one of the two channel signals is selected, demodulated and remodulated with the video signal prior to presentation to the television receiver. The apparatus allows the viewer of a television receiver which accepts a single channel signal to select between one of two alternate channel signals associated with a video broadcast without the need to modify the television receiver. The apparatus is particularly well suited for television broadcasts using a dual carrier transmission format. A novel varactor diode tuning means is used in one embodiment for changing the center frequency of a frequency modulation demodulator. The disclosed apparatus also transparently allows stereo demodulation for television receivers which are capable of such stereo demodulation.

Abstract: A dual mode quadrature detector (15) uses the same components for both narrow band and wide band operation and provides an output amplitude which is independent of the mode of operation selected. A multiplier (32) provides a demodulated output signal (16) which is responsive to the phase difference between a signal (14) at one input (32A) and a phase shifted version of the signal at the other input (32B). A capacitor (30) and a phase shifting circuit (31) provide the phase shifted version of the signal. The phase shifting circuit (31) is responsive to a mode control signal (24) for determining the phase shift which is provided. The phase shift at the maximum frequency deviation of the narrow band signal is the same as the phase shaft at the maximum deviation of the wide band signal so that the output amplitude from the detector (15) is the same for both narrow band and wide band operation. The phase shift provided is controlled by varying the quality factor (Q) of the phase shifting circuit (31).

Abstract: FM quadrature demodulator having in-phase and quadrature terminals for applying a pair of FM-modulated signals in a mutual phase quadrature thereto, having a modulation signal which is frequency-modulated on a carrier, one of the two terminals being coupled to a first input of a first phase comparison circuit and the other terminal being coupled to a second input of the first phase comparison circuit via a first phase-shifting circuit which realizes a phase shift varying with said modulation signal, the first phase comparison circuit being connected to an output of the FM quadrature demodulator via a low-pass filter.

Abstract: A frequency-shift keying (FSK) signal detector splits an FSK signal into two paths. In one path, a phase-altering circuit having a variable frequency characteristic between the two encoding frequencies of the FSK signal provides either a phase lead or a phase lag depending upon the instantaneous frequency of the FSK signal. The phase-altered signal is sampled in response to the signal in the second path to decode a digital signal.

Abstract: A quadrature detector FM demodulates an intercarrier signal operating at an unknown frequency. An LC tank circuit develops a 90.degree. phase shift across inputs of a multiplier. The output signal of the multiplier is amplified and fedback to control a reactance stage and adjust the reactive load at an input of the multiplier so as to maintain a predetermined phase relationship independent of the frequency of the intercarrier signal. A phase compensation stage removes any real component at the inputs of the multiplier also in response to the feedback signal.

Abstract: An FM demodulator which generates a modulated object signal directly in digital form, wherein an input FM signal is phase detected, then converted to digital form, then quantized into a pulse density modulated binary signal using a clock reference signal having a frequency which is not correlated to the frequency of the input FM signal, and then the signal is filtered at the clock reference signal and outputted as the digital word output. Advantageously, by using the non-correlated clock reference signal, the signal to noise ratio is improved by a substantial factor.

Abstract: An angle modulation detector which prevents a demodulated output from being influenced by fluctuations in the amplitudes of signals generated from angle-modulated signal sources such as a phase-modulated signal and a frequency-modulated signal, even if the amplitude of a driving voltage applied to a connection between the bases of a pair of transistors constituting a phase detecting device is made larger in order to enhance the demodulation sensitivity and reduce noise produced during demodulation.

Abstract: A differential amplifier amplifies an FM signal supplied from an FM signal source. A phase shift circuit shifts a phase of a carrier signal included in an FM signal output from the differential amplifier. A multiplier circuit multiplies an FM signal supplied from the differential amplifier to a first balance input terminal and an FM signal supplied from the phase shift circuit to a second balance input terminal and then outputs a demodulation signal. A resistor serving as a supply means supplies an FM signal, whose carrier signal has a phase opposite to that of a carrier signal of an FM signal supplied from the differential amplifier to an output terminal of the phase shift circuit. The phase characteristics of the phase shift circuit is equivalently controlled and the phase of the FM signal supplied to the multiplier circuit controlled, thereby preventing a demodulation output from being distorted.

Abstract: An improved multilevel FSK demodulator, according to the invention, is provided that down-converts the IF frequency back to baseband quadrature via dual mixers. The improved multilevel FSK demodulator uses controllable time-delay in the demodulation process. This method requires a 90.degree. phase difference between 2 modulated signals to produce a maximum demodulated output amplitude at the maximum frequency deviation. Since the IF frequencies have been down-converted back to baseband quadrature, these 2 signals are only "out of phase" by an amount .DELTA.t that is equal to 90.degree./d.omega.. A further aspect of this invention addresses minimizing the DC offset from the demodulator by providing a feedback signal which controls the amount of delay provided to one of the quadrature signals.

Abstract: The invention improves the ability of the FS demodulator-circuit of an FS digital transmission system so as to withstand noise with low error count. The invention uses two different types of all pass networks and a phase measuring circuit to average random noise and enhance the desired FS frequencies.

Abstract: An FM detection circuit utilizes a first multiplier and phase shift circuit to demodulate an FM signal. The output signal also contains harmonic distortion as a result of the demodulation process. A gain control circuit is included to provide a first gain control signal to the first multiplier which adjusts the magnitude of the output signal of the FM detection circuit in such a manner as to substantially eliminate the harmonic distortion. The gain control circuit uses a second multiplier to generate an output signal proportional to the square of the output signal of the phase shift circuit which is then compared to a constant current to produce an error signal proportional to the harmonic distortion. The error signal controls the magnitude of the first gain control signal such that the output signal of the FM detection circuit is proportional to the deviation of the FM signal from its center frequency.