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Felix Hoffmann, a German chemist, was searching for something to relieve his father's arthritis. In doing so, he "rediscovered" acetylsalicylic acid and in 1900, patented a stable process for developing it. Hence, we have aspirin.
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| Number | Title | Issue Date |
| 5225795 | Digital quadrature modulator A digital quadrature modulator having a first storage device for receiving an I phase component of a digital baseband signal and digital carrier phase information as a higher order address and a lower order address, respectively, and a second storage devi... | 07/06/1993 |
| 4992743 | Dual-tone direct digital synthesizer Arrangements are provided for generation of dual-tone waveforms utilizing direct digital waveform synthesis techniques and architecture and retaining the advantageous characteristics of direct digital waveform synthesis. Preferred embodiments feature comb... | 02/12/1991 |
| 4982170 | Signal processing apparatus This invention discloses a signal processing apparatus which has N nonlinear oscillators, a circuit for coupling the N nonlinear oscillators in a loop-like form, a circuit for shifting the phase of the output signal of a particular nonlinear oscillator fr... | 01/01/1991 |
| 4939387 | Impulse waveform drive apparatus for surface acoustic wave chirp system An amplitude modulation apparatus for achieving an extremely deep extinction ratio (in excess of -90 dBc) at nanosecond rise times required by an SAW device comprises the cascaded combination of a controlled switching device (GaAsFET), capable of providin... | 07/03/1990 |
| 4871987 | FSK or am modulator with digital waveform shaping A binary signal modulator includes a sampling circuit for sampling a binary signal at a predetermined sampling frequency, a modulating circuit responsive to the sampled binary signal for generating a modulating signal, the rising and decaying timings of w... | 10/03/1989 |
| 4804931 | Digital amplitude modulator - transmitter A digital amplitude modulator for use in transmitting information signals in the context of AM audio and AM video. The amplitude modulator/transmitter basically consists of a predetermined number of quadrature hybrid power devices configured as combiners ... | 02/14/1989 |
| 4746880 | Number controlled modulated oscillator Disclosed is a number controlled, modulated, oscillator employing a modulation selector for receiving a digital number for use for frequency modulation or for phase modulation, a tuning network for receiving another digital number in a variety of forms, a... | 05/24/1988 |
| 4717894 | Calibration of vector modulators using a scalar detector Calibration of a vector modulator is done using a scalar detector to measure the amplitude of the RF output signal, phase shifters to adjust the relative phases of the I and Q components of the RF carrier, and variable attenuators in the I and Q modulatio... | 01/05/1988 |
| 4602226 | Apparatus for the gated modulation of a radio-frequency carrier signal Apparatus for the gated modulation of an RF carrier signal uses a balanced circuit for amplitude-modulating the carrier signal, and a circuit having a predetermined minimum on-off amplitude-ratio for providing respective very high attenuation and very low... | 07/22/1986 |
| 4540957 | Amplitude modulator forms two phase-shifted pulse trains and combines them A system and method for amplitude modulating a carrier signal with an audio or other information input signal relies on multivibrators and comparators initiating a logic controlled processing technique for providing two sinusoids, each a fundamental frequ... | 09/10/1985 |
| 4509208 | Frequency conversion unit A frequency conversion unit comprising a local oscillator, first and second mixers, first and second hybrid circuits. The mixers receive, via the first hybrid circuit, local oscillation outputs from the local oscillator, and the second hybrid circuit rece... | 04/02/1985 |
| 4499339 | Amplitude modulation apparatus and method An apparatus and a method modulate a carrier signal so that the resultant modulated signal varies between a value substantially equal to the quiescent level of the carrier signal and peak values up to several hundred percent of the quiescent level of the ... | 02/12/1985 |
| 4442407 | Two loop automatic level control for power amplifier The power supply potential applied to the final stage of an RF amplifier is odulated by means of an adaptive power supply. The power supply potential applied to the final RF amplifier is controlled by a first control loop in accordance with an error signal... | 04/10/1984 |
| 4331941 | Digital phase domain amplitude modulation method and apparatus A modulating signal is applied to an analog-to-digital converter which addresses a read-only memory phase look-up table. The read-only memory phase look-up table output is applied to a polarity generator. The polarity generator output and output from a ph... | 05/25/1982 |
| 4321563 | Circuit for stabilizing frequency of FET oscillator as output power varies A frequency stabilizing device for a FET high-frequency oscillator comprises means for coupling an automatic biasing circuit included in the source-ground connection of the oscillator to a drain voltage supply circuit included in the drain-ground connecti... | 03/23/1982 |
| 4320361 | Amplitude and frequency modulators using a switchable component controlled by data signals A modulated signal source derives its modulation information from digital data held in a data store. The digital data is arranged to operate a switch which in the case of amplitude modulation produces pulses of carrier frequency and in the case of frequen... | 03/16/1982 |
| 4295105 | Switched-capacitor modulator Novel apparatus and techniques for the modulation of a signal from one frequency band to another frequency band are disclosed. An integrator is changed between the inverting and non inverting modes, each mode occurring with each half cycle of a carrier si... | 10/13/1981 |
| 4077021 | Method and arrangement for coding binary signals and modulating a carrier signal A method and structure for converting a sequence of binary digits into a sequence of discrete signal values, e.g., phase values, of a modulated carrier signal for data transmission. By introducing additional redundant signal values and coding information ... | 02/28/1978 |
| 4063199 | Radio frequency pulse width amplitude modulation system Amplitude modulation of a radio frequency carrier is achieved by generating a rectangular wave pulse train at the carrier frequency, the pulses of which vary in width as a function of the amplitude of the audio input signal. The audio frequency input wave... | 12/13/1977 |
| 3939303 | Digital video modulation apparatus A modulator for producing a digital sub-carrier amplitude modulated by a video or other modulating signal comprises sampling means for sampling the modulating signal at twice the process carrier frequency, and selector means for feeding the samples to an ... | 02/17/1976 |
