Frequency selective logarithmic amplifier with intrinsic frequency demodulation capability
First Claim
1. A system for use in a receive chain of a communication device, the system comprising:
- an amplifying circuit configured to receive an input signal and to generate an oscillation based on the input signal;
one or more quadripole resonant circuits configured to establish a frequency pass band transfer response with a substantially zero phase region, the one or more quadripole resonant circuits comprising a parallel resonant circuit and a series resonant circuit forming a four terminal network, the one or more quadripole resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation of the system;
a sampling circuit coupled to the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes, wherein an instantaneous frequency of the voltage spikes carries frequency modulation (FM) and amplitude modulation (AM) modulation information of the input signal and is output as a first output signal, and wherein the first output signal has a different frequency than the input signal;
a first low pass filter circuit coupled between the amplifier circuit and the sampling circuit to isolate the first output signal from the input signal and the oscillation generated by the amplifier; and
a second low pass filter circuit coupled to the one or more quadripole resonant circuits, the second low pass filter circuit configured to generate a second output signal.
1 Assignment
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Accused Products
Abstract
A regenerative selective logarithmic detector amplifier (LDA) can have integrated FM demodulation capabilities. It can receive a wired or wireless FM modulated signal and amplify or demodulate it with high sensitivity, high skirt ratio and minimized noise when compared to the prior art. When used in conjunction with other circuits such as a PLL or mixer, it can improve interference rejection and frequency selectivity and be locked on a precise channel in frequency and phase. The LDA produces intermittent oscillations that are self-quenched when reaching a given threshold. It also embeds the circuitry to perform direct FM discrimination. FM demodulation process is completed by a simple analog or digital frequency to voltage converter. This plus the fact that the instantaneous regeneration gain is low-medium permit to detect signals of small amplitudes buried in the noise.
131 Citations
41 Claims
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1. A system for use in a receive chain of a communication device, the system comprising:
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an amplifying circuit configured to receive an input signal and to generate an oscillation based on the input signal; one or more quadripole resonant circuits configured to establish a frequency pass band transfer response with a substantially zero phase region, the one or more quadripole resonant circuits comprising a parallel resonant circuit and a series resonant circuit forming a four terminal network, the one or more quadripole resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation of the system; a sampling circuit coupled to the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes, wherein an instantaneous frequency of the voltage spikes carries frequency modulation (FM) and amplitude modulation (AM) modulation information of the input signal and is output as a first output signal, and wherein the first output signal has a different frequency than the input signal; a first low pass filter circuit coupled between the amplifier circuit and the sampling circuit to isolate the first output signal from the input signal and the oscillation generated by the amplifier; and a second low pass filter circuit coupled to the one or more quadripole resonant circuits, the second low pass filter circuit configured to generate a second output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A system for use in a receive chain of a communication device, the system comprising:
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an amplifying circuit configured to receive an input signal and to generate an oscillation based on the input signal; one or more quadripole resonant circuits configured to establish a frequency pass band transfer response with a substantially zero phase region, the one or more quadripole resonant circuits comprising a parallel resonant circuit and a series resonant circuit forming a four terminal network, the one or more quadripole resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation of the system; a sampling circuit coupled to the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes, where an instantaneous frequency of the voltage spikes carries FM and AM modulation information of the input signal and is output as a first output signal, wherein the first output signal has a different frequency than the input signal; a first low pass filter circuit coupled between the amplifier circuit and the sampling circuit to isolate the first output signal from the input signal and the oscillation generated by the amplifier; a matching circuit configured to receive at least one of the input signal or the output signal and to improve matching and coupling of one or more of the input signal or the output signal; an isolation circuit between the input signal and the matching circuit, the isolation circuit configured to reduce leakage of backward energy; and a second low pass filter circuit coupled to the one or more quadripole resonant circuits, the second low pass filter circuit configured to generate a second output signal. - View Dependent Claims (25, 26)
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27. A logarithmic detector amplifier for use in a receive chain of a communication device, the logarithmic detector amplifier comprising:
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an FM receiver configured to receive an FM input signal; an amplifier configured to receive an input signal and to generate an oscillation based on the FM input signal; at least one quadripole coupled to the amplifier, the at least one quadripole having a parallel resonance circuit and a series resonance circuit, the one or more quadripole resonant circuits comprising a parallel resonant circuit and a series resonant circuit forming a four terminal network, the at least one quadripole configured as a bandpass filter to filter the FM input signal and to cause the amplifier to resonate at a target frequency; a sampling circuit coupled to the amplifier and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes, wherein an instantaneous frequency of the voltage spikes carries FM modulation information of the FM input signal and is output as a first FM output signal; and a low pass filter circuit coupled to the one or more quadripole resonant circuits and configured to generate a second output signal, wherein the target frequency is variable and based on at least one parameter of the logarithmic detector amplifier. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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Specification