Logarithmic Detector Amplifier System for Use as High Sensitivity Selective Receiver Without Frequency Conversion

Abstract

A logarithmic detector amplifying (LDA) system is provided for use as a high sensitivity receive booster or replacement for a low noise amplifier in a receive chain of a communication device. The LDA system includes an amplifying circuit configured to receive an input signal having a first frequency and generate an oscillation based on the input signal, a sampling circuit coupled to the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold to periodically clamp and restart the oscillation to generate a series of pulses modulated by the oscillation and by the input signal, and one or more resonant circuits coupled with the amplifying circuit and configured to establish a frequency of operation and to generate an output signal having a second frequency, the second frequency being substantially the same as the first frequency.

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 at an input of the system having a first frequency and to generate an oscillation based on the input signal;   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; and   one or more resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation of the system and to generate an output signal at an output of the system having a second frequency, the second frequency being substantially the same as the first frequency.   
     
     
         2 . The system of  claim 1 , wherein:
 at least one of the one or more resonant circuits is coupled in series with the amplifying circuit at an input side or an output side of the amplifying circuit.   
     
     
         3 . The system of  claim 1 , wherein:
 at least one of the one or more resonant circuits is coupled in shunt with the amplifying circuit at an input side or an output side of the amplifying circuit.   
     
     
         4 . The system of  claim 1 , wherein:
 at least one of the one or more resonant circuits is coupled in parallel with the amplifying circuit.   
     
     
         5 . The system of  claim 1 , wherein:
 the one or more resonant circuits include an inductor and two capacitors coupled in parallel and a third capacitor coupled to a common node between the two capacitors, wherein values of the inductor and the capacitors are configured to output the signal having the RF frequencies.   
     
     
         6 . The system of  claim 1 , wherein:
 the one or more resonant circuits comprise a plurality of components, one or more of which are configured to be of high Q.   
     
     
         7 . The system of  claim 6 , wherein:
 the one or more components include one or more of a SAW filter, a BAW filter, a crystal filter, a ceramic filter, a mechanical filter, an LC resonator, an active RC, a variation of RC or LC where C is replaced with a variable capacitor, or an active component with variable capacitance.   
     
     
         8 . The system of  claim 1 , further comprising:
 an isolation circuit coupled to an input side, an output side or both the input side and the output side of the amplifying circuit to filter out leaks, reflections and other interference effects from other circuits.   
     
     
         9 . The system of  claim 8 , wherein:
 the isolation circuit comprises a low noise amplifier.   
     
     
         10 . The system of  claim 1 , further comprising:
 a matching network coupled to an input side, an output side or both the input side and the output side of the amplifying circuit for impedance matching.   
     
     
         11 . The system of  claim 1 , further comprising:
 a matching network coupled to an input side, an output side or both the input side and the output side of the amplifying circuit for phase correction.   
     
     
         12 . The system of  claim 1 , further comprising:
 a critically-coupled coupling circuit coupled to an input side of the amplifying circuit.   
     
     
         13 . The system of  claim 1 , wherein:
 the one or more resonant circuits include a critically-coupled coupling circuit coupled to the output of the system.   
     
     
         14 . The system of  claim 1 , wherein:
 the system is configured to replace a low noise amplifier in the receive chain of the communication device.   
     
     
         15 . The system of  claim 1 , wherein:
 the system is configured to complement a low noise amplifier in the receive chain of the communication device, and to be placed before or after the low noise amplifier.   
     
     
         16 . The system of  claim 1 , further comprising:
 a phase lock loop having an output split into a first output and a second output, the second output being adapted to a voltage range frequency divider feeding frequency/phase comparator, wherein the comparator is configured to receive a second input signal F_reference frequency divided by a factor M, wherein the comparator output driving a low pass filter through a switch, wherein the switch is enabled by a digitally shaped signal of a second output of the system, and wherein the low pass is driving an additional input of the system.   
     
     
         17 . A system for use as a complement of a low noise amplifier and configured to be placed before or after the low noise amplifier in a receive chain of a communication device, the system comprising:
 an amplifying circuit configured to receive an input signal at an input of the system having a first frequency and to generate an oscillation based on the input signal;   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; and   one or more resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation of the system and to generate an output signal at an output of the system having a second frequency, the second frequency being substantially the same as the first frequency.   
     
     
         18 . The system of  claim 17 , further comprising:
 a phase lock loop having an output split into a first output and a second output, the second output being adapted as an input to a voltage range frequency divider feeding frequency/phase comparator, wherein the comparator is configured to receive a second input signal F_reference frequency divided by a factor M, wherein the comparator output driving a low pass filter through a switch, wherein the switch is enabled by a digitally shaped signal of a second output of the system, and wherein the low pass is driving an additional input of the system.   
     
     
         19 . The system of  claim 18 , where the output of the phase lock loop is split by one or more of a Wilkinson splitter, a resistive splitter, a Wilkinson splitter implemented with a hybrid microstrip or metamaterial, a lumped elements splitter with a combination of R-L-C components, a coupler, a symmetrical splitting device, an unsymmetrical splitting device, or a digital frequency divider wherein a first output is a Q output and a second output is an inverter Q_bar output. 
     
     
         20 . A method for improving receive sensitivity in a receive chain of a communication device, the method comprising:
 amplifying a receive input signal and generating an oscillation based on the input signal;   sampling the amplified signal and terminating the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes; and   including one or more resonant circuits coupled to the amplifying circuit and configured to establish a frequency of operation and output a signal having RF frequencies.   
     
     
         21 . A system for use in a receive chain of a communication device, the system comprising:
 an amplifying circuit with low instantaneous regenerative gain configured to receive an input signal at an input of the system having a first frequency and generate an oscillation based on the input signal;   an integrated sampling circuit coupled to the amplifying circuit and configured to self-terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes; and   a resonant circuit coupled at an output of the amplifying circuit, the resonant circuit having at least one sub resonator with a high Q factor, having at least one sub resonator coupled in parallel, and configured to establish a frequency of operation of the system and to generate an output signal at an output of the system having a second frequency, the second frequency being substantially the same as the first frequency.