DESC:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)

A METHOD AND SYSTEM FOR DYNAMIC RANGE IMPROVEMENT IN DETECTOR LOG VIDEO AMPLIFIER

BHARAT ELECTRONICS LIMITED
WITH ADDRESS:
OUTER RING ROAD, NAGAVARA, BANGALORE 560045, KARNATAKA, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the invention

The present invention mainly relates to a detector log video amplifier and more particularly to system and method for dynamic range improvement in detector log video amplifier.

Background of the invention

A Detector Log Video Amplifier (DLVA) is well known in the art which is an amplifier that converts an RF signal with a large dynamic range into a video signal/voltage with a smaller dynamic range. The basic configuration of a DLVA is simply a detector diode (i.e. Schottky barrier diode or a zero bias tunnel diode, etc.) which converts the RF energy into a DC voltage which is then amplified by a log video amplifier with a logarithmic transfer function. The combination results in a device which compresses a large RF signal range into a narrow range of video voltage.
The detected video sections of a DLVA may be either AC coupled, DC coupled, or pseudo DC coupled. The DLVAs are often used in radar receivers, such as phased array radar, passive direction-finding radar, and channelized radar used to secure the airspace around airbases and detect unauthorized intrusions. Types of DLVAs are also used in common RF test and measurement equipment to enhance their dynamic range performance while maintaining high linearity and sensitivity. The fast response time and broadband capability of some DLVAs make them ideal for electronic warfare (EW), signal intelligence (SIGINT), instantaneous frequency measurement (IFM) receivers, and other applications that require a fast response and relatively flat frequency response compared to other RF detectors.
For example, in document, US4758793 discloses a “Detector Log Video Amplifier". A Detector Log Video Amplifier (DLVA) comprising of a first RF detector for detecting the power levels within a first range (e.g. -40 to -20dBm) and producing first video frequency signals having amplitude representative thereof, from which are produced output signals having amplitudes logarithmically proportional to such received signals. A second RF detector detects the power levels of received RF signals having power levels of received RF signals having power levels within a second range (e.g. -20dBm to +20dBm) and produces corresponding second video frequency signals having amplitudes representative thereof, from which are produced output signals having amplitudes logarithmically proportional to such received signals. A control signal is produced from the second video frequency signals, the control signal having a level in accordance with the power levels of received RF signals. Received RF signals having power levels equal to or exceeding a first RF level (e.g. 0dBm) are attenuated in accordance with the control signal levels and coupled to the first detector. A limiter is responsive to the power levels of received RF signals exceeding a second level (e.g. +5dBm) for limiting the power levels of such RF signals coupled to the attenuator in accordance with the power levels of such signals exceeding the second level. With such arrangement, the RF signals coupled to the first detector are prevented from exceeding the first level, thereby significantly reducing the DLVA’s recovery time, for example less than 500 nanoseconds.
Further in document, US 7317902 B2 discloses a “successive Log Video Pad Power Detector and Method". Further, this prior describes a power detector which samples the output signal from a communication device and produces a control signal proportional to the transmit power level, compromising a series of diode detectors where the sampled signal is divided between the diode detectors by an attenuator cascade.
Further, the non-patent literature titled "An L Band Temperature Compensated Ultra Low Power Successive Detection Logarithmic Amplifier”, describes temperature compensated L-Band GaAS MMIC successive detection logarithmic amplifier (SDLA) featuring ultra-low power consumption. Log linearity of ±2.5dB and a dynamic range of 60dB were achieved over a 100-degree temperature range. This device shows no sacrifice of performance over larger, labor intensive hybrid MIC approach.
Another non-patent literature titled "Ultra Broad Band Extended Dynamic Range MMIC DLVA”, describes Design, fabrication and experimental results of a 2 to 18 GHz high dynamic range MMIC DLVA featuring short recovery time are presented. This fast DLVA is a Successive Detection Logarithmic Amplifier. The microwave part consists of five 2-18 GHz GaAs MMIC stages: each stage is composed of MMIC amplifiers, active power divider. attenuator and Schottky detector. Detected outputs levels are video limited before summation to obtain a logarithmic video response over a 65-dB extended dynamic range. No use of logarithmic video amplifier ensures short recovery time less than 200 ns over the whole dynamic range.
Another non-patent literature titled "Detector Log Video Amplifier with 60dB Logging Range”, describes the This paper presents an extended range detector log video amplifier for the 2-18 GHz range usable in R WR and ESM receivers. Beside details of the logging and summing amplifier, experimental results of log linearity in the -50 dBm to +10 dBm input power range and response to short 50 ns pulses are given.
All the above-mentioned detector log video amplifiers are with an inadequate dynamic range, inadequate log linearity with the effects of baseline shift and poor recovery time associated with AC or DC coupled circuits. Further, the presently available amplifiers have poor radio Frequency gain flatness, poor log linearity, Low Rise time, unwanted peak overshoot, complex circuity and has poor recovery time over an extended dynamic range.
Therefore, there is a need in the art with a method and system for dynamic range improvement in detector log video amplifier and to solve the above-mentioned limitations.

Objectives of the present invention

The main objective of the present invention is to provide a Detector Log Video Amplifier with CW Immunity, improved dynamic range, improved log linearity, reduced peak overshoot, fast rise time by using unique circuit methodology.
Another objective of the present invention is that the module is realized with less complex circuitry and it is easy for production with minimal tuning.
Further objective of the present invention provides an improved and extended Dynamic Range.
Moreover, objective of the present invention provides a higher video output voltage without the effects of poor Linearity and poor recovery time associated with high output voltage.

Summary of the Invention

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.
Accordingly, one aspect of the present invention relates to a detector log video amplifier, the detector log video amplifier comprising: an input configured to receive an input signal, at least two power dividers (19a and 19b), where one power divider (19a) coupled to the input and configured to divide the input signal into two signals, wherein one signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to the other Detector Log Video Amplifier (6a) as a second input signal (4), at least two Detector Log Video Amplifiers (6a, 6b) coupled to the power dividers (19a and 19b) and configured to receive the first input signal (1) from the power divider (19a) and the amplified second input signal (4) from the power divider (19b) and provide the corresponding first and second video signals (18b and 18a) and a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) and configured to receive the first and second video signals (18b and 18a) to obtain a video output response (24) of extended dynamic range.
Another aspect of the present invention relates to a method for dynamic range improvement in detector log video amplifier, the method comprising: receiving an input signal at an input of a detector log video amplifier (501), isolating the received input signal into two input signals by a power divider 19a, wherein one input signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other input signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to a Detector Log Video Amplifier (6a) as a second input signal (4) (502), receiving the first input signal (1) from the power divider (19a) by a detector log video amplifier (6b) and receiving the amplified second input signal (4) via power divider (19b) by a detector log video amplifier (6a), wherein the detector log video amplifiers (6a, 6b) processes the received signals and provide the corresponding first and second video signals (18b and 18a) (503) and combining the first and second video signals (18b and 18a) by a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) to obtain a video output response (24) of extended dynamic range (504).
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Brief description of the drawings

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Figure 1 illustrates the block diagram describing a broadband Wilkinson power divider to divide Radio Frequency input power to the Detector Log Video Amplifiers according to one embodiment of the present invention.
Figure 2 illustrates the summer circuit and techniques used for extending dynamic range improving log linearity, with Continuous Wave Immunity for Continuous Wave signals while providing state of the art pulse performance according to one embodiment of the present invention.
Figure 3 illustrates the performance of the Detector Log Video Amplifier measured on 2 to 18GHz Bandwidth according to one embodiment of the present invention.
Figure 4 illustrates the Output Voltage Versus input power at 3 different frequencies within the 2-18GHz band measured using Automatic Test equipment’s according to one embodiment of the present invention.
Figure 5 illustrates the Video output measured with 100nS pulse width at 18GHz frequency according to one embodiment of the present invention.
Figure 6 illustrates a flowchart for dynamic range improvement in detector log video amplifier according to one embodiment of the present invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

Detailed description of the invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic is intended to provide.
Figs. 1 through 6, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions, in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.
The present invention relates to a 2-18GHz high dynamic range Detector Log Video Amplifier with a limited RF output and more particularly to a Detector Log Video Amplifier with Continuous Wave Immunity, improved dynamic range, improved log linearity, reduced peak overshoot, fast rise time by using unique circuit methodology that is cheaper and less complex than conventional detector log video amplifiers.
The microwave part of it consists of cascaded Broadband Monolithic amplifiers die’s to achieve Limited Power Output of with a gain over 2-18GHz frequency band. Broadband Wilkinson Power dividers have been used to divide Radio Frequency power to the Detector Log Video Amplifiers for detection purpose. As single Detector Log Video Amplifier can provide only limited dynamic range, a two Detector Log Video Amplifiers in parallel configuration, one in amplified path and the other in attenuated path have been used to extend the dynamic range up to 65dB.The Detector Log Video Amplifier kept in amplified path detects one power levels and produce corresponding video frequency signals. Another Detector Log Video Amplifier kept in attenuated path start detecting power levels from another power level and produces corresponding video frequency signals. The Video Signal Levels are video limited and summed using high speed op-amp obtain a logarithmic video response over a 65 dB of extended dynamic range.
A pseudo Alternating Current coupled technique used in this design to achieve Direct Current stability and Continuous Wave immunity over a limited dynamic range of input signals without the effects of baseline shift and poor recovery time associated with AC coupled circuits. Further, the present invention improves the Dynamic Range of 65dB over frequency band of 2-18GHz.
The present invention provides a higher video output voltage without the effects of poor Linearity and poor recovery time associated with high output voltage, improved rise time, simple circuit with minimal tuning and reduced peak overshoot.
Unlike the prior art discussed, the module is realized with unique methodology and less complex circuitry and it is easy for production with minimal tuning. In the present invention, the Detector Log Video Amplifier device is used as a Detector Log Video Amplifier 6a & 6b for detection of Radio Frequency signals and produces a video frequency output signal having an amplitude representation of the power of such Radio Frequency signals. Two DLVAs in parallel configuration, one in amplified path and the other in attenuated path have been used to extend the dynamic range up to 65dB. The Broadband Wilkinson Power dividers have been used to divide RF power to the DLVAs for detection purpose. The DLVA kept in amplified path detects the one power levels and produce corresponding video frequency signals. The DLVA kept in attenuated path start detecting another power level and produces corresponding video frequency signals. Video Signal Levels are video limited and summed using high speed, low noise linear amplifier to obtain a logarithmic video response over a 65 dB of extended dynamic range. The present invention maintains detector log video amplifier with excellent RF gain flatness, improved log linearity, with CW Immunity for CW signals while providing state of the art pulse performance. Further, the present invention maintains, fast rise time, reduced peak overshoot and improved recovery time over an extended 65dB of dynamic range.
Figure 1 illustrates the block diagram describing a broadband Wilkinson power divider to divide Radio Frequency input power to the Detector Log Video Amplifiers according to one embodiment of the present invention.
The figure illustrates the block diagram describing a broadband Wilkinson power divider to divide Radio Frequency input power to the Detector Log Video Amplifiers for detection and cascaded broadband Monolithic amplifier die have been used to amplify the input signal to achieve gain over 2-18GHz and to offset two Detector Log Video Amplifiers for parallel detection. Appropriate attenuator pads are used to bring the Radio Frequency level to within the operating levels of Detector Log Video Amplifiers. One Detector Log Video Amplifier in amplified path detects power levels and produce corresponding video frequency signals. Another Detector Log Video Amplifier kept in attenuated path detects another power level and produces corresponding video frequency signals. Video Signal Levels are video limited and amplified using high speed op-amps before summation to obtain a logarithmic video response over a 65 dB of extended dynamic range.
Referring to Figure 1, which is a detector log video amplifier 17 generates video output to radio frequency (RF) signals applied at an input port. A broadband Wilkinson Power divider has been used to divide Radio Frequency power to the Detector Log Video Amplifiers for detection purpose. The Wilkinson power divider is used at the input stage and appropriate attenuator pads 5 is used to couple the Radio Frequency power levels at port 1 for detection and generating corresponding video output signal at port 18b using first Detector Log Video Amplifier 6b. Input power at port 1 is used at first stage to avoid clipping of dynamic range at Radio Frequency input powers of +1dBm and above. Second Detector Log Video Amplifier 6a is kept in amplifier path. It comprises of Low Noise amplifiers 2a and 2b along with the appropriate attenuator pad so that input power at 2b amplifier should not reach at its absolute maximum rating. Another Wilkinson power divider 19b is used after Low Noise amplifier 2b to couple RF second Input power at port 4 for detection purpose to Detector Log Video Amplifier 6a. Detector Log Video Amplifier 6a generates corresponding video output signal at port 18a. Here, presently available device is used as a Detector Log Video Amplifier 6a and 6b for detection of Radio Frequency signals and produce a video frequency output signal having an amplitude representation of the power of such Radio Frequency signals. The Wilkinson power divider 19b is kept after Amplifier 2b to reduce gain and output power variation across wide frequency band at the input of Detector Log Video Amplifier 6a. The amplifier 2c along with attenuator pad is used after Wilkinson power divider 19b to generate limited Radio Frequency power output of with a gain at output port 3.
In one embodiment, the present invention relates to a detector log video amplifier, the amplifier comprising: an input configured to receive an input signal, at least two power dividers (19a and 19b), where one power divider (19a) coupled to the input and configured to divide the input signal into two signals, wherein one signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to the other Detector Log Video Amplifier (6a) as a second input signal (4), at least two Detector Log Video Amplifiers (6a, 6b) coupled to the power dividers (19a and 19b) and configured to receive the first input signal (1) from the power divider (19a) and the amplified second input signal (4) from the power divider (19b) and provide the corresponding first and second video signals (18b and 18a) and a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) and configured to receive the first and second video signals (18b and 18a) to obtain a video output response (24) of extended dynamic range.
The power divider (19a) positioned at port 1 to avoid clipping of dynamic range at high RF input power/signal. The power divider (19b) is positioned in-between the low noise amplifiers (2b and 2c) to reduce gain variation across wide frequency band at the input of Detector Log Video Amplifier (6a). The low noise amplifier (2c) with attenuator pad positioned subsequently after the power divider (19b) to generate limited RF power/signal output with a gain at output port 3. The low noise amplifiers (2a, 2b and 2c) coupled to amplify the input signal to achieve required gain and to offset two Detector Log Video Amplifiers for parallel detection to extend the dynamic range.
The amplifier comprises attenuator pad (5) to bring the signal (RF) level to within the operating levels of Detector Log Video Amplifier (6b), and detects first power/signal levels and provide corresponding first video frequency signals (18b) and the second Detector Log Video Amplifier (6a) in amplifier path detects second power/signal levels and provide corresponding second video frequency signals (18a). In the present invention, appropriate attenuator pads are used to bring the Radio Frequency level to within the operating levels of Detector Log Video Amplifiers.
The summer circuit comprises a linear amplifier (11a, 11b) configured to receive the second video frequency signals (video output) at port 18a and the first video frequency signals (video output) at port 18b and provide the corresponding output voltages. The output voltages of linear amplifier 11a and 11b are clamped using voltages VH and VL at ports 12a, 13a,12b and 13b in order to avoid overlapping of log slope, where the voltage levels are decided by corresponding output voltage for particular input power/signal. The summer circuit comprises a pseudo AC coupled technique used to achieve Direct Current stability and continuous wave immunity without the effects of baseline shift and poor recovery time associated with Alternating Current coupled circuits. The summer circuit further comprises an integrating feedback network 9 combining a capacitor at port 10 is immune to pulses, samples the Direct Current level at the input port 18a of the pre-log linear stages and feeds back a correction signal to the input of the linear amplifier (11a), where the correction signal cancels the effects of Direct Current drift and provides CW immunity over a limited dynamic range of input RF signals.
The output voltages of linear amplifiers 11a and 11b are summed at port 22a using an amplifier 15 and a capacitor Comp at port 15 is used to control peak overshoot and rise time of video output voltage at port 24. The output voltages of linear amplifiers are summed using high speed, low Noise linear amplifier. The dynamic range is limited at the high end by output voltage swing of linear amplifier. So linear amplifier with high output voltage swing is used to drive high end input power for required video load & Video Bandwidth. The Capacitor C comp used in shunt to linear amplifier 15 to control peak overshoot and rise time of video output.

Figure 2 illustrates the summer circuit and techniques used for extending dynamic range improving log linearity, with Continuous Wave Immunity for Continuous Wave signals while providing state of the art pulse performance according to one embodiment of the present invention.
The figure illustrates the summer circuit and techniques used for extending dynamic range improving log linearity, with Continuous Wave Immunity for Continuous Wave signals while providing state of the art pulse performance. The corresponding video output signals at port 18a and 18b is fed to the summer circuit 7 as shown in Figure 2 to obtain a video output response over a 65 dB of extended dynamic range. The extended dynamic range of the Detect
or Log Video Amplifier is limited at the low end by the thermal noise floor, the Radio Frequency bandwidth, and the noise figure of the Radio Frequency amplifiers. The dynamic range is limited at the high end by the amount of power available and output voltage swing of linear amplifiers for required load in summer circuit 7. Detected Video output at port 18a for input power is fed to a linear amplifier 11a. Detected Video output at port 18b for input power level is fed to a linear amplifier 11b. In order to avoid overlapping of log slope, Output voltages of linear amplifier 11a and 11b are clamped using voltages VH and VL at ports 12a, 13a ,12b and 13b. Voltage at 12a and 13b is decided by corresponding output voltage for specific input power. Voltage at 12b and 13b is decided by corresponding output voltage respectively.
The Direct Current feedback technique is used to minimize the Direct Current offset voltage associated with the linear video amplifier 11a. The integrating feedback network 9 combining Capacitor at port 10 is immune to pulses but samples the Direct Current level at the input port 18a of the pre-log linear stages and feeds back a correction signal to the input of the first linear amplifier. The correction signal will cancel the effects of Direct Current drift over temperature and will provide CW immunity over a limited dynamic range of input RF signals. The main advantage of Pseudo AC coupled DLVA is DC stability and CW immunity without the effects of baseline shift and poor recovery time associated with AC coupled circuits.
Output Voltages of linear amplifiers 11a and 11b are summed at port 22a using High speed, Low Noise linear amplifier 15. The dynamic range is limited at the high end by output voltage swing of linear amplifier 15. So, the linear amplifier 15 with high output voltage swing is used to drive corresponding highest of input power for required load. Simultaneously, it gives low noise to handle lower voltage levels at sensitivity to give complete improved dynamic range. Capacitor Comp at port 15 is used to control peak overshoot and rise time of video output voltage at port 24.
Figure 3 illustrates the performance of the Detector Log Video Amplifier measured on 2 to 18GHz Bandwidth according to one embodiment of the present invention.
The figure illustrates the performance of the Detector Log Video Amplifier measured on 2 to 18GHz Bandwidth. A plot 20 of the gain response is shown in Figure 3. This figure shows gain with flatness over the full 2 to 18GHz frequency range measured at output port 3. To meet log linearity and frequency flatness of video output gain flatness plays a major role. So, the gain equalizers commercially available are used after Low noise amplifier 2a and 2b to correct gain variation at the input of Detector Log Video Amplifier 6a.
Figure 4 illustrates the Output Voltage Versus input power at 3 different frequencies within the 2-18GHz band measured using Automatic Test equipment’s according to one embodiment of the present invention.
The figure shows the Output Voltage Versus input power at 3 different frequencies within the 2-18GHz band measured using Automatic Test Equipment. The upper cut-off and lower cutoff lines give ±3dB accuracy limits, reference value gives ideal response considering slope. This plot shows linearity and logging accuracy over 65dB of dynamic range with slope for full 2 to18GHz band.
The figure 5 illustrates the measured results for pulse characteristics measured at input power at 18GHz of Frequency with 100 ns pulse width.
Figure 6 illustrates a flowchart for dynamic range improvement in detector log video amplifier according to one embodiment of the present invention.
The figure illustrates a flowchart/method for dynamic range improvement in detector log video amplifier. The method further comprising: receiving an input signal at an input of a detector log video amplifier (501), isolating the received input signal into two input signals by a power divider 19a, wherein one input signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other input signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to a Detector Log Video Amplifier (6a) as a second input signal (4) (502), receiving the first input signal (1) from the power divider (19a) by a detector log video amplifier (6b) and receiving the amplified second input signal (4) via power divider (19b) by a detector log video amplifier (6a), wherein the detector log video amplifiers (6a, 6b) processes the received signals and provide the corresponding first and second video signals (18b and 18a) (503) and combining the first and second video signals (18b and 18a) by a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) to obtain a video output response (24) of extended dynamic range (504).
The method of combining the first and second video signals by the summer circuit (7) further comprises few steps: amplifying the received first and second video signals (18b and 18a) by a linear amplifier (11a, 11b) of the summer circuit (7), clamping the output voltages of linear amplifiers (11a,11b) using voltages VH and VL at ports 12a, 13a,12b and 13b in order to avoid overlapping of log slope, where the voltage levels are decided by corresponding output voltage for particular input power/signal, sampling the direct current at the input port of 18a by an integrating feedback network 9 in order to cancel the effects of Direct Current drift and provides CW immunity over a limited dynamic range of input RF signals and summing the output voltages of linear amplifiers (11a,11b) at port (22a) using an amplifier (15) and in order to obtain a video output response (24) of extended dynamic range.
Those skilled in this technology can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.
FIGS. 1-6 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. FIGS. 1-6 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.
In the foregoing detailed description of embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment.
It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein,” respectively.

,CLAIMS:We Claim:

1. A detector log video amplifier, the amplifier comprising:
an input configured to receive an input signal;
at least two power dividers (19a and 19b), where one power divider (19a) coupled to the input and configured to divide the input signal into two signals, wherein one signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to the other Detector Log Video Amplifier (6a) as a second input signal (4);
at least two Detector Log Video Amplifiers (6a, 6b) coupled to the power dividers (19a and 19b) and configured to receive the first input signal (1) from the power divider (19a) and the amplified second input signal (4) from the power divider (19b) and provide the corresponding first and second video signals (18b and 18a); and
a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) and configured to receive the first and second video signals (18b and 18a) to obtain a video output response (24) of extended dynamic range.

2. The detector log video amplifier as claimed in claim 1, wherein the power divider (19b) is positioned in-between the low noise amplifiers (2b and 2c) to reduce gain variation across wide frequency band at the input of Detector Log Video Amplifier (6a).

3. The detector log video amplifier as claimed in claim 1, wherein low noise amplifier (2c) with attenuator pad positioned subsequently after the power divider (19b) to generate limited RF power/signal output with a gain at output port 3.

4. The detector log video amplifier as claimed in claim 1, wherein the low noise amplifiers (2a, 2b and 2c) coupled to amplify the input signal to achieve required gain and to offset two Detector Log Video Amplifiers for parallel detection to extend the dynamic range.

5. The detector log video amplifier as claimed in claim 1, wherein the amplifier comprises attenuator pad (5) to bring the signal (RF) level to within the operating levels of Detector Log Video Amplifier (6b), and detects first power/signal levels and provide corresponding first video frequency signals (18b) and the second Detector Log Video Amplifier (6a) in amplifier path detects second power/signal levels and provide corresponding second video frequency signals (18a).

6. The detector log video amplifier as claimed in claim 1, wherein the power divider (19a) positioned at port 1 to avoid clipping of dynamic range at high RF input power/signal.

7. The detector log video amplifier as claimed in claim 1, wherein the summer circuit comprises a linear amplifier (11a, 11b) configured to receive the second video frequency signals (video output) at port 18a and the first video frequency signals (video output) at port 18b and provide the corresponding output voltages.

8. The detector log video amplifier as claimed in claim 1, wherein the output voltages of linear amplifier 11a and 11b are clamped using voltages VH and VL at ports 12a, 13a,12b and 13b in order to avoid overlapping of log slope, where the voltage levels are decided by corresponding output voltage for particular input power/signal.

9. The detector log video amplifier as claimed in claim 1, wherein the summer circuit comprises a pseudo AC coupled technique used to achieve Direct Current stability and continuous wave immunity without the effects of baseline shift and poor recovery time associated with Alternating Current coupled circuits.

10. The detector log video amplifier as claimed in claim 1, wherein the summer circuit comprises an integrating feedback network 9 combining a capacitor at port 10 is immune to pulses, samples the Direct Current level at the input port 18a of the pre-log linear stages and feeds back a correction signal to the input of the linear amplifier (11a), where the correction signal cancels the effects of Direct Current drift and provides CW immunity over a limited dynamic range of input RF signals.

11. The detector log video amplifier as claimed in claim 1, wherein the output voltages of linear amplifiers 11a and 11b are summed at port 22a using an amplifier 15 and a capacitor Comp at port 15 is used to control peak overshoot and rise time of video output voltage at port 24.

12. A method for dynamic range improvement in detector log video amplifier, the method comprising:
receiving an input signal at an input of a detector log video amplifier (501);
isolating the received input signal into two input signals by a power divider 19a, wherein one input signal is provided to a Detector Log Video Amplifier (6b) as a first input signal (1) and other input signal is provided to low noise amplifiers (2a and 2b) to amplify the input signal and provide the amplified signal to a Detector Log Video Amplifier (6a) as a second input signal (4) (502);
receiving the first input signal (1) from the power divider (19a) by a detector log video amplifier (6b) and receiving the amplified second input signal (4) via power divider (19b) by a detector log video amplifier (6a), wherein the detector log video amplifiers (6a, 6b) processes the received signals and provide the corresponding first and second video signals (18b and 18a) (503); and
combining the first and second video signals (18b and 18a) by a summer circuit (7) coupled to the Detector Log Video Amplifiers (6a, 6b) to obtain a video output response (24) of extended dynamic range (504).

13. The method as claimed in claim 11, wherein combining the first and second video frequency signals by the summer circuit (7) further comprises few steps:
amplifying the received first and second video frequency signals (18b and 18a) by a linear amplifier (11a, 11b) of the summer circuit (7);
clamping the output voltages of linear amplifiers (11a,11b) using voltages VH and VL at ports 12a, 13a,12b and 13b in order to avoid overlapping of log slope, where the voltage levels are decided by corresponding output voltage for particular input power/signal; and
sampling the direct current at the input port of 18a by an integrating feedback network 9 in order to cancel the effects of Direct Current drift and provides CW immunity over a limited dynamic range of input RF signals: and
summing the output voltages of linear amplifiers (11a,11b) at port (22a) using an amplifier (15) and in order to obtain a video output response (24) of extended dynamic range.
Dated this 29th day of September, 2018

For BHARAT ELECTRONICS LIMITED,
By their Agent,

D. Manoj Kumar) (IN/PA – 2110)
KRISHNA & SAURASTRI ASSOCIATES LLP