DESC:TECHNICAL FIELD
[0001] The present disclosure relates to field of radio frequency circuits and more particularly to the field of PIN diode attenuators.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Conventionally, diode attenuators (for example: step attenuators, digital attenuators, voltage variable attenuators etc.) are used in various applications worldwide, as per system level requirement. The various applications include Radar systems. Some diode attenuators changes in steps and some changes linearly to applied bias voltage. EP0788223A2 “PIN Diode Variable Attenuator” talks about providing variable attenuation in pie configuration with low power & fixed characteristics of diodes over temperature & frequency. EP0903850A2 “PIN Diode Variable Attenuator” uses pi variable attenuator with wide attenuation dynamics, and relevant control circuit is also having limitation of characteristics totally depends on diodes which are fixed in nature. US4590417 “Voltage Controlled Diode Attenuator” has no coils and, therefore, may be built in integrated circuit form. At least one pair of similarly poled diodes and a resistor are connected in a series circuit. An input signal and variable control voltage are applied to a junction between first and adjoining sides of the pair of diodes. An output voltage appears at an opposite side of one of the diodes. A differential amplifier applies a fixed bias voltage to the output terminal, and a negative feedback is connected between the opposite side of the one diode and an input to the differential amplifier. US4097827 “Constant Impedance, Constant Phase PIN Diode Attenuator” uses PIN diodes in a double pi configuration. A control voltage is applied simultaneously thereto thus attaining 40 dB attenuation without substantially varying phase and amplitude characteristics. The prior art references are rated for low power, lower attenuation range with inferior linearity and does not include any configuration mechanism for compensating attenuation characteristics of the diode.
[0004] The PIN diodes used in discussed attenuators are not characterized over a temperature and frequency range, thereby, system incorporating them do not have an accurate tracking. Hence, it is desired to have an improved PIN diode attenuator configuration that has capability to adjust its accuracy/linearity over temperature and frequency band of applications.

OBJECTS OF THE PRESENT DISCLOSURE
[0005] A general objective of the present disclosure is to provide an improved configuration of PIN diode attenuator.
[0006] It is an objective of the present disclosure to provide a PIN diode attenuator with adjustable accuracy/linearity over frequency and temperature range.
[0007] It is an objective of the present disclosure to provide a small size, low cost attenuator that provides flexibility to use it for sensitivity time control (STC) attenuator applications in primary and secondary radar receivers etc.

SUMMARY
[0008] The present disclosure relates to field of block up converters (BUC). More particularly, it relates to an improved method for generating local oscillator (LO) signal for BUC.
[0009] A P-intrinsic-N (PIN) diode attenuator, said attenuator comprises: a plurality of PIN diodes being configured to receive an input radio frequency (RF) signal through a first isolator and generates an output, wherein said plurality of PIN diodes are coupled in shunt configuration; atleast one temperature sensing device configured to sense temperature of said plurality of PIN diodes, and generates an output signal; a bias card, said bias card is configured to receive said output of said atleast one temperature sensor and said output, through an output circuit, of said plurality of PIN didoes, and generate plurality of control signals, wherein said bias card comprises a configurable lookup table (LUT); wherein said plurality of PIN diodes are configured to receive said control signals generated by said bias card.
[0010] In an embodiment, said plurality of PIN diodes is characterized over a temperature range to study and prepare said LUT.
[0011] In an embodiment, a LUT data is received at a periodic temperature interval and is applied to said plurality of PIN diodes.
[0012] In an embodiment, said output circuit comprises: a second isolator operatively coupled to said output of wherein said plurality of PIN diodes, a plurality of amplifiers operatively coupled to an output of said second isolator, a first band pass filter (BPF1) operatively coupled to an output of said plurality of amplifier, a mixer operatively coupled to an output of said BPF1, a second band pass filter (BPF2) operatively coupled to an output of said mixer, an amplifier (A) operatively coupled to an output of said BPF2, a coupler operatively coupled to an output of said amplifier A, and a detector operatively coupled to an output of said coupler.
[0013] In an embodiment, said mixer combines said output of said BPF1 with a local oscillator input.
[0014] In an embodiment, an output of said detector is configured to be received by said bias card.
[0015] In an embodiment, said atleast one temperature sensing device comprises any or combination of a thermocouple, a thermometer, a transducer, a temperature sensor.
[0016] In an embodiment, the attenuator has an attenuation range: 60db Min (over a temperature range -300C to +600C and frequency range).
[0017] In an embodiment, the attenuator has an attenuation tracking: < ±0.3dB (0 to 50 dB), ±<0.5 dB (50 to 60 dB) over the frequency and temperature range.
[0018] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.
[0020] FIG. 1 shows design of high power attenuators, in accordance with embodiments of the present disclosure.
[0021] FIG. 2 shows simulated data of attenuation, in accordance with embodiments of the present disclosure.
[0022] FIG. 3 shows typical system using variable attenuator, in accordance with embodiments of the present disclosure.
[0023] FIG. 4 shows typical system characterization setup, in accordance with embodiments of the present disclosure.
[0024] FIG. 5 shows internal structure of bias card for configurable lookup table (LUT), in accordance with embodiments of the present disclosure.
[0025] 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
[0026] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0027] If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0028] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0029] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0030] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0031] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).
[0032] The present disclosure relates to field of radio frequency (RF) circuits and more particularly to the field of PIN diode attenuators.
[0033] FIG. 1 discloses a design for high power attenuator according to an embodiment of the invention. Disclosed attenuator used multiple diodes to achieve 60db or better attenuation for radar blanking with controlled bias current of didoes. The FIG.1 shows plurality of PIN diodes in shunt configuration to provide a certain amount of attenuation. The PIN diodes are provided with a configurable control using a configurable lookup table (LUT) to compensate attenuation variations with temperature and frequency range. The LUT provides an excellent attenuation tracking of <±0.3dB (0 to 50 dB), ±<0.5 dB (50 to 60 dB). FIG. 3 shows simulated data of attenuation according to an embodiment of an invention.
[0034] FIG. 3 shows a system using variable attenuator according to an embodiment of an invention. The figure shows a compact configuration PIN based variable attenuator design where the PIN diodes are in shunt configuration with isolators (isolator 1, isolator 2) at input and output, respectively. The disclosed attenuator provides insertion loss: 1.2db typ (including isolators) Over the temperature range-30ºC to +60ºC & Freq range & Attenuation Range: 60 dB Min (Over the temperature range- 30ºC to +60ºC & Freq range). The FIG. 3 shows a first isolator (isolator 1) configured to receive an input radio frequency (RF) signal. A plurality of PIN didoes, connected in a shunt configuration, is connected at an output of the said first isolator. A temperature sensing device (temperature sensor) is configured to sense temperature of said plurality of PIN diodes and receives an input from a bias card, and generated an output. The output of said temperature sensing device is received by said bias card (including said LUT), based on the received output said bias card generates a plurality of control signals (CTRL1). The plurality of PIN diodes is configured to receive said CTRL1 control signal.
[0035] According to an embodiment of the invention, a second isolator (isolator 2) is configured to receive an output of said plurality of PIN diodes, a plurality of amplifiers (AMP-1) is configured to receive an output of said second isolator, a first band pass filter (BPF1) is configured to receive an output of said plurality of amplifiers, a mixer is configured to receive an output of said BPF1, said mixer is configured to mix said output of the BPF1 with a local oscillator (LO) input. A second band pass filter (BPF2) is configured to receive an output of said mixer, an amplifier (AMP-2) is configured to receive an output of said BPF2, a coupler is configured to receive an output of said amplifier (AMP-2) and generated an intermediate frequency (IF) output. Said IF output signal is received, through a detector, by said bias card.
[0036] According to an embodiment of the invention, power handling of designed variable attenuator is better than 2KW (Peak) with attenuation range: 60db Min (over temperature range -300C to +600C and frequency range), and attenuation tracking: < ±0.3dB (0 to 50 dB), ±<0.5 dB (50 to 60 dB) over the frequency and temperature range. PIN diodes of said plurality of PIN diodes are attenuation characterized over a temperature range of -30°C to +65 °C to study & preparation of Lookup table as per temperature & Frequency Range. FIG.4 shows characterization setup of attenuator according to an embodiment of the invention. LUT data is received for every 100C and is applied to the PIN diodes through hardware configuration shown in FIG. 5. The configuration can be changed as per specific requirement and availability of hardware. The temperature sensor senses the temperature, and per temperature value, memory mapped data is received from the LUT. The received data is used to apple specific corrections value needed to maintain attenuation accuracy.
[0037] Thus, it will be appreciated by those of ordinary skill in the art that the diagrams, schematics, illustrations, and the like represent conceptual views or processes illustrating systems and methods embodying this invention. The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing associated software. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the entity implementing this invention. Those of ordinary skill in the art further understand that the exemplary hardware, software, processes, methods, and/or operating systems described herein are for illustrative purposes and, thus, are not intended to be limited to any particular named.
[0038] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claim.
[0039] In the foregoing description, numerous details are set forth. It will be apparent, however, to one of ordinary skill in the art having the benefit of this disclosure, that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, to avoid obscuring the present invention.
[0040] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other)and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Within the context of this document terms "coupled to" and "coupled with" are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
[0041] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C …. N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0042] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0043] The present disclosure provides an improved configuration of PIN diode attenuator.
[0044] The present disclosure provides a PIN diode attenuator with adjustable accuracy/linearity over frequency and temperature range.
[0045] The present disclosure a small size, low cost attenuator that provides flexibility to use it for sensitivity time control (STC) attenuator applications in primary and secondary radar receivers etc.
,CLAIMS:1. A P-intrinsic-N (PIN) diode attenuator, said attenuator comprises:
a plurality of PIN diodes being configured to receive an input radio frequency (RF) signal through a first isolator and generates an output, wherein said plurality of PIN diodes are coupled in shunt configuration;
atleast one temperature sensing device configured to sense temperature of said plurality of PIN diodes, and generates an output signal;
a bias card, said bias card is configured to receive said output of said atleast one temperature sensor and said output, through an output circuit, of said plurality of PIN didoes, and generate plurality of control signals, wherein said bias card comprises a configurable lookup table (LUT);
wherein said plurality of PIN diodes are configured to receive said plurality of control signals generated by said bias card.
2. The attenuator as claimed in claim1, wherein said plurality of PIN diodes is characterized over a temperature range to study and prepare said LUT.
3. The attenuator as claimed in claim1, wherein, a LUT data is received at a periodic temperature interval and is applied to said plurality of PIN diodes.
4. The attenuator as claimed in claim1, wherein said output circuit comprises: a second isolator operatively coupled to said output of wherein said plurality of PIN diodes, a plurality of amplifiers operatively coupled to an output of said second isolator, a first band pass filter (BPF1) operatively coupled to an output of said plurality of amplifier, a mixer operatively coupled to an output of said BPF1, a second band pass filter (BPF2) operatively coupled to an output of said mixer, an amplifier (A) operatively coupled to an output of said BPF2, a coupler operatively coupled to an output of said amplifier A, and a detector operatively coupled to an output of said coupler.
5. The attenuator as claimed in claim1, wherein said mixer combines said output of said BPF1 with a local oscillator input.
6. The attenuator as claimed in claim1, wherein an output of said detector is configured to be received by said bias card.
7. The attenuator as claimed in claim1, wherein said atleast one temperature sensing device comprises any or combination of a thermocouple, a thermometer, a transducer, a temperature sensor.
8. The attenuator as claimed in claim1, wherein the attenuator has an attenuation range: 60db Min (over a temperature range -300C to +600C and frequency range).
9. The attenuator as claimed in claim1, wherein the attenuator has an attenuation tracking: < ±0.3dB (0 to 50 dB), ±<0.5 dB (50 to 60 dB) over the frequency and temperature range.