Claims:1. A system for stepped impedance matching for a power amplifier (PA) die, the system comprises:
multiple matching sections operatively coupled with the PA die, wherein the multiple matching sections comprise:
an input matching section coupled with an input terminal of the PA die, and configured to match source impedance, of a source coupled to the input terminal, with a first pre-determined impedance; and
an output matching section coupled with an output terminal of the PA die, and configured to match load impedance, of a load coupled to the output terminal, with a second pre-determined impedance; and
a biasing section electronically coupled with one or more terminals of the PA die, wherein the biasing section is configured to carry out biasing of the PA die within a pre-defined limit to enable optimum operation of the PA die.
2. The system as claimed in claim 1, wherein the biasing section comprises a line having dimensions in multiples of a pre-defined wavelength and a radial stub.
3. The system as claimed in claim 2, wherein the dimensions of the line facilitate in providing a short path for DC signals, open path for RF signals, and in enhancing current handling capacity.
4. The system as claimed in claim 1, wherein the biasing section is fed with a DC supply supplying electric power within a pre-defined range.
5. The system as claimed in claim 1, wherein the PA die is coupled with a carrier plate in order to facilitate spreading of a heat, resulting due to operation of the PA die, on a heat sink.
6. The system as claimed in claim 5, wherein materials having matching coefficient of thermal expansions are selected for configuration of the PA die and the carrier plate for facilitating similar expansions of the PA die and the carrier plate.
7. The system as claimed in claim 5, wherein the carrier plate is made of copper-molybdenum-copper (CMC).
8. The system as claimed in claim 1, wherein the PA die is a GaN based power amplifier die.
9. The system as claimed in claim 1, wherein determination of the first impedance and the second impedance is optimized using source pull and load pull techniques respectively.
10. The system as claimed in claim 1, wherein the system, comprises of 250 nanometre (nm) PA die, RF substrate having dielectric constant 10.2 and dissipation factor 0.0025, and a CMC carrier plate.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to the field of power amplifier. In particular, the present disclosure relates to matching of very low impedance of Ku-Band (Power Amplifier) PA Die using Stepped Impedance Matching Technique.

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] Travelling wave tube amplifier (TWTAs) are specialized vacuum tubes that are used in electronic circuits for amplifying microwave signals. The TWTs and klystron belong to a category of linear beam tubes. In case of the klystron, radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube.
[0004] TWTs and Multi cavity klystron beams (MBKs) are generally used for high power amplifications. For Ku band applications, TWTAs and MBKs are widely used due to their high output power and high efficiency compared to solid state power amplifier (SSPAs). However, TWTAs require very high supply voltage to operate, have a limited lifetime, and also TWTAs have an inherent high turn on time. These characteristics impose limitations that make them inconvenient for broadcasting and news gathering systems and related applications. On the other hand, SSPAs require lower supply voltage, have longer lifetime and also they require shorter preparation time to transmit full output voltage as compared to TWTAs.
[0005] Monolithic microwave integrated circuit (MMIC) is a type of integrated circuit (IC) device that may operate at microwave frequencies, i.e. 300 MHz to 300 GHz, and may typically perform functions such as microwave mixing, power amplification, low-noise amplification, and high-frequency switching. Inputs and outputs of a MMIC device are frequently matched to a characteristic impedance for ensuring optimum functioning of the MMIC device. However, the available packaged Ku Band MMIC device is generally not able to provide high output power and higher power gain in upper Ku Band. Moreover, it may face tuning related issues, and may not be cost-effective.
[0006] There is, therefore, a requirement in the art to provide an efficient matching technique for design of unmatched Ku band PA die to get higher output power & higher power gain in operating bandwidth

OBJECTS OF THE PRESENT DISCLOSURE
[0007] A general object of the present disclosure is to provide a smart, economically feasible, and efficient stepped impedance matching technique for a very low impedance Ku-Band PA.
[0008] Another object of the present disclosure is to provide a system equipped with a PA die attached with carrier plate, which facilitates in transferring the heat generated to surrounding during operation of a PA.

SUMMARY
[0009] Aspects of the present disclosure relates, in general, to the field of power amplifier. In particular, the present disclosure relates to matching of very low impedance of Ku-Band PA Die using Stepped Impedance Matching Technique.
[0010] An aspect of the present disclosure pertains to an efficient and cost-effective system for stepped impedance matching for a power amplifier (PA) die, the system comprises: multiple matching sections operatively coupled with the PA die, wherein the multiple matching sections consists of: an input matching section coupled with GATE terminal of the PA die, and configured to match with source impedance, and an output matching section coupled with Drain terminal of the PA die, and configured to match with load impedance, and a biasing section electronically coupled with gate and drain terminals of the PA die, wherein the biasing section may be configured to carry out biasing of the PA die within a pre-defined limit to enable optimum operation of the PA die.
[0011] In an aspect, the biasing section may consists of a line having dimensions in multiples of a pre-defined wavelength and a radial stub.
[0012] In an aspect, the dimensions of the line may facilitate in providing a short path for DC signals, open path for RF signals, and capable of current handling.
[0013] In an aspect, the biasing section may be fed with a DC supply supplying electric power within a pre-defined range.
[0014] In an aspect, the PA die is attached with a carrier plate in order to facilitate spreading of a heat, resulting due to operation of the PA die,
[0015] In an aspect, carrier plate materials chosen having matching coefficient of thermal expansions similar to the configuration of the PA die in order to facilitate spreading of heat equally in all directions.
[0016] In an aspect, the carrier plate may be made of copper-molybdenum-copper (CMC).
[0017] In an aspect, the PA die may be a GaN based power amplifier die.
[0018] In an aspect, determination of the source impedance and the load impedance may be optimized using source pull and load pull techniques respectively.
[0019] In an aspect, the system comprises of 250 nanometre (nm) PA die, RF substrate having dielectric constant 10.2 and dissipation factor 0.0025 and CMC carrier plate.
[0020] 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.
[0021] Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF DRAWINGS
[0022] 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.
[0023] FIG. 1 illustrates an exemplary schematic representation of the proposed system, to elaborate upon its working in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0024] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0025] 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.
[0026] Embodiments of the present disclosure relates, in general, to the field of power amplifier. In particular, the present disclosure relates to matching of very low impedance of Ku-Band PA Die using stepped impedance matching technique.
[0027] An aspect of the present disclosure pertains to an efficient and cost-effective system for stepped impedance matching for a power amplifier (PA) die, the system comprises: multiple matching sections operatively coupled with the PA die, wherein the multiple matching sections consists of: an input matching section coupled with gate terminal of the PA die, and configured to match with source impedance, and an output matching section coupled with Drain terminal of the PA die, and configured to match with load impedance, and a biasing section electronically coupled with gate and drain terminals of the PA die, wherein the biasing section may be configured to carry out biasing of the PA die within a pre-defined limit to enable optimum operation of the PA die
[0028] In an embodiment, the biasing section can include a line having dimensions in multiples of a pre-defined wavelength and a radial stub.
[0029] In an embodiment, the dimensions of the line can facilitate in providing a short path for DC signals, open path for RF signals, and in enhancing current handling capacity.
[0030] In an embodiment, the biasing section can be fed with a DC supply supplying electric power within a pre-defined range.
[0031] In an embodiment, the PA die can be coupled with a carrier plate in order to facilitate spreading of a heat, resulting due to operation of the PA die, on a heat sink.
[0032] In an embodiment, materials having matching coefficient of thermal expansions can be selected for configuration of the PA die and the carrier plate for facilitating similar expansions of the PA die and the carrier plate.
[0033] In an embodiment, the carrier plate can be made of copper-molybdenum-copper (CMC).
[0034] In an embodiment, the PA die can be a GaN based power amplifier die.
[0035] In an embodiment, determination of the first impedance and the second impedance can be optimized using source pull and load pull techniques respectively.
[0036] In an aspect, the system can include 250 nanometre (nm) PA die, RF substrate having dielectric constant 10.2, dissipation factor 0.0025, and CMC carrier plate.
[0037] FIG. 1 illustrates an exemplary schematic representation of the proposed system, to elaborate its working in accordance with an embodiment of the present disclosure.
[0038] According to an embodiment, in comparison to MMIC power amplifier, discrete Gallium nitride (GaN) transistor based PA can obtain higher output power in a specific band and can have a greater tuning flexibility. Moreover, the GaN transistor based PA can have very lower cost as compared to package MMIC device.
[0039] In an embodiment, the system 100 may facilitate identification of wide bandwidth and high power unmatched Power Amplifier (PA) die 102, which can be further confirmed through simulation and hardware design. In another embodiment, load pull and source pull can be performed to obtain optimum load impedance and source impedance for the PA die 102, thereby a higher peak output power and higher power added efficiency in operating bandwidth. The obtained load and source impedance may be so small that the impedances may require a multi-stage impedance transformer with a high impedance ratio to secure the proper operating bandwidth.
[0040] In an illustrative embodiment, the PA die 102 can be configured to operate for a higher power. In another illustrative embodiment, the obtained load and source impedance can be matched with a 50 ohm using multi section stepped impedance transformer, which can result in a large matching circuit. However, while maintaining the circuit performance, reducing the size of the matching circuit is also essential because of the limited space available in the system 100.
[0041] In yet another illustrative embodiment, an overall input and output matching circuit can be fabricated on a low loss substrate having a high dielectric constant ??0 =10.2, thickness of 10 mils (10-2 of an inch), dissipation factor of .0025. The substrate can be incorporated with a Printed Circuit Board (PCB) having thickness of 10 mils.
[0042] In an embodiment, multi section step impedance matching techniques can be used to match the optimum load and source impedance to 50 O using smith chart utility. Circuit and EM simulation can also be done for the input and output impedance matching in order to obtain higher peak output power, higher power gain and higher power added efficiency. Moreover, better input return loss and better output return loss can be obtained after introducing the matching circuits in the operating bandwidth.
[0043] In an embodiment, the system 100 can include input matching sections operatively coupled with the PA die 102, wherein the input matching section 108 (multi section input step impedance matching) match optimum source impedance obtained from source pull simulations to 50 ohm by multi section stepped impedance transformer.
[0044] In an embodiment, the system 100 can include output matching sections operatively coupled with the PA die 102, wherein the output matching section 110 (multi section output step impedance matching) is used to match optimum load impedance obtained from load pull simulations to 50 ohm by multi section stepped impedance transformer.
[0045] In an illustrative embodiment, a biasing circuit 114 (interchangeably referred to as DC biasing supply 114, herein) consisting of a ? /4 DC feed line 112 and radial stub can be designed, such that the biasing circuit 114 can feed voltage to gate 104 and drain 106 of the power amplifier for proper operation. The ? /4 line may provide a short path for DC signal for example, DC voltage and open path for RF signal and width of ? /4 line may provide optimum current handling capability for the system 100.
[0046] In an illustrative embodiment, there can be two separate biasing circuits and DC feed lines for the input matching section 108 and the output matching section 110. In another illustrative embodiment, the input matching section 108 and the output matching section 110 can be connected to a single biasing circuit and DC feed line.
[0047] In yet another illustrative embodiment, the input matching section 108 and the output matching section 110 can be coupled with the power amplifier through one or more gold bond wires 118. In yet another illustrative embodiment, each of the input matching section 108 and the output matching section 110 can be coupled with a 50 ohm impedance via a DC blocking capacitor 116.
[0048] In one embodiment, the PA die 102 can be attached to a carrier plate in order to spread heat on a heat sink. In other embodiment, to cater for differential expansions happening between materials of the PA die and the carrier plate after both are attached, it may be recommended to maintain a close match between coefficients of thermal expansion (CTE) of both – the PA die and the carrier plate.
[0049] For low frequency band and low power amplifier, generally carrier plates with Kover material are used , but Kover cannot be used for designing of GaN based high frequency and high power amplifier as CTE of Kover differs and do not match with the CTE of GaN power amplifier.
[0050] Therefore, in an illustrative embodiment, the carrier plate can be designed using a 60 mils Copper molybdenum copper (CMC), which can further be attached to bare PA die for facilitating dissipation of the heat generated due to operation of the PA die. CMC material can be used as it has almost same coefficient of thermal expansion as compared to the GaN PA die. The CTE of CMC and GaN lies between 5ppm/K to 7ppm/K.
[0051] The proposed and designed SSPA (solid state power amplifier) using GaN HEMT power amplifier can act as the basic building block, thereby combining multiple such power amplifiers can be used to replace conventional TWTAs and multi cavity klystron beam in Ku band.
[0052] 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 patent 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 “includes” and “including” 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 refer to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0053] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practised with modification within the spirit and scope of the appended claims.
[0054] 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
[0055] The present disclosure provides a smart, economically feasible, and efficient matching technique for a very low impedance of Ku-Band PA die.
[0056] The present disclosure provides a system having a compact size.
[0057] The present disclosure provides a cost-effective system as compared to packaged PA.
[0058] The present disclosure provides a basic block, such that combining multiple of such basic blocks can replace conventional high power TWTAs and multi cavity klystron used in Radars.