DESC:FORM – 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(SEE SECTION 10, RULE 13)

COMPACT PULSED HIGH-POWER X-BAND
MULTI-CHANNEL TRANSMITTER

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.
TECHNICAL FIELD
[0001] The present invention relates to compact pulsed high-power X-band multi-channel transmitter for radio wave analog beam forming networks.
BACKGROUND
[0002] In radio wave analog beam forming networks, a beam of radio waves can be electronically steered to point in different directions without mechanically steering the antenna. In such systems, the antenna typically includes individual radiating elements which are arranged in the form of a matrix to obtain a radiation pattern for a desired application. Each radiating antenna element is directly connected to a transmitter. Further, solid-state based power amplifiers are used to generate necessary pulsed power for the desired application. Electronic beam steering is achieved by digital phase shifters in each arm of the transmitter. The operation of the transmitters and other sub-systems are controlled by real time signal processing systems. Advantageously, in radio wave analog beam forming networks, there is no single point of failure and the system continues to operate with graceful degradation, thus enhancing the system reliability.
[0003] There is therefore felt a need of an invention which provides compact pulsed high-power X-band multi-channel transmitter for radio wave analog beam forming networks.
SUMMARY
[0004] This summary is provided to introduce concepts of the invention related to a compact pulsed high-power X-band multi-channel transmitter for radio wave analog beam forming networks, as disclosed herein. This summary is neither intended to identify essential features of the invention as per the present invention nor is it intended for use in determining or limiting the scope of the invention as per the present invention.
[0005] In accordance with an exemplary implementation of the present invention there is provided, an X-band multi-channel transmitter. The transmitter comprises: a radio frequency (RF) booster configured to receive an external RF signal from an external device and at least boost the power of the external RF signal to a predetermined level; a power splitter connected to the RF booster and configured to split a boosted RF signal received therefrom into a plurality of equally powered RF signals; a plurality of transmit channels corresponding to the plurality of equally powered RF signals, each transmit channel connected to an output of the power splitter and configured to at least amplify an equally powered RF signal received therefrom and transmit the amplified RF signal; a pulsing circuit configured to generate a plurality of pulses for operation of the transmit channels; and a control unit configured to control the operation of the pulsing circuit, the RF booster and each of the transmit channels.
[0006] In an embodiment, the RF booster comprises: a low pass filter (LPF) configured to filter the external RF signal; an attenuator connected to the LPF and configured to attenuate a filtered RF signal received therefrom; a common amplifier connected to the attenuator and configured to amplify an attenuated RF signal received from the attenuator to boost the power of the attenuated RF signal to the predetermined level.
[0007] In an embodiment, each transmit channel comprises: a phase shifter configured to shift the phase of the equally powered RF signal; a driver amplifier connected to the phase shifter and configured to boost the power of a phase-shifted RF signal received from the phase shifter; a power amplifier connected to the driver amplifier and configured to amplify a boosted phase-shifted RF signal received from the driver amplifier and generate a saturated RF signal, wherein the boosted phase-shifted RF signal saturates the power amplifier; a coupler connected to the power amplifier and configured to sample the saturated RF signal received from the power amplifier for monitoring the power of the saturated RF signal; a circulator connected to the coupler and configured to route the saturated RF signal received therefrom to an antenna for transmission; a termination device coupled to the circulator and configured to terminate reflected RF signals from the antenna; and a temperature sensor placed in the vicinity of the power amplifier and connected to the control unit, wherein the control unit is configured to monitor the temperature on the transmit channel based on a sensed temperature received from the temperature sensor.
[0008] In an embodiment, the transmitter includes a detector diode connected between the coupler and the control unit to convert the sampled saturated RF signal into an analog voltage to be fed to the control unit, and wherein the control unit is configured to determine health status of the saturated RF signal based on the analog voltage fed thereto.
[0009] In an embodiment, the predetermined level corresponds to a gain of the common amplifier required to drive the driver amplifier.
[0010] In an embodiment, the pulsing circuit includes a first switching circuit configured to generate a first pulse to operate the common amplifier, and wherein the control unit is configured to control the first switching circuit by providing thereto a first pulsing signal to enable the first switching circuit to generate the first pulse to be fed to the common amplifier.
[0011] In an embodiment, the pulsing circuit includes a second switching circuit configured to generate a second pulse to operate the driver amplifier and a third pulse to operate the power amplifier, and wherein the control unit is configured to control the second switching circuit by providing thereto, a second pulsing signal to enable the second switching circuit to generate the second pulse to be fed to the driver amplifier, and a third pulsing signal to enable the second switching circuit to generate the third pulse to be fed to the power amplifier.
[0012] In an embodiment, the second pulse is fed to a drain input of the driver amplifier, and the third pulse is fed to any one of a drain input or a gate input of the power amplifier.
[0013] In an embodiment, the transmitter is mounted on a multi-layer printed circuit board comprising: a first layer having the control unit, the pulsing circuit, the RF booster, the power splitter and the transmit channels mounted thereon; a second layer having reference ground line formed therein for the first layer; a third layer, a fourth layer, a fifth layer and a sixth layer in combination having power supply traces and power planes formed therein and routed to the first layer through a plurality of blind vias; and a seventh layer and an eight layer having ground lines formed therein for grounding the first to sixth layers through a plurality of ground vias.
[0014] In accordance with another exemplary implementation of the present invention there is provided, a method for transmitting X-band signal. The method comprises: receiving, by a radio frequency (RF) booster, an external RF signal and at least boosting the power of the external RF signal to a predetermined level; splitting, by a power splitter, a boosted RF signal into a plurality of equally powered RF signals; generating, by a pulsing circuit, a plurality of pulses for operating a plurality of transmit channels corresponding to the plurality of equally powered RF signals; controlling, by a control unit, the operation of the pulsing circuit, the RF booster and each transmit channel; and amplifying, by each transmit channel, the corresponding equally powered RF signal and transmitting amplified RF signal.
[0015] In an embodiment, the step of receiving the external RF signal includes: filtering, by a low pass filter, the external RF signal; attenuating, by an attenuator, the filtered RF signal; and amplifying, by a common amplifier, the attenuated RF signal and boosting the power of the attenuated RF signal to the predetermined level.
[0016] In an embodiment, the step of amplifying each equally powered RF signal includes: shifting, by a phase shifter, the phase of the equally powered RF signal; boosting, by a driver amplifier, the power of the phase-shifted RF signal; amplifying, by a power amplifier, the boosted phase-shifted RF signal and generating a saturated RF signal; sampling, by a coupler, the saturated RF signal for monitoring the power of the saturated RF signal; and routing, by a circulator, the saturated RF signal to an antenna for transmission.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0017] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.
[0018] Figure 1 illustrates a block diagram depicting a compact pulsed high-power X-band multi-channel transmitter, according to an exemplary implementation of the present invention.
[0019] Figure 2 illustrates a block diagram depicting a common section and single channel configuration of the multi-channel transmitter illustrated in Figure 1.
[0020] Figure 3 illustrates a schematic diagram depicting a layer stack-up for composite multilayer multi-channel transmitter Printed Circuit Board (PCB).
[0021] Figure 4 illustrates a schematic diagram depicting a surface mount technology (SMT) type power amplifier configuration and thermal considerations through the composite multilayer multi-channel transmitter PCB.
[0022] Figure 5 illustrates a perspective view depicting the compact pulsed high-power X-band multi-channel transmitter in packaged form.
[0023] Figure 6 illustrates a flowchart depicting the steps involved in a method for transmitting X-band signal implemented by the X-band multi-channel transmitter of figure 1.
[0024] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative methods embodying the principles of the present invention. Similarly, it will be appreciated that any flow charts, flow diagrams, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
DETAILED DESCRIPTION
[0025] The various embodiments of the present invention describe about a compact pulsed high-power X-band multi-channel transmitter (MCT) for radio wave analog beam forming networks. The MCT is realized as a single entity by integrating an array of MCTs forming a transmit array for beam forming in radio wave beam forming networks. The MCTs comprise multiple independent transmit modules (TMs), power supply and control circuits/units. The MCT is realized on a single composite multi-layer printed circuit board (PCB) which is enclosed in a mechanical housing.
[0026] In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of systems.
[0027] However, the invention is not limited to the specific embodiments described herein. Further, structures and devices shown in the figures are illustrative of exemplary embodiments of the present invention and are meant to avoid obscuring of the present invention.
[0028] It should be noted that the description merely illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present invention. Furthermore, all examples recited herein are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0029] Referring to figure 1, the block diagram of a compact pulsed high-power X-band multi-channel transmitter (MCT) (100), according to an exemplary implementation of the present invention, is illustrated. The MCT (100) operating in X-Band comprises a plurality of transmit channels or chains (105), a power splitter (104), a radio frequency (RF) booster (103), a pulsing circuit (102) and a control unit (101), as shown in figure 1. Each transmit channel/chain (105) is capable of generating high pulsed O/P power for various pulse widths and duty cycles. These plurality of independent transmit channel/chains (105) are having radio frequency (RF) input being fed from the 1:N power splitter (104), where N is number of transmit chain. In an exemplary embodiment, N=4 represents quad channel. The RF input to this splitter (104) is fed after boosting the RF signal received from an array controller (not particularly shown). The boost in RF signal to required power level is to compensate losses and it is achieved in the common chain RF booster (103).
[0030] The RF booster (103) is configured to receive an external RF signal from an external device i.e. the array controller and boost/increase the power of the external RF signal to a predetermined level based on the necessary power level required by succeeding RF stages. The power splitter (104) is connected to the RF booster (103) and is configured to split the boosted RF signal received from the RF booster (103) into a plurality of equally powered RF signals (N). The plurality of transmit channels/chains (N) (105) correspond to the plurality of equally powered RF signals. In an exemplary non-limiting embodiment as shown in figure 1, MCT comprises four (N=4) transmit channels/chains such that the boosted RF signals is split into a four equally powered RF signals. Each transmit channel/chain (105) is connected to a corresponding output of the power splitter (104) to receive therefrom an equally powered RF signal and is configured to at least amplify the equally powered RF signal and transmit the amplified RF signal. The pulsing circuit (102) is configured to generate a plurality of pulses for operation of the transmit channels (105), and the control unit (101) is configured to control the operation of the pulsing circuit (102), the RF booster (103) and each transmit channel (105).
[0031] The MCT (100) is realized on a single composite multi-layer printed circuit board (PCB) which is enclosed in a mechanical housing. The MCT operates on discrete power supplies (-5, +7, +3.3, +28V) being fed to the MCT from array controller using a Nano-D connector. Voltages required for the FPGA are derived using low-drop-out (LDO) regulators internally. Filtering capacitors have been incorporated on all the supply lines.
[0032] The MCT (100) operates in two modes namely, selective transmit mode and normal mode. An FPGA as the control unit (101) is used to control and monitor the mode of operation. The external interface for this comprises LVDS pairs that are rewarding in terms of low power operation and in mitigating the effects of noisy environment. Nano-D connector is used as the external interface for the MCT that carries the LVDS control lines, power supplies and JTAG lines. The accessibility of the JTAG lines from the external interface aids in reprogramming the MCT in the field.
[0033] The RF circuitry of the MCT (100) is divided into three sections, namely the common chain RF booster (103), power splitter (104) and transmit (Tx) chain (105). The detailed block diagram depicting these sections are shown in figure 2. During transmission the RF input power is fed through a RF connector blind mating with the array controller side. The connector is in-line with the RF transmission path. The RF signal initially passes through the common chain (103) consisting of a printed low pass filter (LPF) (201) to filter out unwanted spurious signals being fed from array controller. This is followed by an attenuator pad (202) to attenuate the filtered RF signal and a common amplifier (203) which amplifies the attenuated RF signal output from the attenuator (202) to boost the power of the attenuated RF signal to the predetermined level.
[0034] The pulsing circuit includes a first switching circuit (209) and a second switching circuit (210). The common amplifier (203) is GaAs based packaged amplifier and has provision to be operated in pulsed mode by aid of the first switching circuit (209) which generates a first pulse to operate the common amplifier (203). A first pulsing signal from the control unit (101) which is in the form of an FPGA (211), determined by pulse width and duty cycle, controls the first switching circuit (209) and enables it to generate the first pulse to be fed to the common amplifier (203).
[0035] The next section is the power splitter (104). The conditioned RF signal from common chain (103) is equally split using a Wilkinson based power splitter and fed to the plurality of transmit (Tx) channels (105). The divider is realized in printed form on a composite multi-layer PCB.
[0036] The third section is the Tx chain (105) wherein each channel comprises a phase shifter (204), a driver amplifier (205), a power amplifier (206), a coupler (207) and a circulator (212). The phase shifter (204) is typically a 6-bit type shifter controlled by the control unit (101) i.e. the FPFA (211), for providing necessary phase shift to the equally powered RF signal in each transmit chain (105) for beam forming in transmitter array. It is followed by the driver amplifier (205) which boosts the phase-shifted RF signal to a level necessary to saturate the power amplifier (206) which amplifies the boosted phase-shifted RF signal and generates a saturated RF signal. The saturated RF signal passes through the coupler (207) printed on the composite PCB and through the higher power circulator (212) before being sent to antenna for transmitting. The MCT has a RF connector blind mating on antenna side.
[0037] The phase shifter (204) and driver amplifier (205) are packaged GaAs devices. The driver amplifier (205) is also operated in pulsed mode by pulsing its drain input with aid of the second switching circuit (210) which generates a second pulse to operate the driver amplifier (205). A second pulsing signal from the control unit (101) / the FPGA (211), determined by pulse width and duty cycle, controls the second switching circuit (210) and enables it to generate the second pulse to operate the driver amplifier (205). The O/P of driver amplifier (205) is sufficient to saturate power amplifier (206). The power amplifier is GaN based and can be a packaged device or a MMIC die with flexibility to use a surface mount type. It has a provision for both gate and drain pulsing with aid of the second switching circuit (210) which generates a third pulse to operate the power amplifier (206). A third pulsing signal from the control unit (101) i.e. the FPGA (211), determined by pulse width and duty cycle, controls the second switching circuit (210) and enables it to generate the third pulse fed to, typically, the gate input of the power amplifier (206). The combination of the drain pulsing driver amplifier (205) and gate pulsing power amplifier (206) achieves fast switching. The generated saturated RF signal from the power amplifier (206) is sampled with the use of a directional coupler (207) and is converted into an analog voltage using a detector diode (214) to monitor the power levels of the saturated RF signal to be transmitted. This input is fed to the FPGA (211) indicating RF health status of the single channel of MCTM based on RF output power that is being generated.
[0038] Typically, the control unit (101) / FPGA (211) generates the first, second and third pulsing signals at precise moments whereby the first, second and third pulses are generated in a synchronized manner by the first and second switching circuits (209, 210).
[0039] The saturated RF signal finally gets routed by the higher power circulator (212) to the antenna port of the MCT. The circulator provides low loss in the clock-wise direction. It is attached to the mechanical housing and is bonded to the RF tracks. The antenna port connector mates with the antenna radiating elements. Any mismatch in antenna side will result in RF power reflecting back to circulator (212). These reflections can damage the power amplifier (206). Thus, a high power termination device (213) is provided which in combination with the circulator forms an isolator to provide any mismatch protection. The reflected power is absorbed by the high power termination device (213) coupled to the circulator (212) to protect the power amplifier (206). A temperature sensor (208) is placed close to the power amplifier (206), to monitor the temperature rise on MCT. The output is monitored by FPGA (211) for any undesirable temperature rise.
[0040] For the MCT to operate in different modes, all the active RF devices are pulsed with respect to an external transmit pulse. Fast turn on metal oxide semiconductor field effect transistor (MOSFET) are used for controlling high voltage supply. The timing of each of the control signals ensures that the transmit chain devices are switched on and off based on pulse width & pulse repetition time (PRT). One of the critical requisites for the operation of GaN based power amplifier is presence of the negative supply bias before the application of positive supply bias which is ensured by the FPGA.
[0041] The positive supply bias to the power amplifier (206) is pulsed by using a combination of high-speed MOSFET driver and FET. Based on the transmit pulse width, power droop and operating voltage, optimum value of the storage capacitor is arrived at. The positive biases to other active devices in transmit chain are pulsed using high performance, low voltage, analog switches. The digital phase shifter (204) takes controls from the FPGA (211).
[0042] All the above mentioned functionalities/components are realized on a single composite multi-layer printed circuit board (PCB) whose stack up is illustrated in figure 3. First layer (301) is designed on dielectric laminate (309) for realization of both RF and digital circuitry. The said second layer (302) acts as reference ground for first layer for superior RF performance. The third layer (303), fourth layer (304), fifth layer (305) and sixth layer (306) are designed for realization of power supply and control distribution and are routed to RF and digital circuitry in first layer (301) with aid of plurality of signal vias (312) realized as blind vias, and also by realization of power planes wherever feasible to distribute high currents. The seventh layer (307) and eight layer (308) are designed as complete ground layers connecting all RF and digital ground references for superior performance. Economically viable dielectric laminate (311) is used for routing digital supply and control traces in inner layers of composite PCB and are bonded together with aid of bonding film (310). Bonding film (310) also aids in binding dielectric laminate (309) with dielectric laminate (311). Plurality of plated through ground vias (313) are stitched to all layers for providing a common ground reference between layers. The entire PCB is attached to the mechanical housing by epoxy for ensuring uniform RF and supply grounding.
[0043] As shown in figure 4, the complexity of having a surface mount GaN power amplifier (403) on a composite multi-layer printed circuit board (402) is regarding the heat dissipation that is generated by the power amplifier while in operation. Also, proper RF grounding of the power amplifier ensures optimum performance. Hence plurality of ground vias are provided in composite multi-layer printed circuit board (402) underneath the power amplifier (403) as indicated in (404) for providing minimum resistance and inductance between power amplifier (403) and mechanical enclosure (401). This aids in efficient heat transfer and optimum RF performance. The heat zones are indicated in (405) of figure 4.
[0044] The complete assembled MCT is shown in figure 5. The MCT is hermetically sealed suited for applications where external environment does not impair its performance when exposed. The peripheral walls of the MCT have been minimized to achieve the compact form-factor. The RF channels of the TMs and the internal walls are appropriately designed to mitigate cavity resonance & unwelcome feedback. Aluminum material with appropriate plating has been used to combat environmental corrosion.
[0045] The operational aspects of the compact pulsed high-power X-band multi-channel transmitter for radio wave analog beam forming networks, as disclosed herein, gives rise to a corresponding method for transmitting X-band signal as illustrated in figure 6. The method is implemented by the X-band multi-channel transmitter (100). The method comprises: at step 602 - receiving, by a radio frequency (RF) booster (103), an external RF signal and at least boosting the power of the external RF signal to a predetermined level; at step 604 - splitting, by a power splitter (104), a boosted RF signal into a plurality of equally powered RF signals; at step 606 - generating, by a pulsing circuit (102), a plurality of pulses for operating a plurality of transmit channels (105) corresponding to the plurality of equally powered RF signals; at step 608 - controlling, by a control unit (101), the operation of the pulsing circuit (102), the RF booster (103) and each transmit channel (105); and at step 610 - amplifying, by each transmit channel (105), the corresponding equally powered RF signal and transmitting amplified RF signal.
[0046] In accordance with the method, the step of receiving the external RF signal includes: filtering, by a low pass filter (201), the external RF signal; attenuating, by an attenuator (202), the filtered RF signal; and amplifying, by a common amplifier (203), the attenuated RF signal and boosting the power of the attenuated RF signal to the predetermined level.
[0047] In accordance with the method, the step of amplifying each equally powered RF signal includes: shifting, by a phase shifter (204), the phase of the equally powered RF signal; boosting, by a driver amplifier (205), the power of the phase-shifted RF signal; amplifying, by a power amplifier (206), the boosted phase-shifted RF signal and generating a saturated RF signal; sampling, by a coupler (207), the saturated RF signal for monitoring the power of the saturated RF signal; and routing, by a circulator (212), the saturated RF signal to an antenna for transmission.
[0048] Typically, upon receiving the external RF signal, the control unit (101) / FPGA (211) starts controlling the operation of the phase shifter (204) and the pulsing circuit (102) i.e. the first and second switching circuits (209, 210) such that the first, second and third pulses are generated in a synchronized manner at precise moments as the signal routes through the transmitter (100) to achieve the phase-shifting of the equally powered RF signal by the phase shifter (204), amplification of the attenuated RF signal by the common amplifier (203), the boosting of the power of the phase-shifted RF signal by the driver amplifier (205), and the amplification of the boosted phase-shifted RF signal and generation of the saturated RF signal by the power amplifier (206). At the same time, the control unit (101) / FPGA (211) also monitors the output of the detector diode (214) to monitor the power levels of the saturated RF signal as well as the temperature sensed by the temperature sensor (208) to deploy any protection mechanism in each transmit channel (105) if the RF health status is outside a predetermined range.
[0049] The MCT as disclosed herein operates on discrete supplies and low voltage differential signal (LVDS) interface is used for communicating with the up-stream systems. For LVDS interface and to obtain fast switching for transmit operation the FPGA based control circuitry is used. Power amplifier is GaN based and operated using gate pulsing method with provision for amplifier supply protection. Common amplifier and driver amplifiers are also pulsed as described above. Pulsing of supplies of the active RF devices improves overall module efficiency as compared to only RF pulsing. Phase shifters are used to control phase of RF signal necessary for beam forming application of entire transmit array. Majority of components are surface mount which eases the assembly.
[0050] The MCT is realized on a single composite multi-layer printed circuit board with blind vertical interconnects and is enclosed in a mechanical housing. Each transmit chain is capable of providing 25W (min) peak pulsed power for pulse widths 0.03 to 100 µsecs and for duty cycles up to 20%. Operation of the MCT typically covers 10% BW of the center frequency. Additionally, it offers fast switching operation with RF rise and fall time typically being <15nsec with gate pulsing. Overall efficiency is >20%, which being crucial specification for array design.
[0051] The power supply and pulsing circuitry comprises regulators, MOSFETS, analog switches and filtering capacitors. Regulators are used to condition some of the input voltages to the required voltages. Gate pulsing of power amplifier is by use of analog switch which is switching between negative voltages that result in the power amplifier to be in cut off mode or in active operation mode. A provision for drain sequencing of the power amplifier with aid of power MOSFETS for supply sequencing is also incorporated as a protection mechanism. Drain supply of common amplifier and driver amplifiers are pulsed by use of analog switch in order to aid in achieving optimum efficiency at system level. Tantalum based capacitor having low effective series resistance (ESR) and its proper placement provides the instantaneous supply current for power amplifiers. Placing 25% of total charge storage capacitance close to power amplifier mitigates ringing and ensures droop of less than 1dB operating at conditions. The MCT is protected from over temperature by monitoring temperature and shutting of supply. The MCT is protected from large ON time and large ON/OFF ratio of the power amplifier to limit thermal rundown and thereby increasing the reliability of the MCT.
[0052] The FPGA based circuit comprises inbuilt analog to digital converters and flash memory, and is used for controlling and monitoring based on the commands received from an external up-stream system. The external interface is LVDS. The FPGA decodes the received commands from external systems and the important functionalities of the FPGA are turning ON and OFF the active devices in chain based on pulse width and duty cycle, set phase bits and monitor voltage, RF coupled power and temperature.
[0053] Low thermal resistance in small form factor to transfer heat generated by high power devices is achieved by judiciously planning RF layout and optimum placement of ground vias close to hot spots. The composite PCB design topology comprises composite layer stack with a dielectric laminate (least dielectric constant and suited for RF designs) realizing RF circuitry on first layer and reference ground to it in second layer for superior RF performance. Other layers realized on an economically viable dielectric laminate for routing & distribution of digital power supply & control signals. The board consists of plurality of signal vias connecting all relevant signals and are realized as blind vias. The board also consists plurality of ground vias that stitch ground references of all layers and are realized as through vias. Realization of power planes in inner layers and plurality of signal vias to connect power supply aids in carrying high current with minimum resistances offered. Judiciously laying out the pulsing circuit close to amplifiers and designing power planes for drain connection across power amplifiers along with plurality of signal vias aids in realizing designs with minimum parasitic and superior switching operations.
[0054] In an exemplary embodiment, the MCT is realized for Quad channel (4-channels) in compact form factor measuring 100 mm in length, 66.4 mm in width and 8.6 mm in height has been realized weighing 103 gms. The MCT uses a vertical PCB mount Nano-D connector for power supply and controls. The thickness of composite multilayer PCB is optimized in such a way that it can be inserted between the dual row connector pins and soldered as surface mount, which being the key to achieve optimum module thickness. RF signal is brought in and brought out of MCT with use of sub miniature push-on (SMP) connectors. This complete arrangement provides flexibility for blind mating.
[0055] In an embodiment, the array controller includes plank controller, MCT and the antenna elements are arranged on same plane. MCT blind mates with plank controller with SMP connector (smooth bore type) for RF signal and Nano-D connector for power supply and controls. Each transmit arm of MCT blind mates with antenna elements on other side of same plane with aid of SMP connectors (limited detent type).
[0056] An array of MCTs are integrated for realizing a radio wave analog beam forming network. One of the key advantages of such an active transmit array is that there is no single point of failure and the system continues to operate with graceful degradation, thus enhancing the reliability of the system. Further, advantageously, the operation of the MCT is in X-band and can be extended to other bands too with a greater number of channels.
[0057] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.

,CLAIMS:WE CLAIM:
1. An X-band multi-channel transmitter comprising:
a radio frequency (RF) booster (103) configured to receive an external RF signal from an external device and at least boost the power of said external RF signal to a predetermined level;
a power splitter (104) connected to said RF booster (103) and configured to split a boosted RF signal received therefrom into a plurality of equally powered RF signals;
a plurality of transmit channels (105) corresponding to the plurality of equally powered RF signals, each transmit channel connected to an output of said power splitter (104) and configured to at least amplify an equally powered RF signal received therefrom and transmit the amplified RF signal;
a pulsing circuit (102) configured to generate a plurality of pulses for operation of said transmit channels (105); and
a control unit (101) configured to control the operation of said pulsing circuit (102), said RF booster (103) and each of said transmit channels (105).

2. The transmitter as claimed in claim 1, wherein said RF booster comprises:
a low pass filter (LPF) (201) configured to filter said external RF signal;
an attenuator (202) connected to said LPF (201) and configured to attenuate a filtered RF signal received therefrom;
a common amplifier (203) connected to said attenuator (201) and configured to amplify an attenuated RF signal received from said attenuator (202) to boost the power of the attenuated RF signal to said predetermined level.

3. The transmitter as claimed in claim 1, wherein each transmit channel (105) comprises:
a phase shifter (204) configured to shift the phase of the equally powered RF signal;
a driver amplifier (205) connected to said phase shifter (204) and configured to boost the power of a phase-shifted RF signal received from said phase shifter (204);
a power amplifier (206) connected to said driver amplifier (205) and configured to amplify a boosted phase-shifted RF signal received from said driver amplifier (205) and generate a saturated RF signal, wherein the boosted phase-shifted RF signal saturates said power amplifier (206);
a coupler (207) connected to said power amplifier (206) and configured to sample the saturated RF signal received from said coupler (207) for monitoring the power of the saturated RF signal;
a circulator (212) connected to said coupler and configured to route the saturated RF signal received therefrom to an antenna for transmission;
a termination device (213) coupled to said circulator (212) and configured to terminate reflected RF signals from said antenna; and
a temperature sensor (208) placed in the vicinity of said power amplifier (206) and connected to said control unit (101), wherein said control unit (101) is configured to monitor the temperature on the transmit channel based on a sensed temperature received from said temperature sensor (208).

4. The transmitter as claimed in claims 1 to 3, wherein the transmitter includes a detector diode (214) connected between said coupler (207) and said control unit (101) to convert the sampled saturated RF signal into an analog voltage to be fed to said control unit (101), and
wherein said control unit (101) is configured to determine health status of the saturated RF signal based on the analog voltage fed thereto.

5. The transmitter as claimed in claims 1 to 3, wherein said predetermined level corresponds to a gain of said common amplifier (203) required to drive said driver amplifier (205).

6. The transmitter as claimed in claims 1 to 3, wherein said pulsing circuit includes a first switching circuit (209) configured to generate a first pulse to operate said common amplifier (203), and
wherein said control unit (101) is configured to control said first switching circuit (209) by providing thereto a first pulsing signal to enable said first switching circuit (209) to generate the first pulse to be fed to said common amplifier (203).

7. The transmitter as claimed in claims 1 to 3, wherein said pulsing circuit includes a second switching circuit (210) configured to generate a second pulse to operate said driver amplifier (205) and a third pulse to operate said power amplifier (206), and
wherein said control unit (101) is configured to control said second switching circuit (210) by providing thereto,
a second pulsing signal to enable said second switching circuit (209) to generate the second pulse to be fed to said driver amplifier (205), and
a third pulsing signal to enable said second switching circuit (209) to generate the third pulse to be fed to said power amplifier (206).

8. The transmitter as claimed in claim 7, wherein the second pulse is fed to a drain input of said driver amplifier (205), and the third pulse is fed to any one of a drain input or a gate input of said power amplifier (206).

9. The transmitter as claimed in claims 1 to 8, wherein said transmitter is mounted on a multi-layer printed circuit board comprising:
a first layer (301) having said control unit (101), said pulsing circuit (102), said RF booster (103), said power splitter (104) and said transmit channels (105) mounted thereon;
a second layer (302) having reference ground line formed therein for said first layer (301);
a third layer (303), a fourth layer (304), a fifth layer (305) and a sixth layer (306) in combination having power supply traces and power planes formed therein and routed to said first layer (301) through a plurality of blind vias (312); and
a seventh layer (307) and an eight layer (308) having ground lines formed therein for grounding said first to sixth layers (301-306) through a plurality of ground vias (313).

10. A method for transmitting X-band signal, the method comprising:
receiving, by a radio frequency (RF) booster (103), an external RF signal and at least boosting the power of the external RF signal to a predetermined level;
splitting, by a power splitter (104), a boosted RF signal into a plurality of equally powered RF signals;
generating, by a pulsing circuit (102), a plurality of pulses for operating a plurality of transmit channels (105) corresponding to the plurality of equally powered RF signals;
controlling, by a control unit (101), the operation of the pulsing circuit (102), the RF booster (103) and each transmit channel (105); and
amplifying, by each transmit channel (105), the corresponding equally powered RF signal and transmitting amplified RF signal.

11. The method as claimed in claim 10, wherein the step of receiving the external RF signal includes:
filtering, by a low pass filter (201), the external RF signal;
attenuating, by an attenuator (202), the filtered RF signal; and
amplifying, by a common amplifier (203), the attenuated RF signal and boosting the power of the attenuated RF signal to the predetermined level.

12. The method as claimed in claim 10, wherein the step of amplifying each equally powered RF signal includes:
shifting, by a phase shifter (204), the phase of the equally powered RF signal;
boosting, by a driver amplifier (205), the power of the phase-shifted RF signal;
amplifying, by a power amplifier (206), the boosted phase-shifted RF signal and generating a saturated RF signal;
sampling, by a coupler (207), the saturated RF signal for monitoring the power of the saturated RF signal; and
routing, by a circulator (212), the saturated RF signal to an antenna for transmission.
Dated this 29th day of March, 2019

FOR BHARAT ELECTRONICS LIMITED
By their Agent)
(D. MANOJ KUMAR IN/PA-2110)
KRISHNA & SAURASTRI ASSOCIATES LLP