FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules  2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

“Multi-Channel Broadband Re-configurable RF Front End for Software Defined Radio / Cognitive Radio”

APPLICANTS:

Name : HCL Technologies Limited

Nationality : Indian

Address : HCL Technologies Ltd.  50-53 Greams Road  Chennai – 600006  Tamil Nadu  India.

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[001] This invention relates to radio frequency front-end design more particularly to a Multi-channel broadband re-configurable RF Front End for Software Defined Radio and Cognitive Radio.

BACKGROUND OF INVENTION
[002] Studies conducted by regulatory bodies in various countries have revealed that most of the radio frequency spectrum is inefficiently utilized. Allocation of fixed spectrum (assigned to specific services) prevents rarely used frequencies from being used by unlicensed users  even when there is no threat of interference at all with any of the assigned services
[003] Advances in the wireless technology along with the development of analog and digital electronics have led to the emergence of wide range of wireless and radio access technologies. There is a huge demand for the availability of spectrum with the increased number of applications in the wireless communications space. With the existing radio frequency spectrum  being pushed to its boundaries there is a limitation on the spectrum availability.
[004] To address spectrum scarcity issue and to satisfy the increased demand of applications new methods are needed for efficient and intelligent use of spectrum.
[005] Wireless communication systems like cognitive radios are working towards allowing the wide frequency spectrum to be shared thus enabling efficient radio spectrum utilization. Cognitive radio devices use dynamic spectrum management system and can identify available/idle frequencies / frequency bands the spectrum that can be used for communications. Multiple cognitive radio systems generally share information to find vacant spectrum bands.
[006] For cognitive radios to succeed  it is essential that they must be software defined  capable of operating on a broader frequency range  have better interference management  strong spectrum sensing and also have re-configurability in terms of operating parameters like frequency  input/output power  receiver sensitivity  bandwidth and so on based on the radio environment. Broad frequency range of operation (for spectrum sensing  interference management and communication) and reconfigurabilty of operating parameters depends on the design of the RF front end.

OBJECT OF INVENTION
[007] The principal object of this invention is to provide a Multi-channel broadband re-configurable RF Front End improving reliability of cognitive radio systems.
[008] Another object of the invention is to ensure that the Multi-channel broadband re-configurable RF Front End is capable of operating over a broad frequency range and is capable of re-configuring operating parameters based on the requirement of the existing radio environment.

STATEMENT OF INVENTION
[009] Accordingly  the invention provides a multichannel broadband re-configurable RF front-end system for software-defined radios / cognitive radios with multiple channels operating on broad frequency range. Each transceiver channel is capable of performing transmitter function and/or receiver function. Each channel contains an RF transmitter  a RF receiver  a control and monitoring section  and a reference switching section  a Transmit/Receiver switch and a power supply and conditioning circuit. The RF transmitter up converts baseband signal to a RF signal. The RF receiver converts the received RF signal from antenna in to the baseband signal using double/dual conversion. One receiver of one transceiver channel is dedicated for sensing of spectrum holes if used for cognitive radio application. Each transceiver channel is reconfigurable across a range of operating parameters. The parameters are reconfigured using a control and monitoring section  which has controller for sending and receiving reconfiguration information. The reference switching section provides said reference frequency-to-frequency synthesizers in channel. A Transmit/Receiver switch is used to operate / perform a channel in TDD or FDD mode of operation.
[0010] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood  however  that the following descriptions  while indicating preferred embodiments and numerous specific details thereof  are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof  and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[0011] This invention is illustrated in the accompanying drawings  throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings  in which:
[0012] FIG. 1 illustrates a block diagram of multichannel broadband reconfigurable RF front end  according to the embodiments as disclosed herein;
[0013] FIG. 2 is a block diagram of receiver section in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein;
[0014] FIG. 3 is a block diagram of transmitter section in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein;
[0015] FIG. 4 is a block diagram of the local oscillator section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein;
[0016] FIG. 5 is a block diagram of the reference section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein; and
[0017] FIG. 6 is a block diagram of the control and monitoring section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein.

DETAILED DESCRIPTION OF INVENTION
[0018] The embodiments herein  the various features  and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly  the examples should not be construed as limiting the scope of the embodiments herein.
[0019] Referring now to the drawings  and more particularly to FIGS. 1 through 6  where similar reference characters denote corresponding features consistently throughout the figures  there are shown preferred embodiments.
[0020] FIG. 1 illustrates a block diagram of multichannel broadband reconfigurable RF front end  according to the embodiments as disclosed herein. The Multi Channel Broadband Reconfigurable RF Front End consists of the multiple channels and consists of RF receivers (down converters) 102  RF Transmitters (Up converters) 101  control and Monitoring Section (Controller) 104  Optional Internal Reference (105)  reference switching section 106  Tx/Rx switches 108 and power supply / power supply and conditioning circuitry 107.
[0021] Each channel can operate from 400MHz to 6000MHz. Each channel comprises of RF- transmitter 101/up converter  RF receiver 102/ down converter  master controller 104 and its associated circuitry. Each channel will get a common reference from reference and switching circuitry 106. The reference could be internally generated through internal reference 105 or can be externally supplied. Each broadband RF transceiver channel is connected to broadband antennas through TX/RX switch 108. Depending on the position of the TX/RX switch 108  the channel works at the TDD (Time Division Duplex) mode or FDD (Frequency Division Duplex) mode. The selection of the operating mode is controlled from the baseband unit. The individual blocks of the system are powered by power supply and conditioning circuitry 107. In the multichannel RF front end  one receiver in one channel works as a “sensing channel” for sensing the environment and other channels are used for the communication at broad frequency range. Although in figure 1 only depicted four channels and associated control section is depicted in practice it but can be applied to multiple channels (more than 4). The RF receiver 102 and RF transmitter 101 contains appropriate modulators  demodulators  local oscillators and so on for operation.
[0022] FIG. 2 is a block diagram of receiver section in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein. . The broadband  reconfigurable RF receiver comprises of two quadrature demodulators 201  broadband local oscillator circuitry 202  fixed frequency local oscillator circuitry206  low noise amplifiers 205  RF variable attenuators  RF Power detection circuitry 203  and control and monitoring circuitry (not shown in figure). The received signal from antenna is fed to the broadband re-configurable RF receiver. The receiver can work at the TDD (Time Division Duplex) mode or FDD (Frequency Division Duplex) mode using the switch as shown in figure 2. The broadband re-configurable RF receiver provides the appropriate amplification to the input signal; using the low noise amplifier 205  gain blocks and digital attenuators. Amplified input signal is down converted into baseband signal using dual conversion. During reception  to avoid the desensitization of receiver  received RF signal in the range 400MHz to 6000MHz is first down converted into 70MHz I/Q signal. The local oscillator frequency is generated by the synthesizer circuitry. Two different synthesizers are used in the receiver. Two LO signals are sent to the two different demodulators. At first conversion  the quadrature demodulator 201 converts the input RF frequency signal into First IF (say 70MHz signal). At second conversion  the first IF is further down converted into zero IF or low IF signal (say 0MHz to 22 MHz) using another quadrature demodulator 207. Local oscillator signals for the first quadrature demodulator 201 (First LO) are generated using broadband LO circuitry 202. The local oscillator signal for the second quadrature modulator 207 (Second LO) is constant/fixed frequency and generated by fixed frequency LO circuitry 206. Multiple power detection circuitry are used for precise power detection and thus for precise automatic gain control (AGC). The power detection circuitry 203 comprising an ultra high bandwidth  high directivity coupler and power detector. The reference signal required for generating the local oscillator signals is provided using reference generating circuitry. The controlling and re-configuring are done by the control and monitoring circuitry. The re-configurability in terms of operating frequency is provided by changing the Local oscillator signal (from the broadband local oscillator circuitry  First LO 202) to the quadrature demodulator 201. The frequency is re-configurable or changeable in precise steps (say in the order of 100 KHz). The re-configurability in terms of input power dynamic range is provided by selecting the appropriate amplification path (out of the four (N) paths) using automatic gain control (AGC) mechanism. The receiver is re-configurable / changeable to the input power level in precise steps (say in the order of 1dB). The receiver can operate over a broad frequency range (say from 400MHz to 6000MHz) and can support broad input power dynamic range (say average input power from -80dBm to +0dBm). The receiver is reconfigurable to any frequency within the frequency range of operation and can be configured to any input power within the input power dynamic range. The receiver section has been described in patent application 2433/CHE/2012.
[0023] FIG. 3 is a block diagram of transmitter section in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein. The transmitter unit is implemented based on direct conversion architecture. The broadband  reconfigurable RF transmitter comprises of quadrature modulator 301  broadband local oscillator circuitry 302  RF amplifiers  RF variable attenuators  RF Power detection circuitry 303  and control and monitoring circuitry. The baseband signal with Q channels and I is fed to the wideband quadrature modulator 301. The local oscillator signal for the quadrature modulator 301 is generated using broadband Local oscillator circuitry 302. The low power RF signal generated by quadrature modulator 301 is subjected to required amplification and attenuation 305 and filtered 304 to provide the required output power. The re-configurability in terms of operating frequency is provided by changing the local oscillator signal (from the broadband local oscillator circuitry 302) to the quadrature modulator 301. The re-configurability in terms of output power is provided by selecting the appropriate amplification path (out of the three (N) paths) and appropriate DVA settings in the corresponding path. The frequency is re-configurable or changeable in precise steps (say in the order of 100 KHz). The output power is re-configurable and changeable in precise steps (say in the order of 1dB). Multiple power detection sections are used for precise power detection and thus for precise automatic power control (APC) and Automatic Gain Control (AGC) with precise output power level. Plurality of power detection circuitry is placed into the chain. Multiple power detection circuits output signal sends to the controller  where it is matches with desired output signal power level  by which can get accurate and precise output power. The power detection circuitry 303comprising an ultra high bandwidth  high directivity coupler and power detector. The reference signal required for generating the local oscillator signal is provided using reference generating circuitry. The controlling and re-configuring are done by the control and monitoring circuitry. The channel can also work at the TDD (Time Division Duplex) mode or FDD (Frequency Division Duplex) mode using the switch as shown in figure 3. The detailed description of the transmitter is provided in 2434/CHE/2012  the description of which is included herein by reference.
[0024] FIG. 4 is a block diagram of the broadband local oscillator section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein. In each channel  two broadband local oscillators are used; wherein one LO is present in the RF transmitter 101 and the second LO is present in the RF receiver 102. The receiver also comprises of a fixed frequency oscillator for down conversion of received signal. A frequency synthesizer 401 is used to produce the desired range of frequencies. Reference frequency generated by the reference generating section is for the frequency synthesizer 401. Synthesizer 401 receives commands from the control and monitoring circuitry and accordingly generates a broadband local oscillator frequency. To achieve the broadband operation  the LO section comprises two frequency selection paths. The path 1 is to generate the portion of the entire frequency range that the frequency synthesizer could support. The path 2 comprises a frequency multiplier to cover the remaining portion of the frequency range and that the frequency synthesizer could not support. Appropriate amplification and filtering is provided in both paths to achieve required LO power level and with adequate harmonic rejection. Appropriate path will be selected using RF switches  which receives the commands from control and monitoring circuitry. The detailed description of the LO is provided in 2433/CHE/2012 and 2434/CHE/2012  the description of which are included herein by reference.
[0025] FIG. 5 is a block diagram of the reference section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein. The reference section produces the required reference signal for the frequency synthesizer in the RF receiver 102 and RF transmitter 101 for all the channels to produce the corresponding LO signal. The reference section produces the number of coherent signals say at 10MHz frequency. The reference section provides the coherent reference signals using clock buffers 503 to all synthesizers in the RF front-end unit and to the other section modules (like baseband unit) for synchronization purpose. By default  the system operates with internal reference frequency 501 that is generated by the TCXO / OCXO. In the presence of the external reference frequency 502 of say 10MHz with adequate power level internal reference will be switched off and external reference is given to all frequency synthesizers in transmitter as well as in receiver section.
[0026] FIG. 6 is a block diagram of the control and monitoring section used in a multichannel broadband reconfigurable RF front end  according to the embodiments disclosed herein. The control and monitoring section reports the health status of the RF transmitter to the base band unit. The control and monitoring interface section contains a microcontroller 600 and its associated circuitry.
[0027] . The baseband unit sends commands  like frequency setting  attenuation setting  to the controller section (Master controller) of the RF Frontend. The Control section processes it and modifies it suitably according to the up convertor 601 and down converters 602 and then sends it to the controllers (slave controllers) in the respective Tx and Rx. The slave controllers could have direct interface to the baseband unit also. This master controller 600 receives instruction from the baseband unit (BBU) through an interface (say SPI) for a required frequency (within the frequency range of operation) and required output power (within the output power dynamic range) for each channel.
[0028] The RF front end can suitably work in receiver mode for say -80dBm to 0dBm average input power and in transmit mode for say -70dBm to +10dBm average output power. The RF front end can suitably be used up to 12dB crest factor signal. The multichannel broadband reconfigurable RF front end is well suited for cognitive application: with multiple channels  with broadband nature of front end  plurality of communication standards can be supported and with re-configurability of variable power levels and frequency range can be supported.
[0029] 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 practiced with modification within the spirit and scope of the embodiments as described herein.

STATEMENT OF CLAIMS
We Claim 

1. A multichannel broadband re-configurable RF front end system for software defined radios / cognitive radios with multiple channels operating on broad frequency range wherein each channel comprises of
a RF transmitter for (Upconverting) converting baseband signal to a RF signal;
a RF receiver for (Downconverting) converting said RF signal from antenna in to the baseband signal using double/dual conversion;
a control and monitoring section with a controller for receiving sending signals for re-configuring said channel;
a reference switching section for providing said reference frequency to frequency synthesizers in channels;
a Transmit/Receiver switch to operate / perform a channel in TDD or FDD mode of operation and
a power supply and conditioning circuit.
2. The multichannel broadband re-configurable RF front end system  wherein each transceiver channel is capable of performing transmitter function and/or receiver function.
3. The multichannel broadband re-configurable RF front end system  wherein one receiver of one transceiver channel is dedicated for sensing of spectrum holes if used for cognitive radio application.
4. The multichannel broadband re-configurable RF front end system  wherein the multiple channels increasing the reliability of the system. (like implementation of the MIMO).
5. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each transceiver channel can operate at a broad frequency range of 400 MHz till 6000 MHz
6. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each transceiver channel has 80 dB of input power dynamic range for receiver and 80dB of output power dynamic range for transmitter.
7. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each transceiver channel is reconfigurable across a range of operating parameters.
8. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each transceiver channel is reconfigurable across the frequency range from 400 MHz to 6000 MHz.
9. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each receiver in each transceiver channel is independently reconfigurable across input power dynamic range from -80 dBm to +0dBm.
10. The multichannel broadband re-configurable RF front end system  as claimed in claim 1  wherein each transmitter in each transceiver channel is independently reconfigurable the output power dynamic range from -70dBm to +10dBm.

Dated: 27th day of July 2012 Signature:
Dr Kalyan Chakravarthy
(Patent Agent)


ABSTRACT
Multi-channel broadband re-configurable RF Front End for Software Defined Radio / Cognitive Radio. The RF front end helps improve spectrum sensing for better spectrum utilization. The RF front end comprising of multiple channels of reconfigurable transmitters and receivers  Tx/Rx switch  reference section  control section and power section is described. The RF front-end transceiver comprises of multiple channels and adapts its parameters based on the radio environment. The RF front end works on wide bandwidth and reconfigures its parameters.

FIG. 1