Patent Publication Number: US-8971421-B2

Title: Milli-meter-wave-wireless-interconnect (M2W2-interconnect) method for short-range communications with ultra-high data rate capability

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation under 35 U.S.C. Section 120 of co-pending and commonly-assigned: 
     U.S. Utility patent application Ser. No. 13/377,124, filed on Dec. 8, 2011, by Sai-Wang Tam and Mau-Chung F. Chang, entitled “MILLI-METER-WAVE-WIRELESS-INTERCONNECT (M2W2-INTERCONNECT) METHOD FOR SHORT-RANGE COMMUNICATIONS WITH ULTRA-HIGH DATA RATE CAPABILITY,”, which application claims the benefit under 35 U.S.C. Section 365(c) of co-pending and commonly-assigned: 
     P.C.T. International Patent Application Serial No. PCT/US2010/038033, filed on Jun. 9, 2010, by Sai-Wang Tam and Mau-Chung F. Chang, entitled “MILLI-METER-WAVE-WIRELESS-INTERCONNECT (M2W2-INTERCONNECT) METHOD FOR SHORT-RANGE COMMUNICATIONS WITH ULTRA-HIGH DATA RATE CAPABILITY,”, which application claims the benefit under 35 U.S.C. Section 119(e) of commonly-assigned: 
     U.S. Provisional Patent Application Ser. No. 61/185,946, filed on Jun. 10, 2009, by Sai-Wang Tam and Mau-Chung F. Chang, entitled “MILLI-METER-WAVE-WIRELESS-INTERCONNECT (M2W2-INTERCONNECT) METHOD FOR SHORT-RANGE COMMUNICATIONS WITH ULTRA-HIGH DATA RATE CAPABILITY,”, 
     all of which applications are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a millimeter wave wireless (M2W2) interconnect method for short range communications with ultra-high data rate capability. 
     2. Description of the Related Art 
     (Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.) 
     On-chip interconnects, especially for multi-processor chips and network-on-a-chip, have been projected as the limiting factor in terms of bandwidth, power and latency. However, on-chip interconnects remain non-scalable and non-reconfigurable. 
     In previous work [1], an on-chip antenna was used for wireless data transmission with distance of 1 m or above. However, this on-chip antenna required the use of a phase and frequency synchronous modulation scheme, such as binary phase-shifted-keying (BPSK), which increased the complexity of the architecture and overall power consumption. 
     Thus, there is a need in the art for improved methods of wireless data transmission. The present invention satisfies that need. 
     SUMMARY OF THE INVENTION 
     To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a millimeter wave wireless (M2W2) interconnect for transmitting and receiving signals at millimeter-wave frequencies for short-range wireless communication with high data rate capability, wherein the M2W2 interconnect is used with asynchronous modulation and differential signaling. 
     The M2W2 interconnect includes a transmitter for modulating a millimeter-wave carrier signal with an input data stream, wherein the modulated millimeter-wave carrier signal is amplified and then fed to a transmitter antenna and radiated. The M2W2 interconnect also includes a receiver for receiving the radiated millimeter-wave carrier signal at a receiver antenna, for amplifying the received millimeter-wave carrier signal, and for converting the amplified millimeter-wave carrier signal by demodulation to a full swing digital signal as an output data stream. 
     A differential-mutual-mixer in the receiver acts as an envelope detector and carrier removal is used to demodulate the millimeter-wave carrier signal to a base-band signal, wherein the base-band signal is amplified to the full swing digital signal. 
     The transmitter and receiver antennae may comprise an on-chip differential dipole antenna or a bond-wire dipole antenna. The bond wire dipole antenna is comprised of a pair of bond wires connecting between a pair of pads on an integrated circuit (IC) die and a pair of floating pads on a printed circuit board (PCB). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  is a schematic of a single channel wireless radio frequency interconnect (RF-I) using an on-chip antenna. 
         FIG. 2  is a schematic of a single channel wireless RF-I using a pair of bond wires as an antenna. 
         FIG. 3A  is a schematic of a transmitter with an on-chip differential dipole antenna. 
         FIG. 3B  comprises two graphs, wherein an upper graph shows the input data of an amplitude shift-keying (ASK) modulator and a lower graph shows the output data of the ASK modulator. 
         FIG. 4  is a layout of a transmitter with an on-chip differential dipole antenna. 
         FIGS. 5A-D  illustrate a pair of bond wires as a dipole antenna, wherein  FIG. 5A  is a top view,  FIG. 5B  is a side view,  FIG. 5C  is a cross-section view and  FIG. 5D  is a three dimensional perspective view. 
         FIG. 6A  is a schematic of a receiver with an on-chip dipole antenna. 
         FIG. 6B  comprises three graphs, wherein a upper graph shows the on-chip antenna first receiving a weak ASK signal, the middle graph shows the low noise amplifier amplifying the ASK signal so that that the self-mixer can demodulate the modulated signal to a base-band digital signal, as shown in the lower graph. 
         FIG. 7  is a layout of a receiver with an on-chip dipole antenna. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Technical Disclosure 
     The present invention comprises a wireless interconnect for transmitting and receiving signals at specified frequencies for short-range communication with high data rate capability, comprising the M2W2 interconnect, where the specified frequencies are millimeter-wave frequencies, using an asynchronous modulation scheme and differential signaling architecture. The M2W2 interconnect transmits data wirelessly, in contrast to previous implementations of RF-I (radio frequency interconnects) that utilize a controlled-impedance transmission medium [2]. Moreover, the specified frequencies used with the M2W2 interconnect may be transmitted concurrently in a plurality of different frequency bands to implement multiple parallel communication links. 
     The present invention describes a transmitter for modulating a millimeter-wave carrier signal with an input data stream, wherein the modulated carrier signal is further amplified to a higher power level and then fed to a transmitter antenna that radiates the modulated carrier signal. The present invention also describes a receiver for receiving the radiated carrier signal at a receiver antenna, for amplifying the received carrier signal, and for converting the amplified carrier signal by demodulation to a base-band signal that is then amplified and output as a full swing digital signal comprising an output data stream. The transmitter and receiver use asynchronous modulation and differential signaling for communicating between integrated circuit (IC) chips or printed circuit boards (PCBs). 
     By choosing a millimeter-wave carrier signal, a higher carrier-to-data-rate ratio further minimizes the dispersion of the modulating signal and removes the need for a power hungry equalization circuit. Moreover, the size of the antenna is dramatically reduced in millimeter-wave frequencies, and in short-range communication applications, the design requirements of antenna such as antenna gain, directivity, radiation efficient, power matching, etc., are greatly relaxed. 
     In the present invention, two configurations are proposed for the antenna for the short range M2W2 interconnect: an on-chip antenna and a bond-wire antenna.  FIG. 1  is a schematic of a single channel wireless M2W2 interconnect using an on-chip differential dipole antenna, while  FIG. 2  is a schematic of a single channel wireless M2W2 interconnect using a bond-wire dipole antenna. 
     The single channel wireless M2W2 interconnect  100  of  FIG. 1  couples a first chip (Chip 1)  102  comprising a transmitter to a second chip (Chip 2)  104  comprising a receiver, wherein the first chip  102  is physically separated from the second chip  104  by a short reach or length  106 . Asynchronous modulation and differential signaling is used for communicating between the integrated circuit (IC) chips or dies  102  and  104  on the same or different printed circuit boards (PCBs). 
     The first chip  102  includes a voltage-controlled oscillator (VCO)  108  for generating a radio frequency (RF) carrier signal, and a transmitter (Tx)  110  for modulating the RF carrier signal using a data-in signal  112  comprising an input data stream, wherein the modulated RF carrier signal is then fed to an on-chip differential dipole antennae  114  that radiates the modulated RF carrier signal. 
     The second chip  104  includes an on-chip differential dipole antenna  116  for receiving the radiated RF carrier signal, which is then fed into a low-noise amplifier (LNA)  118  to generate an amplified RF carrier signal. The amplified RF carrier signal is converted by demodulation at a self-mixer  120  by self-mixing the amplified RF carrier signal with itself  122  to generate a base-band signal. The base-band signal is amplified by a base-band amplifier  124  to generate a data-out signal  126  comprising an output data stream that is a full swing digital signal. 
     The single channel wireless M2W2 interconnect  200  of  FIG. 2  couples a first chip (Chip 1)  202  comprising a transmitter on a first PCB  204  to a second chip (Chip 2)  206  comprising a receiver on a second PCB  208 , wherein the first PCB  204  is physically separated from the second PCB  208  (and thus the first chip  202  is separated from the second chip  206 ) by a short reach or length  210 . As with  FIG. 1 , asynchronous modulation and differential signaling is used for communicating between the integrated circuit chips  202  and  206  on the different PCBs  204  and  208 . 
     The first chip  202  includes a voltage-controlled oscillator (VCO)  210  for generating a radio frequency (RF) carrier signal, and a transmitter (Tx)  212  for modulating the RF carrier signal using a data-in signal  214  comprising an input data stream, wherein the modulated RF carrier signal is then fed to a pair of bond-wire antennae  216  acting as a dipole antenna that radiates the modulated RF carrier signal. 
     The second chip  206  includes a pair of bond-wire antennae  218  acting as a dipole antenna for receiving the radiated RF carrier signal, which is then fed into a low-noise amplifier (LNA)  220  for generating an amplified RF carrier signal. The amplified RF carrier signal is converted by demodulation at a self-mixer  222  by self-mixing the amplified RF carrier signal with itself  224  to generate a base-band signal. The base-band signal is amplified by a base-band amplifier  226  to generate a data-out signal  228  comprising an output data stream that is a full swing digital signal. 
     The first type of antenna configuration, comprising the on-chip differential dipole antennae  114  and  116  of  FIG. 1 , is further illustrated in  FIGS. 3A and 3B .  FIG. 3A  is a schematic of the VCO  108 , transmitter  110  and on-chip differential dipole antenna  114  from  FIG. 1 , and  FIG. 3B  comprises two graphs, wherein an upper graph shows the input data of an amplitude shift-keying (ASK) modulation performed by the transmitter  110  and a lower graph shows the output data of the ASK modulation performed by the transmitter  110 . 
     The transmitter  110  implements the ASK modulation, which is an asynchronous modulation scheme, using a pair of on-off switches  300  and  302  that directly modulates the RF carrier signal using the data-in signal  112 . The output of the transmitter  110  is then fed to the antenna  114  without any further amplification. 
     Unlike other synchronous modulation schemes, such as binary-phase shift-keying (BPSK), the receiver in the asynchronous ASK modulation system only detects changes in amplitude of the RF carrier signal, but does not detect changes in phase or frequency variations of the RF carrier signal. Therefore, the receiver can operate asynchronously without a power hungry phase lock loop (PLL). 
     ASK modulation also eliminates the need for RF carrier signal regeneration at the receiver by using a differential circuit architecture and a differential-mutual-mixing technique to automatically remove the RF carrier signal with no additional components required. Consequently, the M2W2 interconnect does not suffer from process-induced carrier variations between the transmit (Tx) and receive (Rx) functions. 
     The differential dipole antenna  114  is able is boost the input impedance, which provides better power matching between the ASK modulation of the transmitter  110  and the antenna  114 . Moreover, this design using an on-chip antenna  114  eliminates the need to have any packaging operating in millimeter-wave frequencies and electrostatic discharge (ESD) protection circuits. 
       FIG. 4  shows the layout of an exemplary ASK RF-I transmitter according to the present invention, wherein the transmitter is implemented using an IBM 90 nm process, and the die size is 1200 μm×500 μm. 
     The second type of antenna configuration, comprising the pairs of bond-wire dipole antennae  216 ,  218  of  FIG. 2 , is further illustrated in  FIGS. 5A ,  5 B,  5 C and  5 D, wherein  FIG. 5A  is a top view,  FIG. 5B  is a side view,  FIG. 5C  is a cross-section view and  FIG. 5D  is a three dimensional perspective view. Each bond-wire dipole antennae  216 ,  218  is comprised of a pair of bond wires  500  connecting between a pair of pads  502  on an IC chip or die  202 ,  206  mounted on a PCB  204 ,  208 , and a pair of floating pads  504  on a PCB  204 ,  208 . Mounting the bond wires  500  to a pair of floating pads  504  on the PCB  204 ,  208  can stabilize the physical shape of the antenna  216 ,  216 . Moreover, the IC chip or die  202 ,  206  thickness may be controlled to match the optimum antenna length for millimeter-wave frequency operations. 
       FIG. 6A  is a schematic of a receiver with an on-chip differential dipole antenna, and  FIG. 6B  comprises three graphs, wherein a upper graph shows the on-chip antenna first receiving a weak ASK signal, the middle graph shows the low noise amplifier amplifying the ASK signal so that that the self-mixer can demodulate the modulated signal to a base-band digital signal, as shown in the lower graph. 
     On the receiver side, as shown in  FIG. 6A , depending on the application and communication distance, the low noise amplifier  118  may be added to amplify the received RF carrier signal to boost the sensitivity of the receiver. In ASK RF-I, the bandwidth of the low noise amplifier  118  is adjusted to sufficiently support a many 10&#39;s of Gbps data rate, i.e., at microwave frequencies, in contrast to previous RF interconnects that cannot operate at microwave frequencies. A differential common source with a transformer coupling LNA architecture is suitable with such wide band applications. 
     As shown in  FIGS. 6A and 6B , the self-mixer  120  may comprise a differential-mutual-mixer that acts as an envelope detector and carrier removal is used to demodulate the ASK-modulated millimeter-wave carrier signal to a base-band signal. After the differential-mutual-mixer  120 , the demodulated base-band signal is then further amplified at  124  to a full swing digital signal  128 . 
       FIG. 7  shows the layout of an exemplary ASK RF-I receiver according to the present invention, wherein the receiver is implemented using an IBM 90 nm process, and the die size is 1200 μm×1000 μm. 
     Note that the present invention is preferably implemented in high-performance CMOS process technologies. Gate lengths of 90 nm and smaller are required to obtain sufficient transistor gain at carrier rates of 60 GHz and above. Typical implementations will be monolithic semiconductor die for the Tx and Rx functions, respectively. These Tx and Rx chips would be located at the endpoint of a physical signal transmission path, typically on one or more PCBs. 
     Advantages 
     The present invention provides a number of advantages over previous techniques, including:
         Ultra-High Data Rate: Data rates as high as many tens of Gbps is possible because of the high carrier frequency of the present invention.   Low Power: Low power results because the present invention eliminates carrier regeneration at the receiver, and eliminates the need for power-hungry PLL circuitry from the receiver.   Scalable: As CMOS technology continues scaling, higher modulation rates will be possible.   Asynchronous Operation: The ASK modulation scheme is insensitive to process variations that would compromise the operation of a PLL based design.       

     In summary, the present invention offers a highly manufacturable solution for low cost short-reach wireless communication links. Alternative approaches would suffer from lower process yield and higher operating power, and therefore be a less competitive solution. 
     REFERENCES 
     The following references are incorporated by reference herein.
     [1] Changhua Cao, et al., “A 24-GHz Transmitter With On-Chip Dipole Antenna in 0.13-μm CMOS,” IEEE Journal of Solid-State Circuits, Vol. 43, No. 6, June 2008.   [2] U.S. Pat. No. 6,856,788, issued Feb. 15, 2005, to Mau-Chung F. Chang, Tatsuo Itoh, Yongxi Qian, Kang L. Wang, and entitled “Wireless IC Interconnection Method and System.”   [3] Sai-Wang Tam, Eran Socher, Alden Wong and Mau-Chung Frank Chang, “A Simultaneous Tri-band On-Chip RF-Interconnect for Future Network-on-Chip,” Appendix to U.S. Provisional Patent Application Ser. No. 61/185,946, filed on Jun. 10, 2009, by Sai-Wang Tam and Mau-Chung F. Chang, entitled “MILLI-METER-WAVE-WIRELESS-INTERCONNECT (M2W2-INTERCONNECT) METHOD FOR SHORT-RANGE COMMUNICATIONS WITH ULTRA-HIGH DATA RATE CAPABILITY,”.   

     CONCLUSION 
     This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.