Abstract:
Two or more transceiver units can interact with each other via millimeter wave radio frequency signals. One of the transceiver units can detect time-varying signals having specific waveforms in order to initiate an action such as establishment of a communication link, powering a piece of equipment and the like. The time-varying signal can be generated by a user moving one of the transceiver units and/or by passing an non-transmissive obstruction in between the transceiver units. Related apparatus, systems, and methods are also disclosed.

Description:
BACKGROUND 
       [0001]    As the number of wireless and wired electronic devices increases in residential and office environments, so does the likelihood of interference amongst such devices. Various wireless connections can cause such interference such as cell-phone to base station connections, WiFi-connections, Bluetooth connections, inductive coupled connections RFID based connections, and the like. In a number of these systems (such as cell-phone, WiFi and Bluetooth) the connection occurs through narrow pulses in time domain. Thus, the power dissipated to initiate and establish the connection is minimized. The inductive couple connections and RFID recognition systems of the type that include an interrogator and a transponder (RFID interrogation connection) are popular; and, used for toll collection and inventory control respectively. 
         [0002]    With inductively coupled transmitter-responder arrangements, an interrogator generates an AC power field and a receiving responder tag may be positioned at a preselected position. The interrogator generated AC power is received by the responder tag through inductive coupling; and, the responder tag is activated. A uniquely coded signal particular to that tag can then be generated. In this type of transmitter-responder arrangement, the magnetic field is utilized for responsiveness. This system relies on near-field interaction and thus the radiation nature of the radio signal is ignored. With such arrangements, magnetic fields do not diminish quickly enough with distance and are not suitable in smaller physical spaces such as offices and residences. 
         [0003]    RFID, instead of relying only on the magnetic fields, relies on electromagnetic energy for activation. Like inductive coupled systems, typical RFID recognition systems contain an interrogator (the first unit) and at least one tag (also referred as a transponder or the second unit). The tag or transponder rectifies the RF electromagnetic field in its vicinity and depending on the RF power strength may change its state. The RF field is generated by the interrogator which is thus able to control the tag. The amount of energy decreases as the tag goes away from interrogator. The received RF field at the transponder is critical in determining the behavior of the transponder. 
         [0004]    The radiation pattern near the interrogator is characterized as near-field, while the radiation pattern away for the interrogator a far-field. When the transponder is near-field, the received energy strength can change substantially with slight displacement. In the far-field the received power by the transponder is more deterministic given by the following equation: 
         [0000]    
       
         
           
             
               
                 
                   
                     P 
                     Rx 
                   
                   = 
                   
                     
                       
                         P 
                         Tx 
                       
                        
                       
                         G 
                         Tx 
                       
                        
                       
                         G 
                         Rx 
                       
                        
                       
                         λ 
                         2 
                       
                     
                     
                       
                         ( 
                         
                           4 
                            
                           π 
                            
                           
                               
                           
                            
                           D 
                         
                         ) 
                       
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0005]    In equation (1), P Rx  is the received power at the transponder, P Tx  is the transmitted power of the interrogator, G Tx  is interrogator&#39;s transmitter antenna gain, G Rx  is transponder&#39;s receiver antenna gain, D is the distance between the receiver and transmitter, and λ is the wavelength. In this equation P Tx , G Tx  and G Rx  are fixed quantities determined by interrogator output power, transmitter antenna gain, and the receiver antenna gain respectively. Equation 1 is valid when the receiver antenna is in far-field region of the transmitter antenna. At 3 GHz, the wavelength of wireless signal is about 10 cm in air. So as the distance between the interrogator and transponder increases from 10 cm to 20 cm the signal strength at the receiver drops by ¼ (or 6 db) and from 20 cm to 40 cm it drops by another ¼ and so on. The signal strength decreases by 12 dB when distance is increased four folds. Equation (1) is invalid when there is significant scattering. The above equation is valid for all frequencies ranging from low microwave frequency to high millimeter wave frequencies. 
         [0006]    In some toll booth systems, a threshold detector is in communication with an antenna to measure the power level of an RF interrogation. When the power level is greater than a certain threshold, the system initiates further testing using modulated signals to verify the present modulation state. When both of these states meet predefined conditions, a corresponding transponder can be enabled. Such arrangements are not appropriate for office or residential applications. 
         [0007]    In a typical office environment there are many wireless signals. To name a few, cordless phones at 900 MHz, 1800 MHz and 5000 MHz, Cell phone between 0.9 GHz-2 GHz, Bluetooth in 1-2 GHz, Gaming devices, Computer generated noise and many others. These signals can increase background noise and cause interference. A pre-selection filter is therefore needed to remove the spurious signals. However, such filter can be prohibitively expensive for consumer electronic use. Alternatively, the transmit power P Tx  and thus the threshold be increased so that all of the interference is made comparatively small. However, the increase of P Tx  is not possible because of Federal Communication Commission (FCC) and other regulation. In addition, in a home or office environment there maybe plethora of transponder type devices, all of the devices would see the interrogator power. The transponder (or the second unit) would all be switched on simultaneously in response to the interrogators signal power. This, therefore, results in significant power waste. 
         [0008]    Conventional techniques for selectively initiating communications are complicated when there are a large number of transceiver units within a relatively small area (such as residences and offices). 
       SUMMARY 
       [0009]    In one aspect, a transceiver unit includes a transmitter, a transmitter antenna, a receiver, a receiver antenna, and a control circuit. The transmitter transmits millimeter wave radio frequency signals to a remote transceiver unit that in turn has a remote transceiver transmitter, a remote transceiver transmitter antenna, a remote transceiver receiver, and a remote transceiver receiver antenna. The transmitter antenna is coupled to the transmitter. The receiver is configured to receive millimeter wave radio frequency signals from the remote transceiver unit. The receiver antenna is coupled to the receiver to receive millimeter wave radio frequency signals transmitted by the remote transceiver unit. The strength of the power of the signals received by the receiver antenna is inversely related to the distance between the receiver antenna and the remote transceiver transmitter antenna. The signal strength is also dependent on an orientation of the remote transceiver transmitter antenna in relation to an orientation of the receiver antenna. The control circuit is coupled to the transmitter and the receiver to selectively control the transmission of signals by the transmitter and to characterize signals received by the receiver. The control circuit initiates an action when a time-varying signal having a pre-defined waveform is received by the receiver. 
         [0010]    The pre-defined waveform can be based on the amplitude of the detected signal strength increasing and exceeding a pre-defined threshold. The time-varying signal can be dependent on a physical medium separating the receiver antenna and the remote transceiver transmitter antenna and/or it can be dependent on a repetitive displacement of the remote transceiver transmitter antenna and/or it can be dependent on a movement of the remote transceiver transmitter antenna relative to the receiver antenna and/or it can be dependent on a movement of a non-transmissive element adjacent to the remote transceiver transmitter antenna. The pre-defined waveform can comprise a series/train of pulses. 
         [0011]    The transceiver unit can include memory coupled to the control circuit storing one or more of the pre-defined waveforms. Alternatively or in addition, the control circuit communicates with a remote database to obtain one or more of the pre-defined waveforms and/or control data pertaining to a particular transceiver unit. The control circuit can further identify the remote transceiver unit based on the received signal. 
         [0012]    The remote transceiver transmitter can transmit signal in the 60 GHz band. In such cases, the initiated action can comprise the establishment of a communication link between the transceiver unit and the remote transceiver unit in the 60 GHz band. Such a communication link can support data transfer of a rate of up to six gigabytes per second. 
         [0013]    The separation distance between the transceiver unit and the remote transceiver unit can be up to or equal 10 meters. In some implementations, the separation distance is much smaller, being less than or equal to 25 centimeters. 
         [0014]    The action can comprise initiating communication between the transceiver unit and the remote transceiver unit. Such a communication can be selected from a protocol comprising wireless network, cell-phone, Bluetooth, wire network and peer-to-peer networks. The action can comprise generating an activation signal to initiate a subsequent action. 
         [0015]    The transceiver can include an indicator light that is illuminated when communications are initiated between the transceiver unit and the remote transceiver unit. 
         [0016]    The transceiver unit can also include a receiver circuit coupled to the receiver. The receiver circuit can include a diode detector, a capacitor, a low-noise amplifier, a mixer, an oscillator, and a baseband processor. The diode detector can be coupled to the receiver antenna to receive RF signal received by the receiver antenna. The diode detector can also rectify the RF signal to generate a DC level and include a biasing inductor connected to ground, that feeds bias for the diode detector. The capacitor can be coupled to a cathode of the diode detector for DC generation and storage. The switch can be disposed between the diode detector and the receiver antenna to transmit signal from the receiver antenna to the diode detector (and the switch can have three terminals). The low-noise amplifier can be connected to one of the terminals of the switch to amplify the received signal. The mixer can be coupled to the low-noise amplifier for down-conversion of the amplified received signal to a baseband signal. The oscillator can generate a source frequency to be utilized by the mixer in connection with the down-conversion of the amplified received signal to the baseband signal, the oscillator further being coupled to the transmitter. The baseband processor can process the baseband signal to recover information contained therein. 
         [0017]    In an interrelated aspect, a system includes a primary transceiver unit and a plurality of remote transceiver units. Each remote transceiver unit can have a remote transceiver transmitter, a remote transceiver transmitter antenna, a remote transceiver receiver, and a remote transceiver receiver antenna. The primary transceiver unit can comprise a transmitter, a transmitter antenna, a receiver, a receiver antenna, and a control circuit. The transmitter can transmit millimeter wave radio frequency signals to the remote transceiver units, and the transmitter antenna can be coupled to the transmitter. The receiver can receive millimeter wave radio frequency signals from the remote transceiver units. The receiver antenna can be coupled to the receiver to receive millimeter wave radio frequency signals transmitted by the remote transceiver units. The control circuit can be coupled to the transmitter and the receiver to selectively control the transmission of signals by the transmitter and to characterize signals received by the receiver. The control circuit can initiate an action associated with the corresponding remote transceiver unit when a time-varying signal having a pre-defined waveform is received by the receiver. 
         [0018]    The subject matter described herein provides many advantages. For example, the current techniques allows for increased security between transceiver units while avoiding interference from other devices as well as the generation of false control signals. Furthermore, the transceiver units can be controlled by physical moving the units closer or touching; and, also by swaying the direction of beam; thereby, allowing direct and simple control of the units by the user. Due to the nature of attenuation with distance, mm-wave frequency is attenuated in few inches. As a result non-intended units in the room do not see the strong signal and thus do not switch on (or perform some other action). In addition, the current subject matter provides easy-to-use protocols that consume less power (and as a result are less costly to operate and manufacture). 
         [0019]    The details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    These and other aspects will now be described in detail with reference to the following drawings. 
           [0021]      FIG. 1  is a diagram illustrating first and second transceiver units containing at least one mm-wave transmitter and one mm-wave detector; 
           [0022]      FIG. 2  is a diagram illustrating an RF circuit used to make connection and has a mm-wave detector; 
           [0023]      FIG. 3  is a diagram illustrating typical received power versus separation distance for 60 GHz and 1.2 GHz signals; 
           [0024]      FIG. 4  shows a pulse train generated by relative motion of transceiver units as in  FIG. 1 ; 
           [0025]      FIG. 5  is a diagram illustrating creation of two pulse by moving a relative position of a transceiver unit; 
           [0026]      FIG. 6  is a diagram illustrating a detected waveform having a characteristic of two pulses. 
           [0027]      FIG. 7  is a diagram illustrating an alternative way of creating a waveform as in  FIG. 6  by pointing the antenna of transmitting transceiver unit away from the receiving transceiver unit; 
           [0028]      FIG. 8  is a diagram illustrating creation of a waveform as in  FIG. 6  by changing the characteristic of the transmitting medium through introduction of an obstacle. 
       
    
    
       [0029]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0030]      FIG. 1  is a diagram  100  illustrating a system having a first transceiver unit  101  that is remote from a second transceiver unit  109 . The first transceiver unit  101  can include a transmitter  102  (referenced as TX 1 ) that can generate RF signals for transmission, a transmitter antenna  103  coupled to the transmitter  102  that can transmit RF signals, a receiver antenna  104  that can receive RF signals, a receiver  105  (referenced as RX 1 ) coupled to the receiver antenna  104  that can process RF signals received by the receiver antenna  104 , and a processor  106  for controlling and coordinating the receipt and transmission of signals. The first transceiver unit  101  can be hard wired to a power source (via, for example, a power cord  107  when the first transceiver unit  101  is stationary), or it may contain a self-contained power source such as a battery (when the first transceiver unit  101  is mobile). The first transceiver unit  101  can also include an indicator light  116  that is illuminated when a connection is stabilized (as described below). The first transceiver unit  101  can optionally include memory that stores various pre-defined waveforms (as described below) or it can optionally be coupled to a remote data source (e.g., database accessible via a web service, etc.). 
         [0031]    The second transceiver unit  109  can include a second unit transmitter  112  marked as TX 2  and second unit receiver  113  marked as RX 2 . The second unit transmitter  112  can used to transmit RF signal while the second unit receiver  113  can receive RF signal. The second transceiver unit  109  can have a transmitter antenna  115  and a receiver antenna  114 . 
         [0032]    The current subject matter can, in some implementations, utilize millimeter wave or mm-wave frequencies which typically range from 20 GHz to 200 GHz. In particular, 57-to-65 GHz or the 60 GHz band and 22 GHz-to-29 GHz or the 25 GHz bands. 
         [0033]    The second transceiver unit  109  is shown in three separate positions marked as  109 -A,  109 -B and  109 -C respectively. The second transceiver unit  109  can be physically separate from the first transceiver unit  101  by a medium such air or any dielectric that allows transmission of radio frequency signals. The units marked  109 -B and  109 -C are drawn using phantom lines and represent the unit  109 -A being moved closer to first transceiver unit  101  to the position  109 -B, and then moved away from the first unit  101  represented by the position  109 -C. The distance between position marked by  109 -A and  109 -B can be about 1 cm to about 25 cm (although some implementations allow for a separation distance of up to 10 m). Similarly, the distance between  109 -B and  109 -C can be of the same order. The smallest separation between the first and second transceiver units  101 ,  109  occurs at position  109 -B and can be of the order of 10 cm or lower. In some implementations, the first transceiver unit  101  may physically contact the second transceiver unit  109 . 
         [0034]    The second transceiver unit  109  can include an indicator  117  marked as  117 -A,  117 -B and  117 -C in the three different positions. In position  109 -B and  109 -C, the indicator is lit (on), while in position  112  the indicator is off. When lit, the indicator  117  may indicate that the connection has triggered a control. 
         [0035]      FIG. 2  is a diagram  200  of an circuit for the second transceiver unit  109 . In particular, the receiver circuitry for the second transceiver unit  109  is explained in more detail. Receiving antenna  114  can receive the RF signal that is transmitted to a diode detector  204  that rectifies the RF signal thereby generating a DC level. The diode detector  204  can have biasing inductor  203  that is connected to ground  202 . The inductor  203  can be used for feeding bias for the detector diode  204 . The cathode of the diode detector  204  can be connected to a top of a capacitor  217 . The capacitor  217  can be used for aiding DC generation and storage. A switch  206  can be used to transmit the signal from antenna  114  to the diode detector  204 . The switch  206  can have three terminals and the third terminal can be connected to a low-noise amplifier (LNA)  211 . The LNA  211  can amplify the signal in a low noise manner and feed such signal into a mixer  212  that can be used for down-converting the received signal. An oscillator  216  can generates a source frequency (also called the Local Oscillator or LO) and can be utilized in the mixer  212  to down convert the signal to baseband signal. The baseband signal feeds into the IF and a baseband processor  213 . The baseband processor  213  can recover the information in the received signal. The oscillator  216  can also be used in TX 2  chain that outputs at the transmitter antenna  115 . 
         [0036]    When the second transceiver unit  109  of  FIG. 1  is in position  109 -A, it receives a certain amount of power. If second transceiver unit  109 -A is sufficiently far the received power from the transmitter  102 , is sufficiently low. As the power is low, the diode  204  is not able generate a sufficient DC signal into a controller  215  within the second transceiver unit  109 . As a result the receiver  113  does not respond. On the other hand, when the second transceiver unit  109  is in position  109 -B, and is sufficiently close, it receives sufficient power such that diode  204  is able to rectify and generate a sufficiently high DC signal that goes into the controller  215 . When a high signal is received by the controller  215 , it can cause a sequence of events that turns on the receiver  113 . Subsequently transmitter  112  can also turn on. Once the receiver chain is turned on it can synchronize with the first transceiver unit  101  and starts communicating. 
         [0037]    In a typical room, the signal levels can change drastically and in modern office environments there is very high chance of interference amongst wireless devices. As mentioned above, a number of coding and decoding techniques have been used to overcome interference problems. But none of the techniques work successfully in room environment utilizing received signals power for triggering control. To avoid the random changes in signal level, the first and second transceiver units  101 ,  109  can use mm-wave bands (approximately 30-300 GHz) instead of the 0.5-10 GHz frequencies currently used. As FCC has assigned 57-64 GHz band for unlicensed short range communications, this band (referred as 60 GHz band) is very attractive. 
         [0038]      FIG. 3  illustrates received signal power versus distance for 60 GHz and 1.2 GHz frequencies. This data was obtained through electromagnetic simulation where the transmit power was assumed to be 10 dBm. With this example, both the transmitter and receiver are assumed to have dipole antenna. The distance between the receiver and the transmitter is changed to generate the graph. Referencing  FIG. 3 , line  301  shows the received power  305  at the receiver versus distance  304  when the transmit frequency is 60 GHz as distance between the units is changed. In general, the signal strength increases by  20  dB with a factor of 10 reduction in distance. This condition is true until the transponder is in the near field region. For 60 GHz, the near field region starts at 1 cm. In the near-field region, the energy change versus distance is reduced and becomes unpredictable. 
         [0039]    With reference again to  FIG. 3 , curve  302  shows the power received by the 1.2 GHz system with 10 dBm power and curve  303  with −25 dBm power. The curve with −25 dBm shows the detected signal with distance such that it is more easy to compare with the curve for 60 GHz curve  301 . Near-field for 1.2 GHz signal is of the order of 60 cm. Thus, the power level at 60 GHz is more predictable when the distances are of the order of less than 60 cm. Therefore, a graceful degradation of power occurs at 60 GHz compared to 1.2 GHz when the distance changes and this is true all the way to 1 cm. Similarly mm-wave (&gt;20 GHz) may be used for this very reason. The current subject matter, in some implementations, can use mm-wave frequencies for establishing short range integrator and transponder communication. Unlike toll booth applications, devices incorporating the subject matter described herein can be hand-held such that a user can move the device to close proximity (few millimeters) or move it away (few centimeters). During this duration the power can drop substantially, indicating a triggering of event. Further the user can repeat the triggering actions as often as needed. In addition, to its use for forming connection with nearby units, the 60 GHz band can also be used for high data rate communication; thus, the same electronics can used to detect-and-form connections and additionally for high speed communications. This happens when switch  206  of  FIG. 2  is connected to the low noise amplifier  211 ; thereby, activating the receiver for broadband communication. 
         [0040]      FIG. 4  is a diagram  400  illustrating the waveform at the cathode of diode  219 , shown in  FIG. 2 , when the second transceiver unit  109  is moved from  109 -A to  109 -B to  109 -C in  FIG. 1 . Plotted in the vertical direction is detected voltage  406  at the cathode versus time on horizontal axis  405 . As the units are spaced apart during the position depicted by  109 -A, the detected signal is low and depicted by the curve section  401 . As the separation decreases the detected signal increases till it reaches the peak at position  109 -B. This is depicted by curve section  402 . As the unit moves to position  109 -C the signal drops down and is shown by a second low value curve section  403 . This signal is fed into the controller  215  of  FIG. 2 . The controller  215  has a threshold level depicted by line  404 . When the detected signal exceeds the threshold line as at the label  408 , the controller  215  may trigger and launch a sequence of steps to provide some controlling action on the second transceiver unit  109 . Alternatively the sequence of steps could occur when the detected signal goes below the threshold as in point indicated by label  409 . In this example, the controller  215  converts the signal into a pulse of duration Pw indicated by  407 . The generated pulse has square wave characteristics with certain pulse width. Depending on how the units are moved relative to each other various pulse characteristics can be generated. This characteristic of the pulse can then be used for controlling the transceiver units  101 ,  109 . 
         [0041]      FIG. 5  is a diagram  500  that illustrates an approach where two pulses are generated. In the figure, both the first and the second pulses are represented by a rectangular box (containing electronics) and an antenna. This is representation and can be replaced by a number of other possibilities including just an antenna. With this example, it is assumed that the first unit transmits mm-wave signal while the second unit has a corresponding detector diode. However, it the respective roles can be easily interchanged without changing the overall focus of this specification. The first transceiver unit  501  goes from position A to position B shown with phantom lines  501 -B. During the same time the second unit  510  stays in its location and is shown with phantom lines  510 -B. As result the transceiver units  501 -B,  510 -B come closer. In the next step the first unit  501 -B moves to position C shown in phantom line  501 -C. During the same time the second unit  510  shown with phantom lines  510 -B stays in its location and is shown with phantom lines  510 -C. Now the distance between the units  501 ,  510  is increased. In the next step, the first unit  501  shown with phantom lines  501 -C moves to position D shown in phantom line  501 -D. During the same time the second unit  510  shown with phantom lines  510 -C stays in its location and is shown with phantom lines  510 -D. Now the distance between units is decreased. In the next step, the first unit  501  shown with phantom lines  501 -D moves to position E shown in phantom line  501 -E. During the same time the second unit shown with phantom lines  510 -D stays in its location and is shown with phantom lines  510 -E. Now the distance between units  501 ,  511  is increased. Thus these steps describe an action where the units  501 ,  510  come closer and then separate and then come closer again. 
         [0042]    The effect of the physical displacement of the first and second units is shown in the diagram  600  of  FIG. 6 .  FIG. 6  plots the detected voltage at the cathode of the diode  219  shown in  FIG. 2  that is included in the second unit  510 . For position A of  FIG. 5 , because the separation between units  501 ,  510  is large, the detected signal is small and the curve section labeled  601  shows low signal level. For position B of  FIG. 5 , the units  501 ,  510  come closer. As a result the received signal is large and depicted by curve labeled  602 . Similarly in position C of  FIG. 5 , the units  501 ,  510  are further away and detected signal is smaller thereby producing curve section  603 . Similarly in position D and E of  FIG. 5 , curve sections  604  and  605  are produced respectively. Clearly by displacing the units  501 ,  510 , the receive-signal can be varied with time. 
         [0043]    When the receive signal is sufficiently strong, the detected signal derived from the receive-signal exceeds a threshold voltage. As a result two pulses are generated. These pulses are depicted in  FIG. 6  by curves  606  and  607 . The controller  215  examines this time domain waveform and based on pulse characteristics it performs the required controlling action. Such controlling action may include but is not limited to switching ON-or-OFF of the unit or performance of other controlling action such as communication link formation. Also note while only two pulses have been show, multiple pulses can be generated by repeatedly changing the separation between the units  501 ,  510 . For example, one arrangement could require a number of pulses as a benchmark to trigger control signal. Alternatively, the rate of change of the detected signal may be utilized for determining the trigger event. Thus a number of possible characteristics of the pulse could be used for control trigger. Repeated or complex pulse characteristics can be adopted to avoid false trigger and saves considerable power. 
         [0044]    While physical displacement of the relative positioning of the two units  501 ,  510  can achieve the required pulse formation, it is the not the only means for creating modulated signal. The diagram  700  of  FIG. 7  shows an approach that utilizes the antenna direction, while the diagram  800  of  FIG. 8  shows the use of an obstacle such as a human hand for control initiation. In  FIG. 7 ,  706  represent the transmitter antenna  103  of the first transceiver unit  101  (the box is omitted for brevity) while  705  represents the receiver antenna of the second transceiver unit  110 . With this implementation, for exemplary purposes, it can be assumed that the first unit  101  transmits mm-wave signal while the second unit  110  has the detector diode. However, it is clear that this role can be easily interchanged without changing the overall focus of this specification. Each of these antennas  103 ,  115  tends to radiate (receive) signal in greater strength towards (from) some direction than in others. This is depicted by an antenna pattern that shows the direction of the beam. For antenna  706 , the shape  702  is a representative antenna pattern and it has peak in the direction of receiver antenna  705 . As shown in Equation 1, the receive signal is proportional the antenna gain. In simpler terms, if the beam of antenna  706  is directed toward antenna  705  the signal strength would be higher. Conversely when the antenna  706  is directed away from antenna  705  the gain is lower. This feature of the equation 1 is exploited. Thus, the antenna  706  (which could represent a handheld device) is turned away from the antenna  705 . The position marked A, B, C, D and E in  FIG. 7  indicates a possible orientation that would result in a waveform very similar to  FIG. 6 . This, thereby, shows that pulse generation can also be accomplished by axial movement. Also note that either of the units  101 ,  110  can have a varying axial movement. At the transmitter end, the axial movement would change the transmitted signal and send it towards-certain-spatial-direction. Similarly by changing the receiver, the received signal is received from-certain-spatial-direction. Also beams can be redirected using electronic means such as alternate antenna or changing load on the antenna. 
         [0045]      FIG. 8  is a diagram  800  illustrating how transmission characteristics of the medium can be changed. An obstacle object  805  (also shown in different position by  801 ,  802 ,  803 ,  804 ), which is made of metal block, body part, or any material, is interposed between the antenna  705  and  706 . Because the beam encounters this object  805  its strength at the receiver is changed. By moving the object  805  in-and-out of the path a modulation can be generated. For the waveform in  FIG. 6 , the object  805  needs to be moved from A to B to C to D to E. The object in effect has changed the medium that separates the two antennas. 
         [0046]    Aspects of the subject matter described herein may be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations may include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. 
         [0047]    These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and may be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the term “machine-readable medium” refers to any computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor. 
         [0048]    While the current subject matter is generally described in connection with two transceiver units, it will be appreciated that a network of such units can be utilized (with combined mobile and fixed systems). In all of these units, mm-wave signals can be utilized for generating a control signal thereby forming a connection between units. 
         [0049]    Although a few variations have been described in detail above, other modifications are possible. Other embodiments may be within the scope of the following claims.