Patent Application
20140378065
The present disclosure relates generally to radio receivers and more particularly to receivers for two-way radio devices that are used in a control station mode of operation.
Two-way radio systems have been in use for decades, and are still the preferred means of communication in many fields, such as law enforcement, public safety, rescue, and security. The ability to talk and be heard nearly instantly is very important in these fields. Generally, there are three broad categories of two-way radio devices; portable units, mobile units, and control station units. A portable unit is battery powered and generally carried on the user's person, such as on a belt holster. A mobile unit is generally mounted in a vehicle, and is powered by the vehicles electrical system. A control station is generally fixed and is not moved. Each of these three categories have different operating requirement based on their intended usage, and different levels of performance for various radio parameters have been developed over time to optimize devices for operation in each of these three categories. For example, battery life is a critical concern for portable devices, and as such some tradeoffs may be made in radio performance to increase battery life by reducing the power demand of the radio. Conversely, in a control station device, where power consumption is less of a concern, other performance parameters like intermodulation response rejection and linearity of the receiver are emphasized since there is typically a continuous power supply available.
Despite certain two-way radio devices being designed to operate as non-control station device, a number of aftermarket accessory manufacturers have designed accessories that can be connected or coupled to a non-control station two-way radio device so that a user can use the non-control station two-way radio device as a control station. However, due to the design of the non-control station two-way radio device transceiver, it will not have radio performance like that of a two-way radio device that is originally designed to operate as a control station.
Accordingly, there is a need for a method and apparatus for selectively configuring a two-way radio device to operate in a control station mode or a non-control station mode.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
Embodiments as exemplified by the teachings herein solve the problem of operating a two-way radio device that has been designed for non-control station operation as a control station by adjusting a bias of an amplifying transistor depending on whether a control station mode or a non-control station mode of operation is selected. In the non-control station mode the bias is adjusted to provide improved sensitivity and better blocking of spurious signal content, and in the control station mode the bias is adjusted to provided better linearity and intermodulation response rejection. To accomplish this, a receiver front end for a two-way radio device includes a low noise amplifier that amplifies signals received via an antenna. A bias adjustment network adjusts a bias of the low noise amplifier responsive to a bias control signal that corresponds to the selected mode of operation. An adjustable attenuator is coupled in series with the low noise amplifier and selectively attenuates an output of the low noise amplifier responsive to an attenuation control signal that corresponds to the selected mode of operation. A controller asserts the bias control signal and the attenuation control signal when the two-way radio device is operated in a control station mode. Asserting the bias control signal causes the bias adjustment network to increase bias to the low noise amplifier, and asserting the attenuator control signal causes the adjustable attenuator to increase an attenuation of the output of the low noise amplifier.
The receiver front end 100 includes an antenna 102 that collects radio frequency electromagnetic signals from a transmission medium (i.e. air, space). The antenna 102 can be designed to be particularly sensitive to signals in a frequency range of interest. The signals received at the antenna can include signals and noise at other frequencies, so a harmonic filter 104 is used to attenuate non-desired signal content. The harmonic filter 104 is bi-directional, so it also filters transmitted signals to suppress harmonic content. A switch 106 is used to alternatively coupled the antenna 102 and harmonic filter to either the receiver path or a transmitter path (not shown), as is known. A preselector 108 further attenuates signal content outside of the frequency range of interest. The output of the preselector 108 is fed to a low noise amplifier (LNA) 110. The LNA 110 amplifies the filtered signal to produce an amplified signal 111, which is fed to a selective attenuator 112 that can provide different amounts of attenuation, including no attenuation. The output of the selective attenuator 112 on line 113 is then provided to a post filter 114 which can filter out any harmonic or spurious content produced by the LNA 110 to produce a filtered amplified signal 115 that is provided to a controller 116. The controller 116 receives the filtered amplified signal 115, which is still at its originally received frequency, and processes it to produce a demodulated and processed output 117 that is not at a radio frequency, and is in a form that does not require any further frequency-shift processing. The output 117 can contain audio information, such as speech, as well as data, commands, and other information to be utilized by the two-way radio device. The controller 116 provides one or more control signals 118 to the LNA 110 and the selective attenuator 112. A bias control signal is provided to the LNA 110, and an attenuation control signal is fed to the selective attenuator 112. In some embodiments the bias control signal and the attenuation control signal can be independent signals, and in some embodiments they can be a common signal.
The control signal 118 provided to the LNA 110 controls a bias level of the LNA by changing a bias adjustment network (here contained in the LNA 110), and is asserted in correspondence with the selected mode of operation, either control station or non-control station mode. As used here, the term “bias” refers to the direct current (DC) or “steady state” electrical parameters, such as current and voltage, of an amplifying component, such as, for example, a bipolar junction transistor. In general, the “bias” refers to the level of DC current flowing into the base of a bipolar junction transistor. In the non-control station mode the bias current through the amplifying transistor of the LNA 110, is at a low level (relative to the bias level of the control station mode), while in the control station mode the bias is increased to a level above that of the non-control station mode. The higher bias used for the control station mode increases the linearity of the amplifying transistor, and hence the linearity of the LNA 110. The increased linearity provides better intermodulation rejection response. Specifically, increasing the LNA bias current increases the input intercept point of the fundamental frequency with its 3rd order harmonic, known in the art as the IIP3 measurement. Likewise, the 1 dB gain compression point, known in the art as P1 dB, is likewise increased with high bias current. When the IIP3 is sufficiently increased, the intermodulation rejection performance is also increased. However, in addition to consuming more power, the higher bias level used in the control station mode also increases the small signal gain of the amplifying transistor of the LNA 110. As used here, small signal gain refers to the gain determined by the bias, meaning the DC conditions, applied to the amplifying transistor, and assumes that the signal being amplified (e.g. the signal provided to the base of the amplifying transistor) is limited in magnitude such that it does not significantly change the gain of the amplifying transistor. To compensate for the change in gain in the control station mode relative to the non-control station mode, the selective attenuator 112 is controlled to provide higher or additional attenuation in the control station mode over the non-control station mode, responsive to the control signal 118 (i.e. the attenuator control signal). When operated in the non-control station mode, the bias to the LNA 110 is reduced below that of the control station mode, hence the gain of the LNA is reduced, and less (if any) attenuation is needed in the selective attenuator 112. A control signal 119 to the controller 116 can indicate which mode of operation to use, and thereby cause the controller 116 to provide the appropriate control signal(s) 118.
The two-way radio device 300 is capable of operating in either a control station mode or a non-control station mode. A mode selection interface program 322 can be executed by the processor 304, providing a user of the two-way radio device 300 with a means by which the user can select the desired mode of operation. The two-way radio device can have a default operating mode (either control or non-control station mode), or the two-way radio device can store a mode selection and, for example, upon being powered up, resume operating in a last selected mode. Upon entering or changing the mode, the processor 304 can provide appropriate control signals or control information to the receiver front end 302, which then adjusts the LNA bias and selective attenuator accordingly, as previously described herein.
The adjustable attenuator 417 is likewise responsive to the common control signal 402 and generally operates a pair of switches 424, 426 to select one of two or more attenuations networks 428, 430, depending on whether the common control signal 402 is high or low. When the common control signal 402 is low, a first n-type transistor 418 in the adjustable attenuator circuit 417 will be shut off, causing its output 422 to be pulled high, which will cause a second n-type transistor 420 to be turned on, causing its output 432 to be low. Output 422 is provided to a first common switch input 436, and output 432 is provided to a second common switch input 434 of switches 424, 426. Thus, when the common control signal 402 is in one state, one set of corresponding terminals of the switches 424, 426 are selected, causing one of the attenuator networks 428, 430 to be coupled in series between the output 416 of the amplifying transistor 410 and an output 438 of the adjustable attenuator 417. When the common control signal 402 is in the other state, the other set of corresponding terminals of the switches 424, 426 are selected, causing the other one of the attenuator networks 428, 430 to be coupled in series between the output 416 of the amplifying transistor 410 and an output 438 of the adjustable attenuator 417. Accordingly, when the common control signal 402 is low, the default bias is provided to the amplifying transistor 410, and a default attenuation (which can be no attenuation) is coupled in series with the output of the amplifying transistor. Thus, the low state of the common control signal can be used when the two-way radio device is operated in a non-control station mode. When the common control signal 402 is high, corresponding to control station mode, the bias to the amplifying transistor 410 is increased, and a corresponding attenuation is connected in series with the output 416 of the amplifying transistor 410. The common control signal can be both the bias control signal and the attenuation control signal and can be provided by a controller of the receiver front end, as exemplified in
Accordingly, in some embodiments the receiver front end can be operated by determining a mode of operation of the two-way radio device, which is either a control station mode or a non-control station mode. When the determined mode of operation is the non-control station mode, the receiver front end can be operated by adjusting a bias level of the LNA to a first bias level, and by adjusting the adjustable attenuator (coupled to the output of the LNA) to a first attenuation level. When the determined mode of operation is the control station mode, the receiver front end can be operated by adjusting the bias level of the LNA to a second bias level, and by adjusting the adjustable attenuator to second first attenuation level, the first bias level being lower than the second bias level, and the first attenuation level being a lower attenuation than the second attenuation level.
The embodiments provide the benefit of allowing a two-way radio device to operate in either a control station mode or a non-control station mode. Each mode has different requirements for amplifier linearity, intermodulation response rejection, and blocking in the receiver front end. By increasing the bias to the LNA in the receiver front end in the control station mode (over that of the non-control station mode), the receiver front end will be linear over a wider range of frequencies, and have better intermodulation response rejection. In the non-control station mode, where the bias is lower than that provided in the control station mode, the receiver front end consumes less power, and has improved sensitivity and better blocking.
In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors (or “processing devices”) such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.
Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
