Monitoring radio frequency transmitter

Abstract

The invention relates to monitoring a radio frequency transmitter. The proposed embodiments provide a radio frequency (RF) transmitter apparatus and a method for monitoring an RF transmitter. The RF transmitter apparatus includes a phase shifter configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to an RF reference signal. The RF transmit signal is coupled to the transmit antenna while a portion of the RF transmit signal is coupled out to generate an RF feedback signal. A binary phase stepper is provided to generate the RF test signal based on specifically applying a first phase offset or a second phase offset to the RF reference signal. A mixer is also provided to mix the RF test signal and the RF feedback signal to generate a mixer output signal. As the hardware of the binary phase stepper (operable only in two modes) is simplified, space may be saved. Meanwhile, an effective device for monitoring a phase shifter is disclosed, which requires only two settings of the phase stepper.

Description

TECHNICAL FIELD

[0001] The present invention generally relates to radio frequency (RF) transmitters. In particular, the present invention relates to an RF transmitter arrangement and a method for evaluating the performance of an RF transmitter arrangement. BACKGROUND

[0002] Modern radar devices such as radar distance and speed sensors can be integrated in so-called monolithic microwave integrated circuits (MMICs). Radar sensors can for example be used in the automotive field, where they are used in advanced driver assistance systems (ADAS) such as adaptive cruise control (ACC). Such systems can be used to automatically adjust the speed of a car in order to maintain a safe distance to other forward driving cars. However, RF circuits are also used in many other fields, such as RF communication systems.

[0003] Radar MMICs typically incorporate the elements of the RF front-end of a radar transceiver (e.g. local oscillators, power amplifiers, low noise amplifiers, mixers, etc.), the analog pre-processing of the intermediate frequency (IF) or baseband signal (e.g. filters, amplifiers, etc.) and the analog-to-digital conversion (ADC). In applications employing beam steering techniques and phased array antennas, the RF front-end typically comprises multiple receive and transmit channels (to sense the angle of incidence of incoming RF radar signals).

[0004] The phase of the transmitted signal has to be controlled very accurately. Therefore, it is necessary to know the phase shift and / or amplitude gain caused by each output channel. Therefore, feedback hardware for measuring the transmit phase is implemented in many state-of-the-art radar MMIC transceivers. This hardware facilitates the phase calibration of each transmit channel. However, this hardware requires additional space and consumes additional power.

[0005] Therefore, there is a need for a compact and energy-efficient arrangement for monitoring the operation of an RF transmitter. SUMMARY

[0006] Examples disclosed herein present a radio frequency (RF) transmitter apparatus including a phase shifter, a coupler, a binary phase stepper, and a mixer. The phase shifter is configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal. The coupler is configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal. The binary phase stepper is configured to receive the RF reference signal and to generate an RF test signal. The phase stepper is configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal and a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, the first phase offset being different from the second phase offset. The mixer is configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0007] The proposed method makes use of a binary phase stepper that is capable of applying only two different phase offsets to an RF reference signal to generate an RF test signal for comparison with an RF feedback signal to evaluate a transmit path of the RF transmitter apparatus (i.e., to monitor the phase shifter). In this way, the operation of the phase shifter can be evaluated while minimizing the space required by the monitoring hardware and while facilitating fast monitoring. Thus, the proposed RF transmitter apparatus finds particular use when employed within a radar MMIC.

[0008] Other examples disclosed herein provide a method for evaluating the performance of an RF transmitter apparatus. The RF transmitter apparatus includes a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal, a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal, a phase stepper configured to receive the RF reference signal and to generate an RF test signal based on applying one or more test phase offsets to the RF reference signal, and a mixer configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal. The method includes:

[0009] controlling the phase shifter to generate a first sequence of RF transmit signals while the phase stepper applies a first phase offset to the RF reference signal, each of the RF transmit signals based on each of a test set of phase offsets applied to the RF reference signal;

[0010] While the phase stepper applies a second phase offset to the RF reference signal, the phase shifter is controlled to generate a second RF transmit signal sequence, each of the RF transmit signals being based on each phase offset in the test set for which a phase offset is applied to the RF reference signal;

[0011] The mixer output is sampled at multiple sampling times to provide a sequence of digital sample values, wherein each digital sample value in the sequence corresponds to a corresponding RF transmit signal in a first RF transmit signal sequence or a corresponding RF transmit signal in a second RF transmit signal sequence.

[0012] A Discrete Fourier Transform (DFT) is applied to a sequence of digital sample values ​​to generate multiple DFT bin values, each corresponding to a different harmonic present in the sequence. The DFT bin values ​​include the DC amplitude of the sample value sequence, the amplitude of the first harmonic of the sample value sequence, and the amplitude of the third harmonic of the sample value sequence; and

[0013] The defect of the phase shifter is identified based on at least one of the identified DC amplitude value, first harmonic amplitude value, and third harmonic amplitude value.

[0014] Therefore, the proposed method facilitates the detection of defects in the phase shifter by manipulating a phase stepper to apply only two distinct phase shifts. This is achieved by manipulating the phase shifter to generate a sequence of RF transmitted signals (by applying a test set of phase shifts to an RF reference signal), while simultaneously applying a first phase shift and a second phase shift to generate a sequence of digital sample values. Thus, the processing of these digital sample values ​​can provide information for the detection / identification of defects in the phase shifter, while minimizing the power consumption and time required to complete the process.

[0015] Those skilled in the art will recognize the additional features and advantages upon reading the following detailed description and viewing the accompanying drawings. Attached Figure Description

[0016] This disclosure is illustrated by way of example and in a non-limiting manner, in which the same reference numerals refer to similar or identical elements. The elements in the figures are not necessarily proportional to each other. Features of the various illustrated examples may be combined unless they exclude each other.

[0017] Figure 1 The diagram illustrates an RF transmitter device.

[0018] Figure 2 A binary phase stepper according to an aspect of the present invention is illustrated.

[0019] Figure 3The diagram illustrates a flowchart of a method for evaluating the performance of an RF transmitter device. Detailed Implementation

[0020] Some examples described herein provide RF transmitter devices. The RF transmitter device includes a binary phase stepper capable of operating in only two modes, each applying a different phase shift to an RF reference signal to generate an RF test signal, while a phase shifter generates an RF transmit signal by applying a phase shift to the RF reference signal. An RF feedback signal is acquired from the RF transmit signal and compared with the RF test signal, thereby allowing the operation of the phase shifter to be evaluated.

[0021] Another example described herein provides a method for evaluating the performance of an RF transmitter device. This method generates a sequence of digital sample values ​​by mixing multiple RF transmit signals generated by a phase shifter with an RF test signal generated by a phase stepper operating in two different modes.

[0022] The proposed embodiments provide a radio frequency (RF) transmitter apparatus and a method for monitoring the RF transmitter. The RF transmitter apparatus includes a phase shifter configured to generate an RF transmit signal based on an offset of one of a plurality of phase offsets applied to an RF reference signal. The RF transmit signal is coupled to a transmit antenna, while a portion of the RF transmit signal is coupled out to generate an RF feedback signal. A binary phase stepper is provided to generate an RF test signal by specifically applying a first phase offset or a second phase offset to the RF reference signal. A mixer is also provided to mix the RF test signal and the RF feedback signal to generate a mixer output signal. As a result of the simplified hardware of the binary phase stepper (operable only in two modes), space can be saved. Meanwhile, an efficient apparatus for monitoring the phase shifter is disclosed, requiring only two settings for the phase stepper.

[0023] To best understand this disclosure, it is important to understand the operation of existing RF transmitter devices with functions for evaluating the performance of phase shifters.

[0024] Figure 1 An example of an RF transmitter device 100 is illustrated. It should be noted that... Figure 1 The RF transmitter device 100 is a simplified block diagram illustrating the basic structure of the RF transmitter transmission path (i.e., RF front end) and measurement path, and may thereby include additional components depending on the application, such as multiple transmission paths, each of which applies a different phase offset to generate different RF transmission signals.

[0025] The transmission path of the RF transmitter device 100 includes a phase shifter 110, an output amplifier 120, a coupler 130, and a transmitting antenna 140. The measurement path includes a phase stepper 150, a mixer 160, an ADC converter 170, and a processor / controller 180.

[0026] The RF reference signal is generated, for example, by a local oscillator (LO). The RF reference signal can therefore also be referred to as the LO signal. The RF reference signal can be frequency modulated. In radar applications, such as automotive applications, the LO / RF reference signal is typically in the ultra-high frequency (SHF) or extremely high frequency (EHF) bands (e.g., between 76 GHz and 81 GHz).

[0027] The RF reference signal is fed by the splitter 105 into both the transmission path and the measurement path of the RF transmitter device 100.

[0028] In the transmit path, phase shifter 110 receives an RF reference signal and generates an RF transmit signal. The RF transmit signal is generated by applying one of a plurality of phase shifts to the RF reference signal. Therefore, phase shifter 110 controls the phase of the RF transmit signal. That is, phase shifter 110 is required for precise control of the phase of the RF transmit signal—either programming different starting phases of the RF transmit signal or continuously modulating the phase of the RF transmit signal. Phase shifter 110 thus controls the overall phase shift / hysteresis of the transmit path.

[0029] In some cases, phase shifter 110 can apply any phase shift between 0 and 360 degrees. Typically, phase shifter 110 can adjust the phase of the RF reference signal to one of 64 or more different (equally spaced) phases. Phase shifter 110 can be implemented using an IQ modulator (in-phase / quadrature modulator). However, phase shifter 110 can be any component capable of applying one of multiple phase shifts, as understood by those skilled in the art.

[0030] The transmission path may additionally include an output amplifier 120 for amplifying the RF transmitted signal. The transmission path also includes a coupler 130 configured to couple the RF transmitted signal to a transmitting antenna 140 for radiating into the environment.

[0031] More specifically, coupler 130 is configured to provide the power of the RF transmitted signal to the transmit antenna 140 with minimal power loss. Coupler 130 also couples out a portion of the RF transmitted signal power and provides it to the measurement path, and more specifically to the mixer 160. This portion is typically in the range of 20 dB to avoid the RF signal sent to the antenna suffering too much power reduction due to its power separation.

[0032] It is desirable to know the precise phase offset of the RF transmitted signal relative to an RF reference signal applied by the RF transmission path (i.e., actively applied by phase shifter 110 and passively applied by other components such as amplifier 120). In practice, if the RF transmitter is part of a radar sensor device, the phase of the RF transmitted signal must be known to derive the radiation angle. In other words, the phase offset of the RF transmitted signal must be tuned to a specific value to achieve the desired radiation angle.

[0033] However, various factors can affect the phase offset of the transmission path. For example, the temperature of components in the transmission path can alter the phase offset imposed by these components. Furthermore, manufacturing tolerances and aging can affect the phase offset imposed by components, particularly phase shifter 110. Therefore, any defects in the phase offset must be detected and compensated (e.g., through calibration of phase shifter 110) to ensure proper operation of the RF transmitter. This is relevant for radar applications, and particularly for radar used in the automotive sector, as any error could lead to unsafe radar operation. However, phase offset compensation can also be required for other applications, such as, for example, in wireless communication systems.

[0034] Therefore, state-of-the-art RF transceivers typically include the measurement path depicted in the figure.

[0035] The measurement path includes a phase stepper 150, which is configured to receive an RF reference signal and apply one of a plurality of phase offsets to the RF reference signal to generate an RF test signal. Similar to the phase shifter 110 in the transmit path, the phase stepper 150 applies one of a plurality of (typically equidistant) phase offsets between 0 and 360 degrees.

[0036] Unlike phase shifter 110, phase stepper 150 typically has fewer settings (i.e., it can be controlled to apply a smaller number of different phase shifts). However, with more settings, the phase stepper 150 results in a more accurate measurement of the phase shift applied by phase shifter 110 (due to noise averaging effects). Therefore, it is generally desirable to provide a phase stepper 150 with a large number of settings. The trade-off is that it may take longer to perform measurements because more readings need to be acquired and more processing is required.

[0037] Furthermore, the measurement path includes a mixer 160, which receives the RF test signal from the phase stepper 150 and the RF feedback signal coupled from the RF transmitted signal by the coupler 130. The RF feedback signal is therefore substantially the same as the RF transmitted signal (i.e., with the same phase offset).

[0038] Mixer 160 combines the RF test signal and the RF feedback signal to generate the mixer output signal. Specifically, the RF test signal is down-converted by mixer 160 with the RF feedback signal to generate the mixer output signal.

[0039] Finally, the mixer output signal is digitized by an analog-to-digital converter (ADC). That is, the ADC 170 samples the mixer output signal to generate digital sample values. These digital sample values ​​can then be processed by the processor 180 to extract amplitude and phase information.

[0040] More specifically, in order to extract the phase measurement of phase shifter 110 for a given setting (i.e., for a phase shift applied by phase shifter 110), the following procedure is performed:

[0041] (i) The phase shifter 110 is controlled to apply a phase shift to the RF reference signal to generate an RF transmit signal (and thus generate a special RF feedback signal);

[0042] (ii) The phase stepper 150 is controlled to apply each of a plurality of phase offsets available from the phase stepper 150 (e.g., cyclically set through each phase stepper 150);

[0043] (iii) For each offset applied by the phase stepper 150, (and after the signal has stabilized) the ADC is controlled to generate digital sample values ​​by sampling the mixer output signal;

[0044] (iv) Once all digit sample values ​​have been generated, the FFT is applied to the digit sample values;

[0045] (v) Phase and amplitude information extracted from the first harmonic of the FFT.

[0046] Therefore, in order to extract phase and amplitude information for a phase setting of phase shifter 110, phase stepper 150 must be cycled through various settings, with measurements taken during each setting. It should be noted that the amplitude of the transmit path includes the amplitude of output amplifier 120, and the phase of the transmit path includes the controllable phase of phase shifter 110 and the phase of output amplifier 120. This is in addition to another phase shift applied in the measurement path from the output of coupler 13 to the input of mixer 160 (which is essentially constant due to the inclusion of passive components).

[0047] It should be noted that the transmitter must be active during this measurement process, and therefore consumes power. It should also be noted that because the phase stepper 150 must have a large number of settings, it consumes a significant amount of space, which is particularly disadvantageous when the RF transmitter device 100 is implemented in a radar MMIC. Furthermore, the measurement process consumes power and may therefore heat the RF transmitter device 100, leading to further deviations in phase offset. Therefore, it has been recognized that there is a need for improved devices for monitoring the phase offset imposed by the transmission path.

[0048] Figure 2 The figure illustrates a binary phase stepper 151 according to this aspect of the invention. The described binary phase stepper 151 replaces the phase stepper 150 described above.

[0049] A binary phase stepper 151 is proposed to replace the phase stepper 150, which is typically used to monitor the phase offset imposed by the transmit path. That is, known phase steppers are operable in a large number of different modes / settings to provide a large number of different phase offsets. In practice, this is often desired to improve measurement accuracy using the aforementioned known measurement techniques (where the mixer output signal of each RF test signal is sampled as the phase stepper cycles through each of the multiple phase offsets). Instead, the proposed solution provides a binary phase stepper 151 that is specifically operable in only two modes.

[0050] As can be seen, the binary phase stepper 151 is operable only in a first mode and a second mode. In the first mode, the phase stepper 151 generates an RF test signal based on applying a first phase offset (e.g., 0 degrees) to the RF reference signal. In the second mode, the phase stepper 151 generates an RF test signal based on applying a second phase offset (e.g., 90 degrees) to the RF reference signal. For clarity, the first phase offset is different from the second phase offset.

[0051] This significantly reduces the area and complexity of the phase stepper 150, since only two distinct offsets need to be applied by the binary phase stepper 151.

[0052] In one embodiment, the difference between the first phase offset and the second phase offset in the binary phase stepper 151 is 90 degrees. For example, the first phase offset could be 0 degrees, and the second phase offset could be 90 degrees. As will be clear from the following, this choice of phase offset simplifies the processing / calculation used to determine the phase and amplitude information of the RF transmitted signal. However, alternative phase offsets can still achieve the derivation of phase and amplitude information.

[0053] Therefore, in order to determine the phase information of the RF transmitted signal, the controller 180 of the RF transmitter device 100 can be configured to first control the phase shifter 110 to generate a first RF transmitted signal sequence while the binary phase stepper 151 operates in a first mode (i.e., while the binary phase stepper 151 applies a first phase offset to the RF reference signal to generate the RF test signal). In this case, each signal in the RF transmitted signal is based on each offset of the test set to which a phase offset is applied to the RF reference signal. The controller 180 also controls the ADC to sample the mixer output at a first plurality of sampling times to provide a first sequence of digital sample values, wherein each value in the first sequence of digital sample values ​​corresponds to a corresponding signal in the first RF transmitted signal sequence.

[0054] Essentially, in order to determine the phase and amplitude information of the transmit path for a given setting of phase shifter 110 (e.g., for an X-degree offset applied by phase shifter 110), phase stepper 151 is controlled to apply only one phase offset to the RF reference signal to generate an RF test signal. To gather sufficient information to determine the phase and amplitude information, phase shifter 110 is controlled to cycle through multiple test phase offsets.

[0055] In other words, instead of cycling through a large number of settings (which would require the phase stepper 150 to be able to apply a large number of phase shifts), the phase shifter 110 is controlled to cycle through a large number of settings. For example, in addition to the phase shift setting being evaluated, the phase shifter 110 can be controlled to apply test phase shifts, such as a first test phase shift (e.g., 0 degrees), a second test phase shift (e.g., 90 degrees), a third test phase shift (e.g., 180 degrees), and a fourth test phase shift (e.g., 270 degrees). Of course, the ADC can be controlled to generate digital sample values, each corresponding to the mixer output as the phase shifter 110 is controlled to apply each of these test phase shifts.

[0056] The example above should not be considered restrictive, and alternative test phase offsets can be applied. However, subsequent processing / calculations can be simplified by using a set of equidistant phase offsets, such as 0, 90, 180, and 270 degrees.

[0057] In other words, unlike the process described above for extracting phase measurements of phase shifter 110, the following process for calculating phase and amplitude information for a given configuration of phase shifter 110 is proposed:

[0058] (i) The phase stepper is controlled by a switch to operate in a first mode, in which a first phase offset (e.g., 0-degree phase offset or 90-degree phase offset) is applied to the RF reference signal to generate an RF test signal;

[0059] (ii) The phase shifter 110 is controlled to apply one of a plurality of test phase offsets to the RF reference signal to generate an RF transmit signal (and thus a specific RF feedback signal). The test phase offsets may include equidistant phase offsets. For example, the test phase offsets may include four equidistant phase offsets (e.g., X+0, 90, 180, and 270 degrees);

[0060] (iii) For each test phase offset applied by phase shifter 110, (and after the signal has stabilized) the ADC is controlled to generate digital sample values ​​by sampling the mixer output signal;

[0061] (iv) Once all digital sample values ​​have been generated, the FFT is applied to the digital sample values. For example, when four equidistant phase shifts are applied by phase shifter 110, a simple 4-point FFT can be applied, requiring only basic arithmetic operations applied to the four digital sample values;

[0062] (v) Extract phase and amplitude information from the first harmonic of the FFT.

[0063] Therefore, it has been realized that only a phase stepper 151 with two operating modes is required (i.e., capable of applying only two phase offsets to the RF reference signal). This greatly reduces the complexity of the phase stepper 151, saves silicon space, and reduces power consumption.

[0064] In one example, phase stepper 151 is configured to apply a 0-degree phase offset to the RF reference signal, and phase shifter 110 is configured to apply 0, 90, 180, and 270-degree test phase offsets, in addition to the X-degree setting of phase shifter 110 being evaluated. In this case, four digital sample values ​​will be generated. Sig1 represents the digital signal value associated with phase shifter 110 applying a 0-degree test phase offset, Sig2 represents the digital signal value associated with phase shifter 110 applying a 90-degree test phase offset, Sig3 represents the digital signal value associated with phase shifter 110 applying a 180-degree test phase offset, and Sig4 represents the digital signal value associated with phase shifter 110 applying a 270-degree test phase offset.

[0065] In this case, a very simple four-point FFT can be calculated using the following formula:

[0066] Re1 = Sig1 - Sig3 [1]

[0067] Im1 = -(Sig2 - Sig4) [2]

[0068] Therefore, by applying a simple arithmetic function to the voltage represented by digital sample values, the phase and amplitude information can then be extracted directly from the Re1+j*Im1 signal.

[0069] Of course, this is a simplified example of how the process can be performed. An alternative test phase offset can be applied, from which phase and amplitude information can be derived. However, the example above provides a very simple, and therefore fast and energy-efficient, device for measuring the phase and amplitude information of the transmission path, corresponding to a phase shifter 110 operating according to a given setting.

[0070] The RF transmitter device 100 may therefore include a processor 180 configured to receive a first digital sample value sequence and generate phase and amplitude information of the RF transmitted signal based on the result of processing the first digital sample value sequence with a discrete Fourier transform.

[0071] The processor 180 can then be configured to modify the operating parameters of the phase shifter 110 and / or generate signals indicating faults in the phase shifter 110 based on the generated phase and amplitude information. That is, if the generated phase and amplitude information does not correspond to the expected values, then actions can be taken to report and correct the operation of the phase shifter 110.

[0072] According to another aspect of the invention, a method for evaluating the performance of an RF transmitter device is provided that is faster than existing methods. This method... Figure 3 It is depicted in the form of a flowchart.

[0073] In state-of-the-art implementations, the performance / functionality of the phase shifter in an RF transmitter device is typically evaluated by measuring the phase and amplitude information of the transmission path for each phase setting of the phase shifter to be used (in the manner described above). However, it should be understood that this is very time-consuming, as there can be many settings of the phase shifter to be evaluated, and each measurement of phase and amplitude information takes time.

[0074] To overcome this problem, a recent approach has been proposed to skip measuring phase and amplitude information for less critical settings of the phase shifter. That is, only the phase measurement of the most critical settings of the phase shifter is performed, assuming that the less critical settings are operating correctly. However, this assumption can lead to errors.

[0075] Therefore, the proposed method offers a small extension to the above measurement process to provide a rapid method for evaluating the performance of RF transmitter devices, while avoiding the introduction of unwanted assumptions.

[0076] For clarity, the proposed method can be implemented on an RF transmitter device as described above, which includes a binary phase stepper that is operable in only two modes, but the proposed method can also be applied to an RF transmitter device having a phase stepper that is operable in more than two modes (but the use of such a phase stepper with more than two modes is not required).

[0077] In other words, the RF transmitter device includes a phase shifter configured to receive an RF reference signal and to generate an RF transmit signal based on one of a plurality of phase shifts applied to the RF reference signal. The RF transmitter also includes a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal. Furthermore, this provides a phase stepper configured to receive the RF reference signal and generate an RF test signal based on one or more test phase shifts applied to the RF reference signal. In some embodiments, the phase stepper is... Figure 2 The binary phase stepper is depicted in the diagram. Finally, the RF transmitter device includes a mixer configured to receive an RF test signal and an RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0078] In step 210, the phase stepper applies a first phase offset to the RF reference signal. Therefore, the phase stepper generates an RF test signal with the first phase offset and provides the RF test signal to the mixer. The first phase offset can be, for example, 0 degrees. However, the example is not limited to 0 degrees.

[0079] In step 220, while the phase stepper applies a first phase shift to the RF reference signal, the phase shifter is controlled to generate a first RF transmit signal sequence. Each signal in the RF transmit signal is based on each shift in a test set for which a phase shift is applied to the RF reference signal. In this manner, an RF feedback signal sequence is generated and provided to the mixer, while an RF test signal with the first phase shift is also provided to the mixer.

[0080] In step 230, the phase stepper applies a second phase offset to the RF reference signal. Therefore, the phase stepper generates an RF test signal with the second phase offset and provides the RF test signal to the mixer. The second phase offset can be, for example, 90 degrees. However, the example is not limited to 90 degrees, as long as the second phase offset is different from the first phase offset.

[0081] In step 240, while the phase stepper applies a second phase shift to the RF reference signal, the phase shifter is controlled to generate a second RF transmit signal sequence. Each signal in the RF transmit signal is based on each shift in the test set for which a phase shift is applied to the RF reference signal. In this way, an RF feedback signal sequence is generated and provided to the mixer, while an RF test signal with the second phase shift is also provided to the mixer.

[0082] The test set for phase offset can include equidistant phase offsets. For example, the test set for phase offset can include four equidistant phase offsets, such as 0, 90, 180, and 270 degrees.

[0083] It should be noted that steps 210-240 can be performed in a different order. For example, the phase shifter can be configured to apply one offset in the test set of phase offsets, while the phase stepper is controlled to sequentially apply a first phase offset and a second phase offset. In any case, the phase stepper and the phase shifter must be controlled such that the mixer receives a complete combination of the RF feedback signal with the test phase offset and the RF test signal with the first and second phase offsets.

[0084] In step 250, the mixer output is sampled at multiple sampling times to provide a sequence of digital sample values. That is, the mixer combines the input RF test signal and the RF feedback signal, and samples the resulting output at multiple different times. Each digital sample value in the sequence corresponds to a corresponding RF transmit signal in the first RF transmit signal sequence or a corresponding RF transmit signal in the second RF transmit signal sequence. Specifically, the mixer output is sampled for each combination of the first or second RF transmit signal sequence from the phase shifter and the test signal from the phase stepper. Therefore, a sequence of digital sample values ​​is obtained for a complete combination of the two settings of the phase stepper and the test settings of the phase shifter.

[0085] For clarity, each digital sample value will correspond to a downconverter signal whose amplitude depends on the phase difference between the RF feedback signal and the RF test signal at the time the sample is acquired from the mixer. This sampling can be performed, for example, by an ADC.

[0086] In step 260, a Discrete Fourier Transform (DFT) is applied to the digital sample value sequence to generate multiple DFT bin values. Each DFT bin value corresponds to a different harmonic present in the digital sample value sequence. The DFT bin value includes at least the DC amplitude value of the sample value sequence (i.e., the zeroth harmonic amplitude value), the first harmonic amplitude value of the sample value sequence, and the third harmonic amplitude value of the sample value sequence.

[0087] In step 270, a defect in the phase shifter is identified based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0088] For example, if the amplitude of the first harmonic is much greater than the amplitudes of the DC amplitude and the third harmonic amplitude, this will indicate that the phase shifter is operating normally. If this is not the case, then the relative proportions between the amplitudes of the DC amplitude, the first harmonic amplitude, and the third harmonic amplitude indicate a fault, and may also indicate the type and / or source of the fault.

[0089] In other words, if the phase shifter malfunctions, the DC and third harmonic components may become excessively large and / or the first harmonic component may become unacceptably small. Therefore, these values ​​can be compared to various pass / fail conditions to identify a fault. More specifically, a fault can be identified if the first harmonic amplitude value fails to meet the first harmonic condition, the DC amplitude value meets the DC fault condition, and / or the third harmonic amplitude value meets the third harmonic (i.e., image) fault condition.

[0090] However, the embodiments are not limited thereto, and combinations of DFT values ​​can be processed to identify faults (e.g., the sum of DC amplitude and third harmonic amplitude values, etc.). The conditions for evaluating failure or success can vary depending on the specific application.

[0091] Although not described, the method may then include additional steps: modifying the operation of the phase shifter based on the identified defects. Therefore, the method can provide means for automatic correction / calibration of the phase shifter. Additionally or alternatively, the output signal may be generated based on the identified defects in the phase shifter indicating a fault in the phase shifter.

[0092] It should be noted that the method described above can be derived from... Figure 1 The described controller / processor executes.

[0093] By way of a specific example, the first phase offset is a 0-degree phase offset (i.e., the phase stepper applies a 0-degree offset to the RF reference signal), and the second phase offset is a 90-degree phase offset (i.e., the phase stepper applies a 90-degree offset to the RF reference signal). The test set of phase offsets applied to the RF reference signal by the phase shifter includes 0, 90, 180, and 270-degree phase offsets. Essentially, the process performs the measurement procedure described above, but with the phase stepper applying both 0-degree and 90-degree phase offsets.

[0094] More specifically, for each setting of the phase stepper, four digital sample values ​​will be generated, and thus a total of eight digital sample values ​​will be generated. 1…4This represents the digital signal value associated with a 90-degree test phase shift applied by the phase stepper, while the phase shifter applies each phase shift in the test set (e.g., Sin2 represents the digital sample value generated when both the phase stepper and phase shifter apply a 90-degree phase shift). Cos 1…4 Cos3 represents the digital signal value associated with the phase stepper applying a 0-degree test phase offset, while the phase shifter applies each offset in the phase offset of the test set (i.e., Cos3 represents the digital sample value generated when the phase stepper applies a 0-degree phase offset and the phase shifter applies a 180-degree phase offset).

[0095] In this case, applying the DFT to generate the DFT binary values ​​involves the computation of a four-point complex FFT. Due to the selected phase stepper settings and the choice of the test set for the phase shift in this example, only the summation operand is required, meaning that the process of applying the Fourier transform is computationally efficient and fast.

[0096] Specifically, the DC component can be calculated as follows:

[0097] Re0 = cos1 + cos2 + cos3 + cos4 [3]

[0098] Im0 = sin1 + sin2 + sin3 + sin4 [4]

[0099] The first harmonic component can be calculated as follows:

[0100] Re1 = cos1 + sin2 - cos3 - sin4 [5]

[0101] Im1 = sin1 - cos2 - sin3 + cos4 [6]

[0102] The third harmonic component can be calculated as follows:

[0103] Re3 = cos1 - sin2 - cos3 + sin4 [7]

[0104] Im3 = sin1 + cos2 - sin3 - cos4 [8]

[0105] Therefore, by applying a simple arithmetic function to the voltage represented by digital sample values, various harmonic components can be directly derived from cos... 1…4 and sin 1…4 It is derived from the signal.

[0106] As demonstrated, the main advantage of the extended process is that no additional measurements are required to monitor the correct functioning of the phase shifter, apart from repeated measurements for both phase stepper settings. In other words, it is not necessary to cycle through every used setting of the phase shifter to determine its correct operation. Essentially, the number of measurements required to derive the phase shifter's performance is minimized. Therefore, the additional power consumption required for monitoring is minimized.

[0107] In addition to the examples described above, the following examples are disclosed.

[0108] Example 1 is an RF transmitter device, comprising:

[0109] A phase shifter is configured to receive an RF reference signal and to generate an RF transmit signal based on one of a plurality of phase shifts applied to the RF reference signal.

[0110] A coupler is configured to couple an RF transmitted signal to a transmit antenna and to couple out a portion of the RF transmitted signal to generate an RF feedback signal;

[0111] A binary phase stepper is configured to receive an RF reference signal and generate an RF test signal, wherein the phase stepper is configured to be operable in a first mode and a second mode, wherein in the first mode the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal, and in the second mode the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, the first phase offset being different from the second phase offset; and

[0112] The mixer is configured to receive an RF test signal and an RF feedback signal, and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

[0113] Example 2 is an RF transmitter device of Example 1, and further includes:

[0114] An analog-to-digital converter (ADC) is configured to sample the mixer output signal to generate digital sample values; and

[0115] The controller is configured as follows:

[0116] While the binary phase stepper operates in the first mode, the control phase shifter generates a first RF transmit signal sequence, each RF transmit signal being based on a phase shift in a test set applied to the RF reference signal; and

[0117] The ADC is controlled to sample the mixer output at a first plurality of sampling times to provide a first digital sample value sequence, wherein each digital sample value in the first digital sample value sequence corresponds to a corresponding RF transmit signal in a first RF transmit signal sequence.

[0118] Example 3 is an RF transmitter device of Example 2, and further includes a processor configured to receive a first digital sample value sequence and generate phase and amplitude information of an RF transmitted signal based on the result of processing the first digital sample value sequence with a DFT.

[0119] Example 4 is an RF transmitter device of Example 3, wherein the processor is further configured to: modify the operating parameters of the phase shifter based on the generated phase and amplitude information and / or generate a signal indicating a fault in the phase shifter.

[0120] Example 5 is an RF transmitter device of any one of Examples 2 to 4, wherein the controller is further configured as follows:

[0121] While the binary phase stepper operates in the second mode, the control phase shifter generates a second RF transmit signal sequence by applying each of a plurality of phase shifts; and

[0122] The ADC is controlled to sample the mixer output at a second plurality of sampling times to provide a second sequence of digital sample values, wherein each digital sample value in the second sequence of digital sample values ​​corresponds to a corresponding RF transmit signal in the second sequence of RF transmit signals.

[0123] Example 6 is an RF transmitter device of Example 5, and also includes a processor configured to:

[0124] Receive the first digital sample value sequence and the second digital sample value sequence; and

[0125] A DFT is applied to a first digital sample value sequence and a second digital sample value sequence to generate multiple DFT bin values, each DFT bin value corresponding to a different harmonic present in the first digital sample value sequence and the second digital sample value sequence.

[0126] Example 7 is an RF transmitter device of Example 6, wherein the DFT bin value includes the DC amplitude value of the sample value sequence, the first harmonic amplitude value of the sample value sequence, and the third harmonic amplitude value of the sample value sequence. In this case, the processor is also configured to identify a defect in the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

[0127] Example 8 is an RF transmitter device of Example 7, wherein the processor is further configured to generate an error signal in response to an identified DC amplitude value satisfying a DC fault condition, an identified first harmonic amplitude value satisfying a first harmonic condition, and / or an identified third harmonic amplitude value satisfying a third harmonic fault condition.

[0128] Example 9 is an RF transmitter device of either Example 7 or 8, wherein the processor is further configured to: modify the operating parameters of the phase shifter based on the identified defect of the phase shifter and / or generate a signal indicating the failure of the phase shifter.

[0129] Example 10 is an RF transmitter device of any of Examples 3 to 9, wherein applying DFT includes: analytically processing a sequence of digital sample values ​​using only arithmetic and geometric functions and / or approximations.

[0130] Example 11 is an RF transmitter device of any of Examples 1 to 10, wherein the difference between the first phase offset and the second phase offset of the binary phase stepper is 90 degrees.

[0131] Example 12 is an RF transmitter device of any of Examples 1 to 11, wherein the test set of phase offsets includes equidistant phase offsets.

[0132] Example 13 is a method for evaluating the performance of an RF transmitter device. The RF transmitter device includes: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on one of a plurality of phase shifts applied to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and couple out a portion of the RF transmit signal to generate an RF feedback signal; a phase stepper configured to receive the RF reference signal and generate an RF test signal based on one or more test phase shifts applied to the RF reference signal; and a mixer configured to receive the RF test signal and the RF feedback signal and mix the RF test signal and the RF feedback signal to generate a mixer output signal. The method includes:

[0133] While the phase stepper applies a first phase shift to the RF reference signal, the phase shifter is controlled to generate a first RF transmit signal sequence, each of the RF transmit signals being based on each phase shift in the test set for which a phase shift is applied to the RF reference signal;

[0134] While the phase stepper applies a second phase offset to the RF reference signal, the phase shifter is controlled to generate a second RF transmit signal sequence, each of the RF transmit signals being based on each phase offset in the test set for which a phase offset is applied to the RF reference signal;

[0135] The mixer output is sampled at multiple sampling times to provide a sequence of digital sample values, wherein each digital sample value in the sequence corresponds to a corresponding RF transmit signal in a first RF transmit signal sequence or a corresponding RF transmit signal in a second RF transmit signal sequence.

[0136] A Discrete Fourier Transform (DFT) is applied to a sequence of digital sample values ​​to generate multiple DFT bin values, each corresponding to a different harmonic present in the sequence. These DFT bin values ​​include the DC amplitude of the sample value sequence, the amplitude of the first harmonic of the sample value sequence, and the amplitude of the third harmonic of the sample value sequence; and

[0137] The defect of the phase shifter is identified based on at least one of the identified DC amplitude value, first harmonic amplitude value, and third harmonic amplitude value.

[0138] Example 14 is the method of Example 13, and also includes: modifying the phase shifter based on the identified defects of the phase shifter.

[0139] Example 15 is a method of Example 13 or 14, further comprising: generating an output signal indicating a fault in the phase shifter based on the identified defect in the phase shifter.

[0140] Example 16 is a method of any of Examples 13 to 15, further comprising: generating phase and amplitude information of an RF transmitted signal based on the result of processing a sequence of digital sample values ​​using a DFT.

[0141] Example 17 is a method of any of Examples 13 through 16, wherein the test set of phase offsets includes equidistant phase offsets.

[0142] Example 18 is a method of any one of Examples 13 to 17, wherein the phase stepper is a binary phase stepper configured to be operable in a first mode and a second mode, wherein in the first mode, the phase stepper generates an RF test signal based on applying a first phase offset to an RF reference signal, and in the second mode, the phase stepper generates an RF test signal based on applying a second phase offset to an RF reference signal. The method further includes:

[0143] The phase stepper is controlled to operate in a first mode, while the phase shifter is controlled to generate a first RF transmit signal sequence; and

[0144] The phase stepper is controlled to operate in the second mode, while the phase shifter is controlled to generate a second RF transmit signal sequence.

[0145] Example 19 is the method of Example 18, where the difference between the first phase offset and the second phase offset in the binary phase stepper is 90 degrees.

[0146] Although specific examples have been illustrated and described herein, those skilled in the art will understand that various alternative and / or equivalent embodiments may be used instead of the specific examples shown and described without departing from the scope of the invention. This application is intended to cover any modifications or variations of the specific examples discussed herein. Therefore, the invention is intended to be limited only by the claims and their equivalents.

[0147] It should be noted that the methods and apparatuses, including their preferred embodiments as outlined in this document, can be used alone or in combination with other methods and apparatuses disclosed in this document. Furthermore, the features outlined in the context of the apparatus also apply to the corresponding methods, and vice versa. Moreover, all aspects of the methods and apparatuses outlined in this document can be combined arbitrarily. In particular, the features of the claims can be combined with each other in any manner.

[0148] It should be noted that the specification and drawings merely illustrate the principles of the proposed methods and systems. Those skilled in the art will be able to implement various devices, which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and embodiments outlined in this document are primarily intended for illustrative purposes only to aid the reader's understanding of the principles of the proposed methods and systems. In addition, all statements regarding the principles, aspects, and embodiments of the invention, as well as specific examples thereof, provided herein are intended to cover their equivalents.

[0149] In the claims, any reference numerals placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims. The words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. This embodiment can be implemented by means of hardware comprising several different elements. In an apparatus claim enumerating several means, several of these means may be embodied by a single means and the same hardware. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used. Furthermore, the inclusion of "at least one of: A; B; and C" in the appended claims should be interpreted as (A and / or B) and / or C.

Claims

1. A radio frequency (RF) transmitter apparatus comprising: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal; a binary phase stepper configured to receive the RF reference signal and to generate an RF test signal, wherein the phase stepper is configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal and a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, the first phase offset being different from the second phase offset; and a mixer configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal.

2. The RF transmitter apparatus of claim 1, further comprising: an analog-to-digital converter (ADC) configured to sample the mixer output signal to generate digital sample values; and a controller configured to: control the phase shifter to generate a first sequence of RF transmit signals while the binary phase stepper is operating in the first mode, each of the RF transmit signals being based on each phase offset of a test set of phase offsets applied to the RF reference signal; and control the ADC to sample the mixer output at a first plurality of sampling times so as to provide a first sequence of digital sample values, wherein each digital sample value of the first sequence of digital sample values corresponds to a respective one of the first sequence of RF transmit signals.

3. The RF transmitter apparatus of claim 2, further comprising a processor configured to receive the first sequence of digital sample values and to generate phase and amplitude information for the RF transmit signal based on results of processing the first sequence of digital sample values with a discrete Fourier transform (DFT).

4. The RF transmitter apparatus of claim 3, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or to generate a signal indicative of a fault of the phase shifter based on the generated phase and amplitude information.

5. The RF transmitter apparatus of any one of claims 2 to 4, wherein the controller is further configured to: control the phase shifter to generate a second sequence of RF transmit signals by applying each of the plurality of phase offsets while the binary phase stepper is operating in the second mode; and ​ ​ controlling the ADC to sample the mixer output at a second plurality of sampling times so as to provide a second sequence of digital sample values, wherein each digital sample value in the second sequence of digital sample values corresponds to a respective one of the second sequence of RF transmit signals.

6. The RF transmitter apparatus of claim 5, further comprising a processor configured to: receive the first sequence of digital sample values and the second sequence of digital sample values; and apply a DFT to the first sequence of digital sample values and the second sequence of digital sample values to generate a plurality of DFT bin values, each DFT bin value corresponding to a different harmonic present in the first sequence of digital sample values and the second sequence of digital sample values.

7. The RF transmitter apparatus of claim 6, wherein the DFT bin values include a DC amplitude value of the sample value sequence, a first harmonic amplitude value of the sample value sequence, and a third harmonic amplitude value of the sample value sequence, and wherein the processor is further configured to identify a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

8. The RF transmitter apparatus of claim 7, wherein the processor is further configured to generate an error signal in response to the identified DC amplitude value satisfying a DC fault condition, the identified first harmonic amplitude value satisfying a first harmonic condition, and / or the identified third harmonic amplitude value satisfying a third harmonic fault condition.

9. The RF transmitter apparatus of claim 7 or 8, wherein the processor is further configured to modify an operating parameter of the phase shifter and / or generate a signal indicating a fault of the phase shifter based on the identified defect of the phase shifter.

10. The RF transmitter apparatus of any one of claims 3 to 9, wherein applying the DFT comprises: analytically processing the sequence of digital sample values using only arithmetic and geometric functions and / or approximations.

11. The RF transmitter apparatus of any one of claims 1 to 10, wherein a difference between the first phase offset and the second phase offset of the binary phase stepper is 90 degrees.

12. The RF transmitter apparatus of any one of claims 1 to 11, wherein the test set of phase offsets includes equidistant phase offsets.

13. A method for evaluating performance of a radio frequency (RF) transmitter device, the RF transmitter device comprising: a phase shifter configured to receive an RF reference signal and configured to generate an RF transmit signal based on applying one of a plurality of phase offsets to the RF reference signal; a coupler configured to couple the RF transmit signal to a transmit antenna and to couple out a portion of the RF transmit signal to generate an RF feedback signal; a phase stepper configured to receive the RF reference signal and to generate an RF test signal based on applying one or more test phase offsets to the RF reference signal; and a mixer configured to receive the RF test signal and the RF feedback signal and to mix the RF test signal and the RF feedback signal to generate a mixer output signal, the method comprising: controlling the phase shifter to generate a first sequence of RF transmit signals while the phase stepper applies a first phase offset to the RF reference signal, each of the RF transmit signals being based on each phase offset of a test set of phase offsets applied to the RF reference signal; controlling the phase shifter to generate a second sequence of RF transmit signals while the phase stepper applies a second phase offset to the RF reference signal, each of the RF transmit signals being based on each phase offset of the test set of phase offsets applied to the RF reference signal; sampling the mixer output at a plurality of sampling times so as to provide a sequence of digital sample values, wherein each of the sequence of digital sample values corresponds to a respective one of the first sequence of RF transmit signals or the second sequence of RF transmit signals; applying a discrete Fourier transform (DFT) to the sequence of digital sample values to generate a plurality of DFT bin values, each DFT bin value corresponding to a different harmonic present in the sequence of digital sample values, wherein the DFT bin values include a DC amplitude value of the sequence of sample values, a first harmonic amplitude value of the sequence of sample values, and a third harmonic amplitude value of the sequence of sample values; and identifying a defect of the phase shifter based on at least one of the identified DC amplitude value, the first harmonic amplitude value, and the third harmonic amplitude value.

14. The method of claim 13, further comprising: modifying operation of the phase shifter based on the identified defect of the phase shifter.

15. The method of claim 13 or 14, further comprising: generating an output signal indicative of a failure of the phase shifter based on the identified defect of the phase shifter.

16. The method of any one of claims 13-15, further comprising: generating phase and amplitude information of the RF transmit signals based on results of processing the sequence of digital sample values with the DFT.

17. The method of any one of claims 13 to 16, wherein the test set of phase offsets includes equidistant phase offsets.

18. The method of any one of claims 13 to 17, wherein the phase stepper is a binary phase stepper configured to be operable in a first mode in which the phase stepper generates the RF test signal based on applying a first phase offset to the RF reference signal and a second mode in which the phase stepper generates the RF test signal based on applying a second phase offset to the RF reference signal, and wherein the method comprises: controlling the phase stepper to operate in the first mode while the phase shifter is controlled to generate the first sequence of RF transmit signals; and controlling the phase stepper to operate in the second mode while the phase shifter is controlled to generate the second sequence of RF transmit signals.

19. The method of claim 18, wherein a difference between the first phase offset and the second phase offset of the binary phase stepper is 90 degrees. ​

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