Patent Description:
RF signals transmitted from a transmitter circuit based on a high carrier frequency oscillator are frequently received at a receiver circuit based on a local high carrier frequency oscillator, where the carrier frequency of the transmitter oscillator and the carrier frequency of the receiver oscillator are slightly different. The carrier frequency offset (CFO) causes errors in traditional techniques for determining AoA or AoD. Techniques for accurately calculating AoA or AoD in the presence of CFO are needed in the art.

Aspects of the invention are defined in the appended claims.

A receiver circuit (<NUM>) for calculating AoD is disclosed according to claim <NUM>.

A method of using the receiver circuit for calculating AoD is disclosed according to claim <NUM>.

A receiver circuit (<NUM>) for calculating AoA is disclosed according to claim <NUM>.

A method of using the receiver circuit for calculating AoA is disclosed according to claim <NUM>.

In the following, each of the described methods, apparatuses, examples and aspects which does not fully correspond to the invention as defined in the claims is to be considered as not in accordance with the invention and is, as well as the whole following description, present for illustration purposes only or to highlight specific aspects or features of the claims.

Particular embodiments of the disclosure are illustrated herein in conjunction with the drawings. Particular embodiments of the disclosure are illustrated herein in conjunction with the drawings.

Embodiments illustrate circuits and methods for determining a measured angle of arrival (AoA) or angle of departure (AoD) of a signal received at a receiver circuit having multiple antennas generating signals which are digitized with a single RF chain. The AoA or AoD is determined based on a number of signal samples for each of one or more sampling times. Because the RF chain can generate only one sample per sampling time, the other samples for each sampling time are calculated. <FIG> respectively illustrate schematic diagrams of a receiver circuit and a transmitter circuit. <FIG> respectively illustrate AoA and AoD. <FIG> illustrate received and calculated samples used for determining AoA or AoD. <FIG> is a block illustrating a system using an array of N antennas.

<FIG> is a schematic diagram of an embodiment of a transmitter circuit <NUM> according to an embodiment. Transmitter circuit <NUM> includes antenna or antenna array <NUM>, switch <NUM>, RF chain <NUM>, and controller <NUM>. Transmitter circuit <NUM> illustrates a particular example. Other embodiments of transmitter circuits may be used.

Antenna or antenna array <NUM> may be any antenna or antenna array. For example, in some embodiments, antenna or antenna array <NUM> includes <NUM>, <NUM>, <NUM>, <NUM>, or more antennas. In some embodiments, antenna or antenna array <NUM> includes a linear antenna array. In some embodiments, antenna or antenna array <NUM> includes a two dimensional antenna array, for example, having multiple rows of linear antenna arrays.

In embodiments where antenna or antenna array <NUM> includes one antenna, the one antenna is connected directly to RF chain <NUM>, and switch <NUM> may be omitted. In embodiments where antenna or antenna array <NUM> includes multiple antennas, each antenna is directly connected to a separate RF chain. Each of the RF chains may have the features of RF chain <NUM>.

Antenna or antenna array <NUM> is configured to transmit RF signals to a receiver circuit, such as receiver circuit <NUM> described below with reference to <FIG>. The RF signals include a high frequency signal at a carrier frequency modulated with a low frequency information signal. The high frequency signal is transmitted by one of the antennas from antenna or antenna array <NUM>, for example, according to a programmable electrical connection formed by switch <NUM>, as controlled by controller <NUM>. At least because of reflections, a particular signal transmitted by transmitter circuit <NUM> may arrive at the receiver after having traversed each of multiple transmission paths. Each of the transmission paths may terminate at the receiver with a different AoA. Additionally, the RF signals transmitted by antenna or antenna array <NUM> is transmitted from transmitter <NUM> with an AoD.

Controller <NUM> is configured to provide a digital signal to RF chain <NUM>, where the digital signal encodes the information signal to be transmitted by antenna or antenna array <NUM>.

RF chain <NUM> includes digital to analog converter (DAC) <NUM>, mixer <NUM>, frequency synthesizer <NUM>, and power amplifier (PA) <NUM>. RF chain <NUM> is an example only, and embodiments of other RF chains may alternatively be used. For example, in some embodiments, one or more amplifiers, and/or filters may be included, as understood by those of skill in the art.

The digital signal is processed by the digital to analog converter <NUM> to generate an analog baseband signal representing the digital signal, using techniques known in the art. Various digital to analog converter structures known in the art may be used.

Mixer <NUM> receives the analog baseband signal output from the digital to analog converter <NUM> and an oscillator signal at the carrier frequency generated by frequency synthesizer <NUM>. In response to the analog baseband signal and the oscillator signal, mixer <NUM> up converts the analog baseband signal from the analog-to-digital converter <NUM> to a high frequency signal, using techniques known in the art. Various mixer structures known in the art may be used. The resulting high frequency signal is at the carrier frequency in this modulated so as to include the information of the low frequency information signal.

Power amplifier <NUM> is configured to receive the high frequency signal the high frequency signal is driven to one of the antennas from antenna or antenna array <NUM>, for example, according to a programmable electrical connection formed by switch <NUM>, as controlled by controller <NUM>. The power amplifier <NUM> drives the high frequency signal to one of the antennas using techniques known in the art. Various power amplifier structures known in the art may be used.

As understood by those of skill in the art, using communication connectivity not illustrated in <FIG>, control signals from controller <NUM> may control certain variable functionality of switch <NUM>, power amplifier <NUM>, frequency synthesizer <NUM>, mixer <NUM>, and digital to analog converter <NUM>, for example, as understood by those of skill in the art.

The control signals from controller <NUM>, for example, control switch <NUM> to control which of multiple antennas RF chain <NUM> drives the high frequency signal with.

In embodiments having multiple antennas each connected to one of multiple RF chains, controller <NUM> generate control signals for each of the RF chains.

<FIG> is a schematic diagram of an embodiment of a receiver circuit <NUM> according to an embodiment. Receiver circuit <NUM> includes antenna or antenna array <NUM>, switch <NUM>, RF chain <NUM>, and controller <NUM>.

In embodiments where antenna or antenna array <NUM> includes one antenna, the one antenna is connected directly to RF chain <NUM>, and switch <NUM> is omitted. In embodiments where antenna or antenna array <NUM> includes multiple antennas, each antenna is directly connected to a separate RF chain. Each of the RF chains may have the features of RF chain <NUM>.

Antenna or antenna array <NUM> is configured to receive RF signals generated by a transmitter, such as transmitter <NUM> described above with reference to <FIG>. At least because of reflections, a particular signal transmitted by the transmitter may arrive at the antenna or antenna array <NUM> after having traversed each of multiple transmission paths. Each of the transmission paths may terminate at the antenna or antenna array <NUM> with a different AoA. Additionally, the RF signals transmitted by the transmitter <NUM> is transmitted with an AoD.

RF chain <NUM> includes low noise amplifier (LNA) <NUM>, frequency synthesizer <NUM>, mixer <NUM>, and analog to digital converter (ADC) <NUM>. RF chain <NUM> is an example only, and embodiments of other RF chains may alternatively be used. For example, in some embodiments, one or more amplifiers, and/or filters may be included, as understood by those of skill in the art.

Low noise amplifier <NUM> is configured to receive a high frequency signal at a carrier frequency and modulated with a low frequency information signal. The high frequency signal is received from one of the antennas from antenna or antenna array <NUM>, for example, according to a programmable electrical connection formed by switch <NUM>, as controlled by controller <NUM>. The high frequency signal is amplified by low noise amplifier <NUM> to generate an amplified RF signal, using techniques known in the art. Various low noise amplifier structures known in the art may be used.

Mixer <NUM> receives the amplified RF signal output from the low noise amplifier <NUM> and an oscillator signal at or substantially at the carrier frequency generated by frequency synthesizer <NUM>. In response to the amplified RF signal and the oscillator signal, mixer <NUM> down converts the amplified RF signal from the low noise amplifier <NUM> to a baseband signal, using techniques known in the art. Various mixer structures known in the art may be used. The resulting baseband signal includes information of the low frequency information signal.

The baseband signal is then processed by the analog-to-digital converter <NUM> to generate a digital signal representing the baseband signal, using techniques known in the art. Various analog-to-digital converter structures known in the art may be used.

Controller <NUM> receives the digital representation of the baseband signal.

As understood by those of skill in the art, using communication connectivity not illustrated in <FIG>, control signals from controller <NUM> may control certain variable functionality of switch <NUM>, low noise amplifier <NUM>, frequency synthesizer <NUM>, mixer <NUM>, and analog-to-digital converter <NUM>, for example, as understood by those of skill in the art.

The control signals from controller <NUM>, for example, control switch <NUM> to select which of multiple antennas RF chain <NUM> receives the high frequency signals from.

For example, controller <NUM> generates control signals which result in controller <NUM> receiving a group of digital signals, where each digital signal of the group is generated by RF chain <NUM> based on a high frequency signal received by a selected one of the antennas. In embodiments having multiple antennas each connected to one of multiple RF chains, controller <NUM> generates control signals for each of the RF chains, such that controller <NUM> receives a group of digital signals, where each digital signal of the group is generated by one of the RF chains based on an RF signal received by the particular antenna connected thereto. Using techniques described below, controller <NUM> is configured to store the group of digital signals in a memory, and to determine an AoA or AoD for the received RF signals based on the group of digital signals it receives.

<FIG> is a schematic diagram illustrating the geometry of phase-based estimation of angle of arrival (AoA) of an RF signal received at an antenna array comprising antenna A1 and antenna A2.

As shown, the transmitted RF signal is received at an angle of arrival (AoA) θ at antennas A1 and A2. According to geometric and trigonometric principles understood by those of skill in the art, <MAT> where.

Using techniques known to those of skill in the art, a controller, such as controller <NUM> of receiver circuit <NUM> of <FIG>, calculates AoA.

For example, an embodiment of receiver circuit <NUM> having one RF chain for each of antennas A1 and A2, assuming no carrier frequency offset, may calculate AoA as follows:.

The downconverted sample received at antenna A1 is: <MAT> where:
t<NUM> = the time of the receiver oscillator.

The downconverted sample received at antenna A2 is: <MAT>.

The phase difference is: <MAT> <MAT> as discussed above.

Alternatively, an embodiment of receiver circuit <NUM> having one RF chain for both antennas A1 and A2, assuming no carrier frequency offset, may calculate AoA as follows:.

The phase difference is: <MAT> Therefore, ϕ<NUM> - ϕ<NUM> = (-<NUM>πfh (t<NUM> - t<NUM>) - <NUM>πfl (t<NUM> + T) + ϕ<NUM>) - (-<NUM>πfh (t<NUM> - t<NUM>) - <NUM>πfl t<NUM> + ϕ<NUM>) + <NUM>πfl T.

Accordingly, the phase difference for calculating AoA (ϕ<NUM> - ϕ<NUM>) is equal to the phase difference measured + <NUM>πfl T <MAT> as discussed above.

<FIG> is a schematic diagram illustrating the geometry of phase-based estimation of angle of departure (AoD) of an RF signal transmitted by an antenna array comprising antenna A1 and antenna A2.

As shown, the RF signal is transmitted at an angle of departure (AoD) θ from antennas A1 and A2. According to geometric and trigonometric principles understood by those of skill in the art, <MAT> where.

Using techniques known to those of skill in the art, a controller, such as controller <NUM> of receiver circuit <NUM> of <FIG>, calculates AoD.

For example, an embodiment of receiver circuit <NUM> having one RF chain and a single antenna A1, assuming no carrier frequency offset, may calculate AoD as follows:.

The downconverted first sample is: <MAT> where:
t<NUM> = the time of the receiver oscillator.

The downconverted second sample is: <MAT>.

The phase difference is: <MAT> Therefore, ϕ<NUM> - ϕ<NUM> = (-<NUM>πfh (t<NUM> - t<NUM>) - <NUM>πfl(t<NUM> + T) + ϕ<NUM>) - (-<NUM>πfh (t<NUM> - t<NUM>) - <NUM>πflt<NUM> + ϕ<NUM>) + <NUM>πfl T.

Accordingly, the phase difference for calculating AoD ϕ<NUM> - ϕ<NUM>) is equal to the phase difference measured + <NUM>πfl T. <MAT> as discussed above.

<FIG> is a graphic illustration of digitized samples of a received RF signal according to an example embodiment. The received RF signal are received by a receiver circuit, such as receiver circuit <NUM> of <FIG>, having first and second receive antennas A1 and A2, and are used to calculate AoA. Alternatively, the received RF signal is transmitted by a transmitter circuit, such as transmitter circuit <NUM> of <FIG>, having first and second transmit antennas A1 and A2, and is used for calculating AoD.

The discussion will refer to antennas A1 and A2. It will be understood, based on the usage context, whether the referenced antennas A1 and A2 are transmit antennas or are receive antennas.

The received RF signal is received by the receiver circuit, which generates digitized samples of the received RF signal using techniques discussed above and/or other techniques known to those of skill in the art.

Because the received RF signal is time multiplexed either when transmitted with transmit antennas A1 and A2 or received with receive antennas A1 and A2, each sampling time T1-T6 has a single digitized sample. The receiver circuit generates a digitized sample y1 for the first sampling time T1 based on the received RF signal transmitted or received with antenna A1. The receiver circuit generates a digitized sample y2 for the second sampling time T2 based on the received RF signal transmitted or received with antenna A2. The receiver circuit generates a digitized sample y3 for the third sampling time T3 based on the received RF signal transmitted or received with antenna A1. The receiver circuit generates a digitized sample y4 for the fourth sampling time T4 based on the received RF signal transmitted or received with antenna A2. The receiver circuit generates a digitized sample y5 for the fifth sampling time T5 based on the received RF signal transmitted or received with antenna A1. The receiver circuit generates a digitized sample y6 for the sixth sampling time T6 based on the received RF signal transmitted or received with antenna A2.

As understood by those of skill in the art, sampling times is spaced apart by a switching time, during which, for example, either the transmitter circuit disconnects an amplifier from one of transmit antennas A1 and A2 and connects the amplifier to the other of transmit antennas A1 and A2, or the receiver circuit disconnects an amplifier from one of receive antennas A1 and A2 and connects the amplifier to the other of receive antennas A1 and A2.

The digital samples generated by the receiver circuit are used to calculate AoA or AoD. However, because calculations of AoA or AoD are made with digitized samples for the same sampling time, additional digital samples are calculated based on the digitized samples generated by the RF chain of the receiver circuit.

<FIG> is a graphic illustration of received and calculated samples which are used for calculating AoA or AoD. Samples y1 of sampling time T1, y3 of sampling time T3, and y5 of sampling time T5, are generated by the receiver circuit by digitizing the received RF signal of transmit or receive antenna A1 using techniques discussed elsewhere herein, or using other techniques understood by those of skill in the art. Similarly, samples y2 of sampling time T2, y4 of sampling time T4, and y6 of sampling time T6 are generated by the receiver circuit by digitizing the received RF signal of transmit or receive antenna A2 using techniques discussed elsewhere herein, or using other techniques understood by those of skill in the art. In addition, samples ylc2 of sampling time T1, y2c1 of sampling time T2, y3c2 of sampling time T3, y4c1 of sampling time T4, y5c2 of sampling time T5, and y6c1 of sampling time T6 are calculated by the receiver circuit based on digitized samples of the received RF signal using techniques discussed elsewhere herein, or using other techniques understood by those of skill in the art.

In some embodiments, samples ylc2 of sampling time T1, y3c2 of sampling time T3, and y5c2 of sampling time T5 are calculated based on digitized samples of the received RF signal transmitted or received by antenna A2. For example, samples ylc2 of sampling time T1, y3c2 of sampling time T3, and y5c2 of sampling time T5 may be calculated based at least in part on digitized sample y2 of sampling time T2, digitized sample y4 of sampling time T4, and digitized sample y6 of sampling time T6.

For example, a first digital input signal including digitized sample y2 of sampling time T2, digitized sample y4 of sampling time T4, and digitized sample y6 of sampling time T6 may be input to a digital filter, such as a first digital FIR filter. Any suitable digital FIR filter may be used.

As understood by those of skill in the art, as part of the filtering process, the first digital FIR filter oversamples the first digital signal input thereto, and , consequently, generates digital samples corresponding with times between the sampling times of the digitized samples of the first digital input signal.

For example, the first digital input signal including digitized sample y2 of sampling time T2, digitized sample y4 of sampling time T4, and digitized sample y6 of sampling time T6 may be input to the first digital FIR oversampling by a factor of <NUM>. Based at least in part on digitized sample y2, digitized sample y4, and digitized sample y6 of the first digital input signal, the first digital FIR filter may calculate samples ylc2 of sampling time T1, y3c2 of sampling time T3, and y5c2 of sampling time T5, as illustrated in <FIG>.

In some embodiments, y2c1 of sampling time T2, y4c1 of sampling time T4, and y6c1 of sampling time T6 are calculated based on digitized samples of the received RF signal transmitted or received by antenna A1. For example, samples y2c1 of sampling time T2, y4c1 of sampling time T4, and y6c1 of sampling time T6 may be calculated based on digitized sample y1 of sampling time T1, digitized sample y3 of sampling time T3, and digitized sample y5 of sampling time T5.

For example, a second digital input signal including digitized sample y1 of sampling time T1, digitized sample y3 of sampling time T3, and digitized sample y5 of sampling time T5 may be input to a digital filter, such as a second digital FIR filter. Any suitable digital FIR filter may be used.

As understood by those of skill in the art, as part of the filtering process, the second digital FIR filter may oversample the digital signal input thereto, and may, consequently, generate digital samples corresponding with times between the sampling times of the digitized samples of the second digital input signal.

For example, the second digital input signal including digitized sample y1 of sampling time T1, digitized sample y3 of sampling time T3, and digitized sample y5 of sampling time T5 may be input to the second digital FIR oversampling by a factor of <NUM>. Based at least in part on digitized sample y1, digitized sample y3, and digitized sample y5 of the second digital input signal, the digital FIR filter may calculate samples y2c1 of sampling time T2, y4c1 of sampling time T4, and y6c1 of sampling time T6, as illustrated in <FIG>.

Using techniques discussed herein, and/or other techniques known to those of skill in the art, the receiver circuit calculates a measured AoA or AoD based on the digitized and calculated samples illustrated in <FIG>.

For example, a measured AoA or AoD may be calculated based on the digitized and calculated samples of multiple sampling times according to, for example, a Multiple Signal Classification (MUSIC) AoA or AoD algorithm, as understood by those of skill in the art.

Alternatively, an estimate of AoA or AoD may be calculated for each sampling time. For example, each of sample pairs y1 and ylc2, y2c1 and y2, y3 and y3c2, y4c1 and y4, y5 and y5c2, and y6c1 and y6 may be used to calculate an estimate of AoA or AoD. In addition, the calculated estimates of AoA or AoD may be used to calculate a measured AoA or AoD using any of the techniques described herein and/or any other techniques known to those of skill in the art. For example, the measured AoA or AoD may be calculated as an average of the estimates of AoA or AoD.

<FIG> is a graphic illustration of digitized samples of a received RF signal according to an example embodiment. The received RF signal are received by a receiver circuit, such as receiver circuit <NUM> of <FIG>, having receive antennas A1-AN, and are used to calculate AoA. Alternatively, the received RF signal are transmitted by a transmitter circuit, such as transmitter circuit <NUM> of <FIG>, having antennas A1-AN, and are used for calculating AoD.

The discussion will refer to antennas A1-AN. It will be understood, based on the usage context, whether the referenced antennas A1-AN are transmit antennas or are receive antennas.

Because the received RF signal is time multiplexed either when transmitted with transmit antennas A1-AN or received with receive antennas A1-AN, each sampling time T1-TN has a single digitized sample. The receiver circuit generates a digitized sample y1 for the first sampling time T1 based on the received RF signal transmitted or received with antenna A1. The receiver circuit generates a digitized sample yN for the Nth sampling time TN based on the received RF signal transmitted or received with antenna AN. The receiver circuit generates another digitized sample yx for each of the other sampling times Tx between T1 and TN based on the received RF signal transmitted or received with an antenna Ax. As understood by those of skill in the art, the receiver circuit continues to generate samples based on the received RF signal with a repeating pattern of the sample generation scheme illustrated in <FIG>.

As understood by those of skill in the art, sampling times may be spaced apart by a switching time, during which, for example, either the transmitter circuit disconnects an amplifier from one of the transmit antennas A1-AN and connects the amplifier to a next transmit antenna, or the receiver circuit disconnects an amplifier from one of receive antennas A1-AN and connects the amplifier to a next receive antennas.

<FIG> is a graphic illustration of received and calculated samples which are used for calculating AoA or AoD. The receiver circuit generates a digitized sample y1 for the first sampling time T1 based on the received RF signal transmitted or received with antenna A1. The receiver circuit generates a digitized sample y2 for the second sampling time T2 based on the received RF signal transmitted or received with antenna A2. The receiver circuit also generates a digitized sample yN-<NUM> for the N-1th sampling time TN-<NUM> based on the received RF signal transmitted or received with antenna AN-<NUM>. The receiver circuit also generates a digitized sample yN for the Nth sampling time TN based on the received RF signal transmitted or received with antenna AN. The receiver circuit generates another digitized sample yx for each of the other sampling times Tx between sampling times T2 and TN-<NUM> based on the received RF signal transmitted or received with an antenna Ax between antennas A2 and AN-<NUM>. As understood by those of skill in the art, the receiver circuit continues to generate samples based on the received RF signal with a repeating pattern of the sample generation scheme illustrated in <FIG>.

In addition, samples ylc2-ylcN of sampling time T1, y2c1, y2cN-<NUM>, and y2cN of sampling time T2, yN-1c1, yN-1c2, and yN to 1cN of sampling time TN-<NUM>, yNc1 to yNcN-<NUM> of sampling time TN, and other samples corresponding with the antennas and sampling times not identified in <FIG> are calculated by the receiver circuit based on digitized samples of the received RF signal using techniques discussed elsewhere herein, or using other techniques understood by those of skill in the art.

In some embodiments, the samples corresponding with each particular antenna are calculated based on digitized samples calculated based on the RF signal transmitted or received by the particular antenna. For example, the samples corresponding with antenna Ax are calculated based on digitized samples calculated based on the RF signal transmitted or received by antenna Ax.

For example, a first digital input signal including digitized sample y1 of sampling time T1 and other digitized samples (not shown) calculated based on the RF signal transmitted or received by antenna A1, for example, of sampling times TN+<NUM>, T2N+<NUM>, etc. (not shown) are input to a digital filter, such as a first digital FIR filter. Any suitable digital FIR filter may be used.

For example, the first digital input signal including digitized sample y1 of sampling time T1 and the other digitized samples may be input to the first digital FIR oversampling by a factor of N. Based on the first digital input signal, the first digital FIR filter may calculate samples y2c1 - yNcl of sampling times T2-TN, as illustrated in <FIG>.

In addition, an xth digital input signal including digitized sample yx of sampling time Tx, and other digitized samples (not shown) calculated based on the RF signal transmitted or received by antenna Ax, for example, of sampling times TN+x, T2N+x, etc. (not shown) may be input to a digital filter, such as a first digital FIR filter. Any suitable digital FIR filter may be used.

As understood by those of skill in the art, as part of the filtering process, the xth digital FIR filter may oversample the digital signal input thereto, and may, consequently, generate digital samples corresponding with times between the sampling times of the digitized samples of the xth digital input signal.

For example, the xth digital input signal including digitized sample yx of sampling time Tx and the other digitized samples may be input to the xth digital FIR oversampling by a factor of N. Based on the xth digital input signal, the xth digital FIR filter may calculate samples for sampling times T1 to Tx-<NUM> and Tx+<NUM> to TN, as illustrated in <FIG>.

Accordingly, N digital filters may be used to calculate samples to be used with the digitized samples of <FIG>.

For example, a measured AoA or AoD may be calculated based on the digitized and calculated samples according to a Multiple Signal Classification (MUSIC) AoA or AoD algorithm, as understood by those of skill in the art.

Alternatively, an estimate of AoA or AoD may be calculated for each sampling time. In addition, the calculated estimates of AoA or AoD may be used to calculate a measured AoA or AoD using any of the techniques described herein and/or any other techniques known to those of skill in the art. For example, the measured AoA or AoD may be calculated as an average of the estimates of AoA or AoD.

The subject matter described herein can be embodied in systems, apparatus, methods, and/or articles depending on the desired configuration.

Claim 1:
A receiver circuit (<NUM>), comprising:
one receiver antenna (<NUM>) configured to receive a plurality of RF signals transmitted from a transmitter circuit (<NUM>) comprising two or more transmit antennas (<NUM>) for calculating a measured angle of departure (AOD);
an RF chain (<NUM>) configured to generate a plurality of digitized samples of the received RF signals; and
a controller (<NUM>) configured to receive the digitized samples, to calculate a plurality of additional samples, and to calculate AoD of the RF signals based on the digitized samples and the additional samples,
wherein a first set of the additional samples is calculated by oversampling a first set of the digitized samples and a second set of the additional samples is calculated by oversampling a second set of the digitized samples, the first set of the digitized samples are samples of the RF signals taken at a plurality of first sample times, the second set of the digitized samples are samples of the RF signals taken at a plurality of second sample times, and each of the first sample times is different from each of the second sample times, each of the first set of the additional samples corresponds with one of the second sample times and each of the second set of the additional samples corresponds with one of the first sample times; and the controller (<NUM>) is further configured to calculate the measured AoD for each one of the first sample times and second sample times based on the digitized samples taken at the same sample time and the additional samples corresponding to the same sample time.