The Unbiased Characteristic of Doppler Frequency in GNSS Antenna Array Processing

Abstract

The antenna array technology, especially the spaced-time array processing (STAP), is one of the effective methods used in Global Navigation Satellite System (GNSS) receivers to refrain the power of jamming and enhance the performance of receivers in the circumstance of interference. However, biases induced to the receiver because of many reasons, including characteristic of antennas, front-end channel electronics, and space-time filtering, are extremely harmful to the high precise positioning of receivers. Although plenty of works have been done to calibrate the antenna and to mitigate these biases, achieving a good performance of antijamming, high accuracy, and low complexity at the same time still remains challenging. Different from existing works, this paper leverages the characteristic of GNSS signal’s Doppler frequency in STAP, which is proven to remain unbiased to solve the problem, even when the nonideal antennas are used and the interference circumstance changes. Since the integration of frequency is carrier phase, the unbiased Doppler frequency leads to an accurate estimation of carrier phase which can be used to calibrate the antenna array without extra apparatus or complicating algorithms. Therefore, a simple Doppler-aid strategy may be developed in the future to solve the difficulty of STAP bias mitigation.

Carrier phase correction for GNSS space‐time array processing based on frequency jerk detection

“…Step 2 Carrier phase correction. The algorithm does the correction by multiply the data with an exponent item whose phase is calculated in Step 5, and this procedure can be denoted in Equation (16). It should be noticed that the initial value of Δϕ is 0, and it remains unchanged unless a new value is calculated in Step 5.…”

“…Therefore, the abnormal PLL error can be concluded to STAP, and the local NCO does not need to be adjusted while the STAP output data should be modified to maintain the tracking loop. So the corresponding Δϕ in Equation ( 15) is estimated using Equation (20), and it can be corrected by inverse shifting as Equation (16).…”

“…A carrier phase correction algorithm for STAP is proposed. In the previous work, we have proved that although the carrier phase is biased after the STAP, the stable value of Doppler frequency that estimated by the tracking loop would not be influenced, but there would be a frequency jerk when the jammers change [16]. Therefore, if the receiver does not accelerate drastically, the proposed algorithm claims that the frequency jerk is due to the STAP, and the induced carrier phase bias can be calculated at the time of jerk using the output of carrier loop discriminator.…”

Distortionless pseudo‐code tracking space–time adaptive processor based on the PI criterion for GNSS receiver

“…One point should be mentioned is that the GNSS signal's frequency is needed to satisfy (8). Fortunately, Xie et al [16] proved that the classical space–time PI processing method will not introduce frequency bias so that the classical space–time PI processing method can be used to estimate the signal frequency.…”

Suppression of Jammer Multipath in GNSS Antenna Array Receiver

“…The interference cancellation technology with antenna array is a common technology for a user terminal because it not only can suppress narrowband interference, but can also suppress wideband interference [9][10][11][12]. The navigation in the transmission process would encounter dense forests or urban canyons, but the interference transmission would encounter the same situation [13]. Hence, not only the signal would be affected by the multipath, but also the multipath would impact the interference transmission [14,15].…”