Testbed for Jamming Performance in Simultaneous Transmit and Receive (STAR) Digital Radio Frequency Memory Jammer

In next generation Wireless Local Area Network (WLAN), increasing spectral efficiency is indispensable in order to provide enhanced throughput. Spectral efficiency can be increased though Simultaneous Transmit and Receive (STR) technology. In this paper, an efficient WLAN transmission scheme using STR technology is proposed. Since STR technology allows simultaneous reception while receiving, at most network throughput can be doubled. However, in order to utilize STR technology, at least two non- interfering parties are required. Railroad communication environment of busy railroad station is able to provide good STR environment with plenty number of non-interfering communication parties. Therefore, the proposed scheme is able to provide very efficient railroad communication scheme.

Code-domain signal processing techniques implemented at radio frequencies (RFs) enable simultaneous transmit and receive (STAR) applications. With direct sequence spread spectrum (DSSS) techniques and RF correlators, transmit (TX) self-interference (SI) is separated from the receive (RX) signal at the antenna interface for STAR. The processing gain inherent in the code-domain approach increases the TX SI rejection in the RF domain to relax filtering and linearity requirements of the RX. A code-domain RX demonstrates 52 dB of TX SI rejection with TX code-notch and RX code-pass filters operating at the same center frequency. The RX is tunable from 0.25 to 1.25 GHz and has a gain of 39 dB at 1 GHz while consuming 90 mW of which 40 mW are consumed in the front-end filters. The RX is implemented in a 45-nm CMOS SOI process and full-duplex operation is verified through an over-the-air demonstration.

We present an actively tuned balun to enable simultaneous transmit and receive (STAR) antennas to achieve greater isolation. Specifically, for the first time, we propose placing a chip into the antenna feed to control the amplitude of the current density. Nearly perfect balance of the feed currents enables STAR antennas to maintain strong isolation despite unpredictable fabrication imperfections. Two identical prototypes were fabricated for comparison, one passive and the other with active tuning inserted. Measurements demonstrate a minimum isolation of 42 dB across a 250 MHz bandwidth, representing an 11 dB improvement over the passive case. This is the best reported transmit/receive isolation enhancement to date. Further, this novel tuning method is significant because it enables STAR antennas with low-cost substrates, such as FR-4, to achieve greater isolation than passive designs. Notably, the balun was tuned across 1.68–1.93 GHz, part of the Federal Communication Commission's AWS-3 spectrum auction. Measurements show good comparison with simulation.

Mitigating self-interference (SI) is vital for advancing simultaneous transmit and receive (STAR) systems. The noise and linearity of the canceller impose limitations on SI power handling. This article proposes a novel dual-path SI cancelling scheme for high-power SI handling. The proposed approach breaks self-interference cancellation (SIC) tradeoffs between operating frequency, SI power handling, and canceller noise/distortion by using a frequency-translated (FT) SI canceller and an auxiliary FT noise-cancelling (NC) path that cancels the noise/distortion from the primary canceller. This approach can work well for both full-duplex (FD) and frequency-division duplex (FDD) schemes. The 65-nm CMOS implementation achieves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 45-dB SIC for 12-dBm receiver (RX) SI peak power (9-dBm avg.) with only 4-dB noise figure (NF) degradation and 207-mW power consumption at 600 MHz. The SIC approach enables a blocker-1 dB with respect to SI of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 16 dBm (8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> higher than prior work) while operating from 0.5 to 1.3 GHz. Therefore, this implementation can support watt-level SI power handling with transmitter (TX)–RX isolation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 15 dB. This is demonstrated through measurements that show 30-dBm TX power handling with 22-dB initial isolation from the circulator.

Aiming at the application of full-duplex (FD) method in phased array for different kinds of waveforms for different functions, based on the modeling of coupling path characteristics for different spatial links using adaptive system identification method, five representative waveforms, including linear frequency modulation (LFM), pseudorandom frequency shift keying (FSK), continuous phase frequency shift keying (CPFSK), dense repeated jamming (DRJ), and wide-band noise (WBN), are designed and applied in full-duplex mode to validate their self-interference cancellation (SIC) performance in practical experiments. From the experiments' results, where the best SIC is about 38dB for LFM, while the worst SIC is just 5∼7dB for DRJ and WBN, we can draw the conclusion that different kinds of waveforms used for different functions can bring on obviously inconsistent SIC, even in the same frequency bandwidth of 300MHz. Thus it can be seen that waveform characteristics used in multifunction phased array play an important role for self-interference cancellation of simultaneous transmit and receive (STAR).

A wideband monostatic simultaneous transmit and receive (STAR) antenna subsystem with high isolation and Co-horizontally polarized (Co-HP) omnidirectional radiation is presented. The antenna subsystem consists of a STAR antenna and a beamforming network (BFN). The STAR antenna consists of a planar circular array having four printed dipole elements surrounded by two groups of parasitic strips. The parasitic strips are used to improve the impedance bandwidth (IMBW) and reduce the gain variation in transmit (TX) and receive (RX) modes. To achieve high isolation, the four ports of the STAR antenna are excited with two orthogonal phase modes for TX and RX using the BFN. The BFN is a six-port network consisting of two 180&#x00B0; hybrid couplers, one 90&#x00B0; hybrid coupler, and a Wilkinson power divider. The 180&#x00B0; hybrid coupler is elaborately designed with low imbalances since it is most key to achieve high TX/RX isolation. Measured results show that the proposed STAR subsystem achieves a TX/RX overlapping IMBW of 4.71&#x2013;6.2 GHz, and a 40 dB TX/RX isolation bandwidth of 4.81&#x2013;5.88 GHz, while maintaining horizontally polarized omnidirectional radiation patterns for TX and RX over the entire operating frequency band.

In this paper, a wideband dual-circularly polarized simultaneous transmit and receive (STAR) antenna is designed at ISM band. Four sequential rotated microstrip patch elements are excited by two sets of feeding networks: the feeding network of transmit (TX) antenna on the top side of the substrate for left hand circular polarization (LHCP), and the feeding network of receive (RX) antenna on the bottom side for right hand circular polarization (RHCP), or vice versa. The parasitic patches with an air gap are used to enlarge the gain bandwidth. The cancellation technique based on the phase cancellation and geometrical symmetry of antenna is employed. The simulation and measurement results show good agreement and demonstrate the good TX/RX isolation of greater than 35 dB across a wide bandwidth of 5–6 GHz. The TX/RX isolation reaches 48.5 dB @ 5.18 GHz, and the axial radio is better than 3 dB across the entire ISM band, which further proves the feasibility of this design methodology and the application in STAR and sensory integration.

We demonstrate a wideband scanning 4-arm spiral antenna array with high transmit/receive isolation for Simultaneous Transmit and Receive (STAR). STAR increases a channel's spectral efficiency by transmitting and receiving across the full bandwidth of a channel. To our knowledge, this is the first STAR array to demonstrate scanning across GHz bandwidths. Each 4-arm spiral element is divided into two arms for transmit and two more for receive. To suppress grating lobes, the element spacing is kept at less than λ/2. A 3×3 array prototype was fabricated and measurements agree well with simulations.

In this communication, a dual-orthogonal-port stacked annular ring microstrip patch antenna for polarization diversity applications and full-duplex communications is presented. Vertical pins that extend from SMA connector inner pins have been employed to implement a port coupling cancellation mechanism and achieve high isolation between the two ports. Furthermore, the structure is completely symmetric and does not require any feed network bridge (differently from differential feeding structure), making it very suitable for simultaneous transmit and receive (STAR) applications that employ balance feeding structures and, therefore, require very similar port performance. An antenna prototype has been designed for the ultrahigh-frequency (UHF) radio frequency identification (RFID) bandwidth, and the measurement has revealed excellent isolation performance, with a peak of 42 dB at the frequency of 922 MHz.

DARPA's Shared Spectrum Access for Radar and Communications (SSPARC) program seeks to improve radar and communications capabilities through spectrum sharing. Spectrum sensing is an integral component of this vision. For example, a spectrally-agile military radar system could adapt the frequency bands it uses according to the sensed spectrum. Currently, radar transmission and spectrum sensing must be multiplexed in time. That is to say, sensing the use of a particular frequency band is only possible during time slices where the radar is inactive in that band. In this paper, we describe how emerging Simultaneous Transmit and Receive (STAR) technology could be evolved to support simultaneous radar and spectrum sensing. We review the state-of-the-art in STAR technology and identify the key challenges associated with achieving contemporaneous radar operation and spectrum sensing on the same platform.

Theoretical performance of ideal multi-channel analog Self-Interference Cancellation (SIC) networks are considered for Simultaneous Transmit and Receive (STAR) phased array applications. Three different matching criteria are described for designing analog SIC networks, two of which may be implemented using a single cancellation path per element. Simulated results are presented comparing the performance of each SIC type under finite dynamic range limitations.

This research project aims to expand the capability of current US Navy Automated Test Equipment (ATE) family of testers known as the Consolidated Automated Support System (CASS). Industry research is now focused on breaking the historical construct of test equipment. Advances in the field of Synthetic Instruments have opened the door to test avionics in new ways. Every year new capabilities are developed using core hardware and increasingly capable software modules to create complex waveforms. This research creates a Digital Radio Frequency Memory (DRFM) Synthetic Instrument that can be programmed to perform a wide array of low latency Radio Frequency (RF) tests. Synthetic Instruments are defined as a concatenation of hardware and software modules used in combination to emulate a traditional piece of electronic instrumentation. This Synthetic Instrument couples high speed Analog-to-Digital Converters (ADC) to high speed Digital-to-Analog Converters (DAC) with Field Programmable Gate Arrays (FPGA) in between for digital signal processing. An RF front end is used to down convert the RF to baseband where it is sampled, modified, and up converted back to RF. The FPGA performs Digital Signal Processing (DSP) on the signal to achieve the desired output. Application of this DRFM in automated testing is demonstrated using a Reconfigurable Transportable Consolidated Automated Support System (RTCASS) tester at Naval Air Systems Command (NAVAIR) Jacksonville, FL. The Unit Under Test (UUT) is an ALQ-162 Defensive Electronic Countermeasures (DECM) receiver-transmitter. Ultra-low latency signals are generated to simulate enemy jamming stimulus. As the ALQ-162 detects and responds to the input, the DRFM switches to a new frequency. The time taken by the ALQ-162 to acquire, respond, and re-acquire is measured. This test confirms the internal Yttrium Iron Garnet (YIG) oscillator meets slew specifications. Currently Navy ATE can only test RF units using high latency steady state tests. This research project developed a supplemental unit that can be added to the VXI chassis in the CASS family of testers and conduct ultra-low latency active tests. The instrument acts as hardware-in-the-loop to perform real-time tests including a new capability to measure jamming response time from DECM avionics. Demonstrated performance capabilities include: latency <; 100 ns, output Spurious-Free Dynamic Range (SFDR) > 80 dBc, input SFDR > 60 dBc, frequency tuning resolution <; 2 Hz, and frequency settling time <; 0.5 ns. New RF capabilities developed by this effort parallel similar research ongoing for digital test instruments like the Teradyne High Speed Subsystem. Incorporating this Digital RF Memory synthetic instrument into current and future ATE will improve readiness and supportability of the fleet. Improvements demonstrated by this research project will expand the type and quantity of assets able to be tested by current and future ATE.

The Digital Radio Frequency Memory (DRFM) is a device which samples a radio signal, usually at microwave frequencies, and regenerates it after a controlled delay. It is anticipated that DRFMs will replace analogue delay lines in the next generation of Radar Test and Electronic Counter Measures (ECM) equipment. The minimum DRFM consists of: a downconverter from radio frequencies to baseband, a digital delay line, and an upconverter back to the original input frequency. The paper outlines the basic hardware configurations. For the designer of coherent or interferometric systems, the relative phase of the input and output signals is of key importance. This is particularly true for counters to Doppler and angle tracking radar systems. An investigation into the likely phase errors introduced by DRFM sampling and reconstruction is given.

Digital Radio Frequency Memory (DRFM) has been widely used for the storage of radio frequency and microwave signals. As the frequency and bandwidth are large, the implement of DRFM is limited by the speed of digital devices. A design is proposed to solve this problem based on leading technology such as poly-phase filter, Parallel-decomposition convolution and Partition of the coefficient sequence, RapidIO technology. The design shown in this paper is useful in complicate radar echo signal simulation with broadband coverage and high-speed data rate.

This paper describes the design, implementation, and testing of a novel multi-function software defined Radio Frequency (RF) system designed for small airborne drone applications. The system was created using an inexpensive Field Programmable Gate Array (FPGA) to combine a coherent linear frequency modulated radar transmitter and receiver, with a Digital Radio Frequency Memory (DRFM) jammer for use with a common RF aperture in simultaneous operation. The system was implemented on a Xilinx Kintex-7 FPGA with a wideband analogue-to-digital/ digital-to-analogue (ADC/DAC) converter mezzanine board and tested using hardware-in-the-loop mode to validate its performance. This is the first known account of an integrated multifunction electronic attack and radar system on a single chip, capable of performing a simultaneous, not time shared, operation.