Digital communications using self-phased arrays

Abstract

Ab3tmct-A new technique for full duplex digital communications using adaptive phase conjugation is presented. The technique is based on mixing the RF signal to an intermediate frequency where it can be easily processed, and filtering the phase of the IF signal to separate the geometry phase and the message phase. A 6 GHz microstrip retrodirective antenna array w a s built, together with the signal IF processing needed for full duplex operation. The measured RCS values of a circular array are much flatter and are 0 to -5 dB up to f80°. Two way digital communications at a baud rate of 78 KBits/sec was also demonstrated with BER < for SNRs around 10 dB. The application areas are in highperformance digital mobile telecommunications for commercial and military applications.Kevwods-Phase Conjugation, phase filtering, adaptive beam forming, digital communications.

SATCOM Retrodirective Array

“…Triple mode PLL [5] I/Q phase conjugator [6] Recent Phase conjugating mixers [7] Phase detection and phase shifting [8] DSP [9] possible with lower gain elements [14] , or conversely, smaller numbers of higher gain elements could be used at the expense of steering coverage. …”

A PHEMT-Based Phase Conjugator for Full-Duplex Retrodirective Arrays

“…The received information is previously removed in order to recover a direction of arrival bearing carrier [2], [3], or the new data is inserted using a mutually-exclusive modulating format [4]. The architectures in [2] and [3] offer a high performance, although they require dedicated circuitry.…”

“…The received information is previously removed in order to recover a direction of arrival bearing carrier [2], [3], or the new data is inserted using a mutually-exclusive modulating format [4]. The architectures in [2] and [3] offer a high performance, although they require dedicated circuitry. On the other hand, the approach in [4] simultaneous remodulation of the phase conjugated component and amplification of the received signal is presented, allowing two-mode operation for its use in full-duplex retrodirective arrays: mode I, retransmission of a BPSK signal after reception of an amplitude modulated interrogation, or mode II, ASK response when the incoming excitation is angularly modulated.…”

“…A notation as in [6] has been followed ( , with the interrogating frequency and the response. In (1) and (2), shown at the bottom of the next page, and denote the equivalent resistance of the input generator and the output load, and the phasor and frequency of the interrogating signal, while and represent the nth order Fourier coefficients of the periodic transconductance and output conductance waveforms. Note that the gate to source capacitance, , has been considered to be linear.…”

Mirror Image Sawtooth Phase Conjugator Circuit for Retrodirective Antenna Applications

“…These mixers have the disadvantage of high conversion losses since the intrinsic mixing process still uses an LO harmonic of at least twice the RF frequency. Other more complex solutions have been produced using two mixers which down convert to a lower IF frequency and then up convert the phase conjugated signal for retransmission [5], [6]. These solutions are capable of operating using an LO within the RF frequency range, however, they produce unwanted mixing products which require filtering.…”