Although there is much active research on software-defined radios (SDRs) with receive (RX) or transmit (TX) functionality, little work has been done on SDR transceivers supporting frequency division duplex (FDD). In this paper, we present a new circuit concept in which a distributed TX circuit cancels the transmitted signal at a reverse RX port through destructive interference while adding signal constructively at a forward TX port. We pair the distributed transmitter with a receiver-tracking PA degeneration technique to suppress the injected noise from TX circuits in the RX band. The system does not require off-chip filters or circulators, but still achieves both SDR flexibility and both FDD and time division duplex function. Measurements from the transceiver implemented in 65-nm CMOS show a frequency tuning range of 0.3-1.6 GHz with TX-RX isolation >23 dB and transmitted power up to 19 dBm.

Software defined radios (SDR) capable of supporting a wide range of legacy and future systems must be compatible with frequency division duplex (FDD) operation. We have recently demonstrated an FDD capable, integrated SDR (SD-FDD) that achieves >25dB isolation of TX and RX across a wide band while supporting high TX power. This transceiver employs an artificial transmission line and frequency selective TX degeneration to meet the various requirements of FDD-SDR. In this paper, this architecture is analyzed and methods to choose and calibrate the complex input weights of the transmitter are derived. The key degeneration parameters are characterized and how they affect noise is described.

An ideal Software Defined Radio (SDR) requires a reconfigurable, intergrated, widely-frequency-tunable transceiver able to support different RX/TX duplex schemes. Here we present an integrated transceiver capable of supporting both TDD and FDD operation with >25dB integrated RX-TX isolation from 0.3-1.6GHz without any off-chip switches or filters. The transceiver uses an artificial transmission line (TL) and distributed PA to separate TX and RX. TX noise in the RX band is further suppressed by >13dB an RX-tracking PA degeneration circuit.

Recent advances in reconfigurable RF front end circuits, such as passive mixer first receivers have opened the door to the possibility of building radios that can be programmed to both transmit and receive across octaves of frequency while maintaining reasonable performance and extremely high levels of integration. One of the remaining challenges in software defined radio hardware is the construction of a flexible RF system capable of duplex operation. Specifically, transmitting and receiving on the same antenna across a wide band of frequencies presents a significant challenge. This paper presents some of the primary challenges that arise in this space, as well as some interesting published and potential solutions.

A fully integrated wideband active duplexing transceiver with baseband noise-cancelling duplexing LNAs is presented. The circuit allows in-band full duplex operation with concurrent reception and transmission in the same band or closely-spaced channels. A passive mixer-first architecture is applied here, sharing a single passive mixer to perform simultaneous up-conversion and down-conversion. The bi-directional transparency of the passive mixer allows the duplexing function to be implemented at baseband instead of RF front end. Under the same condition as required for noise cancellation, the baseband duplexing LNAs buffer the transmitter input signals to the mixer while canceling those signals in receive path. Measurements from the transceiver implemented in 65 nm CMOS show a frequency tuning range of 0.1-1.5 GHz with S-11 < -20 dB, NF as low as 5.5 dB and transmitted power up to -7.1 dBm. A 30 dB linear isolation between receive and transmit is generally maintained across both LO frequency and in-band transmit/receive frequency separation. Significant suppression of transmit-induced noise and nonlinear intermodulation between received and transmitted signals are also achieved.

Recent developments in CMOS passive mixers have demonstrated a number of new and useful capabilities, including dynamic RF port impedance control and filter up-conversion, while also allowing low noise figure and high out-of-band linearity, all of which track wide-ranging LO frequencies and tunable baseband bandwidth. However, these circuits also bring a unique set of challenges and requirements. Here we extend a previously derived LTI model for such mixers to the general N-phase case, and discuss basic limits in performance specifications including impedance matching, noise figure and linearity. We then extend this analysis to include high-frequency effects, especially as they relate to transistor properties. We show that essentially all of the key specification of such mixers can be described in terms of an impedance ratio, a characteristic cut-off frequency, the number of phases of the mixer and some process-related parameters. Finally, we discuss how these properties relate to power consumption of LO circuitry.

Many MOSFET models have discontinuities in the 2nd derivative of their drain current with respect to their drain-source voltage. Because these discontinuities occur at V ds = 0V, they have little effect on simulations of active circuits, but matter when simulating transistors in deep triode, such as CMOS passive mixers. These discontinuities result in qualitatively incorrect simulations of the effects of third order nonlinearity, with the 3rd harmonic behaving proportional to the square of the input signal amplitude, A 2 , instead of A 3 . In this paper, we present a schematic-level modeling technique that can be easily implemented over any model that fails the Gummel Symmetry Test (e.g. BSIM4) without altering underlying physical equations. We then show how the model performs with respect to IM3 simulations ensuring correct magnitude and slope by comparing our model to measurements from an 8-phase passive mixer manufactured in a deep sub-micron process.

We present a widely tunable passive mixer first duplexing transceiver which employs baseband noise-canceling, duplexing LNAs. The LNAs buffer transmitted signals to the mixer while canceling those signals in receive path. The transmitted signals are up-converted by the same mixer used for receiver down-conversion. The transceiver operates over a frequency range of 0.1-1.5GHz with -18dBm transmitted power. A 33dB linear isolation between receive and transmit (separated by 135kHz) as well as suppression of transmit-induced noise and nonlinearity are achieved.

A baseband technique is presented to detect and suppress LO leakage in wideband passive mixer-first receivers. Using a variable shunting resistance on the RF port, the LO leakage signal is modulated, down-converted and detected from baseband outputs. Current DACs injecting to the baseband port are up-converted and can be adjusted to cancel LO leakage. Suppression of LO on the RF port <; -80dBm is shown with a fully automated algorithm without the aid of RF spectrum monitoring.

The need for a certain type of radar training jammer designed based m-sequence superimposed DDS source.The signal source using the FPGA m pseudo-random sequence of signals and AD9850 DDS signal is superimposed to generate complex noise signal,then this signal is applied to the the microwave oscillator source module,through the power amplifier,and finally the interference signal through an antenna radiated out,so as to achieve the requirements of real analog noise FM jamming.The tests show that the interference of the noise source with a rich spectrum,bandwidth and amplitude adjustable mounting radar.Alpha

In this work we present an architecture for a low power SDR which draws on techniques from both narrowband low power radios and recent work in SDRs. The receiver consists of a wide tuning-range passive mixer, driven with resonant non-overlapping LO drive combined with a noise-power optimized multi-path baseband amplifier. LO generation circuitry drives the mixer with an 8-phase, 12.5% duty cycle LO, but does so directly from complementary LC-tank VCOs in order to resonate out the gate capacitance of the mixer. A capacitor sharing technique on the baseband side of the mixer doubles the RX frequency range of the 8-phase clock at no added cost in power or performance, while achieving a NF as low as 7 dB. The 1.8 mW low noise baseband amplifier reuses the bias current of its four input channels while rejecting the 3rd/5th harmonics by >34 dB. The receiver consumes 10–12 mW (including VCOs, pulse generation and baseband) over a frequency range of 0.7–3.2 GHz with a 1.3 V supply.

We propose a full-duplex radio-over-fiber (ROF) system transmitting 2.5 Gb/s differential phase-shift keying (DPSK) signals with 40GHz optical millimeter-wave as downlink. Meanwhile it can be reused central wavelength as uplink connection for transmitting 2.5 Gb/s on-off keying (OOK) signals. The experimental and simulation results show that the downstream 2.5Gb/s DPSK data and the upstream 2.5Gb/s OOK data can transmit 40km single-mode fiber successfully.