Simultaneous spatial and frequency-domain filtering at the antenna inputs achieving up to +10dBm out-of-band/beam P_1dB

Abstract

Abstract:A 4-element LO-phase shifting phased-array system with 8-phase passive mixers terminated by baseband capacitors is realized in 65nm CMOS. The passive mixers upconvert both the spatial and frequency domain filtering to RF, realizing blocker suppression directly at the antenna input. 3rd harmonic reception is used to widen the frequency range to 0.6-3.6GHz at 68-195mW power dissipation. Up to +10dBm of P 1dB for out-of-beam/band, a 1-element NF of 3-6dB and in-beam/band IIP3=+2..+9dBm are measured. 2 TextMulti-antenna transceivers with beam-forming are recently gaining interest also for low GHz frequencies (<6GHz) [1]-[4]. In the antenna beam, (phase shifted) signals from multiple antennas add constructively, improving SNR, while out-of-beam signals add destructively (i.e. spatial filtering).Usually the summation point is behind some gain blocks, which then need to be capable of handling strong signals. To improve the input-referred compression point P 1dB , a fully passive switchedcapacitor approach was presented in [4], providing P 1dB =+2dBm, but at a high noise penalty:NF=18dB. Here we propose to sum immediately at the baseband capacitors of passive mixer-first switched-RC down-converters. We will show that this can render a direction dependent RF impedance (spatial filtering) together with RF band-pass frequency filtering at lower noise and higherThe proposed architecture is shown in Analog G m blocks consume 36mW generating 100mS at I and Q paths. Overall power when 4 elements are activated is 68-195mW for the received frequency range of 0.6-3.6GHz. The maximum ripple in the gain is 2.5dB and in-beam/band IIP3 varies from +2.. +9dBm (see Fig. 5.2.5). The first harmonic is rejected between 15-25dB. The measurement results are compared to three previously reported 4-element phased-array systems. Clearly remarkable P 1dB and NF are achieved, and the dynamic range at the antenna inputs is substantially improved compared to previous work.Acknowledgment:

3.5 A 1.0-to-2.5GHz beamforming receiver with constant-G<inf>m</inf> vector modulator consuming &#x003C; 9mW per antenna element in 65nm CMOS

“…As the inverter transconductor amplifies the RF signal first, the impedance level seen by the passive mixer can be much higher than the 50Ω antenna impedance. Therefore, compared to a mixer-first design [3,4], the mixer switches can be smaller, resulting in a large reduction in dynamic power consumption in the clocks. It's important to note that the current of the transconductor is always steered to only one of the outputs and the baseband capacitors retain their voltage when the current is routed to another path.…”

“…A receiver with programmable phase shift and high linearity is crucial to cope with interference. Switchedcapacitor vector modulators can provide adequate phase shift and linearity [3,4], but so far, at the cost of a high power consumption. As power consumption increases linearly with the number of antenna elements, it is one of the bottlenecks hindering commercialization of beamforming.…”

“…Conveniently, the element summing required for beamforming is automatically achieved by connecting the element outputs to shared capacitors [3]. The baseband bandwidth is defined by the output resistance of the transconductor (Rout), the baseband capacitance and the mixer duty cycle [5].…”

“…Figure 6 shows a comparison table with high SFDR low-GHz beamforming receivers. Only [3] achieves higher SFDR (but for 13dB lower gain), while its phase shifter resolution is low. In comparison to [2,4], the presented receiver achieves similar or better SFDR, at a significantly lower power consumption of 6.5-to-9 mW per element for 1.0-to-2.5GHz.…”

A 4-Element Phased-Array System With Simultaneous Spatial- and Frequency-Domain Filtering at the Antenna Inputs

“…We will show that this renders superior blocker handling, at the cost of some flexibility in control of the beam pattern. In [8] we presented a 4-element phased-array receiver in 65 nm CMOS technology which achieves up to +10 dBm out-of-band/beam 2 compression point and 3-6 dB single-element noise figure in a frequency range of 0.6-3.6GHz. This paper elaborates on the phased-array system and includes a comprehensive mathematical analysis of the spatial-and frequency-domain filtering at the antenna inputs and also at the baseband.…”