Phased-array transceiver for millimeter-wave frequencies
A phased-array transmitter and receiver that may be effectively implemented on a silicon substrate. The transmitter distributes to front-ends, and the receiver combines signals from front-ends, using a power distribution/combination tree that employs both passive and active elements. By monitoring the power inputs and outputs, a digital control is able to rapidly provide phase and gain correction information to the front-ends. Such a transmitter/receiver includes a plurality of radio frequency (RF) front-ends and a power splitting/combining network that includes active and passive components configured to distribute signals to/from the front-ends.
1. A phased-array transmitter having beam-steering ability, comprising:
a plurality of radio frequency (RF) front-ends, each configured to transmit a signal with a given phase relative to the others such that the amplitude of the transmitted signal is highest in a given direction, each of the RF front-ends comprising:
a phase shifter configured to delay the signal in accordance with the given direction; and
a variable amplifier configured to adjust the gain of the signal; and
a power distribution network configured to accept an RF signal from an up-conversion element and to selectively pass the RF signal to one or more of the RF front-ends such that unselected RF front-ends do not receive the RF signal, wherein the power distribution network includes active components and passive combiners that include a cross-coupled transmission line and a decoupling resistive network.
2. The transmitter of claim 1 , wherein the RF front-ends further comprise a digital beam table configured to adjust the phase shifter's phase delay and the variable amplifier's gain.
3. The transmitter of claim 2 , wherein the RF front-ends further comprise a power sensor configured to measure each RF front-end's power output.
4. The transmitter of claim 3 , further comprising a digital control configured to determine an optimal phase delay and gain for each RF front end and to provide that information to the beam table of each RF front-end.
5. The transmitter of claim 4 , wherein the digital control is further configured to account for manufacturing and environmental variations in its determination of optimal phase delay and gain.
6. The transmitter of claim 4 , further comprising a multiplexer configured to accept the power measurements from each RF front-end's power sensor and further configured to output any individual power signal or an aggregation of all power outputs.
7. The transmitter of claim 1 , wherein the phase shifter of each RF front end is a passive phase shifter configured to provide a continuous 180 degree range of phase shift and the variable amplifier of each RF front end is a differential phase-inverting amplifier configured to provide an additional 180 degrees of discrete phase shift and variable gain amplification.
8. The transmitter of claim 1 , wherein the passive combiners in the power distribution network comprise one or more modified Gysel splitters, configured to passively split a signal and the active components in the power distribution network comprise one or more active distribution amplifiers, configured to amplify and split a signal.
9. The transmitter of claim 1 , further comprising a buffer configured to provide loopback information to an associated receiver.
10. The transmitter of claim 1 , wherein the phased-array transmitter is formed on an integrated circuit chip.
11. A method for beam-steering in a phased-array transmitter implemented on a silicon substrate, comprising the steps of:
distributing a signal to a plurality of transmitter front-ends formed on a silicon substrate, comprising selectively passing the signal to the plurality of transmitter front-ends, such that unselected front-ends do not receive the signal;
phase shifting the signal at each transmitter front-end such that the transmitter outputs interfere to produce a directed beam;
measuring the combined power output of a plurality of the transmitter front-ends; and
adjusting an amplification gain of an amplifier in each of the front-ends based on the measured power output to compensate for deviations from an optimal power output.
12. The method of claim 11 , further comprising the step of monitoring environmental conditions, wherein the step of adjusting further adjusts the amplification gain of the transmitter front-ends based on said environmental conditions.
13. The method of claim 11 , wherein said step of phase shifting directs the beam to avoid obstacles in the line of sight.