Distributed RF front-end for UWB receivers
View Patent ↗Described herein are ultra wide-band distributed RF (UWB-DRF) front-end receivers comprising composite cells distributed along transmission lines, where each composite cell comprises a low-noise amplifier (LNA) merged with a mixer. By merging the LNA and the mixer in each composite cell, the power consumption and chip area of the RF front-end is reduced. Further, the distributed architecture of the RF front-end allows it to operate over a wide bandwidth by absorbing the parasitic capacitances of the composite cells into the transmission lines of the RF-front end. Embodiments of the RF front-end provide wideband flat gain, low noise figure (NF), wideband linearity, and wideband matching at the inputs of the RF front-end. In an embodiment, a programmable resistance at the termination of the RF transmission line allows the RF front-end to trade off a few decibels of mismatch at the RF input for higher gain and lower NF.
1. A radio frequency (RF) front-end circuit, comprising:
an RF transmission line;
a local oscillator (LO) transmission line;
an intermediate frequency (IF) transmission line; and
a plurality of composite cells, wherein each composite cell comprises:
a low-noise amplifier (LNA); and
a mixer coupled to the LNA;
wherein the plurality of composite cells are distributed along the RF, LO and IF transmission lines.
2. The circuit of claim 1 , further comprising a variable resistance coupled to a termination of the RF transmission line.
3. The circuit of claim 2 , wherein the variable resistance comprises:
a bank of parallel resistors; and
a least one switch coupled to at least one of the resistors.
4. The circuit of claim 2 , wherein the variable resistance is programmable to any one of a plurality of resistances, and wherein one of the plurality of resistances is within a range of 75 to 150Ω.
5. The circuit of claim 4 , wherein one of the plurality of resistances is within a range of 100 to 150Ω.
6. The circuit of claim 1 , wherein each composite cell comprises an inductor coupled between the LNA and the mixer in the cell.
7. The circuit of claim 1 , wherein the RF, LO and IF transmission lines each have a characteristic impedance of approximately 50Ω.
8. The circuit of claim 1 , wherein each mixer comprises a pair of switching transistors.
9. The circuit of claim 8 , wherein each pair of switching transistors is configured to be driven by a differential local oscillator (LO) signal.
10. The circuit of claim 8 , wherein each switching transistor comprises a metal-oxide-semiconductor field-effect transistor (MOSFET).
11. The circuit of claim 8 , wherein the LNA comprises a current-mode transistor that outputs a current to the corresponding mixer based on an input RF voltage.
12. The circuit of claim 1 , wherein the RF, LO and IF transmission lines comprise on-chip inductors.
13. The circuit of claim 1 , further comprising a load coupled to a termination of the IF transmission line, wherein the IF transmission line has a characteristic impedance of approximately 50Ω and the load has an impedance of at least 100Ω.
14. The circuit of claim 13 , wherein the load has an impedance of at least 150Ω.
15. The circuit of claim 13 , wherein the load has an impedance of at least 200Ω.