RF front-end circuitry with reduced DC offset
An RF front-end circuit includes a directional coupler, a mixer, and a reflection circuit. The directional coupler is adapted to receive an antenna signal and an oscillator signal. The mixer is coupled to the directional coupler to receive the antenna signal and is further adapted to receive a mixer signal and to generate an output signal related to the antenna signal and the mixer signal. The reflection circuit is coupled to the directional coupler to receive the oscillator signal and is adapted to reflect at least a portion of the oscillator signal to the mixer via the directional coupler to counteract a parasitic portion of the oscillator signal received at the mixer.
1. An RF front-end circuit comprising:
a directional coupler adapted to receive an antenna signal and an oscillator signal;
a mixer coupled to the directional coupler to receive the antenna signal, the mixer further adapted to receive a mixer signal and to generate an output signal related to the antenna signal and the mixer signal; and
a reflection circuit coupled to the directional coupler to receive the oscillator signal, the reflection circuit adapted to reflect at least a portion of the oscillator signal to the mixer via the directional coupler to counteract a parasitic portion of the oscillator signal received at the mixer.
2. The circuit of claim 1 , wherein the reflection circuit comprises a complex input impedance.
3. The circuit of claim 1 , wherein the reflection circuit comprises a delay line and a resistance.
4. The circuit of claim 1 , wherein the reflection circuit comprises a delay line and a power divider, an input impedance of the power divider comprising a resistance.
5. The circuit of claim 4 , wherein the power divider is adapted to provide the mixer signal.
6. The circuit of claim 1 , wherein the reflection circuit comprises a delay line comprising at least two parallel strip lines coupled by a plurality of short-circuits.
7. The circuit of claim 6 , wherein the short-circuits are destructible.
8. The circuit of claim 7 , wherein the short-circuits are laser-destructible.
9. The circuit of claim 6 , wherein the strip lines are separable at locations between adjacent short-circuits.
10. The circuit of claim 9 , wherein the strip lines are laser-separable.
11. The circuit of claim 1 , wherein the output signal is one of a baseband signal and an intermediate frequency (IF) signal.
12. The circuit of claim 1 , wherein the reflection circuit is adapted to reduce a DC signal offset in the output signal by counteracting the parasitic portion of the oscillator signal received at the mixer.
13. An RF front-end circuit comprising:
a mixer comprising:
a first input adapted to receive an antenna signal;
a second input adapted to receive a mixer signal; and
an output adapted to provide an intermediate frequency signal;
a directional coupler comprising:
a first RF port adapted to be coupled to an antenna;
a second RF port coupled to the first input of the mixer and adapted to receive the antenna signal;
a first oscillator port adapted to receive an oscillator signal;
a second oscillator port coupled to the first oscillator port and adapted to receive the oscillator signal; and
a reflection circuit comprising an input coupled to the second oscillator port, the reflection circuit comprising a complex input impedance having a value such that a portion of the oscillator signal is reflected at the reflection circuit input to the second oscillator port of the directional coupler to superimpose with a parasitic portion of the oscillator signal between the first oscillator port and the second RF port and reduce a DC offset signal at the output of the mixer.
14. The circuit of claim 13 , wherein the reflection circuit comprises a delay line and an ohmic resistance.
15. The circuit of claim 13 , wherein the reflection circuit comprises a delay line and a power divider.
16. The circuit of claim 15 , wherein the power divider is coupled to the mixer and is adapted to provide the mixer signal.
17. The circuit of claim 13 , wherein the reflection circuit comprises a delay line comprising at least two parallel strip lines coupled by a plurality of short-circuits.
18. The circuit of claim 17 , wherein the short-circuits are separable.
19. The circuit of claim 18 , wherein the short-circuits are laser-separable.
20. The circuit of claim 17 , wherein the strip lines are separable at locations between adjacent short-circuits.
21. The circuit of claim 20 , wherein the strip lines are laser-separable.
22. The circuit of claim 13 , wherein the reflection circuit comprises electronically adjustable components adapted to selectively adjust an input impedance of the reflection circuit to compensate for the parasitic portion of the oscillator signal.
23. A radar system comprising:
RF front-end circuitry comprising:
a directional coupler adapted to receive an antenna signal and an oscillator signal;
a mixer coupled to the directional coupler to receive the antenna signal, the mixer further adapted to receive a mixer signal and to output a baseband signal related to the antenna signal and the mixer signal;
a reflection circuit coupled to the directional coupler to receive the oscillator signal, the reflection circuit adapted to reflect at least a portion of the oscillator signal to the mixer via the directional coupler to counteract a parasitic portion of the oscillator signal received at the mixer and reduce a DC signal offset at an output of the mixer; and
an antenna integrated with the RF front-end circuitry on a single chip.
24. The radar system of claim 23 , wherein the directional coupler comprises a plurality of microstrip lines.