Joint transmit and receive I/Q imbalance compensation
Conventional transceivers do provide some compensation for in-phase/quadrature (I/Q) imbalance. However, these techniques do not separately compensate for I/Q imbalance for the transmitter and receiver sides of the transceiver. Here, a transceiver is provided that allows for compensation of I/Q imbalance in the transmitter and receiver irrespective of the other to allow for a more accurate transceiver.
1. An apparatus comprising:
a transmit path that is coupled to radio frequency (RF) circuitry, wherein the transmit path includes a modulation compensator that compensates for in-phase/quadrature (I/Q) mismatch in the transmit path;
a switch that is coupled to the RF circuitry;
a delay element that is coupled to the RF circuitry and that is coupled to the switch so as to actuate and deactuate the switch; and
a receive path that is coupled to switch, wherein the receive path includes a demodulation compensator that compensates for I/Q mismatch in the receive path.
2. The apparatus of claim 1 , wherein each of the receive and transmit paths further comprise an in-phase path and a quadrature path.
3. The apparatus of claim 2 , wherein the in-phase path for the transmit path further comprises:
an in-phase filter that is coupled to the modulation compensator;
an in-phase digital-to-analog converter (DAC) that is coupled to the in-phase filter;
an in-phase low pass filter (LPF) that is coupled to the in-phase DAC; and
an in-phase mixer coupled to the in-phase LPF.
4. The apparatus of claim 3 , wherein the quadrature path for the transmit path further comprises:
a quadrature filter that is coupled to the modulation compensator;
a quadrature DAC that is coupled to the quadrature filter;
a quadrature LPF that is coupled to the quadrature DAC; and
a quadrature mixer coupled to the quadrature LPF.
5. The apparatus of claim 4 , wherein the transmit path further comprises:
an adder that is coupled to the in-phase mixer and the quadrature mixer;
a local oscillator that is coupled to the in-phase mixer; and
a phase delay circuit that is coupled to the local oscillator and the quadrature mixer.
6. The apparatus of claim 2 , wherein the in-phase path for the receive path further comprises:
an in-phase mixer that is coupled to the switch;
an in-phase LPF that is coupled to the in-phase mixer; and
an in-phase analog-to-digital converter (ADC) that is coupled to the in-phase LPF and the demodulation compensator.
7. The apparatus of claim 6 , wherein the quadrature path for the receive path further comprises:
a first quadrature mixer that is coupled to the switch;
a quadrature LPF that is coupled to the first quadrature mixer;
a quadrature ADC that is coupled to the quadrature LPF; and
a second quadrature mixer that is coupled to the quadrature ADC and the demodulation compensator.
8. The apparatus of claim 7 , wherein the transmit path further comprises:
a local oscillator that is coupled to the in-phase mixer; and
a phase delay circuit that is coupled to the local oscillator and the first quadrature mixer.
9. The apparatus of claim 1 , wherein the relationship between an input signal (u(n)) and an output signal (x(n)) for the modulation compensator is:
x
(
n
)
=
u
(
n
)
-
h
m
h
d
u
*
(
n
)
-
c
h
d
,
wherein c, h m , and h d are parameters for the apparatus.
10. The apparatus of claim 1 , wherein the relationship between an input signal (y(n)) and an output signal (v(n)) for the demodulation compensator is:
v
(
n
)
=
[
y
(
n
)
-
d
]
-
g
m
g
d
*
[
y
*
(
n
)
-
d
]
,
wherein d, g m , and h d are parameters for the apparatus.
11. An apparatus comprising:
a transmit path having:
a modulation compensator that compensates for I/Q mismatch in the transmit path;
an in-phase filter that is coupled to the modulation compensator;
a quadrature filter that is coupled to the modulation compensator;
a first DAC that is coupled to the in-phase filter;
a second DAC that is coupled to the quadrature filter;
a first LPF that is coupled to the first DAC;
a second LPF that is coupled to the second DAC;
a first local oscillator;
a first mixer that is coupled to the first local oscillator and the first LPF;
a first phase delay circuit that is coupled to the first local oscillator;
a second mixer that is coupled to first phase delay circuit and the second LPF; and
an adder that is coupled to the first and second mixers;
RF circuitry that is coupled to the adder;
a switch that is coupled to the RF circuitry;
a delay element that is coupled to the RF circuitry and that is coupled to the switch so as to actuate and deactuate the switch; and
a receive path having:
a third mixer that is coupled to the switch;
a fourth mixer that is coupled to the switch;
a second local oscillator that is coupled to the third mixer;
a second phase delay circuit that is coupled to the second local oscillator and the fourth mixer;
a third LPF that is coupled to the third mixer;
a fourth LPF that is coupled to the fourth mixer;
a first analog-to-digital converter (ADC) that is coupled to the third LPF;
a second ADC that is coupled to the fourth LPF;
a fifth mixer that is coupled to the second ADC; and
a demodulation compensator is coupled to the first ADC and the fifth mixer, wherein the demodulation compensator compensates for I/Q mismatch in the receive path.
12. The apparatus of claim 11 , wherein the relationship between an input signal (u(n)) and an output signal (x(n)) for the modulation compensator is:
x
(
n
)
=
u
(
n
)
-
h
m
h
d
u
*
(
n
)
-
c
h
d
,
wherein c, h m , and h d are parameters for the apparatus.
13. The apparatus of claim 11 , wherein the relationship between an input signal (y(n)) and an output signal (v(n)) for the demodulation compensator is:
v
(
n
)
=
[
y
(
n
)
-
d
]
-
g
m
g
d
*
[
y
*
(
n
)
-
d
]
,
wherein d, g m , and h d are parameters for the apparatus.