1. A method (100) for synchronizing time alignment in a multi-channel radio
5 frequency receiving system, the method comprising:
 injecting (101) an amplitude modulated or phase modulated reference signal
into each channel in the multi-channel receiver at a location associated with
each antenna input.
 detecting (102) a position of the reference signal within a time sample
10 window for each channel after analog to digital conversion;
 determining (103) propagation time difference and digital synchronization
error between each channel within the receiver electronics;
 determining (104) adjustment parameters, for synchronizing time
alignment, for each channel;
15  adjusting (105) the channels in the time domain in accordance with the
determined adjustment parameters of synchronization for each channel.
2. The method (100) according to claim 1, wherein the channels are adjusted in the
time domain by at least one of:
20  a coarse delay shift in the order of an integer number of analog-to-digital
conversion, ADC, samples; and
 a fine delay shift in the order of a fractional of ADC samples in accordance
with the determined parameters for synchronization for each channel.
25 3. The method (100) according to claim 1, wherein the reference signal is a saw tooth
signal.
4. The method (100) according to claim 3, wherein the saw tooth signal has a rise and
fall time in the order of 1µs.
30
5. The method (100) according to any preceding claims, wherein adjusting (105) the
channels comprise using an interpolation filter.

15
6. The method (100) according to claim 5, wherein the interpolation filter operate
steps of up-sampling, sample delay, and down-sampling in an interpolation module.
7. The method (100) according to any of claims 1 to 6, wherein adjusting (105) the
5 channels comprise at least one of using a shift register, and controlling a clock
generation circuit of the ADC to adjust the phase of the outgoing signal.
8. The method (100) according to any preceding claims, wherein the synchronization
is performed at startup of the system.
10
9. The method (100) according to any preceding claims, wherein the synchronization
is checked at pre-set intervals during operation of the system.
10. The method (100) according to any of the preceding claims, wherein the step of
15 determining (103) propagation time difference and digital synchronization error
comprises:
for each channel, determining (103a) an actual sample distribution around
a reference point in a pre-determined sample area in each of said time sample windows;
setting (103b) a desired sample distribution having evenly distributed
20 samples around said reference point;
determining (103c) a difference between each desired sample distribution
and each actual sample distribution for each channel;
comparing (103d) the difference between the channels.