From 1364d4652c65fe697fd78b10540cb080efaaf93c Mon Sep 17 00:00:00 2001
From: wierenga <sdos@astron.nl>
Date: Thu, 16 Nov 2006 13:52:00 +0000
Subject: [PATCH] BugID: 973 Taking the conjugate of the beamformer weight
before sending it to the hardware was missing. This is needed because:
//
// conjugate weights to get the correct matrix
// weight a_r + i . a_i
//
// (a_r + i . a_i) . (x_r + i . x_i) = ( a_r . x_r - a_i . x_i ) + i ( a_i . x_r + a_r . x_i )
//
// This is equal to:
//
// ( x_out_r ) ( a_r -a_i ) ( x_in_r )
// ( ) = ( ) * ( )
// ( x_out_i ) ( a_i a_r ) ( x_in_i )
//
// and the same for y
//
// To send to correct weights to the beamformer we must therefore
// take the conjugate of the weight (a_r, a_i) to produce (a_r, -a_i)
// for the x_our_r component and take the conjugate AND multiply by i
// the weight (a_r, a_i) to produce (a_i, a_r).
//
---
MAC/APL/PIC/RSPDriver/src/BWWrite.cc | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/MAC/APL/PIC/RSPDriver/src/BWWrite.cc b/MAC/APL/PIC/RSPDriver/src/BWWrite.cc
index f8cfa60777e..57d3b8e3a6f 100644
--- a/MAC/APL/PIC/RSPDriver/src/BWWrite.cc
+++ b/MAC/APL/PIC/RSPDriver/src/BWWrite.cc
@@ -157,7 +157,27 @@ void BWWrite::sendrequest()
m_remaining -= size;
m_offset += size;
- //int xc_gain = GET_CONFIG("RSPDriver.XC_GAIN", i);
+ //
+ // conjugate weights to get the correct matrix
+
+ // weight a_r + i . a_i
+ //
+ // (a_r + i . a_i) . (x_r + i . x_i) = ( a_r . x_r - a_i . x_i ) + i ( a_i . x_r + a_r . x_i )
+ //
+ // This is equal to:
+ //
+ // ( x_out_r ) ( a_r -a_i ) ( x_in_r )
+ // ( ) = ( ) * ( )
+ // ( x_out_i ) ( a_i a_r ) ( x_in_i )
+ //
+ // and the same for y
+ //
+ // To send to correct weights to the beamformer we must therefore
+ // take the conjugate of the weight (a_r, a_i) to produce (a_r, -a_i)
+ // for the x_our_r component and take the conjugate AND multiply by i
+ // the weight (a_r, a_i) to produce (a_i, a_r).
+ //
+ weights = conj(weights);
switch (m_regid)
{
@@ -173,6 +193,7 @@ void BWWrite::sendrequest()
case MEPHeader::BF_XIOUT:
{
+ // multiply by i to get correct weights
// weights for x-imaginary part
weights *= complex<int16>(0,1);
@@ -193,6 +214,7 @@ void BWWrite::sendrequest()
case MEPHeader::BF_YIOUT:
{
+ // multiply by i to get correct weights
// weights for y-imaginary part
weights *= complex<int16>(0,1);
--
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