1. A method for reducing the interfering effect of a radar transmitter occupying a nominal frequency bandwidth into an other operating band, where said other operating band is spaced from said nominal frequency bandwidth by a third frequency band, said method comprising the steps of:
generating at said radar transmitter a constant-amplitude pulse centered at a frequency within said nominal frequency bandwidth of said radar and having a nominal bandwidth which lies within said nominal frequency bandwidth, and which also has an actual bandwidth which extends into said other operating band;
applying phase perturbations to said constant-amplitude pulse so as to produce a phase-perturbed constant-amplitude pulse centered at said frequency within said nominal frequency bandwidth of said radar with reduced amplitude of that portion of said actual bandwidth of said constant-amplitude pulse which lies within said other operating band; and
transmitting said phase-perturbed constant-amplitude pulse toward a radar target.
2. A method for reducing interference between constant-amplitude long-range and short-range radar subpulses, where said long-range radar subpulses are centered at a first frequency and have a first nominal passband and said short-range pulses are centered at a second frequency, different from said first frequency and having a second nominal passband, the passband of at least one of said long-range and short-range radar subpulses extending at least partially into said nominal passband of the other of said long-range and short-range radar subpulses, said method comprising the steps of:
selectively applying phase perturbations to said one of said long-range and short-range radar subpulses to tend to null that portion of said passband of said one of said long-range and short-range radar subpulses which extends into said nominal passband of said other one of said long-range and short-range radar subpulses; and
transmitting at least one of the phased perturbed subpulses toward a radar target.
3. A method according to claim 2, wherein said step of selectively applying phase perturbations includes the steps of:
(a) Compute sk, the nominal pulse’s kth digital sample as:
s
k
=
cos
\u2061
(
2
\u2062
\u03c0
\u2061
(
f
0
f
s
)
\u2062
k
+
\u03b8
k
)
where:
k is a sample index ranging between 1 and N, the total number of samples in the net pulse;
f0 is the pulse’s center frequency at the input to the digital-to-analog (DA) converter;
fs is the sample rate at which the signal samples are to be read out of a digital memory (and the same rate at which the DA converter operates); and
\u03b8k is the pulse’s nominal phase modulation function;
(b) compute the phase perturbation as:
\u03c6=\u03bb\u03bbDRD+I\u22121DRs
where:
\u03c6 is an N\xd71 column vector of phase perturbation samples with kth element equal to \u03c6k;
\u03bb is a positive scalar, greater than unity, whose value determines null depth;
D is an N\xd7N diagonal matrix (all off-diagonal elements are zero) whose kth diagonal element is similar to sk with the cosine function replaced by the sine;
R is an N\xd7N matrix that determines null center frequency, width, and shape;
I is an N\xd7N identity matrix; and
s is an N\xd71 vector whose kth element is equal to sk, to thereby define a kth signal sample as
s
~
k
=
cos
\u2061
(
2
\u2062
\u03c0
\u2061
(
f
0
f
s
)
\u2062
k
+
\u03b8
k
+
\u03d5
k
)
where the tilde indicates a sample of the phase-perturbed pulse and \u03c6k is the kth sample of the phase perturbation that creates the desired spectral null.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An upright surface cleaning apparatus comprising:
(a) a floor cleaning head having a dirty air inlet;
(b) air flow passage extending from the dirty air inlet to a clean air outlet;
(c) an upright section moveably mounted to the surface cleaning head between an storage position and an in use position and comprising a filtration member and a suction motor provided in the air flow passage, the suction motor having an air inlet end, an opposed distal end and an air inlet direction; and a motor housing, the motor housing comprising a motor section in which the suction motor is provided, the motor section having a first end at the air inlet end of the suction motor and an opposed second end at the distal end of the suction motor;
(d) an openable post motor filter chamber provided in the motor housing and having an inlet end and an outlet end, at least a portion of the filter chamber is provided in the motor section, the inlet end includes a finger guard and the filter chamber has a direction of airflow that is transverse to the air inlet direction of the suction motor; and,
(e) a post motor HEPA filter removably mounted in the filter chamber.
2. The surface cleaning apparatus of claim 1 wherein the inlet end of the filter chamber is positioned adjacent the suction motor.
3. The surface cleaning apparatus of claim 1 wherein at least a portion of the inlet end of the filter chamber is laterally spaced from and faces the suction motor.
4. The surface cleaning apparatus of claim 1 further comprising a pre-motor filter positioned at the air inlet end of the suction motor.
5. The surface cleaning apparatus of claim 4 further comprising a pre-motor filter positioned at the air inlet end of the suction motor and the pre-motor filter has a direction of airflow that is aligned with the air inlet direction of the suction motor.
6. The surface cleaning apparatus of claim 5 wherein the filtration member comprises a cyclone, the cyclone comprises an air inlet and an air outlet and the air outlet of the cyclone is spaced from and faces the pre-motor filter.
7. The surface cleaning apparatus of claim 1 wherein the air inlet end of the filter chamber is spaced less than 3 inches from the suction motor.
8. The surface cleaning apparatus of claim 1 wherein the air inlet end of the filter chamber is spaced less than 1.5 inches from the suction motor.
9. An upright surface cleaning apparatus comprising:
(a) a floor cleaning head having a dirty air inlet;
(b) air flow passage extending from the dirty air inlet to a clean air outlet;
(c) an upright section moveably mounted to the surface cleaning head between an storage position and an in use position and including a motor housing;
(d) a filtration member and a suction motor provided in the air flow path, the suction motor having an air inlet end, an opposed distal end and an air inlet direction;
(e) an openable post motor filter chamber provided in the motor housing and having an inlet end and an outlet end, at least a portion of the inlet end is laterally spaced from and faces the suction motor, the inlet end including a finger guard; and,
(f) a post motor HEPA filter removably mounted in the filter chamber.
10. The surface cleaning apparatus of claim 9 wherein the inlet end of the filter chamber is positioned adjacent the suction motor.
11. The surface cleaning apparatus of claim 9 wherein the motor housing comprises a motor section in which the suction motor is provided, the motor section having a first end at the air inlet end of the suction motor and an opposed second end at the distal end of the suction motor and at least a portion of the filter chamber is provided in the motor section.
12. The surface cleaning apparatus of claim 9 further comprising a pre-motor filter positioned at the air inlet end of the suction motor.
13. The surface cleaning apparatus of claim 9 wherein the filter chamber has a direction of airflow that is transverse to the air inlet direction of the suction motor.
14. The surface cleaning apparatus of claim 13 further comprising a pre-motor filter positioned at the air inlet end of the suction motor and the pre-motor filter has a direction of airflow that is aligned with the air inlet direction of the suction motor.
15. The surface cleaning apparatus of claim 14 wherein the filtration member comprises a cyclone, the cyclone comprises an air inlet and an air outlet and the air outlet is spaced from and faces the pre-motor filter.
16. The surface cleaning apparatus of claim 9 wherein the air inlet end of the filter chamber is spaced less than 3 inches from the suction motor.
17. The surface cleaning apparatus of claim 9 wherein the air inlet end of the filter chamber is spaced less than 1.5 inches from the suction motor.